vtund(8) on Linux
The text a40e04c15ce0, as Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny) shipped it.
VTun(Virtual Tunnel) daemon.
Flags it lists
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-P -
-f -
-i -
-m -
-n -
-p -
-s -
-t