How to create a GRE tunnel on Mac OSX Lion?

Question

i'm trying to find a way to create a GRE Tunnel on osx lion, i'm able to create such tunnels in almost every os, including: openbsd/freebsd, linux and cisco IOS.

I'm very surprised that this subject is not discussed in any related osx threads over knowledge sources, ie. google, forums and QA sites.

I found only a couple questions on forums without answer.

Answer 1

Update: The project at http://code.google.com/p/mac-gre/ has been updated and compiles under 10.8 as of Oct 2012. I just compiled it and installed.

Answer 2

According to Note 8 in http://support.apple.com/kb/TS1629,

8.For Mac OS X Server v10.3 VPN service: PPTP uses the IP-GRE protocol (IP protocol 47).

So, GRE should be implemented in the kernel, but I'm not seeing where you can set up your own tunnel, other than using the built-in PPTP service.