anchor.diff:        macAddress = mkOption {
           default = null;
           example = "00:11:22:33:44:55";
  -        type = types.nullOr types.string;
  +        type = types.nullOr (types.uniq types.string);
           description = ''
             MAC address of the interface. Leave empty to use the default.
           '';
  
positive.code:       subnetMask = mkOption {
          default = "";
          example = "255.255.255.0";
          type = types.string;
          description = ''
            Subnet mask of the interface, specified as a bitmask.
            This is deprecated; use <option>prefixLength</option>
  
negative.code: 
        name = mkOption {
          example = "eth0";
          type = types.uniq types.string;
          description = "Name of the interface.";
        };
  
        ipAddress = mkOption {
          default = null;
          example = "10.0.0.1";
          type = types.nullOr (types.uniq types.string);
          description = ''
            IP address of the interface.  Leave empty to configure the
            interface using DHCP.
  