In Ubuntu 12.04 and above there are no iptable rules defined by default. I added the following rule and it works fine:(Update)
iptables -A INPUT -p tcp -j QUEUE -m string --string xyz --algo bm
Now, in fedora 15 and above there are some predefined rules by default. The output of iptables -L is:
Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp -- anywhere anywhere ACCEPT all -- anywhere anywhere REJECT all -- anywhere anywhere reject-with icmp-host-prohibited Chain FORWARD (policy ACCEPT) target prot opt source destination REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Now, when i add my rule to iptables, it doesn't work. To make it work, i have to flush the iptables every time before adding my rule, which is undesirable. So, if somebody could resolve the conflict between above rules and my rule, or if there is an alternate method to make sure such a conflict doesn't arise in any case, i would be deeply thankful.