[PATCH net-next v4 7/8] selftests/net: Synchronize client/server before counters checks

Dmitry Safonov via B4 Relay
2024-08-23T22:05:19Z

On tests that are expecting failure the timeout value is
TEST_RETRANSMIT_SEC == 1 second. Which is big enough for most of devices
under tests. But on a particularly slow machine/VM, 1 second might be
not enough for another thread to be scheduled and attempt to connect().
It is not a problem for tests that expect connect() to succeed as
the timeout value for them (TEST_TIMEOUT_SEC) is intentionally bigger.

One obvious way to solve this would be to increase TEST_RETRANSMIT_SEC.
But as all tests would increase the timeouts, that's going to sum up.

But here is less obvious way that keeps timeouts for expected connect()
failures low: just synchronize the two threads, which will assure that
before counter checks the other thread got a chance to run and timeout
on connect(). The expected increase of the related counter for listen()
socket will yet test the expected failure.

Never happens on my machine, but I suppose the majority of netdev's
connect-deny-* flakes [1] are caused by this.

Prevents the following testing issue:
> # selftests: net/tcp_ao: connect-deny_ipv6
> # 1..21
> # # 462[lib/setup.c:243] rand seed 1720905426
> # TAP version 13
> # ok 1 Non-AO server + AO client
> # not ok 2 Non-AO server + AO client: TCPAOKeyNotFound counter did not increase: 0 <= 0
> # ok 3 AO server + Non-AO client
> # ok 4 AO server + Non-AO client: counter TCPAORequired increased 0 => 1
...

[1]: https://netdev-3.bots.linux.dev/vmksft-tcp-ao/results/681741/6-connect-deny-ipv6/stdout
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
---
tools/testing/selftests/net/tcp_ao/connect-deny.c | 3 +++
tools/testing/selftests/net/tcp_ao/restore.c | 6 ++++--
tools/testing/selftests/net/tcp_ao/seq-ext.c | 6 ++++--
tools/testing/selftests/net/tcp_ao/unsigned-md5.c | 3 +++
4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_ao/connect-deny.c b/tools/testing/selftests/net/tcp_ao/connect-deny.c
index 5691f3d00603..166ad4549ef2 100644
--- a/tools/testing/selftests/net/tcp_ao/connect-deny.c
+++ b/tools/testing/selftests/net/tcp_ao/connect-deny.c
@@ -71,10 +71,12 @@ static void try_accept(const char *tst_name, unsigned int port, const char *pwd,
}
}

+ synchronize_threads(); /* before counter checks */
if (pwd && test_get_tcp_ao_counters(lsk, &ao_cnt2))
test_error("test_get_tcp_ao_counters()");

close(lsk);
+
if (pwd)
test_tcp_ao_counters_cmp(tst_name, &ao_cnt1, &ao_cnt2, cnt_expected);

@@ -180,6 +182,7 @@ static void try_connect(const char *tst_name, unsigned int port,
timeout = fault(TIMEOUT) ? TEST_RETRANSMIT_SEC : TEST_TIMEOUT_SEC;
ret = _test_connect_socket(sk, this_ip_dest, port, timeout);

+ synchronize_threads(); /* before counter checks */
if (ret < 0) {
if (fault(KEYREJECT) && ret == -EKEYREJECTED) {
test_ok("%s: connect() was prevented", tst_name);
diff --git a/tools/testing/selftests/net/tcp_ao/restore.c b/tools/testing/selftests/net/tcp_ao/restore.c
index 7b91d7fde2bc..f6ea2190f43d 100644
--- a/tools/testing/selftests/net/tcp_ao/restore.c
+++ b/tools/testing/selftests/net/tcp_ao/restore.c
@@ -64,6 +64,7 @@ static void try_server_run(const char *tst_name, unsigned int port,
else
test_ok("%s: server alive", tst_name);
}
+ synchronize_threads(); /* 3: counters checks */
if (test_get_tcp_ao_counters(sk, &ao2))
test_error("test_get_tcp_ao_counters()");
after_cnt = netstat_get_one(cnt_name, NULL);
@@ -82,7 +83,7 @@ static void try_server_run(const char *tst_name, unsigned int port,
* Before close() as that will send FIN and move the peer in TCP_CLOSE
* and that will prevent reading AO counters from the peer's socket.
*/
- synchronize_threads(); /* 3: verified => closed */
+ synchronize_threads(); /* 4: verified => closed */
out:
close(sk);
}
@@ -176,6 +177,7 @@ static void test_sk_restore(const char *tst_name, unsigned int server_port,
else
test_ok("%s: post-migrate connection is alive", tst_name);
}
+ synchronize_threads(); /* 3: counters checks */
if (test_get_tcp_ao_counters(sk, &ao2))
test_error("test_get_tcp_ao_counters()");
after_cnt = netstat_get_one(cnt_name, NULL);
@@ -189,7 +191,7 @@ static void test_sk_restore(const char *tst_name, unsigned int server_port,
test_ok("%s: counter %s increased %" PRIu64 " => %" PRIu64,
tst_name, cnt_name, before_cnt, after_cnt);
}
- synchronize_threads(); /* 3: verified => closed */
+ synchronize_threads(); /* 4: verified => closed */
close(sk);
}

