Re: [PATCH] ipv6: check per-interface proxy_ndp in forwarding and NA paths

[Adriano Córdova]

It does not hit any of the current selftests, but it would be possible to write
one that would currently not proxy NDPs, I think the following config in the
current code:

net.ipv6.conf.all.forwarding=1
net.ipv6.conf.eth0.proxy_ndp=1     # all.proxy_ndp == 0
ip -6 neigh add proxy 2001:db8::100 dev eth0

makes the initial multicast NS work but the subsequent unicast NS do not.


El dom, 20 sept 2026 a las 3:34, Ido Schimmel (<idosch@xxxxxxxxxx>) escribió:
>
> On Fri, Sep 18, 2026 at 12:14:05PM -0300, Adriano Cordova wrote:
> > proxy_ndp can be enabled per interface, with net.ipv6.conf.all.proxy_ndp
> > as a global default. ndisc_recv_ns() checks both, but ip6_forward() and
> > ndisc_recv_na() check only the global value. With the per-interface proxy
> > ndp set and the global one left at 0, the router answers proxy NS but
> > does not pass NDP messages to the proxied target.
> >
> > Check both values at these two sites, as ndisc_recv_ns() already does.
> >
> > Fixes: fbea49e1e240 ("[IPV6] NDISC: Add proxy_ndp sysctl.")
> > Signed-off-by: Adriano Cordova <adrianox@xxxxxxxxx>
>
> Do you have an actual use case for this? Changing a 20 years old user
> visible behavior for the sole reason of removing a TODO comment is not
> good practice.