From: YiFei Zhu <zhuyifei@xxxxxxxxxx> [ Upstream commit 5af607a861d43ffff830fc1890033e579ec44799 ] In some cases the loopback latency might be large enough, causing the assertion on invocations to be run before ingress prog getting executed. The assertion would fail and the test would flake. This can be reliably reproduced by arbitrarily increasing the loopback latency (thanks to [1]): tc qdisc add dev lo root handle 1: htb default 12 tc class add dev lo parent 1:1 classid 1:12 htb rate 20kbps ceil 20kbps tc qdisc add dev lo parent 1:12 netem delay 100ms Fix this by waiting on the receive end, instead of instantly returning to the assert. The call to read() will wait for the default SO_RCVTIMEO timeout of 3 seconds provided by start_server(). [1] https://gist.github.com/kstevens715/4598301 Reported-by: Martin KaFai Lau <martin.lau@xxxxxxxxx> Link: https://lore.kernel.org/bpf/9c5c8b7e-1d89-a3af-5400-14fde81f4429@xxxxxxxxx/ Fixes: 3573f384014f ("selftests/bpf: Test CGROUP_STORAGE behavior on shared egress + ingress") Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230405193354.1956209-1-zhuyifei@xxxxxxxxxx Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c index 621c572221918..63ee892bc7573 100644 --- a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c +++ b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c @@ -56,8 +56,9 @@ static bool assert_storage_noexist(struct bpf_map *map, const void *key) static bool connect_send(const char *cgroup_path) { - bool res = true; int server_fd = -1, client_fd = -1; + char message[] = "message"; + bool res = true; if (join_cgroup(cgroup_path)) goto out_clean; @@ -70,7 +71,10 @@ static bool connect_send(const char *cgroup_path) if (client_fd < 0) goto out_clean; - if (send(client_fd, "message", strlen("message"), 0) < 0) + if (send(client_fd, &message, sizeof(message), 0) < 0) + goto out_clean; + + if (read(server_fd, &message, sizeof(message)) < 0) goto out_clean; res = false; -- 2.39.2
