diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index c3109c77eb0b..c21e1feb960f 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -1192,7 +1192,7 @@ tcp6_ctlinput(cmd, sa, d)
 
 		in6_pcbnotify(&tcb, sa, th.th_dport,
 		    (struct sockaddr *)ip6cp->ip6c_src,
-		    th.th_sport, cmd, notify);
+		    th.th_sport, cmd, NULL, notify);
 
 		inc.inc_fport = th.th_dport;
 		inc.inc_lport = th.th_sport;
@@ -1202,7 +1202,7 @@ tcp6_ctlinput(cmd, sa, d)
 		syncache_unreach(&inc, &th);
 	} else
 		in6_pcbnotify(&tcb, sa, 0, (const struct sockaddr *)sa6_src,
-			      0, cmd, notify);
+			      0, cmd, NULL, notify);
 }
 #endif /* INET6 */
 
diff --git a/sys/netinet/tcp_timewait.c b/sys/netinet/tcp_timewait.c
index c3109c77eb0b..c21e1feb960f 100644
--- a/sys/netinet/tcp_timewait.c
+++ b/sys/netinet/tcp_timewait.c
@@ -1192,7 +1192,7 @@ tcp6_ctlinput(cmd, sa, d)
 
 		in6_pcbnotify(&tcb, sa, th.th_dport,
 		    (struct sockaddr *)ip6cp->ip6c_src,
-		    th.th_sport, cmd, notify);
+		    th.th_sport, cmd, NULL, notify);
 
 		inc.inc_fport = th.th_dport;
 		inc.inc_lport = th.th_sport;
@@ -1202,7 +1202,7 @@ tcp6_ctlinput(cmd, sa, d)
 		syncache_unreach(&inc, &th);
 	} else
 		in6_pcbnotify(&tcb, sa, 0, (const struct sockaddr *)sa6_src,
-			      0, cmd, notify);
+			      0, cmd, NULL, notify);
 }
 #endif /* INET6 */
 
diff --git a/sys/netinet6/in6_pcb.c b/sys/netinet6/in6_pcb.c
index a19a1ebc835e..1c7278cf2399 100644
--- a/sys/netinet6/in6_pcb.c
+++ b/sys/netinet6/in6_pcb.c
@@ -610,12 +610,13 @@ in6_mapped_peeraddr(struct socket *so, struct sockaddr **nam)
  * Must be called at splnet.
  */
 void
-in6_pcbnotify(head, dst, fport_arg, src, lport_arg, cmd, notify)
+in6_pcbnotify(head, dst, fport_arg, src, lport_arg, cmd, cmdarg, notify)
 	struct inpcbhead *head;
 	struct sockaddr *dst;
 	const struct sockaddr *src;
 	u_int fport_arg, lport_arg;
 	int cmd;
+	void *cmdarg;
 	struct inpcb *(*notify) __P((struct inpcb *, int));
 {
 	struct inpcb *inp, *ninp;
@@ -661,6 +662,22 @@ in6_pcbnotify(head, dst, fport_arg, src, lport_arg, cmd, notify)
  		if ((inp->inp_vflag & INP_IPV6) == 0)
 			continue;
 
+		/*
+		 * If the error designates a new path MTU for a destination
+		 * and the application (associated with this socket) wanted to
+		 * know the value, notify. Note that we notify for all
+		 * disconnected sockets if the corresponding application
+		 * wanted. This is because some UDP applications keep sending
+		 * sockets disconnected.
+		 * XXX: should we avoid to notify the value to TCP sockets?
+		 */
+		if (cmd == PRC_MSGSIZE && (inp->inp_flags & IN6P_MTU) != 0 &&
+		    (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) ||
+		     IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &sa6_dst->sin6_addr))) {
+			ip6_notify_pmtu(inp, (struct sockaddr_in6 *)dst,
+					(u_int32_t *)cmdarg);
+		}
+
 		/*
 		 * Detect if we should notify the error. If no source and
 		 * destination ports are specifed, but non-zero flowinfo and
diff --git a/sys/netinet6/in6_pcb.h b/sys/netinet6/in6_pcb.h
index cbe67c79081d..6cae30bef579 100644
--- a/sys/netinet6/in6_pcb.h
+++ b/sys/netinet6/in6_pcb.h
@@ -91,7 +91,7 @@ struct	inpcb *
 				struct in6_addr *, u_int, struct in6_addr *,
 				u_int, int, struct ifnet *));
 void	in6_pcbnotify __P((struct inpcbhead *, struct sockaddr *,
-			   u_int, const struct sockaddr *, u_int, int,
+			   u_int, const struct sockaddr *, u_int, int, void *,
 			   struct inpcb *(*)(struct inpcb *, int)));
 struct inpcb *
 	in6_rtchange __P((struct inpcb *, int));
diff --git a/sys/netinet6/ip6_input.c b/sys/netinet6/ip6_input.c
index 07156064a14c..d42a444759a3 100644
--- a/sys/netinet6/ip6_input.c
+++ b/sys/netinet6/ip6_input.c
@@ -1307,6 +1307,45 @@ ip6_savecontrol(in6p, m, mp)
 #undef IS2292
 }
 
