On Fri, 2023-01-27 at 17:03 -0500, Willem de Bruijn wrote:

On Fri, Jan 27, 2023 at 1:16 PM Andrei Gherzan
[off-list ref] wrote:

quoted

The tx and rx test programs are used in a couple of test scripts including
"udpgro_bench.sh". Taking this as an example, when the rx/tx programs
are invoked subsequently, there is a chance that the rx one is not ready to
accept socket connections. This racing bug could fail the test with at
least one of the following:

./udpgso_bench_tx: connect: Connection refused
./udpgso_bench_tx: sendmsg: Connection refused
./udpgso_bench_tx: write: Connection refused

This change addresses this by adding routines that retry the socket
operations with an exponential back off algorithm from 100ms to 2s.

Fixes: 3a687bef148d ("selftests: udp gso benchmark")
Signed-off-by: Andrei Gherzan <redacted>

Synchronizing the two processes is indeed tricky.

Perhaps more robust is opening an initial TCP connection, with
SO_RCVTIMEO to bound the waiting time. That covers all tests in one
go.

Another option would be waiting for the listener(tcp)/receiver(udp)
socket to show up in 'ss' output before firing-up the client - quite
alike what mptcp self-tests are doing.

Cheers,

Paolo