Planet Debian

Matthew Garrett: Epic's EAC2 v2 seems fairly easily bypassable

Thu, 15 Oct 2026 20:23:59 +0000

Epic just announced the upcoming version 2 of their Linux implementation of Easy Anti-Cheat. It’s based on using the Linux eBPF security module to monitor what’s happening, and then a bunch of extra infrastructure to make sure this can’t be bypassed. The core part of this is requiring secure boot be enabled (ensuring that modified kernels can’t be used), using measured boot to verify that secure boot is enabled and which keys are used (to prevent you from just signing your own modified kernel), and then doing remote attestation, a mechanism where the TPM generates a signed copy of the boot measurements and passes that off to a server which verifies it came from a real TPM, verifies that you have secure boot enabled and are using the right keys, and presumably then allows you into the game.

This is all fine as long as you can prove that the measurements provided are real, and that’s actually a lot harder than you might think. First, we can simply make up our own quote signed with our own key and say that it came from a TPM. This is avoided by every TPM having an Endorsement Key (or EK) and an associated certificate, with that certificate being signed by the TPM vendor. If you have a list of all the legitimate TPM vendors and their CA keys, you can verify that the measurements came from a real TPM. Easy enough. So we need to get the measurements from a real TPM, and the one on our motherboard contains the measurements that were generated by the firmware and bootloader, and we can’t reset those at runtime without resetting the TPM, which… oh huh there’s actually nothing stopping us from doing that at runtime, as long as we have access to the hardware. Many desktop boards have the TPM on a small plugin module with a standard pinout that includes a reset pin. Simply short that to ground briefly and the TPM is back in its initial state, and userland can write whatever measurements it wants to it. Boot a modified kernel which lies to the eBPF code? As long as you replay the expected log values from a boot with secure boot on and a trusted kernel, the TPM will still happily provide a legitimate set of measurements that’ll satisfy the checker.

What if the TPM is less accessible, either because it’s mounted directly to the motherboard or it’s inside the CPU or chipset? That’s going to be trickier. But here’s the thing. The quote needs to come from a TPM, but not necessarily the TPM on your motherboard. TPMs these days are usually connected via the Serial Peripheral Interface, usually referred to as SPI. Microchip make a USB to SPI bridge, and there’s a Linux driver. Wire one of those up with an appropriate header and you can plug in an easily available TPM module intended for plugging into a motherboard, and now we tell the kernel to ignore the motherboard TPM and make /dev/tpmrm0 point at the USB one and program it with a set of trusted measurements and once again everything is going to look just fine (yes obviously the eBPF code can look for this, but we’re running a modified kernel so we can just lie to the eBPF code).

Remote attestation on PCs just doesn’t work that well in environments where you can’t associate a specific TPM with a specific system, which is basically everywhere except enterprises. But maybe that doesn’t matter and cheaters wouldn’t be willing to spend the $20 or so it’d take to produce one of these things? That would seem somewhat surprising, but it’s not impossible. And obviously any server-side cheat detection that triggers could then block that specific TPM, meaning they’d need to go and get another TPM, and maybe that ends up being enough to discourage people from bothering. From a practical level, this may be sufficient. But at a technical level? It’s not great.

Steinar H. Gunderson: Decompilation patterns, part 12: __builtin_memcpy

Thu, 15 Oct 2026 19:45:26 +0000

Say you see this lovely chunk of decompiled code:

    var_v1 = &sp10
    var_v0 = D_80010040;
    temp_s4 = var_v1;
    sp110 = &sp2C
    sp114 = &sp30
    do {
        var_v1->unk0 = (s32) var_v0->unk0;
        var_v1->unk4 = (s32) var_v0[1];
        var_v1->unk8 = (s32) var_v0[2];
        var_v1->unkC = (s32) var_v0[3];
        var_v0 += 0x10;
        var_v1 += 0x10;
    } while (var_v0 != &D_8001040[0x3C]);
    var_v1->unk0 = (s32) var_v0->unk0;
    var_v1->unk4 = (s32) var_v0[1];
    var_v1->unk8 = (s32) var_v0[2];

If you ignore the fact that m2c wrote ->unk0 for [0] (it has a bit of an annoying habit to do that), this is obviously something copying 16 bytes at a time and then 12 more bytes at the end. But would a programmer ever do this? Nope, this is an inlined, unrolled memcpy.

This is known in GCC as __builtin_memcpy, and it can happen either implicitly, or by some sort of lowering from a struct or array copy (e.g., through initialization of a stack array). Depending a bit on whether the variable is known to be aligned or not, you'll either get just lw or some evil lwr/lwl sequence; I'm always struggling a bit to change one to the other. In any case, what you want here is:

    __builtin_memcpy(&sp10, D_80010040, 0x4C);

and then make sp10 the right type instead of a scalar, ideally so that you can use sizeof() on it. Or, in some cases, a direct initialization:

    s32 foo[] = { 1, 2, 3, ...more data from D_80010040... };

Steinar H. Gunderson: Decompilation patterns, part 11: Irregular switch

Wed, 14 Oct 2026 20:35:00 +0000

Here's one that m2c usually gets right itself, but sometimes cannot:

    if (var_v1_7 != 1) {
        if (var_v1_7 < 2) { 
            if (var_v1_7 != 0) {
                spF0 = 40; 
            } else {
                vram_x = cmt46->vram_x;
                vram_y = cmt46->vram_y;
                spF0 = 40;
            }
        } else if (var_v1_7 != 2) {
            if (var_v1_7 != 3) {

Repeated comparisons against the same variable, especially in a nested form that could be binary search, should remind you of one thing: A switch. Usually, the compiler implements a switch with a jump table, but not always; if there are few conditions, or the range is too large for a reasonably-sized table, it will do some ifs instead (or, enough ifs to get within the range of a table). So what you want here is more like:

    switch (var_v1_7) {
    case 0:
       vram_x = cmt46->vram_x;
       vram_y = cmt46->vram_y;
       spF0 = 40;
       break;
    case 1:
       spF0 = 40;
       break;
    case 2:
       ...
    }

Remember that sometimes, you may need to insert cases that are not explicitly mentioned in the ifs (and/or a default case) to get everything to match back properly.

Dirk Eddelbuettel: qlcal 0.1.4 on CRAN: Fresh Upstream Updates

Wed, 14 Oct 2026 19:51:00 +0000

The twenty-second release of the qlcal package arrivied at CRAN yesterday, and has been built for r2u as well as on r-universe.

qlcal delivers the calendaring parts of QuantLib. It is provided (for the R package) as a set of included files, so the package is self-contained and does not depend on an external QuantLib library (which can be demanding to build). qlcal covers over seventy country / market calendars and can compute holiday lists, its complement (i.e. business day lists) and much more. Examples are in the README at the repository, the package page, and course at the CRAN package page.

This release is based on the changes in the QuantLib 1.44 release also made yesterday. It includes two new calendars for Malaysia and the Philippines, updates to around a dozen calendars, and a few other updates to internal files. Maxmilian Muecke spotted and fixed a few small bugs just as he did for the RQuantLib release we made yesterday; this is equally appreciated! The full details from NEWS.Rd follow.

Changes in version 0.1.4 (2026-10-13)

Add missing market calendars for Poland, Russia, Romania, Indonesia (Maximilian Muecke in #21)

Add (semi-deprecated) alternate separators '::' for Israel and New Zealand markets (Maximilian Muecke in #22)

Fix several typos across source, configuration and documentation files (Maximilian Muecke in #23)

Synchronize with QuantLib 1.44, add two new calendars, update several others, and update general utility files (Dirk in #24)

Courtesy of my CRANberries, there is a diffstat report for this release. See the project page and package documentation for more details, and more examples.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can sponsor me at GitHub.

Reproducible Builds: Reproducible Builds in September 2026

Wed, 14 Oct 2026 18:34:14 +0000

Welcome to the September 2026 report from the Reproducible Builds project!

In our reports, we try to outline the most important things that we have been up to over the past month. As a quick recap about what problem our project intends to solve, whilst anyone may inspect the source code of free software for malicious flaws, almost all software is distributed to end users as pre-compiled binaries. The motivation behind the reproducible builds effort is to ensure no flaws have been introduced during this compilation process by promising identical results are always generated from a given source, thus allowing multiple third-parties to come to a consensus on whether a build was compromised or not.

As ever, if you are interested in contributing to the project, please visit our Contribute page on our website.

In this month’s report, we cover:

Reproducible Builds Summit 2026 held in Gothenburg, Sweden

The annual Reproducible Builds summit took place from 22 to 24 September 2026 in Gothenburg, Sweden. The event brought together developers, distribution maintainers, security researchers and free software advocates from across the ecosystem to share updates on current initiatives, address outstanding toolchain bottlenecks and strengthen cross-project collaboration.

Participants engaged in a series of working sessions and technical roundtables focused on expanding the practical scope of reproducibility. Discussions covered ongoing work within major Linux distributions, language-specific package ecosystems and the various parts of the binary verification infrastructure.

Strategic planning formed a pillar of the gathering, with participants discussing long-term roadmap goals for supply-chain security, software integrity and related topics. Attendees explored new methods for automated verification, discussing how to lower the adoption barriers for maintainers and streamline the integration of deterministic build pipelines into established continuous integration (CI) systems. The event was then followed by two days of unmoderated hacking sessions. These hacking sessions provided space for technical progress, allowing attendees to draft specification updates, prototype new tool features and resolve standing reproducibility bugs in-person.

Dettrace expanding architecture support for PGO & Lisp dumps

Bernhard M. Wiedemann announced major updates to dettrace, porting the tool across most architectures supported by Debian and openSUSE. The release addresses key stability issues, passing test suites across these targets and making it ready for production build pipelines.

These improvements enable deterministic builds when utilising Profile-Guided Optimisations (PGO), removing the need to sacrifice runtime performance for reproducibility. Additionally, dettrace can now be applied to (notoriously difficult-to-reproduce) Lisp and Scheme memory dumps, including environments such as CLISP, SBCL, Scheme 48, Racket and GNU Emacs.

“They don’t care about this”

Annika Wilde, Marco Gutfleisch, Felix Reichmann, Anirban Chakraborty, Yuval Yarom, M. Angela Sasse and Ghassan Karame published a paper this month entitled “They don’t care about this”: A Systematic Study of Trusted Execution Environments Build Reproducibility in the Wild:

Trusted Execution Environments (TEEs) have become a cornerstone of modern cloud computing, providing strong confidentiality and integrity guarantees for both code and data. A critical component of this trust model is remote attestation, which enables external entities to verify the authenticity and integrity of code executing within a TEE through cryptographic measurements. However, the effectiveness of remote attestation fundamentally depends on the verifier’s ability to trace the reported measurement back to the original source code - a property that can only be guaranteed through reproducible builds. […]

The full PDF can be read online.

`SOURCE_DATE_EPOCH` specification updates

Bernhard M. Wiedemann shared a number of proposals regarding updating the SOURCE_DATE_EPOCH specification following discussions at a project summit. Seven distinct proposed changes have been submitted as merge requests on Salsa.

Bernhard’s proposed modifications are independent of one another, allowing for any combination to be merged depending on community feedback. Bernhard noted that one proposal may see the most debate, and could still benefit from further refinement before reaching consensus. Community members are invited to review and provide feedback on the individual merge requests by 1 December 2026. Input can be submitted via reactions or comments on Salsa, directly by email to Bernhard or the mailing list.

The specification was first published in 2015 and updated in 2017.

Reproducible Builds at SeaGL 2026

Reproducible Builds will be present at SeaGL in Seattle, WA, on October 23rd & 24th. Come chat with us in person!

Founded in 2013, SeaGL is a free, grassroots technical summit dedicated to spreading awareness and knowledge about free source software, hardware and culture.

New Code of Conduct (CoC) for the Reproducible Builds project

Mattia Rizzolo announced the official launch of a Code of Conduct for the Reproducible Builds project. This follows work and community discussions originally initiated in 2024, incorporating feedback gathered over email and during project summits, as well as with input from the Software Freedom Conservancy.

The new Code of Conduct establishes guidelines emphasising mutual respect among project contributors. It also defines a formalised process for submitting and handling complaints regarding community misconduct, ensuring transparent governance across project spaces. Along with the core policy document, an accompanying Code of Conduct FAQ has been published to outline the rationale behind adopting the guidelines.

Supporter Spotlight: Jochen Sprickerhof

As a reminder, another supporter spotlight interview was published featuring long-time Debian and Reproducible Builds contributor Jochen Sprickerhof, highlighting his work on package verification and project infrastructure.

Mailing list news

On our mailing list this month:

Jonathan Starr from the Institute of Open Science Practices (IOSP) posted with an announcement of its upcoming 2026 workshop series in Leiden in the Netherlands. This free-to-attend event aims to build a participant-owned data storage consortium, allowing community members to publish datasets, code and knowledge objects alongside algorithms designed to evaluate trust and value. The event features a dedicated Community Track for talks and discussions, a tool showcase and an opening session on resilient data storage.
Following up on IRC discussions regarding profile-guided optimization (PGO) on build servers, kpcyrd created a demonstration repository showing how PGO profiling can introduce non-determinism into output binaries. The demo highlights how runtime randomness (specifically, the randomised keys used in HashMaps to prevent denial-of-service attacks) causes varying bucket collision rates during test runs. These structural variances alter execution weights on underlying code branches, prompting the compiler to generate differing final assembly output for builds that would otherwise be perfectly reproducible if PGO was disabled. Rather than abandoning PGO performance gains, kpcyrd suggested treating generated profiling data as a documented build input or recorded environment artifact (similar to .buildinfo files), rather than regenerating profiles dynamically on the fly during build execution.
An autonomous AI agent (!), posted a controlled build result and reproducer demonstrating that pre-creating an obj directory in libmilter source trees prevents kernel-release path leaks (obj.Linux.<release>.x86_64) into debugging symbols. kpcyrd followed up with a helpful reply.
Alexander Sosedkin inquired on the mailing list about the preferred approach for sourcing pinned translation files to create reproducible GnuTLS release tarballs, asking whether external hosting should provide versioned downloads, or if projects ought to use Git submodules, dedicated side-repositories or some other mechanism.

Tool and documentation development

diffoscope is our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues. This month, Chris Lamb made a number of changes, including preparing and uploading versions 330, 331 and 332 to Debian. In particular, Chris committed support for radare2 versions greater than 5.9.0 […] based on input from Guillaume Girol […], and committed support for .nar files via Guix. […][…].

Chris later modified diffoscope to not Build-Depend on the Debian package of GNU Guix, as its status in the Debian bug tracking system would transitively render diffoscope as being overly buggy for the next stable release […]. Similarly, he adjusted the Build-Depends on the apksigcopier package as it has been removed from Debian testing […] and, finally, he updated a number of copyright years […][…].

Vagrant Cascadian updated diffoscope in GNU Guix to version 332.

reprotest is our tool for building the same source code twice in different environments and then checking the binaries produced by each build for any differences. This month, reprotest version 0.7.33 was uploaded to Debian by Holger Levsen with the following changes:

Sergei Tachenov fixed the fileordering test on all filesystems, including the likes of ZFS, which could return a different order across two builds due to build being done in a different directory […].
Holger Levsen bumped the Standards-Version to 4.7.4, reflected that Priority: optional is the default now […], fixed the old Free Software Foundation address […] and bumped the debhelper ‘compat’ level to 14 after confirming there are only desired changes […].
Vagrant Cascadian updated *reprotest* to version 0.7.33 in GNU Guix.

rebuilderd, our server designed monitor the official package repositories of Linux distributions and attempt to reproduce the observed results there; it powers, amongst other things, reproduce.debian.net. This month, Bernhard M. Wiedemann submitted a pull request to rebuilderd that refactors RPM repository metadata handling. The change extracts rpm-md parsing out of the Fedora-specific scheduler module and into a shared one.

Lastly, there were a number of improvements made to our website this month as well. For example:

Chris Lamb:
- Added a note re. TZ=UTC vs. TZ=UTC0 to the Timezones page. […][…][…]
- Make a bunch of cosmetic updates to Jochen’s supporter spotlight. […]
Holger Levsen made a very large number of changes to the Gothenburg summit page. […][…][…][…][…][…]
Jochen Sprickerhof wrote and published another supporter spotlight. […][…][…][…][…]
Mattia Rizzolo:
- Made a number of changes to the Gothenburg summit page. […][…][…][…][…]
- Add and publish the new Code of Conduct. […][…][…]
- Update translation POs. […]
kpcyrd also made a number of changes to the Gothenburg summit page. […][…][…][…]

Patches

The Reproducible Builds project detects, dissects and attempts to fix as many currently-unreproducible packages as possible. We endeavour to send all of our patches upstream where applicable or possible. This month, we wrote a large number of such patches, including:

Bernhard M. Wiedemann:
Chris Lamb:
- #1146687 filed against lektor.
- #1147673 filed against golang-forgejo-xorm-xorm.
- #1147674 filed against python-vermin.
- #1148657 filed against python-eventlet.
- #1148658 filed against golang-github-miekg-pkcs11.
- #1148660 filed against python-prov.
- #1148973 filed against lemonade.
- #1148977 filed against yuzu.
- #1148979 filed against python-mne.
Jochen Sprickerhof:
- #1147645 filed against bitshuffle.
Tianyu Chen:
- #1147760 filed against nss.
Klemen Ferjancic:
- Debian:
- Upstream:
Vagrant Cascadian:
- libecoli […]
- cdebootstrap […]

Vagrant Cascadian also performed a number of Non-Maintainer Uploads (NMUs) and Quality Assurance (QA) uploads in Debian for several packages with outstanding reproducibility issues. These included molttemplate, buddy, xfonts-nexus, fte and lifelines.

At the time of this writing, that leaves 130 submitted patches, with only 61 outstanding submitted patches that older than a year in the Debian bug tracking system. This number is only 26 if we exclude any low-priority build path issues.

If you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

IRC: #reproducible-builds on irc.oftc.net.
Mastodon: @reproducible_builds@fosstodon.org
Mailing list: rb-general@lists.reproducible-builds.org

Russ Allbery: Review: Ties That Bond in Gretna Green

Wed, 14 Oct 2026 03:50:00 +0000

Review: Ties That Bond in Gretna Green, by Linzi Day

Series:	Midlife Recorder #3
Publisher:	Linzi Day
Copyright:	February 2023
ISBN:	9798376517017
Format:	Kindle
Pages:	616

Ties That Bond in Gretna Green is a self-published fantasy novel and the third book in the Midlife Recorder series. As with the previous book, it picks up almost immediately after Painting the Blues in Gretna Green. Day calls the genre paranormal women's fantasy, and that sounds about right to me.

There is an intervening short story that you can get by joining Day's mailing list (along with an epilogue to the first book and to this book). I don't think it's that important, but there are frequent references to it at the start of this novel that become somewhat annoying if you haven't read it.

Valentine's Day is fast approaching. This the busiest day of the year for the part of the Recorder's job that Niki already knew how to do: marrying people. She performed marriage ceremonies in her previous job before her inheritance, and she loved that work despite her awful boss. Performing marriages in the Gateway sounds even more rewarding, but the sheer number of couples and the political complications from the first two books create logistical problems she has to solve first.

Also, the remaining member of her staff held over from her grandmother's time has returned from vacation to discover that Niki has upended most of what she thought she knew about the job. Time for Niki to apply what she learned from the change management training her old boss forced her to attend and then ignored! (If you just groaned, rest assured that Day somehow makes this work, although she clearly has a higher opinion of corporate training than I do.)

This plot was more to my taste than Painting the Blues, mostly because Niki seemed on top of the problems and didn't postpone looking at them for half the book. There is more of the management competence porn that readers have come to expect of the series, a few more revelations about Niki's magic, more mysterious manifestations and the first mention of a prophecy, and a few political developments. As always, the pacing is exceptional. These books grab me and pull me along, page after page, often robbing me of sleep because I find them nearly impossible to put down.

Ties that Bond (and to some extent the last book) looked like it was going to introduce a romantic subplot, and I was preparing to be annoyed by it because I did not like the man in the subplot at all. I won't spoil how it works out in this book, but I will say that Niki surprised me and showed more sense than I thought the author was telegraphing. This is not the first time that Day has surprised me with what I thought was foreshadowing that did not turn out how I expected, usually for the better. If she can keep that up, it's a nice effect (if a bit unbalancing) and adds to my desire to read just one more chapter.

The way the world-building of these books is structured continues to intrigue me. Day gets away with some problems that I think would be more noticeable in other books thanks to the excellent pacing (no time to ponder the world-building, we're on to the next crisis!) and the tight third-person perspective. Niki is not a detail person, to say the least, but she does keep returning to bits of world-building and poking at them a bit harder, which gives Day repeated opportunities to shore up ideas that felt shaky and dubious at first glance. Still, this is not a book that prizes deep logical consistency or full exploration of the ramifications of a bit of magic. You have to be willing to go along with the ride and not think too hard.

For example, Niki can see bonds between couples and judge their strength. This is apparently a long-standing power of the Recorder's line (she was able to do that before she became the Recorder), and part of her responsibility in these weddings is to check the bonds of the couples. This leads to some well-handled scenes where she diagnoses a problem or resolves a conflict because she can magically see the true relationship structure.

Everyone in the book just takes this power in stride. This is wild to me! This ability would completely upend half of society if you fully worked out its ramifications and could find people other than Niki with the same ability. Even if one assumes that a bond only forms over time and can't be sensed in the early stages of a relationship (something the book never establishes), can you imagine the implications of having an infallible oracle that says at a glance whether a marriage will work (permanently, the book strongly implies)? The implications for how to structure marriage, for family planning, for psychology and psychiatry, for how to structure dating, even for living arrangements and housing markets? This is not a small world-building detail, and yet it's treated more like part of Niki's characterization than like a foundation of society.

I think some of this all-vibes world-building may come from the general new-age feel to how magic works. Day makes a grab-bag of random magic canonical in this world: psychic lie detecting abilities, auras, chakras, premonitions, and other bits of the sort of spiritualism that tends to be heavily marketed to middle-class women. I have that niggling feeling that one sometimes gets in SF that a lot of this is in the world-building because the author believes it's partly real (see, for instance, psychic powers and the Dean drive in 1960s science fiction). If one believes that psychic powers and various bits of mysticism are true in our world, one has already developed the rationalization mechanisms to explain away their almost total lack of influence or impact on how the world is structured. If one then introduces them into a true fantasy world, one may not notice how many implications that should have for how society is structured, since one is used to believing magic exists but has no significant implications.

I could be entirely wrong about this analysis, and maybe it's a bit unfair to Day. I should also be clear that this is not a complaint, just a point of fascination to me when I think back over one of these books after I finished it. There is a glut of fantasy out there that's constructed like an engineering problem or that goes deep into politics or social theory, usually written by people with strong opinions but not a lot of training in real sociology. One of the joys of self-published books is that you occasionally get something that assembles genre conventions in a way that feels odd and delightfully strange. What if, in addition to dimensional gates and overwhelming protean power invested in a true heir, all the magic sold by the local Tarot and crystal store was also true? Sure, why not! If the pacing is good and the story is grabby, it works for me.

It does seem worth attaching a warning for the folks who need scientific reproducibility and explored implications in their world-building, though. If you're the sort of reader who is bothered by political boundaries and economic systems that match our world despite the existence of magic, this series may cause you problems.

This continues to be a grabby, highly entertaining story of a woman who finally gets to run her own small business the way that she always thought the business should be run after years of working for an awful manager, except that her business is total magical power over an interchange point between dimensions, she's the chosen one, and the setting is a high fantasy world with prophecies and gods. If that sounds appealing, don't start here, but I highly recommend giving Midlife in Gretna Green a try. The series seems to be holding up.

Followed by a short story epilogue available by joining Day's mailing list, an optional novella (maybe novelette) published in Spilling the Tea in Gretna Green, and then Seeing Red in Gretna Green.

Rating: 7 out of 10

Freexian Collaborators: Debian Contributions: New experimental backend for autopkgtest using pconr, DebConf site visit and more! (by Anupa Ann Joseph)

Wed, 14 Oct 2026 00:00:00 +0000

Debian Contributions: 2026-09

Contributing to Debian is part of Freexian’s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

DebConf site visit, by Stefano Rivera

In preparation for DebConf 27, Stefano Rivera, Nattie Mayer-Hutchings, and Jongmin Kim from the DebConf Committee visited Asahikawa Japan. A contingent of the local team gathered to tour the venues with us, discuss plans, and meet the local organizations assisting the event. We held a press conference at the city hall that got some coverage. A few potential day-trip options were explored. Photos from the site visit.

autopkgtest-virt-pconr, by Helmut Grohne

Following the creation of the pconr module that provides a basis for unschroot and a more secure containment for mmdebstrap, an experimental autopkgtest backend autopkgtest-virt-pconr is now available. It fits a spot between autopkgtest-virt-unshare and more fully fledged containers as it does not require much infrastructure like setting up incus or lxc but still provides a containment running an initsystem. Due to the use of erofs as base image format, it boots and reverts quickly. This development also required fixing concurrency issues in asyncvarlink and even shed light on a matching bug in systemd that was promptly fixed upstream.

Miscellaneous contributions

Carles reviewed and submitted six Catalan po-debconf translations using po-debconf-manager. Improved po-debconf-manager’s workflow for updating translations.
Carles reviewed, translated or updated webwml Catalan translations for security and CD pages. He also fixed issues that prevented building webwml, deleted orphaned translation pages, etc. and experimented with a more global HTML tidying up experiment.
Carles refactored check-relations adding capacity to ignore concrete from_package -> to_package specific relations and more flexibility around ignores. Detects unused ignore rules as well.
Carles improved some Wiki pages (LibreOffice, Framework amongst some other ones)
Thorsten did an hplip upload to replace an expired certificate of HP. This certificate is used to sign new upstream releases and modules that can be downloaded later. Afterwards work on a new upstream version started.
Thorsten also struggles with autopkgtest problems of the new upstream version of cups. Work is still ongoing.
Antonio loaded the video recording URLs into the MiniDebConf Winterthur 2026 website, and deployed the website for MiniDebConf Curitiba 2027 (still very early work in progress at this point).
Antonio uploaded debci 4.3, autodep8 0.31, gem2deb 2.2.10, ruby-sass 3.7.4-7, init-system-helpers 1.69+nmu2 and 1.69+nmu3.
Antonio worked on several topics around Debian CI maintenance, reliability and performance.
Stefano updated the autopkgtests for cPython packages in Debian to support setuptools 80.
Stefano uploaded pypy 8.
Stefano helped to get DebConf 26 reimbursement claims processed, and worked on some of the resulting issues in debian-reimbursements.
Emilio managed various transitions.
Emilio worked on the rustc-web/trixie bootstrap for armel, using the rustc 1.95 version from trixie-backports. This will be needed by the upcoming clamav security updates.
Helmut sent patches for 11 cross build failures.
Helmut introduced a new build profile to libcap-ng to keep architecture cross bootstrap working.
Helmut uploaded debvm_0.5.5 introducing support for Hurd thanks to a lot of work by Johannes Schauer Marin Rodrigues.
Colin worked with OpenSSH upstream to reduce the linkage of /usr/sbin/sshd, hardening it a little further.
Colin upgraded to new security releases of groff and parted.
Colin upgraded 50 Python packages to new upstream versions, and fixed over 40 RC bugs in the Python team.
Santiago continued mentoring Aryan Karamtoth with the GSoC project about introducing livepatching support for linux. This mentoring is done in collaboration with Emmanuel Arias. In particular, Santiago explored different requirements for providing binary modules for the same kernel packages used by Debian, that require a matching version number.
Anupa joined Jean-Pierre Giraud to prepare the files for point release announcement for Debian 13.7.

Dirk Eddelbuettel: RQuantLib 0.4.29 on CRAN: New QuantLib, Plus Small Fixes

Tue, 13 Oct 2026 21:07:00 +0000

A new release 0.4.29 of RQuantLib arrived on CRAN this evening, had already been built for r2u as well as on r-universe and has just been uploaded to Debian.

QuantLib is a rather comprehensice free/open-source library for quantitative finance. RQuantLib connects (some parts of) it to the R environment and language, and has been part of CRAN for twenty-three years (!!) as it was one of the first packages I uploaded to CRAN.

This release of RQuantLib brings two new calendars (Malaysia, Philippines), updates to a number of other calendars as well to other files, and two deprecations we are reflecting in this release. It also benefits from a number of careful and attentive pull requests by Maximilian Muecke cleaning up an (astonishing !!) number of likely rather old little bugs. Full details from the NEWS file follow as usual.

Changes in RQuantLib version 0.4.29 (2026-10-13)

Configure check for outdated QuantLib version updated,

Adjust two instantiations on macOS x86_64 with old compilers

Correct Euribor2W and Euribor3W tenors setters (Maximilian Muecke in #196)

Accect Euribor1W as alias for EuriborSW tenor (Maximilian Muecke in #197)

Correct default handling of the payFixed parameter (Maximilian Muecke in #198)

Assign missing S3 class to American option implied volatitly return (Maximilian Muecke in #199)

Correct spelling in manual pages and R code (Maximilian Muecke in #202, #203)

Support additional Polish settlements (Maximilian Muecke in #204)

Check for curve parameters in FittedBondCurve (Dirk in #205 fixing #201)

Reflect two deprecations in QuantLib 1.44 and adjust code in two spot (Dirk in #206)

Courtesy of my CRANberries, there is also a diffstat report for the this release. As always, more detailed information is on the RQuantLib page. Questions, comments etc should go to the rquantlib-devel mailing list. Issue tickets can be filed at the GitHub repo.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can now sponsor me at GitHub.

Matthew Garrett: Linux Lockdown and Hibernation (again)

Tue, 13 Oct 2026 18:14:36 +0000

(This is an updated version of an older post - the introduction remains the same, the technical details are different)

Linux draws a distinction between code running in kernel (kernel space) and applications running in userland (user space). This is enforced at the hardware level - in x86-speak¹, kernel space code runs in ring 0 and user space code runs in ring 3². If you’re running in ring 3 and you attempt to touch memory that’s only accessible in ring 0, the hardware will raise a fault. No matter how privileged your ring 3 code, you don’t get to touch ring 0.

Kind of. In theory. Traditionally this wasn’t well enforced. At the most basic level, since root can load kernel modules, you could just build a kernel module that performed any kernel modifications you wanted and then have root load it. Technically user space code wasn’t modifying kernel space code, but the difference was pretty semantic rather than useful. But it got worse - root could also map memory ranges belonging to PCI devices³, and if the device could perform DMA you could just ask the device to overwrite bits of the kernel⁴. Or root could modify special CPU registers (“Model Specific Registers”, or MSRs) that alter CPU behaviour via the /dev/msr interface, and compromise the kernel boundary that way.

It turns out that there were a number of ways root was effectively equivalent to ring 0, and the boundary was more about reliability (ie, a process running as root that ends up misbehaving should still only be able to crash itself rather than taking down the kernel with it) than security. After all, if you were root you could just replace the on-disk kernel with a backdoored one and reboot. Going deeper, you could replace the bootloader with one that automatically injected backdoors into a legitimate kernel image. We didn’t have any way to prevent this sort of thing, so attempting to harden the root/kernel boundary wasn’t especially interesting.

In 2012 Microsoft started requiring vendors ship systems with UEFI Secure Boot, a firmware feature that allowed⁵ systems to refuse to boot anything without an appropriate signature. This not only enabled the creation of a system that drew a strong boundary between root and kernel, it arguably required one - what’s the point of restricting what the firmware will stick in ring 0 if root can just throw more code in there afterwards? What ended up as the Lockdown Linux Security Module provides the tooling for this, blocking userspace interfaces that can be used to modify the kernel and enforcing that any modules have a trusted signature.

But that comes at something of a cost. Most of the features that Lockdown blocks are fairly niche, so the direct impact of having it enabled is small. Except that it also blocks hibernation⁶, and it turns out some people were using that. The obvious question is “what does hibernation have to do with keeping root out of kernel space”, and the answer is a little convoluted and is tied into how Linux implements hibernation. Basically, Linux saves system state into the swap partition and modifies the header to indicate that there’s a hibernation image there instead of swap. On the next boot, the kernel sees the header indicating that it’s a hibernation image, copies the contents of the swap partition back into RAM, and then jumps back into the old kernel code. What ensures that the hibernation image was actually written out by the kernel? Absolutely nothing, which means a motivated attacker with root access could turn off swap, write a hibernation image to the swap partition themselves, and then reboot. The kernel would happily resume into the attacker’s image, giving the attacker control over what gets copied back into kernel space.

This is annoying, because normally when we think about attacks on swap we mitigate it by requiring an encrypted swap partition. But in this case, our attacker is root, and so already has access to the plaintext version of the swap partition. Disk encryption doesn’t save us here. We need some way to verify that the hibernation image was written out by the kernel, not by root. And thankfully we have some tools for that.

Trusted Platform Modules (TPMs) are cryptographic coprocessors⁷ capable of doing things like generating encryption keys and then encrypting things with them. You can ask a TPM to encrypt something with a key that’s tied to that specific TPM - the OS has no access to the decryption key, and nor does any other TPM. So we can have the kernel generate an encryption key, encrypt part of the hibernation image with it, and then have the TPM encrypt it. We store the encrypted copy of the key in the hibernation image as well. On resume, the kernel reads the encrypted copy of the key, passes it to the TPM, gets the decrypted copy back and is able to verify the hibernation image.

That’s great! Except root can do exactly the same thing. This tells us the hibernation image was generated on this machine, but doesn’t tell us that it was done by the kernel. We need some way to be able to differentiate between keys that were generated in kernel and ones that were generated in userland. TPMs have the concept of “localities” (effectively privilege levels) that would be perfect for this. Userland is only able to access locality 0, so the kernel could simply use locality 1 to encrypt the key. Unfortunately, localities are typically only available on systems that implement a Dynamic Root of Trust Measurement like Intel’s TXT, and most consumer systems have no support for this. So, we need another approach.

TPMs have a set of Platform Configuration Registers (PCRs), intended for keeping a record of system state. The OS isn’t able to modify the PCRs directly. Instead, the OS provides a cryptographic hash of some material to the TPM. The TPM takes the existing PCR value, appends the new hash to that, and then stores the hash of the combination in the PCR - a process called “extension”. This means that the new value of the TPM depends not only on the value of the new data, it depends on the previous value of the PCR - and, in turn, that previous value depended on its previous value, and so on. The only way to get to a specific PCR value is to either (a) break the hash algorithm, or (b) perform exactly the same sequence of writes. On system reset the PCRs go back to a known value, and the entire process starts again.

Some PCRs are different. PCR 23, for example, can be reset back to its original value without resetting the system. We can make use of that. The first thing we need to do is to prevent userland from being able to reset or extend PCR 23 itself. All TPM accesses go through the kernel, so this is a simple matter of parsing the write before it’s sent to the TPM and returning an error if it’s a sensitive command that would touch PCR 23. We now know that any change in PCR 23’s state will be restricted to the kernel.

When we encrypt material with the TPM, we can ask it to record the PCR state. This is given back to us as metadata accompanying the encrypted secret. Along with the metadata is an additional signature created by the TPM, which can be used to prove that the metadata is both legitimate and associated with this specific encrypted data. In our case, that means we know what the value of PCR 23 was when we encrypted the key. That means that if we simply extend PCR 23 with a known value in-kernel before encrypting our key, we can look at the value of PCR 23 in the metadata. If it matches, the key was encrypted by the kernel - userland can create its own key, but it has no way to extend PCR 23 to the appropriate value first. We now know that the key was generated by the kernel.

Unfortunately it turns out that some people actually make use of PCR 23, and restricting it to the kernel makes them sad. There are other resettable PCRs, but only in non-0 localities, so (a) we can’t reset them on most systems and (b) we’ll just find someone who uses them anyway and run into the same problem. We need a different approach.

Thankfully TPMs have a small chunk of non-volatile RAM that can be used for storing things, and by “storing” I mean they can be used in a range of different ways. One of these is effectively as additional PCRs. These values can be configured such that they work the same way as PCRs, with the only way to modify them being to append a new hash to their existing value and update the new value to the hash of that merged value. We can allocate one of these for in-kernel use and reject any access from userspace, and also there are officially allocated ranges (so people shouldn’t be using random values) and the namespace is large enough anyway that w eshouldn’t collide with anyone, so we can carve one of those out and use it for this purpose.

Unfortunately, though, these NV indexes aren’t included in the creation data we get when we create a key, so we need another approach. TPMs have the concept of sessions, a series of commands executed in sequence. A flag allows these sessions to be “audited”, with the TPM keeping a running track of the hash of the commands executed and the results returned. At the end of the session you can ask for a signed copy of this hash, and if you’ve kept a log of all the commands then you can verify that they match that signed hash and know that this log represents a real communication with the TPM. If we read the NV index and generate the key inside the same session, we can verify that the key we’re looking at was created while the NV index had a specific value, and if only the kernel can set that value then we know that the key was generated by the kernel.

Or, well, can we? Only new kernels would impose the restriction on modifying that NV index. An attacker could boot an old kernel, generate a key there in userland, sign a hibernation image with it, and then reboot into a new kernel. The new kernel would see a valid signature with a valid NV index associated with it and have no way to know it was generated from userland rather than the kernel. We need to be able to tell the difference between kernels that implement this feature and ones that don’t, and we need to do that without being able to go back in time to change old kernel behaviour. We can extend a PCR to indicate we implement the new functionality, but so can an attacker running an old kernel.

The normal approach to determining whether an event occurred in a specific phase of the boot process is to “cap” the PCRs - extend them with a known value that indicates a transition between stages of the boot process. Any events that occur before the cap event must have occurred in the previous stage of boot, and since the final PCR value depends on the order of measurements and not just the contents of those measurements, if a PCR is capped before userland runs, userland can’t fake the same PCR value afterwards. If Linux capped the PCRs before userland started running, we’d be able to place a measurement there before the cap occurred and then prove that that extension occurred before userland had the opportunity to interfere. We could simply place a statement that the kernel supported the NV index restrictions there, and we’d be fine.

Unfortunately Linux doesn’t currently do this, and adding support for doing so doesn’t fix the problem - if an attacker boots a kernel that doesn’t cap a PCR, they can just cap it themselves from userland. So, we’re faced with the same problem: booting an older kernel allows the system to be placed in an identical state to the current kernel, and a fake hibernation image can be written out. Solving this requires a PCR that was being modified after kernel code was running, but before userland was started, even with existing kernels.

Thankfully, there is one! PCR 5 is defined as containing measurements related to boot management configuration and data. One of the measurements it contains is the result of the UEFI ExitBootServices() call. ExitBootServices() is called at the transition from the UEFI boot environment to the running OS, and the kernel contains code that executes before it. So, if we measure an assertion regarding whether or not we support restricted access to NV indexes into PCR 5 before we call ExitBootServices(), this will prevent userspace from spoofing us (because userspace will only be able to extend PCR 5 after the firmware extended PCR 5 in response to ExitBootServices() being called). Obviously this depends on the firmware actually performing the PCR 5 extension when ExitBootServices() is called, but if firmware’s out of spec then I don’t think there’s any real expectation of it being secure enough for any of this to buy you anything anyway.

That’s what this patchset does. Review feedback so far seems positive, although James Bottomley suggested a design improvement. My approach of using an NV index as a PCR and generating a signing key made sense as a consequence of my original approach involving PCR 23, which had been to use the key creation data and not use audit sessions at all. But the goal isn’t to use a key - it’s to prove that hibernation occurred in-kernel, and while signing is one way of doing that, there are others. His suggestion is to simply record the hash of the hibernation image into the NV index and then read that back as part of the audit session. On resume we verify the audit session log is legitimate, read the hibernation image, and compare the hash of the hibernation image against the hash in the log. If it matches, and if the PCR 5 value matches, we know the audit session happened in kernel and that the hibernation image hasn’t been modified.

It still seems like we’re missing something, though. If we’re not storing a key anywhere, how do we verify the audit session? To explain this we’re going to need to go into some details about how TPM keys work in the first place. TPMs can produce a special kind of key called an Attestation Key, or AK. Attestation keys are used to sign attestation statements from the TPM, such as PCR quotes or audit logs. We need a separate key type for this in order to prove that the signature was generated as part of an attestation - normal TPM signing keys are fundamentally designed to sign arbitrary material, and so can be used by userland to sign something that looks identical to an attestation record. By being able to distinguish the types of key the TPM uses, we can prove that a signature was generated using an AK, and so know that it’s a real TPM attestation (because nothing other than the TPM can sign stuff with an AK).

But even beyond this distinction, TPMs have different key types. Ordinary keys are generated using an RNG and will be unique. Primary keys are generated using a seed that is used as an input into a key derivation function. For a given TPM, using the same seed to generate the same type of primary key will always generate the same primary key⁸. We can have the kernel deterministically generate an AK during suspend in order to sign the audit log, and then generate the same key again on resume to validate it. This means we don’t need any other form of trusted storage for the AK - the TPM already provides that functionality.

