PPP connection to a private APN

Discussion:

Etienne Mabille

2013-08-02 15:31:48 UTC

Hi everyone,

I am forced to work with version 1.3 of oFono and I want to setup a ppp
connection on a private APN.
It works well on a public APN but not on the private one. I looked at the
debug trace and it seems like oFono doesn't give the username and password
anywhere in the AT commands.
Is this function possible ? If so, does anyone know when this feature was
added so I can add a patch to my version ?

Best regards,

Etienne

Denis Kenzior

2013-08-02 16:00:19 UTC

Permalink

Hi Etienne,

Post by Etienne Mabille
Hi everyone,
I am forced to work with version 1.3 of oFono and I want to setup a ppp
connection on a private APN.
It works well on a public APN but not on the private one. I looked at
the debug trace and it seems like oFono doesn't give the username and
password anywhere in the AT commands.
Is this function possible ? If so, does anyone know when this feature
was added so I can add a patch to my version ?

Your subject mentions a 'PPP' connection. So I assume you're using a
modem which uses PPP. If so, then the user/password exchange is done
over the PPP link and not AT commands. You will have to debug the PPP
connection in order to understand what fails.

The gatchat library actually has a nice tool that might help. It uses
the oFono internal PPP implementation and can make basic context
activations. See gatchat/gsmdial.c for reference.

The tool also supports PPPdump file output (use --pppdump option to set
a filename). You can then view the detailed transaction log with
wireshark or another protocol analyzer.

Regards,
-Denis

Etienne

2013-08-07 14:10:25 UTC

Permalink

Post by Denis Kenzior
Hi Etienne,

Your subject mentions a 'PPP' connection. So I assume you're using a
modem which uses PPP. If so, then the user/password exchange is done
over the PPP link and not AT commands. You will have to debug the PPP
connection in order to understand what fails.
The gatchat library actually has a nice tool that might help. It uses
the oFono internal PPP implementation and can make basic context
activations. See gatchat/gsmdial.c for reference.
The tool also supports PPPdump file output (use --pppdump option to set
a filename). You can then view the detailed transaction log with
wireshark or another protocol analyzer.
Regards,
-Denis

Hi Denis

Thank you for your help, I managed to obtain a dump of the ppp connection
and I compared it with the ppp debug info from ofono.

The modem negociates with the DCE for the correct DNS and IP addresses. But
the modem receives a "CGEV: NW DEACT X25" message before obtaining the IP
address. I checked the dump with wireshark, there is no exchange of username
and password. Do you know if this is supposed to happen before or after
obtention of the IP address ?

I am also wondering what are the possible causes of a "NW DEACT" ?

I tried with the same computer, sim card, APN, credentials, but another
modem (Option GTM382, does not use the PPP module from ofono) and it
connects fine.

Here is the log from ofono :

