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Re: Relative Checksum

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Relative Checksum
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: 26 Mar 2003 19:38:24 +0000
Cc: Gilad Benjamini <yaelgilad@myrealbox.com>, linux-mips@linux-mips.org
In-reply-to: <20030326191601.A19939@linux-mips.org>
Organization:
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1048667601.7d003520yaelgilad@myrealbox.com> <20030326191601.A19939@linux-mips.org>
Sender: linux-mips-bounce@linux-mips.org
On Wed, 2003-03-26 at 18:16, Ralf Baechle wrote:
> On Wed, Mar 26, 2003 at 08:33:21AM +0000, Gilad Benjamini wrote:
> 
> > ip_fast_csum provides an asm version for IP checksum.
> > Any available mips-asm implementation out there for 
> > a relative checksum?
> > 
> > i.e. I get a packet, change
> > a field or two, and want to compute just the 
> > change in the checksum.
> 
> I suggest to look at the code for IP masquerading which already does things
> like this when rewriting packets.

Also read the RFC material on the danger of relative checksum updates.
There are a couple of interesting gotcha's with some stacks


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