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[Xen-devel] Re: Trouble with TCP between domUs

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: David Edmondson <dme@xxxxxxx>
  • Date: Sat, 09 Dec 2006 09:14:32 +0000
  • Cancel-lock: sha1:58OdrTrIeaAgIwTsabnv1A3c28Q=
  • Delivery-date: Sat, 09 Dec 2006 01:15:04 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

* herbert@xxxxxxxxxxxxxxxxxxx [2006-12-09 01:13:26]
> David Edmondson <dme@xxxxxxx> wrote:
>> The inter-domain protocol has no facility to allow the guest to
>> specify the offset at which the checksum should be placed - how does
>> the peer know where to put it?
> When I extended the netback protocol for TSO the idea was that you
> can also have an extra descriptor for checksum offload that would
> carry the offsets.

But that offset is not present today, suggesting that the peer
receiving the packet must be parsing it to determine where to place
the checksum (though I couldn't find that code in a quick inspection).

If the receiver of the packet is required to parse it we're back at
the problem I originally described.

The GSO feature flags are quite specific about what is supported -
checksum feature flags should be the same.

David Edmondson, Sun Microsystems, http://www.dme.org

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