netdev - REDIRECT and UDP in client

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Message-ID: <CA+BD1JGexkpAcJjt73FGRYu+8UUbGeqW-FoFm0dgmyBmgKuViQ@mail.gmail.com>
Date:	Tue, 11 Aug 2015 23:30:27 +0530
From:	Madhan <madhan.mepco@...il.com>
To:	netdev@...r.kernel.org
Subject: REDIRECT and UDP in client

Hi All ,
I am trying to redirect the udp packet to particular port where I run
my proxy (SOCKS) . I am supposed to obtain the original destination
ipaddress of the client to add to the data field of socks message as
per the RFC .

However , when I use REDIRECT chain as it sets the dest addr to the LO
address i get the LO address 127.0.0.1 and the port where socks proxy
client runs .

I tried patching SO_ORIGINAL_DST to obtain for UDP protocol also . In
this case it would work if I use single FD for single dest . However
when I use single FD for multiple connection it might not work .

I cannot add as part of rsvmsg , as I have to send to the proxy server
in advance .

TPROXY works in prerouting , I am not sure how we use in the client
side to send the first packet with the dest address . (I am not sure
about the TPROXYing though)

Can you please suggest the method to overcome the problem . Thanks in advance.

Regards,
Madhan Raj K ,
Senior Software Engineer - Android R&D ,
Samsung Research Institute - Bangalore .
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