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

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Message-ID: <4E28A4C8.8040707@candelatech.com>
Date:	Thu, 21 Jul 2011 15:14:32 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	David Miller <davem@...emloft.net>
CC:	nhorman@...driver.com, eric.dumazet@...il.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

On 07/21/2011 03:01 PM, David Miller wrote:
> 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.

Doesn't that make clone-skb in pktgen much less efficient
in all cases?

Thanks,
Ben


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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