[PATCH net v2] vsock/test: Fix occasional failure in SOCK_STREAM SHUT_RD test

[Konstantin Shkolnyy]

The test outputs:
"SOCK_STREAM SHUT_RD...expected send(2) failure, got 1".

It tests that shutdown(fd, SHUT_RD) on one side causes send() to fail on
the other side. However, sometimes there is a delay in delivery of the
SHUT_RD command, send() succeeds and the test fails, even though the
command is properly delivered and send() starts failing several
milliseconds later.

The delay occurs in the kernel because the used buffer notification
callback virtio_vsock_rx_done(), called upon receipt of the SHUT_RD
command, doesn't immediately disable send(). It delegates that to
a kernel thread (via vsock->rx_work). Sometimes that thread is delayed
more than the test expects.

Change the test to keep calling send() until it fails or a timeout occurs.

Fixes: b698bd97c5711 ("test/vsock: shutdowned socket test")
Signed-off-by: Konstantin Shkolnyy <k...@linux.ibm.com>
---
Changes in v2:
 - Move the new function to utils.c.

 tools/testing/vsock/util.c       | 11 +++++++++++
 tools/testing/vsock/util.h       |  1 +
 tools/testing/vsock/vsock_test.c | 14 ++------------
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
index de25892f865f..04ac88dc4d3a 100644
--- a/tools/testing/vsock/util.c
+++ b/tools/testing/vsock/util.c
@@ -798,3 +798,14 @@ void enable_so_zerocopy_check(int fd)
        setsockopt_int_check(fd, SOL_SOCKET, SO_ZEROCOPY, 1,
                             "setsockopt SO_ZEROCOPY");
 }
+
+void vsock_test_for_send_failure(int fd, int send_flags)
+{
+       timeout_begin(TIMEOUT);
+       while (true) {
+               if (send(fd, "A", 1, send_flags) == -1)
+                       return;
+               timeout_check("expected send(2) failure");
+       }
+       timeout_end();
+}
diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
index d1f765ce3eee..58c17cfb63d4 100644
--- a/tools/testing/vsock/util.h
+++ b/tools/testing/vsock/util.h
@@ -79,4 +79,5 @@ void setsockopt_int_check(int fd, int level, int optname, int 
val,
 void setsockopt_timeval_check(int fd, int level, int optname,
                              struct timeval val, char const *errmsg);
 void enable_so_zerocopy_check(int fd);
+void vsock_test_for_send_failure(int fd, int send_flags);
 #endif /* UTIL_H */
diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 613551132a96..b68a85a6d929 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1060,15 +1060,9 @@ static void sigpipe(int signo)
 
 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);
-       }
+       vsock_test_for_send_failure(fd, 0);
 
        if (!have_sigpipe) {
                fprintf(stderr, "SIGPIPE expected\n");
@@ -1077,11 +1071,7 @@ 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);
-       }
+       vsock_test_for_send_failure(fd, MSG_NOSIGNAL);
 
        if (have_sigpipe) {
                fprintf(stderr, "SIGPIPE not expected\n");
-- 
2.34.1