Ask HN: What rabbit hole(s) did you dive into recently?

It's interesting to discover that a lot of 'facts' about public transport people take for granted just aren't true. The names and liveries by which vehicles go often don't actually correspond with their actual operators and owners. The company that's named on your ticket might not actually get any money from your purchase - or they might make money from passengers who don't pay at all, due to a myriad of subsidy schemes run by different levels of government.

Waves of privatization and re-nationalization with political motivations at every turn have produced a system which is amazingly efficient in some ways, and appallingly wasteful in others. Workforce strikes are obvious to the general public, but what's not obvious is who the negotiating parties even are, with various trade unions (and unions of unions) competing against various management groups (and groups of groups).

Some things are pleasantly surprising. Without any fanfare, digital systems for vehicle tracking have been introduced with remarkable efficiency. Then, for me, there's the astonishment of discovering that not only is every timetable published in a consistent, nation-wide data format, but one that has been utilised in production for twenty years!

It all makes me realise how limited the public discourse about public transport and 'green' mobility policies are in my region. It is simply impossible to grasp the true consequences of any given proposal in the meagre columns that they're given in the newspapers and the two-minute reports in which they feature on the television. Diving into this rabbit hole has led me to respect the complexity of the field much more than I did before, and fills me with both hope and despair on topics which I had hitherto scarcely lent a thought.

I don't currently use it in any serious projects aside from tinkering about with it, but it has been a lot of fun to learn and study.

Between the Nix package manager, the associated language, etc., there has been a lot to learn about, and it's been good fun. I have nixOS on my spare Thinkpad for toying with, and I have Nix on my main Debian systems, if I want to pull something from nixpkgs.

However I can salve my ego spending a day flipping through neovim colour themes.

Intermediate step - I feel pretty confident with the gory details of the kernel code now. can possibly build a custom kernel, boot qemu with both a simple C+assembly bare metal kernel, or the self compiled kernel. I feels like the clouds have cleared and I can see the sun. - Incidentally the kernel source code is pretty well documented, but one thing which is missing is a much smaller list of files which are most important. true pareto here. 20% files carry the weight. You also need to know the subsystem you want to touch. Chances are that subsystem is much lesser number of files.

Finally - Got to reading about kernel packet handling. at the L2/L3/L7 level. from nic hardware to userspace. Turns out that eBPF [hello old friend!] has a networking avataar called XDP which is pretty recent [And now I feel the itch to apply this to some of our networks. Particularly, baremetal servers on equinix metal + aws ec2 + azure can be peered with either VPP/Bird to make a p2p connection which is a factor more performant than the vpc interconnect/gateways which are provided off the shelf.

I might extend the holiday by a few days. and I would love to talk to people who have hands on experience with any of this. Its hard to contain my excitement tbh.