Vincent Bernat
@vincent.bernat.ch
Network engineer at AS12322. Debian and free software developer. Like to work on projects with C, Python, or Go. He/him. https://vincent.bernat.ch
Hacking the Go compiler to efficiently map IPv4 to IPv6: vincent.bernat.ch/en/blog/2026.... This post digs in how to modify the Go compiler to reduce netip.AddrFrom16()+netip.As16() to almost nothing, first through the noding process, then with rewrite rules for the SSA form.
Hacking the Go compiler to efficiently map IPv4 to IPv6
Go maintainers declined netip.Addr.Map() saying the compiler should optimize netip.AddrFrom16(ip.As16()) instead. How difficult is it to implement?
vincent.bernat.ch
Self-hosted HTTP tunnels with SSH and nginx: vincent.bernat.ch/en/blog/2026.... That's like ngrok or Cloudflare Quick Tunnels, but self-hosted and you only need SSH.
Self-hosted HTTP tunnels with SSH and nginx
No extra software to install: OpenSSH remote forwarding and nginx's secure_link module give you a shareable HTTPS URL with an expiring token.
vincent.bernat.ch
Bot-free self-hosted analytics with GoatCounter on NixOS: vincent.bernat.ch/en/blog/2026.... With an alternative JavaScript client, a fallback to CSS, an overdoing local proxy, and a lot of NixOS, including Litestream to backup an SQLite database!
Bot-free self-hosted analytics with GoatCounter on NixOS
AI scrapers inflated my visitor count tenfold. I now count a visit only after a user interaction, buffer hits on each web server, and back up the...
vincent.bernat.ch
Quality of life in Thunderbird with this patch to avoid drag&drop folders by accident: github.com/vincentberna.... Thanks to Nix, it's no issue to apply such a patch.
homemanager-configuration/patches/thunderbird-folder-drag.patch at main · vincentbernat/homemanager-configuration
home-manager configuration for use with Debian Sid - vincentbernat/homemanager-configuration
github.com
Sidenotes with CSS anchor positioning: vincent.bernat.ch/en/blog/2026.... A short post about positioning notes in the margin (and not at the end of the document) and a digression on how to spend far more time than needed on this issue.
Sidenotes with CSS anchor positioning
Sidenotes positioned in the margin with CSS anchor positioning, without JavaScript. On narrow viewports and older browsers, they fall back below...
vincent.bernat.ch
I tried uploading my latest video on Youtube. It seems that I have to be "verified" to be able to add a link to the text version or to add a second language track. I also immediately got a claim about the audio soundtrack, while its recording is CC-PDM-1.0. So, I've just deleted the video.
It's difficult to build very high performance tools in Go. For example, BART would benefit for an helper over net/netip: github.com/golang/go/is.... Unfortunately, the maintainers consistently reject these APIs but Go don't really offer any safe workaround. You can't extend, you can't fork.
proposal: net/netip: add Prefix.ContainsIPv4Unchecked and Prefix.ContainsIPv6Unchecked for hot-path lookups · Issue #81236 · golang/go
Proposal Details Author Karl Gaissmaier Abstract I propose adding two exported, fully inlinable methods to netip.Prefix: ContainsIPv4Unchecked(Addr) bool ContainsIPv6Unchecked(Addr) bool. These met...
github.com
Minor update for Akvorado, your beloved flow collector. Among them, a few small fixes, the ability to zoom out, or the support for DB-IP. github.com/akvorado/akv...
Release v2026.8.1 · akvorado/akvorado
💥 console: console.homepage-graph-filter now uses the console filter language instead of SQL 🩹 console: fix completion for DstNetName and the other network attributes 🩹 console: accept again an emp...
github.com
An interactive introduction to the spanning tree protocol: vincent.bernat.ch/en/blog/2026.... While the spanning tree protocol is quite old, it is still sometimes useful. This article explores it with interactive demonstrations running a real daemon (MSTPD) compiled to WebAssembly with Emscripten.
An interactive introduction to the spanning tree protocol
Root election, port roles, proposals and agreements, topology changes: explore RSTP through simulations powered by MSTPD compiled to WebAssembly.
vincent.bernat.ch
nixpkgs multiverse, now faster and leaner! fzakaria.com/2026/08/14/n... With the previous iteration released last week, if you pin a lot of packages, you pull many versions of nixpkgs and evaluate them. Not anymore! You can fetch directly from the cache! Look at the other articles from the blog too
nixpkgs-multiverse: fast mode
“The fastest evaluation is the one that never happens.” – Sun Tzu, The Art of Evaluation
fzakaria.com
In Debian, CDBS has been deprecated and removed. It didn't get much love, but for a very long time, it made packaging easier by making implicit good decisions, a bit like the "recent" dh command sequencer (2008).
New release of Akvorado, a IPFIX/sFlow collector with a builtin web interface for visualization. We are switching to CalVer for versioning. The GeoIP/networks database migrates from the orchestrator to the outlet. It is now possible to export enriched flows to Kafka. github.com/akvorado/akv...
