[people/stevee/network.git] / src / functions / functions.dhcpd

#!/bin/bash
###############################################################################
#                                                                             #
# IPFire.org - A linux based firewall                                         #
# Copyright (C) 2012  IPFire Network Development Team                         #
#                                                                             #
# This program is free software: you can redistribute it and/or modify        #
# it under the terms of the GNU General Public License as published by        #
# the Free Software Foundation, either version 3 of the License, or           #
# (at your option) any later version.                                         #
#                                                                             #
# This program is distributed in the hope that it will be useful,             #
# but WITHOUT ANY WARRANTY; without even the implied warranty of              #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
# GNU General Public License for more details.                                #
#                                                                             #
# You should have received a copy of the GNU General Public License           #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
#                                                                             #
###############################################################################

DHCPV6D_CONFIG_FILE="/etc/dhcp/dhcpd6.conf"
DHCPV4D_CONFIG_FILE="/etc/dhcp/dhcpd.conf"

DHCPV6D_CONFIG_DIR="${NETWORK_CONFIG_DIR}/dhcpd/ipv6"
DHCPV4D_CONFIG_DIR="${NETWORK_CONFIG_DIR}/dhcpd/ipv4"

DHCPV6D_OPTIONS_FILE="${DHCPV6D_CONFIG_DIR}/options"
DHCPV4D_OPTIONS_FILE="${DHCPV4D_CONFIG_DIR}/options"

DHCPV6D_SETTINGS_FILE="${DHCPV6D_CONFIG_DIR}/settings"
DHCPV4D_SETTINGS_FILE="${DHCPV4D_CONFIG_DIR}/settings"

DHCPD_SETTINGS="\
	AUTHORITATIVE
"
DHCPV6D_SETTINGS="\
	${DHCPD_SETTINGS} \
	PREFERRED_LIFETIME
	VALID_LIFETIME
"
DHCPV4D_SETTINGS="\
	${DHCPD_SETTINGS} \
	DEFAULT_LEASE_TIME \
	MAX_LEASE_TIME \
	MIN_LEASE_TIME \
"

DHCPD_SUBNET_PREFIX="subnet-"
#DHCPD_SUBNET_POOL_PREFIX="pool-"
DHCPD_SUBNET_RANGE_PREFIX="range-"

DHCPD_SUBNET_SETTINGS="ADDRESS PREFIX ROUTERS"
DHCPV6D_SUBNET_SETTINGS="${DHCPD_SUBNET_SETTINGS}"
DHCPV4D_SUBNET_SETTINGS="${DHCPD_SUBNET_SETTINGS}"

DHCPD_SUBNET_RANGE_SETTINGS="START END"
DHCPV6D_SUBNET_RANGE_SETTINGS="${DHCPD_SUBNET_RANGE_SETTINGS}"
DHCPV4D_SUBNET_RANGE_SETTINGS="${DHCPD_SUBNET_RANGE_SETTINGS}"

DHCPV6D_OPTIONS="\
	domain-search \
	name-servers \
"
DHCPV4D_OPTIONS="\
	all-subnets-local \
	arp-cache-timeout \
	bootfile-name \
	broadcast-address \
	default-ip-ttl \
	default-tcp-ttl \
	dhcp-client-identifier \
	dhcp-lease-time \
	dhcp-max-message-size \
	dhcp-rebinding-time \
	dhcp-renewal-time \
	domain-name \
	domain-name-servers \
	domain-search \
	interface-mtu \
	ntp-servers \
	root-path \
	routers \
	tftp-server-name \
"

DHCPV6D_SUBNET_OPTIONS="${DHCPV6D_OPTIONS}"
DHCPV4D_SUBNET_OPTIONS="${DHCPV4D_OPTIONS}"

