I am trying build a VPN client mobile for Android based applications that connect to virtual infrastructure over VPN tunnel. I have a similar application for Linux/Windows and I know how to open a tun/tap device (open /dev/net/tun). How do we do the same for Android using C ?
Also what does the class VpnService in the android.net API do exactly ?
The VpnService class does exactly what you need. It provides an access to the tun device. You cannot directly open /dev/net/tun without having root rights. See the ToyVPN example project or an open source VPN project like OpenVPN for Android.