When iprouting=1, don't try to forward ipv6 packets with link-local destinations.

Reference: /n/sources/patch/applied/ipv6-dont-forward-linklocal
Date: Thu May 17 20:40:59 CES 2007
Signed-off-by: miller@hamnavoe.com

--- /sys/src/9/ip/ipv6.c	Thu May 17 20:37:22 2007
+++ /sys/src/9/ip/ipv6.c	Thu May 17 20:37:19 2007
@@ -381,6 +381,15 @@
 			freeb(bp);
 			return;
 		}
+
+		/* don't forward to link-local destinations */
+		if(islinklocal(h->dst) ||
+		   (isv6mcast(h->dst) && (h->dst[1]&0xF) <= Link_local_scop)){
+			ip->stats[OutDiscards]++;
+			freeblist(bp);
+			return;
+		}
+			
 		/* don't forward to source's network */
 		sr = v6lookup(f, h->src, nil);
 		r  = v6lookup(f, h->dst, nil);