Re: [PATCH bpf-next] selftests/bpf: Use ping_command() for IPv6 pings in lwt_ip_encap

On Thu, Aug 13, 2026 at 2:36 PM 'Andrii Nakryiko' via Kernel Team
<[email protected]> wrote:
>
> lwt_ip_encap hardcodes the ping6 binary for its IPv6 pings. iputils
> merged ping6 into ping long ago and distros have started dropping the
> compat symlink -- Arch's iputils 20250605 ships only arping, clockdiff,
> ping and tracepath. There, every lwt_ip_encap subtest fails:
>
>   check_ping_ok:FAIL:ip netns exec ns-lwt-ip-encap-1-0101330 ping6 -c 1 \
>     -W1 -I veth1 fb04::1 > /dev/null unexpected error: 256 (errno 2)
>   #217/1   lwt_ip_encap_ipv4/egress:FAIL
>
> The IPv4 subtests fail too, because check_ping_ok() pings both families.
> SYS() runs the command through system(), so a missing binary is
> indistinguishable from an unreachable peer.
>
> network_helpers.c has had ping_command() for exactly this since commit
> 372642ea83ff ("selftests/bpf: Move netcnt test under test_progs"): it
> falls back to "ping -6" when ping6 is not present. lwt_ip_encap.c is the
> last hardcoded ping6 user. Fix that.
>
> Fixes: f5e288943e2c ("selftests/bpf: Move test_lwt_ip_encap to test_progs")
> Signed-off-by: Andrii Nakryiko <[email protected]>

Acked-by: Song Liu <[email protected]>