If interface is getting down by netifd (unplug ethernet cable)
mwan3track will not recognize this change. It will also generate an
additional down event when he notice does his tracking interface is offline.
Mwan3track will now be informed by a signal (trap) USR1 during down event
that the interface is already down. An additional down event will not be
generated.
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
If mwan3track detects a failure the interval check will change to
"failure_interval" value until this interface is declared "offline".
After interface gets "offline" normal "interval" value is used again.
If interface ping is successful again "recovery_interval" value is used until
interface is declared "online" again.
Using the different intervals will accelerate the wan line detections on
failure and recovery.
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
