anchor.diff:  
     ###### interface
   
  -  options = {
  +  options.services.radvd = {
   
  -    services.radvd.enable = mkOption {
  +    enable = mkOption {
         type = types.bool;
         default = false;
         description =
  
positive.code:         wantedBy = [ "multi-user.target" ];
          after = [ "network.target" ];
          serviceConfig =
            { ExecStart = "@${pkgs.radvd}/bin/radvd radvd -n -u radvd -C ${confFile}";
              Restart = "always";
            };
        };
  
negative.code:         '';
      };
  
      package = mkOption {
        type = types.package;
        default = pkgs.radvd;
        defaultText = literalExpression "pkgs.radvd";
        description = ''
          The RADVD package to use for the RADVD service.
        '';
      };
  
      config = mkOption {
        type = types.lines;
        example =
          ''
  