+ /* Called whenever a name thus Unit registered for comes or
+ * goes away. */
+ void (*bus_name_owner_change)(Unit *u, const char *name, const char *old_owner, const char *new_owner);
+
+ /* Called whenever a bus PID lookup finishes */
+ void (*bus_query_pid_done)(Unit *u, const char *name, pid_t pid);
+
+ /* Called for each message received on the bus */
+ DBusHandlerResult (*bus_message_handler)(Unit *u, DBusMessage *message);
+