fibocom: Minimum PDP context ID

[Sven Schwermer]

> The CID=2 context was created because we're now explicitly requesting
> a specific APN in settings. I think that should be fine.
> 
>> +CGCONTRDP:
>> 1,5,"internet.gma.iot","10.80.129.7",,"193.181.245.57","193.181.245.58"
>> +GTRNDIS: 1,2,"10.80.129.7","193.181.245.57","193.181.245.58"
>> +CGACT: 1,1
>> +CGACT: 2,0
> 
> So CID=2 is not being used at all because the runtime state already
> matches the settings we were requesting. So this is like, we create
> some specific bearer settings to use in CID=2 but the modem decides to
> reuse the already connected CID=1 that had the same runtime settings.
> We should handle this somehow definitely.

Yes, I believe this is what happens. Note, however, that +GTRNDIS? 
expectedly reports CID=2

>> However, when configuring different APN for initial and ECM bearer, this
>> is the behavior after the +GTRNDIS connection:
>>
>> +CGDCONT: 1,"IP","gemalto.ericsson.iot","10.118.26.77",0,0,0
>> +CGDCONT: 2,"IP","internet.gma.iot","10.80.196.82",0,0,0
>> +CGCONTRDP:
>> 1,5,"gemalto.ericsson.iot","10.118.26.77",,"193.181.245.57","193.181.245.58"
>> +CGCONTRDP:
>> 2,6,"internet.gma.iot","10.80.196.82",,"193.181.245.57","193.181.245.58"
>> +GTRNDIS: 1,2,"10.80.196.82","193.181.245.57","193.181.245.58"
>> +CGACT: 1,1
>> +CGACT: 2,1
>>
> 
> All this above is expected, right? I don't see any issue with that.

Agreed. This is what I expected.

> Once the connection attempt has succeeded, we should run an explicit
> +CGCONTRDP to look for which CID is the one that got really connected
> matching the APN we requested, and if the CID is different to the one
> that we thought would be, then internally change the CID value so that
> the connection checks can go on normally with the correct CID,
> something like that? What do you think?

That would work I think. Do you then suggest to continue using +CGACT? 
for the connectivity check or switch to +GTRNDIS?

>> When hacking the initial EPS bearer setup into a connection manager
>> (e.g. NetworkManager), should this be done before or after enabling the
>> modem device?

I looked into this some more. It seems like it's not possible to set the 
initial EPS settings if the modem is disabled.

> Looks like that would be mixed in the Cinterion plugin? Or maybe the
> Cinterion modules behave in a different way?
> Giacinto, what do you think?

Looks like it's mixed up in the cinterion plugin.

Best regards,
Sven