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Re: Bad TCP checksum error

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From: Rick Jones <rick.jones2@...>
To: Gaurav Aggarwal <grv.aggarwal@...>
Cc: <netfilter-devel@...>, <netdev@...>, <linux-net@...>, <linux-kernel@...>, <davidsen@...>
Subject: Re: Bad TCP checksum error
Date: Friday, October 26, 2007 - 12:59 pm

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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Messages in current thread:
Bad TCP checksum error, Gaurav Aggarwal, (Fri Oct 26, 3:41 am)
Re: Bad TCP checksum error, Gaurav Aggarwal, (Fri Oct 26, 12:03 pm)
Re: Bad TCP checksum error, Rick Jones, (Fri Oct 26, 12:59 pm)