[LTP] [PATCH] netns_netlink: ensure child opens socket before parent creates tap if

[Jan Stancek]

There's a race, that allows parent to create/destroy tap interface
before child manages to open a netlink socket, and then child
will miss all events and test fails:
  tst_kconfig.c:82: TINFO: Parsing kernel config '/lib/modules/5.18.0-rc1/build/.config'
  tst_test.c:1456: TINFO: Timeout per run is 0h 10m 00s
  netns_netlink.c:88: TFAIL: failed to detect interface changes

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 testcases/kernel/containers/netns/netns_netlink.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/testcases/kernel/containers/netns/netns_netlink.c b/testcases/kernel/containers/netns/netns_netlink.c
index 7c90fb075ff9..6f60ff94ef6c 100644
--- a/testcases/kernel/containers/netns/netns_netlink.c
+++ b/testcases/kernel/containers/netns/netns_netlink.c
@@ -57,7 +57,7 @@ static void child_func(void)
 	SAFE_BIND(fd, (struct sockaddr *) &sa, sizeof(sa));
 
 	/* waits for parent to create an interface */
-	TST_CHECKPOINT_WAIT(0);
+	TST_CHECKPOINT_WAKE_AND_WAIT(0);
 
 	/*
 	 * To get rid of "resource temporarily unavailable" errors
@@ -98,6 +98,9 @@ static void test_netns_netlink(void)
 	if (SAFE_FORK() == 0)
 		child_func();
 
+	/* wait until child opens netlink socket */
+	TST_CHECKPOINT_WAIT(0);
+
 	/* creates TAP network interface dummy0 */
 	if (WEXITSTATUS(system("ip tuntap add dev dummy0 mode tap")))
 		tst_brk(TBROK, "adding interface failed");
-- 
2.27.0