svn commit: r364982 - head/sys/netinet6

[Kyle Evans]

On Sun, Aug 30, 2020 at 8:45 PM Kyle Evans <kevans at freebsd.org> wrote:
>
> Author: kevans
> Date: Mon Aug 31 01:45:48 2020
> New Revision: 364982
> URL: https://svnweb.freebsd.org/changeset/base/364982
>
> Log:
>   ipv6: quit dropping packets looping back on p2p interfaces
>
>   To paraphrase the below-referenced PR:
>
>   This logic originated in the KAME project, and was even controversial when
>   it was enabled there by default in 2001. No such equivalent logic exists in
>   the IPv4 stack, and it turns out that this leads to us dropping valid
>   traffic when the "point to point" interface is actually a 1:many tun
>   interface, e.g. with the wireguard userland stack.
>
>   Even in the case of true point-to-point links, this logic only avoids
>   transient looping of packets sent by misconfigured applications or
>   attackers, which can be subverted by proper route configuration rather than
>   hardcoded logic in the kernel to drop packets.
>
>   In the review, melifaro goes on to note that the kernel can't fix it, so it
>   perhaps shouldn't try to be 'smart' about it. Additionally, that TTL will
>   still kick in even with incorrect route configuration.
>
>   PR:           247718
>   Reviewed by:  melifaro, rgrimes
>   MFC after:    1 week
>   Differential Revision:        https://reviews.freebsd.org/D25567
>

I should note that this was:

Submitted by: Mira Ressel <aranea at aixah.de>

It was then put into review form by Lutz Donnerhacke to help guide the
patch into the correct hands.

Apologies for the omission-

Kyle Evans