Add macvlan support for declarative containers

[montag451]

Motivation for this change

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[mention-bot]

@montag451, thanks for your PR! By analyzing the history of the files in this pull request, we identified @kampfschlaefer, @edolstra and @wlhlm to be potential reviewers.

[kampfschlaefer]

Any chance you could add a test to prove that this works as intended and doesn't break anytime soon?

[montag451]

I use nixos-container run for a test but it's not reliable as long as #21044 is not solved

[kampfschlaefer]

I like that!

One additional suggestion: is it also possible (and) testable to ping the containers from machine1? Or is that not how macvlans works?

[montag451]

@kampfschlaefer Yes I could ping from the host but I would have to create another macvlan (on the host) on the same network than eth1. So it would complicate the test because I would end up with two interfaces on the same network. Do you know if it's possible to prevent the test framework to automatically assign an IP to eth1? By the way, thank for you review, it's really valuable for newcomer like me!

[montag451]

@kampfschlaefer Finally I found a way to ping containers from host (see 6cedee9e21fe8b00cbfc910c451a1f00a34e09ca)

[kampfschlaefer]

@montag451 I think the contribution guidelines want these commits squashed, maybe the two test commits can be together?

Otherwise 👍

(sadly I am not yet a member and can not merge this for you)

[montag451]

@kampfschlaefer I squashed all the commits into one. Thanks again for your help 👍

[Mic92]

Thanks!