Release v2026.8.0 · akvorado/akvorado
Akvorado does not use the networks ClickHouse dictionary anymore. It is not removed on upgrade: it still holds a copy of the GeoIP databases in ClickHouse memory. Drop it on each cluster member onc...
github.com
came across a neat post to understand IP lookup using trie and other optimizations on top of it. thanks @vincent.bernat.ch vincent.bernat.ch/en/blog/2017...
IPv4 route lookup on Linux
Linux uses an LPC-trie for looking up routes. It provides good performance with low memory use even with millions of routes.
vincent.bernat.ch
I was about to write an article comparing semicolons in English with BGP confederations in networking: both of them are taught in class but shouldn't be used outside. Unfortunately, it seems the discourse around semicolons is more nuanced.
for fellow freaks who want to render sheet music by writing plain text inside of markdown inside of Astro, well, I made something for you! astro-lilypond converts text to SVG and works in markdown or with a <LilyPond> component. zero client-side JS. 🎶 docs and install: lilypond.ky.fyi
Astro LilyPond
Render LilyPond music notation to images with Astro.
lilypond.ky.fyi
I've asked IEEE the authorization to reproduce one diagram from IEEE 802.1Q (through standards.ieee.org/ipr/copyrigh...). Do they answer "fast"?
IEEE Standards Permission For Use Form
Submit requests for permission for use of IEEE copyrighted material published by IEEE Standards Association.
standards.ieee.org
I had this article about contributing to RRDtool in draft for more than 10 years! I just published it "as is:" vincent.bernat.ch/en/blog/2013... The goal was to encourage people around me to contribute to open source. Unfortunately, the patch took a bit of time to be accepted.
Contributing to open source: a new feature for RRDtool
Note (2026-07) This article was not completed and stayed as a draft for more than 10 years. As I think it is still useful today, even incomplete,...
vincent.bernat.ch
Just published Akvorado 2.4.1, your friendly IPFIX/NetFlow/sFlow collector: github.com/akvorado/akv....
Release v2.4.1 · akvorado/akvorado
🩹 outlet: fix decoding of destination MAC address for sFlow 🩹 console: avoid clipped labels in Sankey graphs 🩹 console: fix empty widgets when toggling dark mode 🌱 outlet: improve BMP RIB performan...
github.com
In Firefox, one tab for Outlook Web and one tab for Teams already eats 2.1GB of RAM. The next one is Zulip with only 150MB (which I think is OK).
ah yes...I should also post about OUR book. the 2nd edition of "Observability Engineering" is now available for download.. and you can download it for free on the honeycomb site. this was supposed to be an update, and ended up being a total rewrite (& then some). 😅 www.honeycomb.io/blog/the-sec...
The Second Edition of Observability Engineering Is Here
IT’S HERE it’s here it’s here it’s here!!!! The second edition of Observability Engineering is available for download, and since Honeycomb is the sponsor, you can now download it from our website (th...
honeycomb.io
Doug Winter@doug.winter.cx · 4mo agoBoth Cat and Charity are very much worth reading.
I've made a Kubernetes that runs in the browser, and today we're open sourcing it. The hope here is to make super interactive and visual web content about Kubernetes much easier to write, and we have a whole bunch planned this year. Repo: github.com/ngrok/webern... Demo: webernetes-demo.ngrok.app
(Some) writers appreciate LLM writing assistance but readers hate it. Survey says… writethatblog.substack.com/p/dev-reacti... If readers suspect AI, they not only stop reading, but also downvote/avoid the author.
Building a Soviet Nail Factory: how KPIs killed efficiency. A story that I often tell. It is now old enough to not upset my former colleagues. vincent.bernat.ch/en/blog/2026...
Building a Soviet Nail Factory: how KPIs killed efficiency
How an obsession with KPIs at Orange led people to game them, slowing service delivery to a crawl. A cautionary tale about Goodhart's law.
vincent.bernat.ch
TIL: `export -f` in bash can export a function to a subshell
yes!! thank you for noticing!! :D i have been going to TOWN lately generating sticker art and slogans and learning graphic design fundamentals. maybe i will write about that today, hm. this is one of my favorite themes.. it feels very.. scandinavian? i will mail you some if you give me an address!
Blogging with an LLM assistant: vincent.bernat.ch/en/blog/2026... (grammar, copyediting, translation). This specific post is *not* modified by an LLM.
Blogging with an LLM assistant
As a non-native English writer, I rely on LLMs for grammar, copyediting, and translation, despite hating AI slop.
vincent.bernat.ch
i wrote a post about the growing divide between AI skeptics and AI enthusiasts. wins and costs are both real, but too often fall on different groups of people. when you're only experiencing half the story, it's too easy to write each other off. charitydotwtf.substack.com/p/ai-enthusi...
AI enthusiasts are in a race against time, AI skeptics are in a race against entropy
Both sides are grappling with a real existential threat, and both sides feel like they are screaming into the void. Here's how to close the gap and get everyone pulling in the same direction.
charitydotwtf.substack.com
