[dpdk-dev] [PATCH v2] telemetry: fix "in-memory" process socket conflicts

[Bruce Richardson <bruce.richardson@intel.com>]

When DPDK is run with --in-memory mode, multiple processes can run
simultaneously using the same runtime dir. This leads to each process
removing another process' telemetry socket as it started up, giving
unexpected behaviour.

This patch changes that behaviour to first check if the existing socket
is active. If not, it's an old socket to be cleaned up and can be
removed. If it is active, telemetry initialization fails and an error
message is printed out giving instructions on how to remove the error;
either by using file-prefix to have a different runtime dir (and
therefore socket path) or by disabling telemetry if it not needed.

Fixes: 6dd571fd07c3 ("telemetry: introduce new functionality")
Cc: stable@dpdk.org

Reported-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
v2: fix build error on FreeBSD
---
 lib/telemetry/telemetry.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
index 8304fbf6e9..78508c1a1d 100644
--- a/lib/telemetry/telemetry.c
+++ b/lib/telemetry/telemetry.c
@@ -457,15 +457,30 @@ create_socket(char *path)
 
 	struct sockaddr_un sun = {.sun_family = AF_UNIX};
 	strlcpy(sun.sun_path, path, sizeof(sun.sun_path));
-	unlink(sun.sun_path);
+
 	if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
 		struct stat st;
 
-		TMTY_LOG(ERR, "Error binding socket: %s\n", strerror(errno));
-		if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode))
+		/* first check if we have a runtime dir */
+		if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode)) {
 			TMTY_LOG(ERR, "Cannot access DPDK runtime directory: %s\n", socket_dir);
-		sun.sun_path[0] = 0;
-		goto error;
+			goto error;
+		}
+
+		/* check if current socket is active */
+		if (connect(sock, (void *)&sun, sizeof(sun)) == 0) {
+			TMTY_LOG(ERR, "Error binding telemetry socket, path already in use\n");
+			TMTY_LOG(ERR, "Use '--file-prefix' to select a different socket path, or '--no-telemetry' to disable\n");
+			path[0] = 0;
+			goto error;
+		}
+
+		/* socket is not active, delete and attempt rebind */
+		unlink(sun.sun_path);
+		if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
+			TMTY_LOG(ERR, "Error binding socket: %s\n", strerror(errno));
+			goto error;
+		}
 	}
 
 	if (listen(sock, 1) < 0) {
-- 
2.32.0