+void
+ip6_notify_pmtu(in6p, dst, mtu)
+	struct inpcb *in6p;
+	struct sockaddr_in6 *dst;
+	u_int32_t *mtu;
+{
+	struct socket *so;
+	struct mbuf *m_mtu;
+	struct ip6_mtuinfo mtuctl;
+
+	so =  in6p->inp_socket;
+
+	if (mtu == NULL)
+		return;
+
+#ifdef DIAGNOSTIC
+	if (so == NULL)		/* I believe this is impossible */
+		panic("ip6_notify_pmtu: socket is NULL");
+#endif
+
+	bzero(&mtuctl, sizeof(mtuctl));	/* zero-clear for safety */
+	mtuctl.ip6m_mtu = *mtu;
+	mtuctl.ip6m_addr = *dst;
+	in6_recoverscope(&mtuctl.ip6m_addr, &mtuctl.ip6m_addr.sin6_addr, NULL);
+
+	if ((m_mtu = sbcreatecontrol((caddr_t)&mtuctl, sizeof(mtuctl),
+	    IPV6_PATHMTU, IPPROTO_IPV6)) == NULL)
+		return;
+
+	if (sbappendaddr(&so->so_rcv, (struct sockaddr *)dst, NULL, m_mtu)
+	    == 0) {
+		m_freem(m_mtu);
+		/* XXX: should count statistics */
+	} else
+		sorwakeup(so);
+
+	return;
+}
+
 #ifdef PULLDOWN_TEST
 /*
  * pull single extension header from mbuf chain.  returns single mbuf that
diff --git a/sys/netinet6/raw_ip6.c b/sys/netinet6/raw_ip6.c
index 56f37585e5db..00205ff01c65 100644
--- a/sys/netinet6/raw_ip6.c
+++ b/sys/netinet6/raw_ip6.c
@@ -278,6 +278,7 @@ rip6_ctlinput(cmd, sa, d)
 	int off = 0;
 	struct ip6ctlparam *ip6cp = NULL;
 	const struct sockaddr_in6 *sa6_src = NULL;
+	void *cmdarg;
 	struct inpcb *(*notify) __P((struct inpcb *, int)) = in6_rtchange;
 
 	if (sa->sa_family != AF_INET6 ||
@@ -299,15 +300,17 @@ rip6_ctlinput(cmd, sa, d)
 		m = ip6cp->ip6c_m;
 		ip6 = ip6cp->ip6c_ip6;
 		off = ip6cp->ip6c_off;
+		cmdarg = ip6cp->ip6c_cmdarg;
 		sa6_src = ip6cp->ip6c_src;
 	} else {
 		m = NULL;
 		ip6 = NULL;
+		cmdarg = NULL;
 		sa6_src = &sa6_any;
 	}
 
 	(void) in6_pcbnotify(&ripcb, sa, 0, (const struct sockaddr *)sa6_src,
-			     0, cmd, notify);
+			     0, cmd, cmdarg, notify);
 }
 
 /*
diff --git a/sys/netinet6/udp6_usrreq.c b/sys/netinet6/udp6_usrreq.c
index deb2a3159817..d95fc2696c1b 100644
--- a/sys/netinet6/udp6_usrreq.c
+++ b/sys/netinet6/udp6_usrreq.c
@@ -435,6 +435,7 @@ udp6_ctlinput(cmd, sa, d)
 	int off = 0;
 	struct ip6ctlparam *ip6cp = NULL;
 	const struct sockaddr_in6 *sa6_src = NULL;
+	void *cmdarg;
 	struct inpcb *(*notify) __P((struct inpcb *, int)) = udp_notify;
 	struct udp_portonly {
 		u_int16_t uh_sport;
@@ -460,10 +461,12 @@ udp6_ctlinput(cmd, sa, d)
 		m = ip6cp->ip6c_m;
 		ip6 = ip6cp->ip6c_ip6;
 		off = ip6cp->ip6c_off;
+		cmdarg = ip6cp->ip6c_cmdarg;
 		sa6_src = ip6cp->ip6c_src;
 	} else {
 		m = NULL;
 		ip6 = NULL;
+		cmdarg = NULL;
 		sa6_src = &sa6_any;
 	}
 
@@ -481,12 +484,12 @@ udp6_ctlinput(cmd, sa, d)
 		m_copydata(m, off, sizeof(*uhp), (caddr_t)&uh);
 
 		(void) in6_pcbnotify(&udb, sa, uh.uh_dport,
-				     (struct sockaddr *)ip6cp->ip6c_src, 
-				     uh.uh_sport, cmd, notify);
+				     (struct sockaddr *)ip6cp->ip6c_src,
+				     uh.uh_sport, cmd, cmdarg, notify);
 	} else
 		(void) in6_pcbnotify(&udb, sa, 0,
 				     (const struct sockaddr *)sa6_src,
-				     0, cmd, notify);
+				     0, cmd, cmdarg, notify);
 }
 
 static int