Re: [PATCH bpf-next v2] selftests/bpf: Fix spurious failures in accept due to EAGAIN
From: Andrii Nakryiko <hidden>
Date: 2020-03-13 19:01:55
Also in:
bpf
On Fri, Mar 13, 2020 at 9:10 AM Jakub Sitnicki [off-list ref] wrote:
Andrii Nakryiko reports that sockmap_listen test suite is frequently
failing due to accept() calls erroring out with EAGAIN:
./test_progs:connect_accept_thread:733: accept: Resource temporarily unavailable
connect_accept_thread:FAIL:733
This is because we are using a non-blocking listening TCP socket to
accept() connections without polling on the socket.
While at first switching to blocking mode seems like the right thing to do,
this could lead to test process blocking indefinitely in face of a network
issue, like loopback interface being down, as Andrii pointed out.
Hence, stick to non-blocking mode for TCP listening sockets but with
polling for incoming connection for a limited time before giving up.
Apply this approach to all socket I/O calls in the test suite that we
expect to block indefinitely, that is accept() for TCP and recv() for UDP.
Fixes: 44d28be2b8d4 ("selftests/bpf: Tests for sockmap/sockhash holding listening sockets")
Reported-by: Andrii Nakryiko <redacted>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---This looks good. Unfortunately can't repro the issue locally anymore. But once this gets into bpf-next and we update libbpf in Github, I'll enable sockmap_listen tests again and see if it's still flaky. Thanks for following up! Stanislav, would you get a chance to do something similar for tcp_rtt as well? Seems like all the tests dealing with sockets might use this approach? Acked-by: Andrii Nakryiko <redacted>
quoted hunk ↗ jump to hunk
Notes: v2: Switch back to non-blocking mode, but with polling and timeout. Extend the fix to all I/O calls that we expect to block. (Andrii) .../selftests/bpf/prog_tests/sockmap_listen.c | 77 ++++++++++++++----- 1 file changed, 58 insertions(+), 19 deletions(-)diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c index 52aa468bdccd..d7d65a700799 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c@@ -16,6 +16,7 @@
[...]