LE910 connection with custom APN on AT&T SIM
Nate Pleasant
nate.pleasant at accelerated.com
Thu Jan 25 22:35:36 UTC 2018
Bjorn,
Thanks for the insights. I made a bit of progress on isolating the issue. It doesn't seem to be a problem with using a certain PDP context, but more on the Telit modem's activation of said context. I found that if I set the Telit LE910 to 3G-only, it's able to connect just fine. However, if I enable LTE and the modem registers on the LTE network, it does some sort of auto-activation of the first PDP context, which then prevents ModemManager from using the connection. I also switched to using a standard AT&T SIM instead of the customer's SIM just to eliminate the custom APN as an issue. Below are links to output and logs for two different connection attempts: one successful on 3G, the other failing on 4G. Notice the at+cgact output when registered on 4G already had the first context activated, even though ModemManager hasn't initiated a connection with the Telit LE910 yet.
3G successful connection - https://paste.pound-python.org/show/pbKjL4Js3DWRUM9JkTux/
# mmcli -L
Found 1 modems:
/org/freedesktop/ModemManager1/Modem/0 [Telit] MBIM [1BC7:0032]
# mmcli -m 0
/org/freedesktop/ModemManager1/Modem/0 (device id '6e2428cafbad03b44f8a815cd9bd831057a34462')
-------------------------
Hardware | manufacturer: 'Telit'
| model: 'MBIM [1BC7:0032]'
| revision: '20.00.504'
| supported: 'gsm-umts, lte'
| current: 'gsm-umts, lte'
| equipment id: '358148060217853'
-------------------------
System | device: '/sys/devices/platform/soc/soc:internal-regs/d0051000.usb/usb2/2-1'
| drivers: 'cdc_acm, cdc_mbim'
| plugin: 'Telit'
| primary port: 'cdc-wdm0'
| ports: 'ttyACM3 (at), cdc-wdm0 (mbim), wwan0 (net), ttyACM0 (at)'
-------------------------
Numbers | own : '18135463248'
-------------------------
Status | lock: 'none'
| unlock retries: 'sim-pin2 (3)'
| state: 'disabled'
| power state: 'on'
| access tech: 'unknown'
| signal quality: '0' (cached)
-------------------------
Modes | supported: 'allowed: 2g, 3g, 4g; preferred: none'
| current: 'allowed: 2g, 3g, 4g; preferred: none'
-------------------------
Bands | supported: 'unknown'
| current: 'unknown'
-------------------------
IP | supported: 'ipv4, ipv6, ipv4v6'
-------------------------
3GPP | imei: '358148060217853'
| enabled locks: 'fixed-dialing'
| operator id: 'unknown'
| operator name: 'unknown'
| subscription: 'unknown'
| registration: 'unknown'
-------------------------
SIM | path: '/org/freedesktop/ModemManager1/SIM/0'
-------------------------
Bearers | paths: 'none'
# mmcli -m 0 -i 0
SIM '/org/freedesktop/ModemManager1/SIM/0'
-------------------------
Properties | imsi : '310410635065476'
| id : '89014103276350654767'
| operator id : '310410'
| operator name : 'AT&T'
# mmcli -m 0 --command='+cgdcont?'
response: '+CGDCONT: 1,"IP","broadband","",0,0
+CGDCONT: 2,"IP","broadband","",0,0'
# mmcli -m 0 --command='+cgact?'
response: '+CGACT: 1,0
+CGACT: 2,0'
# mmcli -m 0 --command='#sgact?'
response: '#SGACT: 1,0
#SGACT: 2,0'
4G failed connection - https://paste.pound-python.org/show/6p4KRxLDig1tpJm4AU16/
# modem cli
/org/freedesktop/ModemManager1/Modem/0 (device id '6e2428cafbad03b44f8a815cd9bd831057a34462')
-------------------------
Hardware | manufacturer: 'Telit'
| model: 'MBIM [1BC7:0032]'
| revision: '20.00.504'
| supported: 'gsm-umts, lte'
| current: 'gsm-umts, lte'
| equipment id: '358148060217853'
-------------------------
System | device: '/sys/devices/platform/soc/soc:internal-regs/d0051000.usb/usb2/2-1'
| drivers: 'cdc_acm, cdc_mbim'
| plugin: 'Telit'
| primary port: 'cdc-wdm0'
| ports: 'ttyACM3 (at), cdc-wdm0 (mbim), wwan0 (net), ttyACM0 (at)'
-------------------------
Numbers | own : '18135463248'
-------------------------
Status | lock: 'none'
| unlock retries: 'sim-pin2 (3)'
| state: 'disabled'
| power state: 'on'
| access tech: 'unknown'
| signal quality: '0' (cached)
-------------------------
Modes | supported: 'allowed: 2g, 3g, 4g; preferred: none'
| current: 'allowed: 2g, 3g, 4g; preferred: none'
-------------------------
Bands | supported: 'unknown'
| current: 'unknown'
-------------------------
IP | supported: 'ipv4, ipv6, ipv4v6'
-------------------------
3GPP | imei: '358148060217853'
| enabled locks: 'fixed-dialing'
| operator id: 'unknown'
| operator name: 'unknown'
| subscription: 'unknown'
| registration: 'unknown'
-------------------------
SIM | path: '/org/freedesktop/ModemManager1/SIM/0'
-------------------------
Bearers | paths: 'none'
# modem cli -i 0
SIM '/org/freedesktop/ModemManager1/SIM/0'
-------------------------
Properties | imsi : '310410635065476'
| id : '89014103276350654767'
| operator id : '310410'
| operator name : 'AT&T'
