nixos-router/tests/apply.nix

# A router configured by settings.json, changed and rebuilt on the device:
# install it (its configuration directory travels with the secrets), boot it
# without network, then
#   - rebuilding the unchanged settings gives exactly the installed system,
#   - a changed setting is built offline, activated and confirmed,
#   - an unconfirmed change is rolled back.
{ self, pkgs }:
let
  inherit (pkgs) lib;
  common = import ./common.nix;

  settings = pkgs.writeText "settings.json" (
    builtins.toJSON {
      system = {
        hostName = "router";
        stateVersion = "26.11";
        sshKeys = [
          "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFakeKeyForTestsOnlyXXXXXXXXXXXXXXXXXXXXXXXXXX test"
        ];
      };
      router = {
        wan.interface = "eth1";
        lans.main = {
          interface = "eth2";
          internet = true;
          ipv4.address = "192.168.10.1";
          dhcp.pool = {
            start = "192.168.10.100";
            end = "192.168.10.199";
          };
        };
      };
    }
  );

  # Only so the test driver can talk to the installed system.
  local = pkgs.writeText "local.nix" ''
    { modulesPath, ... }:
    {
      imports = [ (modulesPath + "/testing/test-instrumentation.nix") ];
    }
  '';

  configDir = self.lib.mkConfigDir { inherit pkgs settings local; };

  # What the device evaluates from configDir.
  toplevel =
    (self.lib.mkRouterSystem {
      settings = "${configDir}/settings.json";
      modules = [ "${configDir}/local.nix" ];
    }).config.system.build.toplevel;

  sharedDisk = {
    virtualisation.diskImage = "./target.qcow2";
    virtualisation.diskSize = 8192;
  };
in
pkgs.testers.runNixOSTest {
  name = "router-apply";

  nodes = {
    installer =
      { lib, ... }:
      {
        imports = [
          sharedDisk
          self.nixosModules.installer
          common.tools
        ];
        router.installer.system = toplevel;
        virtualisation.memorySize = 2048;
        virtualisation.fileSystems."/".autoFormat = true;
        virtualisation.emptyDiskImages = [ 1024 ];
        virtualisation.rootDevice = "/dev/vdb";
        nix.settings.substituters = lib.mkForce [ ];
      };

    target = {
      imports = [ sharedDisk ];
      # Evaluating a NixOS system takes memory.
      virtualisation.memorySize = 3072;
      virtualisation.vlans = [
        1
        2
      ];
      virtualisation.useBootLoader = true;
      virtualisation.useEFIBoot = true;
      virtualisation.useDefaultFilesystems = false;
      virtualisation.efi.keepVariables = false;
      virtualisation.fileSystems."/" = {
        device = "/dev/disk/by-label/this-is-not-real-and-will-never-be-used";
        fsType = "ext4";
      };
    };
  };

  testScript = ''
    installer.start()
    installer.wait_for_unit("multi-user.target")
    installer.succeed("mkdir -p /root/secrets && cp -r ${configDir} /root/secrets/config")
    installer.succeed("router-install --yes --secrets /root/secrets /dev/vda >&2")
    installer.shutdown()

    target.state_dir = installer.state_dir
    target.start()
    target.wait_for_unit("multi-user.target")

    def current():
        return target.succeed("readlink -f /run/current-system").strip()

    def pool_end():
        return target.succeed("grep -o '192.168.10.100 - 192.168.10.[0-9]*' /etc/kea/dhcp4-server.conf").split()[-1]

    with subtest("the installed system is the one built from the settings"):
        assert current() == "${toplevel}"
        target.succeed("test -f /var/lib/router/config/settings.json")

    with subtest("rebuilding unchanged settings on the device changes nothing"):
        out = target.succeed("router-apply 2>&1")
        assert "no changes" in out, out

    with subtest("a changed setting is built offline, activated and confirmed"):
        target.succeed("sed -i 's/192.168.10.199/192.168.10.150/' /var/lib/router/config/settings.json")
        target.succeed("router-apply 5min >&2")
        assert current() != "${toplevel}"
        assert pool_end() == "192.168.10.150"
        target.succeed("systemctl is-active router-rollback.timer")
        target.succeed("router-confirm >&2")
        target.fail("systemctl is-active router-rollback.timer")
        confirmed = current()
        assert target.succeed("readlink -f /nix/var/nix/profiles/system").strip() == confirmed

    with subtest("an unconfirmed change is rolled back"):
        target.succeed("sed -i 's/192.168.10.150/192.168.10.120/' /var/lib/router/config/settings.json")
        target.succeed("router-apply 20s >&2")
        assert pool_end() == "192.168.10.120"
        target.wait_until_succeeds(f"test $(readlink -f /run/current-system) = {confirmed}", timeout=120)
        assert pool_end() == "192.168.10.150"
  '';
}