nixos-servers/nixos/modules/networking/default.nix

{ lib, config, machine, ... }:
let cfg = config.lab.networking;
in {
  imports = [ ./dmz_services ];

  options.lab.networking = {
    dmz = {
      allowConnectivity = lib.mkOption {
        default = false;
        type = lib.types.bool;
        description = ''
          Whether to allow networking on the DMZ bridge interface.
        '';
      };

      bridgeName = lib.mkOption {
        default = "bridgedmz";
        type = lib.types.str;
        description = ''
          The name of the DMZ bridge.
        '';
      };
    };

    mainNicNamePattern = lib.mkOption {
      default = "en*";
      type = lib.types.str;
      description = ''
        Pattern to match the name of this machine's main NIC.
      '';
    };
  };

  config = {
    networking = {
      domain = if machine.type == "physical" then "hyp" else "dmz";
      nftables.enable = true;
      useDHCP = false;

      firewall = {
        enable = true;
        checkReversePath = false;
      };
    };

    systemd.network = lib.mkIf (machine.type == "physical") {
      enable = true;

      netdevs = {
        "20-vlandmz" = {
          vlanConfig.Id = 30;

          netdevConfig = {
            Kind = "vlan";
            Name = "vlandmz";
          };
        };

        "20-bridgedmz" = {
          netdevConfig = {
            Kind = "bridge";
            Name = cfg.dmz.bridgeName;
          };
        };
      };

      networks = {
        "30-main-nic" = {
          matchConfig.Name = cfg.mainNicNamePattern;
          vlan = [ "vlandmz" ];

          networkConfig = {
            DHCP = "yes";
          };
        };

        "40-vlandmz" = {
          matchConfig.Name = "vlandmz";
          linkConfig.RequiredForOnline = "enslaved";

          networkConfig = {
            IPv6AcceptRA = false;
            LinkLocalAddressing = "no";
            Bridge = cfg.dmz.bridgeName;
          };
        };

        "40-bridgedmz" = {
          matchConfig.Name = cfg.dmz.bridgeName;
          linkConfig.RequiredForOnline = "carrier";

          networkConfig = {
            IPv6AcceptRA = cfg.dmz.allowConnectivity;
            LinkLocalAddressing = if cfg.dmz.allowConnectivity then "ipv6" else "no";
            DHCP = "yes";
          };
        };

        "40-vms" = {
          matchConfig.Name = "vm-*";
          networkConfig.Bridge = cfg.dmz.bridgeName;
        };
      };
    };
  };
}