we don't need ip6_id when RANDOM_IP_ID is defined.

sys/netinet6/frag6.c

@@ -89,7 +89,9 @@ frag6_init()
 	 * as initialization during bootstrap time occur in fixed order.
 	 */
 	microtime(&tv);
+#ifndef RANDOM_IP_ID
 	ip6_id = random() ^ tv.tv_usec;
+#endif
 	ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
 }
 

sys/netinet6/in6_proto.c

@@ -299,7 +299,9 @@ int	ip6_rr_prune = 5;	/* router renumbering prefix
 				 * walk list every 5 sec.    */
 int	ip6_v6only = 1;
 
+#ifndef RANDOM_IP_ID
 u_int32_t ip6_id = 0UL;
+#endif
 int	ip6_keepfaith = 0;
 time_t	ip6_log_time = (time_t)0L;
 

sys/netinet6/ip6_var.h

@@ -251,7 +251,9 @@ struct ip6aux {
 #define	IPV6_MINMTU		0x04	/* use minimum MTU (IPV6_USE_MIN_MTU) */
 
 extern struct	ip6stat ip6stat;	/* statistics */
+#ifndef RANDOM_IP_ID
 extern u_int32_t ip6_id;		/* fragment identifier */
+#endif
 extern int	ip6_defhlim;		/* default hop limit */
 extern int	ip6_defmcasthlim;	/* default multicast hop limit */
 extern int	ip6_forwarding;		/* act as router? */