Index: sys/netinet6/ip6_output.c
===================================================================
--- sys/netinet6/ip6_output.c
+++ sys/netinet6/ip6_output.c
@@ -214,7 +214,7 @@
 
 int
 ip6_fragment(struct ifnet *ifp, struct mbuf *m0, int hlen, u_char nextproto,
-    int mtu)
+    int mtu, uint32_t id)
 {
 	struct mbuf *m, **mnext, *m_frgpart;
 	struct ip6_hdr *ip6, *mhip6;
@@ -222,7 +222,6 @@
 	int off;
 	int error;
 	int tlen = m0->m_pkthdr.len;
-	uint32_t id = htonl(ip6_randomid());
 
 	m = m0;
 	ip6 = mtod(m, struct ip6_hdr *);
@@ -318,6 +317,7 @@
 	int needfiblookup;
 	uint32_t fibnum;
 	struct m_tag *fwd_tag = NULL;
+	uint32_t id;
 
 	ip6 = mtod(m, struct ip6_hdr *);
 	if (ip6 == NULL) {
@@ -1010,7 +1010,8 @@
 		 * chain.
 		 */
 		m0 = m;
-		if ((error = ip6_fragment(ifp, m, hlen, nextproto, len)))
+		id = htonl(ip6_randomid());
+		if ((error = ip6_fragment(ifp, m, hlen, nextproto, len, id)))
 			goto sendorfree;
 
 		in6_ifstat_inc(ifp, ifs6_out_fragok);
Index: sys/netinet6/ip6_var.h
===================================================================
--- sys/netinet6/ip6_var.h
+++ sys/netinet6/ip6_var.h
@@ -388,7 +388,8 @@
 struct ip6_pktopts *ip6_copypktopts(struct ip6_pktopts *, int);
 int	ip6_optlen(struct inpcb *);
 int	ip6_deletefraghdr(struct mbuf *, int, int);
-int	ip6_fragment(struct ifnet *, struct mbuf *, int, u_char, int);
+int	ip6_fragment(struct ifnet *, struct mbuf *, int, u_char, int,
+			uint32_t);
 
 int	route6_input(struct mbuf **, int *, int);
 
Index: sys/netpfil/pf/pf_norm.c
===================================================================
--- sys/netpfil/pf/pf_norm.c
+++ sys/netpfil/pf/pf_norm.c
@@ -104,6 +104,7 @@
 	uint16_t	ft_hdrlen;	/* header length of reassembled pkt */
 	uint16_t	ft_extoff;	/* last extension header offset or 0 */
 	uint16_t	ft_maxlen;	/* maximum fragment payload length */
+	uint32_t	ft_id;		/* fragment id */
 };
 
 static struct mtx pf_frag_mtx;
@@ -673,6 +674,7 @@
 	struct m_tag		*mtag;
 	struct pf_fragment_tag	*ftag;
 	int			 off;
+	uint32_t		 frag_id;
 	uint16_t		 total, maxlen;
 	uint8_t			 proto;
 
@@ -715,6 +717,7 @@
 	/* We have all the data. */
 	extoff = frent->fe_extoff;
 	maxlen = frag->fr_maxlen;
+	frag_id = frag->fr_id;
 	frent = TAILQ_FIRST(&frag->fr_queue);
 	KASSERT(frent != NULL, ("frent != NULL"));
 	total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
@@ -751,6 +754,7 @@
 	ftag->ft_hdrlen = hdrlen;
 	ftag->ft_extoff = extoff;
 	ftag->ft_maxlen = maxlen;
+	ftag->ft_id = frag_id;
 	m_tag_prepend(m, mtag);
 
 	ip6 = mtod(m, struct ip6_hdr *);
@@ -1094,6 +1098,7 @@
 	struct mbuf		*m = *m0, *t;
 	struct pf_fragment_tag	*ftag = (struct pf_fragment_tag *)(mtag + 1);
 	struct pf_pdesc		 pd;
+	uint32_t		 frag_id;
 	uint16_t		 hdrlen, extoff, maxlen;
 	uint8_t			 proto;
 	int			 error, action;
@@ -1101,6 +1106,7 @@
 	hdrlen = ftag->ft_hdrlen;
 	extoff = ftag->ft_extoff;
 	maxlen = ftag->ft_maxlen;
+	frag_id = ftag->ft_id;
 	m_tag_delete(m, mtag);
 	mtag = NULL;
 	ftag = NULL;
@@ -1130,7 +1136,7 @@
 	 * is less than 8, ip6_fragment() will return EMSGSIZE and
 	 * we drop the packet.
 	 */
-	error = ip6_fragment(ifp, m, hdrlen, proto, maxlen);
+	error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
 	m = (*m0)->m_nextpkt;
 	(*m0)->m_nextpkt = NULL;
 	if (error == 0) {