OpenWrt Hotplug Scripts on Interface Events

OpenWrt supports interface hotplug events. You can run scripts when an interface goes up or down.

Simple startup tasks can go into /etc/rc.local, but hotplug scripts are best when you need actions on network state changes.

1. Save this file to /etc/hotplug.d/iface/95-sample-hotplug

#!/bin/sh
# put this in /etc/hotplug.d/iface
if [ "$ACTION" == "ifup" -a "$INTERFACE" == "eth0" ]
then
# your scripts here(1) #
fi
if [ "$ACTION" == "ifdown" -a "$INTERFACE" == "eth0" ]
then
# your scripts here(2) #
fi

Replace eth0 with the interface you want to monitor (e.g. br-lan).

The first block runs when the interface comes up; the second runs when the interface goes down.

2. Make it executable

chmod a+x /etc/hotplug.d/iface/95-sample-hotplug

3. Toggle the interface in the web UI and inspect logs with logread and dmesg.

Reference: OpenWrt hotplug