IPFW and PF are used for more than just firewall and shaper, e.g.
NAT, policy routing or shaping, and the plugin framework supports
registering multiple user-facing services per file.

(cherry picked from commit 3b34f51f)
(cherry picked from commit ff0dcc4d)
(cherry picked from commit 5e1e138f)
(cherry picked from commit c8cb224b)