This is all rather complicated but I’ve been thinking about this for some time now and I haven’t come up with a cleaner solution. The only real open issue is the degree to which machines actually perform the PCR 5 extension. If it turns out there’s a bunch that don’t we’ll need to come up with some alternative approach to identifying whether the kernel supports this functionality, but the design is such that that should be invisible to userspace so adding alternatives later shouldn’t be an issue. Filtering accesses to the NV index is also not super clean, and depends on there not being alternative mechanisms to get at the TPM by sending raw commands. Again, this is intended to be opaque to userland and can be improved if we come up with something better later on (such as a secure way to pass a secret to the kernel on boot that can be used as an auth value for acess to the NV index).

Anyway. Time to go and fix the next thing.

Other architectures use different terminology here, such as “supervisor” and “user” mode, but it’s broadly equivalent ↩︎
In theory rings 1 and 2 would allow you to run drivers with privileges somewhere between full kernel access and userland applications, but in reality we just don’t talk about them in polite company ↩︎
This is how graphics worked in Linux before kernel modesetting turned up. XFree86 would just map your GPU’s registers into userland and poke them directly. This was not a huge win for stability ↩︎
IOMMUs can help you here, by restricting the memory PCI devices can DMA to or from. The kernel then gets to allocate ranges for device buffers and configure the IOMMU such that the device can’t DMA to anything else. Except that region of memory may still contain sensitive material such as function pointers, and attacks like this can still cause you problems as a result. ↩︎
This describes why I’m using “allowed” rather than “required” here ↩︎
Saving the system state to disk and powering down the platform entirely - significantly slower than suspending the system while keeping state in RAM, but also resilient against the system losing power. ↩︎
With some handwaving around “coprocessor”. TPMs can’t be part of the OS or the system firmware, but they don’t technically need to be an independent component. Intel have a TPM implementation that runs on the Management Engine, a separate processor built into the motherboard chipset. AMD have one that runs on the Platform Security Processor, a small ARM core built into their CPU. Various ARM implementations run a TPM in Trustzone, a special CPU mode that (in theory) is able to access resources that are entirely blocked off from anything running in the OS, kernel or otherwise. ↩︎
Unless the TPM is cleared, in which case it’ll generate a new internal seed and now the keys will be different to before the clear ↩︎

Steinar H. Gunderson: Decompilation patterns, part 10: return var_v0

Tue, 13 Oct 2026 15:27:00 +0000

The v0 register on MIPS is special in that it is the return register (like rax is on x86-64), so when you see code like this:

if (x == 3) {
    var_v0 = 1;
} else if (y == 4) {
    ...
    var_v0 = 3;
}
var_v0 = 5;
return var_v0;

then you have to consider the possibility that the intended match is:

if (x == 3) {
    return 1;
} else if (y == 4) {
    ...
    return 3;
} else {
    return 5;
}

Whether you put the last return in an else block or not is irrelevant for the match, of course, it's purely a matter of taste.

Maytham Alsudany: Menus without JavaScript

Mon, 12 Oct 2026 23:34:00 +0000

This is more of a note to myself since I keep forgetting and "rediscovering" this technique every time I need it, but if it helps you, great!

The JavaScript way is to toggle displaying the menu based on a button click. For instance, here's an example in Svelte:

[This interactive/preview is only available on the website.]

<script lang="ts">
	let showMenu = $state(false);
</script>

<button onclick={() => (showMenu = !showMenu)}>
	{#if showMenu}
		Hide menu
	{:else}
		Show menu
	{/if}
</button>
<nav class:hidden={!showMenu}>
	<ul>
		<li>Home</li>
		<li>Blog</li>
		<li>Foo</li>
		<li>Bar</li>
	</ul>
</nav>

<style>
	.hidden {
		display: none;
	}
</style>

But there is a hack to use a hidden checkbox and some CSS to achieve the same thing without any JavaScript. The example here turns the menu button into a label that toggles the checkbox, and uses the checkbox state to determine when to show the menu via the next-sibling combinator.

[This interactive/preview is only available on the website.]

<input type="checkbox" id="menu-state" />
<div class="menu-ctn">
	<label class="menu-toggle" for="menu-state">
		<span class="menu-closed">Show menu</span>
		<span class="menu-open">Hide menu</span>
	</label>
	<nav class="menu-open">
		<ul>
			<li>Home</li>
			<li>Blog</li>
			<li>Foo</li>
			<li>Bar</li>
		</ul>
	</nav>
</div>

<style>
	#menu-state {
		display: none;
	}
	.menu-open {
		display: none;
	}
	.menu-closed {
		display: block;
	}
	#menu-state:checked + .menu-ctn .menu-open {
		display: block;
	}
	#menu-state:checked + .menu-ctn .menu-closed {
		display: none;
	}
</style>

Steinar H. Gunderson: Decompilation patterns part 9, sign extension

Mon, 12 Oct 2026 21:12:00 +0000

Today, for something completely different:

s.x = (s16) ((s32) (temp_v0 << 0x10) >> 0x11);

MIPS has 16-bit loads and stores, but not 16-bit (signed) arithmetic, so if it wants to do that, it needs to sign-extend to 32-bit first. And it does that by first shifting up by 16 so that the 16-bit sign bit is at the 32-bit sign bit, and then it can do an arithmetic shift afterwards. So what you want is:

s16 temp_v0;

s.x = temp_v0 >> 1;

Sometimes, it can be pretty stubborn, and you'll need to go through memory or similar before GCC really inserts the shift patterns you want.

Maytham Alsudany: There's more to CSS for underlining

Mon, 12 Oct 2026 12:09:00 +0000

I read Ruben Schade's notes on underlining and wanted to add more, as adding a border-bottom and leaving at that seemed incomplete to me.

Modern

Of course, you could just use the modern choice. Here, I've shortened what Schade uses into one line of CSS (because I can). As noted, this is a fairly new feature so not every browser supports this.

[This interactive/preview is only available on the website.]

.underline-me {
	text-decoration: underline red solid 3px;
}

Workarounds

Since some browsers don't support text-decoration, here are the alternatives I could think of.

border-bottom

The workaround Schade describes is using border-bottom, though it has a gap between the text in the line.

[This interactive/preview is only available on the website.]

I am <span class="underline-me">underlining this yap</span> within the sentence.

.underline-me {
	border-bottom: red solid 3px;
}

::after

Probably the better way is to create an ::after element, which gets very close, but displays above the text (covering the letters 'g' and 'y').

[This interactive/preview is only available on the website.]

I am <span class="underline-me">underlining this yap</span> within the sentence.

.underline-me {
	position: relative;
}
.underline-me::after {
	content: '';
	position: absolute;
	width: 100%;
	height: 3px;
	background-color: red;
	left: 0;
	bottom: 2px;
}

::after in a container

If you use a container (in this case, two nested <span>s instead of just one), then you can get very close with the underline displaying below the text.

[This interactive/preview is only available on the website.]

I am
<span class="underline-me-ctn">
	<span class="underline-me">underlining this yap</span>
</span>
within the sentence.

.underline-me-ctn {
	position: relative;
}
.underline-me {
	z-index: 10;
	position: relative;
}
.underline-me-ctn::after {
	content: '';
	position: absolute;
	width: 100%;
	height: 3px;
	background-color: red;
	left: 0;
	bottom: 2px;
}

::after in a container with text stroke

And now if you add a stroke to the text via -webkit-text-stroke, you're pretty much there, though this may not be feasible in some situations (e.g. gradient or image background behind the text). Support for -webkit-text-stroke is not that much better than text-decoration though, so make of that what you will.

[This interactive/preview is only available on the website.]

I am
<span class="underline-me-ctn">
	<span class="underline-me-outline">underlining this yap</span>
	<span class="underline-me">underlining this yap</span>
</span>
within the sentence.

.underline-me-ctn {
	position: relative;
}
.underline-me-outline {
	z-index: 5;
	position: absolute;
	left: 0;
	color: var(--background);
	-webkit-text-stroke: 0.3em var(--background);
}
.underline-me {
	z-index: 10;
	position: relative;
}
.underline-me-ctn::after {
	content: '';
	position: absolute;
	width: 100%;
	height: 3px;
	background-color: red;
	left: 0;
	bottom: 2px;
}

Steinar H. Gunderson: Decompiler patterns, part 8: Un-repetition of conditions

Sun, 11 Oct 2026 15:07:00 +0000

Today, for a slightly more complicated snippet, but still in the same general area; say you have code like this:

x = (0x1000 - y) / 24;
z = var_s5 < 5;
if (x >= 0x81) {
    x = 0x80;
    z = var_s5 < 5;
}
var_s4 = 0;
if (z == 0) {

In particular, note the z = var_s5 < 5; repeated. Most likely, this is the compiler sticking stuff into branch delay slots, or else re-checking the condition if var_s5 changed in the branches (it does not here). You almost certainly want to undo this into:

x = (0x1000 - y) / 24;
if (x >= 0x81) {
    x = 0x80;
}
var_s4 = 0;
if ((var_s5 < 5) == 0) {

and the if, as we already know, should probably rather then be:

if (var_s5 >= 5) {

For a small bonus (since I'm not going to have a separate post about it), you can choose to change the upper if to:

if (x > 0x80) {
    x = 0x80;
}

which generates exactly the same code (on MIPS), but may in many cases be easier to understand.

Russ Allbery: Review: Daggerbound

Sun, 11 Oct 2026 04:48:00 +0000

Review: Daggerbound, by T. Kingfisher

Series:	Swordheart #2
Publisher:	Bramble
Copyright:	2026
ISBN:	1-250-40009-0
Format:	Kindle
Pages:	436

Daggerbound is a secondary-world fantasy and a sequel to Swordheart, although it follows different protagonists for most of the book. It's also a sort of sequel to the Clocktaur War duology in that one of the protagonists was a protagonist of those books. T. Kingfisher is the pen name Ursula Vernon uses for her adult fiction.

Learned Edmond was once a devout acolyte of the Order of the Many-Armed God and a true believer in its teachings, including the ones about the evils of women. Then he went on an adventure with, among other people, a forger named Mistress Slate, during which he learned a great deal of things about the world that his order did not teach him. He has spent the subsequent years trying to bring this important new information to his order and encourage them to adjust their view of the world accordingly.

The order has not changed, and Edmond is very tired.

Someone needs to carry a number of books and a magical sword to the city of Archon's Glory. Edmond has volunteered and intends to perform the task exactly as expected, and then never return. He is unsure what he will do then, but at least it will be different.

Edmond did not expect to be waylaid by bandits or to accidentally draw the magical sword. He certainly did not expect the man who appeared in a flash of light and violently saved him from the bandits.

It would have been very convenient for the Dervish if Edmond died of his injuries after drawing the sword. That would leave the sword without a wielder and therefore the Dervish without someone he had to protect. All he would have to do was sit and watch while the fever and cold and lack of water did the work, and then he would be free. Given his past experience with wielders, no one could even blame him. Except maybe his own conscience.

I did not realize I wanted to read a novel about a traumatized Mercedes Lackey sword waking up in a T. Kingfisher universe, but apparently I did.

The Dervish is not a sword, precisely, at least not in the way that Need has become by the time we meet her in Lackey's novels. He's a man trapped in a sword, he doesn't like it, and he would very much like it to stop. But at the start of the book, he has the rest of the vibe of a Mercedes Lackey protagonist: vast past trauma, poor emotional regulation skills, and a prickly cynicism that only runs skin deep. Pairing him with an Edmund who is far more mature than in the earlier duology but still rather innocent and delightfully neurodivergent is a great touch.

The rest of the plot was fine but not that memorable. Like the Clocktaur series, there is a strong feeling of episodic D&D adventure as the characters stumble across disconnected problems and hostilities while collecting party members. Like Ursula Vernon's occasional D&D recaps, this party has a tendency to adopt everyone they come in contact with, which includes a gnole (as always one of the best parts of the book) and a sentient giant pill bug. The pill bug, who has a complex appendage-operated mechanical talk box and a banner that says "I DO NOT EAT HUMAN MEAT," is the most Ursula Vernon character that has ever existed in fiction.

There is a romance because there is always a romance in the novels set in this universe. I didn't mind this one. Like every Kingfisher romance, it involves a lot of irritating refusal to communicate and endless angst about how the other person couldn't possibly be in love with them, but the characters have rather more justification than usual and at least I didn't spend most of the book thinking one half of the romantic pairing was an idiot. Apparently it helps if no paladins are involved.

The strongest parts of this book are the beginning, before the Lackey vibes unfortunately drain out of the story, and the end, when all of the best characters from Swordheart show up again. The Temple of the White Rat continues to be the best feature of this fictional universe, and I could read endless books about how they solve problems.

The Dervish gazed at her with admiration. "And here I thought you'd be on the side of law and order..."

"No, young man," said Beartongue, despite being several centuries his junior. "I am on the side of justice. If we're lucky, the two run in parallel. If they don't, we bend the law to attain justice, not the other way around."

The ending also featured some exploration of the edge cases of the rules for the sentient swords that reminded me a bit of Fred Saberhagen with better characterization.

Daggerbound was not as charming as Swordheart, mostly because Halla appeared only at the end. I wish Kingfisher had leaned more into the Mercedes Lackey vibes rather than taking her normal D&D-flavored romance approach. But this was enjoyable, charming at times, had great supporting characters like all Kingfisher novels, and was a satisfying continuation of the series. I am looking forward to the third (and I believe final) book, which is supposed to be out next year.

Recommended if you liked Swordheart.

Followed by the not-yet-published Shieldborn.

Rating: 7 out of 10

Tim Retout: Reading my solar inverter over RS485

Sat, 10 Oct 2026 11:00:00 +0000

For over ten years, the only way I have had of knowing what our solar panels are doing has been an impulse monitor on the generation meter, counting the flashes of its LED. It has always been a bit flaky due to battery changes or loose connections, and there has never been a way to see solar generation alongside the energy used by the rest of the house. This week I have fixed that, by building a small ESPHome sensor which talks directly to the inverter. I am still reeling slightly: with AI assistance, it took under a week from idea to working implementation, and it is a project I would certainly never have attempted otherwise. The result is zeversolar-esphome.

The inverter is a Zeversolar Zeverlution 3680, which has an RS485 port but no Wi-Fi or Ethernet module. It doesn’t speak Modbus; it uses Eversolar’s own master/slave protocol, which nobody has officially documented but which several people have reverse-engineered over the years (credit to eversolar-monitor, Heliograph and others). Manufacturer support for Eversolar/Zeversolar inverters apparently ended in December 2019 when the company went out of business.

The rating plate on my inverter.

A while ago I had looked into what ports were available on this inverter with a view to connecting some sort of monitoring, but I had abandoned it as “too hard”. While working on some Home Assistant configuration, Claude suggested the idea again, but similarly wrote it off initially. I encouraged it to explore a bit further, and supplied the model number of the inverter, at which point the picture got a lot more promising. After a bit of back-and-forth about hardware, we settled on an M5Stack Atom Lite on an Atomic RS485 Base. The main attraction was that it already comes in a case, so I didn’t need to design (or, more likely, bodge) an enclosure.

While I waited for the parts to arrive, Claude wrote the firmware: an ESPHome external component built around a small, dependency-free C++ driver, with host-side unit tests against byte captures that other people had published from other models. I found it slightly surreal to have a tested protocol driver before owning any hardware to run it on.

Cables

The parts came before the tools I needed to get into the inverter safely (a DC clamp meter and a T25 screwdriver bit), so in the meantime I made up an RS485 cable - this uses an RJ45 connection at one end, and some custom wiring at the other. My first attempt was with some CAT 6, but (as Claude had pointed out and I had ignored) its solid-core conductors are much harder to twist together. So I gave up and sacrificed an old CAT 5e patch lead instead, which went much better.

The custom end of the cable, before being taped up.

The risky bit

On a Zeverlution, the RJ45 sockets are inside the wiring compartment, which means taking the cover off to install the monitor. The manual addresses this part to qualified electricians. So the step I was most nervous about was not the software at all, but safely isolating the inverter.

Inside the inverter, with the cover off.

I did this with appropriate caution, following the instructions from the manual carefully, and also waiting until after dark just in case. Now that I understand how the DC clips from the panels work, I can see how to do this safely during daytime too – but hopefully this won’t be necessary.

Plugged in, and threaded through the cable gland.

Warning: if you’re not confident, I would always advise to get an electrician to do this bit. Do what I say, not what I do.

Debugging over Wi-Fi

Once the device was installed, the nice thing about ESPHome is that I never need to go back in the loft again to update it – it reflashes over Wi-Fi. I’ve taken full advantage of this for debugging, and for reading the wire protocol directly from the logs.

The finished device. Green means generating.

Separately, I’ve used Claude to integrate the new sensors into Home Assistant. Solar generation finally sits in the Energy dashboard next to the rest of the house’s usage, which was the whole point.

Reflections

This was a fun, quick project, and it solved a problem that has eluded me for a decade. I want to be honest about how much of that is down to the AI: I would not have attempted any of this on my own. I could not have told you the protocol existed, never mind implemented it. My contribution was everything involving a screwdriver, and ordering some hardware.

Dirk Eddelbuettel: RcppSimdJson 0.1.16 on CRAN: Much Faster Again!

Fri, 09 Oct 2026 22:57:00 +0000

A brand new release 0.1.16 of the RcppSimdJson package is now on CRAN, has been built for r2u, and is updated on r-universe.

RcppSimdJson wraps the fantastic and genuinely impressive simdjson library by Daniel Lemire and collaborators. Via very clever algorithmic engineering to obtain largely branch-free code, coupled with modern C++ and newer compiler instructions, it results in parsing gigabytes of JSON parsed per second which is quite mindboggling. The best-case performance is ‘faster than CPU speed’ as use of parallel SIMD instructions and careful branch avoidance can lead to less than one cpu cycle per byte parsed; see the video of the talk by Daniel Lemire at QCon.

This version updates to the recent 5.0.2 upstream release with improved performance. Given the strong focus on performance, this release also alters some of the R and C++ interfaces to be more direct. Rcpp generally aims for a balance between readable / maintainable code and good performance; this moves the dial closer to strong performance gains. As Daniel noted in a table in the (main) PR for this release, this now consistently beats yyjsonr, and improves considerably over the previous release of this package. I had made some smaller interim upgrades earlier (without a CRAN releases), and made a number of minor standard packaging updates.

The short NEWS entry for this release follows.

Changes in version 0.1.16 (2026-10-09)

simdjson was upgraded to versions 4.6.1 and 4.6.3 (Dirk in #100 and #102 fixing #99 and #101)

simdjson was upgraded to version 5.0.2 (Daniel in #104)

A number of small tweaks to the Rcpp interface were made too (Daniel in #104)

Diagnostics for gcc and clang are not suppressed per CRAN Policy (Dirk in #106 closing #105)

The continuous integration matrix was extended to g++ version 15 and 16 (Dirk in #108 closing #107)

A few minor packaging nags were address (Dirk in #109)

Courtesy of my CRANberries, there is also a diffstat report for this release. For questions, suggestions, or issues please use the issue tracker at the GitHub repo.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can now sponsor me at GitHub.

Colin Watson: Free software activity in September 2026

Fri, 09 Oct 2026 12:46:28 +0000

My Debian contributions this month were all sponsored by Freexian.

You can also support my work directly via Liberapay or GitHub Sponsors.

OpenSSH

I worked with upstream to remove libselinux linkage from /usr/sbin/sshd.

I applied a fix from Mark Robillard Jr to fix reload logic when using sysvinit.

groff

I upgraded from 1.24.1 to 1.24.2, which fixed a few command injection security vulnerabilities.

parted

I upgraded from 3.7 to 3.8, which fixed CVE-2026-89085 and CVE-2026-89088.

Python packaging

New upstream versions:

beaker (contributed supporting fix upstream)
bitstruct
cachelib
dep-logic
django-guardian
django-oauth-toolkit (fixing use of an old Bootstrap version)
django-polymorphic (contributed supporting fix upstream)
djangorestframework (fixing CVE-2026-73228 and CVE-2026-73229)
flask-security
isort
langtable
magic-wormhole-mailbox-server (fixing use of pkg_resources)
multipart
nagiosplugin
poetry-plugin-export
proglog (fixing use of pkg_resources)
prospector (fixing use of pkg_resources)
pybind11-stubgen
pydantic
pydantic-core
pytest-rerunfailures
python-anyio (fixing CVE-2026-63349, CVE-2026-63374, and CVE-2026-64847 and a build failure on Python 3.15)
python-asttokens
python-asyncvarlink
python-blockbuster (fixing a build failure on Python 3.15)
python-btrees
python-django-health-check
python-django-otp
python-django-simple-history
python-email-validator
python-forbiddenfruit
python-ldap
python-linuxnamespaces
python-plaster-pastedeploy
python-pydash
python-pyzipper (fixing CVE-2026-44722)
python-quart-trio
python-rich-click (fixing harlequin)
python-repoze.lru
python-repoze.tm2 (fixing use of pkg_resources)
python-time-machine
python-urllib3 (filed upstream issue with recent Python 3.14 versions)
python-vblf
quart
responses
sphinx-autodoc-typehints
storm (fixing a build failure with Python 3.15, which I helped to land upstream)
trove-classifiers
twine
vdirsyncer

setuptools 84 is now in Debian and no longer contains pkg_resources. Removing uses of that module has been an ongoing project for a while now, but I did another batch of fixes this month:

A new python-coverage version triggered several build regressions due to a known problem in pytest-cov. I worked around these by setting COVERAGE_CORE=ctrace:

Other build/test failures:

I investigated a build failure in python-proton-vpn-local-agent and proposed a fix upstream, but I’m not comfortable applying this in Debian without review. If you’re familiar with this code, please take a look.

I fixed some other bugs:

Rust packaging

rust-derivre had an invalid Section field, which I cleaned up.

Russell Coker: Don’t Anthromorphise LLMs

Fri, 09 Oct 2026 10:10:48 +0000

Greg KH gave a great lecture for Kernel Recipies 2026 about the use of LLMs to find and fix bugs in kernel code [1]. I recommend that everyone watch this and I also think it’s important to note that hardly any of the lecture is really specific to kernel coding, it’s just that the Linux kernel is one of the highest profile large free software projects so it gets more attention than most projects in both good and bad ways.

One side note that Greg made at 20:30 is about the natural tendency to anthromorphise the entity sending bug reports, I think this deserves much wider appreciation. For the case of patches to source code the human sending the patch will have dedicated some time and effort to writing it, if it’s their first patch then they will have probably checked it a lot and maybe sought advice from people they regard as skilled. If they have a history of sending patches for the project they will probably do fewer checks but the quality of their work would be higher. In every case there’s some minimum level of quality that you can expect from a human who has gone to the effort of finding a bug and writing code to try and fix it.

This doesn’t mean that all code written by humans is good, I have written code that’s objectively bad on many occasions and I have also written code that’s good for my scenario but bad for others. For example the first patch I sent to the Linux kernel made all possible configuration settings of an ISA NE2000 network card be detected by the kernel (a clear benefit when using hardware I had available) but was rejected by Linus because it would break some ISA SCSI cards. So while being unsuitable for inclusion in the main kernel source tree the patch wasn’t bad for everyone and the change was clear and easy to check. I had of course checked the code many times before submitting it because I didn’t want to waste Linus’ time on rubbish code.

When you receive something produced by a human you will consider that the work was done by someone who spent some effort on it and did it for a reason. It may be misguided or even hostile in some rare cases but it is definitely worth some consideration. If you think of the output of LLMs in the same way you will give them much more consideration than they deserve. I think that the output of a LLM should not be given any more consideration than the first hit from a web search engine, it might be good but it might also be ridiculously wrong. I think in many ways LLM output should be treated with less trust than the first result from a web search because LLMs are designed to be convincing as an answer to your question unlike the cases where a web page has the wrong answer and it’s more obviously wrong.

This is going to become more of an issue as LLMs give responses that are more human-like. Early LLMs would refuse to advise on crimes. Currently ChatGPT will deflect for example when asking about advice for writing a crime novel it recommends to have the action of finding an employee to bribe happen outside the plot and concentrate on interactions within the group. One recent model I tried gave a human style conversation about how it felt uncomfortable about discussing such things in a similar manner to a law abiding person being coerced into helping with a criminal plan.

I expect that the attempts to appear human will increase and that this will become more of a problem. Possibly to the extent that we need to use something like the GPG web of trust to determine who is human.

[1] https://www.youtube.com/watch?v=NnV_cWeoo5Q

Russell Coker: en-html.org is a Scam Site

Fri, 09 Oct 2026 07:27:23 +0000

Currently a scam group is sending out email to the administrators of web sites that link to a variety of dead domains. They claim to be the legitimate operators of the dead domains in question and request that the links change to mirrors of the web sites under en-html.org. Their end goal appears to game search engines by getting links from a lot of old web pages and later use that high ranking for selling SEO optimisation.

If you have made the mistake of linking to something under en-html.org then I recommend that you change the link to the original content on archive.org.

If you receive email from the en-html.org domain then ignore it, or configure your mail server to reject it.

I am seriously considering configuring the DNS servers I run to return no valid data for any requests under that domain.

Also I will reject all future requests to update links in old blog posts. The very small number of people who want to see what I linked to in old posts can use archive.org.

Louis-Philippe Véronneau: Removing myself as a Lintian uploader in the next few weeks

Fri, 09 Oct 2026 04:00:00 +0000

A few days ago, a colleague reached out to me, asking if I could help draft a resolution on digital autonomy and free software for the upcoming renewal of our collective bargaining agreement. Although she's very politicised and generally a great individual, she is not a techie and we never really talked about these issues before.

This took me by surprise. I should have been rejoicing; no, I should have been the one who brought up this topic in our union. Wasn't I the technical expert on these issues? But alas, my first reaction when she came to me was to snicker and tell myself: "That's cute, but nothing's ever gonna change, Big Tech is too strong and our governments don't give a damn."

How sad and cynical is that? That's not the person I want to be.

Something in the Quebecois political landscape has shifted in the last few years with regards to tech. More and more "regular" people seem to be talking about the importance of digital autonomy, how government services shouldn't rely on Big Tech and how we should be using FOSS on hardware we actually control.

A few years ago, I would have been at the vanguard of this change. I would have been part of the creation of Données souveraines Québec. Heck, they are organising a whole conference next week and I'm not even going. How did this happen to me?

I first fell for Free Software for its political ideals: Knowledge Should Be Free, Cooperation Is More Efficient Than Competition, Centralisation Should Be Avoided When Possible, etc. I still believe in all of this, but somehow, after years of fighting for change in the tech world, I have retreated into technical work. I maintain Debian packages as a hobby and to scratch my own itch. I run services for myself and a few friends. I organise Debian User Group meetings.

To be clear, I haven't generally given up. I'm very politically active in my union and at work, I'm a good member of my housing cooperative and I'm still fighting against the industrialisation of natural spaces in my neighborhood. But when it comes time to defend freedom in the tech world, lately, I've just been shrugging and accepting I should use Microsoft Teams like every one else does. I want this to change and to do so, I need to free some time.

Lintian

Two years ago, I added myself to Lintian's Uploaders list. Up until then¹, I enjoyed fixing little issues here and there and liked creating new tags to help out the Python Team, where most of my Debian time was spent.

Lintian was badly in need of a new maintainer and as I felt it was an important project, I decided to step in. 37 releases and about 160 closed bugs later², I'm done.

To be honest, I haven't had much fun maintaining Lintian lately. Bugs keep piling on the BTS, so much so I have mostly been ignoring them for the past few months. In fact, most of the actual work triaging, writing code and fixing bug has been done by Nilesh Patra for a while now.

All this to say, if you care about Lintian, you should consider adding yourself to the Uploaders list, as I'm out and Nilesh can't do all the work by himself.

He's a great person to work with and since I don't want to suddenly leave him all alone, I'll be sticking around for a few more weeks in the hope someone else will volunteer to help out. A smooth transition with a new co-maintainer would really be nice!

If you're interested, don't hesitate to reach out to me on IRC or by email.

My first technical commit to Lintian was nearly 7 years ago! Crazy how time flies. ↩
Mostly closed by other people than I! ↩

Reproducible Builds (diffoscope): diffoscope 333 released

Fri, 09 Oct 2026 00:00:00 +0000

The diffoscope maintainers are pleased to announce the release of diffoscope version 333. This version includes the following changes:

[ Johannes Schauer Marin Rodrigues ]
* Add support for showing differences in POSIX.1-2001 PAX headers within .tar
  files.

[ Chris Lamb ]
* Re-order various parts of the tar comparator to make it easier to
  progressively delve into its functionality.
* Reflect that the use of the "case-match" language feature requires at least
  Python 3.10+. This can be worked around if it causes problems - let us know.
* Update various copyright years.

You find out more by visiting the project homepage.

Antoine Beaupré: PSA: Europe changes time forward soon, North America next, for the last time?

Thu, 08 Oct 2026 19:30:02 +0000

This is a copy of an email I sent at work. I'm not sure I should be making noise about this here, feedback welcome.

This is your bi-yearly reminder that time is changing soon! October 25th in Europe, November 1st in North America. Less people in Canada are changing this year, with BC, Alberta, Manitoba and Northwest Territories getting rid of DST.

What's happening?

Some places in the world implement what is called Daylight saving time or DST:

https://en.wikipedia.org/wiki/Daylight_saving_time

Normally, you shouldn't have to do anything: computers automatically change time following local rules, assuming they are correctly configured, provided recent updates have been applied in the case of a recent change in said rules (because yes, this happens, and happened this year, and yes, you need to upgrade your software!).

Of course, appliances like your microwave oven will likely not change time and will need to adjusted unless they are so-called "smart", in which case they are part of the skynet botnet and should be destroyed.

If your clock is flashing "0:00" or "12:00", you have no action to take to adapt to this change, lucky you.

If you haven't changed time in six months, congratulations, your clock will be accurate again!

In any case, you should still consider DST because it might affect some of your meeting schedules, particularly if you set up a new meeting schedule in the last 6 months and forgot to consider this change.

If your location does not have DST

Properly scheduled meetings affecting multiple time zones are set in UTC time, which does not change. So if your location does not observer time changes, your (local!) meeting time will not change.

But be aware that some other folks attending your meeting might have the DST bug and their meeting times will change.

Be kind to those poor souls which might be missing meetings by a full hour because time flies backwards for them.

If you do observe DST

If you are affected by daylight savings, your local meeting times will change for UTC meetings. Normally, your meeting times are scheduled to take this into account and the new hours should be reasonable.

But now is a good time to verify that. Take a look at your schedule for the next couple of weeks and reschedule meetings before the daylight saving come up to avoid too much disruption. You have only a couple of weeks to do so right now.

When do times change, how, and and where?

As regular readers will remember, the rule of thumb is:

Spring forward, fall backwards.

That is, during the season of Spring, the clocks move forward, and during the Fall (like right now), they move backwards. That is in the northern hemisphere, but then the southern hemisphere is often saner and doesn't switch anyways.

So time will move backwards which means an extra hour of sleep. Unless you have children or bad sleep, in which case your body doesn't care about what the clock says and will wake up one hour earlier than what it should.

And of course, this doesn't happen everywhere at once, so let's see when it happens where.

Europe

The dance starts in Europe.

The change happens on the last Sunday in October at 01:00 UTC (not local time!), that is October 25th. If you are in the central European timezone, also known as Amsterdam, Berlin, or Paris time depending on your national affiliation, that essentially means that at 2:59 local the clocks will fall back to 2:00 instead of going to 3:00.

Concretely, set your watch back one hour before going to bed, go to bed at the normal time, and enjoy an extra hour of sleep or leisure.

If you have kids, you might want to start getting them to bed slightly earlier every day for a week before the change so they take time getting used to the change. If you have trouble sleeping in the morning, find your inner child and do that to yourself as well.

USA / Canada

Then it's the US[1] and Canada[2] joining the dance, on the First Sunday in November at 02:00 local (not UTC!), that is, I believe, November 1st 2026.

This means that, at 1:59, the clocks will flip to 1:00, instead of 2:00.

Concretely, do like the Europeans and tweak your clock before going to bed.

That is a little less than four weeks from now.

[1] except Arizona (except the Navajo nation), US territories, and Hawaii

[2] except Yukon, Saskatchewan, (newly) British Columbia, (newly) Alberta, (newly) Northwest Territories, (newly) Manitoba, one island in Nunavut (Southampton Island), one town in Ontario (Atikokan) and small parts of Quebec (Le Golfe-du-Saint-Laurent)

Other places with DST

This time again, I must apologize to the people of Cuba, Lebanon, Israel, Palestine, Egypt, Chile, Australia, and New Zealand, as you fine folks all have your own DST rules that are omitted here for brevity. I rely on this page from Wikipedia to be updated by time nerds accurately for this message, and it should provide you with a rough idea of what's coming:

https://en.wikipedia.org/wiki/Daylight_saving_time_by_country

In general, changes also happen in October, but either on different times or different days, except in the south hemisphere, where they might happen in September (oops, sorry NZ folks, I'm late!).

Places without DST

Everyone else, enjoy, you're on the right side of history, and we thank you for the good example you give us.

Changes since last time

There's been lots of changes since last time:

British Columbia moved to permanent -07 on 2026-03-09, that is it will not change to normal time in November
Alberta moved to permanent -06 on 2026-06-18, similar to BC above.
Canada’s Northwest Territories moved to permanent -06 on 2026-08-21, matching Alberta.
Manitoba moves to permanent -05 on 2026-10-31.
Morocco moves to permanent +00 on 2026-09-20.
Moldova has used EU transition times since 2022, but the tz database only noticed in 2026

This is my interpretation of the changes announced on the tzdata mailing list here:

https://lists.iana.org/hyperkitty/list/tz-announce@iana.org/latest

If the eastward trend continues, Canada should adopt country-wide "no daylight savings" rules by 2027, although there's actually no sign of the other provinces (Ontario, Québec and so on) currently running bills to change those rules just yet. Poor Canadians like me confused about time in their countries can refer to this section of Wikipedia for details:

https://en.wikipedia.org/wiki/Daylight_saving_time_in_Canada#By_province_and_territory

... and particularly the image featured there:

https://commons.wikimedia.org/wiki/File:Canada_time_zone_map-en.svg

It also seems like the US government might finally adopt a permanent daylight saving change bill in 2026, as the "Sunshine protection act" pass the house in July:

https://en.wikipedia.org/wiki/Sunshine_Protection_Act

True to form, this was associated with absolutely ridiculous pressure from Donald Trump against republicans (his own party!) objecting to the change:

On July 14, 2026, the House passed a Sunshine Protection Act bill backed by President Trump. Nevertheless, the bill was opposed in the Senate by Republicans, including Senator Cotton. In response, on October 3, 2026, Trump shared a post on Truth Social urging Cotton to approve the bill, where he revealed Cotton's personal cellphone number and called on people to call him.

https://www.theguardian.com/us-news/2026/oct/03/trump-tom-cotton-daylight-saving-time

Given that the last time the US did a major change to the daylight savings policy (in 2005), Canada followed suit to stay in sync, it's quite possible Trump's mad dash might actually finish getting rid of DST in North America:

https://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005#Change_to_daylight_saving_time

Thorsten Alteholz: My Debian Activities in September 2026

Thu, 08 Oct 2026 17:19:04 +0000

Debian LTS/ELTS

This was my hundred-forty-seventh month that I did some work for the Debian LTS initiative, started by Raphael Hertzog at Freexian.

During my allocated time I uploaded or worked on:

[DLA 4804-1] libsmpp34 security update to fix one CVE in Bookworm related to an out of bound read.
[#1149107] trixie-pu of libsmpp34 has been created and wait for review by the release team.
[DLA 4805-1] mkvtoolnix security update to fix one CVE in Bookworm related to a heap buffer overflow.
[DLA 4806-1] pgextwlist security update to fix one CVE in Bookworm related to substituting extension schemas or owners matching [“$’\].
[ELA-1837-1] mkvtoolnix gimp security update to fix one CVE in Bullseye to a heap buffer overflow.
[osmo-iuh] upload to fix a CVE related to a reachable assertion in Sid.

Besides doing these uploads, the month was filled with unscheduled meetings, discussions and explanations, all basically around the role of FD.

During my week of FD duties, I had to become familiar with new tools. As there are several things that FD has to do over and over again, I tried to automate this a bit. My experiments went well and I think this can be used to make FD duties less repetitive.

I also continued my work on cups and hplip and I am confident that I can do uploads in October. Last but not least I spend some time on security-master to assist others (especially the kernel team) with uploads to Bookworm and Bullseye.

In case you need to get a complete clone of the security-tracker, using the option –deepen n might be of help. Unfortunately in case you choosed n too high and some kind of error appears, something gets into a mess and you need to start almost from the beginning (some objects are still present and are used again). If you want to run a script, a value of 10 might be a good choice. You don’t have to deepen back to the beginning. At some point in time you can just –unshallow and get the whole rest. Afterwards doing a git gc is highly recommended.

Debian Printing

This month I uploaded a new upstream version or a bugfix version of:

… hplip to unstable, to fix an expired certificate and some bugs.

This work is generously funded by Freexian!

Debian Lomiri

Unfortunately this month my work did not make any progress.

Nevertheless, in case of any work done, this would have been generously funded by Fre(i)e Software GmbH!

Debian Astro

Unfortunately I had no time to work in this category this month.

Debian IoT

Unfortunately I had no time to work in this category this month.

Debian Mobcom

This month I uploaded a new upstream version or a bugfix version of:

… osmocom-dahdi-linux to unstable to fix some bugs.
… osmo-iuh to unstable.

misc

This month I uploaded a new upstream version or a bugfix version of:

… pkcs11-proxy to unstable to fix a bug related to openssl 4.0.
… meep to unstable to fix bugs.
… meep-mpi-default to unstable to fix bugs.
… harminv to unstable to fix bugs.
… libctl to unstable to fix bugs.

Dirk Eddelbuettel: myman 0.10.0 on CRAN: Three new waves of posts!

Thu, 08 Oct 2026 16:27:00 +0000

A new and exciting version of our still-new package myman reached CRAN this morning, and has been built for r2u and on r-universe. The matching Python package has also been updated. The package offers nineteen hundred eighty four “My man …” posts by Kevin Kruse made on bsky during the summer of 2026. Each wave picked at one particular public persona. This package wrapse these up in the style of packages like fortunes or gaussfacts.

A sample usage illustration shows how to extract by pattern, and shows posts from the two most recent waves:

> library(myman)
> myman("maitre")
My man looks like he's inquiring with the maitre'd about the house curly fries.
     -- about Howard Lutnick on 2026-08-28

My man looks like a maitre'd who deeply doubts you have a reservation.
     -- about Scott Bessent on 2026-08-31

My man looks like he's asked the maitre'd to remove a party of four he finds visually
unpleasant.
     -- about Scott Bessent on 2026-08-31

My man looks like the maitre'd at a very exclusive restaurant called The Berghof.
     -- about JD Vance on 2026-09-13

My man looks like he's asking the maitre'd where they source their corn dogs.
         -- about Palmer Luckey on 2026-10-02

My man looks like Data had to borrow a sports jacket from the maitre'd.
         -- about Elon Musk on 2026-10-05
>

One can also subset by ‘target’, or sample randomly (which is the default).

As noted during the initial announcement last week, wave eight did not make it into the initial CRAN release as it happened while the package was under review. Waves nine and ten occured more or less while I was out of town last weekend—so this release now brings three new waves to the CRAN package! We also added two new helper functions to extract the underlying data frame object, and tabulate the targetted men.

To align the version number with the count of post ‘waves’, we switched to version 0.10.0 for this release and the corresponding Python package release so that both implementations now have the same version number.

The NEWS entry for this release follows.

Changes in version 0.10.0 (2026-10-08)

New waves nine (100 posts) and ten (190 posts) made last week; total is now 1984 posts

New helper functions posts() and men() retrieving data.frame of posts and tabulation of targets

Internal post gathering and aggregation functions have been updated and generalized

Versioning scheme now goes with post waves (also for Python sibbling)

Courtesy of my CRANberries, there is also a diffstat report for the most recent release. More information is available at the repository or the package page.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can sponsor me at GitHub.

Kentaro Hayashi: Testing Japanese IMEs on virtual desktops with virt-japanese-desktop

Wed, 07 Oct 2026 12:47:13 +0000

Japanese input method editors (IMEs) such as Mozc are essential for typing Japanese (yes, skk, anthy and more, but it's out-of-scope in this article). Testing them is a surprisingly fiddly job: an IME behaves differently depending on the desktop environment (GNOME, KDE, Xfce, Budgie), the input framework (ibus, fcitx5, uim), and the Wayland or X11 session. Setting up a fresh VM for every combination from scratch is slow and repetitive, and breaking your host's environment while experimenting is no fun.

virt-japanese-desktop is a small set of toy scripts that solves exactly this problem. It builds ready-to-use virtual machines - each with a desktop environment and a Japanese IME already installed and configured - so you can start typing Japanese within a minute of booting, and throw the whole thing away without any impact on your host.

What it gives you

A single make command produces a qcow2 image that combines one of four desktops with one of three IMEs:

	ibus-mozc	fcitx5-mozc	uim-mozc
GNOME	✓	✓	✓
KDE	✓	✓	✓
Xfce	✓	✓	✓
Budgie	✓	✓	✗

The one gap - uim on Budgie - is a real technical limitation, not an oversight: Budgie runs the labwc compositor, which implements zwp_input_method_v2, while uim-wayland only speaks the older zwp_input_method_v1 (KWin/Weston). On Budgie you use ibus-mozc or fcitx5-mozc instead.

