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====== NSTX - IP Over DNS Tunneling ======

Using ''nstx'', you can (mis-)use the mostly free DNS resolution 
of many commercial Hotspots to gather internet for free.

===== NSTXD Configuration =====

To run a NSTX service, you need:
  * to own a domain
  * to have control over the authoritative nameserver
  * another host (or at least IP) to serve ''nstx'' via it's port 53

==== Create A Simple Subdomain ====

Create a dedicated subdomain of your domain using a Glue-Record, e.g.:
  $ORIGIN nstx.example.com.
  @           IN  NS      ns
  ns          IN  A       1.2.3.4
where ''1.2.3.4'' is the IP ''nstxd'' is listening on.

==== Install and Configure NSTXD ====

Make sure the kernel of the system you want to run ''nstxd'' at provides tun/tap support.

After installing ''nstx'', the daemon has to be run like so:
  nstxd -i <IP> <DOMAIN>
where ''<IP>'' in this case is ''1.2.3.4'' and ''<DOMAIN>'' is ''nstx.example.com''.

The running daemon creates a device named ''tun0'' which has to be configured appropriately.
Further steps of configuration may have to be done to allow routing between tunnel and
internet.

===== NSTXCD Configuration =====

The NSTX Client Daemon is the client-side counterpart to ''nstxd'' and therefore has to be
run on the Hotspot client.

Consider the situation where you have local network access, including DNS. Having a kernel with
support for the tun/tap device, all you need to do is run ''nstxcd'' with the correct options:
  nstxcd <DOMAIN> <IP>
where ''<DOMAIN>'' in this case is ''nstx.example.com'' and ''<IP>'' the IP of the local nameserver.

The created ''tun0'' device has to be configured accordingly. For full internet access, a default
route via the tunnel endpoints IP has to be used.

===== Caveats =====

  * Setting a tunnel MTU of 500 may prevent connectivity problems, especially when using SSH.
  * When the local nameserver is reachable via routing only, setting the new default route is problematic. In this case a host route is necessary to prevent routing DNS requests via the tunnel.

===== Further Information =====
[[http://thomer.com/howtos/nstx.html|NSTX Howto]]