On 11/5/18 9:02 AM, Ulrich Mohr wrote:
> I am facing this problem, too (see 
> https://lists.freedesktop.org/archives/modemmanager-devel/2018-August/006633.html).
> 
> I addressed that problem by changing the modem manager logic to set the 
> default bearer using the UCGDFLT command whenever a the bearer changes. This 
> seems to work reasonably (with the drawback as described in the thread linked 
> above). I am still testing this, since I am not yet sure that this really 
> does the job.
> 
> 
> @Aleksander, concerning your planned implementation. You wrote in the thread 
> above:
> 
> This should be some API that is totally independent from the connection 
> process I think.
> 
> It is not clear to me how this will work: I don't get any connection not 
> using the UCGDFLT command, so if a bearer is set, this needs to be result 
> somehow in the UCGDFLT command. So how can this be independent from the 
> connection process? If someone sets the APN, e.g. via the Network Manager, 
> the UCGDFLT command must be issued, otherwise it will not work...

Yes, I'm planning to add this as a new API, a new way to be able to manage the 
initial default LTE attach bearer. The user will be able to use this API when 
the module is in low-power mode only (e.g. CFUN=4) and the idea is that it will 
setup the bearer details as we currently do during connection (e.g. APN, user, 
pass...). I'm probably going to suggest that we automatically create a bearer 
object upon boot if the module allows to manage the initial default LTE attach 
bearer settings (e.g. u-blox and MBIM at least).

Upon connection from e.g. NM, MM will check whether the requested settings 
(APN, ip-type...) match the ones from the default LTE attach bearer, and if 
they do, MM will report that the modem is connected right away without trying 
to create and connect a different context. This is already more or less what 
the u-blox plugin does. And when disconnecting the connection, if it was the 
initial default LTE bearer, we'll just report disconnection without touching 
the actual bearer in the modem (as that would probably return an error). This 
procedure is IIRC what Microsoft suggests in the MBIM extensions that allow 
this kind of management, see:
https://docs.microsoft.com/en-us/windows-hardware/drivers/network/mb-lte-attach-operations

-- 
Aleksander
https://aleksander.es
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