diff --git a/tools/testing/selftests/net/tcp_ao/seq-ext.c b/tools/testing/selftests/net/tcp_ao/seq-ext.c
index 9c7dde7fd776..885866cc193c 100644
--- a/tools/testing/selftests/net/tcp_ao/seq-ext.c
+++ b/tools/testing/selftests/net/tcp_ao/seq-ext.c
@@ -116,7 +116,7 @@ static void *server_fn(void *arg)
sk = test_sk_restore(&img, &ao_img, &saddr, this_ip_dest,
client_new_port, &ao1);

- synchronize_threads(); /* 5: verify counters during SEQ-number rollover */
+ synchronize_threads(); /* 5: verify the connection during SEQ-number rollover */
bytes = test_server_run(sk, quota, TEST_TIMEOUT_SEC);
if (bytes != quota) {
if (bytes > 0)
@@ -127,6 +127,7 @@ static void *server_fn(void *arg)
test_ok("server alive");
}

+ synchronize_threads(); /* 6: verify counters after SEQ-number rollover */
if (test_get_tcp_ao_counters(sk, &ao2))
test_error("test_get_tcp_ao_counters()");
after_good = netstat_get_one("TCPAOGood", NULL);
@@ -206,12 +207,13 @@ static void *client_fn(void *arg)
sk = test_sk_restore(&img, &ao_img, &saddr, this_ip_dest,
test_server_port + 1, &ao1);

- synchronize_threads(); /* 5: verify counters during SEQ-number rollover */
+ synchronize_threads(); /* 5: verify the connection during SEQ-number rollover */
if (test_client_verify(sk, msg_len, nr_packets, TEST_TIMEOUT_SEC))
test_fail("post-migrate verify failed");
else
test_ok("post-migrate connection alive");

+ synchronize_threads(); /* 5: verify counters after SEQ-number rollover */
if (test_get_tcp_ao_counters(sk, &ao2))
test_error("test_get_tcp_ao_counters()");
after_good = netstat_get_one("TCPAOGood", NULL);
diff --git a/tools/testing/selftests/net/tcp_ao/unsigned-md5.c b/tools/testing/selftests/net/tcp_ao/unsigned-md5.c
index ec2848036341..02346b58efbd 100644
--- a/tools/testing/selftests/net/tcp_ao/unsigned-md5.c
+++ b/tools/testing/selftests/net/tcp_ao/unsigned-md5.c
@@ -70,6 +70,7 @@ static void try_accept(const char *tst_name, unsigned int port,

timeout = fault(TIMEOUT) ? TEST_RETRANSMIT_SEC : TEST_TIMEOUT_SEC;
err = test_wait_fd(lsk, timeout, 0);
+ synchronize_threads(); /* connect()/accept() timeouts */
if (err == -ETIMEDOUT) {
if (!fault(TIMEOUT))
test_fail("timed out for accept()");
@@ -283,6 +284,7 @@ static void try_connect(const char *tst_name, unsigned int port,
timeout = fault(TIMEOUT) ? TEST_RETRANSMIT_SEC : TEST_TIMEOUT_SEC;
ret = _test_connect_socket(sk, this_ip_dest, port, timeout);

+ synchronize_threads(); /* connect()/accept() timeouts */
if (ret < 0) {
if (fault(KEYREJECT) && ret == -EKEYREJECTED)
test_ok("%s: connect() was prevented", tst_name);
@@ -451,6 +453,7 @@ static void try_to_add(const char *tst_name, unsigned int port,
timeout = fault(TIMEOUT) ? TEST_RETRANSMIT_SEC : TEST_TIMEOUT_SEC;
ret = _test_connect_socket(sk, this_ip_dest, port, timeout);

+ synchronize_threads(); /* connect()/accept() timeouts */
if (ret <= 0) {
test_error("%s: connect() returned %d", tst_name, ret);
goto out;

--
2.42.2