source: MondoRescue/branches/3.3/mindi-busybox/examples/udhcp/simple.script

#!/bin/sh
# udhcpc script edited by Tim Riker <Tim@Rikers.org>

RESOLV_CONF="/etc/resolv.conf"

[ -n "$1" ] || { echo "Error: should be called from udhcpc"; exit 1; }

NETMASK=""
[ -n "$subnet" ] && NETMASK="netmask $subnet"
BROADCAST="broadcast +"
[ -n "$broadcast" ] && BROADCAST="broadcast $broadcast"

case "$1" in
    deconfig)
        echo "Setting IP address 0.0.0.0 on $interface"
        ifconfig $interface 0.0.0.0
        ;;

    renew|bound)
        echo "Setting IP address $ip on $interface"
        ifconfig $interface $ip $NETMASK $BROADCAST

        if [ -n "$router" ] ; then
            echo "Deleting routers"
            while route del default gw 0.0.0.0 dev $interface ; do
                :
            done

            metric=0
            for i in $router ; do
                echo "Adding router $i"
                route add default gw $i dev $interface metric $metric
                : $(( metric += 1 ))
            done
        fi

        echo "Recreating $RESOLV_CONF"
        # If the file is a symlink somewhere (like /etc/resolv.conf
        # pointing to /run/resolv.conf), make sure things work.
        realconf=$(readlink -f "$RESOLV_CONF" 2>/dev/null || echo "$RESOLV_CONF")
        tmpfile="$realconf-$$"
        > "$tmpfile"
        [ -n "$domain" ] && echo "search $domain" >> "$tmpfile"
        for i in $dns ; do
            echo " Adding DNS server $i"
            echo "nameserver $i" >> "$tmpfile"
        done
        mv "$tmpfile" "$realconf"
        ;;
esac

exit 0