netdev - RE: [PATCH net-next v4 5/5] xen-netback: enable IPv6 TCP GSO to the guest

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Date:	Wed, 16 Oct 2013 16:52:22 +0000
From:	Paul Durrant <Paul.Durrant@...rix.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Wei Liu <wei.liu2@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: RE: [PATCH net-next v4 5/5] xen-netback: enable IPv6 TCP GSO to the
 guest

> -----Original Message-----
> From: Ian Campbell
> Sent: 16 October 2013 17:49
> To: Paul Durrant
> Cc: xen-devel@...ts.xen.org; netdev@...r.kernel.org; Wei Liu; David Vrabel
> Subject: Re: [PATCH net-next v4 5/5] xen-netback: enable IPv6 TCP GSO to
> the guest
> 
> On Fri, 2013-10-11 at 16:06 +0100, Paul Durrant wrote:
> > This patch adds code to handle SKB_GSO_TCPV6 skbs and construct
> appropriate
> > extra or prefix segments to pass the large packet to the frontend. New
> > xenstore flags, feature-gso-tcpv6 and feature-gso-tcpv6-prefix, are
> sampled
> > to determine if the frontend is capable of handling such packets.
> 
> IIRC the reason we have feature-gso-tcpv4 and feature-gso-tcpv4-prefix
> is that the former did things in a way which Windows couldn't cope with.
> I assuming that is true for v6 too. But could Linux cope with the prefix
> version too for v6 and reduce the number of options? Or is the
> non-prefix variant actually better, if the guest can manage, for some
> reason?
>

The non-prefix variant actually conveys type information and so will be better for frontends that don't have to re-parse the headers anyway.

  Paul
 
> I suppose in the end its all piggybacking off the v4 code paths so
> supporting both isn't a hardship.
>