# Generate /etc/resolv.conf
# Support resolvconf(8) if available
# We can merge other dhcpcd resolv.conf files into one like resolvconf,
# but resolvconf is preferred as other applications like VPN clients
# can readily hook into it.
# Also, resolvconf can configure local nameservers such as bind
# or dnsmasq. This is important as the libc resolver isn't that powerful.

resolv_conf_dir="$state_dir/resolv.conf"
NL="
"
: ${resolvconf:=resolvconf}

build_resolv_conf()
{
	cf="$state_dir/resolv.conf.$ifname"

	# Build a list of interfaces
	interfaces=$(list_interfaces "$resolv_conf_dir")

	# Build the resolv.conf
	if [ -n "$interfaces" ]; then
		# Build the header
		for x in ${interfaces}; do
			header="$header${header:+, }$x"
		done

		# Build the search list
		domain=$(cd "$resolv_conf_dir"; \
			key_get_value "domain " ${interfaces})
		search=$(cd "$resolv_conf_dir"; \
			key_get_value "search " ${interfaces})
		set -- ${domain}
		domain="$1"
		[ -n "$2" ] && search="$search $*"
		[ -n "$search" ] && search="$(uniqify $search)"
		[ "$domain" = "$search" ] && search=
		[ -n "$domain" ] && domain="domain $domain$NL"
		[ -n "$search" ] && search="search $search$NL"

		# Build the nameserver list
		srvs=$(cd "$resolv_conf_dir"; \
			key_get_value "nameserver " ${interfaces})
		for x in $(uniqify ${srvs}); do
			servers="${servers}nameserver $x$NL"
		done
	fi
	header="$signature_base${header:+ $from }$header"

	# Assemble resolv.conf using our head and tail files
	[ -f "$cf" ] && rm -f "$cf"
	[ -d "$resolv_conf_dir" ] || mkdir -p "$resolv_conf_dir"
	echo "$header" > "$cf"
	if [ -f /etc/resolv.conf.head ]; then
		cat /etc/resolv.conf.head >> "$cf"
	else
		echo "# /etc/resolv.conf.head can replace this line" >> "$cf"
	fi
	printf %s "$domain$search$servers" >> "$cf"
	if [ -f /etc/resolv.conf.tail ]; then
		cat /etc/resolv.conf.tail >> "$cf"
	else
		echo "# /etc/resolv.conf.tail can replace this line" >> "$cf"
	fi
	if change_file /etc/resolv.conf "$cf"; then
		chmod 644 /etc/resolv.conf
	fi
	rm -f "$cf"
}

# Extract any ND DNS options from the RA
# For now, we ignore the lifetime of the DNS options unless they
# are absent or zero.
# In this case they are removed from consideration.
# See draft-gont-6man-slaac-dns-config-issues-01 for issues
# regarding DNS option lifetime in ND messages.
eval_nd_dns()
{
	eval ltime=\$nd${i}_rdnss${j}_lifetime
	if [ -z "$ltime" ] || [ "$ltime" = 0 ]; then
		rdnss=
	else
		eval rdnss=\$nd${i}_rdnss${j}_servers
	fi
	eval ltime=\$nd${i}_dnssl${j}_lifetime
	if [ -z "$ltime" ] || [ "$ltime" = 0 ]; then
		dnssl=
	else
		eval dnssl=\$nd${i}_dnssl${j}_search
	fi

	[ -z "${rdnss}${dnssl}" ] && return 1

	[ -n "$rdnss" ] && new_rdnss="$new_rdnss${new_rdnss:+ }$rdnss"
	[ -n "$dnssl" ] && new_dnssl="$new_dnssl${new_dnssl:+ }$dnssl"
	j=$(($j + 1))
	return 0
}

add_resolv_conf()
{
	conf="$signature$NL"
	warn=true

	# Loop to extract the ND DNS options using our indexed shell values
	i=1
	j=1
	while true; do
		while true; do
			eval_nd_dns || break
		done
		i=$(($i + 1))
		j=1
		eval_nd_dns || break
	done
	[ -n "$new_rdnss" ] && \
	    new_domain_name_servers="$new_domain_name_servers${new_domain_name_servers:+ }$new_rdnss"
	[ -n "$new_dnssl" ] && \
	    new_domain_search="$new_domain_search${new_domain_search:+ }$new_dnssl"

	# Derive a new domain from our various hostname options
	if [ -z "$new_domain_name" ]; then
		if [ "$new_dhcp6_fqdn" != "${new_dhcp6_fqdn#*.}" ]; then
			new_domain_name="${new_dhcp6_fqdn#*.}"
		elif [ "$new_fqdn" != "${new_fqdn#*.}" ]; then
			new_domain_name="${new_fqdn#*.}"
		elif [ "$new_host_name" != "${new_host_name#*.}" ]; then
			new_domain_name="${new_host_name#*.}"
		fi
	fi

	# If we don't have any configuration, remove it
	if [ -z "$new_domain_name_servers" ] &&
	   [ -z "$new_domain_name" ] &&
	   [ -z "$new_domain_search" ]; then
		remove_resolv_conf
		return $?
	fi

	if [ -n "$new_domain_name" ]; then
		set -- $new_domain_name
		if valid_domainname "$1"; then
			conf="${conf}domain $1$NL"
		else
			syslog err "Invalid domain name: $1"
		fi
		# If there is no search this, make this one
		if [ -z "$new_domain_search" ]; then
			new_domain_search="$new_domain_name"
			[ "$new_domain_name" = "$1" ] && warn=true
		fi
	fi
	if [ -n "$new_domain_search" ]; then
		if valid_domainname_list $new_domain_search; then
			conf="${conf}search $new_domain_search$NL"
		elif ! $warn; then
			syslog err "Invalid domain name in list:" \
			    "$new_domain_search"
		fi
	fi
	for x in ${new_domain_name_servers}; do
		conf="${conf}nameserver $x$NL"
	done
	if type "$resolvconf" >/dev/null 2>&1; then
		[ -n "$ifmetric" ] && export IF_METRIC="$ifmetric"
		printf %s "$conf" | "$resolvconf" -a "$ifname"
		return $?
	fi

	if [ -e "$resolv_conf_dir/$ifname" ]; then
		rm -f "$resolv_conf_dir/$ifname"
	fi
	[ -d "$resolv_conf_dir" ] || mkdir -p "$resolv_conf_dir"
	printf %s "$conf" > "$resolv_conf_dir/$ifname"
	build_resolv_conf
}

remove_resolv_conf()
{
	if type "$resolvconf" >/dev/null 2>&1; then
		"$resolvconf" -d "$ifname" -f
	else
		if [ -e "$resolv_conf_dir/$ifname" ]; then
			rm -f "$resolv_conf_dir/$ifname"
		fi
		build_resolv_conf
	fi
}

# For ease of use, map DHCP6 names onto our DHCP4 names
case "$reason" in
BOUND6|RENEW6|REBIND6|REBOOT6|INFORM6)
	new_domain_name_servers="$new_dhcp6_name_servers"
	new_domain_search="$new_dhcp6_domain_search"
	;;
esac

if $if_up || [ "$reason" = ROUTERADVERT ]; then
	add_resolv_conf
elif $if_down; then
	remove_resolv_conf
fi