+proto_add_ipv6_prefix() {
+ local prefix="$1"
+ local valid="$2"
+ local preferred="$3"
+
+ if [ -z "$valid" ]; then
+ append PROTO_PREFIX6 "$prefix"
+ else
+ [ -z "$preferred" ] && preferred="$valid"
+ append PROTO_PREFIX6 "$prefix,$valid,$preferred"
+ fi
+}
+