Toby-L201 connect failure Ubuntu 18.04 Modem Manager 1.10.6 Linux Kernel Version 4.20.7

[Aleksander Morgado]

On Fri, Dec 6, 2019 at 9:11 AM Ulrich Mohr <u.mohr at semex-engcon.com> wrote:
>
> Hi,
>
> I am not sure, but I think that this is a problem with the UBlox modems I was facing before with a TOBY 210.
>
> The problem is that the modem does an automatic registration on the LTE network using its default APN (that it gets from the network, when I understand right). That is what you see (m2m.com.attz.mnc170.mcc310.gprs) as context 4:  (which is the default LTE bearer on TOBY). Unfortunately, that does not match the one your have given manually, so ModemManager tries to build up a connection using the secondary context with the APN settings you have given -- which fails, because the service provider does not allow a secondary connection while the first one is active.
>
> What I am not completely clear about is, under which circumstances you get such a long default APN name (not matching the 'official' ones) from the network.
>

The "long" name you get is when the bearer is already connected to
that APN, so the name includes the MCCMNC of the operator.
ModemManager already does a "loose" matching of the APNs and they
should already match that one in context 4 if available:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/blob/master/src/mm-modem-helpers.c#L1506

As you said, MM should have attempted to use context #4 instead of #1
as #4 was already connected. The problem is that the logic looking for
which context to use stops as soon as it finds a matching one, and in
this case it found #1 before #4. We could extend the logic to "prefer"
an APN that is reported with MCCMNC if there are more than one
matching, and I believe that should work.

> @Aleksander: See https://lists.freedesktop.org/archives/modemmanager-devel/2018-August/006633.html
>
> I heavily change the ublox plugin to work around that -- unfortunately I never found the time to bring it to a deliverable state, and at the moment, I can't even remember what exactly I did. But I can provide the sources if needed....

Yes, please, can you do that?


-- 
Aleksander
https://aleksander.es