[PATCH net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change

[PATCH net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change

[Haishuang Yan]

On slow machines, do_test() raises initcwnd on the route into the tunnel
with "ip route change". For IPv6 traffic this fails with:

  RTNETLINK answers: No such file or directory

The IPv6 prefix route of the tunnel address has metric 256, while
"ip -6 route change" without a metric looks for a route with the default
metric 1024, so nothing is changed. The test still passes, but without
the larger initcwnd it is meant to use.

Pass the metric of the prefix route.

Fixes: 1d62b83fb751 ("selftests: net: Fix slow configurations in big_tcp_tunnels.sh")
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
---
 tools/testing/selftests/net/big_tcp_tunnels.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/big_tcp_tunnels.sh b/tools/testing/selftests/net/big_tcp_tunnels.sh
index cc0875e52fb9..fb43fed824e3 100755
--- a/tools/testing/selftests/net/big_tcp_tunnels.sh
+++ b/tools/testing/selftests/net/big_tcp_tunnels.sh
@@ -145,7 +145,8 @@ do_test() {
 			    route change 192.168.2.0/24 dev tun0 initcwnd 100
 		else
 			ip -netns "$CLIENT_NS" -6 \
-			    route change 2001:db8::2:0/112 dev tun0 initcwnd 100
+			    route change 2001:db8::2:0/112 dev tun0 initcwnd 100 \
+			    metric 256
 		fi
 	else
 		ip netns exec "$CLIENT_NS" \
-- 
2.43.0

Re: [PATCH net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change

[Narcisa Vasile]

On Wed, Oct 07, 2026 at 09:47:31AM +0800, Haishuang Yan wrote:
> On slow machines, do_test() raises initcwnd on the route into the tunnel
> with "ip route change". For IPv6 traffic this fails with:
> 
>   RTNETLINK answers: No such file or directory
> 
> The IPv6 prefix route of the tunnel address has metric 256, while
> "ip -6 route change" without a metric looks for a route with the default
> metric 1024, so nothing is changed. The test still passes, but without
> the larger initcwnd it is meant to use.
> 
> Pass the metric of the prefix route.
> 
> Fixes: 1d62b83fb751 ("selftests: net: Fix slow configurations in big_tcp_tunnels.sh")
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
> ---
>  tools/testing/selftests/net/big_tcp_tunnels.sh | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Narcisa Vasile <narcisav.kernel@gmail.com>

Re: [PATCH net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed,  7 Oct 2026 09:47:31 +0800 you wrote:
> On slow machines, do_test() raises initcwnd on the route into the tunnel
> with "ip route change". For IPv6 traffic this fails with:
> 
>   RTNETLINK answers: No such file or directory
> 
> The IPv6 prefix route of the tunnel address has metric 256, while
> "ip -6 route change" without a metric looks for a route with the default
> metric 1024, so nothing is changed. The test still passes, but without
> the larger initcwnd it is meant to use.
> 
> [...]

Here is the summary with links:
  - [net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change
    https://git.kernel.org/netdev/net-next/c/4077df74d716

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net] selftests: net: big_tcp_tunnels: Fix the IPv6 route change

[Alice Mikityanska]

On Wed, Oct 7, 2026, at 04:47, Haishuang Yan wrote:
> On slow machines, do_test() raises initcwnd on the route into the tunnel
> with "ip route change". For IPv6 traffic this fails with:
>
>   RTNETLINK answers: No such file or directory

Thanks for the fix! It's already merged, but anyway:

Tested-by: Alice Mikityanska <alice.kernel@fastmail.im>

> The IPv6 prefix route of the tunnel address has metric 256, while
> "ip -6 route change" without a metric looks for a route with the default
> metric 1024, so nothing is changed. The test still passes, but without
> the larger initcwnd it is meant to use.
>
> Pass the metric of the prefix route.
>
> Fixes: 1d62b83fb751 ("selftests: net: Fix slow configurations in 
> big_tcp_tunnels.sh")
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
> ---
>  tools/testing/selftests/net/big_tcp_tunnels.sh | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/net/big_tcp_tunnels.sh 
> b/tools/testing/selftests/net/big_tcp_tunnels.sh
> index cc0875e52fb9..fb43fed824e3 100755
> --- a/tools/testing/selftests/net/big_tcp_tunnels.sh
> +++ b/tools/testing/selftests/net/big_tcp_tunnels.sh
> @@ -145,7 +145,8 @@ do_test() {
>  			    route change 192.168.2.0/24 dev tun0 initcwnd 100
>  		else
>  			ip -netns "$CLIENT_NS" -6 \
> -			    route change 2001:db8::2:0/112 dev tun0 initcwnd 100
> +			    route change 2001:db8::2:0/112 dev tun0 initcwnd 100 \
> +			    metric 256
>  		fi
>  	else
>  		ip netns exec "$CLIENT_NS" \
> -- 
> 2.43.0