#!/bin/sh
# Copyright (c) 2007-2016 Roy Marples
# All rights reserved

# 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.

RESOLVCONF="$0"
SYSCONFDIR=@SYSCONFDIR@
LIBEXECDIR=@LIBEXECDIR@
VARDIR=@VARDIR@

# Disregard dhcpcd setting
unset interface_order state_dir

# If you change this, change the test in VFLAG and libc.in as well
local_nameservers="127.* 0.0.0.0 255.255.255.255 ::1"

dynamic_order="tap[0-9]* tun[0-9]* vpn vpn[0-9]* ppp[0-9]* ippp[0-9]*"
interface_order="lo lo[0-9]*"
name_server_blacklist="0.0.0.0"

# Support original resolvconf configuration layout
# as well as the openresolv config file
if [ -f "$SYSCONFDIR"/resolvconf.conf ]; then
	. "$SYSCONFDIR"/resolvconf.conf
	[ -n "$state_dir" ] && VARDIR="$state_dir"
elif [ -d "$SYSCONFDIR/resolvconf" ]; then
	SYSCONFDIR="$SYSCONFDIR/resolvconf"
	if [ -f "$SYSCONFDIR"/interface-order ]; then
		interface_order="$(cat "$SYSCONFDIR"/interface-order)"
	fi
fi
IFACEDIR="$VARDIR/interfaces"
METRICDIR="$VARDIR/metrics"
PRIVATEDIR="$VARDIR/private"
EXCLUSIVEDIR="$VARDIR/exclusive"
LOCKDIR="$VARDIR/lock"
_PWD="$PWD"

warn()
{
	echo "$*" >&2
}

error_exit()
{
	echo "$*" >&2
	exit 1
}

usage()
{
	cat <<-EOF
	Usage: ${RESOLVCONF##*/} [options]

	Inform the system about any DNS updates.

	Options:
	  -a \$INTERFACE    Add DNS information to the specified interface
	                   (DNS supplied via stdin in resolv.conf format)
	  -m metric        Give the added DNS information a metric
	  -p               Mark the interface as private
	  -x               Mark the interface as exclusive
	  -d \$INTERFACE    Delete DNS information from the specified interface
	  -f               Ignore non existant interfaces
	  -I               Init the state dir
	  -u               Run updates from our current DNS information
	  -l [\$PATTERN]    Show DNS information, optionally from interfaces
	                   that match the specified pattern
	  -i [\$PATTERN]    Show interfaces that have supplied DNS information
                   optionally from interfaces that match the specified
                   pattern
	  -v [\$PATTERN]    echo NEWDOMAIN, NEWSEARCH and NEWNS variables to
	  		   the console
	  -h               Show this help cruft
	EOF
	[ -z "$1" ] && exit 0
	echo
	error_exit "$*"
}

echo_resolv()
{
	local line= OIFS="$IFS"

	[ -n "$1" -a -f "$IFACEDIR/$1" ] || return 1
	echo "# resolv.conf from $1"
	# Our variable maker works of the fact each resolv.conf per interface
	# is separated by blank lines.
	# So we remove them when echoing them.
	while read -r line; do
		IFS="$OIFS"
		if [ -n "$line" ]; then
			# We need to set IFS here to preserve any whitespace
			IFS=''
			printf "%s\n" "$line"
		fi
	done < "$IFACEDIR/$1"
	echo
	IFS="$OIFS"
}

# Strip any trailing dot from each name as a FQDN does not belong
# in resolv.conf(5)
# If you think otherwise, capture a DNS trace and you'll see libc
# will strip it regardless.
# This also solves setting up duplicate zones in our subscribers.
strip_trailing_dots()
{
	local n= d=

	for n; do
		printf "$d%s" "${n%.}"
		d=" "
	done
	printf "\n"
}

# Parse resolv.conf's and make variables
# for domain name servers, search name servers and global nameservers
parse_resolv()
{
	local line= ns= ds= search= d= n= newns=
	local new=true iface= private=false p= domain= l= islocal=

