I am currently setting up a wireless router using OpenWRT. The landlord of the dorm I live in requires joining a VPN to access the internet, supporting both PPTP and OpenVPN.
I want to support the "freifunk" network, which provides free WiFi all over Germany. As far as I was able to tell, due to the topology of that network and the legal circumstances here, every router connects to other routers using OpenVPN. I was wondering if it is possible to instruct the freifunk OpenVPN instance to use the PPTP VPN network interface ppp0 providing internet access and if it is possible, how to achieve this on openWRT.
Any help, including pointers to related articles would be greatly appreciated since my first searches found only articles telling windows users not to run several VPN clients at once. Since VPN clients in Linux create network interfaces, I could imagine it is possible to "chain" these together.