bus: Add a handle_vips() hook invoked after handling configuration attributes

Similar to assign_vips() used by a peer assigning virtual IPs to the other peer,
the handle_vips() hook gets invoked on a peers after receiving attributes. On
release of the same attributes the hook gets invoked again.

This is useful to inspect handled attributes, as the ike_updown() hook is
invoked after authentication, when attributes have not been handled yet.

src/libcharon/bus/bus.c

@@ -879,6 +879,33 @@ METHOD(bus_t, assign_vips, void,
 	this->mutex->unlock(this->mutex);
 }
 
+METHOD(bus_t, handle_vips, void,
+	private_bus_t *this, ike_sa_t *ike_sa, bool handle)
+{
+	enumerator_t *enumerator;
+	entry_t *entry;
+	bool keep;
+
+	this->mutex->lock(this->mutex);
+	enumerator = this->listeners->create_enumerator(this->listeners);
+	while (enumerator->enumerate(enumerator, &entry))
+	{
+		if (entry->calling || !entry->listener->handle_vips)
+		{
+			continue;
+		}
+		entry->calling++;
+		keep = entry->listener->handle_vips(entry->listener, ike_sa, handle);
+		entry->calling--;
+		if (!keep)
+		{
+			unregister_listener(this, entry, enumerator);
+		}
+	}
+	enumerator->destroy(enumerator);
+	this->mutex->unlock(this->mutex);
+}
+
 /**
  * Credential manager hook function to forward bus alerts
  */
@@ -955,6 +982,7 @@ bus_t *bus_create()
 			.authorize = _authorize,
 			.narrow = _narrow,
 			.assign_vips = _assign_vips,
+			.handle_vips = _handle_vips,
 			.destroy = _destroy,
 		},
 		.listeners = linked_list_create(),