[PATCH 6.5.y] selftests: mptcp: join: correctly check for no RST

[Matthieu Baerts <matttbe@kernel.org>]

commit b134a5805455d1886662a6516c965cdb9df9fbcc upstream.

The commit mentioned below was more tolerant with the number of RST seen
during a test because in some uncontrollable situations, multiple RST
can be generated.

But it was not taking into account the case where no RST are expected:
this validation was then no longer reporting issues for the 0 RST case
because it is not possible to have less than 0 RST in the counter. This
patch fixes the issue by adding a specific condition.

Fixes: 6bf41020b72b ("selftests: mptcp: update and extend fastclose test-cases")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231018-send-net-20231018-v1-1-17ecb002e41d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
---
Backport notes:
  - Two conflicts due to 03668c65d153 ("selftests: mptcp: join: rework
    detailed report") introduced in v6.6. In previous versions, the
    messages are directly printed with echo. Here we only need to modify
    the conditions for the 'elif'.
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 5e55af3e9d5f..621b1964ea6f 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1383,7 +1383,9 @@ chk_rst_nr()
 	count=$(get_counter ${ns_tx} "MPTcpExtMPRstTx")
 	if [ -z "$count" ]; then
 		echo -n "[skip]"
-	elif [ $count -lt $rst_tx ]; then
+	# accept more rst than expected except if we don't expect any
+	elif { [ $rst_tx -ne 0 ] && [ $count -lt $rst_tx ]; } ||
+	     { [ $rst_tx -eq 0 ] && [ $count -ne 0 ]; }; then
 		echo "[fail] got $count MP_RST[s] TX expected $rst_tx"
 		fail_test
 	else
@@ -1394,7 +1396,9 @@ chk_rst_nr()
 	count=$(get_counter ${ns_rx} "MPTcpExtMPRstRx")
 	if [ -z "$count" ]; then
 		echo -n "[skip]"
-	elif [ "$count" -lt "$rst_rx" ]; then
+	# accept more rst than expected except if we don't expect any
+	elif { [ $rst_rx -ne 0 ] && [ $count -lt $rst_rx ]; } ||
+	     { [ $rst_rx -eq 0 ] && [ $count -ne 0 ]; }; then
 		echo "[fail] got $count MP_RST[s] RX expected $rst_rx"
 		fail_test
 	else
-- 
2.40.1