# Defaults for DHCPv6.
DHCPV6D_PREFERRED_LIFETIME=""
DHCPV6D_VALID_LIFETIME="43200"		# 12h

# Defaults for DHCPv4.
DHCPV4D_AUTHORITATIVE="true"
DHCPV4D_DEFAULT_LEASE_TIME="43200"	# 12h
DHCPV4D_MAX_LEASE_TIME="86400"		# 24h
DHCPV4D_MIN_LEASE_TIME=""

dhcpd_service() {
	case "${1}" in
		ipv6)
			print "dhcpd6.service"
			;;
		ipv4)
			print "dhcpd.service"
			;;
		"")
			print "dhcpd6.service dhcp.service"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_start() {
	local services=$(dhcpd_service $@)

	local service
	for service in ${services}; do
		service_start ${service}
	done
}

dhcpd_stop() {
	local services=$(dhcpd_service $@)

	local service
	for service in ${services}; do
		service_stop ${service}
	done
}

dhcpd_restart() {
	# DHCP does not support a reload, so
	# we retsart it.
	local services=$(dhcpd_service $@)

	local service
	for service in ${services}; do
		service_restart ${service}
	done
}

dhcpd_reload() {
	dhcpd_restart $@
}

dhcpd_edit() {
	local proto=${1}
	assert isset proto
	shift

	local settings=$(dhcpd_settings ${proto})
	assert isset settings

	local ${settings}
	dhcpd_global_settings_read ${proto}

	case "${proto}" in
		ipv6)
			_dhcpd_edit_ipv6 $@ || return $?
			;;
		ipv4)
			_dhcpd_edit_ipv4 $@ || return $?
			;;
	esac

	dhcpd_global_settings_write ${proto}
}

_dhcpd_edit_ipv4() {
	local val

	while [ $# -gt 0 ]; do
		case "${1}" in
			--authoritative=*)
				val=$(cli_get_val ${1})

				if enabled val; then
					AUTHORITATIVE="true"
				else
					AUTHORITATIVE="false"
				fi
				;;
			--default-lease-time=*)
				DEFAULT_LEASE_TIME=$(cli_get_val ${1})

				if ! isinteger DEFAULT_LEASE_TIME; then
					error "Invalid value for --default-lease-time."
					return ${EXIT_ERROR}
				fi
				;;
			--max-lease-time=*)
				MAX_LEASE_TIME=$(cli_get_val ${1})

				if ! isinteger MAX_LEASE_TIME; then
					error "Invalid value for --max-lease-time."
					return ${EXIT_ERROR}
				fi
				;;
			--min-lease-time=*)
				MIN_LEASE_TIME=$(cli_get_val ${1})

				if isset MIN_LEASE_TIME; then
					if ! isinteger MIN_LEASE_TIME; then
						error "Invalid value for --min-lease-time."
						return ${EXIT_ERROR}
					fi
				fi
				;;
			*)
				error "Unrecognized argument: ${1}"
				return ${EXIT_ERROR}
				;;
		esac
		shift
	done

	if [ ${MAX_LEASE_TIME} -le ${DEFAULT_LEASE_TIME} ]; then
		error "The max. lease time must be higher than the default lease time."
		return ${EXIT_ERROR}
	fi
}

_dhcpd_edit_ipv6() {
	while [ $# -gt 0 ]; do
		case "${1}" in
			--preferred-lifetime=*)
				PREFERRED_LIFETIME=$(cli_get_val ${1})

				if ! isinteger PREFERRED_LIFETIME; then
					error "Invalid value for --preferred-lifetime."
					return ${EXIT_ERROR}
				fi
				;;
			--valid-lifetime=*)
				VALID_LIFETIME=$(cli_get_val ${1})

				if ! isinteger VALID_LIFETIME; then
					error "Invalid value for --valid-lifetime."
					return ${EXIT_ERROR}
				fi
				;;
			*)
				error "Unrecognized argument: ${1}"
				return ${EXIT_ERROR}
				;;
		esac
		shift
	done
}

