No IP address for a successful connection on LTE modem

Garfield Watkins garfield.watkins at
Mon Feb 12 08:49:50 UTC 2024

Sorry, last message was in html format

I have created a plugin for an LTE modem. This modem exposes 1 AT 
command port (e.g. ttyUSB0) and one ethernet port via usb (cdc_ether).

When the modem is inserted via USB, the kernel enumerates some serial 
ports(ttyUSB0 -> ttyUSB7) and a network interface (enp0s20f0u1)

The modem establishes a default bearer on network registration and to 
establish a data network connection I need to create a pdp context 
(AT+CGDCONT) with an APN and thereafter activate it with AT+CGACT=1,1

The modem, which is configured in router mode responds by activating its 
internal dhcp server causing network managers dhcp client to work its 
magic and eventually configure the ethernet port with all the info it 
needs (gateways, dns servers, ip address etc).

This same process is essentially performed by my plugin and yet no IP 
address get assigned to the ethernet adapter exposed by the modem.

Why could this be happening ?

My plugin, specifically the bearer interface implements the folloiwing:

broadband_bearer_class->dial_3gpp = dial_3gpp;
broadband_bearer_class->dial_3gpp_finish = dial_3gpp_finish;
broadband_bearer_class->disconnect_3gpp = disconnect_3gpp;
broadband_bearer_class->disconnect_3gpp_finish = disconnect_3gpp_finish;
broadband_bearer_class->get_ip_config_3gpp = get_ip_config_3gpp;
broadband_bearer_class->get_ip_config_3gpp_finish = 

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