ubusd: add lookup command queuing support

Defers and continues a client's lookup command to avoid unnecessary
buffering under load.

Signed-off-by: Daniel Danzberger <daniel@dd-wrt.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

ubusd.h

@@ -41,6 +41,12 @@ struct ubus_msg_buf_list {
 	struct ubus_msg_buf *msg;
 };
 
+struct ubus_client_cmd {
+	struct list_head list;
+	struct ubus_msg_buf *msg;
+	struct ubus_object *obj;
+};
+
 struct ubus_client {
 	struct ubus_id id;
 	struct uloop_fd sock;
@@ -53,6 +59,7 @@ struct ubus_client {
 
 	struct list_head objects;
 
+	struct list_head cmd_queue;
 	struct list_head tx_queue;
 	unsigned int txq_ofs;
 	unsigned int txq_len;
@@ -86,6 +93,7 @@ void ubusd_proto_receive_message(struct ubus_client *cl, struct ubus_msg_buf *ub
 void ubusd_proto_free_client(struct ubus_client *cl);
 void ubus_proto_send_msg_from_blob(struct ubus_client *cl, struct ubus_msg_buf *ub,
 				   uint8_t type);
+int ubusd_cmd_lookup(struct ubus_client *cl, struct ubus_client_cmd *cmd);
 
 typedef struct ubus_msg_buf *(*event_fill_cb)(void *priv, const char *id);
 void ubusd_event_init(void);

ubusd_main.c

@@ -32,6 +32,28 @@ static void handle_client_disconnect(struct ubus_client *cl)
 	free(cl);
 }
 
+static void ubus_client_cmd_free(struct ubus_client_cmd *cmd)
+{
+	list_del(&cmd->list);
+	ubus_msg_free(cmd->msg);
+	free(cmd);
+}
+
+static void ubus_client_cmd_queue_process(struct ubus_client *cl)
+{
+	struct ubus_client_cmd *cmd, *tmp;
+
+	list_for_each_entry_safe(cmd, tmp, &cl->cmd_queue, list) {
+		int ret = ubusd_cmd_lookup(cl, cmd);
+
+		/* Stop if the last command caused buffering again */
+		if (ret == -2)
+			break;
+
+		ubus_client_cmd_free(cmd);
+	}
+}
+
 static void client_cb(struct uloop_fd *sock, unsigned int events)
 {
 	struct ubus_client *cl = container_of(sock, struct ubus_client, sock);
@@ -82,10 +104,15 @@ static void client_cb(struct uloop_fd *sock, unsigned int events)
 		ubus_msg_list_free(ubl);
 	}
 
-	/* prevent further ULOOP_WRITE events if we don't have data
-	 * to send anymore */
-	if (list_empty(&cl->tx_queue) && (events & ULOOP_WRITE))
-		uloop_fd_add(sock, ULOOP_READ | ULOOP_EDGE_TRIGGER);
+	if (list_empty(&cl->tx_queue) && (events & ULOOP_WRITE)) {
+		/* Process queued commands */
+		ubus_client_cmd_queue_process(cl);
+
+		/* prevent further ULOOP_WRITE events if we don't have data
+		 * to send anymore */
+		if (list_empty(&cl->tx_queue))
+			uloop_fd_add(sock, ULOOP_READ | ULOOP_EDGE_TRIGGER);
+	}
 
 retry:
 	if (!sock->eof && cl->pending_msg_offset < (int) sizeof(cl->hdrbuf)) {

ubusd_proto.c

@@ -186,16 +186,56 @@ static void ubusd_send_obj(struct ubus_client *cl, struct ubus_msg_buf *ub, stru
 		ubus_proto_send_msg_from_blob(cl, ub, UBUS_MSG_DATA);
 }
 
