dhcp/linux

#!/bin/bash
# dhclient-script for Linux. Dan Halbert, March, 1997.
# Updated for Linux 2.[12] by Brian J. Murrell, January 1999.
# No guarantees about this. I'm a novice at the details of Linux
# networking.
#
# Modified by David Cantrell <dcantrell@redhat.com> for Fedora and RHEL

# Notes:

# 0. This script is based on the netbsd script supplied with dhcp-970306.

# 1. ifconfig down apparently deletes all relevant routes and flushes
# the arp cache, so this doesn't need to be done explicitly.

# 2. The alias address handling here has not been tested AT ALL.
# I'm just going by the doc of modern Linux ip aliasing, which uses
# notations like eth0:0, eth0:1, for each alias.

# 3. I have to calculate the network address, and calculate the broadcast
# address if it is not supplied. This might be much more easily done
# by the dhclient C code, and passed on.

PATH=/bin:/usr/bin

function save_previous() {
    if [ -e $1 ]; then
        mv $1 $1.predhclient
    else
        echo ''> $1.predhclient
    fi
}

make_resolv_conf() {
    if [ "${PEERDNS}" == "no" ]; then
        return
    fi

    if [ x$reason == xRENEW ] &&
       [ "$new_domain_name" == "$old_domain_name" ] && 
       [ "$new_domain_name_servers" == "$old_domain_name_servers" ]; then
        return
    fi

    if [ -n "$new_domain_name" ] || [ -n "$new_domain_name_servers" ]; then
        cp -fp /etc/resolv.conf /etc/resolv.conf.predhclient
        rscf=`mktemp /tmp/XXXXXX`;
        echo '; generated by /sbin/dhclient-script' > $rscf

        if [ -n "$SEARCH" ]; then
            echo search $SEARCH >> $rscf
        else
            if [ -n "$new_domain_name" ]; then
                echo search $new_domain_name >> $rscf
            fi
        fi

        for nameserver in $new_domain_name_servers; do
            echo nameserver $nameserver >> $rscf
        done

        change_resolv_conf $rscf
        rm -f $rscf
    fi
}

# Must be used on exit.   Invokes the local dhcp client exit hooks, if any.
exit_with_hooks() {
    exit_status=$1

    if [ -f /etc/dhclient-exit-hooks ]; then
        . /etc/dhclient-exit-hooks
    fi

    # probably should do something with exit status of the local script
    exit $exit_status
}

# Invoke the local dhcp client enter hooks, if they exist.
if [ -f /etc/dhclient-enter-hooks ]; then
    exit_status=0
    . /etc/dhclient-enter-hooks
    # allow the local script to abort processing of this state
    # local script must set exit_status variable to nonzero.
    if [ $exit_status -ne 0 ]; then
        exit $exit_status
    fi
fi

# Import Red Hat Linux configuration
cd /etc/sysconfig/network-scripts;
. /etc/sysconfig/network-scripts/network-functions
. /etc/rc.d/init.d/functions

[ -f ../network ] && . ../network
[ -f ../networking/network ] && . ../networking/network

CONFIG=$interface

need_config ${CONFIG}

if [ -f "${CONFIG}" ]; then 
    source_config
else
    echo $"$0: configuration for $interface not found. Continuing with defaults." >&2
fi

source_config

release=$(uname -r)
relmajor=$(echo $release | cut -f1 -d'.')
relminor=$(echo $release | cut -f2 -d'.')

# simple IP arithmetic functions:
function quad2num() {
    if [ $# -eq 4 ]; then
        let n="$1<<24|$2<<16|$3<<8|$4"
        echo $n
        return 0
    fi
    echo '0'
    return 1
}

function ip2num() {
    IFS='.' quad2num $1
}

function num2ip() {
    let n="$1"
    let o1='(n>>24)&0xff'
    let o2='(n>>16)&0xff'
    let o3='(n>>8)&0xff'
    let o4='n & 0xff'
    echo $o1.$o2.$o3.$o4
}

function mask() {
    ip=$1
    m=$2
    let ip=$(IFS='.' ip2num $ip)
    let m=$(IFS='.' ip2num $m)
    let n='ip&m'
    num2ip $n
}

