[ale] A tunneling/routing brain teaser....

John Wells jb at sourceillustrated.com
Mon Sep 30 01:17:30 EDT 2002


Alright. here's the problem:

I have classes that meet daily via the web using Windows software.  The
software displays some powerpoint files and streams some video.  Looks
like (so far) everything happens on ports 1730 and 1755 via UDP.  To run
the windows software, I use win4lin.  It's set up on the network with
its own interface, so although my linux box's ip might be 192.168.2.9,
my win4lin ip (on that same machine) might be 192.168.2.10.

My company's firewall blocks most common ports with the exception of
http (80), http-s(443), ssh(22) and a few others, so I'm screwed as far
as class goes.  I'd like to come up with a way to tunnel UDP traffic to
a machine on my home dsl connection, then route via that network to my
school's network, and back.

So, it'd look something like this
 _______________                  __________________
[               ]--------------->[                  ]
[ win4lin iface ]                [ linux host iface ]
[_______________]<---------------[__________________]
                                           ^ 
        ___________________________________|             
       |                                             
 ______V________                  __________________
[               ]--------------->[                  ]
[ home box on   ]                [   classes.ksu    ]
[_____dsl_______]<---------------[__________________] 


One of the problems here is that the home iface is a dynamic address,
but I do have it setup with a dyndns.org dns entry.

Anyway, looking for advice on the best way to set this up.  

I've been playing with vtun but haven't yet been successful.  Every
other option I've come up with thus far feels like it would be held
together with (very frail) scotch tape.  Ideally, a solution would allow
me to have the tunnel established between the linux host iface and the
home box, which would then recognize incoming packets (by src address?)
and forward them to classes.ksu.  This way, I could add classes.ksu to
the win4lin's box hosts file, but point the ip to the linux host iface
instead.  This should cause win4lin to route those packets
appropriately.  I'd also ideally like to have a solution that would 
allow me to tunnel multiple ports via one tunnel, rather than setting up
separate tunnels for each port I need.

Thanks for your time, and for any suggestions you might have!

John




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