Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -469,18 +469,6 @@
 }
 #endif
 
-/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
-#ifdef INET6
-#define ND6_HINT(tp) \
-do { \
-	if ((tp) && (tp)->t_inpcb && \
-	    ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
-		nd6_nud_hint(NULL, NULL, 0); \
-} while (0)
-#else
-#define ND6_HINT(tp)
-#endif
-
 /*
  * Indicate whether this ack should be delayed.  We can delay the ack if
  * following conditions are met:
@@ -1763,7 +1751,6 @@
 				tp->snd_wl2 = th->th_ack;
 				tp->t_dupacks = 0;
 				m_freem(m);
-				ND6_HINT(tp); /* Some progress has been made. */
 
 				/*
 				 * If all outstanding data are acked, stop
@@ -1822,7 +1809,6 @@
 			tp->rcv_up = tp->rcv_nxt;
 			TCPSTAT_INC(tcps_rcvpack);
 			TCPSTAT_ADD(tcps_rcvbyte, tlen);
-			ND6_HINT(tp);	/* Some progress has been made */
 #ifdef TCPDEBUG
 			if (so->so_options & SO_DEBUG)
 				tcp_trace(TA_INPUT, ostate, tp,
@@ -2924,7 +2910,6 @@
 			thflags = th->th_flags & TH_FIN;
 			TCPSTAT_INC(tcps_rcvpack);
 			TCPSTAT_ADD(tcps_rcvbyte, tlen);
-			ND6_HINT(tp);
 			SOCKBUF_LOCK(&so->so_rcv);
 			if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 				m_freem(m);
Index: sys/netinet/tcp_reass.c
===================================================================
--- sys/netinet/tcp_reass.c
+++ sys/netinet/tcp_reass.c
@@ -327,7 +327,6 @@
 		tp->t_segqlen--;
 		q = nq;
 	} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
-	ND6_HINT(tp);
 	sorwakeup_locked(so);
 	return (flags);
 }
Index: sys/netinet/tcp_var.h
===================================================================
--- sys/netinet/tcp_var.h
+++ sys/netinet/tcp_var.h
@@ -83,18 +83,6 @@
 
 #define tcp6cb		tcpcb  /* for KAME src sync over BSD*'s */
 
-/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
-#ifdef INET6
-#define ND6_HINT(tp)						\
-do {								\
-	if ((tp) && (tp)->t_inpcb &&				\
-	    ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0)		\
-		nd6_nud_hint(NULL, NULL, 0);			\
-} while (0)
-#else
-#define ND6_HINT(tp)
-#endif
-
 /*
  * Tcp control block, one per tcp; fields:
  * Organized for 16 byte cacheline efficiency.
Index: sys/netinet6/nd6.h
===================================================================
--- sys/netinet6/nd6.h
+++ sys/netinet6/nd6.h
@@ -413,7 +413,6 @@
 void nd6_llinfo_settimer_locked(struct llentry *, long);
 void nd6_timer(void *);
 void nd6_purge(struct ifnet *);
-void nd6_nud_hint(struct rtentry *, struct in6_addr *, int);
 int nd6_resolve(struct ifnet *, int, struct mbuf *,
     const struct sockaddr *, u_char *, uint32_t *);
 int nd6_ioctl(u_long, caddr_t, struct ifnet *);
Index: sys/netinet6/nd6.c
===================================================================
--- sys/netinet6/nd6.c
+++ sys/netinet6/nd6.c
@@ -1282,51 +1282,6 @@
 }
 
 /*
- * Upper-layer reachability hint for Neighbor Unreachability Detection.
- *
- * XXX cost-effective methods?
- */
-void
-nd6_nud_hint(struct rtentry *rt, struct in6_addr *dst6, int force)
-{
-	struct llentry *ln;
-	struct ifnet *ifp;
-
-	if ((dst6 == NULL) || (rt == NULL))
-		return;
-
-	ifp = rt->rt_ifp;
-	IF_AFDATA_RLOCK(ifp);
-	ln = nd6_lookup(dst6, ND6_EXCLUSIVE, NULL);
-	IF_AFDATA_RUNLOCK(ifp);
-	if (ln == NULL)
-		return;
-
-	if (ln->ln_state < ND6_LLINFO_REACHABLE)
-		goto done;
-
-	/*
-	 * if we get upper-layer reachability confirmation many times,
-	 * it is possible we have false information.
-	 */
-	if (!force) {
-		ln->ln_byhint++;
-		if (ln->ln_byhint > V_nd6_maxnudhint) {
-			goto done;
-		}
-	}
-
- 	ln->ln_state = ND6_LLINFO_REACHABLE;
-	if (!ND6_LLINFO_PERMANENT(ln)) {
-		nd6_llinfo_settimer_locked(ln,
-		    (long)ND_IFINFO(rt->rt_ifp)->reachable * hz);
-	}
-done:
-	LLE_WUNLOCK(ln);
-}
-
-
-/*
  * Rejuvenate this function for routing operations related
  * processing.
  */