nixos/systemd-networkd: add PREF64 related options

[jmbaur]

Description of changes

Tested to work in the legacy nested *Config format as well as the newer flattened format.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[flokli]

Is there a chance we can actually add a test for this?

[jmbaur]

Is there a chance we can actually add a test for this?

Sure thing! A functional test or a test that the config is what we expect?

[flokli]

Is there a chance we can actually add a test for this?

Sure thing! A functional test or a test that the config is what we expect?

I was thinking about a VM test with a "server" configuring such a prefix in their RA announcements, and a client with UsePREF64 set to true, then peeking at networkctl output to see it's there?

I didn't check but in case resolved already makes use of this information for AAAA record synthesis (or dnssec validation), doing a query for something with only a A record, and expecting to get back a synthesized record back could be tested too?

As far as sending any traffic is concerned, you could get some inspiration from our ipv6 prefix delegation test, but I assume we're still missing some CLAT in Linux?

[jmbaur]

@flokli So we do have a clatd test! I added a commit that augments that test to ensure the networkd options work as expected.

[jmbaur]

@ofborg test clatd

[flokli]

LGTM, but I'd like to give @hax404 a chance to also review the test additions.

[mweinelt]

I think it is reasonable to backport this change, as it introduces the declarative interface for functionality present in systemd 255.

[hax404]

Very nice work!

[github-actions]

Backport failed for release-24.05, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin release-24.05
git worktree add -d .worktree/backport-318604-to-release-24.05 origin/release-24.05
cd .worktree/backport-318604-to-release-24.05
git switch --create backport-318604-to-release-24.05
git cherry-pick -x b867cc215f2d01b25f478c6c711b5be9374c3dac d4d5fd718d3ef05b3f47750a6d5462a4e21c321c

[flokli]

@mweinelt please do the backport manually.