To use pf, please follow these steps:

1. Add kernel options into your kernel config file and recompile kernel:

device          bpf
options         PFIL_HOOKS
options         RANDOM_IP_ID

2. Please set the following variables in /etc/rc.conf according to your needs:

pf_enable="Yes"
pf_logd="Yes"
pf_conf="%%PREFIX%%/etc/pf.conf"

3. Check %%PREFIX%%/etc/rc.d/pf.sh, it is the startup script for pf!