netdev - Re: [PATCH v3] ipv4: Early TCP socket demux.

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Date:	Thu, 21 Jun 2012 00:10:39 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	David Miller <davem@...emloft.net>
cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v3] ipv4: Early TCP socket demux.


	Hello,

On Wed, 20 Jun 2012, David Miller wrote:

> > Date: Wed, 20 Jun 2012 10:00:37 +0300 (EEST)
> > 
> >> 			if (skb->dev != dst->dev)
> >> 				dst = NULL;
> > 
> > That makes the most sense.
> 
> Doesn't work, dst->dev is &net->loopback_dev for these locally
> destined input routes.

	I see, correct.

> We have to instead check rt->rt_iif or similar.

	Yes, rt_iif should be valid for packets with
skb->dst = NULL. It is incorrect only on loopback
traffic diverted to "lo", i.e. when skb->dst != NULL.
But it concerns UDP which is not handled by GRO yet.

	When UDP support for GRO is implemented
dev_gro_receive() should additionally check skb_dst
to ignore local copy of b-m/cast traffic sent via
ip_mc_output -> ip_dev_loopback_xmit because
in this case dst->dev and skb->dst can be eth0
where NETIF_F_GRO can be set.

Regards

--
Julian Anastasov <ja@....bg>
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