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

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 ([off-list ref]) escribió:

On Fri, Sep 18, 2026 at 12:14:05PM -0300, Adriano Cordova wrote:

quoted

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 <redacted>

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.