int sd_bus_track_new(sd_bus *bus, sd_bus_track **track, sd_bus_track_handler_t handler, void *userdata);
sd_bus_track* sd_bus_track_ref(sd_bus_track *track);
sd_bus_track* sd_bus_track_unref(sd_bus_track *track);
+
sd_bus* sd_bus_track_get_bus(sd_bus_track *track);
+void *sd_bus_track_get_userdata(sd_bus_track *track);
+void *sd_bus_track_set_userdata(sd_bus_track *track, void *userdata);
int sd_bus_track_add_sender(sd_bus_track *track, sd_bus_message *m);
int sd_bus_track_remove_sender(sd_bus_track *track, sd_bus_message *m);