status of tunnel device?

I took a stab at porting some software that uses the BSD tunnel device. What's the status of this device in Mac OS X? Do I need to do anything special to access it? I don't see a /dev/tunX currently -- is there a runtime configuration I can change, or will I have to build a new kernel? Or do I just need to build a KEXT from somewhere? I see that the man page for tun is there... Rob