dhcpd_settings_file() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_SETTINGS_FILE}"
			;;
		ipv4)
			print "${DHCPV4D_SETTINGS_FILE}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_settings() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_SETTINGS}"
			;;
		ipv4)
			print "${DHCPV4D_SETTINGS}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_options_file() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_OPTIONS_FILE}"
			;;
		ipv4)
			print "${DHCPV4D_OPTIONS_FILE}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_options_list() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "DHCPV6D_OPTIONS"
			;;
		ipv4)
			print "DHCPV4D_OPTIONS"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_options() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_OPTIONS}"
			;;
		ipv4)
			print "${DHCPV4D_OPTIONS}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_global_settings_list() {
	local proto="${1}"
	assert isset proto

	dhcpd_settings "${proto}"
}

dhcpd_global_settings_defaults() {
	local proto=${1}
	assert isset proto

	local settings=$(dhcpd_settings ${proto})
	assert isset settings

	local prefix="DHCPV${proto/ipv/}D_"

	local setting setting_default
	for setting in ${settings}; do
		setting_default="${prefix}${setting}"
		printf -v ${setting} "%s" "${!setting_default}"
	done
}

dhcpd_global_settings_read() {
	local proto=${1}
	assert isset proto

	local file=$(dhcpd_settings_file ${proto})
	assert isset file

	local settings=$(dhcpd_settings ${proto})
	assert isset settings

	dhcpd_global_settings_defaults ${proto}
	settings_read ${file} ${settings}
}

dhcpd_global_settings_write() {
	local proto=${1}
	assert isset proto

	local file=$(dhcpd_settings_file ${proto})
	assert isset file

	local settings=$(dhcpd_settings ${proto})
	assert isset settings

	settings_write ${file} ${settings}
}

dhcpd_global_options_read() {
	local proto=${1}
	assert isset proto

	local options_file=$(dhcpd_options_file ${proto})
	local options_list=$(dhcpd_options_list ${proto})

	settings_read_array ${options_file} options ${!options_list}

	# Check if domain-name is set.
	if [ -z "${options["domain-name"]}" ]; then
		options["domain-name"]=$(config_domainname)
	fi
}

dhcpd_subnet_path() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local path
	case "${proto}" in
		ipv6)
			path=${DHCPV6D_CONFIG_DIR}
			;;
		ipv4)
			path=${DHCPV4D_CONFIG_DIR}
			;;
	esac
	assert isset path

	print "${path}/${DHCPD_SUBNET_PREFIX}${subnet_id}"
	return ${EXIT_OK}
}

dhcpd_subnet_exists() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local path=$(dhcpd_subnet_path ${proto} ${subnet_id})
	assert isset path

	[ -d "${path}" ] && return ${EXIT_TRUE} || return ${EXIT_FALSE}
}

dhcpd_subnet_match() {
	local proto=${1}
	assert isset proto

	local subnet=${2}
	assert isset subnet

	local settings=$(dhcpd_subnet_settings ${proto})
	assert isset settings

	local subnet_id ${settings}
	for subnet_id in $(dhcpd_subnet_list ${proto}); do
		dhcpd_subnet_read ${proto} ${subnet_id}

		${proto}_addr_eq "${ADDRESS}/${PREFIX}" "${subnet}" \
			&& return ${EXIT_TRUE}
	done

	return ${EXIT_FALSE}
}

dhcpd_new_subnet_id() {
	local proto=${1}
	assert isset proto

	local id=1
	while :; do
		if ! dhcpd_subnet_exists ${proto} ${id}; then
			print "${id}"
			return ${EXIT_OK}
		fi

		id=$(( ${id} + 1 ))
	done

	return ${EXIT_ERROR}
}

dhcpd_subnet_new() {
	local proto=${1}
	assert isset proto
	shift

	# Allocate a new subnet id.
	local subnet_id=$(dhcpd_new_subnet_id ${proto})
	assert isinteger subnet_id

	# Create directory structure.
	local path=$(dhcpd_subnet_path ${proto} ${subnet_id})
	assert isset path

	mkdir -p ${path}
	touch ${path}/settings

	dhcpd_subnet_edit ${proto} ${subnet_id} $@
	local ret=$?

