anchor.diff:    ### implementation
   
     config = mkIf (cfg.server.enable || cfg.clients != {}) {
  -    boot.kernel.sysctl = optionalAttrs cfg.server.systemPings {
  +    boot.kernel.sysctl = optionalAttrs cfg.server.respondToSystemPings {
         "net.ipv4.icmp_echo_ignore_all" = 1;
       };
   
  
positive.code:           example = "198.51.100.0";
          };
  
          systemPings = mkOption {
            type = types.bool;
            default = false;
            description = "Respond to ordinary pings";
          };
  
          extraConfig = mkOption {
  
negative.code:         description = "hans, ip over icmp server daemon";
          after = [ "network.target" ];
          wantedBy = [ "multi-user.target" ];
          script = "${pkgs.hans}/bin/hans -f -u ${hansUser} ${cfg.server.extraConfig} -s ${cfg.server.ip} ${optionalString cfg.server.respondToSystemPings "-r"} ${optionalString (cfg.passwordFile != "") "-p $(cat \"${cfg.passwordFile}\")"}";
        };
      };
  
  