[Bug 261129] IPv6 default route vanishes with rtadvd/rtsold

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 17 Jun 2022 05:58:27 UTC

--- Comment #17 from Marek Zarychta <zarychtam@plan-b.pwste.edu.pl> ---

A couple of days ago I rewrote the set of slapdash PF rules suspecting them as
the cause, especially initially abused "rtable" statements. The "rtable" had
been replaced with "reply-to" or deleted where possible and it was the right
step. It is worth mentioning that a few rules with "rtable" were preserved
though. When the issue got sorted out, to find the culprit one of the borked
rules used previously was reintroduced:
"pass in quick on gif0 inet6 to ($gif_if) rtable 1"
which led to the corruption of the default route in FIBs 0 and 1 within a few
hours. Maybe this happens due to incorrectly recognised protocol 41? 

Final conclusions:

1. FreeBSD routing stack is capable of using two different IPv6 GUA subnets on
the same interface on both CURRENT and 13-STABLE.

3. The rules with "rtable" statements regarding IPv6 traffic should be
introduced with care in PF(4) configuration file and avoided when possible.

3. IPv6 on FreeBSD still needs more testing, especially in multihomed scenarios
where multiple FIBs are involved.

It is probably my fault, I am sorry for making noise on the frebsd-net@ mailing
list and hijacking this PR, but provided feedback might be useful. If you still
consider this a bug, please let me know, and I will submit a new PR.

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