	newns=

	while read -r line; do
		case "$line" in
		"# resolv.conf from "*)
			if ${new}; then
				iface="${line#\# resolv.conf from *}"
				new=false
				if [ -e "$PRIVATEDIR/$iface" ]; then
					private=true
				else
					# Allow expansion
					cd "$IFACEDIR"
					private=false
					for p in $private_interfaces; do
						case "$iface" in
						"$p"|"$p":*) private=true; break;;
						esac
					done
				fi
			fi
			;;
		"nameserver "*)
			islocal=false
			for l in $local_nameservers; do
				case "${line#* }" in
				$l)
					islocal=true
					echo "LOCALNAMESERVERS=\"\$LOCALNAMESERVERS ${line#* }\""
					break
					;;
				esac
			done
			$islocal || ns="$ns${line#* } "
			;;
		"domain "*)
			search="$(strip_trailing_dots ${line#* })"
			if [ -z "$domain" ]; then
				domain="$search"
				echo "DOMAIN=\"$domain\""
			fi
			;;
		"search "*)
			search="$(strip_trailing_dots ${line#* })"
			;;
		*)
			[ -n "$line" ] && continue
			if [ -n "$ns" -a -n "$search" ]; then
				newns=
				for n in $ns; do
					newns="$newns${newns:+,}$n"
				done
				ds=
				for d in $search; do
					ds="$ds${ds:+ }$d:$newns"
				done
				echo "DOMAINS=\"\$DOMAINS $ds\""
			fi
			echo "SEARCH=\"\$SEARCH $search\""
			if ! $private; then
				echo "NAMESERVERS=\"\$NAMESERVERS $ns\""
			fi
			ns=
			search=
			new=true
			;;
		esac
	done
}

uniqify()
{
	local result=
	while [ -n "$1" ]; do
		case " $result " in
		*" $1 "*);;
		*) result="$result $1";;
		esac
		shift
	done
	echo "${result# *}"
}

dirname()
{
	local dir= OIFS="$IFS"
	local IFS=/
	set -- $@
	IFS="$OIFS"
	if [ -n "$1" ]; then
		printf %s .
	else
		shift
	fi
	while [ -n "$2" ]; do
		printf "/%s" "$1"
		shift
	done
	printf "\n"
}

config_mkdirs()
{
	local e=0 f d
	for f; do
		[ -n "$f" ] || continue
		d="$(dirname "$f")"
		if [ ! -d "$d" ]; then
			if type install >/dev/null 2>&1; then
				install -d "$d" || e=$?
			else
				mkdir "$d" || e=$?
			fi
		fi
	done
	return $e
}

list_resolv()
{
	[ -d "$IFACEDIR" ] || return 0

	local report=false list= retval=0 cmd="$1" excl=
	shift

	case "$IF_EXCLUSIVE" in
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
		if [ -d "$EXCLUSIVEDIR" ]; then
			cd "$EXCLUSIVEDIR"
			for i in *; do
				if [ -f "$i" ]; then
					list="${i#* }"
					break
				fi
			done
		fi
		excl=true
		;;
	*)
		excl=false
		;;
	esac

	# If we have an interface ordering list, then use that.
	# It works by just using pathname expansion in the interface directory.
	if [ -n "$1" ]; then
		list="$*"
		$force || report=true
	elif ! $excl; then
		cd "$IFACEDIR"
		for i in $interface_order; do
			[ -f "$i" ] && list="$list $i"
			for ii in "$i":* "$i".*; do
				[ -f "$ii" ] && list="$list $ii"
			done
		done
		for i in $dynamic_order; do
			if [ -e "$i" -a ! -e "$METRICDIR/"*" $i" ]; then
				list="$list $i"
			fi
			for ii in "$i":* "$i".*; do
				if [ -f "$ii" -a ! -e "$METRICDIR/"*" $ii" ]; then
					list="$list $ii"
				fi
			done
		done
		if [ -d "$METRICDIR" ]; then
			cd "$METRICDIR"
			for i in *; do
				[ -f "$i" ] && list="$list ${i#* }"
			done
		fi
		list="$list *"
	fi

	cd "$IFACEDIR"
	retval=1
	for i in $(uniqify $list); do
		# Only list interfaces which we really have
		if ! [ -f "$i" ]; then
			if $report; then
				echo "No resolv.conf for interface $i" >&2
				retval=2
			fi
			continue
		fi
		
		if [ "$cmd" = i -o "$cmd" = "-i" ]; then
			printf %s "$i "
		else
			echo_resolv "$i"
		fi
		[ $? = 0 -a "$retval" = 1 ] && retval=0
	done
	[ "$cmd" = i -o "$cmd" = "-i" ] && echo
	return $retval
}

