#!/bin/bash

# Explicitly set the PATH to that of ENV_SUPATH in /etc/login.defs and unset
# various other variables. We need to do this so /sbin/dhclient cannot abuse
# the environment to escape AppArmor confinement via this script
# (LP: #1045986). This can be removed once AppArmor supports environment
# filtering (LP: #1045985)
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export ENV=
export BASH_ENV=
export CDPATH=
export GLOBIGNORE=
export BASH_XTRACEFD=

# dhclient-script for Linux. Dan Halbert, March, 1997.
# Updated for Linux 2.[12] by Brian J. Murrell, January 1999.
# Modified for Debian. Matt Zimmerman and Eloy Paris, December 2003
# Modified to remove useless tests for antiquated kernel versions that
# this doesn't even work with anyway, and introduces a dependency on /usr
# being mounted, which causes cosmetic errors on hosts that NFS mount /usr
# Andrew Pollock, February 2005
# Modified to work on point-to-point links. Andrew Pollock, June 2005
# Modified to support passing the parameters called with to the hooks. Andrew Pollock, November 2005

# The alias handling in here probably still sucks. -mdz

# wait for given file to be writable
wait_for_rw() {
local file=$1
# Find out whether we are going to mount / rw
exec 9>&0 </etc/fstab
rootmode=rw
while read dev mnt type opts dump pass junk; do
[ "$mnt" != / ] && continue
case "$opts" in
ro|ro,*|*,ro|*,ro,*)
rootmode=ro
;;
esac
done
exec 0>&9 9>&-

# Wait for $file to become writable
if [ "$rootmode" = "rw" ]; then
while ! { : >> "$file"; } 2>/dev/null; do
sleep 0.1
done
fi
}

# update /etc/resolv.conf based on received values
make_resolv_conf() {
local new_resolv_conf

# DHCPv4
if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
[ -n "$new_domain_name_servers" ]; then
resolv_conf=$(readlink -f "/etc/resolv.conf" 2>/dev/null) ||
resolv_conf="/etc/resolv.conf"

new_resolv_conf="${resolv_conf}.dhclient-new.$$"
wait_for_rw "$new_resolv_conf"
rm -f $new_resolv_conf

if [ -n "$new_domain_name" ]; then
echo domain ${new_domain_name%% *} >>$new_resolv_conf
fi

if [ -n "$new_domain_search" ]; then
if [ -n "$new_domain_name" ]; then
domain_in_search_list=""
for domain in $new_domain_search; do
if [ "$domain" = "${new_domain_name}" ] ||
[ "$domain" = "${new_domain_name}." ]; then
domain_in_search_list="Yes"
fi
done
if [ -z "$domain_in_search_list" ]; then
new_domain_search="$new_domain_name $new_domain_search"
fi
fi
echo "search ${new_domain_search}" >> $new_resolv_conf
elif [ -n "$new_domain_name" ]; then
echo "search ${new_domain_name}" >> $new_resolv_conf
fi

if [ -n "$new_domain_name_servers" ]; then
for nameserver in $new_domain_name_servers; do
echo nameserver $nameserver >>$new_resolv_conf
done
else # keep 'old' nameservers
sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p $resolv_conf >>$new_resolv_conf
fi

if [ -f $resolv_conf ]; then
chown --reference=$resolv_conf $new_resolv_conf
chmod --reference=$resolv_conf $new_resolv_conf
fi
mv -f $new_resolv_conf $resolv_conf
# DHCPv6
elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
resolv_conf=$(readlink -f "/etc/resolv.conf" 2>/dev/null) ||
resolv_conf="/etc/resolv.conf"

new_resolv_conf="${resolv_conf}.dhclient-new.$$"
wait_for_rw "$new_resolv_conf"
rm -f $new_resolv_conf

if [ -n "$new_dhcp6_domain_search" ]; then
echo "search ${new_dhcp6_domain_search}" >> $new_resolv_conf
fi

if [ -n "$new_dhcp6_name_servers" ]; then
for nameserver in $new_dhcp6_name_servers; do
# append %interface to link-local-address nameservers
if [ "${nameserver##fe80::}" != "$nameserver" ] ||
[ "${nameserver##FE80::}" != "$nameserver" ]; then
nameserver="${nameserver}%${interface}"
fi
echo nameserver $nameserver >>$new_resolv_conf
done
else # keep 'old' nameservers
sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p $resolv_conf >>$new_resolv_conf
fi

if [ -f $resolv_conf ]; then
chown --reference=$resolv_conf $new_resolv_conf
chmod --reference=$resolv_conf $new_resolv_conf
fi
mv -f $new_resolv_conf $resolv_conf
fi
}