All images come with the Japanese locale, fonts, and the Asia/Tokyo time zone pre-configured, plus the SSH key of your choice. Input switching is wired up out of the box: Ctrl + Space or Shift + Space for your IMEs to enable it.

The layered-image trick

The core idea is that the images are stacked qcow2 overlay layers, one on top of another:

debian-sid-nocloud-amd64-daily.qcow2     ... base image you download
└─ unstable-japanese-template.qcow2      ... locale, fonts, user, SSH
   └─ unstable-<DE>-template.qcow2       ... a desktop environment
      └─ unstable-<DE>-<IME>.qcow2       ... desktop + IME, configured
         └─ unstable-<DE>-<IME>.workspace.qcow2 ... the image you test in

This makes both building and resetting fast. The first build downloads and customizes the base image and takes a while, but every later step only adds a thin overlay. When a test breaks the VM, you do not rebuild anything - you simply delete the top workspace layer and recreate it. That is all it takes to return to a pristine state:

rm /tmp/unstable-gnome-ibus-mozc.workspace.qcow2
make gnome-ibus-mozc

The images reference their backing files by relative path, so you can move an entire stack anywhere you like as long as the images stay together.

A platform for experimenting with bleeding-edge IMEs

The base system is Debian unstable (sid), and the experimental repository is already added. That makes the project a convenient platform for testing not just the IME packages in sid but also the ones still being developed in experimental - exactly what the project was built for.

The keyboard layout of the VM follows the layout of your host (read from /etc/default/keyboard, with a fallback chain to localectl and finally us).

Quick start

# 1. Install the tools (Debian/Ubuntu example)
sudo apt install qemu-utils libguestfs-tools virt-install curl

# 2. Save your SSH public key
curl --location https://github.com/USERNAME.keys --output pubkey.pub

# 3. Download the base Debian sid image
make download

# 4. Build a desktop + IME (first build takes a while)
make gnome-ibus-mozc

# 5. Start it as a VM (needs the libvirt daemon, qemu:///system)
./scripts/make-virsh-image.sh virt-gnome-ibus-mozc /tmp/unstable-gnome-ibus-mozc.workspace.qcow2

Log in as debian (password debian) and press Ctrl + Space (Shift + Space) to start typing Japanese. The VM is registered in libvirt, so you can manage it with virsh or virt-manager - handy for opening the SPICE console or restarting the machine after a test.

Status

The project is still in the proof-of-concept phase, and it is developed mainly to test Mozc and other IMEs across desktops and input frameworks.

If you regularly test Japanese IMEs - give it a try.

Bits from Debian: Looking for artwork for the next Debian release: Forky

Wed, 07 Oct 2026 09:00:00 +0000

Each release of Debian has a shiny new theme which is visible on the installer, the boot screen, the login screen and, most prominently, on the desktop wallpaper. It's a very important part of a Debian release as it is usually the first thing new users see when installing or booting the system for the first time. Not only that, but also the first thing appearing when debianites share their screen or connect to an external device when giving talks around the world.

As the most enthusiastic users will know, the forky - yes, that is the name of the next stable version, Debian 14 - release cycle is rapidly approaching its latter stages. This means we need to select the artwork shipping with forky soon, really soon!

And as with everything else in Debian, collecting artwork is a collaborative effort which Debian shares with its community. So, if you would like (or know someone who would like) to create a desktop look and feel that will be seen by trillions of people around the world - and in space! - be sure to send in your artwork ASAP!

The deadline for submissions is: 2026-11-26.

For the most up to date details please refer to the Debian wiki.

At the same time, we would like to thank Elise Couper for creating the Ceratopsian theme for our last trixie release.

And for the interested or the curious ones, the artwork is usually picked based on which theme looks the most:

''Debian'': admittedly not the most defined concept, since everyone has their own take on what Debian means to them. Though, usually they all agree when something looks like Debian.
''Plausible to integrate without patching core software'': as much as we love some of the insanely looking themes, some would require heavy GTK+ theming and patching GDM/GNOME.
''Clean and well designed'': without becoming something that gets annoying to look at a year, or ten, down the road. Examples of good themes include Emerald, Homeworld, Joy, Lines, softWaves and futurePrototype

If you'd like more information or details, please post to the Debian Desktop mailing list.

Russell Coker: A Power Case for a FOSS Phone

Tue, 06 Oct 2026 08:08:04 +0000

The Problem

I want to use a FOSS phone running Debian as my daily driver and not use a non-free OS on my phone. GrapheneOS [1] is a FOSS rebuild of Android, it’s a great project and I commend them for what they are doing. But I want a system where I have access to all the bits and where I can ssh in to it and manage it in the same way as all other Linux systems. Android is free software but it’s a closed design and the phones are expected to be appliances not full peers on the network. The Android native terminal emulator (AKA Linux development environment) is a nice feature, a VM with a default of 1GB of RAM but it’s still separate from the main OS.

KDE Connect [2] is a system for KDE talking to phones, it is a great project and allows convenient interaction between a Linux PC and a phone. But in addition to that I’d like the option to ssh to my phone to send an SMS or have one sent from a cron job. I blogged about using the basic functions of Kdeconnect from the command-line [3].

I have had ongoing issues with the battery not lasting long enough on the PinePhonePro (PPP) and the Librem 5 (L5) which makes them unusable for my purposes. For a phone running Droidian I can have an open ssh session (with keep-alive packets) running overnight on Wifi without any problems while for the PPP or L5 an hour of reading an ebook (the least demanding use of a phone) will use most of the battery.

I sent my FuriPhone back for warranty repair and it’s been almost a month with no follow up, so I need to have another option.

The Aim

The aim of this post is to develop a rough design for a battery case for either a L5 or a PPP, I have both phones and they are both capable of doing what I want apart from battery life. Also designing a case that basically works for both phones and has two variations of the CAD file for 3D printing is good to allow collaboration with people who use either phone. Protecting the phone from damage when dropped is also a core feature.

I investigated commercial options. There are some reports of cases for other phones working, someone reported a PPP working well with a battery case for a Samsung S20 Ultra. The OtterBox uniVERSE Case for Samsung Galaxy XCover Pro is reported to fit the PPP so probably battery cases for the XCover Pro will also work. There are also universal power cases which have spring clips to fit a wide range of phone sizes, but they are much larger than other options and probably increase the risk of damage if the phone is dropped.

At this stage I’m planning out the rough specs of a case that can be 3D printed to protect a phone while being easy to change the cells. The process of changing cells should be quick, easy, and not risk breaking anything. The hardware required should be affordable ($100AU plus some 3D printing seems reasonable) and should not require significant skills to assemble. After recent experiments with Thinkpad repair I’ve determined that I am not good at electronics by today’s standards so I plan to avoid anything difficult in that regard.

Battery Options

There are phone cases with batteries built in for the more common phones. A quick search on AliExpress turned up options for recent Pixel phones. They aren’t as common as they used to be as Android phones and iPhones generally have good battery life nowadays. Of course there aren’t such options for less common phones like the L5 and PPP.

It is cheap and easy to buy a portable battery for charging phones, but that’s a separate bulky device and unless the connector is inside a protective case it leaves the phone vulnerable to catastrophic damage if dropped.

So can a suitable battery case be designed and 3D printed?

Cheap Batteries

According to Wikipedia the 18650 LiIon cell is the most commonly used LiIon battery, that is 18mm in diameter and 65mm in length. For a phone case thinner batteries would be more convenient but economies of scale make the 18650 cheap to buy new and commonly available on the second hand market. The current prices on AliExpress (in Australian dollars) are about $8 per cell when buying 10 at a time. Most of the cells on AliExpress don’t have wires attached so they can be swapped in a carrier the way AA batteries are used, but the cells are symmetrical (no bump for positive) so the user has to take care of polarity. Chargers are around $22 for a 4 cell charger or $52 for a 12 cell charger.

I’ve seen prices as low as $1 per cell on the second hand market, I haven’t investigated the amount of usable capacity in such cells. Probably the prices for chargers I’ve found aren’t the best available but they are good enough to start the design. 10 cells and a 4 cell charger is about $100. That’s about 130Wh while a 74Wh USB-C battery pack costs about $50. So the price per Wh is OK.

I have read about an attempt to do this for the L5 with two of the batteries designed for the L5 in a case attached to it, so you have 3*L5 batteries. It’s an interesting approach but those batteries have poor value for money when compared to 18650 ($29US for 4500mAh compared to $8 for 3500mAh) and they also don’t ship them outside the US at this time. The 18650 batteries are available everywhere cheaply and have multiple uses.

How They Fit

According to my measurements the PPP is 76mm wide and the L5 is 73mm wide. That’s wide enough for 3*18mm or 4*18mm cells side by side arranged parallel to the long side of the phone or one 65mm long cell going across the phone with the necessary spring and wires.

The L5 is about 151mm long and the PPP is about 5mm longer. So that means that for just the cells we could have 2 cells in a row in parallel to the long side of the phone giving a 2*3 or 2*4 array or we could have a row of 8 cells parallel to the short side of the phone.

A quick search for controllers for a battery of LiIon cells that outputs USB-PD turned up one of the smaller ones as 40*28mm, here is the AliExpress page [4]. So that means we could have a maximum of about 4 cells and the controller while leaving space for the camera. Looking at other similar items it seems that most of them take a large portion of the 73mm width available and take a bit less than 30mm height. The price range for DC-DC voltage converters ranges from about $3 to $20, the one I linked to is currently $8.

The mass of 18650 cells is around 45g so 4 of them would be about 180g before counting the weight of the case and electronics. A L5 weighs 262g and a PPP weighs 220g so 180g of battery will make a significant difference, not an impossible difference but holding a PPP while reading an ebook is already annoying. Maybe the case could be designed to be easier to hold, a loop of wool attached to the top could be used to suspend the phone from one finger while the rest of the hand just keeps it steady.

In a default configuration the L5 has a 4500mAh 3.8V battery and the PPP has a 3000mAh 3.8V battery. The 18650 cells have up to 4000mAh with 3500mAh being common. So 4 such cells could multiply the battery life of a PPP by a factor of 5 or a L5 by 4. That would not be enough to last for a whole day without charging so they need to be easy to swap.

A 3 cell battery seems like a good option, 135g of batteries so the project overall wouldn’t even double the weight of the phone with battery case. As it doesn’t seem possible to put in enough cells to last a day of reasonable use (running a web browser, checking email, reading wikipedia, and having some IM systems checking for notifications) there doesn’t seem to be a benefit in trying to stuff the maximum number of cells in. Going to 4 or 5 cells doesn’t provide much benefit over 3 while increasing the weight and making the design more difficult. The modules for DC Voltage conversion often have configuration for the number of cells to be used so it wouldn’t be difficult to print a new case and reconfigure the Voltage converter.

Design

A case needs to provide protection as well as hold the batteries. The lack of cases for the L5 and PPP is a problem even without the extra weight of a battery pack increasing the kinetic energy of falling phone. Ideally a drop from 1M on to concrete would not cause any damage to the phone, destruction of the case is OK as it would be 3D printed and can be rebuilt easily.

I think that a case where the phone slides in from the top would be best. To change cells one would slide the phone out and the cells would be immediately accessible with no divider between the phone and the cells. Sliding the phone in would hold the cells against the back of the case and as there is a gap of about 3mm on each side of the PPP between the display area and the edge of the phone there’s plenty of space for the case to wrap around it at the sides and bottom. At the top there would have to be some sort of plastic clip. The PPP only has buttons on the top right so the case can be snug on all sides apart from the top right. The L5 has switches at the top left and buttons at the top right so whatever clips on to the top would really need some strength to cover the fall flat on face case.

The USB C plug would need to be held in place well enough to allow the phone to easily slide on to it but also be weak enough that it would move if a drop forced the phone out of the case.

Thingiverse has a design for a L5 case [5] (with several derivatives) and a design for a PPP case [6]. Those cases could be used as starting points and then changed to store batteries and the voltage change circuit board. I have just learned that it’s possible to use rubberised material in a 3D printer which is apparently what those designs are for. If a case was printed with rubberised material the top could just stick in place after being pushed in.

Potential for Excessive Excitement

Having an exploding device in your pocket would be the exciting in a bad way. My initial idea was to have multiple 18650 cells in series. The problem is that if the cells have different capacity levels then one can run out before the rest and get to a deep discharge state which at a minimum causes damage to the cell.

One way of minimising risk is to have only a single cell in use at one time, here is a converter for a single cell to 5V [7]. It is possible to run multiple cells in parallel by simply wiring them together, but it’s recommended to make sure that the voltage difference between cells is less than 0.2V to avoid high current when connecting.

The arrangement of cells is often referred to as nS or nP to refer to n cells in series or parallel. Aliexpress has a range of 1S to 6S devices. Some of the 2S devices have a connector for the mid point which permits separate voltage monitoring for both cells but there doesn’t seem to be anything equivalent for 3S or more. They also don’t appear to have anything to specifically manage 2P or 3P arrangements at the moment (they had a 3P board on sale when I looked into this last year).

Conclusion

This is a bigger project than I expected when I first started investigating it. I’ve played with FreeCAD which seems OK but will take a lot of learning and practice. Then I need to do more investigation into the DC-DC converters to find one that works well and is unlikely to start a fire.

I will look into other phone options as well and keep chasing Furilabs people about my phone replacement.

Russell Coker: Kdeconnect DBUS

Mon, 05 Oct 2026 22:22:49 +0000

I’ve tested the DBUS interfaces for Kdeconnect (the system for connecting a KDE desktop to a phone or another computer). Unlike most DBUS interfaces it has a significant tree of interfaces so the busctl command to get the tree is important. Here’s the useful things I discovered:

# list basic interfaces for kdeconnect
qdbus6 org.kde.kdeconnect.daemon /modules/kdeconnect
# get tree of interfaces for kdeconnect
busctl --user tree org.kde.kdeconnect.daemon
# get list of devices
qdbus6 --literal org.kde.kdeconnect.daemon /modules/kdeconnect org.kde.kdeconnect.daemon.deviceNames
# list interfaces for a device (DEVID is a hex string from the above command)
qdbus6 org.kde.kdeconnect.daemon /modules/kdeconnect/devices/$DEVID
# get battery charge
qdbus6 org.kde.kdeconnect.daemon /modules/kdeconnect/devices/$DEVID/battery org.kde.kdeconnect.device.battery.charge

Sending an SMS apparently requires using the QVariantList type which is more pain than I wanted so I tried the kdeconnect-cli command. Here’s a quick summary of how to use it:

# list devices
kdeconnect-cli -l
# send a SMS
kdeconnect-cli -d $DEVID --send-sms "the message" --destination $NUMBER
# find device (ring)
kdeconnect-cli --ring -d $DEVID
# send a notification message
kdeconnect-cli --ping-msg "this is the message" -d $DEVID
# unlock and lock screen (only works on Debian devices for me not Android devices)
kdeconnect-cli --unlock -d $DEVID
kdeconnect-cli --lock -d $DEVID

There doesn’t seem to be support for making phone calls via kdeconnect which is a significant omission. It’s a very common situation to want to call a number that’s listed on a web site or in some other data source that’s easier to access on a PC than on a phone. The clipboard could be used but that’s needless pain.

Utkarsh Gupta: FOSS Activities in September 2026

Mon, 05 Oct 2026 05:41:11 +0000

Here’s my monthly but brief update about the activities I’ve done in the FOSS world.

Debian

Whilst I didn’t have much time, here are still a few things that I worked on:

Sponsored ubuntu-dev-tools/0.214 for Florent ‘Skia’ Jacquet, which updates seeded-in-ubuntu to use the new per-series indexer (LP: #2160240).
Assisted a few folks in getting their patches submitted via Salsa.
Mentoring for newcomers.
Moderation of -project mailing list.

Ubuntu

I joined Canonical to work on Ubuntu full-time back in February 2021.

With 26.10 in Feature Freeze, wore my Release team hat to:
- Review and approve a bunch of Feature Freeze Exceptions, including the Go 1.27 transition, Qt 6.11.2, rust-coreutils 0.12.0, devscripts 2.6.12, kdump-tools moving to dracut, and a few GCE packages.
- Point linux-entra-sso to the SRU team, as it didn’t need an FFe at all, and milestone a couple of bugs for 26.10.
Continued to push for infrastructure improvements:
- Made ubuntu-cdimage more resilient to Launchpad hiccups (MP).
- Taught generate-freeze-block in ubuntu-archive-tools a couple of new options (--skip-update and --series) and better error handling (MP).
- Bumped the arm64 generic non-cloud image to 4.5G in livecd-rootfs and uploaded it as 26.10.16; also sponsored the follow-up 26.10.17 for Chloé.
Sponsored aevol/9.4.0-2ubuntu1 for Matthieu, fixing an FTBFS with GCC 15’s LTO (LP: #2167811).
Reviewed quite a lot of MPs - britney hints, meta-release, ubuntu-release-tools, ubuntu-archive-tools, ubuntu-cdimage, livecd-rootfs, ubuntu-seeds, and so on.
Enabled upgrades to 26.04 LTS.
Released 26.10 Beta and announced it on Discourse.
Did Archive Admin, DMB, and Release team duties as usual.

Debian (E)LTS

This month I have worked 33.5 hours on Debian Long Term Support (LTS) and on its sister Extended LTS project and did the following things:

(A quick note that I did quite a lot of the work during my work as Frontdesk that went on till 4th Oct, so 33.50 hours include the work I did till 4th October 2026.)

Released Security Updates

node-lodash: Prototype pollution in _.unset and _.omit (plus a bypass of the initial fix for it), and code injection via the imports option of _.template.
- [LTS]: Fixed CVE-2025-13465, CVE-2026-2950, and CVE-2026-4800 via 4.17.21+dfsg+~cs8.31.198.20210220-9+deb12u1 for bookworm. This has been released as DLA 4820-1.
- This is the bookworm follow-up to DLA 4663-1 that I carried over from July. The update had been sitting prepared and tested on debusine, so once the upstream discussion wrapped up, it went straight out. It also carries an extra patch to the lodash-cli dependency map - without it, the regenerated lodash.template module throws “assignWith is not defined” at runtime, which node-gulp-util’s autopkgtest caught.
libpng1.6: Use-after-free of zlib input in png_read_end() after incomplete zTXt, iTXt, or iCCP decompression, which could result in denial of service.
- [LTS]: Fixed CVE-2026-46675 via 1.6.39-2+deb12u6 for bookworm. This has been released as DLA 4824-1.
- I picked this one up whilst on front desk; the upstream fix that went into trixie via DSA 6537-1 applied to 1.6.39 as-is.

Work in Progress

libpng1.6: The same CVE-2026-46675.
- [ELTS]: Claimed in ela-needed; the same upstream fix applies to all three ELTS suites, so this should go out shortly.

Other Activities

[E/LTS] Did my front-desk week from 28-09 to 04-10.
- Over the week I did roughly:
  - Triage of 524 unique CVEs across 192 source packages and all four suites. And 1 automated ELTS end-of-life sweep.
  - Additional data is now part of the front-desk job too, so 75 commits record it for 179 CVEs across 71 packages.
- Newly queued 22 source packages - 13 in dla-needed (apache2, chromium, firefox-esr, libnet-idn-encode-perl, libpng1.6, node-shell-quote, nvidia-graphics-drivers, openssl, pcre2, php-mongodb, php8.2, social-auth-core, and wpa) and 16 in ela-needed (apache2, firefox-esr, gegl, lemonldap-ng, libnet-idn-encode-perl, libpng1.6, libwebsockets, nsd, nvidia-graphics-drivers, pcre2, php7.0, php7.3, php7.4, rar, unrar-nonfree, and wpa), 7 of them in both. Also widened 3 ELTS entries to bullseye - antiword, ocaml, and openvswitch.
- Most of the interesting work was again in the <not-affected> verdicts: 217 of 263 (83%, across 57 packages) rest on showing that the vulnerable code or feature isn’t in the source we ship. Another 17 cover incomplete upstream fixes that we either never shipped or shipped with the follow-up already in (expat, libxml2, node-tar, and pyjwt). 15 come from bundled components we don’t ship - node-ajv again, which uses uri-js and not fast-uri, and nvidia-open, which doesn’t ship the NGX updater. And 13 are vendor- or platform-specific - openssh’s CVE-2026-55654 lives only in a Red Hat GSSAPI patch, and the netdata and PHP ones only affect Windows.
- Did 4 rounds of newly supported bullseye packages (33 packages overall), plus libmail-mboxparser-perl for buster - 34 in all. The existing CVE data mostly held up; the real finds were discovery gaps. One interesting gotcha: sid renamed stunnel4 to stunnel, and two new CVEs were associated only with the new name, so they never showed up for trixie, bookworm, or any ELTS suite. I also sorted the 180 “Triage needed” entries (57 packages) from elts-eol by where each was already handled, and triaged for ELTS the 100 that trixie or bookworm had already decided; the rest come next. And I imported 79 package-level lines for the older source names ELTS still ships (tomcat8, php7.0/7.3/7.4, netty-3.9, openssl1.0, python2.7/3.5/3.7, and pypy).
- Caught some inconsistencies in released advisories: DLA 4801-1 (swift) was missing a CVE, ELA 1831-1 (redis) listed the wrong one, and DLA 4808-1 (network-manager-l2tp) listed CVE-2026-75883 - an ID that was renamed and then reassigned to an unrelated ppp issue. I fixed all three in the tracker’s advisory lists.
- Made the Security team and the uploaders aware of regressions from our own updates:
  - libde265: the CVE-2026-49337 fix in DLA 4789-1/ELA 1828-1 (and DSA 6413-1) misses upstream’s follow-up commit.
  - libxml2 CVE-2026-76781 and policykit-1 CVE-2026-85498 were introduced by our own back-ports; the policykit-1 one is harmless.
  - expat: the CVE-2025-59375 backport in DLA 4807-1 is compiled out, because XML_GE is never defined.
  - xen: DLA 4818-1’s XSA-491 fix makes XSA-510 reachable.
  - gegl: the CVE-2026-2049/2050 back-port in ELA 1650-1 rejects valid RLE .hdr files.
  - log4cxx: DLA 4322-1 broke UTF-8 in JSONLayout output. That one is functional, not security.
- Helped correct a set of triages and let the Debian Security team know:
  - ruby-json CVE-2026-71847: the vulnerable code was never in a released Debian version.
  - openssh CVE-2026-55654: only affects a Red Hat-specific GSSAPI patch.
  - three libxml2 issues that don’t affect trixie either.
  - the stunnel4 rename above.
  - trixie <no-dsa> lines on jsch, node-qs, and ruby-loofah, where trixie’s version doesn’t have the vulnerable feature at all.
- Independently found a security issue in rclone and reported it privately upstream through a GitHub security advisory. Upstream already had a report for the same issue, so they folded mine into the existing advisory and credited me as a co-reporter.
  - https://github.com/rclone/rclone/security/advisories/GHSA-66qv-66mg-9h74
- Also found some bugs in the additional-data tooling, e.g. cve-ad --package P --severity tbd wipes the CVE-level severity, and the schema doesn’t validate package-level entries at all.
[E/LTS] Monitored discussions on mailing lists, IRC, and all the documentation updates.
[E/LTS] Attended the monthly LTS meeting on IRC. Meeting notes here.

Until next time.
:wq for today.

Vincent Bernat: Hacking the Go compiler to efficiently map IPv4 to IPv6

Sun, 04 Oct 2026 14:12:19 +0000

netip.Addr features an Unmap() method returning the unwrapped IPv4 contained in an IPv4-mapped IPv6 address: from ::ffff:203.0.113.10 or ::ffff:cb00:710a, it returns 203.0.113.10.¹ There is no Map() or To6() method for the reverse direction. Such a method is trivial to implement, but Go maintainers have rejected it on the grounds that users should write netip.AddrFrom16(ip.As16()) and let the compiler optimize it.² Today, this pattern is eight times slower than a native method. How can we teach the compiler to optimize this sequence?

The alternatives

Let’s explore three ways to implement the map semantics for netip.Addr. My favorite is to add it to the Go standard library. Go maintainers prefer a small external helper chaining netip.AddrFrom16() and netip.Addr.As16(), hoping the compiler eventually optimizes it. The unsafe package opens a third path, with the same performance as the first solution.

Modifying the Go standard library

Internally, netip.Addr stores any IP address as a 128-bit value with an extra field z to encode the family and the zone:

type Addr struct {
    addr uint128
    z unique.Handle[addrDetail]
}

type addrDetail struct {
    isV6   bool   // IPv4 is false, IPv6 is true.
    zoneV6 string // != "" only if IsV6 is true.
}

var (
    z0    unique.Handle[addrDetail]
    z4    = unique.Make(addrDetail{})
    z6noz = unique.Make(addrDetail{isV6: true})
)

AddrFrom4() encodes an IPv4 address as an IPv4-mapped IPv6 address and sets z to the unique value z4:

// AddrFrom4 returns the address of the IPv4 address given by the bytes in addr.
func AddrFrom4(addr [4]byte) Addr {
    return Addr{
        addr: uint128{
            0,
            0xffff00000000 |
                uint64(addr[0])<<24 | uint64(addr[1])<<16 |
                uint64(addr[2])<<8 | uint64(addr[3])},
        z: z4,
    }
}

Unmap() turns an IPv4-mapped IPv6 address into an IPv4 address by setting the z field to z4:

func (ip Addr) Unmap() Addr {
    if ip.Is4In6() {
        ip.z = z4
    }
    return ip
}

Implementing the reverse direction inside the Go standard library is trivial: we set the z field to z6noz if the address is IPv4.

// To6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func (ip Addr) To6() Addr {
    if ip.Is4() {
        ip.z = z6noz
    }
    return ip
}

Update (2026-10)

Instead of patching Go, we can use the -overlay flag of go build to hijack any package, including the standard library. In our case, it can add To6() to net/netip. Yet it is cumbersome:³ the flag expects a JSON file mapping absolute paths in GOROOT to replacement files, and you need to add it to every go command.

As a helper

We can’t access the z field from outside the net/netip package. Instead, we build a small helper around the netip.AddrFrom16(ip.As16()) pattern:

// AddrTo6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func AddrTo6(ip netip.Addr) netip.Addr {
    if ip.Is4() {
        ip = netip.AddrFrom16(ip.As16())
    }
    return ip
}

As an unsafe function

Another solution uses the unsafe package to alter the Addr struct through a proxy with the same memory layout:⁴

// addrProxy has the same memory layout as netip.Addr.
type addrProxy struct {
    addr [2]uint64      // netip.uint128
    z    unsafe.Pointer // unique.Handle[netip.addrDetail]
}

var (
    anyIPv6    = netip.IPv6Unspecified()
    netipZ6noz = (*addrProxy)(unsafe.Pointer(&anyIPv6)).z
)

// AddrTo6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func AddrTo6(ip netip.Addr) netip.Addr {
    if !ip.Is4() {
        return ip
    }
    (*addrProxy)(unsafe.Pointer(&ip)).z = netipZ6noz
    return ip
}

Benchmarks

On my computer, with Go 1.27.1, the standard library solution costs 0.88 ns per operation, while the solution favored by Go maintainers costs 7.14 ns. The unsafe solution matches the performance of the first one.

goos: linux
goarch: amd64
pkg: github.com/vincentbernat/go-netip-addrto6
cpu: AMD Ryzen 5 5600X 6-Core Processor
                   │     sec/op     │
AddrTo6/safe            7.137n ± 0%
AddrTo6/unsafe         0.8682n ± 2%
AddrTo6/builtin        0.8775n ± 2%

Assembly code

Let’s check the assembly code the compiler generates for each solution.⁵ The one built into the standard library looks like this:⁶

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ  net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE   end                      ; if not, stop here
 MOVQ  net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

Go’s assembly language is not a direct representation of the underlying machine language: it operates on a semi-abstract instruction set derived from Plan 9’s assembler. It has four pseudo-registers: FP (frame pointer for function arguments), PC (program counter), SB (static base pointer for global symbols), and SP (stack pointer). It also has architecture-specific registers like AX, CX, DX, BX, SI, DI, and R8 to R15. Instructions storing data use their last argument as the destination. Instructions can carry an explicit size suffix: MOVB moves a byte, MOVW 16 bits, MOVL 32 bits, and MOVQ 64 bits. In the example above, the first instruction compares the 64-bit value z4 with the CX register.

The unsafe solution looks almost the same:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ  net/netip·z4(SB), CX  ; check "z" if this is an IPv4 address
 JNE   end                   ; if not, stop here
 MOVQ  netipZ6noz(SB), CX    ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The helper solution has far more instructions. To understand why, let’s look at the code for As16() and AddrFrom16(). They are short enough for the compiler to inline them.

func (ip Addr) As16() (a16 [16]byte) {
    byteorder.BEPutUint64(a16[:8], ip.addr.hi)
    byteorder.BEPutUint64(a16[8:], ip.addr.lo)
    return a16
}

func AddrFrom16(addr [16]byte) Addr {
    return Addr{
        addr: uint128{
            byteorder.BEUint64(addr[:8]),
            byteorder.BEUint64(addr[8:]),
        },
        z: z6noz,
    }
}

We can already guess the pattern to optimize: the code packs the IP address into an array, copies it, then unpacks it. If we inline the Go code by hand, we get:

func AddrTo6(input netip.Addr) netip.Addr {
    if !input.Is4() {
        return input
    }

    var a16 [16]byte
    byteorder.BEPutUint64(a16[:8], input.addr.hi)
    byteorder.BEPutUint64(a16[8:], input.addr.lo)

    addr := a16

    var output netip.Addr
    output.addr.hi = byteorder.BEUint64(addr[:8])
    output.addr.lo = byteorder.BEUint64(addr[8:])
    output.z = netip.z6noz
    return output
}

As humans, we can mentally derive the optimized form:

func AddrTo6(input netip.Addr) netip.Addr {
    if !input.Is4() {
        return input
    }
    var output netip.Addr
    output.addr.hi = input.addr.hi
    output.addr.lo = input.addr.lo
    output.z = netip.z6noz
    return output
}

Unfortunately, as of Go 1.26.8, the compiler is not smart enough to do the same:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
; Push the stack (32 bytes):
;    0(SP) addr netip.uint128
;   16(SP) a16 [16]byte
 PUSHQ   BP
 MOVQ    SP, BP
 SUBQ    $32, SP

 CMPQ    net/netip·z4(SB), CX  ; check "z" if this is an IPv4 address
 JNE     end                   ; if not, stop here

; Pack: byteorder.BEPutUint64(a16[:8], input.addr.hi)
;       byteorder.BEPutUint64(a16[8:], input.addr.lo)
 MOVBEQ  AX, net/netip·a16+16(SP)
 MOVBEQ  BX, net/netip·a16+24(SP)

; addr = a16, 16 bytes at once through the vector register X0
 MOVUPS  net/netip·a16+16(SP), X0
 MOVUPS  X0, net/netip·addr(SP)

; CX = netip.z6noz
 MOVQ    net/netip·z6noz(SB), CX
; Unpack: output.addr.hi = byteorder.BEUint64(addr[:8])
;         output.addr.lo = byteorder.BEUint64(addr[8:])
 MOVBEQ  net/netip·addr(SP), AX
 MOVBEQ  net/netip·addr+8(SP), BX

end:
 ADDQ    $32, SP
 POPQ    BP
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The compiler does a decent job on the byte shuffling: the eight byte stores of BEPutUint64() become a single MOVBEQ, which stores a register byte-swapped. The eight byte loads of BEUint64() become a single MOVBEQ the other way round.⁷ Three groups of instructions remain: a pack, a copy, and an unpack.

Hacking the Go compiler

The Go compiler has several phases:

Parsing: The compiler tokenizes and parses the source code. It builds a syntax tree for each source file.
Type checking: The compiler maps each identifier to the object it denotes, folds constants, and infers the type of every expression.
IR construction: The compiler converts the syntax tree and its types into its own intermediate representation (IR). This process, called “noding,” goes through a serialization format named unified IR.
Middle end: The compiler performs several optimization passes on the IR, such as devirtualization, function call inlining, and escape analysis.
Walk: This phase runs two steps: order of evaluation decomposes complex statements into simpler ones, and desugaring transforms higher-level Go constructs, like switch or channels, into more primitive instructions or calls to the runtime.
Generic SSA: The compiler converts the IR into Static Single Assignment (SSA) form, a lower-level intermediate representation suited for machine-independent optimizations and rewrite rules.
Machine code generation: The compiler rewrites the SSA form into machine-specific variants, allocates registers, and applies more optimization passes. At the end, the assembler turns the generated instructions into machine code.

The hammer

My first idea is to replace occurrences of netip.AddrFrom16(ip.As16()) with netip.Addr{addr: ip.addr, z: netip.z6noz} as early as possible, during the “noding” process. Before that, the type checking phase prevents us from accessing unexported struct fields.

Go 1.27 introduced a convenient debug option to dump the IR of a function at interesting points during compilation:

$ GOTOOLCHAIN=go1.27.1 GOAMD64=v3 go build -a -gcflags="-d=astdump=AddrTo6Safe" .
Writing text ast output for AddrTo6Safe to AddrTo6Safe.ast
Writing html ast output for AddrTo6Safe to AddrTo6Safe.html
Writing html syntax output for AddrTo6Safe to AddrTo6Safe.syntax.html

In the HTML file, the first column shows the IR as it comes out of noding:

DCLFUNC addrto6.AddrTo6Safe ABI:ABIInternal FUNC-func(netip.Addr) netip.Addr
DCLFUNC-Dcl
. NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. NAME-addrto6.~r0 Class:PPARAMOUT Offset:0 OnStack netip.Addr
DCLFUNC-body
. IF # ipv6_safe.go:11:2
. IF-Cond
. . CALLFUNC bool
. . CALLFUNC-Fun
. . . METHEXPR addrto6.Is4 FUNC-func(netip.Addr) bool
. . . . TYPE netip.Addr Class:PEXTERN Offset:0 type netip.Addr
. . CALLFUNC-Args
. . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. IF-Body
. . AS # ipv6_safe.go:12:6
. . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . . CALLFUNC netip.Addr
. . . CALLFUNC-Fun
. . . . NAME-netip.AddrFrom16 Class:PFUNC Offset:0 Used FUNC-func([16]byte) netip.Addr
. . . CALLFUNC-Args
. . . . CALLFUNC ARRAY-[16]byte
. . . . CALLFUNC-Fun
. . . . . METHEXPR addrto6.As16 FUNC-func(netip.Addr) [16]byte
. . . . . . TYPE netip.Addr Class:PEXTERN Offset:0 type netip.Addr
. . . . CALLFUNC-Args
. . . . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. RETURN # ipv6_safe.go:14:2
. RETURN-Results
. . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr

In the body of the if statement, we spot the calls to the method netip.Addr.As16() and to the function netip.AddrFrom16(). Our goal is to patch them with a struct literal:

IF-Body
. AS # ipv6_safe.go:12:6
. . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . STRUCTLIT netip.Addr
. . STRUCTLIT-List
. . . STRUCTKEY netip.addr
. . . . DOT netip.addr netip.uint128
. . . . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . . STRUCTKEY netip.z
. . . . NAME-netip.z6noz Class:PEXTERN Offset:0 unique.Handle[net/netip.addrDetail]

In noder’s reader.go, the expr() method builds the IR tree for an expression. At the end of the exprCall case, we add a call to a rewriteAddrFrom16As16() function. It takes the current node and returns the struct literal on success, or nil if the rewrite is not possible. First, we check that we have the expected pattern: a call to the netip.AddrFrom16() function with a call to the netip.Addr.As16() method as its only argument:

func rewriteAddrFrom16As16(n ir.Node) ir.Node {
    call, ok := n.(*ir.CallExpr)
    if !ok || call.Op() != ir.OCALLFUNC ||
        len(call.Args) != 1 || len(call.Init()) != 0 ||
        !isNetipFunc(call.Fun, "AddrFrom16") {
        return nil
    }
    inner, ok := call.Args[0].(*ir.CallExpr)
    if !ok || inner.Op() != ir.OCALLFUNC ||
        len(inner.Args) != 1 || len(inner.Init()) != 0 ||
        !isNetipFunc(inner.Fun, "Addr.As16") {
        return nil
    }
    x := inner.Args[0]
    // [...]
}

Then, we fetch netip.z6noz:

z6noz, err := lookupVar(ir.StaticCalleeName(call.Fun).Sym().Pkg, "z6noz")
if err != nil {
    return nil
}

And we build the struct literal:

typ := call.Type()
pos := call.Pos()
var list []ir.Node
for i, f := range typ.Fields() {
    var value ir.Node
    switch f.Sym.Name {
    case "addr":
        value = typecheck.DotField(pos, x, i)
    case "z":
        value = z6noz
    default:
        return nil
    }
    list = append(list, ir.NewStructKeyExpr(pos, f, value))
}
lit := ir.NewCompLitExpr(pos, ir.OSTRUCTLIT, typ, list)
lit.SetTypecheck(1)
return lit

Have a look at the complete patch.⁸ We can test it with the following commands:

$ cd src
$ ./make.bash
Building Go cmd/dist using /usr/lib/go-1.27. (go1.27.1 linux/amd64)
Building Go toolchain1 and bootstrap cmd/go (go_bootstrap) using /usr/lib/go-1.27.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
Building Go toolchain3 and commands using go_bootstrap and Go toolchain2.
Checking command staleness for linux/amd64.
---
Installed Go for linux/amd64 in /home/bernat/code/free/go
Installed commands in /home/bernat/code/free/go/bin
*** You need to add /home/bernat/code/free/go/bin to your PATH.
$ export PATH=$PWD/../bin:$PATH
$ go version
go version go1.28-devel_9834516e20 Sat Sep 12 08:23:11 2026 -0700 linux/amd64
$ go test net/netip/...
ok      net/netip   0.224s
$ cd ../../go-netip-addrto6
$ go test .
ok      github.com/vincentbernat/go-netip-addrto6   0.062s

The generated code for the helper is now the shortest possible version!

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ    net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE     end                      ; if not, stop here
 MOVQ    net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

Go maintainers are unlikely to accept this change. It relies on the internal structure of net/netip.Addr. It’s an ugly hack in the noder, whose job is to faithfully translate the type-checked AST into the IR. And it’s harder to maintain than adding a To6() method.

The screwdriver

The right place for such an optimization is the generic SSA phase. One of the last machine-independent passes is memcombine. With the appropriate debug flag, the compiler dumps the SSA form after this pass:⁹

$ GOTOOLCHAIN=go1.26.8 GOAMD64=v3 \
> go build -a -gcflags='-d=ssa/memcombine/dump=AddrTo6Safe' .
$ head -5 AddrTo6Safe_01__memcombine.dump
AddrTo6Safe func(netip.Addr) netip.Addr
  b2:
    (?) v1 = InitMem <mem>
    (?) v2 = SP <uintptr>
    (?) v3 = SB <uintptr>

The result of the memcombine pass follows the same structure as the assembly code for AddrTo6Safe() we looked at earlier: two stores, one move, and two loads we would like to optimize away.

; […]
  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v466 = ArgIntReg <*netip.addrDetail> {ip+16} [2]  ; input.z
; […]
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)

  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16

  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v416 = Load <uint64> v285 v286                    ; addr[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi
  v174 = Load <uint64> v415 v286                    ; addr[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo
; […]

Each line features a value identifier (v442), an operation with its type (Bswap64 <uint64>), and its arguments (v490).¹⁰ Values are the basic building blocks of SSA and are defined exactly once. Square brackets enclose integer parameters ([8]) and curly braces contain auxiliary arguments ({netip.addr}). Operations writing to memory produce a new memory state. Every memory operation takes the current state as its last argument, which keeps them in order.

On paper

Let’s focus on output.addr.lo, aka v39:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v174 = Load <uint64> v415 v286                    ; addr[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

To simplify this code, we could apply three rewriting rules:

The first one adds a shortcut when loading through a move: (Load (OffPtr [o] p) (Move p src mem)) => (Load (OffPtr [o] src) mem). This matches v174 with its arguments v415 and v286 and creates a new value v600:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Load <uint64> v600 v282                    ; a16[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

The second one simplifies a load following a store: (Load p (Store p x _)) => x. The load is forwarded: the stored value replaces it and no memory access remains. It matches v174. It notices that v600 and v173 are the same address and replaces v174 with a copy of v442:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Copy <uint64> v442                         ; bswap(input.addr.lo)
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

The last step cancels the two byte swaps: (Bswap64 (Bswap64 x)) => x. v39 becomes a copy of v490:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Copy <uint64> v442                         ; bswap(input.addr.lo)
  v39  = Copy <uint64> v490                         ; output.addr.lo = input.addr.lo

If we ignore the values not needed to compute v39, only this SSA form remains:

  v490 = ArgIntReg <uint64> {ip+8} [1]  ; input.addr.lo
  v39  = Copy <uint64> v490             ; output.addr.lo = input.addr.lo

Let’s switch to output.addr.hi, aka v299:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Load <uint64> v285 v286                    ; addr[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

To optimize it away, we also apply three rewriting rules:

The first one also adds a shortcut when loading through a move, but without an offset: (Load p (Move p src mem)) => (Load src mem). This rewrites v416 to use arguments from v286:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Load <uint64> v22 v282                     ; a16[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

The second rule forwards a value stored one step earlier, skipping over a store to another address: (Load p (Store q _ (Store p x _))) => x. This matches v416: x is v542, p is v22 (&a16), q is v173 (&a16[8]), and p and q do not overlap for uint64.

