Index: tcp_subr.c
===================================================================
--- tcp_subr.c
+++ tcp_subr.c
@@ -1677,6 +1677,7 @@
 {
 	struct tcpcb *tp;
 	struct socket *so;
+	u_int oldmaxseg;
 
 	INP_WLOCK_ASSERT(inp);
 	if ((inp->inp_flags & INP_TIMEWAIT) ||
@@ -1686,6 +1687,7 @@
 	tp = intotcpcb(inp);
 	KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
 
+	oldmaxseg = tp->t_maxseg;
 	tcp_mss_update(tp, -1, mtuoffer, NULL, NULL);
   
 	so = inp->inp_socket;
@@ -1694,6 +1696,11 @@
 	if (so->so_snd.sb_hiwat < tp->t_maxseg)
 		tp->t_maxseg = so->so_snd.sb_hiwat;
 	SOCKBUF_UNLOCK(&so->so_snd);
+	
+	if (tp->t_maxseg >= oldmaxseg) {
+		//TCPSTAT_INC(tcps_mtuignore);
+		return (inp);
+	}
 
 	TCPSTAT_INC(tcps_mturesent);
 	tp->t_rtttime = 0;