xl2tp: add PPP unnumbered support to proto handler

Adds the PPP unnumbered support from openwrt commit 48a95ef ("ppp :
Unnumbered support") to the xl2tp proto handler.

openwrt/openwrt@48a95ef

Signed-off-by: Martin Schiller <[email protected]>

Author: sch-m

net/xl2tpd/files/l2tp.sh

@@ -4,10 +4,35 @@
 
 [ -n "$INCLUDE_ONLY" ] || {
 	. /lib/functions.sh
+	. /lib/functions/network.sh
 	. ../netifd-proto.sh
 	init_proto "$@"
 }
 
+proto_l2tp_select_ipaddr()
+{
+	local subnets=$1
+	local res
+	local res_mask
+
+	for subnet in $subnets; do
+		local addr="${subnet%%/*}"
+		local mask="${subnet#*/}"
+
+		if [ -n "$res_mask" -a "$mask" != 32 ]; then
+			[ "$mask" -gt "$res_mask" ] || [ "$res_mask" = 32 ] && {
+				res="$addr"
+				res_mask="$mask"
+			}
+		elif [ -z "$res_mask" ]; then
+			res="$addr"
+			res_mask="$mask"
+		fi
+	done
+
+	echo "$res"
+}
+
 proto_l2tp_init_config() {
 	proto_config_add_string "username"
 	proto_config_add_string "password"
@@ -18,6 +43,7 @@ proto_l2tp_init_config() {
 	proto_config_add_int "checkup_interval"
 	proto_config_add_string "server"
 	proto_config_add_string "hostname"
+	proto_config_add_string "unnumbered"
 	available=1
 	no_device=1
 	no_proto_task=1
@@ -60,8 +86,8 @@ proto_l2tp_setup() {
 		done
 	fi
 
-	local ipv6 keepalive username password pppd_options mtu
-	json_get_vars ipv6 keepalive username password pppd_options mtu
+	local ipv6 keepalive username password pppd_options mtu unnumbered localip
+	json_get_vars ipv6 keepalive username password pppd_options mtu unnumbered
 	[ "$ipv6" = 1 ] || ipv6=""
 
 	local interval="${keepalive##*[, ]}"
@@ -72,6 +98,18 @@ proto_l2tp_setup() {
 	ipv6="${ipv6:++ipv6}"
 	mtu="${mtu:+mtu $mtu mru $mtu}"
 
+	[ -n "$unnumbered" ] && {
+		local subnets
+		( proto_add_host_dependency "$interface" "" "$unnumbered" )
+		network_get_subnets subnets "$unnumbered"
+		localip=$(proto_l2tp_select_ipaddr "$subnets")
+		[ -n "$localip" ] || {
+			proto_block_restart "$interface"
+			return
+		}
+		localip="${localip:+$localip:}"
+	}
+
 	mkdir -p /tmp/l2tp
 	cat <<EOF >"$optfile"
 usepeerdns
@@ -88,6 +126,7 @@ $keepalive
 $username
 $ipv6
 $mtu
+$localip
 $pppd_options
 EOF