From 98f98048bc2da13d9b65fb51ab0d5a76b27649f9 Mon Sep 17 00:00:00 2001
From: goldsimon <goldsimon@gmx.de>
Date: Fri, 28 Aug 2015 11:23:24 +0200
Subject: [PATCH] TCP window scaling: don't parse window scaling option on
 retransmission

---
 src/core/tcp_in.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index 6de74033..19671281 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -1714,10 +1714,10 @@ tcp_parseopt(struct tcp_pcb *pcb)
           return;
         }
         /* If syn was received with wnd scale option,
-           activate wnd scale opt */
-        data = tcp_getoptbyte();
-        if (flags & TCP_SYN) {
+           activate wnd scale opt, but only if this is not a retransmission */
+        if ((flags & TCP_SYN) && !(pcb->flags & TF_WND_SCALE)) {
           /* An WND_SCALE option with the right option length. */
+          data = tcp_getoptbyte();
           pcb->snd_scale = data;
           if (pcb->snd_scale > 14U) {
             pcb->snd_scale = 14U;