Xen networking problems in -current with xn driver?

[Kevin Oberman]

On Tue, Aug 2, 2016 at 11:12 AM, Julian Elischer <julian at freebsd.org> wrote:

> I upgraded my VPS machine to today's current, and on reboot I couldn't get
> into it by network.
>
> A quick switch to the VNC console showed that it was up but that it
> couldn't get out.
>
>
> The xn interfaces said they were UP but attempts to get out were met with
> "network is down".
>
> if I did 'tcpdump -n -i xn0' (and xn1) hten all was fine again.
>
> tcpdump saw packets, and in fact ipfw saw some packets coming in even
> before that but it was not possible to send.
>
>
> Has anyone seen similar?
>
> some relevant parts of the dmesg output.:
>
> [...]

A bit of a guess, but the obvious thing that I see  is that when you start
tcpdump you are placing the interface in promiscuous mode. Looks like the
"device" fails to properly see packet addressed to it.
--
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683