reverse tunnel access

i want a workstation inside a corporate network (typically), to initiate a connection to an external *nix server listening on some arbitrary port, which then reverses direction so an operator on the external server can connect to the webmin session on the workstation. The point here is to allow any workstation inside the net to enable the inbound connection without having to manually setup a port-forward on the router.

If there isn’t already a module that manages this (I looked, but didn’t find), and someone can provide the script for the reversing tunnel, I’d be happy to build out a general-purpose module and contribute it.