netdev - Re: [PATCH net-next] net: fix possible wrong checksum generation

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Message-ID: <1359398148.2721.13.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Mon, 28 Jan 2013 18:35:48 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Pravin Shelar <pshelar@...ira.com>,
	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<jesse@...ira.com>
Subject: Re: [PATCH net-next] net: fix possible wrong checksum generation

On Fri, 2013-01-25 at 22:34 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Pravin Shelar mentioned that GSO could potentially generate
> wrong TX checksum if skb has fragments that are overwritten
> by the user between the checksum computation and transmit.
> 
> He suggested to linearize skbs but this extra copy can be
> avoided for normal tcp skbs cooked by tcp_sendmsg().
> 
> This patch introduces a new SKB_GSO_SHARED_FRAG flag, set
> in skb_shinfo(skb)->gso_type if at least one frag can be
> modified by the user.
[...]

Again, this needs a net device feature, doesn't it?  net_gso_ok() should
allow hardware checksum/segmentation offload of such packets, and it
won't if there is this new GSO flag with no corresponding net device
feature.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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