I am trying to block DNS requests using an Ubuntu machine. I have created a bridge and the packets are being forwarded as expected. Only when I add iptables rules, it is not taken in account. I tried with no rules, simply setting the policy of each table to DROP and even this doesn't work : the packets are still transmitted without interruption. I should precise that I'm working in an ISP context so, network-wise, the bridge is situated on the WAN side, between the CPE and a telindus. Thanks for the help.
Version of iptables : 1.4.21
# iptables -L -n -v
0 packets in forward and input, 16 in output (Rather synthetic as I'm on my phone)
All policies are in DROP mode.
/proc/sys/net/bridge/bridge-nf-call-iptables = 1
The configuration of the bridge is rather simple :
brctl addbr br0 brctl addif br0 eth0 brctl addif br0 eth1 ifconfig eth0 up ifconfig eth1 up ifconfig br0 up