ubusd: add support for watching objects to get notified when they go away

libubus.c

@@ -709,7 +709,7 @@ static bool ubus_push_object_type(const struct ubus_object_type *type)
 	return true;
 }
 
-static int __ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj)
+int ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj)
 {
 	struct ubus_request req;
 	int ret;
@@ -740,14 +740,6 @@ static int __ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj)
 	return 0;
 }
 
-int ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj)
-{
-	if (!obj->name || !obj->type)
-		return UBUS_STATUS_INVALID_ARGUMENT;
-
-	return __ubus_add_object(ctx, obj);
-}
-
 static void ubus_remove_object_cb(struct ubus_request *req, int type, struct blob_attr *msg)
 {
 	struct ubus_object *obj = req->priv;
@@ -819,7 +811,7 @@ int ubus_register_event_handler(struct ubus_context *ctx,
 		if (!!obj->name ^ !!obj->type)
 			return UBUS_STATUS_INVALID_ARGUMENT;
 
-		ret = __ubus_add_object(ctx, obj);
+		ret = ubus_add_object(ctx, obj);
 		if (ret)
 			return ret;
 	}
@@ -835,6 +827,81 @@ int ubus_register_event_handler(struct ubus_context *ctx,
 			  NULL, NULL, 0);
 }
 
+enum {
+	WATCH_ID,
+	WATCH_NOTIFY,
+	__WATCH_MAX
+};
+
+static const struct blobmsg_policy watch_policy[] = {
+	[WATCH_ID] = { .name = "id", .type = BLOBMSG_TYPE_INT32 },
+	[WATCH_NOTIFY] = { .name = "notify", .type = BLOBMSG_TYPE_STRING },
+};
+
+
+static int ubus_watch_cb(struct ubus_context *ctx, struct ubus_object *obj,
+			 struct ubus_request_data *req,
+			 const char *method, struct blob_attr *msg)
+{
+	struct ubus_watch_object *w;
+	struct blob_attr *tb[__WATCH_MAX];
+
+	blobmsg_parse(watch_policy, ARRAY_SIZE(watch_policy), tb, blob_data(msg), blob_len(msg));
+
+	if (!tb[WATCH_ID] || !tb[WATCH_NOTIFY])
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	if (req->peer)
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	w = container_of(obj, struct ubus_watch_object, obj);
+	w->cb(ctx, w, blobmsg_get_u32(tb[WATCH_ID]));
+	return 0;
+}
+
+static const struct ubus_method watch_method = {
+	.name = NULL,
+	.handler = ubus_watch_cb,
+};
+
+int ubus_register_watch_object(struct ubus_context *ctx, struct ubus_watch_object *w_obj)
+{
+	struct ubus_object *obj = &w_obj->obj;
+
+	obj->methods = &watch_method;
+	obj->n_methods = 1;
+
+	return ubus_add_object(ctx, obj);
+}
+
+static int
+__ubus_watch_request(struct ubus_context *ctx, struct ubus_object *obj, uint32_t id, const char *method, int type)
+{
+	struct ubus_request req;
+
+	blob_buf_init(&b, 0);
+	blob_put_int32(&b, UBUS_ATTR_OBJID, obj->id);
+	blob_put_int32(&b, UBUS_ATTR_TARGET, id);
+	if (method)
+		blob_put_string(&b, UBUS_ATTR_METHOD, method);
+
+	if (ubus_start_request(ctx, &req, b.head, type, 0) < 0)
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	return ubus_complete_request(ctx, &req, 0);
+
+}
+
+int ubus_watch_object_add(struct ubus_context *ctx, struct ubus_watch_object *obj, uint32_t id)
+{
+	return __ubus_watch_request(ctx, &obj->obj, id, "event", UBUS_MSG_ADD_WATCH);
+}
+
+int ubus_watch_object_remove(struct ubus_context *ctx, struct ubus_watch_object *obj, uint32_t id)
+{
+	return __ubus_watch_request(ctx, &obj->obj, id, NULL, UBUS_MSG_REMOVE_WATCH);
+}
+
 int ubus_send_event(struct ubus_context *ctx, const char *id,
 		    struct blob_attr *data)
 {

libubus.h

@@ -26,6 +26,7 @@ struct ubus_request;
 struct ubus_request_data;
 struct ubus_object_data;
 struct ubus_event_handler;
+struct ubus_watch_object;
 
 typedef void (*ubus_lookup_handler_t)(struct ubus_context *ctx,
 				      struct ubus_object_data *obj,
@@ -35,6 +36,8 @@ typedef int (*ubus_handler_t)(struct ubus_context *ctx, struct ubus_object *obj,
 			      const char *method, struct blob_attr *msg);
 typedef void (*ubus_event_handler_t)(struct ubus_context *ctx, struct ubus_event_handler *ev,
 				     const char *type, struct blob_attr *msg);
+typedef void (*ubus_watch_handler_t)(struct ubus_context *ctx, struct ubus_watch_object *w,
+				     uint32_t id);
 typedef void (*ubus_data_handler_t)(struct ubus_request *req,
 				    int type, struct blob_attr *msg);
 typedef void (*ubus_complete_handler_t)(struct ubus_request *req, int ret);
@@ -84,6 +87,12 @@ struct ubus_object {
 	int n_methods;
 };
 
