Re: mcx(4) and bridge(4)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Apr 11, 2025 at 06:46:23PM +0200, Hauke Fath wrote:
> Hi,
> 
> I am not really sure where to take this, port-xen or tech-net -- picture the
> following setup:
> 
> A netbsd-10 xen Dom0 hangs off a mcx(4) interface, with three vlans (2,3,5)
> hooked onto three bridge(4)s. The vlans are for the sake of the DomUs, the
> Dom0 itself has an ip on vlan2.
> 
> There is right now one PV DomU which is a dump | restore copy of an existing
> netbsd-9 installation from another Dom0. It also has an ip on vlan2 via the
> usual xen procedure; vlans 3 + 5 are currently unused.
> 
> The setup mimics that of two Dom0 machines with different (older) hardware
> and OS.
> 
> The Dom0 has full network access without any issues.
> 
> The DomU can reach the Dom0 and vice versa (ssh login). But nothing it sends
> will leave the Dom0; a tcpdump on vlan2 logs its arp requests for external
> addresses (default gateway, subnet-local nameserver), but never a reply.
> 
> It isn't the switch: I tried connecting the second mcx interface to a
> different switch, no change.
> 
> Using an onboard bge(4) nic instead of the mcx(4), the DomU has fully
> functional network access. That would be fine for now, but the planned use
> of the mmachine will need the mcx(4)'s bandwidth.

I'd say the mcx driver fails to receive packets that are not for
its owm mac address. Maybe an issue with promiscious mode.

What does ifconfig in the dom0 say ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--