Aleksander Morgado authored Aug 06, 2014 and Dan Williams committed Jan 21, 2015

ModemManager needs to have CLOCAL set in the TTY termios configuration, in order
to notify the kernel that modem control lines are not in effect (e.g. so that a
transition to LOW in the DCD input control line doesn't trigger a hangup in the
TTY).

pppd in the other hand, needs CLOCAL unset in order to have proper modem control
lines in effect during the PPP session. So, when pppd starts it will store the
original termios settings, and before exiting it will restore the original
settings in the TTY. In other words, if CLOCAL was set before launching pppd,
CLOCAL will be also set after pppd exits.

Now, in order for this sequence to work correctly, NetworkManager also needs to
make sure that ModemManager is notified about the disconnection only after pppd
has really finished re-configuring the TTY.

https://bugzilla.gnome.org/show_bug.cgi?id=734347

----------------------

Once the patch is applied, we will be making sure that ModemManager is only
notified about the disconnection AFTER pppd has fully exited:
    NetworkManager[27589]: <info>  (ttyUSB2): device state change: activated -> deactivating (reason 'user-requested') [100 110 39]
    Terminating on signal 15
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 10 / phase 'terminate'
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 8 / phase 'network'
    Connect time 0.3 minutes.
    Sent 56 bytes, received 0 bytes.
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 5 / phase 'establish'
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 11 / phase 'disconnect'
    Connection terminated.
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 1 / phase 'dead'
    nm-pppd-plugin-Message: nm-ppp-plugin: (nm_exit_notify): cleaning up
    NetworkManager[27589]: <warn>  pppd pid 27617 exited with error: pppd received a signal
    NetworkManager[27589]: <info>  (ttyUSB2): modem state changed, 'connected' --> 'disconnecting' (reason: user-requested)
    NetworkManager[27589]: <info>  (ttyUSB2): modem state changed, 'disconnecting' --> 'registered' (reason: user-requested)
    NetworkManager[27589]: <info>  (ttyUSB2) modem deactivation finished
    NetworkManager[27589]: <info>  (ttyUSB2): device state change: deactivating -> disconnected (reason 'user-requested') [110 30 39]
    NetworkManager[27589]: <info>  (ttyUSB2): deactivating device (reason 'user-requested') [39]