Revert "[nrf noup] bluetooth: conn: Skip buffer ref count check in send_buf"

This reverts commit 687cefa.

Signed-off-by: Pavel Vasilyev <[email protected]>

Author: PavelVPV

subsys/bluetooth/host/conn.c

@@ -695,17 +695,13 @@ static int send_buf(struct bt_conn *conn, struct net_buf *buf,
 
 	uint16_t frag_len = MIN(conn_mtu(conn), len);
 
-	/* If ATT sent callback is delayed until data transmission is done by BLE controller, the
-	 * transmitted buffer may have an additional reference. The reference is used to extend
-	 * lifetime of the net buffer until the data transmission is confirmed by ACK of the remote.
-	 *
-	 * send_buf function can be called multiple times, if buffer has to be fragmented over HCI.
-	 * In that case, the callback is provided as an argument only for the last transmitted
-	 * fragment. The `buf->ref == 1` check is skipped because it's impossible to properly
-	 * validate number of references for the sent fragments if buffers may have the additional
-	 * reference.
-	 */
-	__ASSERT_NO_MSG(IS_ENABLED(CONFIG_BT_ATT_SENT_CB_AFTER_TX) || (buf->ref == 1));
+	if (buf->ref > 1 + (cb ? 1 : 0)) {
+		/* Allow for an additional buffer reference if callback is provided.
+		 * This can be used to extend lifetime of the net buffer until the
+		 * data transmission is confirmed by ACK of the remote.
+		 */
+		__ASSERT_NO_MSG(false);
+	}
 
 	if (buf->len > frag_len) {
 		LOG_DBG("keep %p around", buf);