From 52f9ffcfb1a0e8fc03e584cd8ef8f66b7f71f884 Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date: Fri, 11 May 2012 10:00:18 +0800
Subject: [PATCH] tcp: Properly count duplicated ACKs

---
 sys/netinet/tcp_input.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 1ee34994ee..672b7f9e91 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1907,7 +1907,8 @@ after_listen:
 				tcp_sack_update_scoreboard(tp, &to);
 			if (!tcp_callout_active(tp, tp->tt_rexmt) ||
 			    th->th_ack != tp->snd_una) {
-				tcpstat.tcps_rcvdupack++;
+				if (tlen == 0 && tiwin == tp->snd_wnd)
+					tcpstat.tcps_rcvdupack++;
 				tp->t_dupacks = 0;
 				break;
 			}
-- 
2.41.0