#!/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.

# 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.

# 4. TIMEOUT not tested. ping has a flag I don't know, and I'm suspicious
# of the 1ドル in its args.

# 5. Script refresh in 2017. The aliasing code was too convoluted and needs
# to go away. Migrated DHCPv4 script to ip command from iproute2 suite.
# This is based on Debian script with some tweaks. ifconfig is no longer
# used. Everything is done using ip tool from ip-route2.

# 'ip' just looks too weird. Also, we now have unit-tests! Those unit-tests
# overwirte this line to use a fake ip-echo tool. It's also convenient
# if your system holds ip tool in a non-standard location.
ip=/sbin/ip

# update /etc/resolv.conf based on received values
# This updated version mostly follows Debian script by Andrew Pollock et al.
make_resolv_conf() {
 local new_resolv_conf

 # DHCPv4
 if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
 [ -n "$new_domain_name_servers" ]; then
new_resolv_conf=/etc/resolv.conf.dhclient-new
 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 /etc/resolv.conf >>$new_resolv_conf
 fi

	if [ -f /etc/resolv.conf ]; then
chown --reference=/etc/resolv.conf $new_resolv_conf
	 chmod --reference=/etc/resolv.conf $new_resolv_conf
	fi
mv -f $new_resolv_conf /etc/resolv.conf
 # DHCPv6
 elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
new_resolv_conf=/etc/resolv.conf.dhclient-new
 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 /etc/resolv.conf >>$new_resolv_conf
 fi

	if [ -f /etc/resolv.conf ]; then
chown --reference=/etc/resolv.conf $new_resolv_conf
 chmod --reference=/etc/resolv.conf $new_resolv_conf
	fi
mv -f $new_resolv_conf /etc/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ドル"

 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ドル"

 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ドル

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

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

exit $exit_status
}

# This function was largely borrowed from dhclient-script that
# ships with Centos, authored by Jiri Popelka and David Cantrell
# of Redhat. Thanks guys.
add_ipv6_addr_with_DAD() {
 ${ip} -6 addr replace ${new_ip6_address}/${new_ip6_prefixlen} \
 dev ${interface} scope global valid_lft ${new_max_life} \
 preferred_lft ${new_preferred_life}

 if [ ${dad_wait_time} -le 0 ]
 then
 # if we're not waiting for DAD, assume we're good
 return 0
 fi

 # Repeatedly test whether newly added address passed
 # duplicate address detection (DAD)
 for i in $(seq 1 ${dad_wait_time}); do
sleep 1 # give the DAD some time

 addr=$(${ip} -6 addr show dev ${interface} \
 | grep ${new_ip6_address}/${new_ip6_prefixlen})

 # tentative flag == DAD is still not complete
 tentative=$(echo "${addr}" | grep tentative)
 # dadfailed flag == address is already in use somewhere else
 dadfailed=$(echo "${addr}" | grep dadfailed)

 if [ -n "${dadfailed}" ] ; then
 # address was added with valid_lft/preferred_lft 'forever',
 # remove it
 ${ip} -6 addr del ${new_ip6_address}/${new_ip6_prefixlen} \
 dev ${interface}

 exit_with_hooks 3
 fi

 if [ -z "${tentative}" ] ; then
 if [ -n "${addr}" ]; then
 # DAD is over
 return 0
 else
 # address was auto-removed (or not added at all)
 exit_with_hooks 3
 fi
 fi
 done

 return 0
}

# Invoke the local dhcp client enter hooks, if they exist.
run_hook /etc/dhclient-enter-hooks
run_hookdir /etc/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_routes" ]; 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_subnet_mask:+/$alias_subnet_mask} \
 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

 ;;

 V6ONLY)
 if [ -n "$old_ip_address" ]; then
 # flush leased IP
 ${ip} -4 addr flush dev ${interface} label ${interface}
 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

 # We need to give the kernel some time to active interface
 interface_up_wait_time=5
 for i in $(seq 0 ${interface_up_wait_time})
 do
 ${ip} link show dev ${interface} | grep -q LOWER_UP 2>&1
 if [ $? -eq 0 ]; then
break;
 fi
sleep 1
 done

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

 # Wait for duplicate address detection for this interface if the
 # --dad-wait-time parameter has been specified and is greater than
 # zero.
 if [ ${dad_wait_time} -gt 0 ]; then
 # Check if any IPv6 address on this interface is marked as
 # tentative.
 ${ip} addr show ${interface} | grep inet6 | grep tentative \
 &> /dev/null
 if [ $? -eq 0 ]; then
 # Wait for duplicate address detection to complete or for
 # the timeout specified as --dad-wait-time.
 for i in $(seq 0 $dad_wait_time)
 do
 # We're going to poll for the tentative flag every second.
 sleep 1
 ${ip} addr show ${interface} | grep inet6 | grep tentative \
 &> /dev/null
 if [ $? -ne 0 ]; then
break;
 fi
 done
 fi
 fi

 ;;

 BOUND6|RENEW6|REBIND6)
 if [ "${new_ip6_address}" ] && [ "${new_ip6_prefixlen}" ]; then
 # set leased IP
 add_ipv6_addr_with_DAD
 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