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Absolute OpenBSD, 2nd Edition by Michael W. Lucas

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PF Components

Before we dive into PF, let’s look at the basic components of packet filtering on OpenBSD. In addition to the pf(4) kernel module, we’ll look at the packet filter control program and the configuration file /etc/pf.conf. Knowledge of interface groups also helps.

Packet Filter Control and Configuration

Use the packet filter control program pfctl(8) to manage, configure, and extract information from PF. You can see the current packet filter rules and settings, connections being processed, the state of the TCP/IP transactions, debugging information, and all kinds of other details. You can also parse rules files and install them in the actual packet filter.

You’ll see many different options for pfctl, addressing every aspect of ...

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