nixos/echoip: improve systemd hardening

        );

        # Hardening

        AmbientCapabilities = "";

        CapabilityBoundingSet = [ "" ];

        DeviceAllow = [ "" ];

        DevicePolicy = "closed";

        LockPersonality = true;

        MemoryDenyWriteExecute = true;

        NoNewPrivileges = true;

        PrivateDevices = true;

        PrivateTmp = true;

        PrivateUsers = true;

        ProtectKernelTunables = true;

        ProtectProc = "invisible";

        ProtectSystem = "strict";

        RestrictAddressFamilies = [

          "AF_INET"

          "AF_INET6"

          "AF_UNIX"

        ];

        RemoveIPC = true;

        RestrictAddressFamilies = [ "AF_INET AF_INET6 AF_UNIX" ];

        RestrictNamespaces = true;

        RestrictRealtime = true;

        RestrictSUIDSGID = true;

        SystemCallArchitectures = "native";

        SystemCallFilter = [

          "@system-service"

          "~@privileged"

          "~@resources"

          "setrlimit"

        ];

        UMask = "0077";

      };

    };