-static int ubusd_handle_lookup(struct ubus_client *cl, struct ubus_msg_buf *ub, struct blob_attr **attr)
+static int ubus_client_cmd_queue_add(struct ubus_client *cl,
+					struct ubus_msg_buf *msg,
+					struct ubus_object *obj)
 {
-	struct ubus_object *obj;
+	struct ubus_client_cmd *cmd = malloc(sizeof(*cmd));
+
+	if (cmd) {
+		cmd->msg = msg;
+		cmd->obj = obj;
+		list_add_tail(&cmd->list, &cl->cmd_queue);
+		return -2;
+	}
+	return UBUS_STATUS_UNKNOWN_ERROR;
+}
+
+static int __ubusd_handle_lookup(struct ubus_client *cl,
+				struct ubus_msg_buf *ub,
+				struct blob_attr **attr,
+				struct ubus_client_cmd *cmd)
+{
+	struct ubus_object *obj = NULL;
 	char *objpath;
 	bool found = false;
 	int len;
 
 	if (!attr[UBUS_ATTR_OBJPATH]) {
-		avl_for_each_element(&path, obj, path)
-			ubusd_send_obj(cl, ub, obj);
+		if (cmd)
+			obj = cmd->obj;
+
+		/* Start from beginning or continue from the last object */
+		if (obj == NULL)
+			obj = avl_first_element(&path, obj, path);
+
+		avl_for_element_range(obj, avl_last_element(&path, obj, path), obj, path) {
+			/* Keep sending objects until buffering starts */
+			if (list_empty(&cl->tx_queue)) {
+				ubusd_send_obj(cl, ub, obj);
+			} else {
+				/* Queue command and continue on the next call */
+				int ret;
+
+				if (cmd == NULL) {
+					ret = ubus_client_cmd_queue_add(cl, ub, obj);
+				} else {
+					cmd->obj = obj;
+					ret = -2;
+				}
+				return ret;
+			}
+		}
 		return 0;
 	}
 
@@ -230,6 +270,40 @@ static int ubusd_handle_lookup(struct ubus_client *cl, struct ubus_msg_buf *ub,
 	return 0;
 }
 
+static int ubusd_handle_lookup(struct ubus_client *cl, struct ubus_msg_buf *ub, struct blob_attr **attr)
+{
+	int rc;
+
+	if (list_empty(&cl->tx_queue))
+		rc = __ubusd_handle_lookup(cl, ub, attr, NULL);
+	else
+		rc = ubus_client_cmd_queue_add(cl, ub, NULL);
+
+	return rc;
+}
+
+int ubusd_cmd_lookup(struct ubus_client *cl, struct ubus_client_cmd *cmd)
+{
+	struct ubus_msg_buf *ub = cmd->msg;
+	struct blob_attr **attr;
+	int ret;
+
+	attr = ubus_parse_msg(ub->data, blob_raw_len(ub->data));
+	ret = __ubusd_handle_lookup(cl, ub, attr, cmd);
+
+	if (ret != -2) {
+		struct ubus_msg_buf *retmsg = cl->retmsg;
+		int *retmsg_data = blob_data(blob_data(retmsg->data));
+
+		retmsg->hdr.seq = ub->hdr.seq;
+		retmsg->hdr.peer = ub->hdr.peer;
+
+		*retmsg_data = htonl(ret);
+		ubus_msg_send(cl, retmsg);
+	}
+	return ret;
+}
+
 static void
 ubusd_forward_invoke(struct ubus_client *cl, struct ubus_object *obj,
 		     const char *method, struct ubus_msg_buf *ub,
@@ -458,6 +532,10 @@ void ubusd_proto_receive_message(struct ubus_client *cl, struct ubus_msg_buf *ub
 	else
 		ret = UBUS_STATUS_INVALID_COMMAND;
 
+	/* Command has not been completed yet and got queued */
+	if (ret == -2)
+		return;
+
 	ubus_msg_free(ub);
 
 	if (ret == -1)
@@ -495,6 +573,7 @@ struct ubus_client *ubusd_proto_new_client(int fd, uloop_fd_handler cb)
 		goto free;
 
 	INIT_LIST_HEAD(&cl->objects);
+	INIT_LIST_HEAD(&cl->cmd_queue);
 	INIT_LIST_HEAD(&cl->tx_queue);
 	cl->sock.fd = fd;
 	cl->sock.cb = cb;