# modem at '+cgdcont?'
response: '+CGDCONT: 1,"IP","broadband","",0,0
+CGDCONT: 2,"IP","broadband","",0,0'
# modem at '+ws46?'
response: '+WS46: 31'
# modem at '+cgact?'
response: '+CGACT: 1,1
+CGACT: 2,0'
# modem at '#sgact?'
response: '#SGACT: 1,0
#SGACT: 2,0'
I've reached out to Telit support to see if they have any insight. From what I can tell from Telit's AT command documentation, this auto-activation on 4G seems intentional. Below is a note I pulled from Telit's AT command docs concerning the at#sgact command.
#SGACT - Context Activation
Returns the state of all the contexts that have been defined
#SGACT: <cid1>,<Stat1><CR><LF>
...
#SGACT: <cid5>,<Stat5>
where:
<cidn> - as <cid> before
<statn> - context status
0 - context deactivated
1 - context activated
Note: In LTE network, default PDP context(cid 1) is activated by
piggybacking on LTE attach procedure and maintained until detached from
NW. This command with cid 1 is just binding or unbinding application to the
default PDP context.
Nate Pleasant
________________________________
From: David McCullough
Sent: Thursday, January 25, 2018 8:39:00 AM
To: Bjørn Mork
Cc: Nate Pleasant; modemmanager-devel at lists.freedesktop.org
Subject: Re: LE910 connection with custom APN on AT&T SIM
Hi Bjørn,
Comments below.
Bjørn Mork wrote the following:
> Nate Pleasant <nate.pleasant at accelerated.com> writes:
>
> > I have a Telit LE910 modem that ModemManager doesn't seem to be able
> > to connect with when using an AT&T SIM card with a custom APN. See
> > output and debug messages below for reference. If I connect this same
> > SIM card with a Sierra MC7354 or Sierra MC7455 modem, it's able to
> > connect with ModemManager just fine. Is there something I'm missing
> > when connecting with this Telit LE910 modem?
>
> I hope some Telit experts will chime in if I am wrong but the LE910 is
> based on an Intel chipset, isn't it?
>
> If so, then I think some of the findings wrt the Sierra Wireless EM7345
> are relevant. My memory is foggy at best, but I found this:
> https://lists.freedesktop.org/archives/libmbim-devel/2014-May/000283.html
>
> There were a few surprises (to me at least) there. I don't know how
> much of that has been fixed/changed in newer firmware revisions. But
> some issues to be aware of:
>
> - the modem might bring up a default bearer using some APN you never
> configured, based on the SIM/operator.
We have seen this on Sierra modems as well when the AT+CGDCONT list has
APN's but we are connecting through QMI, sometimes it uses the APN from
the +CGDCONT list.
> - this default bearer can conflict with later attempts to connect other
> APNs using MBIM and the same IP-type. Note that in my case I could
> easily detect this error since I knew the two APNs used different
> address types (global vs rfc1918)
>
> - you might be able to work around the issues by explictly configuring
> contexts before attempting to do an MBIM connect.
We actually do this, we have a wrapper that ensures before we connect that
the AT command versions and the MBIM versions of all contexts match.
It has saved us on more than one modem.
> My proposal is to play with the AT+CGDCONT list and see if it changes
> the behaviour in any way.
We have learned that the data session is working, we can use the telit
socket commands (at#sd etc) to make a connection to a website and load a web
page, however, no traffic seems to pass through the wwan0 interface.
We can however put another SIM in there and have it work fine. It sure is
confusing.
I would suspect the MBIM driver if it were not for the large number of
working SIM/APN combinations that work. This particular SIM/custom APN is
the first we have had that does not work, yet clearly the data connection
is working on the radio side.
Big thanks for any and all ideas :-),
Cheers,
Davidm
--
David McCullough, david.mccullough at accelerated.com, Ph: 0410 560 763
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