nixos/firewall: handle conntrack helper autodetection being removed in 6.0

[K900]

Description of changes

Upstream change: https://lore.kernel.org/all/20220830153319.71890-1-pablo@netfilter.org/

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.05 Release Notes (or backporting 22.11 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.

[vcunat]

I'd say the assertion is worth backporting to 22.11, too.

[vcunat]

Also #219457

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/cannot-rebuild-due-to-conntrack-helper-error-after-updating-channels-and-attempt-to-upgrade/27523/2

[SuperSandro2000]

How do I migrate away from this setting? Need to have access to the sysctl setting net.netfilter.nf_conntrack_max at boot to increase it. When not auto loading the conntrack helpers, the setting does not exist.

[vcunat]

I don't know this stuff, but I still have /proc/sys/net/netfilter/nf_conntrack_max on default-ish 6.1 kernel.

[SuperSandro2000]

That path was in the past not available on boot when the sysctl settings are applied and I needed to load the conntrack module early on.