Assert ip6_forward_rt protected by Giant adding GIANT_REQUIRED to

functions not yet asserting it but working on global ip6_forward_rt
route cache which is not locked and perhaps should go away in the
future though cache hit/miss ration wasn't bad.

It's #if 0ed in frag6 because the code working on ip6_forward_rt is.

sys/netinet6/frag6.c

@@ -688,6 +688,10 @@ frag6_slowtimo()
 {
 	struct ip6q *q6;
 
+#if 0
+	GIANT_REQUIRED;	/* XXX bz: ip6_forward_rt */
+#endif
+
 	IP6Q_LOCK();
 	q6 = ip6q.ip6q_next;
 	if (q6)

sys/netinet6/ip6_forward.c

@@ -120,6 +120,8 @@ ip6_forward(m, srcrt)
 	int ipsecrt = 0;
 #endif
 
+	GIANT_REQUIRED; /* XXX bz: ip6_forward_rt */
+
 #ifdef IPSEC
 	/*
 	 * Check AH/ESP integrity.