Message-ID: <49345CCA.1030209@myri.com>
Date: Mon, 01 Dec 2008 16:53:14 -0500
From: Andrew Gallatin <gallatin@myri.com>
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To: David Miller <davem@davemloft.net>
CC: ossthema@de.ibm.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
       tklein@de.ibm.com, raisch@de.ibm.com, jb.billaud@gmail.com,
       hering2@de.ibm.com
Subject: Re: [PATCH] lro: IP fragment checking
References: <4933A74F.3050809@de.ibm.com>	<493423D7.5030203@myri.com> <20081201.131810.158631503.davem@davemloft.net>
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David Miller wrote:
> From: Andrew Gallatin <gallatin@myri.com>
> Date: Mon, 01 Dec 2008 12:50:15 -0500
> 
>> As to whether or not to do it in the drivers/hardware or in the
>> LRO code, I favor doing it in the LRO code just so that it is not
>> missed in some driver.
> 
> Then there is no point in the hardware doing the check, if
> we're going to check it anyways.
> 
> That's part of my point about why this check doesn't belong
> here.

What hardware does an explicit check for fragmentation?
In most cases, aren't we just relying on the hardware checksum
to be wrong on fragmented packets? That works 99.999% of the time,
but the TCP checksum is pretty weak, and it is possible to
have a fragmented packet where the first fragment has the same
checksum as the entire packet.

I'd rather have a fragmentation check at the LRO layer to remove
any ambiguity. But if you still object, I'll at least have to
submit a patch  which adds an explicit check in myri10ge.

Drew
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