[PATCH net 6/6] selftests: ovpn: serialize YNL listener startup

[Antonio Quartulli <antonio@openvpn.net>]

From: Ralf Lici <ralf@mandelbit.com>

Starting one background YNL notification listener per peer back-to-back
can intermittently stall the test setup before the listeners even reach
the Python main function.

This was reproducible in a reduced test.sh setup-only loop: a single
listener stayed stable across repeated runs, while starting listeners
for all peers could hang early in the listener launch phase. Adding a
short delay between listener launches makes the listeners start cleanly
and eliminates the reproduced hangs in repeated normal and slow-runner
tests.

Serialize listener startup with a small sleep between setup_listener
calls.

Fixes: 77de28cd7cf1 ("selftests: ovpn: add notification parsing and matching")
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
 tools/testing/selftests/net/ovpn/test.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/net/ovpn/test.sh b/tools/testing/selftests/net/ovpn/test.sh
index eca653112aeb..b50dbe45a4d0 100755
--- a/tools/testing/selftests/net/ovpn/test.sh
+++ b/tools/testing/selftests/net/ovpn/test.sh
@@ -31,6 +31,9 @@ ovpn_prepare_network() {
 	for p in $(seq 0 ${OVPN_NUM_PEERS}); do
 		ovpn_cmd_ok "start notification listener peer${p}" \
 			ovpn_setup_listener "${p}"
+		# starting all YNL listeners back-to-back can intermittently
+		# stall their startup so serialize launches a bit
+		sleep 0.5
 	done
 
 	for p in $(seq 0 ${OVPN_NUM_PEERS}); do
-- 
2.52.0