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In a wireless Ad-Hoc network, I have two computers which communicates in UDP together from 192.168.1.3 to 192.168.1.5

I have a third computer (192.168.1.6) which wants to listen to the packets which are not addressed to it. I can see the packets with tcpdump (which sets the wireless card in promiscuous mode).

To redirect the packets, I am using :

iptables -t nat -I PREROUTING -s 192.168.1.3 -j DNAT --to-destination 192.168.1.5

Is it the only rule I need to use? Why isn't it working? Did I miss other requirements?

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Something looks strange here. In a wireless network, why are you re-transmitting through iptables? The destination is receiving multiple copies of the same packets. If all you are doing is sniffing, you do not need to route. –  schroeder Jun 5 '13 at 17:02
    
I don't want to re-transmitting packets. I would like to catch the packet which are not destinated to computer .5 –  Mathieu Leiv Jun 5 '13 at 17:29
    
But you are 'redirecting' the packets ... What did you intend iptables to do? –  schroeder Jun 5 '13 at 17:37

1 Answer 1

up vote 7 down vote accepted

Why are you using iptables rather than using good old Wireshark which is specifically made for this? Wireshark is a free and open-source packet analyzer and the ideal tool for performing these types of analysis.

EDIT

If you need to reinject the packets I would have a look at scapy in python.

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I am reusing the packets caught by my filter. Is there anyway to reemit Wireshark caught packets ? –  Mathieu Leiv Jun 5 '13 at 15:07
2  
I would have a look at scapy –  Lucas Kauffman Jun 5 '13 at 15:15

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