The Book of PF(NoStarch,3ed,2014)

OpenBSD's stateful packet filter, PF, is the heart of the OpenBSD firewall and a necessity for any admin working in a BSD environment. With a little effort and this book, you'll gain the insight needed to unlock PF's full potential. This 2nd edition of The Book of PF has been completely updated and revised. Based on Peter N.M. Hansteen's popular PF website and conference tutorials, this no-nonsense guide covers NAT and redirection, wireless networking, spam fighting, failover provisioning, logging, and more.