dhcpcd-discuss

Hi,

I have had trouble with dhcpcd on cellular (QMI) interface when used 
together with ModemManager. This happened on Raspberry Pi using dhcpcd 
version 8.1.2.

Basically what happens is the following:

- QMI based modem is plugged in, the kernel creates the interface (wwan0).
- dhcpcd notices the interface, logs "waiting for carrier" and 
immediately "carrier acquired". Then it proceeds to configure the 
interface (e.g. link IP address), eventually the interface will be in up 
state.
- A bit later, ModemManager attempts to set the raw_ip mode of the 
interface to the correct value, but this fails because the interface is 
already up (blocked by QMI kernel driver).
- When cellular data connection is started later, it will fail to work 
as the kernel has wrong raw_ip mode configured.

Full log of modem hot-plug and some discussion is available here in the 
corresponding MM ticket originally made:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/issues/189

Is it supposed that dhcpcd configures the cellular interface this early, 
or should it wait until wwan0 is actually connected?

BR: - Teijo