+struct ubus_watch_object {
+	struct ubus_object obj;
+
+	ubus_watch_handler_t cb;
+};
+
 struct ubus_event_handler {
 	struct ubus_object obj;
 
@@ -185,6 +194,13 @@ int ubus_add_object(struct ubus_context *ctx, struct ubus_object *obj);
 /* remove the object from the ubus connection */
 int ubus_remove_object(struct ubus_context *ctx, struct ubus_object *obj);
 
+/* add an object for watching other object state changes */
+int ubus_register_watch_object(struct ubus_context *ctx, struct ubus_watch_object *obj);
+
+int ubus_watch_object_add(struct ubus_context *ctx, struct ubus_watch_object *obj, uint32_t id);
+
+int ubus_watch_object_remove(struct ubus_context *ctx, struct ubus_watch_object *obj, uint32_t id);
+
 /* ----------- rpc ----------- */
 
 /* invoke a method on a specific object */

ubusd_obj.c

@@ -112,6 +112,8 @@ struct ubus_object *ubusd_create_object_internal(struct ubus_object_type *type,
 	obj->type = type;
 	INIT_LIST_HEAD(&obj->list);
 	INIT_LIST_HEAD(&obj->events);
+	INIT_LIST_HEAD(&obj->watchers);
+	INIT_LIST_HEAD(&obj->watched);
 	if (type)
 		type->refcount++;
 
@@ -162,8 +164,39 @@ free:
 	return NULL;
 }
 
+void ubus_watch_new(struct ubus_object *obj, struct ubus_object *target, const char *method)
+{
+	struct ubus_watch *w;
+
+	w = calloc(1, sizeof(*w) + strlen(method) + 1);
+	if (!w)
+		return;
+
+	w->watcher = obj;
+	w->watched = target;
+	list_add(&w->watcher_list, &target->watchers);
+	list_add(&w->watched_list, &obj->watched);
+	strcpy(w->method, method);
+}
+
+void ubus_watch_free(struct ubus_watch *w)
+{
+	list_del(&w->watcher_list);
+	list_del(&w->watched_list);
+	free(w);
+}
+
 void ubusd_free_object(struct ubus_object *obj)
 {
+	struct ubus_watch *w, *tmp;
+
+	list_for_each_entry_safe(w, tmp, &obj->watched, watched_list) {
+		ubus_watch_free(w);
+	}
+	list_for_each_entry_safe(w, tmp, &obj->watchers, watcher_list) {
+		ubus_proto_notify_watch(w);
+	}
+
 	ubusd_event_cleanup_object(obj);
 	if (obj->path.key) {
 		ubusd_send_obj_event(obj, false);

ubusd_obj.h

@@ -35,12 +35,20 @@ struct ubus_method {
 	struct blob_attr data[];
 };
 
+struct ubus_watch {
+	struct list_head watcher_list, watched_list;
+	struct ubus_object *watcher, *watched;
+	char method[];
+};
+
 struct ubus_object {
 	struct ubus_id id;
 	struct list_head list;
 
 	struct list_head events;
 
+	struct list_head watchers, watched;
+
 	struct ubus_object_type *type;
 	struct avl_node path;
 
@@ -48,6 +56,7 @@ struct ubus_object {
 	int (*recv_msg)(struct ubus_client *client, const char *method, struct blob_attr *msg);
 
 	int event_seen;
+	unsigned int invoke_seq;
 };
 
 struct ubus_object *ubusd_create_object(struct ubus_client *cl, struct blob_attr **attr);
@@ -67,4 +76,8 @@ static inline struct ubus_object *ubusd_find_object(uint32_t objid)
 	return obj;
 }
 
