Shorewall

Shoreline Firewall (Shorewall) Tips
To list the connections from an IP address.

conntrack -L -s 192.168.0.103

To drop all the connections from an IP address.

conntrack -D -s 192.168.1.102

It can take up to 1 minute to drop all of them, so be patient. You can then restart shorewall and be certain any NEW connections (not ESTABLISHED ones) will be accounted for.