From: Cong Wang cong.wang@bytedance.com
[ Upstream commit a7e65fe7d8201527129206754db1a2db6a6b2fde ]
We use non-blocking sockets for testing sockmap redirections, and got some random EAGAIN errors from UDP tests.
There is no guarantee the packet would be immediately available to receive as soon as it is sent out, even on the local host. For UDP, this is especially true because it does not lock the sock during BH (unlike the TCP path). This is probably why we only saw this error in UDP cases.
No matter how hard we try to make the queue empty check accurate, it is always possible for recvmsg() to beat ->sk_data_ready(). Therefore, we should just retry in case of EAGAIN.
Fixes: d6378af615275 ("selftests/bpf: Add a test case for udp sockmap") Reported-by: Jiang Wang jiang.wang@bytedance.com Signed-off-by: Cong Wang cong.wang@bytedance.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: John Fastabend john.fastabend@gmail.com Acked-by: Jakub Sitnicki jakub@cloudflare.com Link: https://lore.kernel.org/bpf/20210615021342.7416-3-xiyou.wangcong@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/testing/selftests/bpf/prog_tests/sockmap_listen.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c index 648d9ae898d2..01ab11259809 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c @@ -1610,6 +1610,7 @@ static void udp_redir_to_connected(int family, int sotype, int sock_mapfd, struct sockaddr_storage addr; int c0, c1, p0, p1; unsigned int pass; + int retries = 100; socklen_t len; int err, n; u64 value; @@ -1686,9 +1687,13 @@ static void udp_redir_to_connected(int family, int sotype, int sock_mapfd, if (pass != 1) FAIL("%s: want pass count 1, have %d", log_prefix, pass);
+again: n = read(mode == REDIR_INGRESS ? p0 : c0, &b, 1); - if (n < 0) + if (n < 0) { + if (errno == EAGAIN && retries--) + goto again; FAIL_ERRNO("%s: read", log_prefix); + } if (n == 0) FAIL("%s: incomplete read", log_prefix);