I have a proprietary system which transmit a udp video stream from unit #1 (192.168.1.1) to unit #2 (.1.2). I can't make changes to this system, and I'm trying to clone this udp stream so I can access it in a different program. This program will do stuff with the video and send it out again as a multicast stream.
I'm hoping to do this using a Linux machine (running Ubuntu Server 12.04 now) with three network cards. By connecting unit #1 and #2 to two of the network cards (eth0 and eth1) in the Linux machine and using bridge, I've got them communicating. My /etc/network/interfaces looks like:
# The loopback network interface auto lo iface lo inet loopback # The external interface auto eth3 iface eth3 inet static address 192.168.10.2 netmask 255.255.255.0 # The bridge interface auto br0 iface br0 inet manual bridge_ports eth0 eth1
This works, and by using tcpdump I've confirmed that the udp packets are arriving from #1 and are heading towards #2 at port 6000.
The next step I hope will work is to use iptables to clone all udp packets comming from 192.168.1.1 going to port 6000 at #2. I'm not very familiar with iptables, but after reading on line and the manual I thought this would work:
iptables -A PREROUTING -t mangle -p udp -s 192.168.1.1/32 --dport 6000 -j TEE --gateway 192.168.10.2
The rule is applied successfully, but it doesn't work. If I use tcpdump to monitor eth3 I don't see the packets there.
I'd like to grab this stream, work on it and send it out as a multicast on the .10.2 interface.
What am I doing wrong? Is there something I've misunderstood?