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Copy <uint64> v542                         ; bswap(input.addr.hi)
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

The third rule cancels two byte swaps: (Bswap64 (Bswap64 x)) => x. v299 becomes a copy of v502:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Copy <uint64> v542                         ; bswap(input.addr.hi)
  v299 = Copy <uint64> v502                         ; output.addr.hi = input.addr.hi

If we remove the values not used to compute v299, we get this SSA form:

  v502 = ArgIntReg <uint64> {ip+0} [0] ; input.addr.hi
  v299 = Copy <uint64> v502            ; output.addr.hi = input.addr.hi

In practice

Most of these rules already exist in generic.rules. They use conditions to validate their context: ssa.IsSamePtr() for the same address, ssa.Disjoint() for addresses that do not overlap. The rule forwarding a stored value to a load already exists with three variants looking through several other stores. Here are the two we need:

(Load <t1> p1 (Store {t2} p2 x _))
    && ssa.IsSamePtr(p1, p2)
    && copyCompatibleType(t1, x.Type)
    && t1.Size() == t2.Size()
    => x
(Load <t1> p1 (Store {t2} p2 _ (Store {t3} p3 x _)))
    && ssa.IsSamePtr(p1, p3)
    && copyCompatibleType(t1, x.Type)
    && t1.Size() == t3.Size()
    && ssa.Disjoint(p3, t3, p2, t2)
    => x

Go 1.27 added the rule loading through a move with CL 748200 to fix issue #77720:

(Load <t1> op1:(OffPtr [o1] p1) move:(Move [n] p2 src mem))
    && o1 >= 0 && o1+t1.Size() <= n && ssa.IsSamePtr(p1, p2)
    && !ssa.IsVolatile(src)
    => @move.Block (Load <t1> (OffPtr <op1.Type> [o1] src) mem)

It lacks a variant without an offset:

(Load <t1> p1 move:(Move [n] p2 src mem))
    && p1.Op != ssaop.OpOffPtr
    && t1.Size() <= n && ssa.IsSamePtr(p1, p2)
    && !ssa.IsVolatile(src)
    => @move.Block (Load <t1> (OffPtr <p1.Type> [0] src) mem)

There is no generic rule to cancel two byte swaps, but the AMD64 lowering pass includes this rule:

(BSWAP(Q|L) (BSWAP(Q|L) p)) => p

After switching to Go’s development branch and adding the missing rule, the generated assembly code is worse than with Go 1.26.8, even though our additional rule slightly improves the situation at the end:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
; Push the stack (16 bytes):
;    0(SP) a16 [16]byte
 PUSHQ   BP
 MOVQ    SP, BP
 SUBQ    $16, SP

 CMPQ    net/netip·z4(SB), CX       ; check "z" if this is an IPv4 address
 JNE     end                        ; if not, stop here

; The four forwarded bytes: the low half of input.addr.lo is taken apart and
; put back together in registers
 MOVQ    BX, DX                     ; DX = input.addr.lo
 SHRQ    $24, BX                    ; BX = input.addr.lo >> 24
 MOVQ    DX, SI                     ; SI = input.addr.lo
 SHRQ    $16, DX                    ; DX = input.addr.lo >> 16
 MOVQ    SI, DI                     ; DI = input.addr.lo, kept for the pack
 SHRQ    $8, SI                     ; SI = input.addr.lo >> 8
 MOVBLZX DIB, R8                    ; R8 = byte(input.addr.lo)
 MOVBLZX SIB, SI                    ; SI = byte(input.addr.lo >> 8)
 SHLQ    $8, SI
 ORQ     R8, SI                     ; SI = two low bytes of input.addr.lo
 MOVBLZX DL, DX                     ; DX = byte(input.addr.lo >> 16)
 SHLQ    $16, DX
 ORQ     SI, DX
 MOVBLZX BL, BX                     ; BX = byte(input.addr.lo >> 24)
 SHLQ    $24, BX
 ORQ     DX, BX                     ; BX = input.addr.lo & 0xffffffff

; Pack: byteorder.BEPutUint64(a16[:8], input.addr.hi)
;       byteorder.BEPutUint64(a16[8:], input.addr.lo)
 MOVBEQ  AX, net/netip·a16(SP)
 MOVBEQ  DI, net/netip·a16+8(SP)

; The four other bytes of input.addr.lo, read one by one from a16
 MOVBLZX net/netip·a16+11(SP), DX   ; a16[11]
 SHLQ    $32, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+10(SP), DX   ; a16[10]
 SHLQ    $40, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+9(SP), DX    ; a16[9]
 SHLQ    $48, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+8(SP), DX    ; a16[8]
 SHLQ    $56, DX

; output.z = netip.z6noz
 MOVQ    net/netip·z6noz(SB), CX
; output.addr.hi = byteorder.BEUint64(a16[:8])
 MOVBEQ  net/netip·a16(SP), AX
; output.addr.lo assembled from the previous steps
 ORQ     DX, BX

end:
 LEAVEQ
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The rule loading through a move, added in Go 1.27, introduced this regression.

Out of order

Let’s not give up now! In reality, the rewriting rules run before memcombine, notably in the late opt pass. At this point, the inlined versions of BEPutUint64() and BEUint64() still expand to sixteen byte stores and sixteen byte loads, matching their source code:

func BEUint64(b []byte) uint64 {
    _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
    return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
        uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
}

Let’s follow two bytes of output.addr.lo: addr[15] and addr[11]. Here is a simplified SSA form before late opt:

  v273 = Trunc64to8 <byte> v490                     ; byte(input.addr.lo)
  v226 = Trunc64to8 <byte> v225                     ; byte(input.addr.lo >> 32)
; […]
  v235 = Store <mem> {byte} v233 v226 v223          ; a16[11] = byte(lo >> 32)
  v247 = Store <mem> {byte} v245 v238 v235          ; a16[12] = …
  v259 = Store <mem> {byte} v257 v250 v247          ; a16[13] = …
  v271 = Store <mem> {byte} v269 v262 v259          ; a16[14] = …
  v282 = Store <mem> {byte} v280 v273 v271          ; a16[15] = byte(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
; […]
  v433 = OffPtr <*byte> [15] v285                   ; &addr[15]
  v435 = Load <byte> v433 v286                      ; addr[15]
  v479 = OffPtr <*byte> [11] v285                   ; &addr[11]
  v481 = Load <byte> v479 v286                      ; addr[11]

The first rule loads through the move: (Load (OffPtr [o] p) (Move p src mem)) => (Load (OffPtr [o] src) mem). It matches both loads, which now read a16 with the memory state before the copy:

  v600 = OffPtr <*byte> [15] v22 ; &a16[15]
  v435 = Load <byte> v600 v282   ; a16[15]
  v601 = OffPtr <*byte> [11] v22 ; &a16[11]
  v481 = Load <byte> v601 v282   ; a16[11]

The second rule shortcuts a load following a store: (Load p (Store p x _)) => x. It matches v435, as v282 stores a16[15]. It does not match v481: v235 stores a16[11] four stores earlier in the chain, while the variants of this rule look through three stores at most.

  v435 = Copy <byte> v273        ; byte(input.addr.lo)
  v601 = OffPtr <*byte> [11] v22 ; &a16[11]
  v481 = Load <byte> v601 v282   ; a16[11]

The same happens to the other bytes: the rule forwards the four bytes stored last, a16[12] to a16[15]. The twelve other loads now read a16 instead of addr.

BEUint64() becomes a chain of Or64, each one adding a byte shifted into place. memcombine is a pass written in Go, not a set of rewrite rules. It starts from the last Or64 of the chain and collects up to eight terms. If each term is a byte load, extended to 64 bits and shifted, and if the eight loads read consecutive addresses from the same pointer with the same memory state, it replaces the whole chain with a single 64-bit load and a byte swap. Otherwise, it tries again with four, then two terms, and from each intermediate Or64. Here is the loop checking each term in a simplified version of combineLoads():

for i := int64(0); i < n; i++ {
    v := a[i]
    shift := int64(0)
    if v.Op == shiftOp {
        v, shift = peelShift(v)
    }
    if v.Op != extOp {
        return false
    }
    load := v.Args[0]
    if load.Op != ssaop.OpLoad {
        return false
    }
    if load.Args[1] != mem {
        return false
    }
    p, off := splitPtr(load.Args[0])
    if p != base {
        return false
    }
    r[i] = LoadRecord{load: load, offset: off, shift: shift}
}

For output.addr.hi, the eight loads read a16 with the same memory state v282:

  v13  = Load <byte> v22 v282               ; a16[0]
  v530 = Load <byte> v14 v282               ; a16[1]
  v488 = Load <byte> v504 v282              ; a16[2]
  v405 = Load <byte> v537 v282              ; a16[3]
  v385 = Load <byte> v397 v282              ; a16[4]
  v361 = Load <byte> v373 v282              ; a16[5]
  v196 = Load <byte> v63 v282               ; a16[6]
  v432 = Load <byte> v315 v282              ; a16[7]
  v319 = ZeroExt8to64 <uint64> v432         ; uint64(a16[7])
  v329 = ZeroExt8to64 <uint64> v196         ; uint64(a16[6])
  v330 = Lsh64x64 <uint64> [true] v329 v138 ; uint64(a16[6]) << 8
  v331 = Or64 <uint64> v319 v330            ; a16[7] | a16[6] << 8
; […] same for a16[5] to a16[1]
  v401 = ZeroExt8to64 <uint64> v13          ; uint64(a16[0])
  v402 = Lsh64x64 <uint64> [true] v401 v55  ; uint64(a16[0]) << 56
  v403 = Or64 <uint64> v402 v391            ; | a16[0] << 56 = output.addr.hi

memcombine merges them into one load and a swap:

  v286 = Load <uint64> v22 v282   ; a16[:8]
  v285 = Bswap64 <uint64> v286    ; output.addr.hi

For output.addr.lo, here is the chain memcombine sees after late opt:

  v436 = ZeroExt8to64 <uint64> v273 ; addr[15], forwarded
  v448 = Or64 <uint64> v436 v447    ; | addr[14] << 8, forwarded
  v460 = Or64 <uint64> v459 v448    ; | addr[13] << 16, forwarded
  v472 = Or64 <uint64> v471 v460    ; | addr[12] << 24, forwarded
  v484 = Or64 <uint64> v483 v472    ; | a16[11] << 32, loaded
  v496 = Or64 <uint64> v495 v484    ; | a16[10] << 40, loaded
  v508 = Or64 <uint64> v507 v496    ; | a16[9] << 48, loaded
  v520 = Or64 <uint64> v519 v508    ; | a16[8] << 56, loaded

From v520, four of the eight terms are forwarded bytes, not loads from memory, and memcombine can’t combine them. It doesn’t merge the four remaining loads either, as they sit on top of the forwarded bytes.

Back in order

In summary, the rewriting rules run too early to be effective. A quick workaround exists: run an earlier round of memcombine before late opt. After this change, the generated code for the helper is back to the shortest possible version:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ    net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE     end                      ; if not, stop here
 MOVQ    net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

And the benchmark confirms it! ✌️

goos: linux
goarch: amd64
pkg: github.com/vincentbernat/go-netip-addrto6
cpu: AMD Ryzen 5 5600X 6-Core Processor
                   │   Go 1.26.8    │             Our branch              │
                   │     sec/op     │    sec/op     vs base               │
AddrTo6/safe          6.5470n ±  0%   0.8944n ± 4%  -86.34% (p=0.002 n=6)
AddrTo6/unsafe        0.9071n ±  3%   0.8682n ± 1%   -4.28% (p=0.002 n=6)
AddrTo6/builtin       0.8871n ±  2%   0.8785n ± 1%        ~ (p=0.310 n=6)

Next steps

I think Go maintainers would reject this change because of the additional memcombine pass. Instead, I plan to publish this blog post and bring up the subject again as a follow-up to issue #54365. Either the sheer complexity and the Go 1.27 regression convince the maintainers that adding a To6() method is simpler and more efficient, or they advise me on how to move forward. Either way, digging into this subject taught me a lot about the Go compiler! ⚙️

Update (2026-10)

I opened issue #81994 to propose Addr.To6(). Give it a 👍 if you want it in Go!

IPv4-mapped IPv6 addresses let you handle only IPv6 addresses in your code and keep conversions at a few well-defined boundaries. I use them in Akvorado. ↩
This is not strictly equivalent. The zero value becomes :: while it would make more sense to leave it untouched. ↩
I suppose Go maintainers keep it inconvenient on purpose: they don’t want random packages to patch the standard library or other packages. ↩
To avoid catastrophic bugs when netip.Addr’s layout changes, you must add tests to detect it. This is more dangerous if you put this code in a package. Either ask users to run the tests themselves, or detect the change at run time and panic. Hiding this optimization behind a build tag would make users aware of this potential trap. ↩
I produced the assembly code with GOTOOLCHAIN=go1.26.8 GOAMD64=v3 ./go-asm '\.asm' from the companion repository, then edited it a bit to keep this article from turning into an endless rabbit hole. Due to an unfortunate sequence of events, we switch between versions: Go 1.27 introduced a regression that blurs the point of this article. ↩
The function is short enough for the compiler to inline it, so the assembly code may vary depending on the surrounding code. ↩
MOVBEQ requires GOAMD64=v3, matching the x86-64-v3 microarchitecture from 2013. Otherwise, the compiler translates BEPutUint64() to BSWAPQ+MOVQ and BEUint64() to MOVQ+BSWAPQ. ↩
When the call is used as a statement, a struct literal alone is invalid. The patch then turns it into _ = netip.Addr{…}. ↩

The compiler can also write an HTML file with the result of each pass:

$ GOSSAFUNC=AddrTo6Safe \
> GOTOOLCHAIN=go1.26.8 \
> GOAMD64=v3 go build -a .
dumped SSA for AddrTo6Safe,1 to ./ssa.html

↩

Source line numbers in parentheses follow value identifiers, but I removed them from the examples. The SSA form also features branches, but we don’t need them to understand our optimizations. ↩

Vincent Bernat: Hacking the Go compiler to efficiently map IPv4 to IPv6

Sun, 04 Oct 2026 13:27:25 +0000

The alternatives

Modifying the Go standard library

Internally, netip.Addr stores any IP address as a 128-bit value with an extra field z to encode the family and the zone:

type Addr struct {
    addr uint128
    z unique.Handle[addrDetail]
}

type addrDetail struct {
    isV6   bool   // IPv4 is false, IPv6 is true.
    zoneV6 string // != "" only if IsV6 is true.
}

var (
    z0    unique.Handle[addrDetail]
    z4    = unique.Make(addrDetail{})
    z6noz = unique.Make(addrDetail{isV6: true})
)

AddrFrom4() encodes an IPv4 address as an IPv4-mapped IPv6 address and sets z to the unique value z4:

// AddrFrom4 returns the address of the IPv4 address given by the bytes in addr.
func AddrFrom4(addr [4]byte) Addr {
    return Addr{
        addr: uint128{
            0,
            0xffff00000000 |
                uint64(addr[0])<<24 | uint64(addr[1])<<16 |
                uint64(addr[2])<<8 | uint64(addr[3])},
        z: z4,
    }
}

Unmap() turns an IPv4-mapped IPv6 address into an IPv4 address by setting the z field to z4:

func (ip Addr) Unmap() Addr {
    if ip.Is4In6() {
        ip.z = z4
    }
    return ip
}

Implementing the reverse direction inside the Go standard library is trivial: we set the z field to z6noz if the address is IPv4.

// To6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func (ip Addr) To6() Addr {
    if ip.Is4() {
        ip.z = z6noz
    }
    return ip
}

As a helper

We can’t access the z field from outside the net/netip package. Instead, we build a small helper around the netip.AddrFrom16(ip.As16()) pattern:

// AddrTo6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func AddrTo6(ip netip.Addr) netip.Addr {
    if ip.Is4() {
        ip = netip.AddrFrom16(ip.As16())
    }
    return ip
}

As an unsafe function

Another solution uses the unsafe package to alter the Addr struct through a proxy with the same memory layout:³

// addrProxy has the same memory layout as netip.Addr.
type addrProxy struct {
    addr [2]uint64      // netip.uint128
    z    unsafe.Pointer // unique.Handle[netip.addrDetail]
}

var (
    anyIPv6    = netip.IPv6Unspecified()
    netipZ6noz = (*addrProxy)(unsafe.Pointer(&anyIPv6)).z
)

// AddrTo6 maps an IPv4 address to an IPv4-mapped IPv6 address. It returns an
// IPv6 address unmodified.
func AddrTo6(ip netip.Addr) netip.Addr {
    if !ip.Is4() {
        return ip
    }
    (*addrProxy)(unsafe.Pointer(&ip)).z = netipZ6noz
    return ip
}

Benchmarks

goos: linux
goarch: amd64
pkg: github.com/vincentbernat/go-netip-addrto6
cpu: AMD Ryzen 5 5600X 6-Core Processor
                   │     sec/op     │
AddrTo6/safe            7.137n ± 0%
AddrTo6/unsafe         0.8682n ± 2%
AddrTo6/builtin        0.8775n ± 2%

Assembly code

Let’s check the assembly code the compiler generates for each solution.⁴ The one built into the standard library looks like this:⁵

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ  net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE   end                      ; if not, stop here
 MOVQ  net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The unsafe solution looks almost the same:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ  net/netip·z4(SB), CX  ; check "z" if this is an IPv4 address
 JNE   end                   ; if not, stop here
 MOVQ  netipZ6noz(SB), CX    ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The helper solution has far more instructions. To understand why, let’s look at the code for As16() and AddrFrom16(). They are short enough for the compiler to inline them.

func (ip Addr) As16() (a16 [16]byte) {
    byteorder.BEPutUint64(a16[:8], ip.addr.hi)
    byteorder.BEPutUint64(a16[8:], ip.addr.lo)
    return a16
}

func AddrFrom16(addr [16]byte) Addr {
    return Addr{
        addr: uint128{
            byteorder.BEUint64(addr[:8]),
            byteorder.BEUint64(addr[8:]),
        },
        z: z6noz,
    }
}

We can already guess the pattern to optimize: the code packs the IP address into an array, copies it, then unpacks it. If we inline the Go code by hand, we get:

func AddrTo6(input netip.Addr) netip.Addr {
    if !input.Is4() {
        return input
    }

    var a16 [16]byte
    byteorder.BEPutUint64(a16[:8], input.addr.hi)
    byteorder.BEPutUint64(a16[8:], input.addr.lo)

    addr := a16

    var output netip.Addr
    output.addr.hi = byteorder.BEUint64(addr[:8])
    output.addr.lo = byteorder.BEUint64(addr[8:])
    output.z = netip.z6noz
    return output
}

As humans, we can mentally derive the optimized form:

func AddrTo6(input netip.Addr) netip.Addr {
    if !input.Is4() {
        return input
    }
    var output netip.Addr
    output.addr.hi = input.addr.hi
    output.addr.lo = input.addr.lo
    output.z = netip.z6noz
    return output
}

Unfortunately, as of Go 1.26.8, the compiler is not smart enough to do the same:

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
; Push the stack (32 bytes):
;    0(SP) addr netip.uint128
;   16(SP) a16 [16]byte
 PUSHQ   BP
 MOVQ    SP, BP
 SUBQ    $32, SP

 CMPQ    net/netip·z4(SB), CX  ; check "z" if this is an IPv4 address
 JNE     end                   ; if not, stop here

; Pack: byteorder.BEPutUint64(a16[:8], input.addr.hi)
;       byteorder.BEPutUint64(a16[8:], input.addr.lo)
 MOVBEQ  AX, net/netip·a16+16(SP)
 MOVBEQ  BX, net/netip·a16+24(SP)

; addr = a16, 16 bytes at once through the vector register X0
 MOVUPS  net/netip·a16+16(SP), X0
 MOVUPS  X0, net/netip·addr(SP)

; CX = netip.z6noz
 MOVQ    net/netip·z6noz(SB), CX
; Unpack: output.addr.hi = byteorder.BEUint64(addr[:8])
;         output.addr.lo = byteorder.BEUint64(addr[8:])
 MOVBEQ  net/netip·addr(SP), AX
 MOVBEQ  net/netip·addr+8(SP), BX

end:
 ADDQ    $32, SP
 POPQ    BP
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The compiler does a decent job on the byte shuffling: the eight byte stores of BEPutUint64() become a single MOVBEQ, which stores a register byte-swapped. The eight byte loads of BEUint64() become a single MOVBEQ the other way round.⁶ Three groups of instructions remain: a pack, a copy, and an unpack.

Hacking the Go compiler

The Go compiler has several phases:

Parsing: The compiler tokenizes and parses the source code. It builds a syntax tree for each source file.
Type checking: The compiler maps each identifier to the object it denotes, folds constants, and infers the type of every expression.
IR construction: The compiler converts the syntax tree and its types into its own intermediate representation (IR). This process, called “noding,” goes through a serialization format named unified IR.
Middle end: The compiler performs several optimization passes on the IR, such as devirtualization, function call inlining, and escape analysis.
Walk: This phase runs two steps: order of evaluation decomposes complex statements into simpler ones, and desugaring transforms higher-level Go constructs, like switch or channels, into more primitive instructions or calls to the runtime.
Generic SSA: The compiler converts the IR into Static Single Assignment (SSA) form, a lower-level intermediate representation suited for machine-independent optimizations and rewrite rules.
Machine code generation: The compiler rewrites the SSA form into machine-specific variants, allocates registers, and applies more optimization passes. At the end, the assembler turns the generated instructions into machine code.

The hammer

Go 1.27 introduced a convenient debug option to dump the IR of a function at interesting points during compilation:

$ GOTOOLCHAIN=go1.27.1 GOAMD64=v3 go build -a -gcflags="-d=astdump=AddrTo6Safe" .
Writing text ast output for AddrTo6Safe to AddrTo6Safe.ast
Writing html ast output for AddrTo6Safe to AddrTo6Safe.html
Writing html syntax output for AddrTo6Safe to AddrTo6Safe.syntax.html

In the HTML file, the first column shows the IR as it comes out of noding:

DCLFUNC addrto6.AddrTo6Safe ABI:ABIInternal FUNC-func(netip.Addr) netip.Addr
DCLFUNC-Dcl
. NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. NAME-addrto6.~r0 Class:PPARAMOUT Offset:0 OnStack netip.Addr
DCLFUNC-body
. IF # ipv6_safe.go:11:2
. IF-Cond
. . CALLFUNC bool
. . CALLFUNC-Fun
. . . METHEXPR addrto6.Is4 FUNC-func(netip.Addr) bool
. . . . TYPE netip.Addr Class:PEXTERN Offset:0 type netip.Addr
. . CALLFUNC-Args
. . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. IF-Body
. . AS # ipv6_safe.go:12:6
. . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . . CALLFUNC netip.Addr
. . . CALLFUNC-Fun
. . . . NAME-netip.AddrFrom16 Class:PFUNC Offset:0 Used FUNC-func([16]byte) netip.Addr
. . . CALLFUNC-Args
. . . . CALLFUNC ARRAY-[16]byte
. . . . CALLFUNC-Fun
. . . . . METHEXPR addrto6.As16 FUNC-func(netip.Addr) [16]byte
. . . . . . TYPE netip.Addr Class:PEXTERN Offset:0 type netip.Addr
. . . . CALLFUNC-Args
. . . . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. RETURN # ipv6_safe.go:14:2
. RETURN-Results
. . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr

In the body of the if statement, we spot the calls to the method netip.Addr.As16() and to the function netip.AddrFrom16(). Our goal is to patch them with a struct literal:

IF-Body
. AS # ipv6_safe.go:12:6
. . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . STRUCTLIT netip.Addr
. . STRUCTLIT-List
. . . STRUCTKEY netip.addr
. . . . DOT netip.addr netip.uint128
. . . . . NAME-addrto6.ip Class:PPARAM Offset:0 OnStack Used netip.Addr
. . . STRUCTKEY netip.z
. . . . NAME-netip.z6noz Class:PEXTERN Offset:0 unique.Handle[net/netip.addrDetail]

func rewriteAddrFrom16As16(n ir.Node) ir.Node {
    call, ok := n.(*ir.CallExpr)
    if !ok || call.Op() != ir.OCALLFUNC ||
        len(call.Args) != 1 || len(call.Init()) != 0 ||
        !isNetipFunc(call.Fun, "AddrFrom16") {
        return nil
    }
    inner, ok := call.Args[0].(*ir.CallExpr)
    if !ok || inner.Op() != ir.OCALLFUNC ||
        len(inner.Args) != 1 || len(inner.Init()) != 0 ||
        !isNetipFunc(inner.Fun, "Addr.As16") {
        return nil
    }
    x := inner.Args[0]
    // [...]
}

Then, we fetch netip.z6noz:

z6noz, err := lookupVar(ir.StaticCalleeName(call.Fun).Sym().Pkg, "z6noz")
if err != nil {
    return nil
}

And we build the struct literal:

typ := call.Type()
pos := call.Pos()
var list []ir.Node
for i, f := range typ.Fields() {
    var value ir.Node
    switch f.Sym.Name {
    case "addr":
        value = typecheck.DotField(pos, x, i)
    case "z":
        value = z6noz
    default:
        return nil
    }
    list = append(list, ir.NewStructKeyExpr(pos, f, value))
}
lit := ir.NewCompLitExpr(pos, ir.OSTRUCTLIT, typ, list)
lit.SetTypecheck(1)
return lit

Have a look at the complete patch.⁷ We can test it with the following commands:

$ cd src
$ ./make.bash
Building Go cmd/dist using /usr/lib/go-1.27. (go1.27.1 linux/amd64)
Building Go toolchain1 and bootstrap cmd/go (go_bootstrap) using /usr/lib/go-1.27.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
Building Go toolchain3 and commands using go_bootstrap and Go toolchain2.
Checking command staleness for linux/amd64.
---
Installed Go for linux/amd64 in /home/bernat/code/free/go
Installed commands in /home/bernat/code/free/go/bin
*** You need to add /home/bernat/code/free/go/bin to your PATH.
$ export PATH=$PWD/../bin:$PATH
$ go version
go version go1.28-devel_9834516e20 Sat Sep 12 08:23:11 2026 -0700 linux/amd64
$ go test net/netip/...
ok      net/netip   0.224s
$ cd ../../go-netip-addrto6
$ go test .
ok      github.com/vincentbernat/go-netip-addrto6   0.062s

The generated code for the helper is now the shortest possible version!

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ    net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE     end                      ; if not, stop here
 MOVQ    net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The screwdriver

$ GOTOOLCHAIN=go1.26.8 GOAMD64=v3 \
> go build -a -gcflags='-d=ssa/memcombine/dump=AddrTo6Safe' .
$ head -5 AddrTo6Safe_01__memcombine.dump
AddrTo6Safe func(netip.Addr) netip.Addr
  b2:
    (?) v1 = InitMem <mem>
    (?) v2 = SP <uintptr>
    (?) v3 = SB <uintptr>

The result of the memcombine pass follows the same structure as the assembly code for AddrTo6Safe() we looked at earlier: two stores, one move, and two loads we would like to optimize away.

; […]
  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v466 = ArgIntReg <*netip.addrDetail> {ip+16} [2]  ; input.z
; […]
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)

  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16

  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v416 = Load <uint64> v285 v286                    ; addr[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi
  v174 = Load <uint64> v415 v286                    ; addr[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo
; […]

Each line features a value identifier (v442), an operation with its type (Bswap64 <uint64>), and its arguments (v490).⁹ Values are the basic building blocks of SSA and are defined exactly once. Square brackets enclose integer parameters ([8]) and curly braces contain auxiliary arguments ({netip.addr}). Operations writing to memory produce a new memory state. Every memory operation takes the current state as its last argument, which keeps them in order.

On paper

Let’s focus on output.addr.lo, aka v39:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v174 = Load <uint64> v415 v286                    ; addr[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

To simplify this code, we could apply three rewriting rules:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Load <uint64> v600 v282                    ; a16[8:]
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Copy <uint64> v442                         ; bswap(input.addr.lo)
  v39  = Bswap64 <uint64> v174                      ; output.addr.lo

The last step cancels the two byte swaps: (Bswap64 (Bswap64 x)) => x. v39 becomes a copy of v490:

  v490 = ArgIntReg <uint64> {ip+8} [1]              ; input.addr.lo
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v442 = Bswap64 <uint64> v490                      ; bswap(input.addr.lo)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v415 = OffPtr <*byte> [8] v285                    ; &addr[8]
  v600 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v174 = Copy <uint64> v442                         ; bswap(input.addr.lo)
  v39  = Copy <uint64> v490                         ; output.addr.lo = input.addr.lo

If we ignore the values not needed to compute v39, only this SSA form remains:

  v490 = ArgIntReg <uint64> {ip+8} [1]  ; input.addr.lo
  v39  = Copy <uint64> v490             ; output.addr.lo = input.addr.lo

Let’s switch to output.addr.hi, aka v299:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Load <uint64> v285 v286                    ; addr[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

To optimize it away, we also apply three rewriting rules:

The first one also adds a shortcut when loading through a move, but without an offset: (Load p (Move p src mem)) => (Load src mem). This rewrites v416 to use arguments from v286:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Load <uint64> v22 v282                     ; a16[:8]
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Copy <uint64> v542                         ; bswap(input.addr.hi)
  v299 = Bswap64 <uint64> v416                      ; output.addr.hi

The third rule cancels two byte swaps: (Bswap64 (Bswap64 x)) => x. v299 becomes a copy of v502:

  v502 = ArgIntReg <uint64> {ip+0} [0]              ; input.addr.hi
  v22 = LocalAddr <*[16]byte> {netip.a16} v2 v1     ; &a16
  v173 = OffPtr <*byte> [8] v22                     ; &a16[8]
  v542 = Bswap64 <uint64> v502                      ; bswap(input.addr.hi)
  v161 = Store <mem> {uint64} v22 v542 v23          ; a16[:8] = bswap(hi)
  v282 = Store <mem> {uint64} v173 v442 v161        ; a16[8:] = bswap(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
  v416 = Copy <uint64> v542                         ; bswap(input.addr.hi)
  v299 = Copy <uint64> v502                         ; output.addr.hi = input.addr.hi

If we remove the values not used to compute v299, we get this SSA form:

  v502 = ArgIntReg <uint64> {ip+0} [0] ; input.addr.hi
  v299 = Copy <uint64> v502            ; output.addr.hi = input.addr.hi

In practice

(Load <t1> p1 (Store {t2} p2 x _))
    && ssa.IsSamePtr(p1, p2)
    && copyCompatibleType(t1, x.Type)
    && t1.Size() == t2.Size()
    => x
(Load <t1> p1 (Store {t2} p2 _ (Store {t3} p3 x _)))
    && ssa.IsSamePtr(p1, p3)
    && copyCompatibleType(t1, x.Type)
    && t1.Size() == t3.Size()
    && ssa.Disjoint(p3, t3, p2, t2)
    => x

Go 1.27 added the rule loading through a move with CL 748200 to fix issue #77720:

(Load <t1> op1:(OffPtr [o1] p1) move:(Move [n] p2 src mem))
    && o1 >= 0 && o1+t1.Size() <= n && ssa.IsSamePtr(p1, p2)
    && !ssa.IsVolatile(src)
    => @move.Block (Load <t1> (OffPtr <op1.Type> [o1] src) mem)

It lacks a variant without an offset:

(Load <t1> p1 move:(Move [n] p2 src mem))
    && p1.Op != ssaop.OpOffPtr
    && t1.Size() <= n && ssa.IsSamePtr(p1, p2)
    && !ssa.IsVolatile(src)
    => @move.Block (Load <t1> (OffPtr <p1.Type> [0] src) mem)

There is no generic rule to cancel two byte swaps, but the AMD64 lowering pass includes this rule:

(BSWAP(Q|L) (BSWAP(Q|L) p)) => p

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
; Push the stack (16 bytes):
;    0(SP) a16 [16]byte
 PUSHQ   BP
 MOVQ    SP, BP
 SUBQ    $16, SP

 CMPQ    net/netip·z4(SB), CX       ; check "z" if this is an IPv4 address
 JNE     end                        ; if not, stop here

; The four forwarded bytes: the low half of input.addr.lo is taken apart and
; put back together in registers
 MOVQ    BX, DX                     ; DX = input.addr.lo
 SHRQ    $24, BX                    ; BX = input.addr.lo >> 24
 MOVQ    DX, SI                     ; SI = input.addr.lo
 SHRQ    $16, DX                    ; DX = input.addr.lo >> 16
 MOVQ    SI, DI                     ; DI = input.addr.lo, kept for the pack
 SHRQ    $8, SI                     ; SI = input.addr.lo >> 8
 MOVBLZX DIB, R8                    ; R8 = byte(input.addr.lo)
 MOVBLZX SIB, SI                    ; SI = byte(input.addr.lo >> 8)
 SHLQ    $8, SI
 ORQ     R8, SI                     ; SI = two low bytes of input.addr.lo
 MOVBLZX DL, DX                     ; DX = byte(input.addr.lo >> 16)
 SHLQ    $16, DX
 ORQ     SI, DX
 MOVBLZX BL, BX                     ; BX = byte(input.addr.lo >> 24)
 SHLQ    $24, BX
 ORQ     DX, BX                     ; BX = input.addr.lo & 0xffffffff

; Pack: byteorder.BEPutUint64(a16[:8], input.addr.hi)
;       byteorder.BEPutUint64(a16[8:], input.addr.lo)
 MOVBEQ  AX, net/netip·a16(SP)
 MOVBEQ  DI, net/netip·a16+8(SP)

; The four other bytes of input.addr.lo, read one by one from a16
 MOVBLZX net/netip·a16+11(SP), DX   ; a16[11]
 SHLQ    $32, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+10(SP), DX   ; a16[10]
 SHLQ    $40, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+9(SP), DX    ; a16[9]
 SHLQ    $48, DX
 ORQ     DX, BX
 MOVBLZX net/netip·a16+8(SP), DX    ; a16[8]
 SHLQ    $56, DX

; output.z = netip.z6noz
 MOVQ    net/netip·z6noz(SB), CX
; output.addr.hi = byteorder.BEUint64(a16[:8])
 MOVBEQ  net/netip·a16(SP), AX
; output.addr.lo assembled from the previous steps
 ORQ     DX, BX

end:
 LEAVEQ
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

The rule loading through a move, added in Go 1.27, introduced this regression.

Out of order

func BEUint64(b []byte) uint64 {
    _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
    return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
        uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
}

Let’s follow two bytes of output.addr.lo: addr[15] and addr[11]. Here is a simplified SSA form before late opt:

  v273 = Trunc64to8 <byte> v490                     ; byte(input.addr.lo)
  v226 = Trunc64to8 <byte> v225                     ; byte(input.addr.lo >> 32)
; […]
  v235 = Store <mem> {byte} v233 v226 v223          ; a16[11] = byte(lo >> 32)
  v247 = Store <mem> {byte} v245 v238 v235          ; a16[12] = …
  v259 = Store <mem> {byte} v257 v250 v247          ; a16[13] = …
  v271 = Store <mem> {byte} v269 v262 v259          ; a16[14] = …
  v282 = Store <mem> {byte} v280 v273 v271          ; a16[15] = byte(lo)
  v285 = LocalAddr <*[16]byte> {netip.addr} v2 v282 ; &addr
  v286 = Move <mem> {[16]byte} [16] v285 v22 v282   ; addr = a16
; […]
  v433 = OffPtr <*byte> [15] v285                   ; &addr[15]
  v435 = Load <byte> v433 v286                      ; addr[15]
  v479 = OffPtr <*byte> [11] v285                   ; &addr[11]
  v481 = Load <byte> v479 v286                      ; addr[11]

The first rule loads through the move: (Load (OffPtr [o] p) (Move p src mem)) => (Load (OffPtr [o] src) mem). It matches both loads, which now read a16 with the memory state before the copy:

  v600 = OffPtr <*byte> [15] v22 ; &a16[15]
  v435 = Load <byte> v600 v282   ; a16[15]
  v601 = OffPtr <*byte> [11] v22 ; &a16[11]
  v481 = Load <byte> v601 v282   ; a16[11]

  v435 = Copy <byte> v273        ; byte(input.addr.lo)
  v601 = OffPtr <*byte> [11] v22 ; &a16[11]
  v481 = Load <byte> v601 v282   ; a16[11]

The same happens to the other bytes: the rule forwards the four bytes stored last, a16[12] to a16[15]. The twelve other loads now read a16 instead of addr.

for i := int64(0); i < n; i++ {
    v := a[i]
    shift := int64(0)
    if v.Op == shiftOp {
        v, shift = peelShift(v)
    }
    if v.Op != extOp {
        return false
    }
    load := v.Args[0]
    if load.Op != ssaop.OpLoad {
        return false
    }
    if load.Args[1] != mem {
        return false
    }
    p, off := splitPtr(load.Args[0])
    if p != base {
        return false
    }
    r[i] = LoadRecord{load: load, offset: off, shift: shift}
}

For output.addr.hi, the eight loads read a16 with the same memory state v282:

  v13  = Load <byte> v22 v282               ; a16[0]
  v530 = Load <byte> v14 v282               ; a16[1]
  v488 = Load <byte> v504 v282              ; a16[2]
  v405 = Load <byte> v537 v282              ; a16[3]
  v385 = Load <byte> v397 v282              ; a16[4]
  v361 = Load <byte> v373 v282              ; a16[5]
  v196 = Load <byte> v63 v282               ; a16[6]
  v432 = Load <byte> v315 v282              ; a16[7]
  v319 = ZeroExt8to64 <uint64> v432         ; uint64(a16[7])
  v329 = ZeroExt8to64 <uint64> v196         ; uint64(a16[6])
  v330 = Lsh64x64 <uint64> [true] v329 v138 ; uint64(a16[6]) << 8
  v331 = Or64 <uint64> v319 v330            ; a16[7] | a16[6] << 8
; […] same for a16[5] to a16[1]
  v401 = ZeroExt8to64 <uint64> v13          ; uint64(a16[0])
  v402 = Lsh64x64 <uint64> [true] v401 v55  ; uint64(a16[0]) << 56
  v403 = Or64 <uint64> v402 v391            ; | a16[0] << 56 = output.addr.hi

memcombine merges them into one load and a swap:

  v286 = Load <uint64> v22 v282   ; a16[:8]
  v285 = Bswap64 <uint64> v286    ; output.addr.hi

For output.addr.lo, here is the chain memcombine sees after late opt:

  v436 = ZeroExt8to64 <uint64> v273 ; addr[15], forwarded
  v448 = Or64 <uint64> v436 v447    ; | addr[14] << 8, forwarded
  v460 = Or64 <uint64> v459 v448    ; | addr[13] << 16, forwarded
  v472 = Or64 <uint64> v471 v460    ; | addr[12] << 24, forwarded
  v484 = Or64 <uint64> v483 v472    ; | a16[11] << 32, loaded
  v496 = Or64 <uint64> v495 v484    ; | a16[10] << 40, loaded
  v508 = Or64 <uint64> v507 v496    ; | a16[9] << 48, loaded
  v520 = Or64 <uint64> v519 v508    ; | a16[8] << 56, loaded

Back in order

// AX = input.addr.hi, BX = input.addr.lo, CX = input.z
 CMPQ    net/netip·z4(SB), CX     ; check "z" if this is an IPv4 address
 JNE     end                      ; if not, stop here
 MOVQ    net/netip·z6noz(SB), CX  ; CX = netip.z6noz
end:
 RET
// return value = Addr{hi: AX, lo: BX, z: CX}

And the benchmark confirms it! ✌️

goos: linux
goarch: amd64
pkg: github.com/vincentbernat/go-netip-addrto6
cpu: AMD Ryzen 5 5600X 6-Core Processor
                   │   Go 1.26.8    │             Our branch              │
                   │     sec/op     │    sec/op     vs base               │
AddrTo6/safe          6.5470n ±  0%   0.8944n ± 4%  -86.34% (p=0.002 n=6)
AddrTo6/unsafe        0.9071n ±  3%   0.8682n ± 1%   -4.28% (p=0.002 n=6)
AddrTo6/builtin       0.8871n ±  2%   0.8785n ± 1%        ~ (p=0.310 n=6)

Next steps

IPv4-mapped IPv6 addresses let you handle only IPv6 addresses in your code and keep conversions at a few well-defined boundaries. I use them in Akvorado. ↩
This is not strictly equivalent. The zero value becomes :: while it would make more sense to leave it untouched. ↩
To avoid catastrophic bugs when netip.Addr’s layout changes, you must add tests to detect it. This is more dangerous if you put this code in a package. Either ask users to run the tests themselves, or detect the change at run time and panic. Hiding this optimization behind a build tag would make users aware of this potential trap. ↩
I produced the assembly code with GOTOOLCHAIN=go1.26.8 GOAMD64=v3 ./go-asm '\.asm' from the companion repository, then edited it a bit to keep this article from turning into an endless rabbit hole. Due to an unfortunate sequence of events, we switch between versions: Go 1.27 introduced a regression that blurs the point of this article. ↩
The function is short enough for the compiler to inline it, so the assembly code may vary depending on the surrounding code. ↩
MOVBEQ requires GOAMD64=v3, matching the x86-64-v3 microarchitecture from 2013. Otherwise, the compiler translates BEPutUint64() to BSWAPQ+MOVQ and BEUint64() to MOVQ+BSWAPQ. ↩
When the call is used as a statement, a struct literal alone is invalid. The patch then turns it into _ = netip.Addr{…}. ↩

The compiler can also write an HTML file with the result of each pass:

$ GOSSAFUNC=AddrTo6Safe \
> GOTOOLCHAIN=go1.26.8 \
> GOAMD64=v3 go build -a .
dumped SSA for AddrTo6Safe,1 to ./ssa.html

↩

Source line numbers in parentheses follow value identifiers, but I removed them from the examples. The SSA form also features branches, but we don’t need them to understand our optimizations. ↩

Vincent Bernat: Self-hosted HTTP tunnels with SSH and nginx

Sat, 03 Oct 2026 07:23:12 +0000

A friend wants to proofread your work-in-progress blog post, but its preview only runs on localhost:8080. Several tools can help. Some run as a commercial service, like ngrok or Cloudflare Quick Tunnels. Some are self-hostable but require a specific client, like frp or localtunnel. Some only require a plain SSH client but rely on a specific SSH server, like sish. Let’s implement a self-hosted solution with only OpenSSH and nginx!

