Add macvlan support for declarative containers

nixos/modules/virtualisation/containers.nix

@@ -476,6 +476,17 @@ in
               '';
             };
 
+            macvlans = mkOption {
+              type = types.listOf types.str;
+              default = [];
+              example = [ "eth1" "eth2" ];
+              description = ''
+                The list of host interfaces from which macvlans will be
+                created. For each interface specified, a macvlan interface
+                will be created and moved to the container.
+              '';
+            };
+
             extraVeths = mkOption {
               type = with types; attrsOf (submodule { options = networkOptions; });
               default = {};
@@ -654,6 +665,7 @@ in
               ''}
             ''}
             INTERFACES="${toString cfg.interfaces}"
+            MACVLANS="${toString cfg.macvlans}"
             ${optionalString cfg.autoStart ''
               AUTO_START=1
             ''}