list_remove() {
	local list= e= l= result= found= retval=0

	[ -z "$2" ] && return 0
	eval list=\"\$$1\"
	shift

	set -f
	for e; do
		found=false
		for l in $list; do
			case "$e" in
			$l) found=true;;
			esac
			$found && break
		done
		if $found; then
			retval=$(($retval + 1))
		else
			result="$result $e"
		fi
	done
	set +f
	echo "${result# *}"
	return $retval
}

echo_prepend()
{
	echo "# Generated by resolvconf"
	if [ -n "$search_domains" ]; then
		echo "search $search_domains"
	fi
	for n in $name_servers; do
		echo "nameserver $n"
	done
	echo
}

echo_append()
{
	echo "# Generated by resolvconf"
	if [ -n "$search_domains_append" ]; then
		echo "search $search_domains_append"
	fi
	for n in $name_servers_append; do
		echo "nameserver $n"
	done
	echo
}

replace()
{
	local r= k= f= v= val= sub=

	while read -r keyword value; do
		for r in $replace; do
			k="${r%%/*}"
			r="${r#*/}"
			f="${r%%/*}"
			r="${r#*/}"
			v="${r%%/*}"
			case "$keyword" in
			$k)
				case "$value" in
				$f) value="$v";;
				esac
				;;
			esac
		done
		val=
		for sub in $value; do
			for r in $replace_sub; do
				k="${r%%/*}"
				r="${r#*/}"
				f="${r%%/*}"
				r="${r#*/}"
				v="${r%%/*}"
				case "$keyword" in
				$k)
					case "$sub" in
					$f) sub="$v";;
					esac
					;;
				esac
			done
			val="$val${val:+ }$sub"
		done
		printf "%s %s\n" "$keyword" "$val"
	done
}

make_vars()
{
	local newdomains= d= dn= newns= ns=

	# Clear variables
	DOMAIN=
	DOMAINS=
	SEARCH=
	NAMESERVERS=
	LOCALNAMESERVERS=
	
	if [ -n "$name_servers" -o -n "$search_domains" ]; then
		eval "$(echo_prepend | parse_resolv)"
	fi
	if [ -z "$VFLAG" ]; then
		IF_EXCLUSIVE=1
		list_resolv -i "$@" >/dev/null || IF_EXCLUSIVE=0
		eval "$(list_resolv -l "$@" | replace | parse_resolv)"
	fi
	if [ -n "$name_servers_append" -o -n "$search_domains_append" ]; then
		eval "$(echo_append | parse_resolv)"
	fi

	# Ensure that we only list each domain once
	for d in $DOMAINS; do
		dn="${d%%:*}"
		list_remove domain_blacklist "$dn" >/dev/null || continue
		case " $newdomains" in
		*" ${dn}:"*) continue;;
		esac
		newns=
		for nd in $DOMAINS; do
			if [ "$dn" = "${nd%%:*}" ]; then
				ns="${nd#*:}"
				while [ -n "$ns" ]; do
					case ",$newns," in
					*,${ns%%,*},*) ;;
					*) list_remove name_server_blacklist \
						"${ns%%,*}" >/dev/null \
					&& newns="$newns${newns:+,}${ns%%,*}";;
					esac
					[ "$ns" = "${ns#*,}" ] && break
					ns="${ns#*,}"
				done
			fi
		done
		if [ -n "$newns" ]; then
			newdomains="$newdomains${newdomains:+ }$dn:$newns"
		fi
	done
	DOMAIN="$(list_remove domain_blacklist $DOMAIN)"
	SEARCH="$(uniqify $SEARCH)"
	SEARCH="$(list_remove domain_blacklist $SEARCH)"
	NAMESERVERS="$(uniqify $NAMESERVERS)"
	NAMESERVERS="$(list_remove name_server_blacklist $NAMESERVERS)"
	LOCALNAMESERVERS="$(uniqify $LOCALNAMESERVERS)"
	LOCALNAMESERVERS="$(list_remove name_server_blacklist $LOCALNAMESERVERS)"
	echo "DOMAIN='$DOMAIN'"
	echo "SEARCH='$SEARCH'"
	echo "NAMESERVERS='$NAMESERVERS'"
	echo "LOCALNAMESERVERS='$LOCALNAMESERVERS'"
	echo "DOMAINS='$newdomains'"
}

force=false
VFLAG=
while getopts a:Dd:fhIilm:puvVx OPT; do
	case "$OPT" in
	f) force=true;;
	h) usage;;
	m) IF_METRIC="$OPTARG";;
	p) IF_PRIVATE=1;;
	V)
		VFLAG=1
		if [ "$local_nameservers" = \
		    "127.* 0.0.0.0 255.255.255.255 ::1" ]
		then
			local_nameservers=
		fi
		;;
	x) IF_EXCLUSIVE=1;;
	'?') ;;
	*) cmd="$OPT"; iface="$OPTARG";;
	esac
done
shift $(($OPTIND - 1))
args="$iface${iface:+ }$*"

