netdev - Re: Kernel panic eth2 mirred redirect to ifb0

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Message-ID: <1292841671.2800.11.camel@edumazet-laptop>
Date:	Mon, 20 Dec 2010 11:41:11 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	Paweł Staszewski <pstaszewski@...are.pl>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Network Development list <netdev@...r.kernel.org>
Subject: Re: Kernel panic eth2 mirred redirect to ifb0

Le lundi 20 décembre 2010 à 10:32 +0000, Jarek Poplawski a écrit :
> On Mon, Dec 20, 2010 at 10:21:25AM +0100, Eric Dumazet wrote:
> > Le lundi 20 décembre 2010 ?? 17:11 +0800, Changli Gao a écrit :
> > > Yes, you are right. I just wonder where shared skbs are allowed. Is
> > > there any rule?
> > > 
> > 
> > Shared skbs are allowed for sure (pktgen is a provider of such skbs).
> 
> But pktgen doesn't use common dev_queue_xmit() path. It looks like
> some places checking segmentation call pskb_expand_head() assuming skb
> isn't shared. Btw, it seems ifb should have GSO features similarly to
> loopback. Anyway, until all this is verified, IMHO we should revert
> Changli's mirred patch in stable.
> 

I thought Changli question was : is a skb given to a device
ndo_start_xmit() handler is allowed to be shared ;)

I believe Changli patch should be reverted, because not doing a
skb_clone() should be known by caller.

To avoid the skb_clone(), we must tell caller what we did, so that
caller dont even try to reuse skb (even freeing it)




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