Re: Interactions with ModemManager

[Dan Williams <dcbw redhat com>]

On Mon, 2017-04-10 at 14:40 +0100, Colin Helliwell wrote:
> A couple of things I've noticed in integrating NM with ModemManager:
> 1. It seems that eth0 doesn't come up - i.e. dhcp client not fired
> off - until MM has done it's startup operations on the GSM modem. It
> so happens that my GSM has a long power-on pause, and that is holding
> up the system's eth network start-up too. Not a huge problem as a
> hyper-fast startup isn't needed, but not ideal..

Missed this message...  This may be due to NM's "startup" function,
where it waits for all interfaces that exist at startup to settle
before it tries to do anything with them.  This tries to ensure that
composed devices (eg, bonds, bridges, teams, etc) have all the
components they need at startup.

So yeah, that could prevent things from happening if the GSM modem
takes a long time to power on.  You might be able to work around this
by setting the NM "wwan enabled" property to "off" and then having
scripts or something flip that on later?  A dispatcher script could do
that perhaps.

> 2. Even after the initial 'query' start-up on the GSM, NM seems to
> leave it enabled (as per mmcli -m 0), rather than leaving it disabled
> until called upon (with a nmcli conn up XX)

NM has the 'wwan-enabled' option which controls whether it powers up
modems on start.  If that option is off, NM will leave them in
'disabled' state until the 'nmcli con up XXX'.

Try setting 'nmcli radio wwan off', ensuring the modem is disabled in
MM, then restarting NM.  Does that keep the modem disabled?

Dan