This is the IP over IP encapsulation daemon.  It is an alternative to the
kernel's native encapsulation support when dealing with more than a few
encapsulation pipes.  It's much easier to update the ipip daemon's routing
table than to have to configure and route a bunch of different interfaces in
the kernel.

The daemon was written by Mike Westerhof, and has been maintained since 1992
by Bdale Garbee.