Hello everyone,
I need some help to further debug a mobile broadband modem connection problem.
We are using a mikroe LTE IoT Click board [1] with an u-blox SARA-R410M-02B
cellular modem (LTE-M, NB-IoT) to connect some custom embedded ARM SoC based
hardware to the internet. The LTE module is connected through the serial UART
only.
The current software stack is running on a custom ptxdist based board support
package (BSP) with Linux kernel 4.9.201, ModemManager 1.16.6, NetworkManager
1.30.4, and pppd 2.4.9. I have full control over the software, and can apply
and test patches if needed.
Provider is Deutsche Telekom (DT), we are using some special SIM cards in some
so called Business Smart Connect plan.
The symptoms we face are like this: after reboot of the whole system,
NetworkManager successfully connects. We see that both in Linux, there's a
ppp0 device with the correct IPv4 address, route setup looks fine, resolv.conf
looks fine, `mmcli -m 0` shows the modem is connected, `journalctl -u
ModemManager` looks fine and so does `journalctl -u NetworkManager`. We can
see the modem is connected in the dashboard provided by DT [2].
However we can't receive any data. :-/
After roughly 10 minutes (some random time between 9 and 11 minutes) we get a
disconnect (LCP terminated by peer), and this happens always, every time.
Sometimes after automatic reconnect, we can send/receive data then, but
reconnect is not always successful. :-/
See nm journal output of such a disconnect:
Feb 01 00:10:17 unit pppd[230]: LCP terminated by peer
Feb 01 00:10:17 unit pppd[230]: nm-ppp-plugin: status 8 / phase
'network'
Feb 01 00:10:17 unit NetworkManager[230]: LCP terminated by peer
Feb 01 00:10:17 unit pppd[230]: Connect time 9.8 minutes.
Feb 01 00:10:17 unit pppd[230]: nm-ppp-plugin: status 5 / phase
'establish'
Feb 01 00:10:17 unit NetworkManager[230]: Connect time 9.8 minutes.
Feb 01 00:10:17 unit NetworkManager[230]: Sent 22602 bytes, received 0
bytes.
Feb 01 00:10:17 unit pppd[230]: Sent 22602 bytes, received 0 bytes.
Feb 01 00:10:17 unit NetworkManager[130]: <info> [1612138217.8665]
device
(ppp0): state change: disconnected -> unmanaged (reason 'connection-assumed',
sys-iface-state: 'external')
Feb 01 00:10:20 unit pppd[230]: nm-ppp-plugin: status 11 / phase
'disconnect'
Feb 01 00:10:20 unit NetworkManager[230]: Connection terminated.
Feb 01 00:10:20 unit pppd[230]: Connection terminated.
Feb 01 00:10:21 unit pppd[230]: Modem hangup
Feb 01 00:10:21 unit pppd[230]: nm-ppp-plugin: status 1 / phase 'dead'
Feb 01 00:10:21 unit NetworkManager[230]: Modem hangup
Feb 01 00:10:21 unit NetworkManager[130]: <info> [1612138221.8974]
device
(ttymxc4): state change: activated -> failed (reason 'ip-config-unavailable',
sys-iface-state: 'managed')
Feb 01 00:10:21 unit pppd[230]: Exit.
Feb 01 00:10:21 unit pppd[230]: nm-ppp-plugin: cleaning up
Feb 01 00:10:21 unit NetworkManager[130]: <error> [1612138221.9571]
kill
child process 'pppd' (230): failed due to unexpected return value -1 by
waitpid (No child processes, 10) after sending SIGTERM (15)
I'm currently struggling to debug the whole thing. I see at least 4 components
interacting (kernel, mm, nm, pppd), and I'm not sure where to start debugging,
but I think nm is worth a try.
I get logs as shown above, however I could not get NetworkManager to increase
log level. I tried to set it in /etc/NetworkManager/NetworkManager.conf like
this:
root@unit:~ cat /etc/NetworkManager/NetworkManager.conf
[main]
plugins=ifupdown,keyfile
rc-manager=file
[ifupdown]
managed=false
[logging]
domains="MB:DEBUG,PPP:DEBUG"
The connection itself is defined like this:
root@unit:~ cat /etc/NetworkManager/system-connections/gsm-ttymxc4
[connection]
id=gsm-ttymxc4
type=gsm
interface-name=ttymxc4
permissions=
autoconnect=yes
autoconnect-retries=0
[gsm]
apn=iot.telekom.net
[ipv4]
dns-search=
method=auto
[ipv6]
addr-gen-mode=stable-privacy
dns-search=
method=auto
I'm a little puzzled about that log message:
Feb 01 00:59:34 unit NetworkManager[342]: <warn> [1612141174.8636]
config:
invalid logging configuration: Unknown log level 'DEBUG"'
Can certain log levels set deactivated by meson options on build?
Maybe someone has some hints how to dig in deeper?
Greets
Alex
[1] https://www.mikroe.com/lte-iot-click
[2] https://business-portal-smart-connect.telekom.de/
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