modules/bridge/default.nix

@@ -28,6 +28,12 @@ in
         type = types.str;
         description = "bridge interface name to create";
       };
+
+      macAddressFromInterface = mkOption {
+        type = types.nullOr liminix.lib.types.service;
+        default = null;
+        description = "reuse mac address from an existing interface service";
+      };
     };
     members = config.system.callService ./members.nix {
       primary = mkOption {

modules/bridge/primary.nix

@@ -3,15 +3,20 @@
 , ifwait
 , lib
 }:
-{ ifname } :
+{ ifname, macAddressFromInterface ? null } :
 let
   inherit (liminix.services) bundle oneshot;
-  inherit (lib) mkOption types;
+  inherit (lib) mkOption types optional;
 in oneshot rec {
   name = "${ifname}.link";
   up = ''
-    ip link add name ${ifname} type bridge
+    ${if macAddressFromInterface == null then
+      "ip link add name ${ifname} type bridge"
+      else
+      "ip link add name ${ifname} address $(output ${macAddressFromInterface} ether) type bridge"}
     ${liminix.networking.ifup name ifname}
   '';
   down = "ip link set down dev ${ifname}";
+
+  dependencies = optional (macAddressFromInterface != null) macAddressFromInterface;
 }

pkgs/liminix-tools/networking/default.nix

@@ -9,6 +9,7 @@
     ip link set up dev ${ifname}
     (in_outputs ${name}
      echo ${ifname} > ifname
+     cat /sys/class/net/${ifname}/address > ether
     )
   '';
 }