netdev - Re: LRO/GSO interaction when packets are forwarded

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Message-ID: <20080423103809.GB3994@ff.dom.local>
Date:	Wed, 23 Apr 2008 10:38:10 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Stephen Hemminger <stephen.hemminger@...tta.com>,
	Kieran Mansley <kmansley@...arflare.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org
Subject: Re: LRO/GSO interaction when packets are forwarded

On Wed, Apr 23, 2008 at 11:07:04AM +0100, Ben Hutchings wrote:
> Jarek Poplawski wrote:
> > On Wed, Apr 23, 2008 at 06:00:18AM +0000, Jarek Poplawski wrote:
> > > On 23-04-2008 01:01, Stephen Hemminger wrote:
> > > ...
> > > >>>> First off, no hardware should ever do LRO on non-local packets. If the
> > > >>>> hardware isn't smart enough to do this, I guess the bridge code to have
> > > >>>> an API to turn it off. IP should also turn it off if ip_forwarding
> > > >>>> is enabled on that device.
> > > 
> > > Could you explain this more? (I can't see any obvious reason why
> > > forwarding between local networks should differ here from bridging?)
> >
> > ...and the second question: is only ip_forwarding flag checking right
> > way to disable something destined for local packets?
> 
> "Non-local" here simply means destined for another host.  It doesn't
> matter whether that host is on the same LAN or not.

Thanks for explanation! I'd still like to know why it's wrong, and
why we should turn this off on a device with ip_forwarding enabled
without checking how smart this hardware is?

Regards,
Jarek P.
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