RE: Entirely ignoring TCP and UDP checksum in kernel level

[Josan Kadett]

I have found the exact reason why NAT does not work;

- The patched linux box ignores IP checksum errors
- Since now the source address is mofidified without checksumming, NAT also
carries that wrong checksum
- Other boxes does not ignore the checksum and drop packets

I think the solution is here, I have done many different modifications to
get the system redirect packets with wrong checksum. Now all to be done, is
to correct this checksum by changing some code in ip_input.c so that it
recalculates the checksum when the packets seem to arrive from 192.168.1.1. 

Where in the code then?

-----Original Message-----
From: Brad Campbell [mailto:brad@xxxxxxxxxxx] 
Sent: Sunday, August 22, 2004 3:14 PM
To: Josan Kadett
Cc: linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: Entirely ignoring TCP and UDP checksum in kernel level

Are you trying to ping 192.168.77.1 from 192.168.0.30?

Can you give me an iptables -L -n -t nat, ifconfig and route -n from the
patched box and also route 
-n and ifconfig from the dummy client at 192.168.0.30 so I can try and get a
handle on what you are 
doing and how it all is supposed to work?




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