6tunnel(1) on Linux
The text 42c3dbb8c031, as Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch) shipped it.
tunnelling for application that don't speak IPv6
Flags it lists
-
-1 -
-4 -
-6 -
-d -
-f -
-h -
-v