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 0.0.0.0 up
ifconfig eth1 0.0.0.0 up
ifconfig br0 64.221.148.221 netmask 255.255.255.224 up
route add default gw 64.221.148.220
for file in br0 eth0 eth1
do
echo "1" > /proc/sys/net/ipv4/conf/${file}/proxy_arp
echo "1" > /proc/sys/net/ipv4/conf/${file}/forwarding
done;
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.

Regards,
Vikram.

Try using the libnetfilter_queue library.

Bridge working in layer 2 level, so did you check about ebtables?