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

{ lib, config, machine, ... }:
let cfg = config.lab.networking;
in {
  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.
        '';
      };
    };

    staticNetworking = lib.mkOption {
      default = false;
      type = lib.types.bool;
      description = ''
        Whether this machine has static networking configuration applied.
        Routing is prepopulated, but IP addresses have to be set.
      '';
    };

    staticIPv4 = lib.mkOption {
      type = lib.types.str;
      description = ''
        Static IPv4 address for the machine.
      '';
    };

    staticIPv6 = lib.mkOption {
      type = lib.types.str;
      description = ''
        Static IPv6 address for the machine.
      '';
    };
  };

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

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

    systemd.network = {
      enable = true;

      netdevs = lib.mkIf machine.isHypervisor {
        "20-vlandmz" = {
          vlanConfig.Id = 30;

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

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

      networks = lib.attrsets.mergeAttrsList [
        (lib.optionalAttrs machine.isHypervisor {
          "30-main-nic" = {
            matchConfig.Name = "en*";
            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;
          };
        })
        (lib.optionalAttrs machine.isVirtual {
          "30-main-nic" = {
            matchConfig.Name = "en*";

            networkConfig = {
              IPv6AcceptRA = ! cfg.staticNetworking;
              DHCP = lib.mkIf (! cfg.staticNetworking) "yes";

              Address = lib.mkIf cfg.staticNetworking [
                "${cfg.staticIPv4}/${cfg.dmz.ipv4.prefixLength}"
                "${cfg.staticIPv6}/${cfg.dmz.ipv6.prefixLength}"
              ];

              DNS = lib.mkIf cfg.staticNetworking [
                cfg.dmz.ipv4.router
                cfg.dmz.ipv6.router
              ];
            };

            routes = lib.mkIf cfg.staticNetworking [
              {
                routeConfig = {
                  Gateway = cfg.dmz.ipv4.router;
                  Destination = "0.0.0.0/0";
                };
              }
              {
                routeConfig = {
                  Gateway = cfg.dmz.ipv6.router;
                  Destination = "::/0";
                };
              }
            ];
          };
        })
        (lib.optionalAttrs machine.isRaspberryPi {
          "30-main-nic" = {
            matchConfig.Name = "end*";
            networkConfig = {
              IPv6AcceptRA = true;
              DHCP = "yes";
            };
          };
        })
      ];
    };
  };
}