Network Security Hacks

Automatic vtund.conf Generator

Generate a vtund.conf on the fly to match changing network conditions.

If you’ve just come from [Hack #78] , then the following script will generate a working vtund.conf for the client side automatically.

If you haven’t read the previous hack (or if you’ve never used VTun), then go back and read it before attempting to grok this bit of Perl. Essentially, it attempts to take the guesswork out of changing the routing table around on the client side by auto-detecting the default gateway and building the vtund.conf accordingly.

To configure the script, take a look at the Configuration section. The first line of $Config contains the addresses, port, and secret that we used in the VTun hack. The second line simply serves as an example of how to add more.

To run the script, either call it as vtundconf home or set $TunnelName to the one you want to default to. Better yet, make symlinks to the script, like this:

# ln -s vtundconf home 
# ln -s vtundconf tunnel2

Then you can generate the appropriate vtund.conf by calling the symlink directly:

# vtundconf home > /usr/local/etc/vtund.conf

You might be wondering why anyone would go to all of the trouble to make a vtund.conf-generating script in the first place. Once you get the settings right, you’ll never have to change them, right?

Well, usually that is the case. But consider the case of a Linux laptop that uses many different networks in the course of the day (say, a DSL line at home, Ethernet at work, and maybe a ...