Re: PPP connection to a private APN

[Denis Kenzior <denkenz@gmail.com>]

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Hi Etienne,

 >
> So we managed to solve our problem, we found out how to connect to a private
> apn, but we have some questions to clear things up.
>
> We compared the sequence of AT commands sent by ofono and by network manager
> for the same modem (Telit HE910).
> One difference is during the activation of the context :
>
>      - ofono uses the 'AT+CGDATA="PPP",<cid>'
> the driver used by the telit is the atmodem. This command doesn't appear in
> the documentation for the Telit HE910, but it still replied OK. However in
> the dumps from ppp, we saw that the DCE does not ask for any authentication
> protocol. So the modem doesn't send its credentials, and the DCE eventually
> forces a deactivation.
>
>      - network manager used 'ATD*99***#<cid>'
> With this command, the DCE asks for an authentication protocol. The modem
> then sends its credentials and the connection is completed.
>
>
> I am not quite sure why the first command does not work while the second
> does and I am very interested in having an explanation if you have one.
> Should we use another driver than the atmodem ? one that uses the ATD command ?
>

So in theory the ATD*99... variation is a legacy context activation 
command.  It is described in 27.007 Section 10.2.1.1 Request Packet 
Domain service 'D'.  It is supposed to be superseded by AT+CGDATA, but 
many manufacturers have not updated their firmware properly.  oFono 
supports both, you might need to set a quirk if one is preferred over 
the other.

>
> Another topic is the authentication protocol. By default the Telit HE910
> uses PAP which is not handled by ofono.
> I started to implement it in gatchat/ppp_auth.c it is not quite perfect
> because it does not ask to do CHAP before falling back to PAP but if anyone
> is interested i would be glad to share the code.
> We then found out that there is a custom AT command for the Telit HE910 that
> allows you to set the authentication protocol to use : AT#CGAUTH=[0,1, or 2]
> I added it in plugins/telit.c in the post_online function and stopped
> working on PAP. (I am using the telit rework patch provided by Jonas Bonn on
> the 4th of April)

Does this work with CGDATA?  If that is the case it might explain why 
CGDATA does not ask for authentication.  You can enable this command 
inside drivers/atmodem/gprs-context.c with the appropriate OFONO_VENDOR 
handling as well.

Patches are always welcome.

>
> At the moment i just modified the source with these modifications, and it
> works nice.
>

No problem.

Regards,
-Denis