#!/bin/sh
# Copyright (c) 2007-2023 Roy Marples
# All rights reserved

# dnsmasq subscriber for resolvconf

# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#     * Redistributions of source code must retain the above copyright
#       notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
#       copyright notice, this list of conditions and the following
#       disclaimer in the documentation and/or other materials provided
#       with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[ -f "@SYSCONFDIR@"/resolvconf.conf ] || exit 0
. "@SYSCONFDIR@/resolvconf.conf" || exit 1
[ -z "${dnsmasq_conf}${dnsmasq_resolv}" ] && exit 0
[ -z "$RESOLVCONF" ] && eval "$(@SBINDIR@/resolvconf -v)"
NL="
"

: ${dnsmasq_pid:=/var/run/dnsmasq.pid}
[ -s "$dnsmasq_pid" ] || dnsmasq_pid=/var/run/dnsmasq/dnsmasq.pid
[ -s "$dnsmasq_pid" ] || unset dnsmasq_pid
: ${dnsmasq_service:=dnsmasq}
newconf="# Generated by resolvconf$NL"
newresolv="$newconf"

# Using dbus means that we never have to restart the daemon
# This is important as it means we should not drop DNS queries
# whilst changing DNS options around. However, dbus support is optional
# so we need to validate a few things first.
# Check for DBus support in the binary
dbus=false
dbus_ex=false
dbus_introspect=$(dbus-send --print-reply --system \
	--dest=uk.org.thekelleys.dnsmasq \
	/uk/org/thekelleys/dnsmasq \
	org.freedesktop.DBus.Introspectable.Introspect \
	2>/dev/null)
if [ $? = 0 ]; then
	dbus=true
	if printf %s "$dbus_introspect" | \
	    grep -q '<method name="SetDomainServers">'
	then
		dbus_ex=true
	fi
fi

for n in $NAMESERVERS; do
	newresolv="${newresolv}nameserver $n$NL"
done

dbusdest=
dbusdest_ex=
conf=
for d in $DOMAINS; do
	dn="${d%%:*}"
	ns="${d#*:}"
	while [ -n "$ns" ]; do
		n="${ns%%,*}"
		if $dbus && ! $dbus_ex; then
			case "$n" in
			*.*.*.*)
				SIFS=${IFS-y} OIFS=$IFS
				IFS=.
				set -- $n
				num="0x$(printf %02x $1 $2 $3 $4)"
				if [ "$SIFS" = y ]; then
					unset IFS
				else
					IFS=$OIFS
				fi
				dbusdest="$dbusdest uint32:$(printf %u $num)"
				dbusdest="$dbusdest string:$dn"
				;;
			*:*%*)
				# This version of dnsmasq won't accept
				# scoped IPv6 addresses
				dbus=false
				;;
			*:*)
				SIFS=${IFS-y} OIFS=$IFS bytes= front= back=
				empty=false i=0
				IFS=:
				set -- $n
				while [ -n "$1" ] || [ -n "$2" ]; do
					addr="$1"
					shift
					if [ -z "$addr" ]; then
						empty=true
						continue
					fi
					i=$((i + 1))
					while [ ${#addr} -lt 4 ]; do
						addr="0${addr}"
					done
					byte1="$(printf %d 0x${addr%??})"
					byte2="$(printf %d 0x${addr#??})"
					if $empty; then
						back="$back byte:$byte1 byte:$byte2"
					else
						front="$front byte:$byte1 byte:$byte2"
					fi
				done
				while [ $i != 8 ]; do
				i=$((i + 1))
					front="$front byte:0 byte:0"
				done
				front="${front}$back"
				if [ "$SIFS" = y ]; then
					unset IFS
				else
					IFS=$OIFS
				fi
				dbusdest="${dbusdest}$front string:$dn"
				;;
			*)
				if ! $dbus_ex; then
					dbus=false
				fi
				;;
			esac
		fi
		dbusdest_ex="$dbusdest_ex${dbusdest_ex:+,}/$dn/$n"
		conf="${conf}server=/$dn/$n$NL"
		[ "$ns" = "${ns#*,}" ] && break
		ns="${ns#*,}"
	done
done

if $dbus; then
	newconf="$newconf$NL# Domain specific servers will"
	newconf="$newconf be sent over dbus${NL}"
else
	newconf="$newconf$conf"
fi

# Try to ensure that config dirs exist
if command -v config_mkdirs >/dev/null 2>&1; then
	config_mkdirs "$dnsmasq_conf" "$dnsmasq_resolv"
else
	@SBINDIR@/resolvconf -D "$dnsmasq_conf" "$dnsmasq_resolv"
fi

changed=false
if [ -n "$dnsmasq_conf" ]; then
	if [ ! -f "$dnsmasq_conf" ] || \
		[ "$(cat "$dnsmasq_conf")" != "$(printf %s "$newconf")" ]
	then
		changed=true
		printf %s "$newconf" >"$dnsmasq_conf"
	fi
fi
if [ -n "$dnsmasq_resolv" ]; then
	# dnsmasq polls this file so no need to set changed=true
	if [ -f "$dnsmasq_resolv" ]; then
		if [ "$(cat "$dnsmasq_resolv")" != "$(printf %s "$newresolv")" ]
		then
			printf %s "$newresolv" >"$dnsmasq_resolv"
		fi
	else
		printf %s "$newresolv" >"$dnsmasq_resolv"
	fi
fi

if $changed; then
	# dnsmasq does not re-read the configuration file on SIGHUP
	if [ -n "$dnsmasq_restart" ]; then
		eval $dnsmasq_restart
	elif [ -n "$RESTARTCMD" ]; then
		set -- ${dnsmasq_service}
		eval "$RESTARTCMD"
	else
		@SBINDIR@/resolvconf -r ${dnsmasq_service}
	fi
fi
if $dbus; then
	if [ -s "$dnsmasq_pid" ]; then
        	$changed || kill -HUP $(cat "$dnsmasq_pid")
	fi
	# Send even if empty so old servers are cleared
	if $dbus_ex; then
		method=SetDomainServers
		if [ -n "$dbusdest_ex" ]; then
			dbusdest_ex="array:string:$dbusdest_ex"
		fi
		dbusdest="$dbusdest_ex"
	else
		method=SetServers
	fi
	dbus-send --system --dest=uk.org.thekelleys.dnsmasq \
 		/uk/org/thekelleys/dnsmasq uk.org.thekelleys.$method \
  		$dbusdest
	dbus-send --system --dest=uk.org.thekelleys.dnsmasq \
		/uk/org/thekelleys/dnsmasq uk.org.thekelleys.ClearCache
fi