vsock/test: Expand linger test to ensure close() does not misbehave

There was an issue with SO_LINGER: instead of blocking until all queued
messages for the socket have been successfully sent (or the linger timeout
has been reached), close() would block until packets were handled by the
peer.

Add a check to alert on close() lingering when it should not.

Signed-off-by: Michal Luczaj <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: mmhal

tools/testing/vsock/vsock_test.c

@@ -1788,13 +1788,16 @@ static void test_stream_connect_retry_server(const struct test_opts *opts)
 	close(fd);
 }
 
+#define	LINGER_TIMEOUT	1	/* seconds */
+
 static void test_stream_linger_client(const struct test_opts *opts)
 {
 	struct linger optval = {
 		.l_onoff = 1,
-		.l_linger = 1
+		.l_linger = LINGER_TIMEOUT
 	};
-	int fd;
+	int bytes_unsent, fd;
+	time_t ts;
 
 	fd = vsock_stream_connect(opts->peer_cid, opts->peer_port);
 	if (fd < 0) {
@@ -1807,7 +1810,28 @@ static void test_stream_linger_client(const struct test_opts *opts)
 		exit(EXIT_FAILURE);
 	}
 
+	/* Byte left unread to expose any incorrect behaviour. */
+	send_byte(fd, 1, 0);
+
+	/* Reuse LINGER_TIMEOUT to wait for bytes_unsent == 0. */
+	timeout_begin(LINGER_TIMEOUT);
+	do {
+		if (ioctl(fd, SIOCOUTQ, &bytes_unsent) < 0) {
+			perror("ioctl(SIOCOUTQ)");
+			exit(EXIT_FAILURE);
+		}
+		timeout_check("ioctl(SIOCOUTQ) == 0");
+	} while (bytes_unsent != 0);
+	timeout_end();
+
+	ts = current_nsec();
 	close(fd);
+	if ((current_nsec() - ts) / NSEC_PER_SEC > 0) {
+		fprintf(stderr, "Unexpected lingering on close()\n");
+		exit(EXIT_FAILURE);
+	}
+
+	control_writeln("DONE");
 }
 
 static void test_stream_linger_server(const struct test_opts *opts)
@@ -1820,7 +1844,7 @@ static void test_stream_linger_server(const struct test_opts *opts)
 		exit(EXIT_FAILURE);
 	}
 
-	vsock_wait_remote_close(fd);
+	control_expectln("DONE");
 	close(fd);
 }