anchor.diff:          default = false;
           description = "
             Enable the Varnish Server.
  +        ";
  +      };
  +
  +      http_address = mkOption {
  +        default = "*:6081";
  +        description = "
  +          HTTP listen address and port.
           ";
         };
   
  
positive.code:         chown -R varnish:varnish ${cfg.stateDir}
        '';
        path = [ pkgs.gcc ];
        serviceConfig.ExecStart = "${pkgs.varnish}/sbin/varnishd -f ${pkgs.writeText "default.vcl" cfg.config} -n ${cfg.stateDir} -u varnish";
        serviceConfig.Type = "forking";
      };
  
  
negative.code: { config, pkgs, ...}:
  let
    cfg = config.services.varnish;
  
  in
  with pkgs.lib;
  {
  