+ * @brief Build a notify payload and add it to the message.
+ *
+ * This is a helper method to create notify messages or add
+ * notify payload to messages. The flush parameter specifies if existing
+ * payloads should get removed before appending the notify.
+ *
+ * @param this message_t object
+ * @param flush TRUE to remove existing payloads
+ * @param type type of the notify
+ * @param data a chunk of data to add to the notify, gets cloned
+ */
+ void (*add_notify) (message_t *this, bool flush, notify_type_t type,
+ chunk_t data);
+
+ /**