I can confirm that indeed Strongswan is written in OOP C. This is relatively common in software with a modular architecture that is intended to run on embedded

I can confirm that indeed Strongswan is written in OOP C. This is relatively common in software with a modular architecture that is intended to run on embedded systems and whose design dates back from a time when C++ standard library was not really well supported on such systems. This is also useful when performance is highly important and you can't afford the C++ vtable overhead.