Might be a duplicate of bug #728044. Or is reconnect behaviour expected without autoconnect enabled?

What happens is not that the modem doesn't automatically connect, but also that the network connection disappears in the first place.

The modem's LED stays in red suggesting there isn't any available mobile network in range, till I remove the device from the USB port and reconnect it.

But the most interesting aspect of it is that the device works fine for many hours if I open a terminal and ping a network address every 5 seconds. Perhaps the connection is finished elsewhere if it stays idle, and the modem simply cannot recover from it till reset.

If the modem disappears from NM/MM, automatic reconnect probably won't help. What would be useful here is a debug log from ModemManager (not "modem-manager"):

https://wiki.ubuntu.com/DebuggingModemmanager

and also the output of these steps when it has happened: http://www.chromium.org/chromium-os/how-tos-and-troubleshooting/debugging-3g/modem-debugging-with-mmcli

mm-test.py link at <http://cgit.freedesktop.org/ModemManager/ModemManager/plain/test/mm-test.py> is broken.

From where can I download it?

Created attachment 283052 [details]
modem.log.txt

Created attachment 283053 [details]
nm.log.txt

- "sudo restart network-manager" keeps the modem running correctly.
- "sudo stop network-manager && sudo start network-manager" doesn't.

The modem seems to be:

'Longcheer', VID 0x1C9E PID 0x9605 (usb)

But the log seems to be just statup of Modemmanager. Please reproduce the problem and then upload the logs.

May be due to this already fixed issue:

http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=2b82fd0e1d5a5441b063090d5d07103e93d92e47

To confirm that we would need to see NM and MM logs during a connection attempt.

Created attachment 283124 [details]
network-debug-toolkit.tar.gz

Created attachment 283125 [details]
mmcli.log.txt

Created attachment 283126 [details]
modem-manager.log.txt

Created attachment 283127 [details]
network-manager.log.txt

Trying to capture "modem-manager.log.txt" or "network-manager.log.txt" using the provided scripts makes:

 - The modem to go down, triggering the bug.
 - The network indicator to disappear.
 - Unable to reconnect by software.

The patch provided in <http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=2b82fd0e1d5a5441b063090d5d07103e93d92e47> could fix this issue.

How can I test it?

I'm afraid the modem manager log still does not contain the connection attempt.

You could also try to look in /var/log/syslog for this error message:

"pppd[30575]: Terminating connection due to lack of activity."

Created attachment 283147 [details]
syslog.txt

Since there isn't any "pppd[30575]: Terminating connection due to lack of activity." message, the cause of this bug is different from the one in <http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=2b82fd0e1d5a5441b063090d5d07103e93d92e47>.

Ouch!

Aug 12 01:28:28 Pandita kernel: [ 5156.185769] option1 ttyUSB3: option_instat_callback: error -71
Aug 12 01:28:28 Pandita kernel: [ 5156.208998] usb 2-1.2: USB disconnect, device number 4
Aug 12 01:28:28 Pandita kernel: [ 5156.209369] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
Aug 12 01:28:28 Pandita kernel: [ 5156.209413] option 2-1.2:1.0: device disconnected
Aug 12 01:28:28 Pandita kernel: [ 5156.209743] option1 ttyUSB1: usb_wwan_indat_callback: resubmit read urb failed. (-19)
Aug 12 01:28:28 Pandita kernel: [ 5156.209753] option1 ttyUSB1: usb_wwan_indat_callback: resubmit read urb failed. (-19)
Aug 12 01:28:28 Pandita kernel: [ 5156.209760] option1 ttyUSB1: usb_wwan_indat_callback: resubmit read urb failed. (-19)
Aug 12 01:28:28 Pandita kernel: [ 5156.209767] option1 ttyUSB1: usb_wwan_indat_callback: resubmit read urb failed. (-19)
Aug 12 01:28:28 Pandita kernel: [ 5156.210010] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
Aug 12 01:28:28 Pandita kernel: [ 5156.210038] option 2-1.2:1.1: device disconnected
Aug 12 01:28:28 Pandita kernel: [ 5156.210346] option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
Aug 12 01:28:28 Pandita kernel: [ 5156.210383] option 2-1.2:1.2: device disconnected
Aug 12 01:28:28 Pandita kernel: [ 5156.211368] option1 ttyUSB3: usb_wwan_indat_callback: resubmit read urb failed. (-19)

The modem firmware is actually crashing, and the device disappears from the USB layer all together. I'm afraid we cannot do anything to handle that :/ We could try to avoid commands we send if they are known to crash the device, but it's hard to say what to do here during a connection attempt.

I'd suggest to try to update the firmware of the device to the latest one given by the vendor/operator :/

Thank you ;)