From 319a972e751cec1ac95092fb138b9840bb1ac696 Mon Sep 17 00:00:00 2001
From: likewise <likewise>
Date: Wed, 14 Dec 2005 21:58:14 +0000
Subject: [PATCH] Duplicate FIN ACK race condition fix by Kelvin Lawson.

---
 src/core/tcp_in.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index ba4ebf3e..7715d9e5 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -938,7 +938,12 @@ tcp_receive(struct tcp_pcb *pcb)
 
         tcplen = TCP_TCPLEN(&inseg);
 
-        pcb->rcv_nxt += tcplen;
+        /* First received FIN will be ACKed +1, on any successive (duplicate)
+         * FINs we are already in CLOSE_WAIT and have already done +1.
+         */
+        if (pcb->state != CLOSE_WAIT) {
+          pcb->rcv_nxt += tcplen;
+        }
 
         /* Update the receiver's (our) window. */
         if (pcb->rcv_wnd < tcplen) {