-# Where src_addr and dst_addr are IP addresses in dotted decimal
-# notation or valid DNS names, and src_masklen and dst_masklen are
-# subnet masks in CIDR notation, i.e. integer values from 2 to 30
-# representing the length (in bits) of the network address. The
-# masks and the whole destination part are optional.
+# Where src_addr and dst_addr are IPv4 addresses in dotted
+# decimal notation or valid DNS names, port is a port number, and
+# src_masklen and dst_masklen are subnet masks in CIDR notation,
+# i.e. integer values from 2 to 30 representing the length
+# (in bits) of the network address. The masks and the whole
+# destination part are optional.
+#
+# If your system implements RFC 3493, then src_addr and dst_addr
+# can be IPv6 addresses delimeted by brackets, port can be a
+# number or a service name, and src_masklen and dst_masklen can
+# be a number from 0 to 128.