Re: Does NetworkManager support blocking non-home networks (UMTS/3g)

[Dan Williams <dcbw redhat com>]

On Tue, 2009-11-10 at 09:28 +0100, Marcel Holtmann wrote:
> Hi Dan,
> 
> > > I can't seem to find it in the GUI or in the documentation.
> > > 
> > > Can NetworkManager be configured to only connect to home networks? Say I 
> > > am on Vodafone and get free data usage, but then move to an area with 
> > > poor signal for Vodafone, can I prevent switching to T-Mobile which 
> > > costs me money?
> > > 
> > > If yes, can this be determined automatically, or is this done with a 
> > > string match?
> > 
> > For cards where we actually know the commands for controlling roaming,
> > yes we can do this, otherwise NM will need to send the specific MCC/MNC
> > of your operator to the modem, which has its own problems.  This is
> > definitely going to be fixed in the near future, but there's no facility
> > for doing so now other than entering the MCC/MNC of your operator into
> > teh Network entry in the connection editor.
> 
> what do you mean by this. It makes no sense. Which card can be
> controlled to roam or not via its firmware. Normally this is all host
> stack stuff.

Yeah, seems that's mostly CDMA cards right now.  My bad.

> You get the current MCC/MNC from the network notifications and your home
> network is part of the IMSI. Only trick part with the IMSI is that you
> have to check first if the MNC is two or three digits long. That value
> is stored somewhere in the SIM card.

Does that mean talking directly to the SIM to find out the MNC length?
There's boatloads of networks with 3-digit MNC (americas and India
mostly) so it would completely suck if you couldn't tell just from the
MNC.

Dan