netdev - Re: Checksum offload queries

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Message-Id: <20151208.120911.1930136653560954435.davem@davemloft.net>
Date:	Tue, 08 Dec 2015 12:09:11 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ecree@...arflare.com
Cc:	tom@...bertland.com, netdev@...r.kernel.org
Subject: Re: Checksum offload queries

From: Edward Cree <ecree@...arflare.com>
Date: Tue, 8 Dec 2015 16:03:18 +0000

> NETIF_F_HW_CSUM is limited to one checksum per packet.

This is false.

As we demux encapsulation layers, we re-adjust the provided 1's
complement sum provided and use that to validate the next layer.

This works for arbitrarily nested encapsulations, and therefore
can support mutliple checksums per packet.

Tom has also created a scheme, called remote checksum offload,
that deals with the corner cases that are actually not able
to be handled fully by NETIF_F_HW_CSUM.
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