	# Remove the new subnet, when the edit method returned
	# an error.
	if [ ${ret} -ne ${EXIT_OK} ]; then
		dhcpd_subnet_remove ${proto} ${subnet_id}
	fi
}

dhcpd_subnet_edit() {
	local proto=${1}
	assert isset proto
	shift

	local id=${1}
	assert isset id
	shift

	local settings
	case "${proto}" in
		ipv6)
			settings=${DHCPV6D_SUBNET_SETTINGS}
			;;
		ipv4)
			settings=${DHCPV4D_SUBNET_SETTINGS}
			;;
	esac
	assert isset settings
	local ${settings}

	# Read current settings.
	dhcpd_subnet_read ${proto} ${id} || :

	while [ $# -gt 0 ]; do
		case "${1}" in
			--address=*)
				ADDRESS=$(cli_get_val ${1})

				local prefix=$(ip_get_prefix ${ADDRESS})
				if isset prefix; then
					PREFIX=${prefix}
					ADDRESS=$(ip_split_prefix ${ADDRESS})
				fi
				;;
			--prefix=*)
				PREFIX=$(cli_get_val ${1})
				;;
			--routers=*)
				ROUTERS=$(cli_get_val ${1})
				;;
			*)
				error "Unknown argument: ${1}"
				return ${EXIT_ERROR}
				;;
		esac
		shift
	done

	case "${proto}" in
		ipv6)
			if ! ipv6_is_valid ${ADDRESS}; then
				error "'${ADDRESS}' is not a valid IPv6 address."
				return ${EXIT_ERROR}
			fi

			if ! ipv6_prefix_is_valid ${PREFIX}; then
				error "'${PREFIX}' is not  a valid IPv6 prefix."
				return ${EXIT_ERROR}
			fi
			;;
		ipv4)
			if ! ipv4_is_valid ${ADDRESS}; then
				error "'${ADDRESS}' is not a valid IPv4 address."
				return ${EXIT_ERROR}
			fi

			if ! ipv4_prefix_is_valid ${PREFIX}; then
				error "'${PREFIX}' is not a valid IPv4 prefix."
				return ${EXIT_ERROR}
			fi
			;;
	esac

	# XXX Check for subnet collisions!

	local file="$(dhcpd_subnet_path ${proto} ${id})/settings"
	settings_write ${file} ${settings}
}

dhcpd_subnet_remove() {
	local proto=${1}
	assert isset proto

	local id=${2}
	assert isset id

	local path=$(dhcpd_subnet_path ${proto} ${id})
	assert isset path

	# Remove everything of this subnet.
	rm -rf ${path}
}

dhcpd_subnet_list() {
	local proto=${1}
	assert isset proto

	local path=$(dhcpd_subnet_path ${proto} 0)
	path=$(dirname ${path})

	# Return an error of the directory does not exist.
	[ -d "${path}" ] || return ${EXIT_ERROR}

	local p
	for p in ${path}/${DHCPD_SUBNET_PREFIX}*; do
		[ -d "${p}" ] || continue

		p=$(basename ${p})
		print "${p:${#DHCPD_SUBNET_PREFIX}}"
	done
}

dhcpd_subnet_read() {
	local proto=${1}
	assert isset proto

	local id=${2}
	assert isset id

	local file="$(dhcpd_subnet_path ${proto} ${id})/settings"
	settings_read ${file}
}

dhcpd_subnet_range_path() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isinteger subnet_id

	local range_id=${3}
	assert isinteger range_id

	print "$(dhcpd_subnet_path ${proto} ${subnet_id})/${DHCPD_SUBNET_RANGE_PREFIX}${range_id}"
	return ${EXIT_OK}
}

dhcpd_subnet_range_settings() {
	local proto=${1}

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_SUBNET_RANGE_SETTINGS}"
			;;
		ipv4)
			print "${DHCPV4D_SUBNET_RANGE_SETTINGS}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_subnet_new_range_id() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local id=1 path
	while :; do
		path=$(dhcpd_subnet_range_path ${proto} ${subnet_id} ${id})
		if [ ! -f "${path}" ]; then
			print "${id}"
			return ${EXIT_OK}
		fi