ofonod[1911]: drivers/atmodem/network-registration.c:cops_cb() cops_cb:
BOUYGTEL, 208 20 2
ofonod[1911]: src/network.c:current_operator_callback() 0x82ea648, 0x82f0a68
ofonod[1911]: Aux: < \r\n+CIEV: rssi,3\r\n\r\n+CIEV: service,1\r\n\r\n+CIEV:
roam,0\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_gprs_activate_primary() cid 1
ofonod[1911]: Modem: > AT+CGDCONT=1,"IP","alstom-france-locomotive.fr"\r
ofonod[1911]: Modem: < \r\nOK\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_cgdcont_cb() ok 1
ofonod[1911]: Modem: > AT+CGDATA="PPP",1\r
ofonod[1911]: Modem: < \r\nCONNECT\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_cgdata_cb() ok 1
ofonod[1911]: drivers/atmodem/gprs-context.c:setup_ppp()
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 0:INITIAL
ofonod[1911]: PPP: event: 0 (Up), action: 2, new_state: 2 (CLOSED)
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 2:CLOSED
ofonod[1911]: PPP: event: 2 (Open), action: 1026, new_state: 6 (REQSENT)
ofonod[1911]: PPP: lcp: pppcp_initialize_restart_count: current state 2:CLOSED
ofonod[1911]: PPP: lcp: pppcp_send_configure_request: current state 2:CLOSED
ofonod[1911]: PPP: gatchat/gatppp.c:ppp_enter_phase() 1
ofonod[1911]: PPP: lcp: pppcp_process_configure_request: current state 6:REQSENT
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 6:REQSENT
ofonod[1911]: PPP: event: 6 (RCR+), action: 2008, new_state: 8 (ACKSENT)
ofonod[1911]: PPP: lcp: pppcp_send_configure_ack: current state 6:REQSENT
ofonod[1911]: PPP: lcp: pppcp_process_configure_ack: current state 8:ACKSENT
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 8:ACKSENT
ofonod[1911]: PPP: event: 8 (RCA), action: 129, new_state: 9 (OPENED)
ofonod[1911]: PPP: lcp: pppcp_initialize_restart_count: current state 8:ACKSENT
ofonod[1911]: PPP: gatchat/gatppp.c:ppp_enter_phase() 3
ofonod[1911]: PPP: ipcp: pppcp_generate_event: current state 0:INITIAL
ofonod[1911]: PPP: event: 2 (Open), action: 401, new_state: 1 (STARTING)
ofonod[1911]: PPP: ipcp: pppcp_generate_event: current state 1:STARTING
ofonod[1911]: PPP: event: 0 (Up), action: 1026, new_state: 6 (REQSENT)
ofonod[1911]: PPP: ipcp: pppcp_initialize_restart_count: current state
1:STARTING
ofonod[1911]: PPP: ipcp: pppcp_send_configure_request: current state 1:STARTING
ofonod[1911]: PPP: ipcp: pppcp_process_configure_nak: current state 6:REQSENT
ofonod[1911]: PPP: ipcp: pppcp_generate_event: current state 6:REQSENT
ofonod[1911]: PPP: event: 9 (RCN), action: 1026, new_state: 6 (REQSENT)
ofonod[1911]: PPP: ipcp: pppcp_initialize_restart_count: current state 6:REQSENT
ofonod[1911]: PPP: ipcp: pppcp_send_configure_request: current state 6:REQSENT
ofonod[1911]: PPP: ipcp: pppcp_process_configure_nak: current state 6:REQSENT
ofonod[1911]: PPP: ipcp: pppcp_generate_event: current state 6:REQSENT
ofonod[1911]: PPP: event: 9 (RCN), action: 1026, new_state: 6 (REQSENT)
ofonod[1911]: PPP: ipcp: pppcp_initialize_restart_count: current state 6:REQSENT
ofonod[1911]: PPP: ipcp: pppcp_send_configure_request: current state 6:REQSENT
ofonod[1911]: Aux: < \r\n+CGEV: NW DEACT X25, "", 1\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:cgev_notify() cid 1
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 9:OPENED
ofonod[1911]: PPP: event: 3 (Close), action: 8224, new_state: 4 (CLOSING)
ofonod[1911]: PPP: lcp: pppcp_initialize_restart_count: current state 9:OPENED
ofonod[1911]: PPP: lcp: pppcp_send_terminate_request: current state 9:OPENED
ofonod[1911]: PPP: ipcp: pppcp_generate_event: current state 6:REQSENT
ofonod[1911]: PPP: event: 1 (Down), action: 1, new_state: 1 (STARTING)
ofonod[1911]: PPP: gatchat/gatppp.c:ppp_enter_phase() 5
ofonod[1911]: Aux: < \r\n
ofonod[1911]: Aux: < +CGEV: ME DEACT X25, "", 1\r\n
ofonod[1911]: PPP: lcp: pppcp_process_terminate_request: current state 4:CLOSING
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 4:CLOSING
ofonod[1911]: PPP: event: 10 (RTR), action: 10004, new_state: 4 (CLOSING)
ofonod[1911]: PPP: lcp: pppcp_send_terminate_ack: current state 4:CLOSING
ofonod[1911]: PPP: gatchat/gatppp.c:sta_sent()
ofonod[1911]: Aux: < \r\n+CGREG: 0\r\n\r\n+CGEV: NW DETACH\r\n
ofonod[1911]: src/gprs.c:ofono_gprs_status_notify() /telit_0 status 0
ofonod[1911]: src/gprs.c:ofono_gprs_detached_notify() /telit_0
ofonod[1911]: PPP: lcp: pppcp_timeout: current state 4:CLOSING
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 4:CLOSING
ofonod[1911]: PPP: event: 4 (TO+), action: 8004, new_state: 4 (CLOSING)
ofonod[1911]: PPP: lcp: pppcp_send_terminate_request: current state 4:CLOSING
ofonod[1911]: PPP: lcp: pppcp_timeout: current state 4:CLOSING
ofonod[1911]: PPP: lcp: pppcp_generate_event: current state 4:CLOSING
ofonod[1911]: PPP: event: 5 (TO-), action: 802, new_state: 2 (CLOSED)
ofonod[1911]: PPP: lcp: pppcp_this_layer_finished: current state 2:CLOSED
ofonod[1911]: PPP: gatchat/gatppp.c:ppp_enter_phase() 0
ofonod[1911]: PPP: gatchat/gatppp.c:ppp_dead()
ofonod[1911]: drivers/atmodem/gprs-context.c:ppp_disconnect()
ofonod[1911]: src/gprs.c:pri_activate_callback() 0x82f0430
ofonod[1911]: src/gprs.c:pri_activate_callback() Activating context failed
with error: Unknown error type