# -I inits the state dir
if [ "$cmd" = I ]; then
	if [ -d "$VARDIR" ]; then
		rm -rf "$VARDIR"/*
	fi
	exit $?
fi

# -D ensures that the listed config file base dirs exist
if [ "$cmd" = D ]; then
	config_mkdirs "$@"
	exit $?
fi

# -l lists our resolv files, optionally for a specific interface
if [ "$cmd" = l -o "$cmd" = i ]; then
	list_resolv "$cmd" "$args"
	exit $?
fi

# Not normally needed, but subscribers should be able to run independently
if [ "$cmd" = v -o -n "$VFLAG" ]; then
	make_vars "$iface"
	exit $?
fi

# Test that we have valid options
if [ "$cmd" = a -o "$cmd" = d ]; then
	if [ -z "$iface" ]; then
		usage "Interface not specified"
	fi
elif [ "$cmd" != u ]; then
	[ -n "$cmd" -a "$cmd" != h ] && usage "Unknown option $cmd"
	usage
fi

if [ "$cmd" = a ]; then
	for x in '/' \\ ' ' '*'; do
		case "$iface" in
		*[$x]*) error_exit "$x not allowed in interface name";;
		esac
	done
	for x in '.' '-' '~'; do
		case "$iface" in
		[$x]*) error_exit \
			"$x not allowed at start of interface name";;
		esac
	done
	[ "$cmd" = a -a -t 0 ] && error_exit "No file given via stdin"
fi

if [ ! -d "$VARDIR" ]; then
	if [ -L "$VARDIR" ]; then
		dir="$(readlink "$VARDIR")"
		# link maybe relative
		cd "${VARDIR%/*}"
		if ! mkdir -m 0755 -p "$dir"; then
			error_exit "Failed to create needed" \
				"directory $dir"
		fi
	else
		if ! mkdir -m 0755 -p "$VARDIR"; then
			error_exit "Failed to create needed" \
				"directory $VARDIR"
		fi
	fi
fi

if [ ! -d "$IFACEDIR" ]; then
	mkdir -m 0755 -p "$IFACEDIR" || \
		error_exit "Failed to create needed directory $IFACEDIR"
	if [ "$cmd" = d ]; then
		# Provide the same error messages as below
		if ! ${force}; then
			cd "$IFACEDIR"
			for i in $args; do
				warn "No resolv.conf for interface $i"
			done
		fi
		${force}
		exit $?
	fi
fi

# An interface was added, changed, deleted or a general update was called.
# Due to exclusivity we need to ensure that this is an atomic operation.
# Our subscribers *may* need this as well if the init system is sub par.
# As such we spinlock at this point as best we can.
# We don't use flock(1) because it's not widely available and normally resides
# in /usr which we do our very best to operate without.
[ -w "$VARDIR" ] || error_exit "Cannot write to $LOCKDIR"
: ${lock_timeout:=10}
while true; do
	if mkdir "$LOCKDIR" 2>/dev/null; then
		trap 'rm -rf "$LOCKDIR";' EXIT
		trap 'rm -rf "$LOCKDIR"; exit 1' INT QUIT ABRT SEGV ALRM TERM
		echo $$ >"$LOCKDIR/pid"
		break
	fi
	pid=$(cat "$LOCKDIR/pid")
	if ! kill -0 "$pid"; then
		warn "clearing stale lock pid $pid"
		rm -rf "$LOCKDIR"
		continue
	fi
	lock_timeout=$(($lock_timeout - 1))
	if [ "$lock_timeout" -le 0 ]; then
		error_exit "timed out waiting for lock from pid $pid"
	fi
	sleep 1
done

case "$cmd" in
a)
	# Read resolv.conf from stdin
	resolv="$(cat)"
	changed=false
	changedfile=false
	# If what we are given matches what we have, then do nothing
	if [ -e "$IFACEDIR/$iface" ]; then
		if [ "$(echo "$resolv")" != \
			"$(cat "$IFACEDIR/$iface")" ]
		then
			changed=true
			changedfile=true
		fi
	else
		changed=true
		changedfile=true
	fi

