From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: Kernel panic eth2 mirred redirect to ifb0
Date: Mon, 20 Dec 2010 11:41:11 +0100
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Cc: Changli Gao <xiaosuo@gmail.com>,
	=?UTF-8?Q?Pawe=C5=82?= Staszewski <pstaszewski@itcare.pl>,
	"David S. Miller" <davem@davemloft.net>,
	Linux Network Development list <netdev@vger.kernel.org>
To: Jarek Poplawski <jarkao2@gmail.com>
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Le lundi 20 d=C3=A9cembre 2010 =C3=A0 10:32 +0000, Jarek Poplawski a =C3=
=A9crit :
> On Mon, Dec 20, 2010 at 10:21:25AM +0100, Eric Dumazet wrote:
> > Le lundi 20 d=C3=A9cembre 2010 ?? 17:11 +0800, Changli Gao a =C3=A9=
crit :
> > > Yes, you are right. I just wonder where shared skbs are allowed. =
Is
> > > there any rule?
> > >=20
> >=20
> > Shared skbs are allowed for sure (pktgen is a provider of such skbs=
).
>=20
> But pktgen doesn't use common dev_queue_xmit() path. It looks like
> some places checking segmentation call pskb_expand_head() assuming sk=
b
> 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.
>=20

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)