		id=$(( ${id} + 1 ))
	done

	return ${EXIT_ERROR}
}

dhcpd_subnet_range_new() {
	local proto=${1}
	assert isset proto
	shift

	local subnet_id=${1}
	assert isset subnet_id
	shift

	# Allocate a new range id.
	local range_id=$(dhcpd_subnet_new_range_id ${proto} ${subnet_id})
	assert isinteger range_id

	local path=$(dhcpd_subnet_range_path ${proto} ${subnet_id} ${range_id})
	assert isset path

	# Create file (as a placeholder).
	touch ${path}

	dhcpd_subnet_range_edit ${proto} ${subnet_id} ${range_id} $@
	local ret=$?

	if [ ${ret} -ne ${EXIT_OK} ]; then
		dhcpd_subnet_range_remove ${proto} ${subnet_id} ${range_id}
		return ${EXIT_ERROR}
	fi

	return ${EXIT_OK}
}

dhcpd_subnet_range_edit() {
	local proto=${1}
	assert isset proto
	shift

	local subnet_id=${1}
	assert isset subnet_id
	shift

	local range_id=${1}
	assert isset range_id
	shift

	local ip_encode ip_is_valid
	local settings
	case "${proto}" in
		ipv6)
			ip_encode="ipv6_encode"
			ip_is_valid="ipv6_is_valid"
			settings=${DHCPV6D_SUBNET_RANGE_SETTINGS}
			;;
		ipv4)
			ip_encode="ipv4_encode"
			ip_is_valid="ipv4_is_valid"
			settings=${DHCPV4D_SUBNET_RANGE_SETTINGS}
			;;
	esac
	assert isset settings
	local ${settings}

	while [ $# -gt 0 ]; do
		case "${1}" in
			--start=*)
				START=$(cli_get_val ${1})
				;;
			--end=*)
				END=$(cli_get_val ${1})
				;;
			*)
				error "Unknown argument: ${1}"
				return ${EXIT_ERROR}
				;;
		esac
		shift
	done

	if ! isset START; then
		error "You need to set the start of the IP range with --start=..."
		return ${EXIT_ERROR}
	fi

	if ! isset END; then
		error "You need to set the end of the IP range with --end=..."
		return ${EXIT_ERROR}
	fi

	local var
	for var in START END; do
		if ! ${ip_is_valid} ${!var}; then
			error "'${!var}' is not a valid IP address."
			return ${EXIT_ERROR}
		fi
	done

	# XXX currently, this check can only be performed for IPv4
	if [ "${proto}" = "ipv4" ]; then
		# Check if the end address is greater than the start address.
		local start_encoded=$(${ip_encode} ${START})
		local end_encoded=$(${ip_encode} ${END})

		if [ ${start_encoded} -ge ${end_encoded} ]; then
			error "The start address of the range must be greater than the end address."
			return ${EXIT_ERROR}
		fi
	fi

	# Write the configuration to file.
	local file=$(dhcpd_subnet_range_path ${proto} ${subnet_id} ${range_id})
	assert isset file

	settings_write ${file} ${settings}
}

dhcpd_subnet_range_remove() {
	local path=$(dhcpd_subnet_range_path $@)
	assert isset path

	rm -f ${path}
}

dhcpd_subnet_range_list() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local path=$(dhcpd_subnet_range_path ${proto} ${subnet_id} 0)
	path=$(dirname ${path})

	local p
	for p in ${path}/${DHCPD_SUBNET_RANGE_PREFIX}*; do
		[ -r "${p}" ] || continue

		p=$(basename ${p})
		print "${p:${#DHCPD_SUBNET_RANGE_PREFIX}}"
	done

	return ${EXIT_OK}
}

dhcpd_subnet_range_read() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local range_id=${3}
	assert isset range_id

	local file=$(dhcpd_subnet_range_path ${proto} ${subnet_id} ${range_id})
	settings_read ${file}
}