function mask_bits() {
    ip=$1
    let ip=$(IFS='.' ip2num $ip)
    let bits=0
    for ((bit=1; '((ip&bit)==0) && (bits < 32)'; 'bit<<=1')) do
        let bits+=1
    done
    let n_bits=32-bits
    echo $n_bits
}

function class_bits() {
    let ip=$(IFS='.' ip2num $1)
    let bits=32
    let mask='255'
    for ((i=0; i <= 3; i++, 'mask<<=8')); do
        let v='ip&mask'
        if [ "$v" -eq 0 ] ; then
             let bits-=8
        else
             break
        fi
    done
    echo $bits
}

function routerReachable() {
    # Handle silly DHCP servers that give us a router not on our subnet:
    router=$1
    routerSubnet=$(mask $router $new_subnet_mask)
    mySubnet=$(mask $new_ip_address $new_subnet_mask)
    unreachable=0
    if [ "$routerSubnet" != "$mySubnet" ]; then
        unreachable=1
        if /sbin/arping -f -q -I $interface -w2 $router; then
             /sbin/ip route add ${router}/32 dev $interface
             if [ $? -eq 0 ]; then
                 unreachable=0
             else
                 /usr/bin/logger -p local7.notice -t "NET"  "dhclient: failed to create host route for unreachable router $router not on subnet $mySubnet";
             fi
        else
             unreachable=1
             if [ -x /usr/bin/logger ]; then
                 /usr/bin/logger -p local7.notice -t "NET"  "dhclient: DHCP router $router is unreachable on DHCP subnet $mySubnet router subnet $routerSubnet";
             fi
        fi
    fi
    return $unreachable
}

function add_default_gateway() {
    router=$1
    metric=''
    if [ $# -gt 1 ] && [ "$2" -gt 0 ]; then
        metric="metric $2"
    fi
    if routerReachable $router ; then
        /sbin/ip route replace default via $router dev $interface $metric
        if [ $? -ne 0 ]; then
            /usr/bin/logger -p local7.notice -t "NET"  'dhclient: failed to create default route: '$router dev $interface $metric
            return 1
        else
            return 0
        fi
    fi
    return 1
}

function dhconfig() {
    if [ x$old_ip_address != x ] && [ x$alias_ip_address != x ] && [ x$alias_ip_address != x$old_ip_address ]; then
        # Possible new alias. Remove old alias.
        ifconfig $interface:0- inet 0
    fi

    if [ x$old_ip_address != x ] && [ x$old_ip_address != x$new_ip_address ]; then
        # IP address changed. Bringing down the interface will delete all
        # routes, and clear the ARP cache.
        ifconfig $interface inet 0 down
    fi

    if [ x$reason = xBOUND ] || [ x$reason = xREBOOT ] ||
       [ x$old_ip_address  != x$new_ip_address ] ||
       [ x$old_subnet_mask != x$new_subnet_mask ] ||
       [ x$new_network_number != x$new_network_number ] ||
       [ x$old_broadcast_address != x$new_broadcast_address ] ||
       [ "x$old_routers" != "x$new_routers" ] ||
       [ x$old_interface_mtu != x$new_interface_mtu ] ; then
        ifconfig $interface inet $new_ip_address $new_subnet_arg $new_broadcast_arg
        if [ -n "$new_interface_mtu" ]; then
            /sbin/ip link set $interface mtu $new_interface_mtu
        fi

        if [ -x /etc/dhclient-${interface}-up-hooks ]; then
            . /etc/dhclient-${interface}-up-hooks
        elif [ -x /etc/dhclient-up-hooks ]; then
            . /etc/dhclient-up-hooks
        fi

        prefix_bits=$(mask_bits $new_subnet_mask)
        # Add a network route to the computed network address.
        if [ $relmajor -lt 2 ] || ( [ $relmajor -eq 2 ] && [ $relminor -eq 0 ] ); then
            /sbin/ip route replace ${new_network_number}/${prefix_bits} dev $interface
            if [ $added_old_broadcast_route -eq 1 ]; then
                /sbin/ip route del default
            fi
        fi