+void ubus_watch_new(struct ubus_object *obj, struct ubus_object *target, const char *method);
+void ubus_watch_free(struct ubus_watch *w);
+void ubus_proto_notify_watch(struct ubus_watch *w);
+
 #endif

ubusd_proto.c

@@ -285,6 +285,61 @@ error:
 	return -1;
 }
 
+static int ubusd_handle_add_watch(struct ubus_client *cl, struct ubus_msg_buf *ub, struct blob_attr **attr)
+{
+	struct ubus_object *obj, *target;
+
+	if (!attr[UBUS_ATTR_OBJID] || !attr[UBUS_ATTR_TARGET] ||
+	    !attr[UBUS_ATTR_METHOD]) {
+		return UBUS_STATUS_INVALID_ARGUMENT;
+	}
+
+	obj = ubusd_find_object(blob_get_u32(attr[UBUS_ATTR_OBJID]));
+	if (!obj)
+		return UBUS_STATUS_NOT_FOUND;
+
+	if (cl != obj->client)
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	target = ubusd_find_object(blob_get_u32(attr[UBUS_ATTR_TARGET]));
+	if (!target)
+		return UBUS_STATUS_NOT_FOUND;
+
+	if (cl == target->client)
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	ubus_watch_new(obj, target, blob_data(attr[UBUS_ATTR_METHOD]));
+	return 0;
+}
+
+static int ubusd_handle_remove_watch(struct ubus_client *cl, struct ubus_msg_buf *ub, struct blob_attr **attr)
+{
+	struct ubus_object *obj;
+	struct ubus_watch *w;
+	uint32_t id;
+
+	if (!attr[UBUS_ATTR_OBJID] || !attr[UBUS_ATTR_TARGET])
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	obj = ubusd_find_object(blob_get_u32(attr[UBUS_ATTR_OBJID]));
+	if (!obj)
+		return UBUS_STATUS_NOT_FOUND;
+
+	if (cl != obj->client)
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	id = blob_get_u32(attr[UBUS_ATTR_TARGET]);
+	list_for_each_entry(w, &obj->watched, watched_list) {
+		if (w->watched->id.id != id)
+			continue;
+
+		ubus_watch_free(w);
+		return 0;
+	}
+
+	return UBUS_STATUS_NOT_FOUND;
+}
+
 static const ubus_cmd_cb handlers[__UBUS_MSG_LAST] = {
 	[UBUS_MSG_PING] = ubusd_send_pong,
 	[UBUS_MSG_ADD_OBJECT] = ubusd_handle_add_object,
@@ -293,6 +348,8 @@ static const ubus_cmd_cb handlers[__UBUS_MSG_LAST] = {
 	[UBUS_MSG_INVOKE] = ubusd_handle_invoke,
 	[UBUS_MSG_STATUS] = ubusd_handle_response,
 	[UBUS_MSG_DATA] = ubusd_handle_response,
+	[UBUS_MSG_ADD_WATCH] = ubusd_handle_add_watch,
+	[UBUS_MSG_REMOVE_WATCH] = ubusd_handle_remove_watch,
 };
 
 void ubusd_proto_receive_message(struct ubus_client *cl, struct ubus_msg_buf *ub)
@@ -359,6 +416,28 @@ void ubusd_proto_free_client(struct ubus_client *cl)
 	ubus_free_id(&clients, &cl->id);
 }
 
+void ubus_proto_notify_watch(struct ubus_watch *w)
+{
+	struct ubus_msg_buf *ub;
+	void *data;
+
+	blob_buf_init(&b, 0);
+	blob_put_int32(&b, UBUS_ATTR_OBJID, w->watcher->id.id);
+	blob_put_string(&b, UBUS_ATTR_METHOD, w->method);
+
+	data = blob_nest_start(&b, UBUS_ATTR_DATA);
+	blobmsg_add_string(&b, "notify", "remove");
+	blobmsg_add_u32(&b, "id", w->watched->id.id);
+	blobmsg_add_u32(&b, "peer", w->watched->client->id.id);
+	blob_nest_end(&b, data);
+
+	ub = ubus_msg_from_blob(false);
+	ubus_msg_init(ub, UBUS_MSG_INVOKE, ++w->watcher->invoke_seq, 0);
+	ubus_msg_send(w->watcher->client, ub, true);
+
+	ubus_watch_free(w);
+}
+
 static void __init ubusd_proto_init(void)
 {
 	ubus_init_id_tree(&clients);

ubusmsg.h

@@ -54,6 +54,10 @@ enum ubus_msg_type {
 	UBUS_MSG_ADD_OBJECT,
 	UBUS_MSG_REMOVE_OBJECT,
 
+	/* watch an object, notify on remove */
+	UBUS_MSG_ADD_WATCH,
+	UBUS_MSG_REMOVE_WATCH,
+
 	/* must be last */
 	__UBUS_MSG_LAST,
 };
@@ -71,6 +75,7 @@ enum ubus_msg_attr {
 	UBUS_ATTR_SIGNATURE,
 
 	UBUS_ATTR_DATA,
+	UBUS_ATTR_TARGET,
 
 	/* must be last */
 	UBUS_ATTR_MAX,