[atlas] SixXS issues

On Thu, May 5, 2016 at 3:11 PM, Alison Wheeler <ripecontact at markyate.net> wrote:
> ... but the v6 is going up and down every few minutes (for around the same period.)

For many months, one of my Atlas probe (v1/v2, firmware 4730) has been
running quite nicely through a SixXS IPv6 tunnel. But starting two or
three months ago, this probe goes up and down every two to four
minutes. As soon as I block all IPv6 connections to/from the probe, it
is connectivity over IPv4 only (behind a NAT firewall) is stable and
the probe stays up.

In another location, a second Atlas probe (v3, firmware 4730) runs
stable with dual-stack through a IPv6 tunnel from Hurricane Electric,
and with a very similar rule-set on the firewall (pfSense/FreeBSD).

Currently, I am looking potential causes:
 a) My firewall (pf on OpenBSD) rules over-block incoming ICMP6
requests, if Atlas control hosts should now check if the probe has
two-way IPv6 connectivity.
 b) MTU size mismatch somewhere with my SixXS tunnel setup.
 c) Static vs. dynamic configuration of the probes for IPv6.

I will report any progress/findings. Suggestions welcome, thanks!