ipv6 default router Operation not permitted

[Mark Martinec]

Schrodinger wrote:
> What I am confused about is that without ACCEPT_RTADV on re0, FreeBSD
> doesn't perform Neighbour Solicitation for the default gateway but with
> ACCEPT_RTADV it does ..... Why ? This is Neighbour Solicitation and not
> Router Solicitation....
> 
> I understand that FreeBSD doesn't consider the defaulte gateway to be
> "on-link" so it does not perform ND for it but why does it perform ND
> when ACCEPT_RTADV is set on re0 ? "Surely" ACCEPT_RTADV only affects
> Router Advertisements / Solicitations and not ND.
> 
> I have done packet captures and with ACCEPT_RTADV I see the initial
> Neighbour Solicitation and the Neighbour Advertisement to and from my
> default gateway.
> 
> Without ACCEPT_RTADV - FreeBSD simply doesn't try to perform ND for the
> address. This is where I am uncertain if this is expected or not.

That is a good question and I'd be interested in an answer too.

Perhaps FreeBSD is implementing a predecessor to RFC 4861,
i.e. the now obsolete RFC 2461:


RFC 4861, Appendix F: Changes from RFC 2461
 o Removed the on-link assumption in Section 5.2 based on RFC 4943,
   "IPv6 Neighbor Discovery On-Link Assumption Considered Harmful".


RFC 4943, Abstract
   This document describes the historical and background information
   behind the removal of the "on-link assumption" from the conceptual
   host sending algorithm defined in Neighbor Discovery for IP Version 6
   (IPv6).  According to the algorithm as originally described, when a
   host's default router list is empty, the host assumes that all
   destinations are on-link.


Mark