Re: manage a modem connection

[Édouard Debry <edouard debry gmail com>]

On lun., mars 29 2021, Aleksander Morgado wrote:
> Hey

Thanks for your answeer.


> > I have a "e3372h-153" Huawei 4G USB dongle.
> >
> > This dongle works with the "huawei_cdc_ncm" kernel driver.
> >
> > Once connected,  two devices appear : /dev/ttyUSB0 and
> > /dev/cdc-wdm1.
> > These ones are used to talk to the modem itself.
> >
> > There is also a network interface appearing, which is (I 
> > believe)
> > related to the driver "huawei_cdc_ncm" and the NCM protocol :
> >
> > wwx001e101f0000: flags=4098<BROADCAST,MULTICAST>  mtu 1500
> >         ether 00:1e:10:1f:00:00  txqueuelen 1000  (Ethernet)
> >
> > I am able to connect the modem with "mmcli ...", yet still I 
> > have
> > to configure
> > the corresponding network interface in order to access the
> > web.
>
> When using only ModemManager/mmcli this is expected, yes. You 
> need to
> look for the connected bearer details (e.g. mmcli -b 0 probably) 
> and
> then apply the IP addressing changes showed there.

I cannot find any bearer.

> > But this
> > interface does not show up with "nmcli device show". I am 
> > however
> > able to
> > issue "dhclient wwx001e101f0000" and it works.
>
> NetworkManager does not refer to the modem based on the network
> interface it exposes, it refers to the modem based on the 
> primary
> control port exposed by the modem (e.g. cdc-wdm0 probably).

Ok, I understand, "nmcli -m 0" gives :

 System   |               device: 
 /sys/devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.1/1-1.1.3
          |              drivers: huawei_cdc_ncm, option1
          |               plugin: huawei
          |         primary port: ttyUSB0
          |                ports: cdc-wdm1 (at), ttyUSB0 (at), 
          wwx001e101f0000 (net)

so, there are two control ports and one data port. NetworkManager 
defaults to the primary port :

ttyUSB0: déconnecté
       "Intel Sunrise Point-LP 3.0 xHCI"
       gsm (huawei_cdc_ncm, option1), hw
       

> > I also tried "nm-connection-editor". This one finds the modem
> > (gsm) but it seems to
> > settle a connection through ppp.I would prefer a connection
> > through wwx001e101f0000
> > because it uses the NCM protocol, known to be faster than PPP.
>
> This is the way to go. If ModemManager doesn't use the cdc-wdm 
> port
> plus the network interface for the connection, there must be a 
> reason
> for that, we need to find why.
>
> Do the cdc-wdm and the net port show up in the list of ports 
> reported
> in "mmcli -m 0"?

yes, but I tried again, nm-connection-editor lets me choose 
"Mobile Connection",
but I see settings for PPP.

> > Then, how come that I cannot see and configure wwx001e101f0000
> > with nmcli, just like
> > any other network (wired, wifi) interface ?
>
> Because that interface is a modem network interface, and so the 
> main
> interface that NetworkManager would refer to is the control 
> port, not
> the data port (as the data port is chosen dynamically on 
> runtime).

Ok, I understand.

Maybe this is because NetworkManager sees ttyUSB0 first and then 
thinks
it is a PPP connection. How could I make NetworkManager consider 
only
cdc-wdm1 (in my case) ?

Regards