[PATCH AUTOSEL 5.4 071/330] selftests/bpf: De-flake test_tcpbpf

Sasha Levin
2020-09-18T02:02:40Z

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit ef8c84effce3c7a0b8196fcda8f430c815ab511c ]

It looks like BPF program that handles BPF_SOCK_OPS_STATE_CB state
can race with the bpf_map_lookup_elem("global_map"); I sometimes
see the failures in this test and re-running helps.

Since we know that we expect the callback to be called 3 times (one
time for listener socket, two times for both ends of the connection),
let's export this number and add simple retry logic around that.

Also, let's make EXPECT_EQ() not return on failure, but continue
evaluating all conditions; that should make potential debugging
easier.

With this fix in place I don't observe the flakiness anymore.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: Lawrence Brakmo <brakmo@fb.com>
Link: https://lore.kernel.org/bpf/20191204190955.170934-1-sdf@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../selftests/bpf/progs/test_tcpbpf_kern.c | 1 +
tools/testing/selftests/bpf/test_tcpbpf.h | 1 +
.../testing/selftests/bpf/test_tcpbpf_user.c | 25 +++++++++++++------
3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
index 2e233613d1fc0..7fa4595d2b66b 100644
--- a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c
@@ -131,6 +131,7 @@ int bpf_testcb(struct bpf_sock_ops *skops)
g.bytes_received = skops->bytes_received;
g.bytes_acked = skops->bytes_acked;
}
+ g.num_close_events++;
bpf_map_update_elem(&global_map, &key, &g,
BPF_ANY);
}
diff --git a/tools/testing/selftests/bpf/test_tcpbpf.h b/tools/testing/selftests/bpf/test_tcpbpf.h
index 7bcfa62070056..6220b95cbd02c 100644
--- a/tools/testing/selftests/bpf/test_tcpbpf.h
+++ b/tools/testing/selftests/bpf/test_tcpbpf.h
@@ -13,5 +13,6 @@ struct tcpbpf_globals {
__u64 bytes_received;
__u64 bytes_acked;
__u32 num_listen;
+ __u32 num_close_events;
};
#endif
diff --git a/tools/testing/selftests/bpf/test_tcpbpf_user.c b/tools/testing/selftests/bpf/test_tcpbpf_user.c
index 716b4e3be5813..3ae127620463d 100644
--- a/tools/testing/selftests/bpf/test_tcpbpf_user.c
+++ b/tools/testing/selftests/bpf/test_tcpbpf_user.c
@@ -16,6 +16,9 @@

#include "test_tcpbpf.h"

+/* 3 comes from one listening socket + both ends of the connection */
+#define EXPECTED_CLOSE_EVENTS 3
+
#define EXPECT_EQ(expected, actual, fmt) \
do { \
if ((expected) != (actual)) { \
@@ -23,13 +26,14 @@
" Actual: %" fmt "\n" \
" Expected: %" fmt "\n", \
(actual), (expected)); \
- goto err; \
+ ret--; \
} \
} while (0)

int verify_result(const struct tcpbpf_globals *result)
{
__u32 expected_events;
+ int ret = 0;

expected_events = ((1 << BPF_SOCK_OPS_TIMEOUT_INIT) |
(1 << BPF_SOCK_OPS_RWND_INIT) |
@@ -48,15 +52,15 @@ int verify_result(const struct tcpbpf_globals *result)
EXPECT_EQ(0x80, result->bad_cb_test_rv, PRIu32);
EXPECT_EQ(0, result->good_cb_test_rv, PRIu32);
EXPECT_EQ(1, result->num_listen, PRIu32);
+ EXPECT_EQ(EXPECTED_CLOSE_EVENTS, result->num_close_events, PRIu32);

- return 0;
-err:
- return -1;
+ return ret;
}

int verify_sockopt_result(int sock_map_fd)
{
__u32 key = 0;
+ int ret = 0;
int res;
int rv;

@@ -69,9 +73,7 @@ int verify_sockopt_result(int sock_map_fd)
rv = bpf_map_lookup_elem(sock_map_fd, &key, &res);
EXPECT_EQ(0, rv, "d");
EXPECT_EQ(1, res, "d");
- return 0;
-err:
- return -1;
+ return ret;
}

static int bpf_find_map(const char *test, struct bpf_object *obj,
@@ -96,6 +98,7 @@ int main(int argc, char **argv)
int error = EXIT_FAILURE;
struct bpf_object *obj;
int cg_fd = -1;
+ int retry = 10;
__u32 key = 0;
int rv;

@@ -134,12 +137,20 @@ int main(int argc, char **argv)
if (sock_map_fd < 0)
goto err;

+retry_lookup:
rv = bpf_map_lookup_elem(map_fd, &key, &g);
if (rv != 0) {
printf("FAILED: bpf_map_lookup_elem returns %d\n", rv);
goto err;
}

+ if (g.num_close_events != EXPECTED_CLOSE_EVENTS && retry--) {
+ printf("Unexpected number of close events (%d), retrying!\n",
+ g.num_close_events);
+ usleep(100);
+ goto retry_lookup;
+ }
+
if (verify_result(&g)) {
printf("FAILED: Wrong stats\n");
goto err;
--
2.25.1