Merge branch 'vsock-test-improve-sigpipe-test-reliability'

Stefano Garzarella says:

====================
vsock/test: improve sigpipe test reliability

Running the tests continuously I noticed that sometimes the sigpipe
test would fail due to a race between the control message of the test
and the vsock transport messages.

While I was at it I also improved the test by checking the errno we
expect.

v1: https://lore.kernel.org/20250508142005.135857-1-sgarzare@redhat.com
====================

Link: https://patch.msgid.link/20250514141927.159456-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 38 insertions, 8 deletions

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 613551132a96..9ea33b78b9fc 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1058,18 +1058,39 @@ static void sigpipe(int signo)
 	have_sigpipe = 1;
 }
 
+#define SEND_SLEEP_USEC (10 * 1000)
+
 static void test_stream_check_sigpipe(int fd)
 {
 	ssize_t res;
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, 0);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
+	/* When the other peer calls shutdown(SHUT_RD), there is a chance that
+	 * the send() call could occur before the message carrying the close
+	 * information arrives over the transport. In such cases, the send()
+	 * might still succeed. To avoid this race, let's retry the send() call
+	 * a few times, ensuring the test is more reliable.
+	 */
+	timeout_begin(TIMEOUT);
+	while(1) {
+		res = send(fd, "A", 1, 0);
+		if (res == -1 && errno != EINTR)
+			break;
+
+		/* Sleep a little before trying again to avoid flooding the
+		 * other peer and filling its receive buffer, causing
+		 * false-negative.
+		 */
+		timeout_usleep(SEND_SLEEP_USEC);
+		timeout_check("send");
 	}
+	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (!have_sigpipe) {
 		fprintf(stderr, "SIGPIPE expected\n");
 		exit(EXIT_FAILURE);
@@ -1077,12 +1098,21 @@ static void test_stream_check_sigpipe(int fd)
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, MSG_NOSIGNAL);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
+	timeout_begin(TIMEOUT);
+	while(1) {
+		res = send(fd, "A", 1, MSG_NOSIGNAL);
+		if (res == -1 && errno != EINTR)
+			break;
+
+		timeout_usleep(SEND_SLEEP_USEC);
+		timeout_check("send");
 	}
+	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (have_sigpipe) {
 		fprintf(stderr, "SIGPIPE not expected\n");
 		exit(EXIT_FAILURE);