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

[Marcel Holtmann <marcel holtmann org>]

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.

so with CDMA cards you can actually tell them to allow roaming or not?
If so, do you get notifications when it does.

> > 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.

Actually you really can't tell it by just looking at the IMSI. In oFono
we have to do some heavy lifting to get this information out of the SIM
card. And it is the only way to find the home network that actually
issued your SIM card (at least to me knowledge).

Regards

Marcel