netdev - Re: [PATCH 2/3] virtio: Net header needs gso_hdr

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Message-Id: <200801230906.14585.rusty@rustcorp.com.au>
Date:	Wed, 23 Jan 2008 09:06:14 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 2/3] virtio: Net header needs gso_hdr_len

On Tuesday 22 January 2008 21:36:30 Herbert Xu wrote:
> On Wed, Jan 16, 2008 at 03:19:03PM +1100, Rusty Russell wrote:
> > > > It's far easier to deal with GSO if we don't have to parse the packet
> > > > to figure out the header length.  Add the field to the virtio_net_hdr
> > > > struct (and fix the spaces that somehow crept in there).
> > >
> > > Why do we need this? When receiving GSO packets from an untrusted
> > > source the network stack will fill in the transport header offset
> > > after verifying that the headers are sane.
> >
> > Thanks for clarifying; it simplifies things.
>
> Actually now that I've tried your test program I can see that this
> field exists not because of GSO, but because of SG.  It tells you
> how many bytes you want to put in the skb head as opposed to the
> frag array.

Yes, I took it out after your comments, then realized I needed it and put it 
back.

> So this field is fine with me as long as it is named as such to
> avoid confusion since it really has nothing to do with GSO as you
> also need it for SG with large MTUs.

Hmm, how about just "hdr_len" rather than "gso_hdr_len"?

Thanks,
Rusty.
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