Bluetooth: SDP: Notify partial records if RX buf is full

In current implementation, if the response total data length is more
than the receiving buffer size, the request cannot be completed
properly.

Improve the SDP client with the following changes,
o Notify the received completed SDP records if the case occurs, and
  then start the continuing SDP discovery,
o Stop the SDP discovery if the hold SDP record cannot be saved to the
  receiving buffer,
o Stop the SDP discovery if the `BT_SDP_DISCOVER_UUID_STOP` is
  returned by upper layer.

Signed-off-by: Lyle Zhu <[email protected]>

Author: lylezhu2012

subsys/bluetooth/host/classic/sdp.c

@@ -2051,10 +2051,11 @@ static uint16_t get_record_len(struct bt_sdp_client *session)
 enum uuid_state {
 	UUID_NOT_RESOLVED,
 	UUID_RESOLVED,
+	UUID_PARTIAL_RESOLVED,
 };
 
-static void sdp_client_notify_result(struct bt_sdp_client *session,
-				     enum uuid_state state)
+static int sdp_client_notify_result(struct bt_sdp_client *session,
+				    enum uuid_state state)
 {
 	struct bt_conn *conn = session->chan.chan.conn;
 	struct bt_sdp_client_result result;
@@ -2065,17 +2066,61 @@ static void sdp_client_notify_result(struct bt_sdp_client *session,
 		result.resp_buf = NULL;
 		result.next_record_hint = false;
 		session->param->func(conn, &result, session->param);
-		return;
+		return 0;
 	}
 
 	while (session->rec_buf->len) {
 		struct net_buf_simple_state buf_state;
 
+		net_buf_simple_save(&session->rec_buf->b, &buf_state);
 		rec_len = get_record_len(session);
 		/* tell the user about multi record resolution */
 		if (session->rec_buf->len > rec_len) {
 			result.next_record_hint = true;
 		} else {
+			if (state == UUID_PARTIAL_RESOLVED) {
+				struct net_buf *buf;
+				uint8_t *src, *dst;
+				uint16_t len;
+
+				net_buf_simple_restore(&session->rec_buf->b, &buf_state);
+				/* Partial resolution, continue processing */
+				src = session->rec_buf->data;
+				len = session->rec_buf->len;
+
+				/* The allocated buffer is full. Try to allocate a new buffer from
+				 * the same pool. Use allocated buffer to continue the SDP
+				 * discovery if the new buffer allocated. Otherwise, use the
+				 * current allocated to continue the SDP discovery.
+				 */
+				buf = net_buf_alloc(session->param->pool, K_NO_WAIT);
+				if (buf != NULL) {
+					if (net_buf_tailroom(buf) < len) {
+						LOG_ERR("No more buffer space for SDP discover. "
+							"Need to increase buffer size of the "
+							"receiving pool.");
+						net_buf_unref(buf);
+						return -ENOMEM;
+					}
+					net_buf_add_mem(buf, src, len);
+					net_buf_unref(session->rec_buf);
+					session->rec_buf = buf;
+					LOG_DBG("Continue discovery with new buf %p", buf);
+					return 0;
+				}
+
+				net_buf_reset(session->rec_buf);
+				dst = net_buf_add(session->rec_buf, len);
+				if (dst == src) {
+					LOG_ERR("No more buffer space for SDP discover. Need to "
+						"increase buffer size of the receiving pool.");
+					return -ENOMEM;
+				}
+
+				memmove(dst, src, len);
+				LOG_DBG("Continue discovery with current buf");
+				return 0;
+			}
 			result.next_record_hint = false;
 		}
 
@@ -2100,9 +2145,11 @@ static void sdp_client_notify_result(struct bt_sdp_client *session,
 		 */
 		net_buf_pull(session->rec_buf, rec_len);
 		if (user_ret == BT_SDP_DISCOVER_UUID_STOP) {
-			break;
+			return -ECANCELED;
 		}
 	}
+
+	return 0;
 }
 
 static int sdp_client_discover(struct bt_sdp_client *session)
@@ -2264,6 +2311,11 @@ static int sdp_client_receive_ss(struct bt_sdp_client *session, struct net_buf *
 	return 0;
 }
 
+static int sdp_client_ssa_sa_notify(struct bt_sdp_client *session)
+{
+	return sdp_client_notify_result(session, UUID_PARTIAL_RESOLVED);
+}
+
 static int sdp_client_receive_ssa_sa(struct bt_sdp_client *session, struct net_buf *buf)
 {
 	struct bt_sdp_pdu_cstate *cstate;
@@ -2284,7 +2336,7 @@ static int sdp_client_receive_ssa_sa(struct bt_sdp_client *session, struct net_b
 		return -EINVAL;
 	}
 	/* Check valid range of attributes length */
-	if (((session->cstate.length == 0) && (frame_len < 2)) || (frame_len == 0)) {
+	if ((session->cstate.length == 0) && (frame_len < 2)) {
 		LOG_ERR("Invalid attributes data length");
 		return -EINVAL;
 	}
@@ -2302,6 +2354,22 @@ static int sdp_client_receive_ssa_sa(struct bt_sdp_client *session, struct net_b
 		return -EINVAL;
 	}
 
+	/* No more data found for given UUID and Continuation State length is not zero.
+	 * It means the remaining tailroom of the RX buffer is not enough to store the data.
+	 * Try to notify the received data, and request the next portion of data by sending a
+	 * continuation request.
+	 */
+	if (frame_len == 0 && cstate->length != 0) {
+		/* Notify current received data */
+		int err;
+
+		err = sdp_client_ssa_sa_notify(session);
+		if (err != 0) {
+			LOG_ERR("Failed to notify received data: %d", err);
+			return err;
+		}
+	}
+
 	/*
 	 * No record found for given UUID. The check catches case when
 	 * current response frame has Continuation State shortest and