Re: QMI and LTE: IP connection problems

[Bjørn Mork <bjorn mork no>]

"Martin Anderseck" <Martin Anderseck ni com> writes:

> I'm testing around with a Sierra Wireless MC7710 in QMI mode. For this
> I've checked out, built and installed the current versions of
> ModemManager and NetworkManager a few days ago. First tests with two
> different UMTS networks were successful. Great work, this really works
> out of the box both with QMI and AT commands (Sierra Wireless
> SW/DirectIP mode)!
>
> For further tests I'm using a communication tester for LTE
> signaling. Currently this fails at the simple IPv4 connection. I think
> I can exclude the communication tester as the connection works
> flawlessly using the module with AT commands in the SW/DirectIP mode.

> So what is happening in QMI: The module gets attached and gets an IP
> address with the default bearer. Setting up a connection either using
> the NetworkManager or mmcli --simple-connect works. Binding this IP
> address to wwan0 using dhclient works, too. But while after this
> procedure with AT commands (SW/DirectIP mode) I can ping my APN, use
> services which the communication tester provides and so on, no
> IP-based communication is possible when having set up the connection
> via QMI.
>
> What have I done already: 
> - Checked output of ifconfig wwan0. Differences in the netmask: In AT
> mode the netmask is 255.255.255.0, in QMI it's 255.255.255.252. I
> don't know yet if this could make the important difference as in
> general the UE only needs to connect to its gateway which can be done
> with a rather limiting netmask, too.
> - Changed configuration of wwan0 to the data which works for the AT
> mode - no success.
> - Tried pinging the UE from the communication tester using a built-in
> ping functionality. It got pongs back when the UE was attached but
> stopped as soon as I connected the UE using the NetworkManager or
> mmcli --simple-connect. When I disconnected the pongs re-appeared. I
> cannot explain this to me in any way...
>
> Does anyone of you know what could be the problem in this setup? Can I
> provide you with more information or log files to narrow the down
> problem? Which parts of the ModemManager log is crucial?

So it
- works with DirectIP
- works with QMI and UMTS
- fails with QMI and LTE, except for DHCP
?


This pattern matches the firmware bug worked around by this commit:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/net/usb/qmi_wwan.c?id=6ff509af3869ccac69dcf8905fc75b9a76951594

It has been backported to a number of stable kernels, but as it is
pretty new there are chances you haven't got it yet.  If not, then the
first thing you should try is a kernel with that patch.


Bjørn