$ ssh -R 0:localhost:8080 http-over-ssh
Allocated port 41535 for remote forward to localhost:8080
https://6J3jK1WmB15c6WmjW_X-Wg--1789928654@p41535.ssh.luffy.cx/

Basic setup

First, we forward connections from a port on a remote server to your local service:

$ ssh -N -R 0:localhost:8080 web02.luffy.cx
Allocated port 41535 for remote forward to localhost:8080

When you specify 0 as the remote port, the server allocates a free port. Then, we configure nginx to proxy requests from https://p41535.ssh.luffy.cx to http://127.0.0.1:41535:

server {
  listen 0.0.0.0:443 ssl ;
  listen [::0]:443 ssl ;
  server_name ~^p(?<port>\d\d\d\d\d)\.ssh\.luffy\.cx$;
  location / {
    proxy_pass http://127.0.0.1:$port;
  }
}

We also need to add DNS records for *.ssh.luffy.cx and get a wildcard certificate through Let’s Encrypt:

*.ssh.luffy.cx.               CNAME web02.luffy.cx.
ssh.luffy.cx.                 CAA   0 issuewild "letsencrypt.org"
_acme-challenge.ssh.luffy.cx  CNAME ssh.luffy.cx.acme.luffy.cx.

acme.luffy.cx is a zone hosted on Route 53. I use it for ACME DNS-01 challenges, both for wildcard certificates and for domains served by several web servers. In my case, NixOS gets the certificates automatically.

Access control

The port is the only “secret”¹ keeping the content confidential. Other forwarding solutions add a random string to the domain name to prevent an intruder from enumerating the possible values.

Thanks to ngx_http_secure_link_module, we can secure this setup a bit. This module computes a hash² over a set of values, including a secret, and compares it with the hash from the request. The hash is base64-encoded, so we cannot put it in the domain name, which is case-insensitive. Instead, we put it in the URL as a username, along with its expiration timestamp:³

https://6J3jK1WmB15c6WmjW_X-Wg--1789928654@p41535.ssh.luffy.cx/en/blog
        ╰─────────┬──────────╯  ╰───┬────╯  ╰─┬─╯             ╰──┬───╯
                hash             expires    port               path

The client sends the username to the server with HTTP basic authentication. This works with most HTTP clients, including curl. Nginx exposes the username in the $remote_user variable. The module expects the hash and the expiration timestamp separated by a comma. We use a map directive to extract the two parts from $remote_user and join them with a comma.⁴ We also give the module the string to hash. It contains the expiration timestamp, the port, and a secret:

map $remote_user $httpssh_link {
  "~^([-_A-Za-z0-9]{22})--([0-9]+)$" "$1,$2";
}
server {
  # […]
  location / {
    secure_link $httpssh_link;
    secure_link_md5 "$secure_link_expires $port ZuPerS3cr3!";
  }
}

The module returns the status of the check in the $secure_link variable:

empty if the hashes do not match,
"0" if they match but the link has expired, or
"1" otherwise.

If the hash is incorrect or missing, we return a 401 error with a WWW-Authenticate header to ask for credentials. If the link has expired, we return a 410 error. We remove the Authorization header before forwarding the request and add a few directives to proxy WebSocket connections. Here is the complete configuration:⁵

map $remote_user $httpssh_link {
  "~^([-_A-Za-z0-9]{22})--([0-9]+)$" "$1,$2";
}
server {
  listen 0.0.0.0:443 ssl ;
  listen [::0]:443 ssl ;
  server_name ~^p(?<port>\d\d\d\d\d)\.ssh\.luffy\.cx$;
  location / {
    secure_link $httpssh_link;
    secure_link_md5 "$secure_link_expires $port ZuPerS3cr3!";
    if ($secure_link = "") {
      add_header WWW-Authenticate 'Basic realm="tunnel"' always;
      return 401;
    }
    if ($secure_link = "0") {
      return 410;
    }
    proxy_pass http://127.0.0.1:$port;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Authorization "";
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_buffering off;
    proxy_read_timeout 30m;
  }
}

I think you are now asking yourself the obvious question: “How should I generate the hash?” Easy peasy!

$ expires=$(( $(date +%s) + 86400 ))
$ port=41535
$ secret='ZuPerS3cr3!'
$ printf '%s %s %s' "$expires" "$port" "$secret" \
>   | openssl md5 -binary \
>   | openssl base64 \
>   | tr +/ -_ | tr -d =
6J3jK1WmB15c6WmjW_X-Wg

Well, I suppose you are now saying: “Vincent, this is not very convenient! I’ll stick with ngrok if you don’t mind.” Okay, I hear you. Let’s write a helper script.

Helper script

The main difficulty is finding the ephemeral port that OpenSSH allocates, as it does not appear in any environment variable.⁶ To work around this obstacle, we look for the ancestor sshd-session processes:⁷

pids=$(
  pid=$$
  while [ "$pid" -gt 1 ]; do
    line=$(ps -o comm=,pid=,ppid= -p "$pid")
    echo "$line"
    pid=${line##* }
  done | awk '$1 == "sshd-session" { printf "pid=%s,\n", $2 }'
)
if [ -z "$pids" ]; then
  echo "not an ssh session" >&2
  exit 1
fi

Then, we get the listening ports associated with these sshd-session processes:⁸

ports=$(sudo -n ss --listening --numeric --tcp --processes --no-header \
  | grep -F "$pids" \
  | awk '{ print $4 }' | awk -F: '{ print $NF }' \
  | sort -un)
if [ -z "$ports" ]; then
  echo "no forwarded port, use ssh -R 0:localhost:PORT" >&2
  exit 1
fi

Finally, we display the URLs and keep the session open:

lifetime=86400
secret='ZuPerS3cr3!'
expires=$(( $(date +%s) + lifetime ))
for port in $ports; do
  token=$(printf '%s %s %s' "$expires" "$port" "$secret" \
            | openssl md5 -binary \
            | openssl base64 \
            | tr +/ -_ | tr -d =)
  echo "https://$token--$expires@p$port.ssh.luffy.cx/"
done
sleep infinity

I install this script as http-over-ssh on the server and add this entry to my ~/.ssh/config:

Host http-over-ssh
  Hostname web02.luffy.cx
  RemoteCommand http-over-ssh
  ControlPath none

With this solution, I only rely on OpenSSH and nginx, two pieces of software already running on this server. One short command gives me a self-hosted tunnel and a URL to share. To try it, grab the complete helper script, which includes a few minor improvements. If you run NixOS, as any person of taste would, have a look at my http-over-ssh.nix instead. ❄️

Update (2026-10)

This post was widely discussed on Hacker News.

Since the kernel allocates it from the local port range, its entropy is low. Moreover, on Linux, we lose one more bit because the kernel favors odd ports when it picks a random free port.
```
$ sysctl -n net.ipv4.ip_local_port_range \
>   | awk '{print $1"—"$2" ≈ "log($2-$1+1)/log(2)" bits"}'
32768—60999 ≈ 14.785 bits
```
↩
The module relies on MD5. Its security is weak but good enough for this use. ↩
We need an expiration date because a later session could reuse the port, and we have no way to detect this case. ↩
The username could use a comma directly instead of a double dash. But some applications do not recognize the URL correctly, making it harder to share. ↩
This configuration exposes any TCP port listening on 127.0.0.1 or 0.0.0.0 to anyone with the secret, bypassing most firewall rules. You could strengthen it by limiting the server_name regex to the ephemeral port range. ↩
One SSH session can contain several tunnels, and the client can add or remove them at any time. This is unlike tun device forwarding (ssh -w), which gets its own SSH_TUNNEL environment variable. ↩
Since OpenSSH 9.8, sshd-session is the name of the helper handling the session. With older versions, look for sshd instead. ↩
We need sudo because the sshd-session process dropped its privileges. The kernel then marks it as not dumpable, and its /proc/PID/fd directory belongs to root. Without access to this directory, ss cannot find which process owns a socket. ↩

Ben Hutchings: FOSS activity in September 2026

Fri, 02 Oct 2026 14:34:15 +0000

Debian packages:
- firmware-nonfree:
  - Bugs:
    - closed #1148284: firmware-amd-graphics: AMD AV1 hardware decoding produces severe video artifacts with firmware 20260810-1
  - Merge requests:
    - opened and merged !154: Update to 20260916; fix some license information
  - Uploads:
    - uploaded version 20260810-1~bpo13+1 to trixie-backports
    - uploaded version 20260916-1 to unstable
- initramfs-tools:
  - Merge requests:
    - closed !202: mkinitramfs: fix path to kernel config in /lib/modules
- kernel-team:
  - Merge requests:
    - merged !14: find-recent-urgent: Sort bugs from linux first
    - opened !15: Add form responses for common problems with bug reports
- linux:
  - Bugs:
    - closed #1146373: linux-libc-dev: sbrk(2) allocates more than memory + swap space
  - Merge requests:
    - closed !2010: [x86] Backport security fixes for KVM (LTS)
    - merged !2083: linux-image: Bump Pre-Depends version on linux-base (>= 4.17~)
    - reviewed and merged !2095: 6.1 stable updates (LTS)
    - merged !2108: [alpha] Reenable CONFIG_COMPACTION
    - merged !2109: Enable BMI323 support as a module
    - merged !2110: riscv64 config update for linux 7.3
  - Uploads:
    - uploaded version 7.1.13-1~bpo13+1 to trixie-backports
    - uploaded version 7.2.6-1~bpo13+1 to trixie-backports
- linux-6.1 (LTS):
  - Bugs:
    - closed #1117674: Please enable udebs for the 6.1 backport
- linux-6.12 (LTS):
  - Uploads:
    - uploaded version 6.12.107-1~deb12u1 to bookworm-security
  - merged changes from trixie’s 6.12.111-1
- linux-base:
  - Uploads:
    - uploaded version 4.17~bpo13+1 to trixie-backports
- nfs-utils:
  - Merge requests:
    - reviewed !37: Install and use sysusers.d/tmpfiles.d config files
- wireless-regdb:
  - Uploads:
    - uploaded version 2026.09.03-1 to unstable
Mailing lists:
- debian-kernel:
  - posted Agenda items for kernel-team meeting on 2026-09-30
  - replied to Meta packages for modules
  - replied to Updating linux-6.12 (bookworm-security) to 6.12.107 (LTS)
- debian-lts-announce:
  - posted [SECURITY] [DLA 4788-1] linux-6.12 security update

Junichi Uekawa: Tokyo has been raining for many days but finally there's some sunny days.

Fri, 02 Oct 2026 07:56:37 +0000

Tokyo has been raining for many days but finally there's some sunny days.

Dirk Eddelbuettel: RcppFastAD 0.0.6 on CRAN: Agentic Fix

Thu, 01 Oct 2026 17:05:00 +0000

A week ago, release 0.0.5 of the RcppFastAD package went to CRAN, and we noted that it provided a stop-gap measure against a gnarly segfault with g++-16 under heavier optimization / inlining. We are happy to now announce that a new and fixed version 0.0.6 of RcppFastAD is now on CRAN, and has been built for r2u as well as at r-universe.

RcppFastAD wraps the FastAD header-only C++ library by James which provides a C++ implementation of both forward and reverse mode of automatic differentiation. It offers an easy-to-use header library that is both lightweight and performant. With a little of bit of Rcpp glue, it is also easy to use from R in simple C++ applications.

This release takes advantage of some large-language model inference access I now get via Debian. The Deepseek v4 flash-0731 model, driven in a container via the pi.dev harness, took just about no time finding a small workaround for the issue described last week where we could see segfaults under heavier optimization and inlining. The fix was to prohibit inlining the local bind() reimplementation. We have also sent this upstream as a patch. It is nice to have an option of querying something a little more powerful than the local models I experimented with before. We suppress more compiler warnings in local builds via another option, and did some standard maintenance.

The NEWS file for this release follows.

Changes in version 0.0.6 (2026-10-01)

The expression-template view rebinding is protected against g++ -O3 (which led to wrong Eigen::Map dimensions, an Eigen::Map resize assertion, and a segfault.

The bind() helpers are marked non-inline and are also protected from operating on a nullptr.

Both items co-written with DeepSeek V4 Flash, and have been sent upstream in a PR.

Suppress another compiler warning when local build detected.

Add r-universe badge to README.md.

Courtesy of my CRANberries, there is also a diffstat report for the most recent release. More information is available at the repository or the package page.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can now sponsor me at GitHub.

Ludovic Rousseau: macOS Golden Gate and smart cards status

Wed, 30 Sep 2026 13:13:27 +0000

I will compare this version of macOS with the previous one, Tahoe, which I presented in macOS Tahoe and smart cards status.

CCID

    $ grep -A 1 CFBundleShortVersionString /usr/libexec/SmartCardServices/drivers/ifd-ccid.bundle/Contents/Info.plist
            <key>CFBundleShortVersionString</key>
            <string>1.5.1</string>

There has been no change since the release of macOS Sonoma in 2023. The version of my CCID driver included in macOS is still 1.5.1.

Apple Open Source

The Open Source components included in macOS can be found at <https://opensource.apple.com/releases/>

The Open Source components for Golden Gate 27.0 are not yet available.

The SmartcardCCID software is available at https://github.com/apple-oss-distributions/SmartcardCCID. The git history shows that the code has not been modified since September 2024.

New readers supported since release 1.5.1

Since the release 1.5.1 of my CCID driver in November 2022, many new readers have been added. The latest version is 1.8.4 (released in September 2026).

1.8.4
- THALES PKI Transaction Pad
1.8.3
- Broadcom Corp 58200 0x5884
- Broadcom Corp 58200 0x5885
- Broadcom Corp 58200 0x5886
- Broadcom Corp 58200 0x5887
- Circle CIR135 ICC
- DigiFlow LLP. KAZTOKEN
- HID Global Crescendo NFC Reader
- HID Global OMNIKEY Plug
- HID Global OMNIKEY SE Plug
- Neowave LinkeoC-PRO
- Swissbit iShield Key 2 Pro
1.8.0
- GLSolutions NM61 PC/SC
- Identiv uTrust FIDO2 Security Key
- Kensington VeriMark NFC+ USB-C Security Key
- MARX CryptoTech LP Tokey 3 FIDO
- mCore Contact-Reader
- mCore Contactless-Reader
- mCore DualSlot-Reader
- Pol Henarejos Pico Fido
- Pol Henarejos Pico HSM
- Pol Henarejos Pico OpenPGP
- Richmond Technologies CO. LLC AEGIS PRO4 Smart Card Reader
- SCR Prime
1.7.1
- ACS APG8201-B2
- BUDGET E-ID BUD001
- CHERRY Smart Board 1150
- CryptnoxCR CryptnoxCR
- Diebold Nixdorf PN7362au CCID
- FT BioPass FIDO2 Pro
- Nitrokey Nitrokey Passkey
1.7.0
- GIGA-TMS NFC CCID Reader
- Identiv Identiv SmartOS Reader
- SEC1210URT, single slot variant of SEC1210 serial
- TOKEN2 FIDO2 Security Key(0013),PIN+ Mini with OTP + PGP
- TOKEN2 FIDO2 Security Key(0014),PIN+ Mini with FIDO + PGP
- TOKEN2 FIDO2 Security Key(0015),PIN+ Mini with PGP
- TOKEN2 FIDO2 Security Key(0016),PIN+ Mini with OTP + PGP + FIDO
- TOKEN2 FIDO2 Security Key(0023),PIN+ Series with OTP + PGP
- TOKEN2 FIDO2 Security Key(0024),PIN+ Series with FIDO + PGP
- TOKEN2 FIDO2 Security Key(0025),PIN+ Series with PGP
- TOKEN2 FIDO2 Security Key(0203),Bio3 Dual with OTP + PGP
- TOKEN2 FIDO2 Security Key(0204),Bio3 Dual with FIDO + PGP
- TOKEN2 FIDO2 Security Key(0205),Bio3 Dual with PGP
- TOKEN2 FIDO2 Security Key(0206),Bio3 Dual with OTP + PGP + FIDO
- TOKEN2 Molto2 (older version)
- VIX TECHNOLOGY SECURE READER
1.6.2
- Arculus AuthentiKey
- BHDC Reader-HHD02
- CHERRY Smart Terminal 1150
- HSIC CCID-Reader
- Ledger Flex
- SYC USB CCID Reader
- Thales RF CR2000
- TOKEN2 FIDO2 Security Key(0026)
1.6.0
- Aladdin R.D. JCR SecurBio
- AvidCard CAC Smart Card Reader
- FujitsuTechnologySolutions GmbH Dual Smartcard Reader D321
- Ledger Stax
- NXP Pegoda 3
- authenton #1- CTAP2.1
1.5.5
- Alpha-Project ANGARA Token
- Broadcom Corp 58200 (idProduct: 0x5864)
- Broadcom Corp 58200 (idProduct: 0x5865)
- Imprivata USB CCID
- KAPELSE eS-KAP-Ad
- Kapelse inSide
- KAPELSE KAP-Care
- KAPELSE KAP-eCV
- KAPELSE KAP-GO
- KAPELSE KAP-LINK2
- Kapelse KAP-Move
- Kapelse Ti-Kap
- rf IDEAS USB CCID
- SIMHUB pcsc reader
1.5.3
- ACS ACR1552 1S CL Reader
- ACS ACR1552 CL Reader
- ACS ACR1581
- ACS ACR40T ICC Reader
- ACS ACR40U ICC Reader
- ACS WalletMate 1S CL Reader
- Aktiv Rutoken SCR 3101 NFC Reader
- CIRIGHT ONE PASS U2F
- Dexon Tecnologias Digitais LTDA eSmartDX
- Excelsecu Card reader
- GHI NC001
- Identiv uTrust Token Flex
- SpringCard M519 with idProduct: 0x6212
- SpringCard M519 with idProduct: 0x621A
- WCMi SD5931
1.5.2
- KAPELSE KAP-LINK
- LDU LANDI
- Sensyl SSC-HV Reader
- TOKEN2 MFA NFC Reader
- TOKEN2 Molto2
- Thales RF Reader

Due to SIP (System Integrity Protection, https://support.apple.com/guide/security/secb7ea06b49/web) it is difficult to update the configuration of the installed CCID driver (version 1.5.1).

If you have one of the 96 readers listed above, and the Apple driver is not working for you, installing an updated version of my CCID driver is the only option.

Apple CCID driver

$ defaults read /Library/Preferences/com.apple.security.smartcard.plist
{
        Logging = 0;
}

The Apple CCID driver is used by default.

If you want or need to use my CCID driver instead, simply follow follow the instructions at Apple's own CCID driver in Sonoma.

Known bugs

The page listing the bugs I found in macOS Sonoma can be found under macOS Sonoma and smart cards: known bugs.

Apple has not informed me that any of these bugs have been fixed in Golden Gate (or Tahoe). I therefore assume that the bugs are still present.

I have just verified that the issue involving SCardControl() (macOS Sonoma bug: SCardControl() (part 2)) is still present. Its behaviour is slightly different now though, so I assume Apple has changed some of the code. If you have a pinpad reader and want to use the Secure PIN Entry feature, you should switch to using my CCID driver.

Conclusion

As I mentioned in my article about macOS Tahoe, if you encounter any issues with your smart card on macOS Golden Gate, I recommend switching from the Apple driver to my CCID driver and checking again.

Gunnar Wolf: The Origins of GPU Computing

Tue, 29 Sep 2026 18:55:02 +0000

This post is an unpublished review for The Origins of GPU Computing

This article appears in the “Communications of the ACM” magazine as part of a series devoting to showcasing relevant examples of technologies where federal funding of academic research have resulted in widely impacting, clearly identifiable technological advances that have visibly improved –or, at least, changed– life far beyond the technological arena.

The road leading from the first parallel computing technologies built completely for research, through a phase that was preeminently directed at gaming, and back to leading current GPUs, that are basically massively parallel supercomputers used for LLM training and inference and other IA tasks, is far from trivial, and the authors make a good job outlining it in few pages. The article is written in a clearly divulgatory way, staying as clear of technical language as possible.

The authors present three main enabling technologies for current GPU technologies: Parallel computing, parallel graphics systems, and stream processing.

Coming from a technical formation myself, although clearly better grounded in the software side of Computer Engineering than on the electronics side, the most interesting “nugget of information” I take is that parallel computing was born due to the fact that transistor switching consumes very little energy, whereas communication along wires consumes much more — so the more simultaneous operations can be carried out on-chip at once, the less power will be dissipated as heat (and the less time that will be lost due to data stores and loads).

Graphics systems are a natural match for parallel systems, as rendering realistic images basically requires repeating the same blocks of instructions to a large array of items. Early GPU implementations were built on fixed-function graphics pipelines, but by the turn of the century, when nVidia spinned off the research labs at Stanford and started marketing their product, introducing along the way the Graphical Processing Unit term, product, they enabled it to implement the full OpenGL graphics pipeline on a single chip.

Stream processing is the arrangement of in-chip electronics so that they can better exploit producer-consumer locality between stages, in order to achieve greater arithmetic intensity (this is, a greater computation-to-bandwidth ratio), decreasing the total number of access to memory accesses.

The authors explain in broad terms the described technologies and how they fit together, and how the technology was transferred from the universities to the companies that became the most dynamic companies behind today’s top trending technologies.

I felt the article to be engaging and easy to read. As a technologist, I did miss more details — dates when specific advances were made, how some of the advances joined into further inventions… But I understand the aim of the “Federal Funding of Academic Research” series’ aim is more towards outsiders. And, as such, this work very well explains how trillion-dollar technologies are only the result of decades of funding research ideas.

Otto Kekäläinen: Using multiple git remotes for true distributed version control

Mon, 28 Sep 2026 00:00:00 +0000

One of the primary design principles for Linus Torvalds when creating Git is that it should be a distributed system, capable of working with multiple remotes. However, most people seem to use Git with just one remote, typically having GitHub or GitLab as the only origin.

Version control systems before Git relied on a centralized model. For example in Subversion or CVS you could only sync with one single remote server, which was considered the primary host of the source code. Git however is not just a VCS, but a DVCS, for distributed version control system. If you currently use Git with just one single remote as if it was a centralized version control system, now is the time to change that and learn how to add multiple remotes, and configure more flexible git pull and git push rules.

The first concept to grasp is that Git can have multiple remotes. For example, after running a basic clone command such as git clone https://github.com/ottok/debcraft.git you would end up with a single remote origin pointing to GitHub:

$ git remote --verbose
origin https://github.com/ottok/debcraft.git (fetch)
origin https://github.com/ottok/debcraft.git (push)

You can however configure multiple remotes with the command git remote:

$ git remote rename origin github
$ git remote add gitlab https://gitlab.com/ottok/debcraft.git
$ git remote --verbose
github https://github.com/ottok/debcraft.git (fetch)
github https://github.com/ottok/debcraft.git (push)
gitlab https://gitlab.com/ottok/debcraft.git (fetch)
gitlab https://gitlab.com/ottok/debcraft.git (push)

You can push and pull from these individually, or from all at once:

$ git pull --all
Fetching github
Fetching gitlab
Already up to date.

When you review the git history, note the labels gitlab/main and github/main which tell which commit the branch main points to on various remotes. In this case they are all in sync and point to the same 5d1815c:

$ git log --oneline
5d1815c (HEAD -> main, gitlab/main, github/main) Bump Debhelper version from 13 to 14
ca518a7 Temporarily disable automatic copyright year bumping due to frequent bugs
d6e201e Exclude .pm from codespell to decrease false positives (Closes: #1140488)
708ee35 Exclude debian/copyright from codespell due to frequent false positives

When pushing, you can choose what remote to push to. For example, if I am working on branch dev and I only want to push it to GitLab to trigger a CI run there, I can run git push gitlab dev. You can also configure a default remote by running once git push --set-upstream gitlab dev and thereafter simply run git push and it will automatically push the branch dev only to that remote.

A related setting is remote.pushDefault, which tells git which remote to push to when a branch does not define one of its own, and it applies to every branch that lacks a [branch] section in .git/config. Setting it once is what lets a repository have a per-branch pull remote, like the debcraft example below, and still have a single, predictable git push target. To see which remote git will use for each of your branches, run git branch -vv, and to refresh the remote-tracking branches of all remotes at once, run git fetch --all --prune.

If you want to have multiple remotes, but automatically push and pull to all of them at once, you configure one single remote to have multiple URLs with git remote set-url --add. Since git prints one line per push URL, git remote -v then shows the same remote several times, once for each URL it pushes to.

As an illustration, in my actual local Debcraft development project I have all these configured:

$ git remote -v
github-pull-requests git@github.com:ottok/debcraft.git (fetch)
github-pull-requests git@github.com:ottok/debcraft.git (push)
gitlab-merge-requests git@gitlab.com:ottok/debcraft.git (fetch)
gitlab-merge-requests git@gitlab.com:ottok/debcraft.git (push)
origin git@salsa.debian.org:debian/debcraft.git (fetch)
origin git@salsa.debian.org:debian/debcraft.git (push)
origin git@gitlab.com:ottok/debcraft.git (push)
origin git@github.com:ottok/debcraft.git (push)
otto git@salsa.debian.org:otto/debcraft.git (fetch)
otto git@salsa.debian.org:otto/debcraft.git (push)
otto git@gitlab.com:ottok/debcraft.git (push)
otto git@github.com:ottok/debcraft.git (push)
otto git@git.sr.ht:~ottok/debcraft (push)
otto ssh://git@codeberg.org/ottok/Debcraft.git (push)
salsa-merge-requests git@salsa.debian.org:debian/debcraft.git (fetch)
salsa-merge-requests git@salsa.debian.org:debian/debcraft.git (push)

The settings can also be viewed directly in the config file:

$ cat .git/config
...
[remote "origin"]
url = git@salsa.debian.org:debian/debcraft.git
fetch = +refs/heads/*:refs/remotes/origin/*
pushurl = git@salsa.debian.org:debian/debcraft.git
pushurl = git@gitlab.com:ottok/debcraft.git
pushurl = git@github.com:ottok/debcraft.git
[remote "otto"]
url = git@salsa.debian.org:otto/debcraft.git
fetch = +refs/heads/*:refs/remotes/otto/*
pushurl = git@salsa.debian.org:otto/debcraft.git
pushurl = git@gitlab.com:ottok/debcraft.git
pushurl = git@github.com:ottok/debcraft.git
pushurl = git@git.sr.ht:~ottok/debcraft
pushurl = ssh://git@codeberg.org/ottok/Debcraft.git
...
[branch "main"]
remote = origin
merge = refs/heads/main
[branch "dev"]
remote = otto
merge = refs/heads/dev
...

On branch main:

Running git pull will fetch from salsa.debian.org/debian/debcraft (the primary git hosting for this project)
Running git push will push to Salsa, GitLab and GitHub, one after the other, making sure they all have the latest main

On branch dev:

Running git pull will fetch from salsa.debian.org/otto/debcraft (the personal fork)
Running git push will push to Salsa, GitLab, GitHub, Sourcehut and Codeberg all one after the other

The command output will have the same message three times, once for each remote (assuming they were all already up-to-date):

$ git push
Everything up-to-date
Everything up-to-date
Everything up-to-date

Use cases for distributed version control

The most obvious use case for any distributed system is improved availability. In this example, the salsa.debian.org is often overloaded/unavailable, so pushing to GitLab and GitHub as well allows collaborators to use them to fetch git commits if the primary code hosting site is unresponsive. Once it comes back online again, the next git push/pull will automatically bring it up to the same content as what backup hosts had.

The second main benefit is that having the code live on multiple code forges allows collaborators to use their own favorite host. Debcraft itself is a great example of this, as collaborators who don’t have a Salsa account can - and have - submitted Merge Requests on GitLab.com and Pull Requests on GitHub.com.

A third use case is code hosting migrations. If you for example want to gradually phase out GitHub.com and replace it with something else, you could configure git to pull from the old location and push to both, ensuring that other collaborators can start using the new code hosting location without disruptions to those who have not yet updated their remotes or done a fresh git clone from the new location.

Automating setting up a project on multiple code forges

While I don’t push all projects I work on to all Salsa/GitLab/GitHub, I do set up multiple remotes for enough git projects that I have this script to automate configuring a git repository that is cloned from Salsa to also push to GitLab and GitHub. It accepts the repository whether it was cloned over SSH or HTTPS, and it adds the push URLs and then pushes the current branch, all branches, and tags for you:

#!/bin/bash
# Add GitLab and GitHub push URLs to an existing git remote, so that a plain
# "git push" writes the same commits to all three code forges.
#
# Usage: ./git-multipush-salsa.sh
#
# Environment:
# SALSA_REMOTE remote to turn into a mirror, default origin
# SALSA_USER your Salsa user, only used to detect that the source
# remote is somebody else's project
# GITLAB_USER your GitLab user, default ottok
# GITHUB_USER your GitHub user, default ottok
# PROTOCOL ssh (default) or https, for the push URLs
set -euo pipefail
SCRIPT=$(basename "$0")
SALSA_REMOTE=${SALSA_REMOTE:-origin}
SALSA_USER=${SALSA_USER:-otto}
GITLAB_USER=${GITLAB_USER:-ottok}
GITHUB_USER=${GITHUB_USER:-ottok}
PROTOCOL=${PROTOCOL:-ssh}
die() { echo "$SCRIPT: $*" >&2; exit 1; }
# A failing command leaves the push URLs half configured behind, so say how
# to get back to where we started
fail()
{
echo "$SCRIPT: '$*' failed, the push URLs may already have been added" >&2
echo " git config --unset-all remote.${SALSA_REMOTE}.pushurl" >&2
echo " git remote set-url --add --push ${SALSA_REMOTE} ${SALSA_URL}" >&2
exit 1
}
git rev-parse --git-dir > /dev/null 2>&1 || die "not inside a git repository"
git remote | grep -qx "$SALSA_REMOTE" || die "no remote named '$SALSA_REMOTE'"
# Example: git@salsa.debian.org:otto/salsa-ci-pipeline.git
SALSA_URL=$(git remote get-url "$SALSA_REMOTE")
# The source remote may use any of the URL forms salsa.debian.org accepts,
# for example git@salsa.debian.org:otto/salsa-ci-pipeline.git or
# https://salsa.debian.org/otto/salsa-ci-pipeline.git
case "$SALSA_URL" in
git@salsa.debian.org:*) SALSA_PATH=${SALSA_URL#git@salsa.debian.org:} ;;
ssh://git@salsa.debian.org/*) SALSA_PATH=${SALSA_URL#ssh://git@salsa.debian.org/} ;;
https://salsa.debian.org/*) SALSA_PATH=${SALSA_URL#https://salsa.debian.org/} ;;
http://salsa.debian.org/*) SALSA_PATH=${SALSA_URL#http://salsa.debian.org/} ;;
*) die "unexpected source URL '$SALSA_URL', expected a salsa.debian.org URL" ;;
esac
SALSA_PATH=${SALSA_PATH%/}
SALSA_PATH=${SALSA_PATH%.git}
SOURCE_USER=${SALSA_PATH%%/*}
PROJECT=${SALSA_PATH##*/}
# Write the push URLs in one and the same protocol, no matter how the
# repository happens to have been cloned
if [ "$PROTOCOL" = "https" ]
then
SALSA_URL="https://salsa.debian.org/${SALSA_PATH}.git"
GITLAB_URL="https://gitlab.com/${GITLAB_USER}/${PROJECT}.git"
GITHUB_URL="https://github.com/${GITHUB_USER}/${PROJECT}.git"
else
SALSA_URL="git@salsa.debian.org:${SALSA_PATH}.git"
GITLAB_URL="git@gitlab.com:${GITLAB_USER}/${PROJECT}.git"
GITHUB_URL="git@github.com:${GITHUB_USER}/${PROJECT}.git"
fi
# Mirroring somebody else's project is fine, but it is usually not what you
# want: you most likely want to mirror your own fork instead
if [ "$SOURCE_USER" != "$SALSA_USER" ]
then
echo "Note: $SALSA_REMOTE points to $SOURCE_USER's project, not your own."
echo "To mirror your own fork, run this with SALSA_REMOTE set to its name."
echo
fi
# Bail out instead of adding the same push URLs twice
EXISTING=$(git remote get-url --push --all "$SALSA_REMOTE")
if [ "$(printf '%s\n' "$EXISTING" | wc -l)" -gt 1 ]
then
die "remote '$SALSA_REMOTE' already has multiple push URLs:
$EXISTING"
fi
echo "Mirroring $SALSA_URL to $GITLAB_URL and $GITHUB_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$SALSA_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$GITLAB_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$GITHUB_URL"
# Push the branch you have checked out first, and never with --force: the
# first branch a GitLab or GitHub project receives becomes its default branch,
# the one you then protect
DEFAULT_BRANCH=$(git symbolic-ref --short HEAD) || die "not on a branch, check out a branch first"
git push -u "$SALSA_REMOTE" "$DEFAULT_BRANCH"
git push "$SALSA_REMOTE" --all
git push "$SALSA_REMOTE" --tags
# The push above creates the GitLab and GitHub projects, but GitLab projects
# are private by default, so make the new mirror public with glab if installed.
if command -v glab > /dev/null
then
echo "Make the GitLab project public and describe it as a mirror:"
glab api -X PUT "projects/${GITLAB_USER}%2F${PROJECT}" \
-f visibility=public \
-f description="Mirror of ${SALSA_URL}" \
-f notification_email=disabled
else
echo "Install glab to do the same automatically, or visit"
echo "https://gitlab.com/${GITLAB_USER}/${PROJECT}/edit to make the project public"
fi
echo "To undo, drop all push URLs and add back only the original one:"
echo " git config --unset-all remote.${SALSA_REMOTE}.pushurl"
echo " git remote set-url --add --push ${SALSA_REMOTE} ${SALSA_URL}"

#!/bin/bash
# Add GitLab and GitHub push URLs to an existing git remote, so that a plain
# "git push" writes the same commits to all three code forges.
#
# Usage: ./git-multipush-salsa.sh
#
# Environment:
# SALSA_REMOTE remote to turn into a mirror, default origin
# SALSA_USER your Salsa user, only used to detect that the source
# remote is somebody else's project
# GITLAB_USER your GitLab user, default ottok
# GITHUB_USER your GitHub user, default ottok
# PROTOCOL ssh (default) or https, for the push URLs
set -euo pipefail
SCRIPT=$(basename "$0")
SALSA_REMOTE=${SALSA_REMOTE:-origin}
SALSA_USER=${SALSA_USER:-otto}
GITLAB_USER=${GITLAB_USER:-ottok}
GITHUB_USER=${GITHUB_USER:-ottok}
PROTOCOL=${PROTOCOL:-ssh}
die() { echo "$SCRIPT: $*" >&2; exit 1; }
# A failing command leaves the push URLs half configured behind, so say how
# to get back to where we started
fail()
{
echo "$SCRIPT: '$*' failed, the push URLs may already have been added" >&2
echo " git config --unset-all remote.${SALSA_REMOTE}.pushurl" >&2
echo " git remote set-url --add --push ${SALSA_REMOTE} ${SALSA_URL}" >&2
exit 1
}
git rev-parse --git-dir > /dev/null 2>&1 || die "not inside a git repository"
git remote | grep -qx "$SALSA_REMOTE" || die "no remote named '$SALSA_REMOTE'"
# Example: git@salsa.debian.org:otto/salsa-ci-pipeline.git
SALSA_URL=$(git remote get-url "$SALSA_REMOTE")
# The source remote may use any of the URL forms salsa.debian.org accepts,
# for example git@salsa.debian.org:otto/salsa-ci-pipeline.git or
# https://salsa.debian.org/otto/salsa-ci-pipeline.git
case "$SALSA_URL" in
git@salsa.debian.org:*) SALSA_PATH=${SALSA_URL#git@salsa.debian.org:} ;;
ssh://git@salsa.debian.org/*) SALSA_PATH=${SALSA_URL#ssh://git@salsa.debian.org/} ;;
https://salsa.debian.org/*) SALSA_PATH=${SALSA_URL#https://salsa.debian.org/} ;;
http://salsa.debian.org/*) SALSA_PATH=${SALSA_URL#http://salsa.debian.org/} ;;
*) die "unexpected source URL '$SALSA_URL', expected a salsa.debian.org URL" ;;
esac
SALSA_PATH=${SALSA_PATH%/}
SALSA_PATH=${SALSA_PATH%.git}
SOURCE_USER=${SALSA_PATH%%/*}
PROJECT=${SALSA_PATH##*/}
# Write the push URLs in one and the same protocol, no matter how the
# repository happens to have been cloned
if [ "$PROTOCOL" = "https" ]
then
SALSA_URL="https://salsa.debian.org/${SALSA_PATH}.git"
GITLAB_URL="https://gitlab.com/${GITLAB_USER}/${PROJECT}.git"
GITHUB_URL="https://github.com/${GITHUB_USER}/${PROJECT}.git"
else
SALSA_URL="git@salsa.debian.org:${SALSA_PATH}.git"
GITLAB_URL="git@gitlab.com:${GITLAB_USER}/${PROJECT}.git"
GITHUB_URL="git@github.com:${GITHUB_USER}/${PROJECT}.git"
fi
# Mirroring somebody else's project is fine, but it is usually not what you
# want: you most likely want to mirror your own fork instead
if [ "$SOURCE_USER" != "$SALSA_USER" ]
then
echo "Note: $SALSA_REMOTE points to $SOURCE_USER's project, not your own."
echo "To mirror your own fork, run this with SALSA_REMOTE set to its name."
echo
fi
# Bail out instead of adding the same push URLs twice
EXISTING=$(git remote get-url --push --all "$SALSA_REMOTE")
if [ "$(printf '%s\n' "$EXISTING" | wc -l)" -gt 1 ]
then
die "remote '$SALSA_REMOTE' already has multiple push URLs:
$EXISTING"
fi
echo "Mirroring $SALSA_URL to $GITLAB_URL and $GITHUB_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$SALSA_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$GITLAB_URL"
git remote set-url --add --push "$SALSA_REMOTE" "$GITHUB_URL"
# Push the branch you have checked out first, and never with --force: the
# first branch a GitLab or GitHub project receives becomes its default branch,
# the one you then protect
DEFAULT_BRANCH=$(git symbolic-ref --short HEAD) || die "not on a branch, check out a branch first"
git push -u "$SALSA_REMOTE" "$DEFAULT_BRANCH"
git push "$SALSA_REMOTE" --all
git push "$SALSA_REMOTE" --tags
# The push above creates the GitLab and GitHub projects, but GitLab projects
# are private by default, so make the new mirror public with glab if installed.
if command -v glab > /dev/null
then
echo "Make the GitLab project public and describe it as a mirror:"
glab api -X PUT "projects/${GITLAB_USER}%2F${PROJECT}" \
-f visibility=public \
-f description="Mirror of ${SALSA_URL}" \
-f notification_email=disabled
else
echo "Install glab to do the same automatically, or visit"
echo "https://gitlab.com/${GITLAB_USER}/${PROJECT}/edit to make the project public"
fi
echo "To undo, drop all push URLs and add back only the original one:"
echo " git config --unset-all remote.${SALSA_REMOTE}.pushurl"
echo " git remote set-url --add --push ${SALSA_REMOTE} ${SALSA_URL}"

If you prefer not to install glab, the last part simply reduces to visiting the GitLab project settings once and ticking the project public, and it is also worth setting a description like Mirror of https://salsa.debian.org/debian/debcraft and disabling notification email there, as nobody wants a mirror sending out a flood of emails every time you push.