dhcpd_subnet_settings() {
	local proto=${1}

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_SUBNET_SETTINGS}"
			;;
		ipv4)
			print "${DHCPV4D_SUBNET_SETTINGS}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_subnet_options_file() {
	local path=$(dhcpd_subnet_path $@)
	assert isset path

	print "${path}/options"
}

dhcpd_subnet_options_list() {
	local proto=${1}
	assert isset proto

	case "${proto}" in
		ipv6)
			print "${DHCPV6D_SUBNET_OPTIONS}"
			;;
		ipv4)
			print "${DHCPV4D_SUBNET_OPTIONS}"
			;;
	esac

	return ${EXIT_OK}
}

dhcpd_subnet_options_read() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local options_file=$(dhcpd_subnet_options_file ${proto} ${subnet_id})
	local options_list=$(dhcpd_subnet_options_list ${proto})

	_dhcpd_read_options ${options_file} ${options_list}
}

# Helper functions to create a DHCP configuration file.
_dhcpd_write_options() {
	local proto=${1}
	assert isset proto

	local file=${2}
	assert isset file

	local options_list=${3}
	assert isset options_list

	local ident=${4}

	# Dump options array.
	local key val fmt
	for key in ${!options_list}; do
		val=${options[${key}]}

		# Prepend dhcp6 on IPv6 options.
		if [ "${proto}" = "ipv6" ]; then
			key="dhcp6.${key}"
		fi

		if isset val; then
			if isinteger val; then
				fmt="option %s %d;"
			elif isipaddress val; then
				fmt="option %s %s;"
			else
				fmt="option %s \"%s\";"
			fi
			print "${ident}${fmt}" "${key}" "${val}"
		fi
	done >> ${file}

	# Append an empty line when options have been written.
	if [ -n "${!options[@]}" ]; then
		print >> ${file}
	fi
}

_dhcpd_read_options() {
	local file=${1}
	assert isset file

	local options_list=${2}
	assert isset options_list

	settings_read_array ${file} options ${!options_list}
}

_dhcpd_write_subnet() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local file=${3}
	assert isset file

	# Check which settings we do expect.
	local settings
	case "${proto}" in
		ipv6)
			settings=${DHCPV6D_SUBNET_SETTINGS}
			;;
		ipv4)
			settings=${DHCPV4D_SUBNET_SETTINGS}
			;;
	esac
	assert isset settings
	local ${settings}

	# Read configuration settings.
	dhcpd_subnet_read ${proto} ${subnet_id}

	print "# Subnet declaration for subnet id ${subnet_id}." >> ${file}
	case "${proto}" in
		ipv6)
			print "subnet6 ${ADDRESS}/${PREFIX} {" >> ${file}
			;;
		ipv4)
			local netmask=$(ipv4_get_netmask ${ADDRESS}/${PREFIX})
			print "subnet ${ADDRESS} netmask ${netmask} {" >> ${file}
			;;
	esac

	# Add options.
	_dhcpd_write_subnet_options ${proto} ${subnet_id} ${file}

	# Add the ranges.
	local range_id
	for range_id in $(dhcpd_subnet_range_list ${proto} ${subnet_id} ${range_id}); do
		_dhcpd_write_subnet_range ${proto} ${subnet_id} ${range_id} ${file}
	done

	# End this subnet block.
	print "}\n" >> ${file}

	return ${EXIT_OK}
}

_dhcpd_write_subnet_options() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local file=${3}
	assert isset file

	local settings
	local options_file="$(dhcpd_subnet_path ${proto} ${subnet_id})/options"
	local options_list
	case "${proto}" in
		ipv6)
			settings=${DHCPV6D_SUBNET_SETTINGS}
			options_list="DHCPV6D_OPTIONS"
			;;
		ipv4)
			settings=${DHCPV4D_SUBNET_SETTINGS}
			options_list="DHCPV4D_OPTIONS"
			;;
	esac
	assert isset settings
	assert isset options_list

	local ${settings}
	dhcpd_subnet_read ${proto} ${subnet_id}

	local -A options
	_dhcpd_read_options ${options_file} ${options_list}

	# Fill in router, if not already set.
	if [ -z "${options["routers"]}" ]; then
		options["routers"]=$(_dhcpd_search_routers ${proto} "${ADDRESS}/${PREFIX}")
	fi