# set host name
set_hostname() {
local current_hostname

if [ -n "$new_host_name" ]; then
current_hostname=$(hostname)

# current host name is empty, '(none)' or 'localhost' or differs from new one from DHCP
if [ -z "$current_hostname" ] ||
[ "$current_hostname" = '(none)' ] ||
[ "$current_hostname" = 'localhost' ] ||
[ "$current_hostname" = "$old_host_name" ]; then
if [ "$new_host_name" != "$old_host_name" ]; then
hostname "$new_host_name"
fi
fi
fi
}

# run given script
run_hook() {
local script
local exit_status
script="$1"
shift # discard the first argument, then the rest are the script's

if [ -f $script ]; then
. $script "$@"
fi

if [ -n "$exit_status" ] && [ "$exit_status" -ne 0 ]; then
logger -p daemon.err "$script returned non-zero exit status $exit_status"
fi

return $exit_status
}

# run scripts in given directory
run_hookdir() {
local dir
local exit_status
dir="$1"
shift # See run_hook

if [ -d "$dir" ]; then
for script in $(run-parts --list $dir); do
run_hook $script "$@" || true
exit_status=$?
done
fi

return $exit_status
}

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

# Source the documented exit-hook script, if it exists
if ! run_hook /etc/dhcp/dhclient-exit-hooks "$@"; then
exit_status=$?
fi

# Now run scripts in the Debian-specific directory.
if ! run_hookdir /etc/dhcp/dhclient-exit-hooks.d "$@"; then
exit_status=$?
fi

exit $exit_status
}


# The 576 MTU is only used for X.25 and dialup connections
# where the admin wants low latency. Such a low MTU can cause
# problems with UDP traffic, among other things. As such,
# disallow MTUs from 576 and below by default, so that broken
# MTUs are ignored, but higher stuff is allowed (1492, 1500, etc).
if [ -z "$new_interface_mtu" ] || [ "$new_interface_mtu" -le 576 ]; then
new_interface_mtu=''
fi


# The action starts here

# Invoke the local dhcp client enter hooks, if they exist.
run_hook /etc/dhcp/dhclient-enter-hooks
run_hookdir /etc/dhcp/dhclient-enter-hooks.d

# Execute the operation
case "$reason" in

### DHCPv4 Handlers

MEDIUM|ARPCHECK|ARPSEND)
# Do nothing
;;
PREINIT)
# The DHCP client is requesting that an interface be
# configured as required in order to send packets prior to
# receiving an actual address. - dhclient-script(8)

# ensure interface is up
ip link set dev ${interface} up

if [ -n "$alias_ip_address" ]; then
# flush alias IP from interface
ip -4 addr flush dev ${interface} label ${interface}:0
fi

;;

BOUND|RENEW|REBIND|REBOOT)
set_hostname

if [ -n "$old_ip_address" ] && [ -n "$alias_ip_address" ] &&
[ "$alias_ip_address" != "$old_ip_address" ]; then
# alias IP may have changed => flush it
ip -4 addr flush dev ${interface} label ${interface}:0
fi

if [ -n "$old_ip_address" ] &&
[ "$old_ip_address" != "$new_ip_address" ]; then
# leased IP has changed => flush it
ip -4 addr flush dev ${interface} label ${interface}
fi

if [ -z "$old_ip_address" ] ||
[ "$old_ip_address" != "$new_ip_address" ] ||
[ "$reason" = "BOUND" ] || [ "$reason" = "REBOOT" ]; then
# new IP has been leased or leased IP changed => set it
ip -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \
${new_broadcast_address:+broadcast $new_broadcast_address} \
dev ${interface} label ${interface}

if [ -n "$new_interface_mtu" ]; then
# set MTU
ip link set dev ${interface} mtu ${new_interface_mtu}
fi

# if we have $new_rfc3442_classless_static_routes then we have to
# ignore $new_routers entirely
if [ ! "$new_rfc3442_classless_static_routers" ]; then
# set if_metric if IF_METRIC is set or there's more than one router
if_metric="$IF_METRIC"
if [ "${new_routers%% *}" != "${new_routers}" ]; then
if_metric=${if_metric:-1}
fi

for router in $new_routers; do
if [ "$new_subnet_mask" = "255.255.255.255" ]; then
# point-to-point connection => set explicit route
ip -4 route add ${router} dev $interface >/dev/null 2>&1
fi