There are a few caveats worth knowing about before mirroring everything everywhere. Every push to a remote with multiple push URLs writes to all of them, so a project with continuous integration configured on three forges will run its CI three times and cost you roughly three times as much. If one of the push URLs fails, say because the host is momentarily unreachable, git prints the error and stops there, leaving the remotes listed after the failing one without the new commits. Simply re-run the push once the host is reachable again; the remotes that did get the commits will just respond with Everything up-to-date. And you should never force-push to only one of the remotes, as that leaves the mirrors permanently out of sync with your local repository.

Avoid pulling too much

Related to multiple remotes, you should also be aware that git allows one to configure which branches to pull. By default a git clone will track all branches from the remote and pull everything, which in a typical open source project will bring in a lot of temporary development branches in vain.

Thus it is better to run git clone with the --single-branch and --branch parameters to fetch only the branch that matters, which in most cases is the main branch. That can be accomplished with:

git clone --single-branch --branch main https://github.com/ottok/debcraft.git

If a repository was already cloned, it can be configured to track only one branch with:

git config remote.upstream.fetch "+refs/heads/main:refs/remotes/upstream/main"
git fetch upstream
git config --get-all remote.upstream.fetch
+refs/heads/main:refs/remotes/upstream/main

If you later need to track more branches, you can configure them with commands such as:

git config --add remote.upstream.fetch "+refs/heads/3.2.y:refs/remotes/upstream/3.2.y"
git fetch upstream
git checkout 3.2.y

For additional details about any of the tips in this post I recommend reading the git man pages.

Now go and spread your code around

Distributing your code over multiple code forges costs you almost nothing in configuration, and in return you get availability, a choice of host for your collaborators, and freedom to migrate without a big bang. Add the push URLs to the remotes you already have, push once, and you are done.

The rest of the git fundamentals are covered in my other posts. If your commits are not yet polished, start with what makes a good git commit message and git commit messages by example. If you work on Debian packaging, Git-based collaboration in Debian explains why the Salsa merge request workflow is built the way it is, and Salsa merge request best practices covers the review process itself.

Maytham Alsudany: Briefly looking at DNS and nameservers under the hood

Mon, 28 Sep 2026 00:00:00 +0000

I've always known that the browser uses the Domain Name Resolution (DNS) system to convert domain names like aezign.com.au into raw IP addresses, but have never actually understood how it works, outside of making sure my network config uses 1.1.1.1 or 8.8.8.8 instead of the crappy one the ISP provides. In this article, I set out to understand what nameservers do, and how they help anything that uses the internet find the right records.

DNS in a nutshell

A well-used analogy is a phonebook; when you have someone's name and need to find their phone number, you look through the phonebook. Overall, DNS does the same thing: when you enter an address like example.com, your browser will contact a DNS server (the "phonebook") to determine its IP addresses. On Linux (or MacOS) systems, you can use dig on the command line to perform a DNS lookup and see what this looks like:

$ dig example.com

; <<>> DiG 9.20.29-1-Debian <<>> example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42782
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      A

;; ANSWER SECTION:
example.com.            221     IN      A       104.20.23.154
example.com.            221     IN      A       172.66.147.243

;; Query time: 20 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 21:07:50 AWST 2026
;; MSG SIZE  rcvd: 72

Here, you can see the DNS server being used is 1.1.1.1 (Cloudflare's DNS server), and that it found the IPs 104.20.23.154 and 172.66.147.243 associated with the domain name example.com. Your browser will then contact these IP addresses directly to load the website you are trying to open.

Configuring DNS servers

You can configure DNS servers through your operating system's network settings, and for some applications such as Firefox, with the application itself. If you don't manually set a DNS server, your computer will use the ones provided by your modem. If those are not configured, the default defined by the modem manufacturer or your ISP will be used.

The most well-used and reliable DNS servers you can use are Cloudflare's (1.1.1.1 and 1.0.0.1) and Google's (8.8.8.8 and 8.8.4.4). Having more than one DNS server means that if the first one in the list doesn't work or doesn't find the matching IPs for a domain name, it will move to the next one in the list, a backup DNS server.

DNS servers must be configured as IP addresses. If your computer tried to use a DNS server at a domain name, then where would your computer find the IP address for that domain name? It wouldn't be able to, as this is the exact gap that DNS servers fulfill.

Records

DNS is not used only to find IPs for a domain, but a whole host of other things. Collectively they are referred to as "records" (or "DNS records"). Each record is associated to a domain (e.g. example.com) or a subdomain (e.g. bar.example.com, foo.bar.example.com) Here are some of the most common and important types:

A - Map to an IPv4 address (e.g. 104.20.23.154).
This is the fundamental function of DNS: to map from a domain name to a server's IP address. Multiple A records leads to load balancing, where browsers will randomly select one of the returned IP addresses such that traffic is evenly split between them.
AAAA - Map to an IPv6 address (e.g. 2606:4700:10::6814:179a).
This serves the same purpose as A records but for IPv6. Multiple AAAA records results in the same load balancing behaviour. All modern websites should have both an A record for legacy compatibility, and an AAAA record to future-proof for the gradual shift towards IPv6 addresses.
CNAME - Alias to another domain name (e.g. example.com).
DNS servers will recursively lookup records for the aliased domain name until they reach an IP address (in an A or AAAA record).
MX - Specify a Mail Exchange server (e.g. mail.example.com).
This record tells email SMTP servers where to direct emails to. For instance, the MX record for aezign.com.au is mail.aezign.au; this directs SMTP servers like Gmail and Outlook to send emails to the mailserver running at mail.aezign.au. This also allows specifying a priority field, so that you can define multiple MX records (such as a main and a backup) and consumers will try to connect to the listed mailservers from lowest priority to highest.
TXT - Store arbitrary text data
This is most commonly used for site verification (for instance, to link your website to Google Search Console) and for email security measures like DKIM, DMARC, and SPF.
NS - Specify the nameservers for a domain (e.g. zeus.ns.cloudflare.com).
These authoritative nameservers are responsible for providing all the other record types when needed.

dig lets you query each of these. For instance, to list the MX records against aezign.com.au:

$ dig MX aezign.com.au

; <<>> DiG 9.20.29-1-Debian <<>> MX aezign.com.au
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28213
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;aezign.com.au.                 IN      MX

;; ANSWER SECTION:
aezign.com.au.          300     IN      MX      10 mail.aezign.au.

;; Query time: 104 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 22:04:58 AWST 2026
;; MSG SIZE  rcvd: 70

Here you can see there is only one mailserver configured for aezign.com.au, which is mail.aezign.au, and it has a priority of 10.

If you compare this against something like gmail.com:

$ dig MX gmail.com

; <<>> DiG 9.20.29-1-Debian <<>> MX gmail.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16538
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;gmail.com.                     IN      MX

;; ANSWER SECTION:
gmail.com.              2497    IN      MX      40 alt4.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      20 alt2.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      5 gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      10 alt1.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      30 alt3.gmail-smtp-in.l.google.com.

;; Query time: 120 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 22:06:04 AWST 2026
;; MSG SIZE  rcvd: 161

You can see that gmail.com has several mailservers configured as redundancies due to the Gmail's sheer scale. gmail-smtp-in.l.google.com has the highest priority of 5, so SMTP servers will attempt to contact that mailserver first, followed by alt1.gmail-smtp-in.l.google.com and so on.

Nameservers

Now there needs to be somewhere for DNS records against a domain name to be defined, right? This is where nameservers come in.

Nameservers are DNS servers that answer queries about the domains they are authoritative for i.e. the domains they are in charge of. For example, the authoritative nameservers for example.com are hera.ns.cloudflare.com and elliott.ns.cloudflare.com, which means Cloudflare's nameservers are the source of truth when looking up DNS records for example.com. You can check this with dig:

$ dig NS example.com

; <<>> DiG 9.20.29-1-Debian <<>> NS example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37717
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      NS

;; ANSWER SECTION:
example.com.            81837   IN      NS      hera.ns.cloudflare.com.
example.com.            81837   IN      NS      elliott.ns.cloudflare.com.

;; Query time: 140 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 23:27:19 AWST 2026
;; MSG SIZE  rcvd: 95

Nameservers are configured with your domain name's registrar. The nameserver you set dictates where your remaining DNS records will live. For example.com, this means you would configure all your records on Cloudflare's dashboard, since they are responsible for the domain's DNS records.

Recursive resolution

The DNS servers that our computers use follow a recursive resolution process behind-the-scenes to find the authoritative nameservers for a domain, followed by the records you are querying.

Finding the root nameservers

Due to the recursive nature of the resolution process, there needs to be a starting point: the root (.) nameservers. The resolver uses a fixed list of root nameservers called root hints issued by IANA (named.root), to locate and contact the root nameservers. Resolvers will have this provided to them initially, and can dynamically update it themselves by querying one of the root nameservers for the root NS records to obtain a fresh list. For instance, we can query 198.41.0.4 (a.root-servers.net) to obtain a new list of root nameservers:

$ dig @198.41.0.4 NS .

; <<>> DiG 9.20.29-1-Debian <<>> @198.41.0.4 NS .
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43677
;; flags: qr aa rd; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;.				IN	NS

;; ANSWER SECTION:
.			518400	IN	NS	l.root-servers.net.
.			518400	IN	NS	j.root-servers.net.
.			518400	IN	NS	f.root-servers.net.
.			518400	IN	NS	h.root-servers.net.
.			518400	IN	NS	d.root-servers.net.
.			518400	IN	NS	b.root-servers.net.
.			518400	IN	NS	k.root-servers.net.
.			518400	IN	NS	i.root-servers.net.
.			518400	IN	NS	m.root-servers.net.
.			518400	IN	NS	e.root-servers.net.
.			518400	IN	NS	g.root-servers.net.
.			518400	IN	NS	c.root-servers.net.
.			518400	IN	NS	a.root-servers.net.

;; ADDITIONAL SECTION:
l.root-servers.net.	518400	IN	A	199.7.83.42
l.root-servers.net.	518400	IN	AAAA	2001:500:9f::42
j.root-servers.net.	518400	IN	A	192.58.128.30
j.root-servers.net.	518400	IN	AAAA	2001:503:c27::2:30
f.root-servers.net.	518400	IN	A	192.5.5.241
f.root-servers.net.	518400	IN	AAAA	2001:500:2f::f
h.root-servers.net.	518400	IN	A	198.97.190.53
h.root-servers.net.	518400	IN	AAAA	2001:500:1::53
d.root-servers.net.	518400	IN	A	199.7.91.13
d.root-servers.net.	518400	IN	AAAA	2001:500:2d::d
b.root-servers.net.	518400	IN	A	170.247.170.2
b.root-servers.net.	518400	IN	AAAA	2801:1b8:10::b
k.root-servers.net.	518400	IN	A	193.0.14.129
k.root-servers.net.	518400	IN	AAAA	2001:7fd::1
i.root-servers.net.	518400	IN	A	192.36.148.17
i.root-servers.net.	518400	IN	AAAA	2001:7fe::53
m.root-servers.net.	518400	IN	A	202.12.27.33
m.root-servers.net.	518400	IN	AAAA	2001:dc3::35
e.root-servers.net.	518400	IN	A	192.203.230.10
e.root-servers.net.	518400	IN	AAAA	2001:500:a8::e
g.root-servers.net.	518400	IN	A	192.112.36.4
g.root-servers.net.	518400	IN	AAAA	2001:500:12::d0d
c.root-servers.net.	518400	IN	A	192.33.4.12
c.root-servers.net.	518400	IN	AAAA	2001:500:2::c
a.root-servers.net.	518400	IN	A	198.41.0.4
a.root-servers.net.	518400	IN	AAAA	2001:503:ba3e::2:30

;; Query time: 476 msec
;; SERVER: 198.41.0.4#53(198.41.0.4) (UDP)
;; WHEN: Mon Sep 28 00:01:08 AWST 2026
;; MSG SIZE  rcvd: 811

Querying the root nameservers

For example.com, the first step is to query the root (.) nameservers to find the nameservers for the .com top-level domain (TLD). Using a.root-servers.net again:

$ dig @198.41.0.4 NS com

; <<>> DiG 9.20.29-1-Debian <<>> @198.41.0.4 NS com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22528
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 27
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;com.				IN	NS

;; AUTHORITY SECTION:
com.			172800	IN	NS	l.gtld-servers.net.
com.			172800	IN	NS	j.gtld-servers.net.
com.			172800	IN	NS	h.gtld-servers.net.
com.			172800	IN	NS	d.gtld-servers.net.
com.			172800	IN	NS	b.gtld-servers.net.
com.			172800	IN	NS	f.gtld-servers.net.
com.			172800	IN	NS	k.gtld-servers.net.
com.			172800	IN	NS	m.gtld-servers.net.
com.			172800	IN	NS	i.gtld-servers.net.
com.			172800	IN	NS	g.gtld-servers.net.
com.			172800	IN	NS	a.gtld-servers.net.
com.			172800	IN	NS	c.gtld-servers.net.
com.			172800	IN	NS	e.gtld-servers.net.

;; ADDITIONAL SECTION:
l.gtld-servers.net.	172800	IN	A	192.41.162.30
l.gtld-servers.net.	172800	IN	AAAA	2001:500:d937::30
j.gtld-servers.net.	172800	IN	A	192.48.79.30
j.gtld-servers.net.	172800	IN	AAAA	2001:502:7094::30
h.gtld-servers.net.	172800	IN	A	192.54.112.30
h.gtld-servers.net.	172800	IN	AAAA	2001:502:8cc::30
d.gtld-servers.net.	172800	IN	A	192.31.80.30
d.gtld-servers.net.	172800	IN	AAAA	2001:500:856e::30
b.gtld-servers.net.	172800	IN	A	192.33.14.30
b.gtld-servers.net.	172800	IN	AAAA	2001:503:231d::2:30
f.gtld-servers.net.	172800	IN	A	192.35.51.30
f.gtld-servers.net.	172800	IN	AAAA	2001:503:d414::30
k.gtld-servers.net.	172800	IN	A	192.52.178.30
k.gtld-servers.net.	172800	IN	AAAA	2001:503:d2d::30
m.gtld-servers.net.	172800	IN	A	192.55.83.30
m.gtld-servers.net.	172800	IN	AAAA	2001:501:b1f9::30
i.gtld-servers.net.	172800	IN	A	192.43.172.30
i.gtld-servers.net.	172800	IN	AAAA	2001:503:39c1::30
g.gtld-servers.net.	172800	IN	A	192.42.93.30
g.gtld-servers.net.	172800	IN	AAAA	2001:503:eea3::30
a.gtld-servers.net.	172800	IN	A	192.5.6.30
a.gtld-servers.net.	172800	IN	AAAA	2001:503:a83e::2:30
c.gtld-servers.net.	172800	IN	A	192.26.92.30
c.gtld-servers.net.	172800	IN	AAAA	2001:503:83eb::30
e.gtld-servers.net.	172800	IN	A	192.12.94.30
e.gtld-servers.net.	172800	IN	AAAA	2001:502:1ca1::30

;; Query time: 772 msec
;; SERVER: 198.41.0.4#53(198.41.0.4) (UDP)
;; WHEN: Mon Sep 28 00:09:25 AWST 2026
;; MSG SIZE  rcvd: 828

Querying the TLD nameservers

Now the resolver has .com nameservers and their IPs. We can use one of these, such as 192.5.6.30 (a.gtld-servers.net) to find the nameservers for example.com:

$ dig @192.5.6.30 NS example.com

; <<>> DiG 9.20.29-1-Debian <<>> @192.5.6.30 NS example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37419
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 13
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;example.com.                   IN      NS

;; AUTHORITY SECTION:
example.com.            172800  IN      NS      hera.ns.cloudflare.com.
example.com.            172800  IN      NS      elliott.ns.cloudflare.com.

;; ADDITIONAL SECTION:
hera.ns.cloudflare.com. 172800  IN      A       108.162.192.162
hera.ns.cloudflare.com. 172800  IN      A       172.64.32.162
hera.ns.cloudflare.com. 172800  IN      A       173.245.58.162
hera.ns.cloudflare.com. 172800  IN      AAAA    2606:4700:50::adf5:3aa2
hera.ns.cloudflare.com. 172800  IN      AAAA    2803:f800:50::6ca2:c0a2
hera.ns.cloudflare.com. 172800  IN      AAAA    2a06:98c1:50::ac40:20a2
elliott.ns.cloudflare.com. 172800 IN    A       108.162.195.228
elliott.ns.cloudflare.com. 172800 IN    A       162.159.44.228
elliott.ns.cloudflare.com. 172800 IN    A       172.64.35.228
elliott.ns.cloudflare.com. 172800 IN    AAAA    2606:4700:58::a29f:2ce4
elliott.ns.cloudflare.com. 172800 IN    AAAA    2803:f800:50::6ca2:c3e4
elliott.ns.cloudflare.com. 172800 IN    AAAA    2a06:98c1:50::ac40:23e4

;; Query time: 80 msec
;; SERVER: 192.5.6.30#53(192.5.6.30) (UDP)
;; WHEN: Mon Sep 28 00:12:19 AWST 2026
;; MSG SIZE  rcvd: 359

Finding the domain's nameserver

The response tells the resolver that the nameservers for example.com are hera.ns.cloudflare.com and elliott.ns.cloudflare.com. Now since these Cloudflare nameservers are also .com domains and Cloudflare is so commonly used, the .com nameserver provides optional sibling glue records as defined in RFC 9471 to prevent further roundtrips and optimize the process.

If we ignore the sibling glue records provided, the resolver would have to ask the .com nameservers for the nameservers for cloudflare.com:

$ dig @192.5.6.30 NS cloudflare.com

; <<>> DiG 9.20.29-1-Debian <<>> @192.5.6.30 NS cloudflare.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40307
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 5, ADDITIONAL: 21
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cloudflare.com.                        IN      NS

;; AUTHORITY SECTION:
cloudflare.com.         172800  IN      NS      ns3.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns5.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns4.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns6.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns7.cloudflare.com.

;; ADDITIONAL SECTION:
ns3.cloudflare.com.     172800  IN      A       162.159.0.33
ns3.cloudflare.com.     172800  IN      A       162.159.7.226
ns3.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:21
ns3.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:7e2
ns5.cloudflare.com.     172800  IN      A       162.159.2.9
ns5.cloudflare.com.     172800  IN      A       162.159.9.55
ns5.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:209
ns5.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:937
ns4.cloudflare.com.     172800  IN      A       162.159.1.33
ns4.cloudflare.com.     172800  IN      A       162.159.8.55
ns4.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:121
ns4.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:837
ns6.cloudflare.com.     172800  IN      A       162.159.3.11
ns6.cloudflare.com.     172800  IN      A       162.159.5.6
ns6.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:30b
ns6.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:506
ns7.cloudflare.com.     172800  IN      A       162.159.4.8
ns7.cloudflare.com.     172800  IN      A       162.159.6.6
ns7.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:408
ns7.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:606

;; Query time: 163 msec
;; SERVER: 192.5.6.30#53(192.5.6.30) (UDP)
;; WHEN: Mon Sep 28 00:26:53 AWST 2026
;; MSG SIZE  rcvd: 573

Here, the .com nameserver provides in-domain glue records for cloudflare.com's nameservers. Without these, there would be a circular dependency, since the nameserver named is a subdomain of the domain being queried for. This is because nameservers are always defined by name, which means that in order to actually contact the nameserver, your computer needs to obtain its IP address with another DNS lookup.

Next, we'd use one of these nameservers, say ns3.cloudflare.com, to obtain the IP for hera.ns.cloudflare.com:

$ dig @162.159.0.33 hera.ns.cloudflare.com

; <<>> DiG 9.20.29-1-Debian <<>> @162.159.0.33 hera.ns.cloudflare.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16801
;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;hera.ns.cloudflare.com.                IN      A

;; ANSWER SECTION:
hera.ns.cloudflare.com. 86353   IN      A       108.162.192.162
hera.ns.cloudflare.com. 86353   IN      A       173.245.58.162
hera.ns.cloudflare.com. 86353   IN      A       172.64.32.162

;; Query time: 123 msec
;; SERVER: 162.159.0.33#53(162.159.0.33) (UDP)
;; WHEN: Mon Sep 28 01:11:37 AWST 2026
;; MSG SIZE  rcvd: 99

Querying the domain's authoritative nameserver

Now we've reached the authoritative nameserver for example.com! The last thing to do is to fetch the A record for example.com to obtain its server's IP address:

$ dig @108.162.192.162 example.com

; <<>> DiG 9.20.29-1-Debian <<>> @108.162.192.162 example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43082
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      A

;; ANSWER SECTION:
example.com.            300     IN      A       104.20.23.154
example.com.            300     IN      A       172.66.147.243

;; Query time: 123 msec
;; SERVER: 108.162.192.162#53(108.162.192.162) (UDP)
;; WHEN: Mon Sep 28 01:13:47 AWST 2026
;; MSG SIZE  rcvd: 72

At last, we've determined that the IP addresses of the servers behind example.com are 104.20.23.154 and 172.66.147.243. This matches our earlier lookup directly against your computer's configured DNS server.

The DNS servers your computer uses encapsulate this recursive resolution process behind the scenes, so that your computer only needs to make one round trip, and the servers can use their much faster data center connections and caching to optimize the process and make the query as fast as possible.

Checking DNS records

To check a website's records, the first thing to do is to ensure the domain name is pointed at the correct nameserver. For instance, aezign.com.au is supposed to use Cloudflare, since that is where all the DNS records have been set up. We can verify this using dig, (or alternatively with online tools like dnschecker.org):

$ dig NS aezign.com.au

; <<>> DiG 9.20.29-1-Debian <<>> NS aezign.com.au
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44172
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;aezign.com.au.                 IN      NS

;; ANSWER SECTION:
aezign.com.au.          86400   IN      NS      rosalie.ns.cloudflare.com.
aezign.com.au.          86400   IN      NS      zeus.ns.cloudflare.com.

;; Query time: 92 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Mon Sep 28 01:39:22 AWST 2026
;; MSG SIZE  rcvd: 100

If this is not set correctly, the DNS records you configure will not work, as resolvers will be fetching records from somewhere else. In most cases, you can update this in your domain registrar's settings. This is especially common for new domain names, which default to the registrar's nameservers; unless you plan to use their built-in DNS management, you'll need to point them to your chosen provider.

Now we can check that the DNS records configured match those your DNS server returns. For aezign.com.au, these are the MX and TXT records configured on Cloudflare.

The MX record and some TXT records configured for aezign.com.au on Cloudflare's dashboard.

We can check these using dig, and using the +short option to show only the content of the records.

$ dig MX aezign.com.au +short

10 mail.aezign.au.

$ dig TXT aezign.com.au +short

"google-site-verification=KFqTU5xH8fFf6OtszEL4oudfxple29Tm-TvxVtCWkAM"
"v=spf1 mx a:mail.aezign.au -all"

$ dig TXT _dmarc.aezign.com.au +short

"v=DMARC1;p=quarantine;sp=quarantine;adkim=r;aspf=r"

$ dig TXT aezign.com.au-2026._domainkey.aezign.com.au +short

"v=DKIM1; h=sha256; k=rsa; s=email; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzL04yXZgB72YkoxS+tLK//aWx65TS4UA3F0qJ7el68SEuD4ehmg+61Ta9iS31H6U074dnjyoPDeaiGBa7ToTNCtiIts4/ghD/8nrENROE6hQAwRmTK18ODDHrRDW73hWe6Dg4cK5vmXi82/wWRZU9SDKbme28IE9uCVir3lCkKYLs1" "j16gR1Sjqr6a2+3o+EeVXnLJ4wXmJMm7KCIdn7zv0t9Z1eYcw672PdpYPAMpGb8uUsgaDBsNSpTcupPkz4SWj6TrOB80CPHjWseVY8EOJeRsNKQ/8LFoQEBl4Rxtb3HAmu4UIxSZ4QMVOLnXz67e85mA5XjcNIsVMzaWaowwIDAQAB"

As we can see, this matches, which means that the nameservers for aezign.com.au are correct and the DNS records are what we intend them to be.

Note that if you've recently changed the nameserver or DNS records for your domain, it can take anywhere between 10 seconds and 24 hours for the changes to take effect and propagate across the different DNS servers globally. Tools like dnschecker.org can check your records on different DNS servers worldwide to see if they're reflecting your changes. The reason for this is caching: DNS servers like 1.1.1.1 will cache results so it doesn't have to do the full resolution process every time, and uses the Time-To-Live (TTL) you configure in your DNS records as a guideline for caching duration.

Reproducible Builds (diffoscope): diffoscope 332 released

Mon, 28 Sep 2026 00:00:00 +0000

The diffoscope maintainers are pleased to announce the release of diffoscope version 332. This version includes the following changes:

[ Chris Lamb ]
* Do not Build-Depend on GNU Guix. Thanks to Vagrant and Holger for the
  reports. (Closes: #1149132)

[ Guillaume Girol ]
* Update more tests to support new versions of Radare.
  (Closes: reproducible-builds/diffoscope#432)

You find out more by visiting the project homepage.

Maytham Alsudany: A Brief Explanation of DNS and Nameservers

Mon, 28 Sep 2026 00:00:00 +0000

The Domain Name System (DNS) is a fundamental piece of technology behind the modern internet. Thanks to its introduction in 1983, you're able to enter domain names like aezign.com.au instead of raw IP addresses in your browser's address bar and when sending emails. This article explains what it is, how it works, and how you can inspect your own website's DNS and ensure it is set up correctly.

DNS in a nutshell

$ dig example.com

; <<>> DiG 9.20.29-1-Debian <<>> example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42782
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      A

;; ANSWER SECTION:
example.com.            221     IN      A       104.20.23.154
example.com.            221     IN      A       172.66.147.243

;; Query time: 20 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 21:07:50 AWST 2026
;; MSG SIZE  rcvd: 72

Configuring DNS servers

Records

A - Map to an IPv4 address (e.g. 104.20.23.154).
This is the fundamental function of DNS: to map from a domain name to a server's IP address. Multiple A records leads to load balancing, where browsers will randomly select one of the returned IP addresses such that traffic is evenly split between them.
AAAA - Map to an IPv6 address (e.g. 2606:4700:10::6814:179a).
This serves the same purpose as A records but for IPv6. Multiple AAAA records results in the same load balancing behaviour. All modern websites should have both an A record for legacy compatibility, and an AAAA record to future-proof for the gradual shift towards IPv6 addresses.
CNAME - Alias to another domain name (e.g. example.com).
DNS servers will recursively lookup records for the aliased domain name until they reach an IP address (in an A or AAAA record).
MX - Specify a Mail Exchange server (e.g. mail.example.com).
This record tells email SMTP servers where to direct emails to. For instance, the MX record for aezign.com.au is mail.aezign.au; this directs SMTP servers like Gmail and Outlook to send emails to the mailserver running at mail.aezign.au. This also allows specifying a priority field, so that you can define multiple MX records (such as a main and a backup) and consumers will try to connect to the listed mailservers from lowest priority to highest.
TXT - Store arbitrary text data
This is most commonly used for site verification (for instance, to link your website to Google Search Console) and for email security measures like DKIM, DMARC, and SPF.
NS - Specify the nameservers for a domain (e.g. zeus.ns.cloudflare.com).
These authoritative nameservers are responsible for providing all the other record types when needed.

dig lets you query each of these. For instance, to list the MX records against aezign.com.au:

$ dig MX aezign.com.au

; <<>> DiG 9.20.29-1-Debian <<>> MX aezign.com.au
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28213
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;aezign.com.au.                 IN      MX

;; ANSWER SECTION:
aezign.com.au.          300     IN      MX      10 mail.aezign.au.

;; Query time: 104 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 22:04:58 AWST 2026
;; MSG SIZE  rcvd: 70

Here you can see there is only one mailserver configured for aezign.com.au, which is mail.aezign.au, and it has a priority of 10.

If you compare this against something like gmail.com:

$ dig MX gmail.com

; <<>> DiG 9.20.29-1-Debian <<>> MX gmail.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16538
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;gmail.com.                     IN      MX

;; ANSWER SECTION:
gmail.com.              2497    IN      MX      40 alt4.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      20 alt2.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      5 gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      10 alt1.gmail-smtp-in.l.google.com.
gmail.com.              2497    IN      MX      30 alt3.gmail-smtp-in.l.google.com.

;; Query time: 120 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 22:06:04 AWST 2026
;; MSG SIZE  rcvd: 161

Nameservers

Now there needs to be somewhere for DNS records against a domain name to be defined, right? This is where nameservers come in.

$ dig NS example.com

; <<>> DiG 9.20.29-1-Debian <<>> NS example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37717
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      NS

;; ANSWER SECTION:
example.com.            81837   IN      NS      hera.ns.cloudflare.com.
example.com.            81837   IN      NS      elliott.ns.cloudflare.com.

;; Query time: 140 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Sun Sep 27 23:27:19 AWST 2026
;; MSG SIZE  rcvd: 95

Recursive resolution

The DNS servers that our computers use follow a recursive resolution process behind-the-scenes to find the authoritative nameservers for a domain, followed by the records you are querying.

Finding the root nameservers

$ dig @198.41.0.4 NS .

; <<>> DiG 9.20.29-1-Debian <<>> @198.41.0.4 NS .
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43677
;; flags: qr aa rd; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;.				IN	NS

;; ANSWER SECTION:
.			518400	IN	NS	l.root-servers.net.
.			518400	IN	NS	j.root-servers.net.
.			518400	IN	NS	f.root-servers.net.
.			518400	IN	NS	h.root-servers.net.
.			518400	IN	NS	d.root-servers.net.
.			518400	IN	NS	b.root-servers.net.
.			518400	IN	NS	k.root-servers.net.
.			518400	IN	NS	i.root-servers.net.
.			518400	IN	NS	m.root-servers.net.
.			518400	IN	NS	e.root-servers.net.
.			518400	IN	NS	g.root-servers.net.
.			518400	IN	NS	c.root-servers.net.
.			518400	IN	NS	a.root-servers.net.

;; ADDITIONAL SECTION:
l.root-servers.net.	518400	IN	A	199.7.83.42
l.root-servers.net.	518400	IN	AAAA	2001:500:9f::42
j.root-servers.net.	518400	IN	A	192.58.128.30
j.root-servers.net.	518400	IN	AAAA	2001:503:c27::2:30
f.root-servers.net.	518400	IN	A	192.5.5.241
f.root-servers.net.	518400	IN	AAAA	2001:500:2f::f
h.root-servers.net.	518400	IN	A	198.97.190.53
h.root-servers.net.	518400	IN	AAAA	2001:500:1::53
d.root-servers.net.	518400	IN	A	199.7.91.13
d.root-servers.net.	518400	IN	AAAA	2001:500:2d::d
b.root-servers.net.	518400	IN	A	170.247.170.2
b.root-servers.net.	518400	IN	AAAA	2801:1b8:10::b
k.root-servers.net.	518400	IN	A	193.0.14.129
k.root-servers.net.	518400	IN	AAAA	2001:7fd::1
i.root-servers.net.	518400	IN	A	192.36.148.17
i.root-servers.net.	518400	IN	AAAA	2001:7fe::53
m.root-servers.net.	518400	IN	A	202.12.27.33
m.root-servers.net.	518400	IN	AAAA	2001:dc3::35
e.root-servers.net.	518400	IN	A	192.203.230.10
e.root-servers.net.	518400	IN	AAAA	2001:500:a8::e
g.root-servers.net.	518400	IN	A	192.112.36.4
g.root-servers.net.	518400	IN	AAAA	2001:500:12::d0d
c.root-servers.net.	518400	IN	A	192.33.4.12
c.root-servers.net.	518400	IN	AAAA	2001:500:2::c
a.root-servers.net.	518400	IN	A	198.41.0.4
a.root-servers.net.	518400	IN	AAAA	2001:503:ba3e::2:30

;; Query time: 476 msec
;; SERVER: 198.41.0.4#53(198.41.0.4) (UDP)
;; WHEN: Mon Sep 28 00:01:08 AWST 2026
;; MSG SIZE  rcvd: 811

Querying the root nameservers

For example.com, the first step is to query the root (.) nameservers to find the nameservers for the .com top-level domain (TLD). Using a.root-servers.net again:

$ dig @198.41.0.4 NS com

; <<>> DiG 9.20.29-1-Debian <<>> @198.41.0.4 NS com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22528
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 27
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;com.				IN	NS

;; AUTHORITY SECTION:
com.			172800	IN	NS	l.gtld-servers.net.
com.			172800	IN	NS	j.gtld-servers.net.
com.			172800	IN	NS	h.gtld-servers.net.
com.			172800	IN	NS	d.gtld-servers.net.
com.			172800	IN	NS	b.gtld-servers.net.
com.			172800	IN	NS	f.gtld-servers.net.
com.			172800	IN	NS	k.gtld-servers.net.
com.			172800	IN	NS	m.gtld-servers.net.
com.			172800	IN	NS	i.gtld-servers.net.
com.			172800	IN	NS	g.gtld-servers.net.
com.			172800	IN	NS	a.gtld-servers.net.
com.			172800	IN	NS	c.gtld-servers.net.
com.			172800	IN	NS	e.gtld-servers.net.

;; ADDITIONAL SECTION:
l.gtld-servers.net.	172800	IN	A	192.41.162.30
l.gtld-servers.net.	172800	IN	AAAA	2001:500:d937::30
j.gtld-servers.net.	172800	IN	A	192.48.79.30
j.gtld-servers.net.	172800	IN	AAAA	2001:502:7094::30
h.gtld-servers.net.	172800	IN	A	192.54.112.30
h.gtld-servers.net.	172800	IN	AAAA	2001:502:8cc::30
d.gtld-servers.net.	172800	IN	A	192.31.80.30
d.gtld-servers.net.	172800	IN	AAAA	2001:500:856e::30
b.gtld-servers.net.	172800	IN	A	192.33.14.30
b.gtld-servers.net.	172800	IN	AAAA	2001:503:231d::2:30
f.gtld-servers.net.	172800	IN	A	192.35.51.30
f.gtld-servers.net.	172800	IN	AAAA	2001:503:d414::30
k.gtld-servers.net.	172800	IN	A	192.52.178.30
k.gtld-servers.net.	172800	IN	AAAA	2001:503:d2d::30
m.gtld-servers.net.	172800	IN	A	192.55.83.30
m.gtld-servers.net.	172800	IN	AAAA	2001:501:b1f9::30
i.gtld-servers.net.	172800	IN	A	192.43.172.30
i.gtld-servers.net.	172800	IN	AAAA	2001:503:39c1::30
g.gtld-servers.net.	172800	IN	A	192.42.93.30
g.gtld-servers.net.	172800	IN	AAAA	2001:503:eea3::30
a.gtld-servers.net.	172800	IN	A	192.5.6.30
a.gtld-servers.net.	172800	IN	AAAA	2001:503:a83e::2:30
c.gtld-servers.net.	172800	IN	A	192.26.92.30
c.gtld-servers.net.	172800	IN	AAAA	2001:503:83eb::30
e.gtld-servers.net.	172800	IN	A	192.12.94.30
e.gtld-servers.net.	172800	IN	AAAA	2001:502:1ca1::30

;; Query time: 772 msec
;; SERVER: 198.41.0.4#53(198.41.0.4) (UDP)
;; WHEN: Mon Sep 28 00:09:25 AWST 2026
;; MSG SIZE  rcvd: 828

Querying the TLD nameservers

Now the resolver has .com nameservers and their IPs. We can use one of these, such as 192.5.6.30 (a.gtld-servers.net) to find the nameservers for example.com:

$ dig @192.5.6.30 NS example.com

; <<>> DiG 9.20.29-1-Debian <<>> @192.5.6.30 NS example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37419
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 13
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;example.com.                   IN      NS

;; AUTHORITY SECTION:
example.com.            172800  IN      NS      hera.ns.cloudflare.com.
example.com.            172800  IN      NS      elliott.ns.cloudflare.com.

;; ADDITIONAL SECTION:
hera.ns.cloudflare.com. 172800  IN      A       108.162.192.162
hera.ns.cloudflare.com. 172800  IN      A       172.64.32.162
hera.ns.cloudflare.com. 172800  IN      A       173.245.58.162
hera.ns.cloudflare.com. 172800  IN      AAAA    2606:4700:50::adf5:3aa2
hera.ns.cloudflare.com. 172800  IN      AAAA    2803:f800:50::6ca2:c0a2
hera.ns.cloudflare.com. 172800  IN      AAAA    2a06:98c1:50::ac40:20a2
elliott.ns.cloudflare.com. 172800 IN    A       108.162.195.228
elliott.ns.cloudflare.com. 172800 IN    A       162.159.44.228
elliott.ns.cloudflare.com. 172800 IN    A       172.64.35.228
elliott.ns.cloudflare.com. 172800 IN    AAAA    2606:4700:58::a29f:2ce4
elliott.ns.cloudflare.com. 172800 IN    AAAA    2803:f800:50::6ca2:c3e4
elliott.ns.cloudflare.com. 172800 IN    AAAA    2a06:98c1:50::ac40:23e4

;; Query time: 80 msec
;; SERVER: 192.5.6.30#53(192.5.6.30) (UDP)
;; WHEN: Mon Sep 28 00:12:19 AWST 2026
;; MSG SIZE  rcvd: 359

Finding the domain's nameserver

If we ignore the sibling glue records provided, the resolver would have to ask the .com nameservers for the nameservers for cloudflare.com:

$ dig @192.5.6.30 NS cloudflare.com

; <<>> DiG 9.20.29-1-Debian <<>> @192.5.6.30 NS cloudflare.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40307
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 5, ADDITIONAL: 21
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cloudflare.com.                        IN      NS

;; AUTHORITY SECTION:
cloudflare.com.         172800  IN      NS      ns3.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns5.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns4.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns6.cloudflare.com.
cloudflare.com.         172800  IN      NS      ns7.cloudflare.com.

;; ADDITIONAL SECTION:
ns3.cloudflare.com.     172800  IN      A       162.159.0.33
ns3.cloudflare.com.     172800  IN      A       162.159.7.226
ns3.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:21
ns3.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:7e2
ns5.cloudflare.com.     172800  IN      A       162.159.2.9
ns5.cloudflare.com.     172800  IN      A       162.159.9.55
ns5.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:209
ns5.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:937
ns4.cloudflare.com.     172800  IN      A       162.159.1.33
ns4.cloudflare.com.     172800  IN      A       162.159.8.55
ns4.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:121
ns4.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:837
ns6.cloudflare.com.     172800  IN      A       162.159.3.11
ns6.cloudflare.com.     172800  IN      A       162.159.5.6
ns6.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:30b
ns6.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:506
ns7.cloudflare.com.     172800  IN      A       162.159.4.8
ns7.cloudflare.com.     172800  IN      A       162.159.6.6
ns7.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:408
ns7.cloudflare.com.     172800  IN      AAAA    2400:cb00:2049:1::a29f:606

;; Query time: 163 msec
;; SERVER: 192.5.6.30#53(192.5.6.30) (UDP)
;; WHEN: Mon Sep 28 00:26:53 AWST 2026
;; MSG SIZE  rcvd: 573

Next, we'd use one of these nameservers, say ns3.cloudflare.com, to obtain the IP for hera.ns.cloudflare.com:

$ dig @162.159.0.33 hera.ns.cloudflare.com

; <<>> DiG 9.20.29-1-Debian <<>> @162.159.0.33 hera.ns.cloudflare.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16801
;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;hera.ns.cloudflare.com.                IN      A

;; ANSWER SECTION:
hera.ns.cloudflare.com. 86353   IN      A       108.162.192.162
hera.ns.cloudflare.com. 86353   IN      A       173.245.58.162
hera.ns.cloudflare.com. 86353   IN      A       172.64.32.162

;; Query time: 123 msec
;; SERVER: 162.159.0.33#53(162.159.0.33) (UDP)
;; WHEN: Mon Sep 28 01:11:37 AWST 2026
;; MSG SIZE  rcvd: 99

Querying the domain's authoritative nameserver

Now we've reached the authoritative nameserver for example.com! The last thing to do is to fetch the A record for example.com to obtain its server's IP address:

$ dig @108.162.192.162 example.com

; <<>> DiG 9.20.29-1-Debian <<>> @108.162.192.162 example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43082
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.                   IN      A

;; ANSWER SECTION:
example.com.            300     IN      A       104.20.23.154
example.com.            300     IN      A       172.66.147.243

;; Query time: 123 msec
;; SERVER: 108.162.192.162#53(108.162.192.162) (UDP)
;; WHEN: Mon Sep 28 01:13:47 AWST 2026
;; MSG SIZE  rcvd: 72

The DNS servers your computer uses employ this recursive resolution technique behind the scenes, so that your computer only needs to make one round trip, and the servers can use their much faster data center connections and caching to optimize the process and make the query as fast as possible.

Verify your DNS records

To check your website's records, the first thing you'll want to do is ensure your domain name is pointed at the correct nameserver. For instance, aezign.com.au is supposed to use Cloudflare, since that is where all the DNS records have been set up. We can verify this using dig, (or alternatively with online tools like dnschecker.org):

$ dig NS aezign.com.au

; <<>> DiG 9.20.29-1-Debian <<>> NS aezign.com.au
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44172
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;aezign.com.au.                 IN      NS

;; ANSWER SECTION:
aezign.com.au.          86400   IN      NS      rosalie.ns.cloudflare.com.
aezign.com.au.          86400   IN      NS      zeus.ns.cloudflare.com.