        if [[ (( -z "$GATEWAYDEV" ) || ( "$GATEWAYDEV" = "$interface" )) && (( -z "$GATEWAY" ) || (( -n "$DHCLIENT_IGNORE_GATEWAY" ) && ( "$DHCLIENT_IGNORE_GATEWAY" = [Yy]* ))) ]]; then
            metric=${METRIC:-''}
            let i=${METRIC:-0}
            default_routers=()

            for router in $new_routers; do
                added_router=0

                for r in ${default_routers[@]}; do
                    if [ "$r" == "$router" ]; then
                        added_router=1
                    fi
                done

                if [ -z "$router" ] || [ "$added_router" -eq 1 ] || [ $(IFS=. ip2num $router) -le 0 ] || [[ ( "$router" = "$new_broadcast_address" ) && ( "$new_subnet_mask" != "255.255.255.255" ) ]]; then
                    continue
                fi

                default_routers=(${default_routers[@]} $router)
                add_default_gateway $router $metric
                let i=i+1
                metric=$i
            done
        elif [[ (( -z "$GATEWAYDEV" ) || ( "$GATEWAYDEV" = "$interface" )) && ( -n "$GATEWAY" ) ]]; then
            routerSubnet=$(mask $GATEWAY $new_subnet_mask)
            mySubnet=$(mask $new_ip_address $new_subnet_mask)

            if [ "$routerSubnet" = "$mySubnet" ]; then
                /sbin/ip route replace default via $GATEWAY dev $interface
            fi
        fi

        # static routes
        if [ "x$new_static_routes" != x ]; then
            IFS=', 	' static_routes=($new_static_routes)
            route_targets=()

            for((i=0; i<${#static_routes[@]}; i+=2)); do
                target=${static_routes[$i]}
                gateway=${static_routes[$i+1]}
                metric=''

                for t in ${route_targets[@]}; do
                    if [ $t == $target ]; then
                        if [ -z "$metric" ]; then
                            metric=1
                        else
                            ((metric=metric+1))
                        fi
                    fi
                done

                if [ -n "$metric" ]; then
                    metric="metric $metric"
                fi

                if routerReachable $gateway; then
                    /sbin/ip route replace ${target}/$(class_bits $target) via ${gateway} dev $interface ${metric}

                    if [ $? -ne 0 ]; then
                        /usr/bin/logger -p local7.notice -t 'NET' 'dhclient: failed to create static route:' ${target}/`class_bits $target` via ${gateway} dev $interface ${metric}
                    else
                        route_targets=(${route_targets[@]} $target)
                    fi
                fi
            done
        fi
    fi

    if [ x$new_ip_address != x$alias_ip_address ] && [ x$alias_ip_address != x ]; then
        ifconfig $interface:0- inet 0
        ifconfig $interface:0 inet $alias_ip_address $alias_subnet_arg
        /sbin/ip route replace ${alias_ip_address}/32 dev $interface:0
    fi

    make_resolv_conf

    if [ -n "$new_host_name" ] && need_hostname; then
        hostname $new_host_name
    fi

    if [ "${PEERNIS}" = no ]; then
        :
    elif [ -n "$new_nis_domain" ]; then
        domainname "$new_nis_domain"
        save_previous /etc/yp.conf
        let contents=0
        echo '# generated by /sbin/dhclient-script' > /etc/yp.conf

        if [ -n "$new_nis_servers" ]; then
            for I in $new_nis_servers; do
                echo "domain $new_nis_domain server $I" >> /etc/yp.conf
                let contents=contents+1
            done
        else
            echo "domain $new_nis_domain broadcast" >> /etc/yp.conf
            let contents=contents+1
        fi

        if [ $contents -gt 0 ] && [ -r /var/run/ypbind.pid ] && yppid=$(cat /var/run/ypbind.pid) && [ -d /proc/${yppid} ] && [ "$(if [ -x /usr/bin/readlink ]; then readlink /proc/${yppid}/exe; else echo /sbin/ypbind; fi)" = "/sbin/ypbind" ]; then
            kill -HUP $yppid
        fi
    elif [ -n "$new_nis_servers" ]; then
        save_previous /etc/yp.conf
        echo '# generated by /sbin/dhclient-script' > /etc/yp.conf
        let contents=0

