Re: [PATCH] lro: IP fragment checking

Andrew Gallatin
2008-12-01T21:53:46Z

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