IP sets are a framework inside the Linux kernel, which can be administered by the ipset utility. Depending on the type, an IP set may store IP addresses, networks, (TCP/UDP) port numbers, MAC addresses, interface names or combinations of them in a way, which ensures lightning speed when matching an entry against a set.
If you want to
IP sets was written by Jozsef Kadlecsik and it is
based on ippool by Joakim Axelsson, Patrick Schaaf and Martin