I've committed the change I posted earlier, minus the comment, plus
removing the cast to i6addr_t * in fil.c - it seems unnecessary and is
unsafe from a strict viewpoint.

I'll request a pullup to netbsd-4 later today unless there any
objections.


Index: sys/dist/ipf/netinet/fil.c
===================================================================
RCS file: /cvsroot/src/sys/dist/ipf/netinet/fil.c,v
retrieving revision 1.38
diff -u -p -r1.38 fil.c
--- sys/dist/ipf/netinet/fil.c	24 Jun 2007 22:16:35 -0000	1.38
+++ sys/dist/ipf/netinet/fil.c	18 Jul 2007 16:22:54 -0000
@@ -771,7 +771,7 @@ fr_info_t *fin;
 			icmp6 = fin->fin_dp;
 			ip6 = (ip6_t *)((char *)icmp6 + ICMPERR_ICMPHLEN);
 			if (IP6_NEQ(&fin->fin_fi.fi_dst,
-				    (i6addr_t *)&ip6->ip6_src))
+				    &ip6->ip6_src))
 				fin->fin_flx |= FI_BAD;
 
 			minicmpsz = ICMP6ERR_IPICMPHLEN - sizeof(ip6_t);
Index: sys/dist/ipf/netinet/ip_fil.h
===================================================================
RCS file: /cvsroot/src/sys/dist/ipf/netinet/ip_fil.h,v
retrieving revision 1.13
diff -u -p -r1.13 ip_fil.h
--- sys/dist/ipf/netinet/ip_fil.h	16 Jun 2007 10:52:27 -0000	1.13
+++ sys/dist/ipf/netinet/ip_fil.h	18 Jul 2007 16:22:54 -0000
@@ -158,14 +158,15 @@ typedef	union	i6addr	{
 #define	iplookupptr	vptr[0]
 #define	iplookupfunc	lptr[1]
 
-#define	I60(x)	(((i6addr_t *)(x))->i6[0])
-#define	I61(x)	(((i6addr_t *)(x))->i6[1])
-#define	I62(x)	(((i6addr_t *)(x))->i6[2])
-#define	I63(x)	(((i6addr_t *)(x))->i6[3])
-#define	HI60(x)	ntohl(((i6addr_t *)(x))->i6[0])
-#define	HI61(x)	ntohl(((i6addr_t *)(x))->i6[1])
-#define	HI62(x)	ntohl(((i6addr_t *)(x))->i6[2])
-#define	HI63(x)	ntohl(((i6addr_t *)(x))->i6[3])
+/* Avoid casting to a type presuming 64-bit alignment. */
+#define	I60(x)	(((u_32_t *)(x))[0])
+#define	I61(x)	(((u_32_t *)(x))[1])
+#define	I62(x)	(((u_32_t *)(x))[2])
+#define	I63(x)	(((u_32_t *)(x))[3])
+#define	HI60(x)	ntohl(((u_32_t *)(x))[0])
+#define	HI61(x)	ntohl(((u_32_t *)(x))[1])
+#define	HI62(x)	ntohl(((u_32_t *)(x))[2])
+#define	HI63(x)	ntohl(((u_32_t *)(x))[3])
 
 #define	IP6_EQ(a,b)	((I63(a) == I63(b)) && (I62(a) == I62(b)) && \
 			 (I61(a) == I61(b)) && (I60(a) == I60(b)))