Merge pull request #3200 from wkennington/master.dhcpcd

nixos/dhcpcd: Add an explicit interfaces option

nixos/modules/services/networking/dhcpcd.nix

@@ -6,6 +6,8 @@ let
 
   dhcpcd = if !config.boot.isContainer then pkgs.dhcpcd else pkgs.dhcpcd.override { udev = null; };
 
+  cfg = config.networking.dhcpcd;
+
   # Don't start dhcpcd on explicitly configured interfaces or on
   # interfaces that are part of a bridge, bond or sit device.
   ignoredInterfaces =
@@ -38,7 +40,10 @@ let
       # (Xen) and virbr* and vnet* (libvirt).
       denyinterfaces ${toString ignoredInterfaces} lo peth* vif* tap* tun* virbr* vnet* vboxnet* sit*
 
-      ${config.networking.dhcpcd.extraConfig}
+      # Use the list of allowed interfaces if specified
+      ${optionalString (cfg.allowInterfaces != null) "allowinterfaces ${toString cfg.allowInterfaces}"}
+
+      ${cfg.extraConfig}
     '';
 
   # Hook for emitting ip-up/ip-down events.
@@ -81,6 +86,17 @@ in
       '';
     };
 
+    networking.dhcpcd.allowInterfaces = mkOption {
+      type = types.nullOr (types.listOf types.str);
+      default = null;
+      description = ''
+         Enable the DHCP client for any interface whose name matches
+         any of the shell glob patterns in this list. Any interface not
+         explicitly matched by this pattern will be denied. This pattern only
+         applies when non-null.
+      '';
+    };
+
     networking.dhcpcd.extraConfig = mkOption {
       type = types.lines;
       default = "";