        for I in $new_nis_servers; do
            echo "ypserver $I" >> /etc/yp.conf
            let contents=contents+1
        done

        if [ $contents -gt 0 ] && [ -r /var/run/ypbind.pid ] && yppid=$(cat /var/run/ypbind.pid) && [ -d /proc/${yppid} ] && [ "$(if [ -x /usr/bin/readlink ]; then readlink /proc/${yppid}/exe; else echo /sbin/ypbind; fi)" = "/sbin/ypbind" ]; then
            kill -HUP $yppid
        fi
    fi

    if [ -n "$DHCP_TIME_OFFSET_SETS_TIMEZONE" ] && [[ "$DHCP_TIME_OFFSET_SETS_TIMEZONE" = [yY1]* ]]; then
        if [ -n "$new_time_offset" ]; then
            # DHCP option "time-offset" is requested by default and should be
            # handled.  The geographical zone abbreviation cannot be determined
            # from the GMT offset, but the $ZONEINFO/Etc/GMT$offset file can be
            # used - note: this disables DST.
            ((z=new_time_offset/3600))
            ((hoursWest=$(printf '%+d' $z)))

            if (( $hoursWest < 0 )); then
                # tzdata treats negative 'hours west' as positive 'gmtoff'!
                ((hoursWest*=-1))
            fi

            tzfile=/usr/share/zoneinfo/Etc/GMT$(printf '%+d' $hoursWest)
            if [ -e $tzfile ]; then
                /bin/mv -f /etc/localtime /etc/localtime.predhclient
                /bin/cp -fp $tzfile /etc/localtime
                /bin/touch /etc/localtime
            fi
        fi
    fi

    if [ "${PEERNTP}" = no ]; then
        :
    elif [ -n "$new_ntp_servers" ] && [ -e /etc/ntp.conf ]; then
        save_previous /etc/ntp.conf
        /bin/egrep -v '^server .*  # added by /sbin/dhclient-script$'< /etc/ntp.conf.predhclient > /etc/ntp.conf

        for s in $new_ntp_servers; do
            echo "server $s  # added by /sbin/dhclient-script" >> /etc/ntp.conf
        done

        if [ -x /usr/bin/diff ] && /usr/bin/diff -q /etc/ntp.conf /etc/ntp.conf.predhclient >/dev/null 2>&1; then
            :
        else
            /sbin/service ntpd condrestart >/dev/null 2>&1
        fi
    fi
}

if [ x$new_broadcast_address != x ] && [ x$new_subnet_mask != x ] && [ "$new_subnet_mask" != "255.255.255.255" ]; then
    new_broadcast_arg="broadcast $new_broadcast_address"
fi

if [ x$old_broadcast_address != x ]; then
    old_broadcast_arg="broadcast $old_broadcast_address"
fi

if [ x$new_subnet_mask != x ]; then
    new_subnet_arg="netmask $new_subnet_mask"
fi

if [ x$old_subnet_mask != x ]; then
    old_subnet_arg="netmask $old_subnet_mask"
fi

if [ x$alias_subnet_mask != x ]; then
    alias_subnet_arg="netmask $alias_subnet_mask"
fi

if [ x$reason = xMEDIUM ]; then
    # Linux doesn't do mediums (ok, ok, media).
    exit_with_hooks 0
fi

added_old_broadcast_route=0
if [ x$reason = xPREINIT ]; then
    if [ x$alias_ip_address != x ]; then
        # Bring down alias interface. Its routes will disappear too.
        ifconfig $interface:0- inet 0
    fi

    if [ x$keep_old_ip = xyes ]; then
        ifconfig $interface up
    elif [ $relmajor -lt 2 ] || ( [ $relmajor -eq 2 ] && [ $relminor -eq 0 ] )   then
        ifconfig $interface inet 0.0.0.0 netmask 0.0.0.0 broadcast 255.255.255.255 up
        # Add route to make broadcast work. Do not omit netmask.
        /sbin/ip route replace default dev $interface && added_old_broadcast_route=1
    else
        ifconfig $interface 0 up
    fi

