logind: add infrastructure to watch busnames

If we want to track bus-names to allow exclusive resource-access, we need
a way to get notified when a bus-name is gone. We make logind watch for
NameOwnerChanged dbus events and check whether the name is currently
watched. If it is, we remove it from the watch-list (notification for
other objects can be added in follow-up patches).

1 files changed, 17 insertions, 0 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index d052e7478..5decf8114 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -2459,6 +2459,23 @@ DBusHandlerResult bus_message_filter(
                         HASHMAP_FOREACH(session, m->sessions, i)
                                 session_add_to_gc_queue(session);
                 }
+
+        } else if (dbus_message_is_signal(message, DBUS_INTERFACE_DBUS, "NameOwnerChanged")) {
+                const char *name, *old, *new;
+                char *key;
+
+                if (!dbus_message_get_args(message, &error,
+                                           DBUS_TYPE_STRING, &name,
+                                           DBUS_TYPE_STRING, &old,
+                                           DBUS_TYPE_STRING, &new,
+                                           DBUS_TYPE_INVALID)) {
+                        log_error("Failed to parse NameOwnerChanged message: %s", bus_error_message(&error));
+                        goto finish;
+                }
+
+                if (*old && !*new && (key = hashmap_remove(m->busnames, old))) {
+                        free(key);
+                }
         }
 
 finish: