interfaces: in SLAAC tracking prevent footshooting

src/etc/inc/interfaces.inc

@@ -2868,6 +2868,10 @@ if [ -z "\${1}" ]; then
     echo "Nothing to do."
     exit 0
 fi
+if grep -q "^interface \${1} " /var/etc/radvd.conf; then
+       echo "Rejecting own configuration."
+       exit 0
+fi
 if [ -n "\${2}" ]; then
     # Note that the router file can be written by ppp-linkup.sh or
     # this script so do not clear the file as it may already exist.

src/opnsense/scripts/interfaces/rtsold_resolvconf.sh

@@ -40,6 +40,11 @@ ifname=${2%%:[*}
 rasrca=${2##*:[}
 rasrca=${rasrca%]}
 
+if grep -q "^interface ${ifname%%:slaac} " /var/etc/radvd.conf; then
+	echo "Rejecting own configuration."
+	exit 0
+fi
+
 # ${1} indicates whether DNS information should be added or deleted.
 
 if [ "${1}" = "-a" ]; then