Re: [PATCH net] selftest/net: skip srv6_end_d[t/x][4/6]_*_test.sh if iproute2 too old

[Andrea Mayer <andrea.mayer@uniroma2.it>]

On Fri, 28 Aug 2026 18:04:41 +0200
Alessio Faina <alessio.faina@canonical.com> wrote:

> [snip]
> 

Hi Alessio,

> I tried multiple methods:
> the first approach is yours, but I can see the following error with any iproute2 
> version I'm using (I tried 5.5 to 5.18): when running 
> "ip -netns ${rtdst_name}" command, it always returns 
> 
> RTNETLINK answers: File exists
> 2

EEXIST means that the object is already there, and says nothing about
vrftable. When ip does not know vrftable it refuses the command itself,
with the error you showed earlier: either "to" is duplicate,
or "vrftable" is a garbage.

In a netns created by the check there is nothing to collide with, so EEXIST
does not come from the way I suggested. The full command and output would
settle it.

> I tried the following approach as well,
> 
>  	# set the decap route for decapsulating packets which arrive from
>  	# the rtdst router and destined to the hsdst host.
> -	ip -netns ${rtdst_name} -6 route add ${vpn_sid}/128 table ${LOCALSID_TABLE_ID} \
> -		encap seg6local action End.DT4 vrftable ${tid} dev vrf-${tid}
> +	if ! ip -netns ${rtdst_name} -6 route add ${vpn_sid}/128 table ${LOCALSID_TABLE_ID} \
> +			encap seg6local action End.DT4 vrftable ${tid} dev vrf-${tid} 2>/dev/null; then
> +		echo "SKIP: SRv6 End.DT4 vrftable not supported in iproute2"
> +		cleanup
> +		exit "${ksft_skip}"
> +	fi
> 
> where the test is checked at vrftable creation time, and it would
> cleanup and exit as expected from standard tests.
> 
> But obviously this gets the same RTNETLINK answer as an error.
> 

This is a setup step, not a check. The skip decision is taken while the
topology is being built, because setup_vpn_config() is called several times
inside setup(). The check should run before setup(), once.

The way I suggested runs the route add with vrftable in a throwaway netns,
created and removed by the check itself.
test_encap_lookup_supp_or_ksft_skip() in srv6_encap_lookup_l3vpn_test.sh
has that shape: it creates the netns, adds the device it needs, tries its
route, and on failure cleans up and exits ksft_skip. For the dt4 and dt6
tests that device is a vrf bound to the table passed to vrftable, and the
netns also needs the strict mode.

> Then another approach came to my mind, and it seems to be quite reliable.
> Practically checking if the ip command contains the string "vrftable"
> using the "strings" command, and if not, skip the test.
> 
> Something like this:
> 
> +test_iproute2_vrftable_supp_or_ksft_skip()
> +{
> +	if ! strings $(command -v ip) | grep -q "vrftable"; then
> +		echo "SKIP: SRv6 End.DT4 vrftable not supported in iproute2"
> +		exit "${ksft_skip}"
> +	fi
> +}
> +
> 
> What do you think about it?

I would rather not add a new tool dependency to these two tests. The
route add uses ip, which the test needs anyway.

Ciao,
Andrea