Regards,

Etienne

Denis Kenzior

2013-08-07 15:41:08 UTC

Permalink

Hi Etienne,

Post by Etienne
Thank you for your help, I managed to obtain a dump of the ppp connection
and I compared it with the ppp debug info from ofono.
The modem negociates with the DCE for the correct DNS and IP addresses. But
the modem receives a "CGEV: NW DEACT X25" message before obtaining the IP
address. I checked the dump with wireshark, there is no exchange of username
and password. Do you know if this is supposed to happen before or after
obtention of the IP address ?

The way this is setup is slightly weird in GSM. The PPP stack runs on
the modem and it is supposed to ask for credential information and
transparently forward it to the network during context activation.

Marcel Holtmann

2013-08-07 16:12:38 UTC

Permalink

Hi Etienne,

Post by Etienne

Post by Denis Kenzior

Post by Etienne Mabille
I am forced to work with version 1.3 of oFono and I want to setup a ppp
connection on a private APN.
It works well on a public APN but not on the private one. I looked at
the debug trace and it seems like oFono doesn't give the username and
password anywhere in the AT commands.
Is this function possible ? If so, does anyone know when this feature
was added so I can add a patch to my version ?

Your subject mentions a 'PPP' connection. So I assume you're using a
modem which uses PPP. If so, then the user/password exchange is done
over the PPP link and not AT commands. You will have to debug the PPP
connection in order to understand what fails.
The gatchat library actually has a nice tool that might help. It uses
the oFono internal PPP implementation and can make basic context
activations. See gatchat/gsmdial.c for reference.
The tool also supports PPPdump file output (use --pppdump option to set
a filename). You can then view the detailed transaction log with
wireshark or another protocol analyzer.

Thank you for your help, I managed to obtain a dump of the ppp connection
and I compared it with the ppp debug info from ofono.
The modem negociates with the DCE for the correct DNS and IP addresses. But
the modem receives a "CGEV: NW DEACT X25" message before obtaining the IP
address. I checked the dump with wireshark, there is no exchange of username
and password. Do you know if this is supposed to happen before or after
obtention of the IP address ?

is your private APN really an X25 network? We would normally expect types of IP, IPV6 or IPV4V6 and not plain X25. Are you asking for X25 network via AT+CGDCONT or does the network turn it into one?

Regards

Marcel

Denis Kenzior

2013-08-07 23:30:49 UTC

Permalink

Hi Marcel,

Post by Marcel Holtmann
is your private APN really an X25 network? We would normally expect types of IP, IPV6 or IPV4V6 and not plain X25. Are you asking for X25 network via AT+CGDCONT or does the network turn it into one?

The CGDCONT is quite clearly using an IP context type. We don't even
support X25 context type btw ;)

ofonod[1911]: Modem: > AT+CGDCONT=1,"IP","...."\r
ofonod[1911]: Modem: < \r\nOK\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_cgdcont_cb() ok 1
ofonod[1911]: Modem: > AT+CGDATA="PPP",1\r
ofonod[1911]: Modem: < \r\nCONNECT\r\n

Regards,
-Denis

Marcel Holtmann

2013-08-08 01:03:59 UTC

Permalink

Hi Denis,

The CGDCONT is quite clearly using an IP context type. We don't even support X25 context type btw ;)
ofonod[1911]: Modem: > AT+CGDCONT=1,"IP","...."\r
ofonod[1911]: Modem: < \r\nOK\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_cgdcont_cb() ok 1
ofonod[1911]: Modem: > AT+CGDATA="PPP",1\r
ofonod[1911]: Modem: < \r\nCONNECT\r\n

maybe SIM Toolkit is turning this into an X25 connection ;)

Or the modem firmware is fully confused and not able to handle this. Time to try this with a different modem. For example an Ericsson MBM or Qualcomm QMI.

