Openwrt/openwrt/package/base-files/default/usr/share/udhcpc/default.script

#!/bin/sh
[ -z "$1" ] && echo "Error: should be run by udhcpc" && exit 1

RESOLV_CONF="/tmp/resolv.conf"

hotplug_event() {
	nvram show 2>&- | grep _proto=dhcp | {
		while :; do
			read FOO
			[ -z "$FOO" ] && break
			FOO="${FOO%%_*}"
			[ "$(nvram get ${FOO}_ifname)" = "${interface}" ] || continue
			env -i ACTION="$1" INTERFACE="${FOO}" PROTO=dhcp /sbin/hotplug iface
		done
	}
}

case "$1" in
	deconfig)
		ifconfig $interface 0.0.0.0
		hotplug_event ifdown
	;;
	renew|bound)
		ifconfig $interface $ip \
		netmask ${subnet:-255.255.255.0} \
		broadcast ${broadcast:-+}

		if [ -n "$router" ] ; then
			echo "deleting routers"
			while route del default gw 0.0.0.0 dev $interface ; do :; done
					
			for i in $router ; do
				route add default gw $i dev $interface
			done
		fi

		echo -n > $RESOLV_CONF
		${domain:+echo search $domain} >> $RESOLV_CONF
		for i in $dns ; do
			echo adding dns $i
			echo nameserver $i >> $RESOLV_CONF
		done
		
		hotplug_event ifup
		
		# user rules
		[ -f /etc/udhcpc.user ] && . /etc/udhcpc.user
	;;
esac

exit 0