Linux system cannot use the data connection

Wed Jul 27 07:33:44 UTC 2022

Hi Amol,

> MTU from the carrier is 1360 but wwan0 MTU is set to 1500. It must be set
to the MTU received from the carrier.

Thank you for your suggestion! I added the correct MTU value setting.
However, it looks like it's not the cause of this specific problem, after
changing the MTU and resetting the ModemManager, or after changing MTU,
resetting ModemManager and resetting the modem, the issue still persists.

# ifconfig wwan0
wwan0     Link encap:UNSPEC  HWaddr
00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          inet addr:100.65.37.39  P-t-P:100.65.37.39  Mask:255.255.255.240
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1360  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:696 (696.0 B)

# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes

^C
--- 8.8.8.8 ping statistics ---
12 packets transmitted, 0 packets received, 100% packet loss
#

Do you have an idea what this issue can be caused by, or how to recover the
network access on the devices?

Kind regards,
Filip

On Fri, Jul 15, 2022 at 3:30 PM Amol Lad <Amol.Lad at 4rf.com> wrote:

> Also, one thing I noticed in mmcli-all-log.info. It might not be related
> to your problem though.
>
> MTU from the carrier is 1360 but wwan0 MTU is set to 1500. It must be set
> to the MTU received from the carrier.
>
> -----Original Message-----
> From: Amol Lad <Amol.Lad at 4rf.com>
> Sent: Friday, 15 July 2022 6:39 PM
> To: Filip Kubicz <filip.kubicz at tier.app>
> Cc: modemmanager-devel at lists.freedesktop.org; Kamil Sroka <
> kamil.sroka at tier.app>
> Subject: RE: Linux system cannot use the data connection
>
> Please try below (skip dns resolution)
>
> wget
> http://193.63.62.31/sites/default/files/publications/civic_renewal_forms.zip
>
> From: Filip Kubicz <filip.kubicz at tier.app>
> Sent: Friday, 15 July 2022 6:29 PM
> To: Amol Lad <Amol.Lad at 4rf.com>
> Cc: modemmanager-devel at lists.freedesktop.org; Kamil Sroka <
> kamil.sroka at tier.app>
> Subject: Re: Linux system cannot use the data connection
>
> Hi Amol,
>
> # wget http://speedtest.ftp.otenet.gr/files/test10Mb.db
> --1970-01-04 01:06:40--  http://speedtest.ftp.otenet.gr/files/test10Mb.db
> Resolving speedtest.ftp.otenet.gr... failed: Temporary failure in name
> resolution.
> wget: unable to resolve host address 'speedtest.ftp.otenet.gr<
> http://speedtest.ftp.otenet.gr>'
>
> Filip
>
>
> On Fri, Jul 15, 2022 at 2:52 PM Amol Lad <Amol.Lad at 4rf.com<mailto:
> Amol.Lad at 4rf.com>> wrote:
> Please also try downloading a test file as below and see the result. Does
> it download any file at all?
>
> wget http://speedtest.ftp.otenet.gr/files/test10Mb.db
>
>
>
> From: Filip Kubicz <filip.kubicz at tier.app<mailto:filip.kubicz at tier.app>>
> Sent: Friday, 15 July 2022 5:28 PM
> To: Amol Lad <Amol.Lad at 4rf.com<mailto:Amol.Lad at 4rf.com>>
> Cc: modemmanager-devel at lists.freedesktop.org<mailto:
> modemmanager-devel at lists.freedesktop.org>; Kamil Sroka <
> kamil.sroka at tier.app<mailto:kamil.sroka at tier.app>>
> Subject: Re: Linux system cannot use the data connection
>
> Hi Amol, thanks for the answer. I checked that the devices are not hitting
> the SIM data limit.
> Moreover, as I mentioned there is some small RX/TX occurring for the
> device from the operator point of view, but the "ping 8.8.8.8 -I wwan0"
> does not work.
>
> Filip
>
>
> On Fri, Jul 15, 2022 at 1:28 PM Amol Lad <Amol.Lad at 4rf.com<mailto:
> Amol.Lad at 4rf.com>> wrote:
> I generally run into similar situation when my SIM card runs out of money.
> Do you want to try topping-up SIM card and see if ping is successful?
>
> Amol
>
> From: ModemManager-devel <modemmanager-devel-bounces at lists.freedesktop.org
> <mailto:modemmanager-devel-bounces at lists.freedesktop.org>> On Behalf Of
> Filip Kubicz
> Sent: Friday, 15 July 2022 4:14 PM
> To: modemmanager-devel at lists.freedesktop.org<mailto:
> modemmanager-devel at lists.freedesktop.org>
> Cc: Kamil Sroka <kamil.sroka at tier.app<mailto:kamil.sroka at tier.app>>
> Subject: Linux system cannot use the data connection
>
> Hi!
>
> I'm using ModemManager 1.18.6 with Quectel EG21-G modem and Twilio
> SuperSIM.
>
> This setup works ok on multiple devices.
> However, on a few devices, I see following situation:
>
> • Modem registered to operator network (e.g. Vodafone UK)
>
> • Modem reports connected state
>
> • wwan0 interface has IPv4 address
>
> • Network provider sees no issues
>
> • in Network provider console you can see the device exchanges a few
> hundred kB of data every hour
>
> • but ping doesn’t work
>
> • sending data fails
> This looks strange, as if ModemManager was not aware of the data session
> that is setup, or Linux system not being able to use it.
>
> The simplified flow of using the modem:
> - enable modem
> - wait until it auto-registers
> - create a bearer and connect
> - when bearer obtains IP address, configure the network interface
>
> I attached relevant mmcli information from the device (modem, bearer) and
> debug level logs from 2 situations:
> - device stable in connected state (but ping fails)
> - modem reset - sequence of enable, register, connect -> goes into the
> same state where ping does not work.
> I also attached the commands that are used for setting up the network
> interface when a new IP address is obtained.
>
> What should I check, or do you know how to avoid this situation?
>
> Kind regards,
> Filip
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