Index: head/sys/net/ethernet.h
===================================================================
--- head/sys/net/ethernet.h
+++ head/sys/net/ethernet.h
@@ -71,6 +71,8 @@
 } __packed;
 
 #define	ETHER_IS_MULTICAST(addr) (*(addr) & 0x01) /* is address mcast/bcast? */
+#define	ETHER_IS_IPV6_MULTICAST(addr) \
+	(((addr)[0] == 0x33) && ((addr)[1] == 0x33))
 #define	ETHER_IS_BROADCAST(addr) \
 	(((addr)[0] & (addr)[1] & (addr)[2] & \
 	  (addr)[3] & (addr)[4] & (addr)[5]) == 0xff)