    # We need to give the kernel some time to get the interface up.
    # sleep 1
    # I don't think this is necessary with modern kernels - no problems found
    # during testing - JVD, 2005-06-17
    # but just in case:
    if [ -n "$DHCLIENT_DELAY" ] && [ "$DHCLIENT_DELAY" -gt 0 ] ; then
        sleep $DHCLIENT_DELAY
    fi

    exit_with_hooks 0
fi

if [ x$reason = xARPCHECK ] || [ x$reason = xARPSEND ]; then
    if [ -z "$new_ip_address" ] || [ -z "$interface" ] ||  /sbin/arping -q -f -c 2 -w 3 -D -I ${interface} ${new_ip_address}; then
        exit_with_hooks 0
    else
        exit_with_hooks 1
    fi
fi

if [ x$reason = xBOUND ] || [ x$reason = xRENEW ] || \
   [ x$reason = xREBIND ] || [ x$reason = xREBOOT ]; then
    dhconfig
    exit_with_hooks 0
fi

if [ x$reason = xEXPIRE ] || [ x$reason = xFAIL ] || [ x$reason = xRELEASE ] \
   || [ x$reason = xSTOP ]; then
    if [ -f /etc/resolv.conf.predhclient ]; then
        change_resolv_conf /etc/resolv.conf.predhclient
        rm -f /etc/resolv.conf.predhclient
    fi

    if [ -n "$DHCP_TIME_OFFSET_SETS_TIMEZONE" ] && [[ "$DHCP_TIME_OFFSET_SETS_TIMEZONE" = [yY1]* ]]; then
        if [ -e /etc/localtime.predhclient ]; then
            /bin/rm -f /etc/localtime
            /bin/mv -f /etc/localtime.predhclient /etc/localtime
            /bin/touch /etc/localtime
        fi
    fi

    if [ -f /etc/ntp.conf.predhclient ]; then
        /bin/rm -f /etc/ntp.conf
        /bin/mv -f /etc/ntp.conf.predhclient /etc/ntp.conf
        service ntpd condrestart >/dev/null 2>&1
    fi

    if [ -f /etc/yp.conf.predhclient ]; then
        /bin/rm -f /etc/yp.conf
        /bin/mv -f /etc/yp.conf.predhclient /etc/yp.conf

        if [ -r /var/run/ypbind.pid ] && yppid=$(cat /var/run/ypbind.pid) && [ -d /proc/${yppid} ] && [ "$(if [ -x /usr/bin/readlink ]; then readlink /proc/${yppid}/exe; else echo /sbin/ypbind; fi)" = "/sbin/ypbind" ]; then
           kill -HUP $yppid
        fi
    fi

    if [ -x /etc/dhclient-${interface}-down-hooks ]; then
        . /etc/dhclient-${interface}-down-hooks
    elif [ -x /etc/dhclient-down-hooks ]; then
        . /etc/dhclient-down-hooks
    fi

    if [ x$alias_ip_address != x ]; then
        # Turn off alias interface.
        ifconfig $interface:0- inet 0
    fi

    if [ x$old_ip_address != x ]; then
        # Shut down interface, which will delete routes and clear arp cache.
        ifconfig $interface inet 0 down
    fi

    if [ x$alias_ip_address != x ]; then
        ifconfig $interface:0 inet $alias_ip_address $alias_subnet_arg
        /sbin/ip route replace ${alias_ip_address}/32 $interface:0
    fi

    exit_with_hooks 0
fi

if [ x$reason = xTIMEOUT ] && [ "x$new_routers" != 'x' ]; then
    if [ x$alias_ip_address != x ]; then
        ifconfig $interface:0- inet 0
    fi

    ifconfig $interface inet $new_ip_address $new_subnet_arg $new_broadcast_arg
    set $new_routers

    if ping -q -c 1 -w 10 -I $interface $1; then
        dhconfig
        exit_with_hooks 0
    fi

    if [ -z "${dhc_dbus}" ] || (( ( dhc_dbus & 2 ) != 2 )); then
        ifconfig $interface inet 0 down
    fi

    exit_with_hooks 1
elif [ x$reason = xTIMEOUT ]; then
    exit_with_hooks 1
fi

exit_with_hooks 0