netdev - Re: [PATCH] net: Add ndo_gso

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Date:	Tue, 7 Oct 2014 10:18:25 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	Tom Herbert <therbert@...gle.com>, Jesse Gross <jesse@...ira.com>,
	"gerlitz.or@...il.com" <gerlitz.or@...il.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Thomas Graf <tgraf@...g.ch>,
	Pravin Shelar <pshelar@...ira.com>,
	Andy Zhou <azhou@...ira.com>
Subject: Re: [PATCH] net: Add ndo_gso_check

On Tue, Oct 7, 2014 at 10:05 AM, David Miller <davem@...emloft.net> wrote:
> From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Date: Tue, 7 Oct 2014 09:50:50 -0700
>
>> CHECKSUM_COMPLETE is a burden on software.
>
> I totally disagree, it's the most software friendly checksumming
> offload mechanism possible.  I wish every card did it.
>
> CHECKSUM_COMPLETE means that any sub-protocol or tunneling mechanism
> can be trivially supported without any modifications to hardware, and
> it therefore makes checksum offloading of new protocols require no
> hardware changes whatsoever.

yes, of course. My point is that if HW can parse the packet and validate
csum it should do that, since it's faster for the stack on top.
HW can fall back to CHECKSUM_COMPLETE if it fails to parse, for example.
I think some NICs do exactly that.
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