Index: head/sys/contrib/ipfilter/netinet/fil.c
===================================================================
--- head/sys/contrib/ipfilter/netinet/fil.c
+++ head/sys/contrib/ipfilter/netinet/fil.c
@@ -3422,35 +3422,21 @@
 		sum += *sp++;
 		sum += *sp++;	/* ip_dst */
 		sum += *sp++;
+		slen = fin->fin_plen - off;
+		sum += htons(slen);
 #ifdef	USE_INET6
 	} else if (IP_V(ip) == 6) {
+		mb_t *m;
+
+		m = fin->fin_m;
 		ip6 = (ip6_t *)ip;
-		hlen = sizeof(*ip6);
-		off = ((char *)fin->fin_dp - (char *)fin->fin_ip);
-		sp = (u_short *)&ip6->ip6_src;
-		sum += *sp++;	/* ip6_src */
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		/* This needs to be routing header aware. */
-		sum += *sp++;	/* ip6_dst */
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
-		sum += *sp++;
+		off = ((caddr_t)ip6 - m->m_data) + sizeof(struct ip6_hdr);
+		int len = ntohs(ip6->ip6_plen) - (off - sizeof(*ip6));
+		return(ipf_pcksum6(fin, ip6, off, len));
 	} else {
 		return 0xffff;
 	}
 #endif
-	slen = fin->fin_plen - off;
-	sum += htons(slen);
 
 	switch (l4proto)
 	{
@@ -6645,6 +6631,12 @@
 	if ((fin->fin_flx & (FI_FRAG|FI_SHORT|FI_BAD)) != 0)
 		return 1;
 
+	DT2(l4sumo, int, fin->fin_out, int, (int)fin->fin_p);
+	if (fin->fin_out == 1) {
+		fin->fin_cksum = FI_CK_SUMOK;
+		return 0;
+	}
+
 	csump = NULL;
 	hdrsum = 0;
 	dosum = 0;
@@ -6696,7 +6688,11 @@
 	}
 #endif
 	DT2(l4sums, u_short, hdrsum, u_short, sum);
+#ifdef USE_INET6
+	if (hdrsum == sum || (sum == 0 && fin->fin_p == IPPROTO_ICMPV6)) {
+#else
 	if (hdrsum == sum) {
+#endif
 		fin->fin_cksum = FI_CK_SUMOK;
 		return 0;
 	}
Index: head/sys/contrib/ipfilter/netinet/ip_fil.h
===================================================================
--- head/sys/contrib/ipfilter/netinet/ip_fil.h
+++ head/sys/contrib/ipfilter/netinet/ip_fil.h
@@ -1836,6 +1836,10 @@
 						     struct icmp *, int));
 extern	u_32_t		ipf_newisn __P((fr_info_t *));
 extern	u_int		ipf_pcksum __P((fr_info_t *, int, u_int));
+#ifdef	USE_INET6
+extern	u_int		ipf_pcksum6 __P((fr_info_t *, ip6_t *,
+						u_int32_t, u_int32_t));
+#endif
 extern	void		ipf_rule_expire __P((ipf_main_softc_t *));
 extern	int		ipf_scanlist __P((fr_info_t *, u_32_t));
 extern	frentry_t 	*ipf_srcgrpmap __P((fr_info_t *, u_32_t *));
Index: head/sys/contrib/ipfilter/netinet/ip_fil_freebsd.c
===================================================================
--- head/sys/contrib/ipfilter/netinet/ip_fil_freebsd.c
+++ head/sys/contrib/ipfilter/netinet/ip_fil_freebsd.c
@@ -1446,3 +1446,56 @@
 	sum2 = ~sum & 0xffff;
 	return sum2;
 }
+
+#ifdef  USE_INET6
+#ifdef	_KERNEL
+u_int
+ipf_pcksum6(fin, ip6, off, len)
+	fr_info_t *fin;
+	ip6_t *ip6;
+	u_int32_t off;
+	u_int32_t len;
+{
+	struct mbuf *m;
+	int sum;
+
+	m = fin->fin_m;
+	if (m->m_len < sizeof(struct ip6_hdr)) {
+		return 0xffff;
+	}
+
+	sum = in6_cksum(m, ip6->ip6_nxt, off, len);
+	return(sum);
+}
+#else
+u_int
+ipf_pcksum6(fin, ip6, off, len)
+	fr_info_t *fin;
+	ip6_t *ip6;
+	u_int32_t off;
+	u_int32_t len;
+{
+	u_short *sp;
+	u_int sum;
+
+	sp = (u_short *)&ip6->ip6_src;
+	sum = *sp++;   /* ip6_src */
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+	sum += *sp++;   /* ip6_dst */
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+        sum += *sp++;
+	return(ipf_pcksum(fin, off, sum));
+}
+#endif
+#endif