Convert ip6_forward() to the new routing KPI.

[melifaro]

Summary

Convert ip6_forward() to the new routing KPI.

This change depends on D24232.

[melifaro]

Update review to account for committed changes.

[ae]

sys/netinet6/ip6_forward.c

206 ↗

(On Diff #70478)

stale comment

242 ↗

(On Diff #70478)

This looks strange, why we don't send ICMP6_DST_UNREACH_BEYONDSCOPE here? Also ifs6_in_discard is not accounted.

[melifaro]

sys/netinet6/ip6_forward.c

242 ↗

(On Diff #70478)

I would prefer to address it in a separate review, as IMO these 2 blocks should be rewritten and simplified.

At this moment we know that src & dst are unicast, hence each can be either link-local or global unicast.
This brings matrix of 4 options: ll-ll, ll-gu, gu-ll and gu-gu.
If gu-gu, no scope checks are needed. For the rest 3, as one or both addresses are link-local, both received and transmitted interface has to be the same.

This can lead to the logic similar to:

if (LL(src) or LL(dst)) {
  if (src_ifp != dst_ifp)
   error
}

instead of the 2 checks above.

Does this sound sane to you?

[melifaro]

Update to reflect ae@ comments.

[ae]

sys/netinet6/ip6_forward.c

242 ↗

(On Diff #70478)

Yes, this sounds correct for me.