ovn: fix missing ovsdb binaries

[positiveEV]

Hi @adamcstephens ,

Last time, I forgot the most important items: the OVSDB binaries.
This time I tested it in a nix-shell --pure so that me PATH was clean.

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/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 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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[adamcstephens]

This feels a bit wrong, since we also have an openvswitch package, but if ovn expects these here we'll go with it. I originally tried to use our openvswitch directly, but failed. :/

[positiveEV]

I have the same feeling, but the ovsdb-server is mandatory to run the OVN northbound and southbound databases, and we might want to run them on a different host than the ovn-controller, which actually requires Open vSwitch (ovs-vswitchd). That's why I believe it should be included in the OVN package.

Another solution would be to create an Open vSwitch package that includes only ovsdb-client, ovsdb-server, and ovsdb-tool, and then add this package as a dependency of the OVN package, similar to how Debian handles openvswitch-common. However, I don't think this approach aligns with the Nix philosophy and may complicate maintenance.

There is also the workaround that I am currently using which is to add pkgs.openvswitch to the systemd.services.<name>.path option of the ovn-nb-ovsdb service.

[adamcstephens]

I suspect we don't want to use the nixpkgs openvswitch package for binaries unless we're also compiling ovn against that same package/version.

This PR is fine for now. :)

Are you hoping to use this work on stable? Or, since you're really doing the development on this, is unstable ok for your needs for now? Wondering if we need to keep backporting these or if we can target 25.05 for a more useful release with ovn.

[positiveEV]

Since we don't want to use the binaries from the openvswitch pkg, which I also think is the logical thing to do, I am going to try to include what is needed to run vswitchd and its ovsdb-server in the ovn pkg.
So there is no need to backport it.