Re: [TEST] forwarding/router_bridge_lag.sh started to flake on Monday

[Petr Machata <petrm@nvidia.com>]

Jakub Kicinski <kuba@kernel.org> writes:

> Looks like forwarding/router_bridge_lag.sh has gotten a lot more flaky
> this week. It flaked very occasionally (and in a different way) before:
>
> https://netdev.bots.linux.dev/contest.html?executor=vmksft-forwarding&test=router-bridge-lag-sh&ld_cnt=250
>
> There doesn't seem to be any obvious commit that could have caused this.

Hmm:
    # 3.37 [+0.11] Error: Device is up. Set it down before adding it as a team port.

How are the tests isolated, are they each run in their own vng, or are
instances shared? Could it be that the test that runs befor this one
neglects to take a port down?

In one failure case (I don't see further back or my browser would
apparently catch fire) the predecessor was no_forwarding.sh, and indeed
it looks like it raises the ports, but I don't see where it sets them
back down.

Then router-bridge-lag's cleanup downs the ports, and on rerun it
succeeds. The issue would be probabilistic, because no_forwarding does
not always run before this test, and some tests do not care that the
ports are up. If that's the root cause, this should fix it:

From 0baf91dc24b95ae0cadfdf5db05b74888e6a228a Mon Sep 17 00:00:00 2001
Message-ID: <0baf91dc24b95ae0cadfdf5db05b74888e6a228a.1724413545.git.petrm@nvidia.com>
From: Petr Machata <petrm@nvidia.com>
Date: Fri, 23 Aug 2024 14:42:48 +0300
Subject: [PATCH net-next mlxsw] selftests: forwarding: no_forwarding: Down
 ports on cleanup
To: <nbu-linux-internal@nvidia.com>

This test neglects to put ports down on cleanup. Fix it.

Fixes: 476a4f05d9b8 ("selftests: forwarding: add a no_forwarding.sh test")
Signed-off-by: Petr Machata <petrm@nvidia.com>
---
 tools/testing/selftests/net/forwarding/no_forwarding.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/net/forwarding/no_forwarding.sh b/tools/testing/selftests/net/forwarding/no_forwarding.sh
index af3b398d13f0..9e677aa64a06 100755
--- a/tools/testing/selftests/net/forwarding/no_forwarding.sh
+++ b/tools/testing/selftests/net/forwarding/no_forwarding.sh
@@ -233,6 +233,9 @@ cleanup()
 {
 	pre_cleanup
 
+	ip link set dev $swp2 down
+	ip link set dev $swp1 down
+
 	h2_destroy
 	h1_destroy
 
-- 
2.45.0