On Mon, Apr 3, 2023 at 2:59 PM YiFei Zhu <zhuyifei@xxxxxxxxxx> wrote: > > 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 increaing 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 polling on the receive end and waiting for up to a > second, instead of instantly returning to the assert. > > [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") > Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx> Thank you! Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> > --- > .../testing/selftests/bpf/prog_tests/cg_storage_multi.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > 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 621c57222191..3b0094a2a353 100644 > --- a/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c > +++ b/tools/testing/selftests/bpf/prog_tests/cg_storage_multi.c > @@ -7,6 +7,7 @@ > #include <test_progs.h> > #include <cgroup_helpers.h> > #include <network_helpers.h> > +#include <poll.h> > > #include "progs/cg_storage_multi.h" > > @@ -56,8 +57,9 @@ 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; > + struct pollfd pollfd; > + bool res = true; > > if (join_cgroup(cgroup_path)) > goto out_clean; > @@ -73,6 +75,11 @@ static bool connect_send(const char *cgroup_path) > if (send(client_fd, "message", strlen("message"), 0) < 0) > goto out_clean; > > + pollfd.fd = server_fd; > + pollfd.events = POLLIN; > + if (poll(&pollfd, 1, 1000) != 1) > + goto out_clean; > + > res = false; > > out_clean: > -- > 2.40.0.348.gf938b09366-goog >
