anchor.diff:          pkgs.openresolv
         ]
         ++ optional (cfg.bridges != {}) pkgs.bridge_utils
  +      ++ optional hasVirtuals pkgs.tunctl
         ++ optional cfg.enableIPv6 pkgs.ndisc6;
   
       security.setuidPrograms = [ "ping" "ping6" ];
  
positive.code: let
  
    cfg = config.networking;
  
  in
  
  
negative.code:         preStart =
            ''
              set +e # continue in case of errors
  
              # Create virtual network interfaces
              ${flip concatMapStrings cfg.interfaces (i:
                optionalString i.virtual
                  ''
                    echo "Creating virtual network interface ${i.name}..."
                    ${pkgs.tunctl}/bin/tunctl -t "${i.name}" -u "${i.virtualOwner}"
                  '')
              }
  
              # Set MAC addresses of interfaces, if desired.
              ${flip concatMapStrings cfg.interfaces (i:
  