netdev - Re: [PATCH] pktgen: Clone skb to avoid corruption of skbs in ndo_start

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Message-Id: <20110721.150107.25773992475689131.davem@davemloft.net>
Date:	Thu, 21 Jul 2011 15:01:07 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nhorman@...driver.com
Cc:	eric.dumazet@...il.com, greearb@...delatech.com, jpirko@...hat.com,
	netdev@...r.kernel.org, adobriyan@...il.com,
	robert.olsson@....uu.se
Subject: Re: [PATCH] pktgen: Clone skb to avoid corruption of skbs in
 ndo_start_xmit methods

From: Neil Horman <nhorman@...driver.com>
Date: Wed, 20 Jul 2011 11:18:27 -0400

> On Wed, Jul 20, 2011 at 06:24:15AM +0200, Eric Dumazet wrote:
>> Le mardi 19 juillet 2011 à 22:07 -0400, Neil Horman a écrit :
>> > > 
>> > I think this is a good idea.  It lets pktgen dynamically make the clone/share
>> > decision dynamically and only impacts performance for those systems.
>> > 
>> 
>> Just let pktgen refuse to use clone_skb command for these devices.
>> 
> copy that, This is by no means final, but what do you think of this?  If its
> agreeable to you, Ben, et al. I can add this to my local tree and start auditing
> all the drivers that may need to have the flag set.

I think there is a much simpler solution.

Set a flag in the SKB when pktgen does SKB sharing.

In dev_queue_xmit() (or perhaps, dev_hard_start_xmit()), check the flag
and if it's set then we copy the SKB.

If this works, then we fix the crash and no driver changes are
necessary both now and in the future.
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