refactor(nixos): consolidate VLAN networking

configs/nixos/hosts/pikachu/default.nix

@@ -15,46 +15,10 @@
 
   hardware.cpu.intel.updateMicrocode = true;
 
-  systemd.network = {
+  modules.network.vlans = {
-    enable = true;
+    interface = "enp2s0";
-    netdevs = {
+    ids = [ 20 ];
-      "40-br-vlan20".netdevConfig = {
-        Name = "br-vlan20";
-        Kind = "bridge";
   };
-      "40-vlan20" = {
-        netdevConfig = {
-          Name = "vlan20";
-          Kind = "vlan";
-        };
-        vlanConfig.Id = 20;
-      };
-    };
-
-    networks = {
-      "10-uplink" = {
-        matchConfig = {
-          Name = "enp2s0";
-          MACAddress = "78:55:36:07:af:49";
-        };
-        networkConfig.DHCP = "yes";
-        vlan = [ "vlan20" ];
-        linkConfig.RequiredForOnline = "routable";
-      };
-      "40-vlan20" = {
-        matchConfig.Name = "vlan20";
-        networkConfig.Bridge = "br-vlan20";
-        linkConfig.RequiredForOnline = "no";
-      };
-      "40-br-vlan20" = {
-        matchConfig.Name = "br-vlan20";
-        linkConfig.RequiredForOnline = "no";
-      };
-    };
-  };
-  networking.useDHCP = false;
-
-  modules.network.vlans.ids = [ 20 ];
 
   boot.zfs.forceImportRoot = false;
 

configs/nixos/modules/network/vlans.nix

@@ -4,24 +4,17 @@
   util,
   ...
 }:
-# The host networking foundation: per-VLAN bridges over a tagged trunk.
+# Configures bridges for tagged VLANs on a physical interface that uses DHCP.
 let
   cfg = config.modules.network.vlans; # NOLINT(let_order)
-
-  inherit (util) bridgeName;
-
-  vlanName = id: "${cfg.trunk}.${toString id}";
 in
 {
   options.modules.network.vlans = {
-    enable = lib.mkEnableOption "host VLAN bridges over a tagged trunk";
+    interface = lib.mkOption {
-
-    trunk = lib.mkOption {
       type = lib.types.str;
       example = "enp1s0";
       description = ''
-        Physical interface that carries 802.1Q-tagged traffic for every VLAN.
+        Names the physical interface that carries untagged DHCP traffic and tagged VLANs.
-        Each declared VLAN attaches to its own bridge.
       '';
     };
 
@@ -34,67 +27,37 @@ in
         30
       ];
       description = ''
-        Tagged VLAN ids to materialize.
+        Creates bridges for the specified tagged VLAN IDs.
-        Each id N creates one bridge named `br-vlanN`.
-      '';
-    };
 
-    management = {
+        VLAN ID N creates bridge `br-vlanN`.
-      vlan = lib.mkOption {
-        type = lib.types.nullOr (lib.types.ints.between 1 4094);
-        default = null;
-        description = ''
-          VLAN whose bridge carries the host's own management address.
-          The value must be one of `ids`.
-          Left null, the host takes no address on any bridge.
-        '';
-      };
-
-      address = lib.mkOption {
-        type = lib.types.nullOr lib.types.str;
-        default = null;
-        example = "10.0.10.2/24";
-        description = ''
-          Host static management address in CIDR form.
-          Left null, the host takes its management address by DHCP.
       '';
     };
   };
-  };
 
-  config = lib.mkIf cfg.enable {
+  config = lib.mkIf (cfg.ids != [ ]) {
-    assertions = [
+    networking = {
-      {
+      useDHCP = false;
-        assertion = cfg.management.vlan == null || lib.elem cfg.management.vlan cfg.ids;
+      networkmanager.unmanaged = [
-        message = "modules.network.vlans.management.vlan (${toString cfg.management.vlan}) must name one of modules.network.vlans.ids.";
+        "interface-name:${cfg.interface}"
-      }
-      {
-        assertion = cfg.management.address == null || cfg.management.vlan != null;
-        message = "modules.network.vlans.management.address needs modules.network.vlans.management.vlan to say which bridge carries it.";
-      }
-    ];
-
-    # networkd owns these interfaces so NetworkManager does not contend for them.
-    networking.networkmanager.unmanaged = [
-      "interface-name:${cfg.trunk}"
       ]
-    ++ map (id: "interface-name:${bridgeName id}") cfg.ids
+      ++ map (id: "interface-name:${util.bridgeName id}") cfg.ids
-    ++ map (id: "interface-name:${vlanName id}") cfg.ids;
+      ++ map (id: "interface-name:vlan${toString id}") cfg.ids;
+    };
 
     systemd.network = {
       enable = true;
 
       netdevs = lib.mkMerge (
         map (id: {
-          "40-${bridgeName id}" = {
+          "40-${util.bridgeName id}" = {
             netdevConfig = {
-              Name = bridgeName id;
+              Name = util.bridgeName id;
               Kind = "bridge";
             };
           };
-          "40-${vlanName id}" = {
+          "40-vlan${toString id}" = {
             netdevConfig = {
-              Name = vlanName id;
+              Name = "vlan${toString id}";
               Kind = "vlan";
             };
             vlanConfig.Id = id;
@@ -104,37 +67,25 @@ in
 
       networks = lib.mkMerge (
         [
-          # The trunk carries only tagged frames and takes no address.
           {
-            "30-${cfg.trunk}" = {
+            "10-${cfg.interface}" = {
-              matchConfig.Name = cfg.trunk;
+              matchConfig.Name = cfg.interface;
-              networkConfig.LinkLocalAddressing = "no";
+              networkConfig.DHCP = "yes";
-              linkConfig.RequiredForOnline = "no";
+              vlan = map (id: "vlan${toString id}") cfg.ids;
-              vlan = map vlanName cfg.ids;
+              linkConfig.RequiredForOnline = "routable";
             };
           }
         ]
         ++ map (id: {
-          # Enslaved to its bridge, carrying no address itself.
+          "40-vlan${toString id}" = {
-          "40-${vlanName id}" = {
+            matchConfig.Name = "vlan${toString id}";
-            matchConfig.Name = vlanName id;
+            networkConfig.Bridge = util.bridgeName id;
-            networkConfig.Bridge = bridgeName id;
             linkConfig.RequiredForOnline = "no";
           };
-          # The management bridge carries the host address.
+          "40-${util.bridgeName id}" = {
-          # Other bridges provide L2 segments for guests.
+            matchConfig.Name = util.bridgeName id;
-          "40-${bridgeName id}" = lib.mkMerge [
-            {
-              matchConfig.Name = bridgeName id;
             linkConfig.RequiredForOnline = "no";
-            }
+          };
-            (lib.mkIf (cfg.management.vlan == id) (
-              if cfg.management.address == null then
-                { networkConfig.DHCP = "yes"; }
-              else
-                { address = [ cfg.management.address ]; }
-            ))
-          ];
         }) cfg.ids
       );
     };