linux-kernel - Re: [PATCH] selftests: net: forwarding: cleanup veth peers created via NUM

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Message-ID: <aXAsb+sCbyeD/xkL@devvm11784.nha0.facebook.com>
Date: Tue, 20 Jan 2026 17:31:27 -0800
From: Bobby Eshleman <bobbyeshleman@...il.com>
To: Aleksei Oladko <aleksey.oladko@...tuozzo.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
	Petr Machata <petrm@...dia.com>, netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: net: forwarding: cleanup veth peers created
 via NUM_NETIFS

On Tue, Jan 20, 2026 at 11:09:05PM +0000, Aleksei Oladko wrote:
> Some net/forwarding kselftests set NUM_NETIFS, causing lib.sh to create
> the requested number of veth peer interfaces.
> 
> These interfaces are not removed when the tests finish, leaving stale
> veth devices in the system. This can cause subsequent tests to fail,
> for example min_max_mtu.sh.
> 
> Ensure that veth peers created via NUM_NETIFS are properly removed at
> the end of the tests to avoid interference between test runs.
> 
> Signed-off-by: Aleksei Oladko <aleksey.oladko@...tuozzo.com>
> ---
>  tools/testing/selftests/net/forwarding/lib.sh | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh
> index a9034f0bb58b..ae7699c0c7e5 100644
> --- a/tools/testing/selftests/net/forwarding/lib.sh
> +++ b/tools/testing/selftests/net/forwarding/lib.sh
> @@ -597,6 +597,10 @@ vrf_cleanup()
>  	ip -6 rule del pref 32765
>  	ip -4 rule add pref 0 table local
>  	ip -4 rule del pref 32765
> +
> +	for ((i = 1; i <= NUM_NETIFS; i=$i+2)); do

I'd suggest 'i = i + 2' here instead of "i=$i+2", as it seems closer to the rest of lib.sh
style.

> +		ip link delete dev ${NETIFS[p$i]} 2>/dev/null || true
> +	done
>  }
>  
>  adf_vrf_prepare()
> -- 
> 2.43.0
> 

I see that some tests that set NUM_NETIFS do not seem to call
vrf_cleanup() (e.g. bridge_activity_notify.sh), so I think those tests
will still leak?

Maybe lib.sh needs a remove_netif() to go along with create_netif(), and
then tests can call it from their 'cleanup()' EXIT handlers? This avoids
the mismatch between vrf_prepare() not creating devices but
vrf_cleanup() removing them.

Thanks,
Bobby