openwrt netifd integration improvements with new dispatcher scripts

[Aleksander Morgado]

Hey,

The current openwrt integration suffered from a serious problem:
network initiated disconnections were properly detected by MM but
never reported to netifd. Due to this, the modem may end up in
registered state while netifd thinks it is still connected.

I reported about this issue here: https://github.com/openwrt/openwrt/issues/8368

After discussing the problem with one of the openwrt maintainers, they
suggested a way to report the disconnection of the interface to
netifd. In order to run the operations they suggested, I've added
support for connection status dispatch scripts in ModemManager. These
are scripts that distributions or users could install, equivalent to
what we do with the FCC unlock scripts, and which are run whenever a
bearer gets connected or disconnected.

The work is ready for review/testing here:

https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/775

In that same bugreport I've pushed also the dispatcher script that I
would attempt to integrate in the openwrt packaging once the
dispatcher script support is shipped in a ModemManager release.

Comments and tests welcome!
Cheers

-- 
Aleksander
https://aleksander.es