+/**
+ * function prototype for the vhost backend to handler specific vhost user
+ * messages prior to the master message handling
+ *
+ * @param vid
+ * vhost device id
+ * @param msg
+ * Message pointer.
+ * @param require_reply
+ * If the handler requires sending a reply, this varaible shall be written 1,
+ * otherwise 0.
+ * @param skip_master
+ * If the handler requires skipping the master message handling, this variable
+ * shall be written 1, otherwise 0.
+ * @return
+ * 0 on success, -1 on failure
+ */
+typedef int (*vhost_msg_pre_handle)(int vid, void *msg,
+ uint32_t *require_reply, uint32_t *skip_master);
+
+/**
+ * function prototype for the vhost backend to handler specific vhost user
+ * messages after the master message handling is done
+ *
+ * @param vid
+ * vhost device id
+ * @param msg
+ * Message pointer.
+ * @param require_reply
+ * If the handler requires sending a reply, this varaible shall be written 1,
+ * otherwise 0.
+ * @return
+ * 0 on success, -1 on failure
+ */
+typedef int (*vhost_msg_post_handle)(int vid, void *msg,
+ uint32_t *require_reply);
+
+/**
+ * pre and post vhost user message handlers
+ */
+struct vhost_user_extern_ops {
+ vhost_msg_pre_handle pre_msg_handle;
+ vhost_msg_post_handle post_msg_handle;
+};
+