From 197ff3ac2f4fe9be7eefc9c8409cee04e267b04a Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Wed, 22 May 2019 22:20:31 +0200
Subject: [PATCH] devip: if the server does not support TCP ws option, disable
 window scaling (thanks joe9)

if the server responds without a window scale option in
its syn-ack, disable window scaling alltogether as both
sides need to understand the option.
---
 sys/src/9/ip/tcp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sys/src/9/ip/tcp.c b/sys/src/9/ip/tcp.c
index 775d1b1ce..8d0195ac3 100644
--- a/sys/src/9/ip/tcp.c
+++ b/sys/src/9/ip/tcp.c
@@ -3031,6 +3031,12 @@ procsyn(Conv *s, Tcp *seg)
 		tpriv->stats[Mss] = tcb->mss;
 	}
 
+	/* if the server does not support ws option, disable window scaling */
+	if(seg->ws == 0){
+		tcb->scale = 0;
+		tcb->snd.scale = 0;
+	}
+
 	tcb->snd.wnd = seg->wnd;
 	initialwindow(tcb);
 }