# set default route
ip -4 route add default via ${router} dev ${interface} \
${if_metric:+metric $if_metric} >/dev/null 2>&1

if [ -n "$if_metric" ]; then
if_metric=$((if_metric+1))
fi
done
fi
fi

if [ -n "$alias_ip_address" ] &&
[ "$new_ip_address" != "$alias_ip_address" ]; then
# separate alias IP given, which may have changed
# => flush it, set it & add host route to it
ip -4 addr flush dev ${interface} label ${interface}:0
ip -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \
dev ${interface} label ${interface}:0
ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
fi

# update /etc/resolv.conf
make_resolv_conf

;;

EXPIRE|FAIL|RELEASE|STOP)
if [ -n "$alias_ip_address" ]; then
# flush alias IP
ip -4 addr flush dev ${interface} label ${interface}:0
fi

if [ -n "$old_ip_address" ]; then
# flush leased IP
ip -4 addr flush dev ${interface} label ${interface}
fi

if [ -n "$alias_ip_address" ]; then
# alias IP given => set it & add host route to it
ip -4 addr add ${alias_ip_address}${alias_network_arg} \
dev ${interface} label ${interface}:0
ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
fi

;;

TIMEOUT)
if [ -n "$alias_ip_address" ]; then
# flush alias IP
ip -4 addr flush dev ${interface} label ${interface}:0
fi

# set IP from recorded lease
ip -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \
${new_broadcast_address:+broadcast $new_broadcast_address} \
dev ${interface} label ${interface}

if [ -n "$new_interface_mtu" ]; then
# set MTU
ip link set dev ${interface} mtu ${new_interface_mtu}
fi

# if there is no router recorded in the lease or the 1st router answers pings
if [ -z "$new_routers" ] || ping -q -c 1 "${new_routers%% *}"; then
# if we have $new_rfc3442_classless_static_routes then we have to
# ignore $new_routers entirely
if [ ! "$new_rfc3442_classless_static_routes" ]; then
if [ -n "$alias_ip_address" ] &&
[ "$new_ip_address" != "$alias_ip_address" ]; then
# separate alias IP given => set up the alias IP & add host route to it
ip -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \
dev ${interface} label ${interface}:0
ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
fi

# set if_metric if IF_METRIC is set or there's more than one router
if_metric="$IF_METRIC"
if [ "${new_routers%% *}" != "${new_routers}" ]; then
if_metric=${if_metric:-1}
fi

# set default route
for router in $new_routers; do
ip -4 route add default via ${router} dev ${interface} \
${if_metric:+metric $if_metric} >/dev/null 2>&1

if [ -n "$if_metric" ]; then
if_metric=$((if_metric+1))
fi
done
fi

# update /etc/resolv.conf
make_resolv_conf
else
# flush all IPs from interface
ip -4 addr flush dev ${interface}
exit_with_hooks 2 "$@"
fi

;;

### DHCPv6 Handlers
# TODO handle prefix change: ?based on ${old_ip6_prefix} and ${new_ip6_prefix}?

PREINIT6)
# ensure interface is up
ip link set ${interface} up

# flush any stale global permanent IPs from interface
ip -6 addr flush dev ${interface} scope global permanent

;;

BOUND6|RENEW6|REBIND6)
if [ "${new_ip6_address}" ] && [ "${new_ip6_prefixlen}" ]; then
# set leased IP
ip -6 addr add ${new_ip6_address}/${new_ip6_prefixlen} \
dev ${interface} scope global
fi

# update /etc/resolv.conf
if [ "${reason}" = BOUND6 ] ||
[ "${new_dhcp6_name_servers}" != "${old_dhcp6_name_servers}" ] ||
[ "${new_dhcp6_domain_search}" != "${old_dhcp6_domain_search}" ]; then
make_resolv_conf
fi

;;

DEPREF6)
if [ -z "${cur_ip6_prefixlen}" ]; then
exit_with_hooks 2
fi

# set preferred lifetime of leased IP to 0
ip -6 addr change ${cur_ip6_address}/${cur_ip6_prefixlen} \
dev ${interface} scope global preferred_lft 0

;;

EXPIRE6|RELEASE6|STOP6)
if [ -z "${old_ip6_address}" ] || [ -z "${old_ip6_prefixlen}" ]; then
exit_with_hooks 2
fi

# delete leased IP
ip -6 addr del ${old_ip6_address}/${old_ip6_prefixlen} \
dev ${interface}

;;
esac

exit_with_hooks 0