nixpkgs/nixos/tests/networking/router.nix

{ networkd }: { config, pkgs, ... }:
  let
    inherit (pkgs) lib;
    qemu-common = import ../../lib/qemu-common.nix { inherit lib pkgs; };
    vlanIfs = lib.range 1 (lib.length config.virtualisation.vlans);
  in {
    environment.systemPackages = [ pkgs.iptables ]; # to debug firewall rules
    virtualisation.vlans = [ 1 2 3 ];
    boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = true;
    networking = {
      useDHCP = false;
      useNetworkd = networkd;
      firewall.checkReversePath = true;
      firewall.allowedUDPPorts = [ 547 ];
      interfaces = lib.mkOverride 0 (lib.listToAttrs (lib.forEach vlanIfs (n:
        lib.nameValuePair "eth${toString n}" {
          ipv4.addresses = [ { address = "192.168.${toString n}.1"; prefixLength = 24; } ];
          ipv6.addresses = [ { address = "fd00:1234:5678:${toString n}::1"; prefixLength = 64; } ];
        })));
    };
    services.kea = {
      dhcp4 = {
        enable = true;
        settings = {
          interfaces-config = {
            interfaces = map (n: "eth${toString n}") vlanIfs;
            dhcp-socket-type = "raw";
            service-sockets-require-all = true;
            service-sockets-max-retries = 5;
            service-sockets-retry-wait-time = 2500;
          };
          subnet4 = map (n: {
            id = n;
            subnet = "192.168.${toString n}.0/24";
            pools = [{ pool = "192.168.${toString n}.3 - 192.168.${toString n}.254"; }];
            option-data = [
              { data = "192.168.${toString n}.1"; name = "routers"; }
              { data = "192.168.${toString n}.1"; name = "domain-name-servers"; }
            ];

            reservations = [{
              hw-address = qemu-common.qemuNicMac n 1;
              hostname = "client${toString n}";
              ip-address = "192.168.${toString n}.2";
            }];
          }) vlanIfs;
        };
      };
      dhcp6 = {
        enable = true;
        settings = {
          interfaces-config = {
            interfaces = map (n: "eth${toString n}") vlanIfs;
            service-sockets-require-all = true;
            service-sockets-max-retries = 5;
            service-sockets-retry-wait-time = 2500;
          };

          subnet6 = map (n: {
            id = n;
            subnet = "fd00:1234:5678:${toString n}::/64";
            interface = "eth${toString n}";
            pools = [{ pool = "fd00:1234:5678:${toString n}::2-fd00:1234:5678:${toString n}::2"; }];
          }) vlanIfs;
        };
      };
    };
    services.radvd = {
      enable = true;
      config = lib.flip lib.concatMapStrings vlanIfs (n: ''
        interface eth${toString n} {
          AdvSendAdvert on;
          AdvManagedFlag on;
          AdvOtherConfigFlag on;

          prefix fd00:1234:5678:${toString n}::/64 {
            AdvAutonomous off;
          };
        };
      '');
    };
  }