net/mwan3: add lock for mwan3 hotplug script

If more then one interface get up/down at once mwan3 could be in a
undefined state, because more then one mwan3 hotplug script are running
and editing the iptables.

Lock the critical section should solve this issue.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
(cherry picked from commit b6e9debc1b)

net/mwan3/files/etc/hotplug.d/iface/15-mwan3

@@ -35,6 +35,7 @@ if [ "$ACTION" == "ifup" ]; then
 	[ -n "$gateway" ] || exit 9
 fi
 
+mwan3_lock
 $LOG notice "$ACTION interface $INTERFACE (${DEVICE:-unknown})"
 
 case "$ACTION" in
@@ -58,4 +59,6 @@ case "$ACTION" in
 	;;
 esac
 
+mwan3_unlock
+
 exit 0

net/mwan3/files/lib/mwan3/mwan3.sh

@@ -7,6 +7,14 @@ IPT4="/usr/sbin/iptables -t mangle -w"
 IPT6="/usr/sbin/ip6tables -t mangle -w"
 LOG="/usr/bin/logger -t mwan3 -p"
 
+mwan3_lock() {
+	lock /var/run/mwan3.lock
+}
+
+mwan3_unlock() {
+	lock -u /var/run/mwan3.lock
+}
+
 mwan3_get_iface_id()
 {
 	local _tmp _iface _iface_count