ModemManager vs NetworkManager (and the overlap of functionality) : Best Practices

[Peter Naulls]

On 3/13/23 08:34, Robert Colvin wrote:

> but this leaves me with more questions than answers (after playing for a while)
> 
> As I understood it, NM was responsible for managing the modem itself, whereas MM would handle tasks like automatically failing over a wireless network to a cellular connection - but would rely on NM to manage the interface to the modem. But in this "simple" task there is some overlap/grey area - for example, a cellular data connection requires things like APNs, where should that fall? it seems it has landed in both NM and MM.

"It's complicated".

I use MM in OpenWrt, and I have a separate script to monitor connections and 
restart the modem when required.  It's not an ideal or tightly integrated 
solution, but it's pretty robust at this time.  There may be other pieces too,
in particular udev rules for invoking usbmodeswitch and such.  In OpenWrt,
ModemManager intergrates with netifd, which a lot like NetworkManager, and there
are scripts that tie them together.

> I have had first hand experience in this, though I assumed it was a Network Manager issue . I made a post to the NM list here https://lists.freedesktop.org/archives/networkmanager/2023-February/000026.html - essentially, I have a modem that is on a serial port; modem manager can see it, but Network Manager is unable to setup a connection with it - the specific error is "failed to connect 'r412m_serial': Connection requested IPv4 but IPv4 is unsupported by the modem." -> given in two months there has been no response, maybe its a modem manager issue?
> 

 From what I can see, this could be a MM issue, or it could be an issue with the 
underlying driver.  In any case, full ModemManager debug is needed here.