anchor.diff:        enable = mkEnableOption "Dante SOCKS proxy";
   
         config = mkOption {
  -        default     = null;
  -        type        = types.nullOr types.str;
  +        type        = types.lines;
           description = ''
  -          Contents of Dante's configuration file
  -          NOTE: user.privileged/user.unprivileged are set by the service
  +          Contents of Dante's configuration file.
  +          NOTE: user.privileged, user.unprivileged and logoutput are set by the service.
           '';
         };
       };
  
positive.code:   confFile = pkgs.writeText "dante-sockd.conf" ''
      user.privileged: root
      user.unprivileged: dante
  
      ${cfg.config}
    '';
  
negative.code: 
    config = mkIf cfg.enable {
      assertions = [
        { assertion   = cfg.config != "";
          message     = "please provide Dante configuration file contents";
        }
      ];
  