#!/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/>.       #
#                                                                             #
###############################################################################

# Set this to true if localhost should be added as the first DNS server.
DNS_USE_LOCAL_RESOLVER=true
NETWORK_CONFIG_FILE_PARAMS="${NETWORK_CONFIG_FILE_PARAMS} DNS_USE_LOCAL_RESOLVER"

# Set this option to true if the DNS servers should be queried in a random order.
# This is useful to load balance between multiple servers.
DNS_RANDOMIZE=false
NETWORK_CONFIG_FILE_PARAMS="${NETWORK_CONFIG_FILE_PARAMS} DNS_RANDOMIZE"

# Set this option to true if the DNS servers should be advertised by
# radvd.
DNS_ADVERTISE_SERVERS="true"

DNS_SERVER_CONFIG_FILE="${NETWORK_CONFIG_DIR}/dns-servers"

# Path to the configuration file of the DNS resolver.
RESOLV_CONF="/etc/resolv.conf"

function dns_get_hostname() {
	local address=${1}
	assert isset address

	(
		unset HOSTNAME
		eval $(ipcalc -h ${address} 2>/dev/null)
		echo "${HOSTNAME}"
	)
}

function __dns_server_println() {
	local server=${1}
	local priority=${2}

	print "%-20s %s" "${server}" "${priority}"
}

function __dns_server_sort() {
	sort -k2 -g | uniq
}

function dns_server_list() {
	[ -r "${DNS_SERVER_CONFIG_FILE}" ] || return ${EXIT_OK}

	local server priority
	while read server priority; do
		if [ -n "${server}" ] && [ -n "${priority}" ]; then
			__dns_server_println "${server}" "${priority}"
		fi
	done < ${DNS_SERVER_CONFIG_FILE} | __dns_server_sort
}

function dns_server_list_no_priority() {
	local server priority
	dns_server_list | while read server priority; do
		echo "${server}"
	done
}

function dns_server_add() {
	local server=${1}
	assert isset server

	local priority=${2}
	if ! isset priority; then
		priority=20
	fi
	assert isinteger priority

	(
		dns_server_list
		__dns_server_println "${server}" "${priority}"
	) | __dns_server_sort > ${DNS_SERVER_CONFIG_FILE}.new

	mv ${DNS_SERVER_CONFIG_FILE}{.new,}
}

function dns_server_remove() {
	local server=${1}
	assert isset server

	local entry priority
	local entries=$(dns_server_list)

	while read entry priority; do
		[ "${entry}" = "${server}" ] && continue
		__dns_server_println "${server}" "${priority}"
	done <<< ${entries} | __dns_server_sort > ${DNS_SERVER_CONFIG_FILE}
}

function dns_server_flush() {
	: > ${DNS_SERVER_CONFIG_FILE}
}

# Update resolv.conf(5) when initializing the network.
init_register dns_generate_resolvconf

function dns_generate_resolvconf() {
	local file=${RESOLV_CONF}

	log INFO "Updating resolver configuration..."

	config_header "resolver configutation file" > ${file}

	if enabled DNS_RANDOMIZE; then
		print "option rotate\n" >> ${file}
	fi

	# XXX Add search domain.

	# Add the local resolver as the first DNS server if enabled.
	if enabled DNS_USE_LOCAL_RESOLVER; then
		print "nameserver ::1" >> ${file}
	fi

	# Dump all DNS servers (if any).
	local server priority
	dns_server_list | while read server priority; do
		print "nameserver ${server}"
	done >> ${file}
}