RE: [Xen-devel] bug in vlan offload in dom0 3.0.0 kernel?

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> On Thu, Sep 29, 2011 at 10:33:44AM +1000, James Harper wrote:
> > I've just upgraded some dom0's to 3.0.0 (debian kernel) and now my
> 
> From?

>From 2.6.32 pvops

> > Has anyone else seen this problem? And more importantly, might
vswitch
> > solve some of the above problems?
> 
> So.. just since that is probably the first thing you should have
checked for,
> but did your turn checksumming off?
> 

Yes, even with all offloads turned off this is still broken. Google
tells me that I'm not the only one having this problem and it sounds
like it's the igb driver that is broken wrt the new vlan offload code.
It was a known bug around 2.6.37 and just hasn't been fixed yet.

I've worked around the problem by using openvswitch which works because
it doesn't use vlan offload it handles the trunking internally. I had to
increase the MTU on the eth0 interface to 1504 and had to write a brctl
compatibility script (the 'brctl compatibility layer' in openvswitch
doesn't show internal bridges correctly in the output of show) but other
than that it is now working mostly fine.

The only problem is that the tapN interfaces get added to the bridge on
DomU startup but don't get removed from the database on shutdown. The
reason they don't get removed is that because the PCI device is
unplugged when the PV drivers take over, the shutdown code isn't fired
for that interface. Under brctl it didn't matter because the kernel
handled removing an interface when it went away. That's only cosmetic
though.

James

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