Want to have easy config for network:

 Start/stop GPRS, and set AP name
 Start/stop wireless, and set AP name

So:
 Big "GPRS" button toggles on/off
  text entry for AP name

 Big "WLAN" button toggles on/off
   If on and no ESSID chosen, try to fill in box.


AP name is stored in /media/card/gprs


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There are 4 network connections:
 - usb
 - bluetooth
 - wifi
 - GPRS

Each of the first three could be a source or sink of the
default route.  GPRS can only be a source.

usb:
   notebook runs dnsmasq.  On 'power' we attempt to connect
   each creates a low-prio default route through the other

On 'wake' or explicit request we probe for a network:
 - turn in wifi and wpa_supplicant and see if we manage to connect
 - turn on bluetooth and try to connect
 - if neither of those work, allow GPRS??

Once we get a connection on one network we switch the others to
receive:
 - wifi goes ad-hoc as 'internet'
 - bluetooth listens for network

Use cases:

 1/ development.
    USB cable connects freerunner with notebook and sets
    up network.
    No default route needed, but might be useful if route
    goes out through notebook incase it is on a wired network
    or for other reason freerunner cannot see wireless.

 2/ Internet access for freerunner
     use wifi if connection can be made,
      else usb or bluetooth if it has been set up
      else GPRS

 3/ Access point for tethering
    As above but listen on bluetooth and wifi if there aren't
    in use for Internet access.


Notebook always initiates connection whether usb (cable
plug) or bluetooth.  freerunner runs dhcp.
If Internet is available, notebook runs dns server
which freerunner polls for.  If a nameserver is found,
default route is configured.

Accesspoint mode must be explicitly enabled, possibly by ssh request once local
connection set up.  That is just setting ip_forward.

So: on wake up and possibly other times:

 - write '0' to ip_forward
 - wifi: power on, scan for network
         if we find one, set route and resolv.conf
         if not, configure ad-hoc mode

 - bluetooth: enable iscan and listen for connection with pand
 - usb: always have dnsmasq running
     if there is a bluetooth 

On 'request for internet':
  If wifi connected, then OK
  If usb or bluetooth connected, ping dns server.  If found,
    set resolv.conf and OK
  Attempt GPRS

On 'request for access point'
  request internet, enable routing


---------------------------

dnsmasq:
 - listen on usb0 bnep0 and wifi0
 - each is configured with /5 
   192.168.222.{129,161,193}
 - hand out addreses as appropriate

usb:
  configure when power connected
    ?? how to enable default route on notebook?
    Need to restart dnsmasq?
   Maybe on noteboot us a dhclient hook to avoid
    over-riding the default route.