Re: [PATCH net v1 2/2] selftests: fib_nexthops: test stale has_v4 on nexthop replace

David Ahern
2026-04-13T14:47:47Z

On 4/13/26 5:45 AM, Jiayuan Chen wrote:
> Add test cases that exercise the scenario where an IPv6 nexthop is
> replaced with an IPv4 nexthop while being part of a group. The group's
> has_v4 flag must be updated so that subsequent IPv6 route additions are
> properly rejected.
>
> Two cases are covered:
> 1. Gateway nexthop replaced across families with an existing IPv6
> route on the group (rejected by fib6_check_nh_list).
> 2. Blackhole nexthop replaced across families with no existing IPv6
> route on the group (fib6_check_nh_list returns early) — this is
> the path that triggers a NULL ptr deref without the kernel fix.
>
> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
> ---
> tools/testing/selftests/net/fib_nexthops.sh | 22 +++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>

Reviewed-by: David Ahern <dsahern@kernel.org>