netdev - Re: Checksum offload queries

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Date:	Tue, 08 Dec 2015 12:06:54 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ecree@...arflare.com
Cc:	netdev@...r.kernel.org, tom@...bertland.com
Subject: Re: Checksum offload queries

From: Edward Cree <ecree@...arflare.com>
Date: Tue, 8 Dec 2015 14:42:19 +0000

> I'm afraid I still don't see it.

You assume that nothing in the stack mangles the packet and would
benefit from having the 1's complement to work with in order to
assist with checksum adjustments etc.

So we want 1's complement, all the time.

All of the headers get touched anyways as each layer of the stack
demuxes the packet.  Therefore there is _ZERO_ cost to use 1's
complement to validate checksums in input.

It's always superior.
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