isc-dhcp: add support for RFC-3442 classless IPv4 routes

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

net/isc-dhcp/Makefile

@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=isc-dhcp
 UPSTREAM_NAME:=dhcp
 PKG_VERSION:=4.4.1
-PKG_RELEASE:=7
+PKG_RELEASE:=8
 
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE

net/isc-dhcp/files/dhcpd.init

@@ -131,6 +131,36 @@ typeof() {
 '
 }
 
+explode() {
+	local arg="$1"
+
+	echo "$arg" | sed -e 's/\./, /g'
+}
+
+append_routes() {
+	local tuple tuples="$1"
+	local string=
+
+	local IFS=','
+	for tuple in $tuples; do
+		local network prefix router save octets compacted
+
+		save="${tuple% *}"
+		router="${tuple#${save} }"
+
+		network="${save%/[0-9]*}"
+		prefix="${save##${network}}"
+		prefix="${prefix:1}"
+
+		octets=$((($prefix + 7) / 8))
+		compacted="$(echo "$network" | cut -d. -f1-$octets)"
+
+		string="${string:+, }$(explode "$prefix.$compacted.$router")"
+	done
+
+	echo " option classless-ipv4-route $string;"
+}
+
 append_dhcp_options() {
 	local tuple="$1"
 
@@ -178,6 +208,7 @@ gen_dhcp_subnet() {
 	fi
 	echo " option routers $gateway;"
 	echo " option domain-name-servers $DNS;"
+	config_list_foreach "$cfg" "routes" append_routes
 	config_list_foreach "$cfg" "dhcp_option" append_dhcp_options
 	echo "}"
 }
@@ -264,6 +295,8 @@ general_config() {
 
 	[ -n "$domain" ] && echo "option domain-name \"$domain\";"
 
+	echo -e "\n# additional codes\noption classless-ipv4-route code 121 = array of { unsigned integer 8 };\n"
+
 	rm -f /tmp/resolv.conf
 	echo "# This file is generated by the DHCPD service" > /tmp/resolv.conf
 	[ -n "$domain" ] && echo "domain $domain" >> /tmp/resolv.conf