Re: [PATCH bpf v3 1/2] selftests/bpf: keep polling connection that is still in progress

On 8/11/26 10:26 PM, Alexis Lothoré (eBPF Foundation) wrote:
> Some tests, like tc_tunnel or tc_edt, sporadically fail in CI with the
> following logs:
>
>    (network_helpers.c:309: errno: Operation now in progress) \
>      Failed to connect to server
>    send_and_test_data:FAIL:connect to server unexpected error: -115
>
> This is due to SO_RCVTIMEO and SO_SNDTIMEO being set on the client
> socket (see settimeo() in client_socket()), allowing connect() to return
> an error and to set errno to EINPROGRESS instead of blocking until
> connection result is known. Increasing the timeout value for those tests
> is likely not a good solution (and it has already been done by commit
> 2790db208b44 ("selftests/bpf: Improve tc_tunnel test reliability")):
> they involve subtests that expect the connection to fail, and so
> increasing the timeout value would increase overall test execution
> duration again (not only the connection, but any socket operation).
>
> Another solution, as documented in man 2 connect, is to poll the socket
> for POLLOUT once connect has returned EINPROGRESS, and to get the actual
> connection result through getsockopt: this allows to keep the overall
> timeout values low for the general traffic, while letting a chance to
> the connection to succeed even if CI runners are loaded.
>
> When connect() returns EINPROGRESS, poll the socket for POLLOUT and
> check the connection result via getsockopt(SO_ERROR). This new handling
> conforms to the configured timeout: the polling loop will only run for
> the amount of time still available, accounting for the time used by the
> initial connect() call.


So IIUC this patch doesn't actually fix the flakiness: connect() on a 
blocking socket only
returns EINPROGRESS after SO_SNDTIMEO is fully consumed, so remaining_ms 
is always ~0 and the
overall time budget is still 1s, same as before. Am I missing something?