	# Set metric and private before creating the interface resolv.conf file
	# to ensure that it will have the correct flags
	[ ! -d "$METRICDIR" ] && mkdir "$METRICDIR"
	oldmetric="$METRICDIR/"*" $iface"
	newmetric=
	if [ -n "$IF_METRIC" ]; then
		# Pad metric to 6 characters, so 5 is less than 10
		while [ ${#IF_METRIC} -le 6 ]; do
			IF_METRIC="0$IF_METRIC"
		done
		newmetric="$METRICDIR/$IF_METRIC $iface"
	fi
	rm -f "$METRICDIR/"*" $iface"
	[ "$oldmetric" != "$newmetric" -a \
	    "$oldmetric" != "$METRICDIR/* $iface" ] &&
		changed=true
	[ -n "$newmetric" ] && echo " " >"$newmetric"

	case "$IF_PRIVATE" in
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
		if [ ! -d "$PRIVATEDIR" ]; then
			[ -e "$PRIVATEDIR" ] && rm "$PRIVATEDIR"
			mkdir "$PRIVATEDIR"
		fi
		[ -e "$PRIVATEDIR/$iface" ] || changed=true
		[ -d "$PRIVATEDIR" ] && echo " " >"$PRIVATEDIR/$iface"
		;;
	*)
		if [ -e "$PRIVATEDIR/$iface" ]; then
			rm -f "$PRIVATEDIR/$iface"
			changed=true
		fi
		;;
	esac

	oldexcl=
	for x in "$EXCLUSIVEDIR/"*" $iface"; do
		if [ -f "$x" ]; then
			oldexcl="$x"
			break
		fi
	done
	case "$IF_EXCLUSIVE" in
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
		if [ ! -d "$EXCLUSIVEDIR" ]; then
			[ -e "$EXCLUSIVEDIR" ] && rm "$EXCLUSIVEDIR"
			mkdir "$EXCLUSIVEDIR"
		fi
		cd "$EXCLUSIVEDIR"
		for x in *; do
			[ -f "$x" ] && break
		done
		if [ "${x#* }" != "$iface" ]; then
			if [ "$x" = "${x% *}" ]; then
				x=10000000
			else
				x="${x% *}"
			fi
			if [ "$x" = "0000000" ]; then
				warn "exclusive underflow"
			else
				x=$(($x - 1))
			fi
			if [ -d "$EXCLUSIVEDIR" ]; then
				echo " " >"$EXCLUSIVEDIR/$x $iface"
			fi
			changed=true
		fi
		;;
	*)
		if [ -f "$oldexcl" ]; then
			rm -f "$oldexcl"
			changed=true
		fi
		;;
	esac

	if $changedfile; then
		printf "%s\n" "$resolv" >"$IFACEDIR/$iface" || exit $?
	elif ! $changed; then
		exit 0
	fi
	unset changed changedfile oldmetric newmetric x oldexcl
	;;

d)
	# Delete any existing information about the interface
	cd "$IFACEDIR"
	changed=false
	for i in $args; do
		if [ -e "$i" ]; then
			changed=true
		elif ! ${force}; then
			warn "No resolv.conf for interface $i"
		fi
		rm -f "$i" "$METRICDIR/"*" $i" \
			"$PRIVATEDIR/$i" \
			"$EXCLUSIVEDIR/"*" $i" || exit $?
	done
	if ! ${changed}; then
		# Set the return code based on the forced flag
		${force}
		exit $?
	fi
	unset changed i
	;;
esac

case "${resolvconf:-YES}" in
[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1) ;;
*) exit 0;;
esac

eval "$(make_vars)"
export RESOLVCONF DOMAINS SEARCH NAMESERVERS LOCALNAMESERVERS
: ${list_resolv:=list_resolv -l}
retval=0

# Run scripts in the same directory resolvconf is run from
# in case any scripts accidently dump files in the wrong place.
cd "$_PWD"
for script in "$LIBEXECDIR"/*; do
	if [ -f "$script" ]; then
		eval script_enabled="\$${script##*/}"
		case "${script_enabled:-YES}" in
		[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1) ;;
		*) continue;;
		esac
		if [ -x "$script" ]; then
			"$script" "$cmd" "$iface"
		else
			(set -- "$cmd" "$iface"; . "$script")
		fi
		retval=$(($retval + $?))
	fi
done
exit $retval