redirect network traffic from/to tapX to/from ethX

[tnavid]

hi,
i want to redirect ALL network traffics (at least tcp&udp) from any-process(exp: browser,messengers,..)
to other process(proxy-client) . i need to do it by tap device like OPENVPN client.
i searched so many about openvpn but i can't understand how openvpn client redirect traffic from all process and modify(encrypt,..) and then send over physical nic to otherside(openvpn server). is openvpn client hook sockets to redirect (like proxifier tool)? or something else?

also i want to know how redirect traffic from tunX interface to ethX interface in c/c++ WINDOWS.