6tunnel(1) on Linux
The text 3cfb48a1240d, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye) shipped it.
tunnelling for application that don't speak IPv6
Flags it lists
-
-1 -
-4 -
-6 -
-d -
-f -
-h -
-v