From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 2 Mar 2022 17:59:17 +0000 (-0500)
Subject: Fix: relayd: connection abruptly closed on viewer stream creation failure
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=14e34907ffbc9645f8ed799b74e04d9c850df4f0

Fix: relayd: connection abruptly closed on viewer stream creation failure

Commit fe88e5175 explains (and fixes) an issue that could cause the
creation of viewer streams to fail. Currently, the error path causes the
relay daemon to abruptly close the connection to its live viewer peer.
This behaviour makes it impossible for the viewer to determine if an
error occurred or if the network connection simply failed.

Returning an `LTTNG_VIEWER_NEW_STREAMS_ERR` status code allows the
viewer to report a precise error. The viewer connection is closed since
the internal error is unlikely to be recoverable.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I557a8b66c1bd1c0bf361cfbabe962d8a6808f4f4
---

diff --git a/src/bin/lttng-relayd/live.cpp b/src/bin/lttng-relayd/live.cpp
index 5925642f0..e0d446b2a 100644
--- a/src/bin/lttng-relayd/live.cpp
+++ b/src/bin/lttng-relayd/live.cpp
@@ -1266,7 +1266,12 @@ int viewer_get_new_streams(struct relay_connection *conn)
 			LTTNG_VIEWER_SEEK_BEGINNING, &nb_total, &nb_unsent,
 			&nb_created, &closed);
 	if (ret < 0) {
-		goto error_unlock_session;
+		/*
+		 * This is caused by an internal error; propagate the negative
+		 * 'ret' to close the connection.
+		 */
+		response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_ERR);
+		goto send_reply;
 	}
 	send_streams = 1;
 	response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_OK);
@@ -1321,10 +1326,6 @@ end_put_session:
 	}
 error:
 	return ret;
-error_unlock_session:
-	pthread_mutex_unlock(&session->lock);
-	session_put(session);
-	return ret;
 }
 
 /*