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>

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

@@ -8,6 +8,14 @@ IPT6="ip6tables -t mangle -w"
 LOG="logger -t mwan3 -p"
 CONNTRACK_FILE="/proc/net/nf_conntrack"
 
+mwan3_lock() {
+	lock /var/run/mwan3.lock
+}
+
+mwan3_unlock() {
+	lock -u /var/run/mwan3.lock
+}
+
 mwan3_get_iface_id()
 {
 	local _tmp _iface _iface_count