Packet Filtering with Tables
A table is a list of IPv4 and/or IPv6 addresses, much like a list. A table is faster than a list, however, and uses less memory. If you have only a few addresses, using a list is fine, but once you have more than a few, use a table.
Interestingly, you can edit tables without reloading the filter rules, and several programs use this feature to dynamically change how a server behaves. Some people load lists of malware-laden computers into a table to block those hosts, or use external programs to generate such lists. (“You’ve tried to send us four invalid emails in a row? Good-bye!”) Tables can be kept permanently in external files, or you can treat them as ephemera. It’s your choice.
You can create ...
Get Absolute OpenBSD, 2nd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.