I've been trying to figure out a complete working solution for IPSec VPN implementation on FreeBSD but with no luck till now. pfSense seems did a fantastic job on supporting IPSec and even for mobile clients, so I downloaded and installed pfSense hoping to figure out how it works, or at least see some configuration examples, but I couldn't find anything interesting maybe because I'm not familiar with pfSense, so I'd like to ask for help.
How pfSense implements IPSec, what tools are used?
Where does pfSense store all its configuration files?
And since pfSense has its own kernel mods and acts as a different OS, there's no way for us to install it on top of an existing FreeBSD box, and plus that it is such a great project combining those fantastic features, so my question can kinda be extended as:
How do we learn from pfSense, and implement its features on top of a regular FreeBSD server?