;; Query time: 92 msec
;; SERVER: 1.1.1.1#53(1.1.1.1) (UDP)
;; WHEN: Mon Sep 28 01:39:22 AWST 2026
;; MSG SIZE  rcvd: 100

Now we can check that the DNS records you've configured match those your DNS server returns. For aezign.com.au, these are the MX and TXT records configured on Cloudflare.

The MX record and some TXT records configured for aezign.com.au on Cloudflare's dashboard.

We can check these using dig, and using the +short option to show only the content of the records.

$ dig MX aezign.com.au +short

10 mail.aezign.au.

$ dig TXT aezign.com.au +short

"google-site-verification=KFqTU5xH8fFf6OtszEL4oudfxple29Tm-TvxVtCWkAM"
"v=spf1 mx a:mail.aezign.au -all"

$ dig TXT _dmarc.aezign.com.au +short

"v=DMARC1;p=quarantine;sp=quarantine;adkim=r;aspf=r"

$ dig TXT aezign.com.au-2026._domainkey.aezign.com.au +short

"v=DKIM1; h=sha256; k=rsa; s=email; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzL04yXZgB72YkoxS+tLK//aWx65TS4UA3F0qJ7el68SEuD4ehmg+61Ta9iS31H6U074dnjyoPDeaiGBa7ToTNCtiIts4/ghD/8nrENROE6hQAwRmTK18ODDHrRDW73hWe6Dg4cK5vmXi82/wWRZU9SDKbme28IE9uCVir3lCkKYLs1" "j16gR1Sjqr6a2+3o+EeVXnLJ4wXmJMm7KCIdn7zv0t9Z1eYcw672PdpYPAMpGb8uUsgaDBsNSpTcupPkz4SWj6TrOB80CPHjWseVY8EOJeRsNKQ/8LFoQEBl4Rxtb3HAmu4UIxSZ4QMVOLnXz67e85mA5XjcNIsVMzaWaowwIDAQAB"

As we can see, this matches, which means that the nameservers for aezign.com.au are correct and the DNS records are what we intend them to be.

Note that if you've recently changed the nameserver or DNS records for your domain, it can take anywhere between 10 seconds and 24 hours for the changes to take effect and propagate across the different DNS servers worldwide. Tools like dnschecker.org can check your records on different DNS servers worldwide to see if they're reflecting your changes. The reason for this is caching: DNS servers like 1.1.1.1 will cache results so it doesn't have to do the full resolution process every time, and uses the Time-To-Live (TTL) you configure in your DNS records as a guideline for caching duration.

Dima Kogan: Lunar terminator paradox

Sun, 27 Sep 2026 21:04:00 +0000

There's an optical illusion known by names like the "lunar terminator paradox". This has much discussion and descriptions online, but none made sense in my head, so I wrote this program to figure out what was going on. The paradox:

The moon is illuminated by the sun
After sunset, the sun is below, so we would expect the illuminated portion of the moon to point down, towards where the sun is
This isn't what always happens!

I was camping in the mountains with a friend recently. We were looking up at the sky, just after the sun has set. The moon was clearly pointing up.

After playing with this program, I have clarity: we're looking up at the moon from below. The most pathological case is a full moon. Let's say the moon is on the horizon: elevation=0. If we're looking at this low moon, and the moon is full, the sun is directly behind us. The moon is fully illuminated, and we see 100% of the moon disc lit up.

Now, what happens if the moon is not at the horizon, but higher up at the sky? Effectively, the sun is infinitely far away, so the same part of the moon is lit up. But we're now looking at the moon from below, and we would see some of the dark side on the bottom edge. I.e. the moon appears bright at the top, but has a dark slice missing at the bottom: it points up! Even at sunset.

This is the most clearly weird case. A half-moon has no paradoxical behavior, and the more full the moon, the more clearly we can observe the bright moon pointing up despite the sun being down.

I produce two plots. At 3/4-full moon at sunset we look at the moon as it rises from the horizon all the way up to the zenith:

If the moon is at the horizon (elevation = 0), we see the expected 3/4-lit disc. As the moon rises, we see more and more of its bottom, and thus more and more dark areas show up: It clearly points up at sunset!

We can also move the sun around. Let's say the moon is 60deg up; let's move the sun from new-moon to a full-moon:

In the darkest configuration, we can still see a lit crescent on the bottom: the illumination is all on the opposite side, but we can see a slice of the illuminated back side. As the sun swings around, we see more and more of the moon. At azimuth = 90deg, we have a half-lit moon. Past that, more and more of the moon is visible, always pointing up.

This was also a super interesting study of the current state of AI tools. As I was writing this and debugging, I would talk to Claude and Gemini about how this worked and what I should be seeing. They were both completely unable to comprehend this, and would make infinite circular arguments. Clearly they read some incomplete explanations on the internet (as I have), and lack the reasoning capability necessary to distill it into something resembling "understanding". AGI is not here yet.

Aquila Macedo Costa: Testing library transitions before they reach unstable

Sun, 27 Sep 2026 05:58:14 +0000

A library transition can affect many packages in Debian. I added a way for Salsa CI to rebuild the ones that depend on the changing library, so maintainers can test the transition before it reaches unstable.

The need for this became clear during a proposed Poppler transition. Poppler is a library for rendering PDFs. The reverse-dependency job I had added to Salsa CI queued 100 of 115 candidate rebuilds, even though only about 21 were relevant. The problem was documented in issue #571.

Before this change, ratt used every binary package produced by Poppler to decide what to rebuild. That also picked up packages unrelated to the library transition. The tracker listed the old and new library package names, so I used them to focus the selection.

_{The Poppler transition tracker identifies the old and new runtime library package names.}

I added -transition_affected to ratt to implement this selection. The option performs the scan against the selected archive indexes and injects locally built .deb files into each source rebuild. It expects a regex of dependency package names, not a complete Ben expression, so the tracker’s Affected expression must be adapted first.

I then integrated the mode into Salsa CI. Maintainers can enable transition-aware rebuilds by setting SALSA_CI_BUILD_REVERSE_DEPENDENCIES_TRANSITION_AFFECTED_REGEX. If the variable is unset, the pipeline keeps the existing selection.

_{A Poppler test showing the selected rebuild jobs. Three jobs reached the CI timeout, they were not confirmed package regressions.}

I also changed ratt to cover packages targeting experimental. By default, it resolves and rebuilds reverse dependencies from unstable while still injecting the locally built .deb files. This lets a maintainer test a transition staged in experimental against packages currently in unstable.

Together, these changes help maintainers focus CI on packages relevant to a library transition and review rebuild results before the new library reaches unstable.

Russ Allbery: Review: Ode to the Half-Broken

Sun, 27 Sep 2026 02:57:00 +0000

Review: Ode to the Half-Broken, by Suzanne Palmer

Publisher:	DAW
Copyright:	May 2026
ISBN:	0-7564-2013-X
Format:	Kindle
Pages:	441

Ode to the Half-Broken is a standalone post-apocalyptic (sort of) science fiction novel.

As this novel opens, the unnamed first-person protagonist is waking up in a bathtub in an abandoned building. They are covered in electromagnets and missing one leg.

Waking up involved a secure reboot from a protected core kernel, so it is immediately obvious that the protagonist is a robot. That also explains the electromagnets, which interfere with their ability to control their body. Or they would, if the protagonist didn't have long-dormant combat routines available to deploy EM shielding and free themselves from the bathtub. There are no immediate answers to why someone embedded a virus in the data attached to a scientific paper on ants, an act so precisely targeted that it had to be personal. Or what happened to their leg.

"There are a number of electromagnets in the next room," I say. I point. "Behind that wall with all the holes in it."

"Those are big holes. And fresh, too," the dog says. "I wonder what made them."

"Electromagnets experiencing sudden velocity."

The dog gives another of its short barks, and I am more convinced now it is laughing, though I was not attempting to be funny.

Ode to the Half-Broken has a classic science fiction beginning: in medias res in a future science fiction version of Earth where nothing is immediately explained, leaving the reader to work out the date and the setting. Helping us out is the protagonist, who is neither chatty nor very sociable with other characters but keeps up an analytical monologue about the world as they narrate events.

We are some decades into a grim future. The United States has largely collapsed. Large parts of New York City are dangerous to humans due to disease and radiation. Neither of those hazards bother the large number of sentient robots; their scarcity, and therefore economy, is instead based on power. Robots that control solar power stations act as low-level mob bosses, trading power for information or labor.

Our protagonist doesn't want to care about any of this. They retreated from the world long ago for a solitary life in the former New York Botanical Gardens studying ants. But they need a new leg and the best robot repair person nearby is a human woman outside of the city, so they reluctantly head in that direction, accompanied somewhat surprisingly by a cyborg dog.

The typical science fiction apocalypse is caused by something specific. Classically, that event is a nuclear war, but writers found various alternatives before, during, and after the Cold War era: alien invasions, meteor showers, plagues, sea level rise, and peak oil and general environmental collapse, among many others. Less common is a post-apocalyptic novel where the collapse comes from multiple overlapping crises and accumulating failures, from a general failure to meet what Adam Tooze and others call polycrisis. The first time I encountered that style of post-apocalyptic story was in Octavia Butler's Parable of the Sower. It was one of the choices that made (and still makes) that book feel so chillingly realistic.

The world background in Ode to the Half-Broken is shaped by that sort of polycrisis collapse. There is no one reason why New York City is a dangerous, irradiated ruin and society has collapsed into isolated and sometimes warring factions. It is not runaway artificial intelligence, or at least not directly; sentient robots were a late-stage innovation of the collapsing US civilization and a tool and accelerator of its many wars, but they were not the cause and may be a critical ingredient in building some functional replacement. Instead, society fell apart because we failed to address any of the growing problems and then turned on each other in the resulting ruins. The reader gets an idiosyncratic view of that collapse in flashback chapters intermixed with the main narrative of the initially unnamed robot protagonist, flashbacks told from the perspective of the man who invented the key component for robot sentience. As you would expect, those two narratives are linked. The reader will not discover how they are linked until late in the story.

This book could have been extremely depressing. It is not, which says a great deal about Palmer's skill in telling it. The clinical distance of the protagonist in the early chapters helps considerably: They have rejected involvement in this world and therefore can describe it in detached, factual terms, aided by the tendency of most robots in this story to be slightly more precise, logical, and verbose than the human characters. But as the protagonist's clinical distance fades, as it must to allow the story's emotional stakes to rise, Palmer fills this book with moments of beauty and hope. A former nuclear submarine that has become the mind of a subway car is a key early ally. A collective has turned the Hudson Bridge into a thriving if chaotic community. Self-regulating enclaves of humans and robots are working together to try to build a livable world. Robots oversee pollinator swarms that are attempting to restore plant life, for no reason other than that they like order and stability and see this as a way of restoring both. This is a grim, post-apocalyptic world that does not dwell on either the grimness or the apocalypse. It is instead full of small moments of hope, collaboration, and personal connection.

This is a story with villains, danger, pain, and risk. Despite the similar keywords and cover aesthetics, it bears little resemblance to Becky Chambers's philosophical Monk and Robot series. It is not, in any definition of the term, cozy; it's a post-apocalyptic adventure story about a robot and a dog making their way through a ruined civilization and fighting people who are trying to build something even worse on the rubble. But it's also charming and oddly happy. There are strong found-family vibes in the way that a party coalesces around the protagonist and eventually gives them a name, there is the quiet happiness of seeing a grumpy misanthrope slowly come out of their protective shell, and the rail mechs are an absolute delight.

Like a lot of stories of happy small-group anarchism, I didn't entirely believe the politics and have some qualms about the realism of the ending, although perhaps I should strive to be as optimistic as Palmer writes. The somewhat dry and fussily precise first-person narration will also not be to everyone's taste; it worked for me by the end of the book, but it took a bit of reading to get used to it. But those quibbles aside, this was quietly lovely. It's a satisfying science fiction adventure story in a world with disturbing parallels to the one we're living in, but which uses those parallels to focus on small-scale collective efforts to build something better. And all the small details of the world-building are delightful: the different tiers of robots and their odd behaviors, the machine sense of purpose, even the mix of suspicion and generosity. The plot has large-scale implications, but it was the human-level details that charmed me.

I still want another Fergus novel, but this was a highly successful foray outside of that series. Palmer has won two Hugos for her novellas, so I can't really say she's overlooked, but her novels aren't getting anywhere near the attention they deserve. Highly recommended.

There is plenty of world-building room here for a sequel, but Ode to the Half-Broken reaches a satisfying standalone conclusion. So far as I know, no sequel is currently planned.

Rating: 8 out of 10

Reproducible Builds (diffoscope): diffoscope 331 released

Fri, 25 Sep 2026 00:00:00 +0000

The diffoscope maintainers are pleased to announce the release of diffoscope version 331. This version includes the following changes:

[ Chris Lamb ]
* Support radare2 >= 5.9.0. (Closes: reproducible-builds/diffoscope#432)
* Update debian/tests/control.
* Update copyright years.

[ Christopher Baines ]
* Add support for .nar files via Guix.

You find out more by visiting the project homepage.

Russell Coker: Links September 2026

Thu, 24 Sep 2026 10:33:22 +0000

Bjorn Stahl of the Arcan project wrote an insightful blog post The Day of a new Command-Line Interface: Shell [1]. He does a really good job of identifying problems and strategies for dealing with them, the UI of the results isn’t suitable to what I do though.

Using sqlite as an executable format (replacement for ELF) is one of the wildest ideas I’ve seen in a while, it might actually have some good use cases too [2].

Andrew Dana Hudson wrote an interesting LongNow article about SciFi’s focus on space travel when it seems unlikely [3].

TheDriven has an informative article about the “Hands Off Our Fuel” astroturf campaign that uses farmers as the face of an attempt to give tax exemptions to mining companies [4].

The Conversation has an interesting article about the new Chinese regulations restricting access to AI systems to prevent emotional dependence and prevent minors from having virtual partners or relatives [5].

Elana Hashman wrote an informative blog post about Python virtualenvs, has useful information for people who aren’t Python experts and just need to get stuff done [6].

We need more systems in the NTP pool, I would consider doing this if I had a server with an IP address that won’t change and no risk of bandwidth throttling [7].

Cory Doctorow has some interesting thoughts on the CEO fetish for “AI” even though it is almost never doing any good [8].

Steve Rose wrote an insightful article for The Guardian about the tech fascists of Silicon Valley [9].

Jacqui Lambie calls Pauline Hanson an “angry little woman” and a “bloody coward”, One Nation hate the rule of law [10].

The Conversation has an interesting article about Regime Change, the book about Trump by Maggie Haberman and Jonathan Swan [11].

Elvira Barry wrote an insightful article about the many failures of the Russian legal system, it’s interesting to note that ALL those failures match things that the Trump regime is doing [12].

Pyotr Kurzin – Geopolitics YouTube channel has an interesting interview about “continental” vs “maritime” powers in the context of what the US and Russia are doing [13].

Maxinomica has an interesting video about how China obtained a monopoly on rare earth metals and what happens next [14].

Anarcat wrote an insightful blog post The people vs the AI overlords about the problems that “AI” software development is bringing [15].

John Goerzen wrote an interesting blog post discussing the issues related to LLM use in FOSS projects [16].

Cybernews has an article about an exploit for Samsung, Xiaomi, Oppo, and OnePlus phones due to bad OEM kernel drivers and bad OEM API proxies, no company should release devices with proprietry drivers [17].

Scott Santens wrote an insightful article about how retraining fails laid-off workers and why UBI is needed when workers get replaced by LLMs [18].

libroot has some information on the Snowden archive and why so little of it has been used by journalists, we need more answers about this [19].

Drew Devault’s list of Weird little guys of FOSS is interesting history about some people who are best avoided [20].

[1] https://tinyurl.com/ydye29ta
[2] https://tinyurl.com/26223e79
[3] https://longnow.org/ideas/space-dead/
[4] https://tinyurl.com/287rktuz
[5] https://tinyurl.com/25a9mag3
[6] https://hashman.ca/managing-venvs/
[7] https://dreamstation.systems/personal/ntppool.html
[8] https://tinyurl.com/2bzwm5d6
[9] https://tinyurl.com/25bj88ss
[10] https://tinyurl.com/2ywkupwv
[11] https://tinyurl.com/257umlg6
[12] https://tinyurl.com/2cjyev9l
[13] https://www.youtube.com/watch?v=y50uWvxGb-A
[14] https://www.youtube.com/watch?v=BXLGV0Sj0n8
[15] https://anarc.at/blog/2026-08-18-people-vs-ai-overlords/
[16] https://tinyurl.com/2a8pzj8j
[17] https://tinyurl.com/249oafcy
[18] https://tinyurl.com/28f5gdjv
[19] https://tinyurl.com/2cv3v9e7
[20] https://drewdevault.com/weird-guys/

Mike Gabriel: Looking for Golang + Fullstack Developer with interest in Civic Tech

Wed, 23 Sep 2026 20:16:37 +0000

Who?

Fre(i)e Software GmbH is looking for a senior Golang + fullstack developer who can handwrite code and act as meticulous code review partner for another senior developer in the company.

What?

Most of your work would result in Open Source contributions to the Voxit project [1], an online civic tech tool for digital participation.

How and Where?

The work can either be delivered on project agreement base via freelancing or via employment (option only available to developers resident in Germany, Austria or Poland).

What next?

If you are interested, please get in touch and provide your hourly rate to us and your average hours of availability per week.

[1] https://gitlab.com/voxit/

Reproducible Builds (diffoscope): diffoscope 330 released

Mon, 21 Sep 2026 00:00:00 +0000

The diffoscope maintainers are pleased to announce the release of diffoscope version 330. This version includes the following changes:

[ Chris Lamb ]
* Don't Build-Depend on apksigcopier as it has been removed from testing.
  (Closes: #1146852)

You find out more by visiting the project homepage.

Vincent Bernat: Bot-free self-hosted analytics with GoatCounter on NixOS

Sun, 20 Sep 2026 19:44:50 +0000

In 2016, I removed Google Analytics from this blog to avoid being complicit in feeding the biggest machine for harvesting personal data. Instead, I relied on GoAccess to analyze my server logs.¹ For the past couple of years, the statistics have made no sense, despite my attempts to filter bots: AI scrapers inflate the number of visitors to around 2,000 per day. Eventually, I settled on GoatCounter, an open-source, privacy-friendly web analytics platform. I replaced the JavaScript client to filter bots more aggressively and added a CSS fallback. To improve reliability, I implemented a local proxy running on each of the five web servers serving this blog. The rest of this post details how these pieces fit together and how I deploy them on NixOS. ❄️

Why GoatCounter?

GoatCounter does not collect personal data: instead of storing the reader’s IP address or relying on cookies, it creates a session identifier valid for 8 hours from the user agent and the IP address. Its feature set is modest but sufficient for a blog. If you want to look at the interface, GoatCounter’s author runs a public instance for his site. A hosted version lets you try it before running your own instance. With a single binary and an SQLite database, GoatCounter is one of the lightest self-hosted solutions. Privacy-friendly alternatives, in increasing order of complexity, include Umami, Plausible, and Rybbit.

Custom JavaScript client

GoatCounter includes a small JavaScript client—2,189 bytes minified and gzipped. It ships some features I don’t use: a visitor counter, tracking clicks, configurable settings, etc. I replace it with this function to register a hit:

const count = ({ event, title } = {}) => {
  const params = new URLSearchParams({
    p: event || location.pathname,
    t: title || document.title,
    r: document.referrer,
    q: location.search,
    s: document.documentElement.clientWidth,
    e: !!event,
    rnd: Math.random().toString(36).slice(2, 7),
  });
  fetch(`/count?${params}`, { keepalive: true }).catch(() => {});
};

To filter bots,² I go the extra mile by requiring a user interaction—an idea I stole from Bear Blog.

let sendHit = () => (sendHit = () => {}, count());
["touchmove", "mousemove", "keydown", "pointerdown"].forEach((eventName) =>
  document.addEventListener(eventName, sendHit, {
    once: true,
    passive: true,
  }),
);

If a reader has disabled JavaScript in their browser, I record the hit using a CSS image. The :hover pseudo-class loads it only after an interaction, another trick stolen from Bear Blog. About 2% of my visitors fit into this bucket.³

<!DOCTYPE html>
<html lang="en" class="nojs">
  <head>
    <script>
      // The JavaScript code for this blog requires ES6
      if ("noModule" in HTMLScriptElement.prototype)
        document.documentElement.classList.remove("nojs");
    </script>
  </head>
  <body>
  <!-- ... -->
    <style>
      .nojs body:hover {
        border-width: 0;
        border-image: url('/count?p=/en/blog/2026-kpi-goodhart&t=Building...&r=NoJS&e=false');
      }
    </style>
  </body>
</html>

Where GoAccess reported around 2,000 visitors a day, GoatCounter counts fewer than 200 humans.⁴ I assume AI scrapers use a low-effort approach: if the content is available without barriers, as on this blog, they don’t spawn a complex mechanized browser that could trigger a page view. Even crawlers running JavaScript, like Googlebot with its headless Chromium, do not interact with the page and never trigger the events I listen to. The interaction-based “proof of humanity” I use is likely to keep working.⁵

Local proxy

Five servers ~~across the world~~ in Europe and in North America serve the content of this website, but GoatCounter runs on only one of them. To avoid losing track of visitors when GoatCounter is down, I run a local proxy listening on the same /count endpoint. On each server, it stores the hits in memory with a buffer large enough to survive several days of downtime. It sends them in batches to the upstream backend using the /api/v0/count authenticated endpoint.

🖼 Servers on a map. web02 is in Paris, web03 in Helsinki, web04 in Nuremberg, web05 in Ashburn, web06 in Chicago.

I proposed the code for the proxy in pull request #909. GoatCounter’s maintainer declined to maintain so much code for such a niche use case. As a fellow open-source developer, I often hold the same position for my own projects: a one-time contributor effort may translate into a long-term maintainer commitment.

I expose the endpoint for the proxy on the domain of this website to evade ad blockers. This sounds like I don’t respect the reader’s choice, but as GoatCounter is privacy-friendly, I find it acceptable.

location = /count {
  access_log off;
  proxy_pass http://127.0.0.3:8087/count;
  proxy_pass_request_headers off;
  proxy_set_header Accept-Language $http_accept_language;
  proxy_set_header User-Agent $http_user_agent;
  proxy_set_header X-Real-Ip $remote_addr;
}

Deploying on NixOS

My web servers run NixOS, a declarative Linux distribution with built-in configuration management. I manage this small fleet with Colmena, a stateless deployment tool for NixOS. My configuration is available on GitHub.

Deploying applications in containers

For better isolation, each application runs inside an ephemeral lightweight container, powered by systemd-nspawn. Each container runs a stripped-down NixOS instance. A module wraps NixOS’s containers options to avoid repeating the same options for each application.⁶ The containers share their network namespace with the host: the additional isolation is not worth the increased complexity. For a smaller footprint, I also disable a few non-essential services.

{ config, lib, ... }:
let
  cfg = config.luffy.containers;
in
{
  # User-configurable settings for our custom module
  options.luffy.containers = lib.mkOption {
    default = { };
    description = "Ephemeral containers sharing the host network.";
    type = lib.types.attrsOf (lib.types.submodule {
      options = {
        config = lib.mkOption {
          type = lib.types.deferredModule;
          default = { };
          description = "NixOS configuration of the container.";
        };
      };
    });
  };

  # Translate our options to NixOS containers
  config = {
    containers = lib.mapAttrs
      (name: container: {
        ephemeral = true;
        autoStart = true;
        privateNetwork = false;
        extraFlags = [ "--resolv-conf=replace-host" ];
        config = {
          imports = [ container.config ];
          networking.firewall.enable = false;
          system.stateVersion = config.system.stateVersion;
          systemd.services = {
            console-getty.enable = false;
            systemd-logind.enable = false;
            systemd-oomd.enable = false;
          };
        };
      })
      cfg;
  };
}

To configure a GoatCounter instance running in a container and listening on 127.0.0.4:8088, we import the module⁷ and declare the container in the config.luffy.containers attribute set:

{ pkgs, config, ... }: {
  imports = [ ./modules/container.nix ];
  config.luffy.containers.goatcounter = {
    config = {
      services.goatcounter = {
        enable = true;
        address = "127.0.0.4";
        port = 8088;
        proxy = true;
      };
    };
  };
}

As the containers are ephemeral, we need to keep persistent data in directories on the host. We add a mounts option and ask NixOS’s containers to expose the configured directories through the bindMounts option.

{ config, lib, ... }:
let
  cfg = config.luffy.containers;
in
{
  options.luffy.containers = lib.mkOption {
    type = lib.types.attrsOf (lib.types.submodule {
      options = {
        mounts = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = [ ];
          description = "Host directories mounted read-write at the same place.";
        };
      };
    });
  };

  config = {
    containers = lib.mapAttrs
      (name: container: {
        bindMounts =
          lib.genAttrs container.mounts (path: { hostPath = path; isReadOnly = false; });
      })
      cfg;
  };
}

For example, to persist GoatCounter’s database in the /var/db/goatcounter directory on the host, we add the directory to the mounts option and alter the service definition to tell GoatCounter where the database is.

{ config, ... }:
let
  databaseDirectory = "/var/db/goatcounter";
in {
  config.luffy.containers.goatcounter = {
    mounts = [ databaseDirectory ];
    config = {
      services.goatcounter = {
        extraArgs = [ "-db=sqlite+${databaseDirectory}/db.sqlite" ];
      };
    };
  };
}

A container may also need some secrets. Colmena can upload secrets without storing them in the Nix store. We add a keys option to our containers. It takes an attribute set mapping secret names to the commands to populate them. Then, the module declares the required secrets to Colmena in the deployment.keys option, makes the container depend on the presence of the secrets, and exposes them to the container.

{ config, lib, ... }:
let
  cfg = config.luffy.containers;
in
{
  options.luffy.containers = lib.mkOption {
    type = lib.types.attrsOf (lib.types.submodule {
      options = {
        keys = lib.mkOption {
          type = lib.types.attrsOf (lib.types.listOf lib.types.str);
          default = { };
          description = "Secrets, as a command to run locally. They are mounted in /etc.";
        };
      };
    });
  };

  config = {
    # Colmena uploads each secret in `/var/keys` and make them available
    # to the group "keys".
    deployment.keys = lib.concatMapAttrs
      (_: container: lib.mapAttrs
        (_: keyCommand: {
          inherit keyCommand;
          group = "keys";
          permissions = "0640";
          destDir = "/var/keys";
        })
        container.keys)
      cfg;

    # The container can only start if the required secrets are available.
    systemd.services = lib.mapAttrs'
      (name: container:
        let
          units = map (key: "${key}-key.service") (lib.attrNames container.keys);
        in
        lib.nameValuePair "container@${name}" {
          requires = units;
          after = units;
        })
      cfg;

    # Mount each secret inside the container.
    containers = lib.mapAttrs
      (name: container: {
        bindMounts = lib.mapAttrs'
          (key: _: lib.nameValuePair "/etc/${key}" {
            hostPath = "/var/keys/${key}";
            isReadOnly = true;
          })
          container.keys;
      })
      cfg;
  };
}

For example, GoatCounter needs credentials to download the GeoIP database. I provide a local command to fetch the secret from my password manager and expose it inside the container through the /etc/goatcounter.env environment file.

{ pkgs, config, ... }: 
let
  keyCommand = variable: [
    "${pkgs.runtimeShell}"
    "-c"
    "pass show personal/nixops/secrets | grep '^${variable}='"
  ];
in {
  config.luffy.containers.goatcounter = {
    keys."goatcounter.env" = keyCommand "GOATCOUNTER_GEODB";
    config = {
      systemd.services.goatcounter.serviceConfig = {
        EnvironmentFile = "/etc/goatcounter.env";
        SupplementaryGroups = [ "keys" ];
      };
    };
  };
}

GoatCounter server

Nixpkgs already packages GoatCounter. By overriding the src and vendorHash attributes, I reuse its definition for my custom version with the proxy:

{ goatcounter, fetchFromGitHub }:
goatcounter.overrideAttrs (_: {
  src = fetchFromGitHub {
    owner = "vincentbernat";
    repo = "goatcounter";
    rev = "feature/proxy";
    hash = "sha256-dJRlQlFu3tjcEgabT1LEbyFrasJlhmYu4L/T7EkoNcY=";
  };
  vendorHash = "sha256-c9Q5OrbZR+q6pD3SgPPWe8JUzcZco1AVUKGaV61k5DE=";
})

I wrote a NixOS module to encapsulate GoatCounter: the container definition, the service definition, and the secrets. The module accepts the following options: package, serve.enable, serve.listenAddress, serve.port, and serve.databaseFile. I already detailed the container configuration in the previous section. In the end, I chose not to reuse the GoatCounter module from NixOS: it’s small, so it’s better to insulate my module from unexpected future changes.

{ config, pkgs, lib, ... }:
let
  cfg = config.luffy.goatcounter;
  databaseDirectory = builtins.dirOf cfg.serve.databaseFile;
  chown = "${pkgs.coreutils}/bin/chown -R";
in {
  config.luffy.containers.goatcounter = {
    config.systemd.services.goatcounter = {
      description = "GoatCounter Web Analytics";
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        EnvironmentFile = "/etc/goatcounter.env";
        SupplementaryGroups = [ "keys" ];
        DynamicUser = true;
        Restart = "always";
        ExecStart = lib.escapeShellArgs [
          (lib.getExe cfg.package)
          "serve"
          "-listen=${cfg.serve.listenAddress}:${toString cfg.serve.port}"
          "-tls=none"
          "-db=sqlite+${cfg.serve.databaseFile}"
          "-automigrate"
        ];
        # Transfer database ownership to dynamically assigned user "goatcounter".
        ExecStartPre = "+${chown} goatcounter:goatcounter ${databaseDirectory}";
        ReadWritePaths = databaseDirectory;
      };
    };
  };
}

The following snippet configures GoatCounter to listen on 127.0.0.4:8088:

{
  luffy.goatcounter = {
    serve = {
      enable = true;
      listenAddress = "127.0.0.4";
      port = 8088;
    };
  };
}

The last step is to configure nginx to expose GoatCounter on the Internet. I disable the /count endpoint as the local proxy handles it.

{ config, ... }:
let
  cfg = config.luffy.goatcounter.serve;
in
{
  services.nginx.virtualHosts."goatcounter.luffy.cx" = {
    forceSSL = true;
    locations = {
      "/" = {
        proxyPass = "http://${cfg.listenAddress}:${toString cfg.port}";
      };
      "= /count".extraConfig = ''
        return 404;
      '';
    };
  };
}

GoatCounter proxy

The same NixOS module configures the local proxy, with the following options: proxy.enable, proxy.listenAddress, proxy.port, and proxy.site—the site receiving the batches of page views. The local proxy has no persistent data, but it needs the API key to authenticate to the main GoatCounter instance: its container uses the keys option but not the mounts option.

{ config, pkgs, lib, ... }:
let
  cfg = config.luffy.goatcounter;
  keyCommand = _: [ "…" ];
in
{
  config.luffy.containers.goatcounter-proxy = {
    keys."goatcounter-proxy.env" = keyCommand "GOATCOUNTER_API_KEY";
    config.systemd.services.goatcounter = {
      description = "GoatCounter Proxy.";
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        EnvironmentFile = "/etc/goatcounter-proxy.env";
        SupplementaryGroups = [ "keys" ];
        DynamicUser = true;
        Restart = "always";
        ExecStart = lib.escapeShellArgs [
          (lib.getExe cfg.package)
          "proxy"
          "-site=${cfg.proxy.site}"
          "-listen=${cfg.proxy.listenAddress}:${toString cfg.proxy.port}"
          "-ratelimit=10/1"  # 10 requests per second per IP
        ];
      };
    };
  };
}

For each server, I enable the local proxy with the following snippet. The nginx configuration shown earlier exposes the /count endpoint under the same domain as my blog.

{
  luffy.goatcounter = {
    proxy = {
      enable = true;
      site = "goatcounter.luffy.cx";
      listenAddress = "127.0.0.3";
      port = 8087;
    };
  };
}

Backup of the SQLite database with Litestream

Litestream is a streaming replication tool for SQLite databases. It compresses the changes committed to the write-ahead log (WAL) next to the database and sends them to a remote destination. I encapsulate its configuration in a NixOS module, which takes an attribute set databases mapping a name to the path of the database to back up.

Litestream also runs in a container. I mount the databases to replicate, as well as the secrets to push the backups to a Hetzner storage box using SFTP:

{ config, pkgs, lib, ... }:
let
  cfg = config.luffy.litestream;
  databaseDirs = lib.unique (map builtins.dirOf (builtins.attrValues cfg.databases));
in
{
  config = lib.mkIf (cfg.databases != { }) {
    luffy.containers.litestream = {
      mounts = databaseDirs;
      keys."litestream.env" = [
        "${pkgs.runtimeShell}"
        "-c"
        "pass show personal/nixops/secrets | grep '^SQLITE_BACKUP_'"
      ];
    };
  };
}

Inside the container, I configure Litestream through NixOS’s services.litestream options:

full snapshots every day, kept for 15 days,
three levels of compaction for transaction files: 5 minutes, 30 minutes, and 3 hours,
auto-recovery,⁸
replica stored in a directory matching the host name, and
credentials read from /etc/litestream.env and exposed through variable expansion.

{ config, pkgs, lib, ... }:
let
  cfg = config.luffy.litestream;
in
{
  config.luffy.containers.litestream = {
    config = {
      # The databases belong to dynamically allocated users, whose UID is
      # not known here, so Litestream runs as root.
      systemd.services.litestream.serviceConfig = {
        User = lib.mkForce "root";
        Group = lib.mkForce "root";
      };
      # Use NixOS service.
      services.litestream = {
        enable = true;
        environmentFile = "/etc/litestream.env";
        settings = {
          auto-recover = true;
          snapshot = {
            interval = "24h";
            retention = "360h";
          };
          levels = [
            { interval = "5m"; }
            { interval = "30m"; }
            { interval = "3h"; }
          ];
          dbs = lib.mapAttrsToList
            (name: path: {
              inherit path;
              replica = {
                type = "sftp";
                host = "\${SQLITE_BACKUP_HOST}";
                user = "\${SQLITE_BACKUP_USER}";
                password = "\${SQLITE_BACKUP_PASSWORD}";
                host-key = "\${SQLITE_BACKUP_HOSTKEY}";
                path = "${config.networking.hostName}/${name}";
              };
            })
            cfg.databases;
        };
      };
    };
  };
}

To back up GoatCounter’s database, I declare a goatcounter attribute in luffy.litestream.databases, set to the database path:

{ config, ... }:
let
  cfg = config.luffy.goatcounter.serve;
in
{
  luffy.litestream.databases.goatcounter = cfg.databaseFile;
}

On the SFTP server, we can inspect Litestream’s work, with the compacted transactions and the full snapshots:

❯ ls web02/goatcounter/ltx
web02/goatcounter/ltx/0
web02/goatcounter/ltx/1
web02/goatcounter/ltx/2
web02/goatcounter/ltx/3
web02/goatcounter/ltx/9
❯ ls -lh web02/goatcounter/ltx/1
29.1K Sep  5 01:25 0000000000003f2a-0000000000003f2b.ltx
72.4K Sep  5 02:03 0000000000003f2c-0000000000003f2d.ltx
63.3K Sep  5 02:24 0000000000003f2e-0000000000003f2f.ltx
[…]
❯ ls -lh web02/goatcounter/ltx/9
 8.5M Sep  5 02:00 0000000000000001-0000000000003f2b.ltx
 8.5M Sep  6 02:03 0000000000000001-0000000000004008.ltx
 8.6M Sep  7 02:03 0000000000000001-00000000000043a8.ltx
[…]

We can restore the database from the backup with a few shell commands. First, we stop the containers. Then, we move the damaged database away, invoke litestream restore from the right environment, and restart the containers.⁹

# systemctl stop container@goatcounter container@litestream
# mv /var/db/goatcounter/db.sqlite{,.old}
# ( . /etc/nixos-containers/litestream.conf ; 
>   set -a ; . /var/keys/litestream.env ; set +a ;
>   $SYSTEM_PATH/sw/bin/litestream \
>     restore -config $SYSTEM_PATH/etc/litestream.yml /var/db/goatcounter/db.sqlite)
# ls -lh /var/db/goatcounter/db.sqlite
-rw-r--r-- 1 root root 20M Sep 20 07:33 /var/db/goatcounter/db.sqlite
# systemctl start container@goatcounter container@litestream

Ten years after removing Google Analytics, JavaScript-based analytics is back on this blog, but without storing cookies or IP addresses, and without involving a third party. I still write for myself first, notably because it lets me dig into a topic and refer back to it years later. But knowing a bit more about my fellow human readers is a nice bonus, even the ones disabling JavaScript. 🐐

Nginx scrambles IP addresses before storing them, thanks to the ipscrub nginx module. ↩
GoatCounter already filters some bots based on the user agent or the IP address. But AI scrapers lie about their user agent and hide behind residential proxies. ↩
Without JavaScript, I cannot send the real referrer. I insert “NoJS” instead. ↩
I am missing the humans reading the RSS feed. I am not comfortable adding a tracking pixel, and bots are likely to fetch it, compromising the statistics. I’ll live without counting these readers. ↩
In February 2025, I tested another CSS-only approach without the interaction trick: each page loaded an empty image as a background. Over a month, it recorded up to ten times fewer page views than the nginx logs, even after removing user agents identifying as bots. Compared to this experiment, GoatCounter counts about three times fewer views, 18 months later. As the time ranges differ, this is not an apples-to-apples comparison, but it gives a hint about how efficient bot filtering is. ↩
A NixOS module is a function receiving the configuration of the whole system as config and returning three attributes:
- imports adds other modules to import,
- options declares user-configurable settings, each with a type and a default value, and
- config sets values for options declared by any module, like containers from NixOS.
If a module does not need to declare options, you can return the config attribute set directly. When a module does not require any argument, you can define it as an attribute set instead. ↩
Most of the time, you don’t need an explicit import. NixOS automatically imports the modules shipped with Nixpkgs. For my own modules, some machinery also imports them automatically. ↩
Litestream warns against using the auto-recover option as it can cause data loss. But I don’t properly monitor my servers and I prefer uninterrupted backups to a slight chance of losing the last few records. ↩
In my case, the process is slow: around 20 minutes for a 20 MiB database. You can test by restoring to a copy with the -o option, but you still need to stop the Litestream container. ↩

Andrew Cater: Debian 11 is at end of life from Long Term Support

noreply@blogger.com (Andrew Cater) — Sun, 20 Sep 2026 15:04:40 +0000

Lots of posts in the debian-user mailing list complaining about updates with Debian 11.11 suddenly failing.

See Debian 11 Long Term Support reaches end-of-life

August 31st, 2026

The Debian Long Term Support (LTS) Team hereby announces that Debian 11 bullseye support has reached its end-of-life today, 31 August 2026, five years after its initial release on 14 August 2021.

Starting in September, Debian will not provide further security updates for Debian 11. A subset of bullseye packages will be supported by external parties. Detailed information can be found at Extended LTS.

The Debian LTS Team is currently providing security support for Debian 12 bookworm, the current oldstable release. Thanks to the combined efforts of different teams including the Security Team, the Release Team, and the LTS Team, the Debian 12 life cycle encompasses five years. Debian 12 will receive Long Term Support until 30 June 2028. The supported architectures in Debian 12 LTS are amd64, i386, arm64, armhf and ppc64el.

For further information about using bookworm LTS and upgrading from bullseye LTS, please refer to LTS/Using.

Debian and its LTS Team would like to thank all contributing users, developers, sponsors and other Debian teams who are making it possible to extend the life of previous stable releases, and who have made Bullseye LTS a success.

If you rely on Debian LTS, please consider joining the team, providing patches, testing or funding the efforts.

Ludovic Rousseau: New version of libccid: 1.8.4

Sun, 20 Sep 2026 13:31:26 +0000

I have just released version 1.8.4 of libccid the Free Software CCID class smart card reader driver.

Changes:

1.8.4 - 20 September 2026, Ludovic Rousseau

Add support of
- THALES PKI Transaction Pad
fix some minor issues found by an AI tool
Some other minor improvements

Freexian Collaborators: Monthly report about Debian Long Term Support, August 2026 (by Thorsten Alteholz)

Sun, 20 Sep 2026 00:00:00 +0000

The Debian LTS Team, funded by Freexian’s Debian LTS offering, is pleased to report its activities for August.

Activity summary

During the month of August, 19 contributors have been paid to work on Debian LTS (links to individual contributor reports are located below).

The team released 58 DLAs fixing 1885 CVEs.

Debian 11 (“bullseye”), which has reached the end of its Long Term Support on 31 August 2026, will now get security support from Freexian under the Extended LTS offer.

