netdev - Re: Bad TCP checksum error

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Message-ID: <47221CE4.70103@hp.com>
Date:	Fri, 26 Oct 2007 09:59:16 -0700
From:	Rick Jones <rick.jones2@...com>
To:	Gaurav Aggarwal <grv.aggarwal@...il.com>
Cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-net@...r.kernel.org, linux-kernel@...r.kernel.org,
	davidsen@....com
Subject: Re: Bad TCP checksum error

Checksum Offload on the NIC(s) can complicate things.  First, if you are tracing 
on the sender, the tracepoint is before the NIC has computed the full checksum. 
  IIRC only a partial checksum is passed-down to the NIC when CKO is in use.

So, making certain your trace is from the "wire" or the receiver rather than the 
sender would be a good thing, and trying again with CKO disabled on the 
interface(s) (via ethtool) might be something worth looking at.  Ultimately, 
doing the partial checksum modificiations in a CKO-friendly manner might be a 
good thing.

rick jones
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