	_dhcpd_write_options ${proto} ${file} ${options_list} "\t"
}

_dhcpd_search_routers() {
	local proto=${1}
	assert isset proto

	# Do nothing for IPv6 (yet?).
	[ "${proto}" = "ipv6" ] && return ${EXIT_OK}

	local subnet=${2}
	assert isset subnet

	local routers

	local zone addr
	for zone in $(zones_get_all); do
		addr="$(db_get "${zone}/${proto}/local-ip-address")"
		isset addr || continue

		if ipv4_in_subnet ${addr} ${subnet}; then
			list_append routers $(ip_split_prefix ${addr})
		fi
	done

	list_join routers ", "
}

_dhcpd_write_subnet_range() {
	local proto=${1}
	assert isset proto

	local subnet_id=${2}
	assert isset subnet_id

	local range_id=${3}
	assert isset range_id

	local file=${4}
	assert isset file

	local settings=$(dhcpd_subnet_range_settings ${proto})
	assert isset settings

	# Read the configuration settings.
	local ${settings}
	dhcpd_subnet_range_read ${proto} ${subnet_id} ${range_id}

	# Print the range line.
	print "	# Range id ${range_id}." >> ${file}

	case "${proto}" in
		ipv6)
			print "	range6 ${START} ${END};" >> ${file}
			;;
		ipv4)
			print "	range ${START} ${END};" >> ${file}
			;;
	esac
	print >> ${file}

	return ${EXIT_OK}
}

dhcpd_write_config() {
	local proto=${1}
	assert isset proto

	local file options_list
	case "${proto}" in
		ipv6)
			file=${DHCPV6D_CONFIG_FILE}
			options_list="DHCPV6D_OPTIONS"
			;;
		ipv4)
			file=${DHCPV4D_CONFIG_FILE}
			options_list="DHCPV4D_OPTIONS"
			;;
	esac
	assert isset file
	assert isset options_list

	# Writing header.
	config_header "DHCP ${proto} daemon configuration file" > ${file}

	# Authoritative.
	if enabled AUTHORITATIVE; then
		(
			print "# This is an authoritative DHCP server for this network."
			print "authoritative;\n"
		) >> ${file}
	else
		(
			print "# This is NOT an authoritative DHCP server for this network."
			print "not authoritative;\n"
		) >> ${file}
	fi

	case "${proto}" in
		ipv6)
			# Lease times.
			if ininteger VALID_LIFETIME; then
				print "default-lease-time %d;" "${VALID_LIFETIME}" >> ${file}
			fi

			if isinteger PREFERRED_LIFETIME; then
				print "preferred-lifetime %d;" "${PREFERRED_LIFETIME}" >> ${file}
			fi
			;;
		ipv4)
			# Lease times.
			if isinteger DEFAULT_LEASE_TIME; then
				print "default-lease-time %d;" "${DEFAULT_LEASE_TIME}" >> ${file}
			fi

			if isinteger MAX_LEASE_TIME; then
				print "max-lease-time %d;" "${MAX_LEASE_TIME}" >> ${file}
			fi

			if isinteger MIN_LEASE_TIME; then
				print "min-lease-time %d;" "${MIN_LEASE_TIME}" >> ${file}
			fi
			;;
	esac

	# Write the options to file.
	local -A options
	dhcpd_global_options_read ${proto}
	_dhcpd_write_options ${proto} ${file} ${options_list}

	# Add all subnet declarations.
	local subnet_id
	for subnet_id in $(dhcpd_subnet_list ${proto}); do
		_dhcpd_write_subnet ${proto} ${subnet_id} ${file}
	done

	return ${EXIT_OK}
}