udhcpc.hook

#!/bin/sh
# Hook script for udhcpc
# Copyright (c) 2008 Natanael Copa <natanael.copa@gmail.com>
# Augmented by Fabian Mastenbroek <mail.fabianm@gmail.com>

export broadcast
export dns
export domain
export interface
export ip
export mask
export metric
export staticroutes
export router
export subnet

export PATH=/usr/bin:/bin:/usr/sbin:/sbin

# Use busybox if iproute2 is not installed
if ! command -v ip > /dev/null 2>&1; then
    alias ip="busybox ip"
fi

run_scripts() {
    local dir=$1
    if [ -d $dir ]; then
        for i in $dir/*; do
            [ -f $i ] && $i
        done
    fi
}

deconfig() {
    ip -4 addr flush dev "$interface"
}

if_index() {
    if [ -e /sys/class/net/"$interface"/ifindex ]; then
        cat /sys/class/net/"$interface"/ifindex
    else
        ip -4 link show dev "$interface" | head -n1 | cut -d: -f1
    fi
}

calc_metric() {
    echo $((200 + $(if_index)))
}

route_add() {
    local to=$1 gw=$2 num=$3
    # special case for /32 subnets:
    # /32 instructs kernel to always use routing for all outgoing packets
    # (they can never be sent to local subnet - there is no local subnet for /32).
    # Used in datacenters, avoids the need for private ip-addresses between two hops.
    if [ "$subnet" = "255.255.255.255" ]; then
        ip -4 route add $gw dev $interface
    fi
    ip -4 route add $to via $gw dev $interface \
        metric $(($num + ${IF_METRIC:-$(calc_metric)}))
}

routes() {
    [ -z "$router" ] && [ -z "$staticroutes" ] && return
    for i in $NO_GATEWAY; do
        [ "$i" = "$interface" ] && return
    done
    while ip -4 route del default via dev $interface 2>/dev/null; do
        :
    done
    local num=0
    # RFC3442:
    # If the DHCP server returns both a Classless Static Routes option
    # and a Router option, the DHCP client MUST ignore the Router option.
    if [ -n "$staticroutes" ]; then
        # static routes format: dest1/mask gw1 ... destn/mask gwn
        set -- $staticroutes
        while [ -n "$1" ] && [ -n "$2" ]; do
            local dest="$1" gw="$2"
            if [ "$gw" != "0.0.0.0" ]; then
                route_add $dest $gw $num && num=$(($num + 1))
            fi
            shift 2
        done
    else
        local gw=
        for gw in $router; do
            route_add 0.0.0.0/0 $gw $num && num=$(($num + 1))
        done
    fi
}

bound() {
    ip -4 addr add $ip/$mask ${broadcast:+broadcast $broadcast} dev $interface
    ip -4 link set dev $interface up
    routes

    for i in $dns; do
            echo "nameserver $i"
    done;;
}

renew() {
    if ! ip -4 addr show dev $interface | grep $ip/$mask; then
        ip -4 addr flush dev $interface
        ip -4 addr add $ip/$mask ${broadcast:+broadcast $broadcast} dev $interface
    fi

    local i
    for i in $router; do
        if ! ip -4 route show | grep ^default | grep $i; then
            routes
            break
        fi
    done

    for i in $dns; do
        echo "nameserver $i"
    done;;
}

case "$1" in
deconfig | renew | bound)
    $1
    ;;
leasefail)
    echo "udhcpc failed to get a DHCP lease" >&2
    ;;
nak)
    echo "udhcpc received DHCP NAK" >&2
    ;;
*)
    echo "Error: this script should be called from udhcpc" >&2
    exit 1
    ;;
esac
exit 0