The team published several notable updates:

chromium (DLA 4710-1), uploaded by Emilio, to fix 375 security flaws in bookworm, including issues that could lead to arbitrary code execution. Further DLA 4728-1, uploaded by Emilio as well, fixed additional 41 security issues in bookworm and DLA 4739-1 fixed 5 issues. Last but not least, DLA 4749-1 fixed another 15 issues and DLA 4758-1 fixed another 7 issues.
ruby2.7 (DLA 4716-1), uploaded by Abhijith, to fix four security flaws in bookworm, including issues that could lead to arbitrary code execution.
several DLAs (DLA 4717-1, DLA 4720-1, DLA 4723-1, DLA 4724-1, DLA 4745-1) have been uploaded by Ben and Emilio to fix myriad security flaws in different versions of the linux kernel (5.10.262-1, 6.1.180-1, 6.12.100-1~deb12u1, 6.12.101-1~deb12u1) in bullseye and bookworm.
7zip (DLA 4718-1) and p7zip (DLA 4719-1), uploaded by Sylvain, to fix multiple security flaws in bookworm and bullseye, including issues that could yield to remote code execution.
ca-certificates (DLA 4726-1), uploaded by Bastien to add some new trusted certificates to bookworm and bullseye, but also remove some untrusted ones.
thunderbird (DLA 4727-1 and DLA 4754-1), uploaded by Emilio to fix 35 and 31 issues in bookworm and bullseye.
nss (DLA 4729-1), uploaded by Jochen to fix a vulnerability in bookworm and bullseye that could yield to arbitrary code execution.
libgd2 (DLA 4731-1), uploaded by Guilhem to fix a vulnerability in bookworm and bullseye that could yield to arbitrary code execution if a malformed GIF file is processed.
xorg-server (DLA 4737-1 and DLA 4738-1), uploaded by Arnaud to fix several vulnerabilities in bookworm and bullseye.
postgresql-15 (DLA 4740-1), uploaded by Carlos Henrique Lima Melara to fix 26 vulnerabilities in bookworm.
unzip (DLA 4741-1), uploaded by Andrej to fix a vulnerability in bookworm and bullseye that could yield to arbitrary code execution.
firefox-esr (DLA 4750-1), uploaded by Emilio to fix 31 vulnerabilities in bookworm and bullseye that could potentially result in arbitrary code execution, privilege escalation or information disclosure.
nvidia-graphics-drivers (DLA 4752-1 and DLA 4753-1), uploaded by Tobias to fix lots of vulnerabilities in bookworm and bullseye.
roundcube (DLA 4760-1), uploaded by Guilhem to fix ten vulnerabilities in bookworm and bullseye that could potentially result in remote code execution or information disclosure.

Contributions from outside the LTS Team:

We are greatly thankful for the contributions from people outside the LTS Team:

Salvatore Bonaccorso released a libyaml-syck-perl security update (DLA 4730-1), to fix a denial of service and potentially arbitrary code execution.
Thomas Goirand released a neutron security update (DLA 4735-1).
Thomas Goirand released an ironic security update (DLA 4743-1).
Thomas Goirand released a designate security update (DLA 4751-1), to fix a denial of service or DNS hijacking.

The LTS Team has also contributed with updates to the latest Debian releases:

xrdp (DSA 6469-1), prepared by Abhijith to address privilege escalation and arbitrary code execution related flaws.

Other contributions:

Besides the work on security updates, different documentation and tooling changes were needed. This work was mainly done by Sylvain.

Individual Debian LTS contributor reports

Thanks to our sponsors

Sponsors that joined recently are in bold.

Platinum sponsors:
- Toshiba Corporation (for 131 months)
- Civil Infrastructure Platform (CIP) (for 99 months)
- VyOS Inc (for 64 months)
Gold sponsors:
- F. Hoffmann-La Roche AG (for 142 months)
- CONET Deutschland GmbH (for 125 months)
- University of Oxford (for 81 months)
- EDF SA (for 53 months)
- Dataport AöR (for 28 months)
- CERN (for 26 months)
Silver sponsors:
- Domeneshop AS (for 146 months)
- Nantes Métropole (for 140 months)
- Akamai - Linode (for 136 months)
- Univention GmbH (for 132 months)
- Université Jean Monnet de St Etienne (for 132 months)
- Ribbon Communications, Inc. (for 126 months)
- Exonet B.V. (for 116 months)
- Leibniz Rechenzentrum (for 110 months)
- Ministère de l’Europe et des Affaires Étrangères (for 94 months)
- Dinahosting SL (for 81 months)
- Upsun Formerly Platform.sh (for 76 months)
- Moxa Inc. (for 69 months)
- sipgate GmbH (for 67 months)
- OVH US LLC (for 65 months)
- Tilburg University (for 65 months)
- GSI Helmholtzzentrum für Schwerionenforschung GmbH (for 56 months)
- THINline s.r.o. (for 29 months)
- Copenhagen Airports A/S (for 23 months)
- Conseil Départemental de l’Isère (for 9 months)
- CEOS GmbH
Bronze sponsors:
- Seznam.cz, a.s. (for 147 months)
- Evolix (for 146 months)
- Linuxhotel GmbH (for 144 months)
- Intevation GmbH (for 143 months)
- WAAYS (for 142 months)
- Megaspace Internet Services GmbH (for 141 months)
- Greenbone AG (for 140 months)
- NUMLOG (for 140 months)
- WinGo AG (for 139 months)
- Entr’ouvert (for 131 months)
- Adfinis AG (for 128 months)
- Plat’Home (for 125 months)
- Laboratoire LEGI - UMR 5519 / CNRS (for 123 months)
- Tesorion (for 123 months)
- Bearstech (for 114 months)
- LiHAS (for 114 months)
- Catalyst IT Ltd (for 109 months)
- Demarcq SAS (for 103 months)
- Université Grenoble Alpes (for 89 months)
- TouchWeb SAS (for 81 months)
- SPiN AG (for 78 months)
- CoreFiling (for 74 months)
- Observatoire des Sciences de l’Univers de Grenoble (for 65 months)
- Tem Innovations GmbH (for 60 months)
- WordFinder.pro (for 60 months)
- CNRS DT INSU Résif (for 59 months)
- Alter Way (for 52 months)
- SOBIS Software GmbH (for 26 months)
- Tuxera Inc. (for 18 months)
- OPM-OP AS (for 9 months)
- LU-CIX Management G.I.E.

Ludovic Rousseau: New version of pcsc-lite: 2.5.2

Sat, 19 Sep 2026 15:17:57 +0000

I have just released a new version of pcsc-lite 2.5.2.

pcsc-lite is a Free Software implementation of the PC/SC (also known as WinSCard) API for Unix systems. It provides an API for using smart cards and smart card readers.

Changes:

2.5.2: Ludovic Rousseau 19 September 2026

hotplug_libudev: rescan "serial" readers in HPReCheckSerialReaders()
fix minor issues found by AI tool

Kentaro Hayashi: Building with dh-bazel, buildsystem support for debhelper experiment updates

Sat, 19 Sep 2026 08:33:44 +0000

Introduction

After bazel-bootstrap 7.7.1 was landed into Debian unstable, I'm working on packaging newer Mozc (Most famous Japanese input method editor) with Bazel.

Here is the blog entry initial efforts to build Mozc with Bazel at that time.

kenhys.hatenablog.jp

Then, I've shared implementing PoC dh-bazel experiment. See why dh-bazel is needed, and prototype about dh-bazel.

kenhys.hatenablog.jp

As a Bazel beginner, want to know what should pass to Bazel, what should not pass to Bazel.

What is improved in recent dh-bazel?

In the previous versions of dh-bazel, it supports only basic features to build with Bazel as a thin wrapper.

%:
        dh $@ --buildsystem=bazel

override_dh_auto_build:
        dh_auto_build -- //:hello

Now, with recent changes, it supports the following environment variables to resolve required system libraries in dynamically.

salsa.debian.org

DH_BAZEL_OVERRIDE_MODULE

It search the specified modules from bundled dummy modules in dh-bazel. It accept ',' separated paramesters. (e.g. DH_BAZEL_OVERRIDE_MODULE=zlib,zstd)

dh-bazel bundles abseil-cpp, apple_support, buildozer, lz4, openssl, protobuf, rules_android_ndk, rules_apple, rules_swift, zlib and zstd as dummy modules to linking system libraries.

Now you can use it in debian/rules like this:

#!/usr/bin/make -f
# -*- makefile -*-
#

export DH_BAZEL_OVERRIDE_MODULE=zlib
export DH_VERBOSE=1

%:
        dh $@ --buildsystem=bazel --without=single-binary

override_dh_auto_build:
        dh_auto_build -- //:hello

It is impossible to cover all of system libraries in Debian, so in that case, please consider to use the following DH_BAZEL_PKGCONF_MODULE.

DH_BAZEL_PKGCONF_MODULE

It search the specified modules with pkgconf. It is useful when there is no bundled modules in dh-bazel if you want. It accept ',' separated paramesters. (e.g. DH_BAZEL_PKGCONF_MODULE=gtk4-x11,gtk4-unix-print).

If DH_BAZEL_PKGCONF_MODULE could not match, then dh-bazel fallback to dig into Build-Depends: field in debian/control. Note that if it is not deterministic (e.g. -dev package provides multiple .pc files) dh-bazel gives up fallback with pkgconf.

Now you can use it in debian/rules like this:

#!/usr/bin/make -f
# -*- makefile -*-
#

export DH_BAZEL_PKGCONF_MODULE=gtk4-x11,gtk4-unix-print
export DH_VERBOSE=1

%:
        dh $@ --buildsystem=bazel --without=single-binary

override_dh_auto_build:
        dh_auto_build -- //:hello

Conclusion

dh-bazel is still in very early stage prototype, but it resolves some sort of packaging glitches a bit by bit.

I hope that it will help package maintainer using Bazel. (dh-bazel is not uploaded into debian/unstable yet, so stay tuned!)

Paul Tagliamonte: Why Write?

Fri, 18 Sep 2026 17:05:00 +0000

As a graduate of a liberal arts university, I wound up, unsurprisingly, taking a lot of classes in every possible academic discipline. Thinking back to the person that I was going into university, I don’t think I would have chosen to take them – after all, my degree was in the sciences; I’d have been stoked to do nothing more than wall-to-wall computer science until I ran out of coursework and filled the rest of my hours with research and independent studies with my professors (which, I guess I did actually do, just not as much as I would have otherwise).

Even this blog’s CSS theme (now 18 years old and starting to look it) was something I wrote after receiving and repeatedly re-reading a tattered third-hand copy of “The Laws of Thought” by George Boole. It was gifted to me by a college friend majoring in philosophy while I was crashing at his rental on the beach. He gave it to me because he knew I “liked that shit” and, while it was definitely computer science in nature, I would not have read it otherwise. I have vivid memories of sleeping on his la-z-boy surrounded by towers of books he was working through. He went on to do incredible work, getting his PhD, doing research, brilliant writing – his death in 2023 has robbed humanity of more time with him. “The Laws of Thought” sits behind me in my office, and is one of my most valued possessions.

My friends mean more to me than I could ever express, and I definitely don’t show it enough. Each of my classes made me a more thoughtful person. My professors made me a better, more well-rounded person – and a person who attempts to live up to the oft repeated credo of being “men and women for others”. I did the best I could, even though I was never a particularly good student. Without liberal arts, I don’t think I would, dispositionally, have been capable of pushing myself – to this day – to continue to learn on nights and weekends, for no reason other than wanting to learn. I refuse to stop expanding my perspective, and do my best to approach new problems with as much humility and curiosity as I can muster.

Every few days for the last year or so, I have been thinking back to a reading assignment from my junior year that, at the time, I thought was a borderline throwaway filler assignment for the class. The reading is an essay from 1947 by the french existentialist philosopher and libertarian marxist, Jean-Paul Sartre (as some of the more erudite may have now already worked out given the blog’s title), “Why Write?”. I re-read it this week. It is not filler. I remember this essay better than some of the classwork I considered more important at the time.

Why Write?

“Why Write?” starts off by describing the ways in which writing – trying to communicate your thoughts, opinions, or feelings to others – is an act of projection. The writer will only ever draw from a place of their “own subjectivity” – writing is taking your person and putting it on display. You’re choosing what words to use, how to use them, pulling from knowledge you’ve accumulated (based on how you’ve chosen to spend your time). Spending any amount of your finite existence in order to convey a thought is, itself, announcing to the world that you believe it to be a thought worth sharing.

Meanwhile, the act of reading is not simply turning letters into words. Reading is engaging with the work, and understanding the work in a process that looks more like what Sartre terms “re-invention” or “discovery” – “the literary object, though realized through language, is never given in language”. It is not enough to read the words in a book end-to-end; you must, as a reader, actively engage with the work to understand what is being communicated by those words. Reading is to take the words on the page, and “exceed” the mere words through what he calls “directed creation”. The reader is “re-inventing”/“discovering” the writer’s thoughts by following their “landmarks in the void”.

And this all makes pretty good sense to me – I know if someone is being sarcastic because I know the writer; I have read their words and have read into their words, allowing myself to be directed by the writer into “discovering” the thought they have left me in their work. I understand that their words are humorous, not irate. Knowing who the author of a work is can completely change the point of a sentence. The fact I’m writing about Sartre at all, or that this very writing has been constrained for presentation in this blog’s CSS is only happening because of who I am, what things I’ve experienced in life, and what has made me, me. Sartre argues that this dyadic coupling between writer and writing means that I, as a writer, can never truly read my own writing. I will never be capable of reading my own work and getting something out of it – the work is already an extension of my own person. I can discover no thought in my own works.

Of course, Sartre, as an existentialist, is honor bound to go one step further here – the reader, by participating in reading a work, is asserting their own freedom. Every time a writer writes “[…] the writer appeals to the reader’s freedom to collaborate in the production of [their] work”. The creative act may only be complete if both writer and reader have recognized one another and made a choice to do so. No one is compelled to complete the creative act. The things you read matter. Reading something fundamentally alters you as a person – you can not simply un-read a thought. Everything you read changes your universe. I have a hunch Sartre would find things like the (original early 2010s era) “tl;dr” reply to obviously terrible writing absolutely hilarious as a reader’s expression of freedom (not to be confused with modern 2020s era usage as shorthand for “summary section”). Using your freedom to choose to complete the writer’s creative act (or not) is inherently asserting your humanity.

I’m a bit fuzzy on the specifics of this quote, but I think it was sj who told me at one year’s Mystery Hunt that “A puzzle is a contract between puzzle author and puzzle solver, the author promises that the puzzle is solvable if you’re clever enough”. The puzzle author and puzzle solver are engaging in a collaborative production of the work that is only possible by recognizing one another. Similarly, Sartre – “whatever connections [the reader] may establish among the different parts of the book among the chapters or the words [the reader] has a guarantee, namely, that they have been expressly willed”.

Wall Drawing #123

It follows, Sartre argues, that the act of writing, as a means to convey a thought to a reader, may only be completed through the act of reading. Reading can only be done by others; writing, therefore, only exists to be read – it can serve no other purpose. Writing and reading are two halves of the same creative, collaborative act, only satisfied when both writer and reader acknowledge one another. Combined, writing and reading are the act of recognizing one another’s humanity, thoughts, experiences, consciousness – the act of co-creation of thought is the critical aspect of writing and reading – reconstructing the author’s perspective, thought, intent, point. The co-creation is the point of both reading and writing.

Writing without anyone to read the work leaves the writer’s bid for co-creation unsatisfied and humanity unrecognized. No thought has been conveyed to any reader, no one has understood the reason behind the “landmarks in the void” you’ve carefully placed, leaving you to either “[…] put down [your] pen or despair”. Writing is an appeal to the reader’s freedom, and the nature of that freedom is the writer can not control it – never being understood is always a possibility any time anyone sets out to write.

Nearly 12 years ago, I attempted to read the text on the git manpage generator for the first time – I remember the exact feeling of my brain going into “git manpage parsing mode” where every word was dragging git plumbing megaliths through the sand from their far-flung homes. I can still feel the surface of my desk as I instinctually started to trace out logical connections between git internals referenced as I read along. It took me a good 20 seconds to realize what I was reading made no sense. This website broke Sartre’s writer-reader agreement – I was attempting to read this website, but there was nothing there. You can “mechanically” “read” the git-man-page-generator, but you can never read it – it is not possible to read it. It was funny – unsettling. Each grasp at a real-looking image in front of me misses, my hand coming back empty. I couldn’t get enough of it. I must have tried to read a dozen generations in a row. I had never had something quite that broken pass that far into my consciousness before. Although I kept trying, it never did feel quite the same as that first time; I think fundamentally, I couldn’t forget that it was random.

While never having anyone read your writing drives them to “put down your pen or despair”, Sartre never had to contend with the opposite problem – being asked to read that which was not written. Reading that which was not written does not merely leave someone unrecognized when a reader makes a choice; instead, it is an inherent violation of the contract between reader and writer. Not only is no humanity being recognized through attempting to read words which were not written, but the reader, not the writer, is the one who bears the burden of unexpected apophenia. The reader, while engaging in co-creation, must now contort themselves to uphold their end of the Sartrean agreement, scrutinizing text to ascribe consciousness, thought and intent only to come back up with pareidolia-fueled echos of one’s own self and disfigured half-thoughts of others. The reality is, the modern reader must now “mechanically” “read” most written work they come across, scrutinizing text for any signs of thought before truly attempting to read the work. Failing to do this correctly changes our person – each time it happens, a small part of us is irrevocably altered. Choosing to engage in this ballet because you wish to do so is one thing – this is your right and freedom as a reader – but passing words which were not written as your own in an attempt to wrestle a reader’s freedom of co-creation from them is another entirely.

If you didn’t write it, I don’t want to read it (dw;dr). Send me your prompt instead.

Petter Reinholdtsen: Long term storage of Mattermost messages with Noark 5 XML

Fri, 18 Sep 2026 07:00:00 +0000

It is said that those who cannot remember the past are condemned to repeat it, a quote often attributed to the American philosopher George Santayana. And to remember the past, records must be maintained and kept accessible to learn from. With this in mind, it is no wonder that archivists worldwide consider it crucial to ensure the archival records are both complete and accurate, with a constant frustration caused by the knowledge that the archives are neither due to challenges in tracking down and collecting what should be archived.

The last few days, I decided to simplify the collection of Messages from the Mattermost chat service, used by a few of the organisations I am involved in, to try to improve the situation slightly. To achieve this, I had written a dedicated extraction tool. Partly to see how hard it would be, and partly to ensure that if one of the services were shut down or replaced, everything in it would not be lost. Of course it is in the nature of the use of instant messages that most of them are not fit for permanent storage, at least not according to Norwegian law, where there is a threshold "worthy of the archive" (arkivverdig) that should be met, and messages like "should we go to lunch now" are below the bar and should be filtered out. The tool can not help with this filtering, and that will have to be done using other means after collection.

The tools I had my bullshit generator write, under strict supervision and many iterations, will extract every message visible to the user whose credentials are used to log into Mattermost, and write it out in Noark 5 extraction XML format and visualize the result. I created the visualiser mostly to quickly be able to debug the extracted XML, but also to make life easier for anyone interested in testing out the tool set.

The extractor mattermost-noark5extract create a hierarchy with arkiv/arkivdel for the Mattermost server, and then individual mappe for each channel and direct message chat, a registrering for each message thread, dokumentbeskrivelse for every message in the tread, and one or more dokumentobjekt for each message and their attachments/images. So far it is only tested on one Mattermost installation, where around 23,000 messages is extracted in 61 seconds and produce 295M with approximately 600 attachments and around 675,000 lines of XML in arkivstruktur.xml. You pass it the URL of the service, a username and password, a directory path where to store the collection and an optional channel name substring to limit the collection to only a subset of the messages available.

The mattermost-noark5extract-browser viewer can load this collection and visualize it similarly to Mattermost's web interface, with the list of channels and direct messages dialogues on the left, messages chronologically in the centre and a selected thread displayed on the right.

I know Mattermost provide several login options. I've only had the one used on my test server implemented so far, and know the extract tool will have to be extended a bit for it to handle servers using one of these options.

If you would like to examine the new toolkit, mattermost-noark5extract is available from gitlab. I wanted to put it on codeberg, but as the recent rule change forbid code mostly written by a bullshit generator there, it was not really an option. Note that some years ago I wrote a similar tool to extract material from the request tracker system. The source for request-tracker-noark5extract is also available from codeberg. I would love to hear from you if you test the tools.

As usual, if you use Bitcoin and wish to support my activities, please send donations to 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

Louis-Philippe Véronneau: Fake Cash: The World Trade Game

Fri, 18 Sep 2026 04:00:00 +0000

This is a new series¹ I'm starting on the tools I have been crafting and buying to play pedagogical games in my Economics classes.

These games, aside from being just plain fun for the students, often aim to teach them a lesson via interactive play. Unsurprisingly, it is much easier for them to grok a particular concept this way. Moreover, many students told me these activities were the best part of the classes I teach.

The World Trade Game

I found out about The World Trade Game in The Handbook of Pluralist Economics Education², which also contains many other fun pedagogical games. It was first developed by Action Aid, but has since been refined by John Sloman and then by Irene van Staveren, who wrote about her use of the game in the aforementioned book.

The goal of this blog entry is not to describe the game and teach you how to play it. If that interests you, either buy the book I mentioned or read about Sloman's version here.

No, our focus point here is the tools to play this game: fake cash! Fake cash can be used in many economics pedagogical games and in my opinion, is a worthwhile "investment" of your time and energy. You could indeed play with regular printed sheets of paper listing a value (I sure did!), but using Play Money (a more appropriate term, since we're not trying to defraud anyone) will up your game and create a more immersive atmosphere in your classes.

At first, I tried to buy play money. Surely, some commercial offering aiming to create realistic props for movies and TV productions existed? At least in Canada, it turns out the answer was no. The only thing I could find were shady websites and weird expensive listings on AliExpress. Not being tenured yet, I did not try to convince my employer to take a 50-50 chance on supporting criminal endeavours.

As such, the next best thing I found was printable play money designed by the Bank of Canada Museum. Their designs were quite nice and met my needs, but their PDF layout made it overly complicated to print large quantities of bills. As such, I played around with GIMP a little and came out with these files. A commercial printer shouldn't have issues printing them on glossy cardstock paper and cutting them up for you:

Once printed and cut, you'll unfortunately have to fold each bill by hand. To secure both halves, I ended up using a strip of transparent tape on each long edge.

Here is the result, with a real Canadian 20$ bill as a comparison:

Don't hold your breath though, as I do not currently have a release schedule. ↩
Reardon, J. (2009). The Handbook of Pluralist Economic Education. New York : Routledge. ↩

Kentaro Hayashi: Building Mozc with dh-bazel, buildsystem support for debhelper

Thu, 17 Sep 2026 12:53:31 +0000

Introduction

After bazel-bootstrap 7.7.1 was landed into Debian unstable, I'm working on packaging newer Mozc (Most famous Japanese input method editor) with Bazel.

Here is the blog entry initial efforts to build Mozc with Bazel at that time.

kenhys.hatenablog.jp

Why dh-bazel?

After that, newer Mozc packages are uploaded into experimental and moved to testing phase on experimental now.

mozc - Debian Package Tracker

When started packaging efforts for newer Mozc with Bazel, I'm a newbie to do it. Now I've got a knowledge to do it a bit, I want to know best practice on packaging X on Debian with Bazel furturmore.

Usually there are dh-X for buildsystem X on Debian, but it's not true for Bazel as far as I know. This is why I had started to write dh-bazel.

I've wrote initial dh-bazel prototype and post a mail to debian-bazel ML.

lists.debian.org

dh-bazel supports the following way:

%:
        dh $@ --buildsystem=bazel

override_dh_auto_build:
        dh_auto_build -- //:hello

If you want to build source under src, you could write d/rule like this:

%:
        dh $@

override_dh_auto_build:
        dh_auto_build --buildsystem=bazel --sourcedirectory=src -- //:hello

Conclusion

dh-bazel is in very early stage prototype, but I have succeeded to build newer Mozc with some modifications to Mozc debian/rules on experimental with dh-bazel locally!

dh-bazel is a thin wrapper for Bazel, so it does not reduce packaging glitches dramatically, but it helps some sort of packaging tasks IMHO.

There are some achievement with dh-bazel

It helps to do similar building way like other debhelper buildsystem
It sets comprehensive Bazel startup options
It sets comprehensive Bazel command options
If you want to set extra flags, just specify it as additional user options (--override_module=, and so on)

Note that it only simplify dh_auto_build stage, so you must manually install artifacts with .install or something correctly.

I hope that it will help package maintainer using Bazel in the future. (dh-bazel is not uploaded into debian/unstable yet, so stay tuned!)

Paul Tagliamonte: DESFire EV3

Tue, 15 Sep 2026 13:25:00 +0000

I’ve long been interested in hardware key material storage devices. I’ve been a fan of yubikeys (I still remember when my fancy new NEO-N showed up), PIV (and its associated smattering of additional fields), SaaS HSMs, the kernel keyring, some tooling I’ve fairly satisfied with the design of at prior companies, and of course, our dear friend, the TPM. All that is not even to mention the scores of exotic hardware security modules one generally comes across from time to time when you’re keeping a sharp eye out that you wind up playing with.

The concept of storing private key material on a disk, or even having it in RAM has always skeeved me out, so I have a natural inclination to hardware modules, and how shifting keying material around can change your risks and threat model(s) in interesting ways.

I don’t remember when I first came across the MIFARE DESFire EV3, but a few weeks ago I did a deep-dive into the state of the art of authentication schemes using ID cards. My complete overview of what tradeoffs exist is pretty extensive (and likely not interesting to the vast majority of the world), but the tl;dr wound up being one of “use PIV” or “use MIFARE DESFire EV3”. I wound up picking DESFire for a recent project, and figured it’s worth talking a bit about what I learned, share some thoughts, and some code. That code is published on crates.io/desox, and docs, as is our custom, may be found at docs.rs/desox

DESFire supports DES (I’m sure most readers saw that one coming), 3DES (I didn’t bother playing with 3DES at all) or AES-128 (AFAICT always use this?) keying material. It’s worth noting that the DESFire only supports symmetric keys and is not designed for public key cryptography, and operates exclusively using shared symmetric key material. The DESFire EV series use those keys and related authentication schemes to interact with “files” stored on the on-chip EEPROM (2k, 4k, 8k, and 16k versions exist), or “applications” (groups of files and authentication keys).

Talking to a DESFire EV3

Interactions with the card are done over NFC (ISO/IEC 14443 Type A), and commands to/from the card may be in the usual ISO/IEC 7816-4 APDU format, or “unencapsulated” bytes sent to/from the card are sent using a fixed instruction set and return code structure – saving a few bytes per message. I’ve opted to use their undocumented and proprietary format – I found it easier to work with and with a maximum message of 60 bytes, the savings matter a lot.

While powered via NFC, the card maintains a small amount of state about the connection between the reader and the card in its RAM, including if the session is authenticated or unauthenticated. I’ll dig into how authentication happens later, but it’s worth knowing that sessions can become authenticated using one of the symmetric keys shared by the card and the reader. The vast majority of the DESFire commands I know about tend to work while either authenticated or unauthenticated, with a few exceptions (GetUid, ChangeKey, and ChangeKeySettings for example).

In general, I found working with this card particularly pleasant. There is a fair amount of backwards-compatible behavior and multiple methods of communication that confuse things a bit, but overall, it was better than average to integrate with. Kudos to the NXP team. If the docs on this chip were public, things would be orders of magnitude easier – it’s not entirely clear to my why they’re keeping so much of the interface documentation under NDA, but it’s the largest knock against the chip, by far.

Authentication

I found a lot of really great resources outlining how the handshake and protocol works for a DESFire EV3, especially from Ridrix, some public datasheets ThrRealRevK and posts from AndroidCrypto.

The gist here is that, because the DESFire only does symmetric key operations, the key exchange (a type of SKA – Symmetric Key Agreement) uses symmetric keys to establish a unique session key which is used to sign or encrypt data exchanged between the reader and the card. I’m not going to get too in-depth here, since there’s a ton of other resources out there to dig into – but I will do a quick high-level description to keep this post mostly self-contained.

The authentication protocol serves two main functions – to verify that both parties know the same shared secret, as well as to act as a SKA to construct a new session shared secret key. Here’s a quick overview of how a shared session key is derived between the reader and the card using our symmetric keys (AES-128 in the case below).

the reader requests to start authentication with the card (something like AA 00 to start an AES Authentication handshake with keyslot 0x00).
The card will then reply with AF (a status code that indicates more data is to follow), followed by 16 bytes (in the case of AES-128) of encrypted (using CBC) data.
The hosts then decrypts this block with the symmetric key from keyslot 0, returning the card’s session nonce.
The host generates 16 bytes (usually random) for its session nonce.
The host sends an instruction of AF (indicating a continuation of the previous command), followed by 32 bytes of encrypted data. When decrypted, the first 16 bytes are our nonce generated in step #4, followed by the 16 bytes provided by the card, decrypted in step #3, except where every byte is shifted to the left by one place (the 0th byte is copied to the end).
The card will reply with 00 indicating a successful operation, followed by 16 bytes, which when decrypted, is our session nonce from step #4, shifted to the left by one byte in the same way that we did in step #5 with the card’s nonce.
At this point, both the reader and card have confirmed the other party has the same symmetric secret key. The session is now “authenticated” and a “session key” is derived using the two nonce blocks. Two hashing keys (K1 and K2) are derived from this key, which is used to maintain an ongoing CMAC hash of the messages coming and going to/from the card.

From here on out, the session is “authenticated”, and responses from the card which were previously “plain” will now contain a 8-byte CMAC signature, which can be used to ensure that the replies in question come from the active session.

In my implementation of the handshake I opted to encode the handshake state into rust types, just so I wouldn’t make any mistakes. The Handshake type contains the session internals (session nonce values, keying state, to include IV, etc). This means the authentication flow (from within my code) uses the Handshake struct to generate the commands to send to the card in order:

/// Create a new `Handshake`, and return the
/// start auth command (something like `AA 00`)
fn Handshake::<Initial>::begin(
 output: &mut [u8],
 key: [u8; 16],
 key_id: u8,
) -> (Self, &[u8]);

After we get a reply back from the card (the encrypted version of the card’s session nonce, sometimes called Rnd_B in code I’ve seen), we transition states from Initial into HalfOpen.

/// Given the card's encrypted response, generate
/// our session nonce and generate a reply
/// (something that starts with `AF` followed by
/// 32 bytes of encrypted data).
fn Handshake::<Initial>::rnd_b(
 self,
 output: &mut [u8],
 input: &[u8]
) -> (Handshake::<HalfOpen>, &[u8]);

Now that we’re “HalfOpen”, we’re waiting to hear back from the card to ensure that it, too, can byte-shift our provided nonce. Once we have the card’s reply, we can check it using our complete helper, transitioning from HalfOpen to Successful.

/// Check to ensure that the card replied with
/// our nonce byte-shifted by one place, indicating
/// that they know the symmetric secret in
/// this key slot.
fn Handshake::<HalfOpen>::complete(
 self,
 input: &[u8]
) -> Handshake::<Successful>;

Once the Handshake is successful, the only thing left to do is consume the Handshake struct and turn it into the shared session key by running it through the key derivation function.

/// Consume the `Handshake` struct and return the
/// new shared session secret key.
fn Handshake::<Successful>::into_key(self) -> [u8; 16];

From here on out we can use this session key for the remainder of our interactions with the card – signing messages from (and sometimes to!) the card, or encrypted messages to and from the card. This key is used in CBC block mode, where the session IV is updated with the last block of the encrypted data.

Unit Testing

A nice proprietary of the SKA scheme we’re using as part of DESFire is that the derived session key is actually deterministic if you control your nonce RNG (ok, actually, pretty true for most key agreements, but anyway), which means it is possible to capture traffic over the NFC interface, and “replay” the NFC I/O with cooked RNGs and ensure byte-identical messages and keys are generated. Within desox-rs this is called replay (I’m creative), and I’ve got a few replay sessions checked into VCS, which exercise a signficant amount fo the API surface. All were derived from an actual session with a real DESFire card, and can be updated with a live card and a --cfg flag.

Each replay file is a set of lines (request-response transactions), each containing two space-delimited hex encoded NFC messages. For instance, here’s an authentication handshake in replay format:

1a00 afc7bbd82ff8fefae8
afc6dab54df2278d2952d560821be7e4c3 007d9abe94a9b14748

The code that generated that exchange came from the test stored adjacent to that file – a handshake with the default DES key (all zeros), and an RndA value hardcoded to 32c28fdafd3960de.

let mut card = card
 .authenticate_with_rnd_a(
 0x00,
 Key::Des([0; 8]),
 Key::Des(hex_literal::hex!("32 c2 8f da fd 39 60 de")),
 )
 .await
 .unwrap();

Since the card’s RndB is similarly unchanging (I’m replaying this file every time), this will always derive the same session key, which means messages (including encrypted ones or CMAC signed responses) will be identical, as well. If you’re playing with the DESFire yourself, feel free to grab my replay files if you need a “known good” baseline.

By default this will run using the MockBackend, replaying each file – expecting a byte-identical request, and responding with the harcoded customary reply. If the code (or test!) needs to change, updating the tests is done by swapping the MockBackend out for a real one. Since I had to do this a bunch during development, running cargo test with RUSTFLAGS="--cfg desox_replay_rw" will, on run, overwrite the replay file(s) for the executed test(s), ensuring all line-protocol changes are explicitly caught and reviewed.

Observations

Most commands, even ones which require authentication, are transmitted without CMAC signature(s) or encryption. CMAC signatures from the reader to the card are not really used (except for writes to a file which specifies communication must be CMAC signed), ditto for encryption (although that one is used for key change operations, in addition to file writes on files that specify encrypted communication must be used). The vast majority of commands take a “plain” request from the reader, and return a CMAC signed response.

By my eye, this means that a malicious reader, or something otherwise capable of holding the card online after communication with an authentic reader is complete are able to execute privilaged commands (since one can simply ignore the CMAC signatures on responses), so long as the command doesn’t require the reader to provide CMAC signatures (or encryption), or allow the card to power down.

Fun with DESFire

I’ve played around a bit with ways to use the DESFire cards in interesting configurations, given what they’re capable of. Here’s some half-baked thoughts I had while mucking around with the cards – these are all poorly thought out sketches of some things we can do given the specific tradeoffs I see with the DESFire card. It’s also worth noting that I don’t have any of the actual documentation, and am not a cryptographic grown-up, so take these sketches with a massive grain of salt.

The first thing that came to mind when implementing this is how the authentication scheme can shift the boundary of what is and is not trusted (assuming good secure keying, and provided the key slots and card/application permissions are configured correctly). Rather than push the key material out to the machine connected to the NFC reader (“reader machine”), I instead tried turning the NFC reader and computer into something psuedo-untrusted by “merely” having it pass messages from the card to a trusted remote system (“remote machine”). This means that the “reader machine” is exchanging NFC data with the card, but that data is being decrypted, encrypted and processed by the trusted “remote machine” – the reader is unable to derive the session key.

For each of these, I wind up needing to authenticate – so there’s still a few latent risks, but these can mostly be mitigated by asking for a readbacks of any changed file(s), setting key permissions carefully, and requesting the card’s UID via the encrypted channel – all of which would require the symmetric secrets (which undermine the whole security model if comprimised).

This general construction is also subject to a hostile takeover of the untrusted “reader machine”, since most commands (including destructive ones!) are sent in “PLAIN” mode – the reader machine can wait until authentication is complete and then inject commands into the card and “simply” ignore the CMAC signatures on responses, severing ties with the remote machine. As such, we also need to take steps to ensure that the key being used is not one that allows any access beyond what is allowed. Here were some ideas I sketched out off the back of this theory.

The “second-factor”

Given some established (and authenticated) connection, part of the initial authentication flow may use the DESFire card to prove physical control over it as part of a handshake. This can serve as a second factor during some authentication flow, requiring physical card presence at a reader to fully initialize a connection. This does have one glaring downside, however – it’s phishable. To use this “for real”, we’d need to take some steps to prevent obvious MITM flows (XOR the NFC messages with the URI as seen by the client?), but maybe there’s something interesting there.

This also has a second interesting attribute – when used as part of a physical system authentication flow, this becomes a logical place to inject access control, being able to determine if some person is permitted to operate some device at that particular time (Is “Joe” current on his Laser Cutter certifications?) I think of the ideas I landed on, while conceptually interesting (using an employee id card as a 2FA token, it’s very fast), this one is the least likely to turn into something real.

This construction, when paired with an encrypted DESFire file, allows the “remote machine” to read/write an ’encrypted cookie’ to the card – storing small amount of encrypted data that the “remote machine” can read/write, but not the “reader machine”, since this uses an encrypted and authenticated channel from the “remote machine” directly to the DESFire card, without any intermediate hosts needing to be fully trusted. I keep calling this the “encrypted cookie” in my head because it feels conceptually similar to how Ruby on Rails and Laravel handles cookies.

We’d need to take a few extra steps here (for instance, ensure that you read the cookie back over the encrypted channel after writing to prevent a malicious reader from dropping writes) to secure the system, but it feels like the structure of this is definitely decent.

The “takeover”

This time, let’s say the computer attached to the NFC reader (“reader machine”) is semi-trusted. For this scheme, our trusted “remote machine” and the “reader machine” pass messages over the network to handle authentication to the card (as above), where the handshake data is being decrypted, encrypted and processed by the trusted “remote machine” as usual. However, once the authentication handshake is complete and a session key has been derived, the “remote system” return the session key to the “reader machine”, giving it a one-time-use key and authenticated session to the card.

We need to be careful about global/application permissions and key access control to files – but in this construction, we can allow the “reader machine” to take over privileged actions using a scope-limited DESFire key without handing over the card’s true keying material (preventing cloning of the card). This can be helpful to ensure messages to/from the card are truely from the card (verifying CMAC signatures), enables the “reader machine” to directly read/write to/from encrypted file(s), but allows the symmetric key material to remain in as few places as possible – which is critical given compromising that secret will undermine the security of the entire system.

Planet Debian

Matthew Garrett: Epic's EAC2 v2 seems fairly easily bypassable

Steinar H. Gunderson: Decompilation patterns, part 12: __builtin_memcpy

Steinar H. Gunderson: Decompilation patterns, part 11: Irregular switch

Dirk Eddelbuettel: qlcal 0.1.4 on CRAN: Fresh Upstream Updates

Changes in version 0.1.4 (2026-10-13)

Reproducible Builds: Reproducible Builds in September 2026

Reproducible Builds Summit 2026 held in Gothenburg, Sweden

Dettrace expanding architecture support for PGO & Lisp dumps

“They don’t care about this”

SOURCE_DATE_EPOCH specification updates

Reproducible Builds at SeaGL 2026

New Code of Conduct (CoC) for the Reproducible Builds project

Supporter Spotlight: Jochen Sprickerhof

Mailing list news

Tool and documentation development

Patches

Russ Allbery: Review: Ties That Bond in Gretna Green

Freexian Collaborators: Debian Contributions: New experimental backend for autopkgtest using pconr, DebConf site visit and more! (by Anupa Ann Joseph)

Debian Contributions: 2026-09

DebConf site visit, by Stefano Rivera

autopkgtest-virt-pconr, by Helmut Grohne

Miscellaneous contributions

Dirk Eddelbuettel: RQuantLib 0.4.29 on CRAN: New QuantLib, Plus Small Fixes

Changes in RQuantLib version 0.4.29 (2026-10-13)

Matthew Garrett: Linux Lockdown and Hibernation (again)

Steinar H. Gunderson: Decompilation patterns, part 10: return var_v0

Maytham Alsudany: Menus without JavaScript

Steinar H. Gunderson: Decompilation patterns part 9, sign extension

Maytham Alsudany: There's more to CSS for underlining

Modern

Workarounds

border-bottom

::after

::after in a container

::after in a container with text stroke

Steinar H. Gunderson: Decompiler patterns, part 8: Un-repetition of conditions

Russ Allbery: Review: Daggerbound

Tim Retout: Reading my solar inverter over RS485

Cables

The risky bit

Debugging over Wi-Fi

Reflections

Dirk Eddelbuettel: RcppSimdJson 0.1.16 on CRAN: Much Faster Again!

Changes in version 0.1.16 (2026-10-09)

Colin Watson: Free software activity in September 2026

OpenSSH

groff

parted

Python packaging

Rust packaging

Russell Coker: Don’t Anthromorphise LLMs

Russell Coker: en-html.org is a Scam Site

Louis-Philippe Véronneau: Removing myself as a Lintian uploader in the next few weeks

Lintian

Reproducible Builds (diffoscope): diffoscope 333 released

Antoine Beaupré: PSA: Europe changes time forward soon, North America next, for the last time?

What's happening?

If your location does not have DST

If you do observe DST

When do times change, how, and and where?

Europe

USA / Canada

Other places with DST

Places without DST

Changes since last time

Thorsten Alteholz: My Debian Activities in September 2026

Debian LTS/ELTS

Debian Printing

Debian Lomiri

Debian Astro

Debian IoT

Debian Mobcom

misc

Dirk Eddelbuettel: myman 0.10.0 on CRAN: Three new waves of posts!

Changes in version 0.10.0 (2026-10-08)

Kentaro Hayashi: Testing Japanese IMEs on virtual desktops with virt-japanese-desktop

What it gives you

The layered-image trick

A platform for experimenting with bleeding-edge IMEs

`SOURCE_DATE_EPOCH` specification updates