[Pkg-xen-devel] Bug#679533: Bug#679533: Traffic forwarding issue between Xen domU/dom0 and ovs

[Hans van Kranenburg]

On 07/10/2012 08:16 PM, Ian Campbell wrote:
> On Fri, 2012-06-29 at 16:06 +0200, Hans van Kranenburg wrote:
>> We're seeing weird behaviour regarding network traffic between a Xen
>> dom0 and domU. I reported this issue yesterday to the
>> openvswitch-discuss mailing list, but it seems this could also be a
>> (regression?) bug in the xen hypervisor or the linux kernel...
>
> Did you get any response from the vswitch folks?

The response from Ben Pfaff (nicira/openvswitch) was like: "I wish I had 
something to suggest, but this seems like a truly bizarre problem."

http://openvswitch.org/pipermail/discuss/2012-July/007544.html

The reason I also reported this at Debian was because of the observation 
that ARP requests did show up at the interface which is connected to the 
domU, while not showing up inside the domU.

I did some 30+ careful live migrations after reporting the bug and none 
of them showed this weird behaviour again... :|

> Did this used to work? You say "(regression?)".

It just 'used to work' in the sense of "I never encountered this 
behaviour before", having done a number of live migrations in the past.

> This seems more likely on first glance to be an issue with the vswitch
> rather than with Xen or the kernel, unless you can reproduce with Linux
> bridging too.

Currently I have no domU's hanging around in this broken state, because 
I had to fix them for the customer. I've been throwing around some 
domU's today, migrating them over a number of dom0's, but the same issue 
does not show up again... :-(

> In fact it is very unlikely to be a hypervisor issue (the
> hypervisor isn't really involved in network traffic).

> However it would still be useful to try the 4.1 hypervisor and 3.2
> kernel from Wheezy if you can.

...the first thing to do would be to reproduce this using the exact 
software/hardware situation it originated in, and that seems to be quite 
a challenge already...

Anyway, somebody who has the same issue might stumble upon this bug report.

-- 
Hans van Kranenburg - System / Network Engineer
+31 (0)10 2760434 | hans.van.kranenburg at mendix.com | www.mendix.com