# There are three main environment variables that are passed to this script.
#
# $ACTION
-# <ifup> Is called by netifd and mwan3track
-# <ifdown> Is called by netifd and mwan3track
-# <connected> Is only called by mwan3track if tracking was successful
-# <disconnected> Is only called by mwan3track if tracking has failed
-# $INTERFACE Name of the interface which went up or down (e.g. "wan" or "wwan")
-# $DEVICE Physical device name which interface went up or down (e.g. "eth0" or "wwan0")
+# <ifup> Is called by netifd and mwan3track.
+# <ifdown> Is called by netifd and mwan3track.
+# <connected> Is only called by mwan3track if tracking was successful.
+# <disconnected> Is only called by mwan3track if tracking has failed.
+# $INTERFACE Name of the interface an action relates to (e.g. "wan" or "wwan").
+# $DEVICE Physical device name of the interface the action relates to (e.g. "eth0" or "wwan0").
+# Note: On an ifdown event, $DEVICE is not available, use $INTERFACE instead.
+#
+# Further documentation can be found here:
+# https://openwrt.org/docs/guide-user/network/wan/multiwan/mwan3#alertsnotifications