From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: TCP transmit performance regression
Date: Thu, 05 Jul 2012 16:28:49 +0200
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Cc: Network Development <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>
To: Ming Lei <tom.leiming@gmail.com>
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On Thu, 2012-07-05 at 22:01 +0800, Ming Lei wrote:

> Basically, copy path will be bypassed since hard_header_len
> has included the 'overhead' already.

Unfortunately this is not done correctly.

needed_headroom should be set to SMSC95XX_TX_OVERHEAD_CSUM