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RE: [Xen-devel] ip/udp checksum offload from minios guest

To: "Ian Campbell" <Ian.Campbell@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] ip/udp checksum offload from minios guest
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Wed, 30 Mar 2011 21:37:52 +1100
Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Anil Madhavapeddy <anil@xxxxxxxxxx>
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Thread-index: AcvuxazpqcsDj2LDS9KujQSxdMUK+gAAHBFA
Thread-topic: [Xen-devel] ip/udp checksum offload from minios guest
> > Is IPv6 offload (gso and/or checksum) supported at this time?
> For GSO only TCPv4 is supported.
> For checksum only TCPv4 and UDPv4 are supported.
> Extending netback to cover more cases would be relatively trivial, I
> think. e.g. extending checksum_setup and/or netbk_set_skb_gso in
> netback.c, plus doing the opposite same on the guest RX paths.
> I suspect most of the complexity will probably come from the correct
> negotiation of the featureset via xenstore ;-)

Yes. Given the problems I've seen under linux with offload it would be nice to 
have even more granularity than we do now. We'd definitely want to be able to 
turn offload on and off for all combinations of tcp/udp/csum/gso individually 
in case there is a problem somewhere.

The main problem I've seen is that Linux doesn't seem to understand that my 
network card supports offload functions but not in combination with VLAN, so 
only the untagged packets (eg vlan1) can be offloaded. That was back at 2.6.18 
so hopefully the support is better now.

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