netdev - Re: [3.15-rc3] Bisected: xen-netback mangles packets between two guests on a bridge since merge of "TX grant mapping with SKBTX_DEV

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Date:	Fri, 9 May 2014 18:19:08 -0400
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Sander Eikelenboom <linux@...elenboom.it>,
	Zoltan Kiss <zoltan.kiss@...rix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"David S. Miller" <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>, xen-devel@...ts.xen.org
Subject: Re: [3.15-rc3] Bisected: xen-netback mangles packets between two
 guests on a bridge since merge of "TX grant mapping with SKBTX_DEV_ZEROCOPY
 instead of copy" series.

On Fri, May 2, 2014 at 11:35 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2014-05-01 at 17:40 +0200, Sander Eikelenboom wrote:
>
>> Yesterday i tried to get packetdrill (https://code.google.com/p/packetdrill/) to
>> work to see if i could reproduce with one of it's tests, but didn't get the
>> client server stuff working. It seems it has helped with finding and fixing
>> previous kernel networking bugs.
>
> If you use recent net-next kernel, you need a packetdrill patch, Neal
> might submit it shortly on packetdrill repo.
>
> packetdrill currently does not consume the packets sent on the tun
> device, so this triggers the new [1] TCP stack behavior detecting packet
> did not yet leaved the host.
>
> [1] :
> ( http://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=1f3279ae0c13cd742731726b0ed195d5f09b14e4 )

I have submitted the fix to the packetdrill repo. If you "git pull"
the latest packetdrill sources then its "local mode" should work again
for net-next. Sorry if the delay has caused any hassles.

neal
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