RE: [Xen-devel] Checksumming problem in pv_ops dom0 kernel / netback

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

> 
> Yeah, I've seen that. It does not give that much information however.
> 
> More specifically, I've tested with two dom0 pv_ops kernels now, and
since
> it's still
> reproducable on the latest xen/stable platform, I'm guessing it either
has to
> do with vlan'ing or
> the tg3 driver , in combination with netback.
> 
> I was hoping some Xen developers could shed some light on this.
> I already conversed with Jeremy about this, and he pointed me to this
mailing
> list.
> 

This may not be relavant, but I have seen problems with the following
combination:

br0:
 eth0
 <netback devices>

br1:
 eth0.2
 <netback devices>

Some (most?) network hardware cannot provide checksum/large send offload
functions for packets that use vlan tagging, but Linux doesn't quite
understand that and gets confused, so when such a packet comes off of
netback and is sent to eth0.2, the LSO/checksum function should be
performed in software but isn't.

I haven't yet figured out of the problem is that the driver is
incorrectly reporting that offload is supported on the vlan device or if
the rest of Linux isn't taking the appropriate action...

James

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