netdev - [PATCH net 1/4] selftests/tcp_ao: Make RST tests less flaky

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Message-Id: <20240413-tcp-ao-selftests-fixes-v1-1-f9c41c96949d@gmail.com>
Date: Sat, 13 Apr 2024 02:42:52 +0100
From: Dmitry Safonov via B4 Relay <devnull+0x7f454c46.gmail.com@...nel.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Dmitry Safonov <0x7f454c46@...il.com>
Subject: [PATCH net 1/4] selftests/tcp_ao: Make RST tests less flaky

From: Dmitry Safonov <0x7f454c46@...il.com>

Currently, "active reset" cases are flaky, because select() is called
for 3 sockets, while only 2 are expected to receive RST.
The idea of the third socket was to get into request_sock_queue,
but the test mistakenly attempted to connect() after the listener
socket was shut down.

Repair this test, it's important to check the different kernel
code-paths for signing RST TCP-AO segments.

Fixes: c6df7b2361d7 ("selftests/net: Add TCP-AO RST test")
Reported-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Dmitry Safonov <0x7f454c46@...il.com>
---
 tools/testing/selftests/net/tcp_ao/rst.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_ao/rst.c b/tools/testing/selftests/net/tcp_ao/rst.c
index 7df8b8700e39..a2fe88d35ac0 100644
--- a/tools/testing/selftests/net/tcp_ao/rst.c
+++ b/tools/testing/selftests/net/tcp_ao/rst.c
@@ -256,8 +256,6 @@ static int test_wait_fds(int sk[], size_t nr, bool is_writable[],
 
 static void test_client_active_rst(unsigned int port)
 {
-	/* one in queue, another accept()ed */
-	unsigned int wait_for = backlog + 2;
 	int i, sk[3], err;
 	bool is_writable[ARRAY_SIZE(sk)] = {false};
 	unsigned int last = ARRAY_SIZE(sk) - 1;
@@ -275,16 +273,20 @@ static void test_client_active_rst(unsigned int port)
 	for (i = 0; i < last; i++) {
 		err = _test_connect_socket(sk[i], this_ip_dest, port,
 					       (i == 0) ? TEST_TIMEOUT_SEC : -1);
-
 		if (err < 0)
 			test_error("failed to connect()");
 	}
 
-	synchronize_threads(); /* 2: connection accept()ed, another queued */
-	err = test_wait_fds(sk, last, is_writable, wait_for, TEST_TIMEOUT_SEC);
+	synchronize_threads(); /* 2: two connections: one accept()ed, another queued */
+	err = test_wait_fds(sk, last, is_writable, last, TEST_TIMEOUT_SEC);
 	if (err < 0)
 		test_error("test_wait_fds(): %d", err);
 
+	/* async connect() with third sk to get into request_sock_queue */
+	err = _test_connect_socket(sk[last], this_ip_dest, port, -1);
+	if (err < 0)
+		test_error("failed to connect()");
+
 	synchronize_threads(); /* 3: close listen socket */
 	if (test_client_verify(sk[0], packet_sz, quota / packet_sz, TEST_TIMEOUT_SEC))
 		test_fail("Failed to send data on connected socket");
@@ -292,13 +294,14 @@ static void test_client_active_rst(unsigned int port)
 		test_ok("Verified established tcp connection");
 
 	synchronize_threads(); /* 4: finishing up */
-	err = _test_connect_socket(sk[last], this_ip_dest, port, -1);
-	if (err < 0)
-		test_error("failed to connect()");
 
 	synchronize_threads(); /* 5: closed active sk */
-	err = test_wait_fds(sk, ARRAY_SIZE(sk), NULL,
-			    wait_for, TEST_TIMEOUT_SEC);
+	/*
+	 * Wait for 2 connections: one accepted, another in the accept queue,
+	 * the one in request_sock_queue won't get fully established, so
+	 * doesn't receive an active RST, see inet_csk_listen_stop().
+	 */
+	err = test_wait_fds(sk, last, NULL, last, TEST_TIMEOUT_SEC);
 	if (err < 0)
 		test_error("select(): %d", err);
 

-- 
2.42.0