Frédéric Danis authored Sep 11, 2018 and Thomas Haller committed Sep 11, 2018

When unplugging an USB 3G modem device, pppd does not exit correctly and
we have the following traces:

Sep 10 07:58:24.616465 ModemManager[1158]: <info>  (tty/ttyUSB0): released by device '/sys/devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb4/4-1'
Sep 10 07:58:24.620314 pppd[2292]: Modem hangup
Sep 10 07:58:24.621368 ModemManager[1158]: <info>  (tty/ttyUSB1): released by device '/sys/devices/pci0000:00/0000:00:1c.0/0000:01:00.0/usb4/4-1'
Sep 10 07:58:24.621835 ModemManager[1158]: <warn>  (ttyUSB1): could not re-acquire serial port lock: (5) Input/output error
Sep 10 07:58:24.621358 NetworkManager[1871]: <debug> ppp-manager: set-ifindex 4
Sep 10 07:58:24.621369 NetworkManager[1871]: <warn>  ppp-manager: can't change the ifindex from 4 to 4
Sep 10 07:58:24.623982 NetworkManager[1871]: <info>  device (ttyUSB0): state change: activated -> unmanaged (reason 'removed', sys-iface-state: 'removed')
Sep 10 07:58:24.624411 NetworkManager[1871]: <debug> kill child process 'pppd' (2292): wait for process to terminate after sending SIGTERM (15) (send SIGKILL in 1500 milliseconds)...
Sep 10 07:58:24.624440 NetworkManager[1871]: <debug> modem-broadband[ttyUSB0]: notifying ModemManager about the modem disconnection
Sep 10 07:58:24.626591 NetworkManager[1871]: <debug> modem-broadband[ttyUSB0]: notifying ModemManager about the modem disconnection
Sep 10 07:58:24.681016 NetworkManager[1871]: <warn>  modem-broadband[ttyUSB0]: failed to disconnect modem: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface 'org.freedesktop.ModemManager1.Modem.Simple' on object at path /org/freedesktop/ModemManager1/Modem/0
Sep 10 07:58:26.126817 NetworkManager[1871]: <debug> kill child process 'pppd' (2292): process not terminated after 1502368 usec. Sending SIGKILL signal
Sep 10 07:58:26.128121 NetworkManager[1871]: <info>  device (ppp0): state change: disconnected -> unmanaged (reason 'unmanaged', sys-iface-state: 'removed')
Sep 10 07:58:26.135571 NetworkManager[1871]: <debug> kill child process 'pppd' (2292): terminated by signal 9 (1511158 usec elapsed)

This is due to nm-ppp-plugin waiting on SetIfIndex call until timeout,
which is longer than termination process timeout.

Calling g_dbus_method_invocation_return_value() on error fixes this.

Fixes: dd98ada3

https://mail.gnome.org/archives/networkmanager-list/2018-September/msg00010.html