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Old 12-21-2009, 11:53 AM   #1
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Intercept UDP packet in transparent bridge mode

Hello All,

I have setup two servers as shown below

|Internet |
|DSL Modem|
| eth0
|Server 1 |
| eth1(Server1)
| eth0(Server2)
|Server 2 |

Server1 : Has eth0 and eth1 bridged, bridge has a Public IP.Runs Kamailio and rtpproxy
Server2 : Configured with a Public IP.Runs Asterisk
The bridge between eth0 and eth1 of Server1 has been setup using the shell script:
brctl addbr br0
brctl stp br0 on
brctl addif br0 eth0
brctl addif br0 eth1
ifdown eth0 1>/dev/null 2>&1
ifdown eth1 1>/dev/null 2>&1
ifconfig eth0 up
ifconfig eth1 up
ifconfig br0 netmask up
route add default gw
for file in br0 eth0 eth1
echo "1" > /proc/sys/net/ipv4/conf/${file}/proxy_arp
echo "1" > /proc/sys/net/ipv4/conf/${file}/forwarding
echo "1" > /proc/sys/net/ipv4/ip_forward
Is it possible to intercept packets on UDP port(port_number) at Server1 destined to Server2 before they arrive at Server2 ? If so, how can this be done ?

Thanks in advance for your help.


Last edited by vragukumar; 12-21-2009 at 11:54 AM.
Old 12-21-2009, 12:33 PM   #2
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Location: South Carolina, U.S.A.
Distribution: Ubuntu, Fedora Core, Red Hat, SUSE, Gentoo, DSL, coLinux, uClinux
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Originally Posted by vragukumar View Post
Is it possible to intercept packets on UDP port(port_number) at Server1 destined to Server2 before they arrive at Server2 ? If so, how can this be done ?
Try using the libnetfilter_queue library.
Old 12-22-2009, 07:36 AM   #3
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Bridge working in layer 2 level, so did you check about ebtables?


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