Index: sys/dist/ipf/netinet/ip_fil_netbsd.c
===================================================================
RCS file: /cvsroot/src/sys/dist/ipf/netinet/ip_fil_netbsd.c,v
retrieving revision 1.55
diff -u -r1.55 ip_fil_netbsd.c
--- sys/dist/ipf/netinet/ip_fil_netbsd.c	1 Jun 2010 08:53:20 -0000	1.55
+++ sys/dist/ipf/netinet/ip_fil_netbsd.c	5 Sep 2010 12:16:04 -0000
@@ -1076,6 +1076,7 @@
 
 		hlen = sizeof(ip_t);
 		ohlen = fin->fin_hlen;
+		iclen = hlen + offsetof(struct icmp, icmp_ip) + ohlen;
 		if (fin->fin_hlen < fin->fin_plen)
 			xtra = MIN(fin->fin_dlen, 8);
 		else
@@ -1086,12 +1087,12 @@
 	else if (fin->fin_v == 6) {
 		hlen = sizeof(ip6_t);
 		ohlen = sizeof(ip6_t);
+		iclen = hlen + offsetof(struct icmp, icmp_ip) + ohlen;
 		type = icmptoicmp6types[type];
 		if (type == ICMP6_DST_UNREACH)
 			code = icmptoicmp6unreach[code];
 
-		if (hlen + sizeof(*icmp) + max_linkhdr +
-		    fin->fin_plen > avail) {
+		if (iclen + max_linkhdr + fin->fin_plen > avail) {
 			MCLGET(m, M_DONTWAIT);
 			if (m == NULL)
 				return -1;
@@ -1102,7 +1103,14 @@
 			avail = MCLBYTES;
 		}
 		xtra = MIN(fin->fin_plen,
-			   avail - hlen - sizeof(*icmp) - max_linkhdr);
+			   avail - iclen - max_linkhdr);
+		/* RFC4443 asks for 'as much of invoking packet
+		 * as possible without the ICMPv6 packet exceeding
+		 * the minimum IPv6 MTU'
+		 * fr_send_ip also drops packets larger than the
+		 * link mtu
+		 */
+		xtra = MIN(xtra, IPV6_MMTU - iclen);
 		if (dst == 0) {
 			if (fr_ifpaddr(6, FRI_NORMAL, ifp,
 				       (struct in_addr *)&dst6, NULL) == -1) {
@@ -1118,7 +1126,6 @@
 		return -1;
 	}
 
-	iclen = hlen + sizeof(*icmp);
 	avail -= (max_linkhdr + iclen);
 	if (avail < 0) {
 		FREE_MB_T(m);
@@ -1584,9 +1591,7 @@
 
 	{
 # if (__NetBSD_Version__ >= 106010000)
-#  if (__NetBSD_Version__ >= 399001400)
-		struct in6_ifextra *ife;
-#  else
+#  if (__NetBSD_Version__ < 399001400)
 		struct in6_addr finaldst = fin->fin_dst6;
 		int frag;
 #  endif
@@ -1605,8 +1610,7 @@
 		mtu = nd_ifinfo[ifp->if_index].linkmtu;
 # else
 #  if (__NetBSD_Version__ >= 399001400)
-		ife = (struct in6_ifextra *)(ifp)->if_afdata[AF_INET6];
-		mtu = ife->nd_ifinfo[ifp->if_index].linkmtu;
+		mtu = IN6_LINKMTU(ifp);
 #  else
 		error = ip6_getpmtu(ro, ro, ifp, &finaldst, &mtu, &frag);
 #  endif

.