Regards

Marcel

Etienne

2013-08-09 09:11:51 UTC

Permalink

Post by Marcel Holtmann
Hi Denis,

Post by Denis Kenzior

Post by Marcel Holtmann
is your private APN really an X25 network? We would normally expect

types of IP, IPV6 or IPV4V6 and not

Post by Marcel Holtmann
plain X25. Are you asking for X25 network via AT+CGDCONT or does the

network turn it into one?

Post by Marcel Holtmann

Post by Denis Kenzior
The CGDCONT is quite clearly using an IP context type. We don't even

support X25 context type btw ;)

Post by Marcel Holtmann

Post by Denis Kenzior
ofonod[1911]: Modem: > AT+CGDCONT=1,"IP","...."\r
ofonod[1911]: Modem: < \r\nOK\r\n
ofonod[1911]: drivers/atmodem/gprs-context.c:at_cgdcont_cb() ok 1
ofonod[1911]: Modem: > AT+CGDATA="PPP",1\r
ofonod[1911]: Modem: < \r\nCONNECT\r\n

maybe SIM Toolkit is turning this into an X25 connection ;)
Or the modem firmware is fully confused and not able to handle this. Time

to try this with a different modem.

Post by Marcel Holtmann
For example an Ericsson MBM or Qualcomm QMI.
Regards
Marcel

Hi all,

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 ?

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)

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

Thank you for your help,
Regards,

Etienne

Etienne

2013-08-09 09:37:19 UTC

Permalink

Post by Etienne
- 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.

Sorry I just noticed a mistake, the command used by network manager is
'ATD*99***<cid>#'
The # is at the end

Etienne

Denis Kenzior

2013-08-09 14:24:36 UTC

Permalink

Hi Etienne,

Post by 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).
- 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.

Post by Etienne
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.

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

No problem.

Regards,
-Denis

Etienne Mabille

2013-08-12 09:19:15 UTC

Permalink

Post by Denis Kenzior

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.

The CGDATA does not work with the Telit modem, whatever the value of
AT#CGAUTH is. In my case, ATD*99 is absolutely necessary. The CGAUTH
command is just there to use CHAP instead of PAP because ofono doesn't
handle it.

Post by Denis Kenzior
Patches are always welcome.

I am trying to do a clean patch in drivers/atmodem/gprs-context.c but for
some reason the field gcd->vendor is equal to 0 so it doesn't match with
OFONO_VENDOR_TELIT.
The two AT commands are the following :

// in at_gprs_activate_primary :

if (gcd->vendor == OFONO_VENDOR_TELIT){
/*
* Set the modem to use CHAP authentication if needed.
* Telit modems use PAP by default which is not supported
* by ofono.
*/
g_at_chat_send(gcd->chat, "AT#GAUTH=2", none_prefix, NULL, NULL, NULL);
}

// in at_cgdcont_cb :
if (gcd->vendor == OFONO_VENDOR_TELIT){
/*
* With Telit AT+CGDATA prevents the DCE from offering
* an authentication protocol, so we use this command in
* case we need to connect to a private APN.
*/

sprintf(buf, "ATD*99***%u#", gcd->active_context);
}

Jesper Larsen

2013-08-12 09:28:11 UTC

Permalink

Post by Etienne Mabille

Post by Denis Kenzior

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.

Post by Denis Kenzior
Patches are always welcome.

I am trying to do a clean patch in drivers/atmodem/gprs-context.c but for
some reason the field gcd->vendor is equal to 0 so it doesn't match with
OFONO_VENDOR_TELIT.

Vendor is set when creating the gprs context in telit_post_sim()
(plugins/tellit.c:561)

gprs = ofono_gprs_create(modem, OFONO_VENDOR_TELIT, "atmodem",
data->chat);
gc = ofono_gprs_context_create(modem, 0, "atmodem", data->modem);

You need to change the second argument from 0 to OFONO_VENDOR_TELIT

Post by Etienne Mabille
if (gcd->vendor == OFONO_VENDOR_TELIT){
/*
* Set the modem to use CHAP authentication if needed.
* Telit modems use PAP by default which is not supported
* by ofono.
*/
g_at_chat_send(gcd->chat, "AT#GAUTH=2", none_prefix, NULL, NULL, NULL);
}
if (gcd->vendor == OFONO_VENDOR_TELIT){
/*
* With Telit AT+CGDATA prevents the DCE from offering
* an authentication protocol, so we use this command in
* case we need to connect to a private APN.
*/
sprintf(buf, "ATD*99***%u#", gcd->active_context);
}
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Etienne

2013-08-12 12:43:02 UTC

Permalink

Hi Jesper,

Perfect, this is all it needed. Thank you.

Etienne