On Tue, 28 Oct 2003 08:17:59 -0800
"Kevin Lahey" [off-list ref] wrote:

It appears that tcp_ack_update_window is window scaling the offered
TCP receiver window even on the SYN packet.  As noted in no less
than two other places in the networking code, RFC 1323 insists that
initial window advertisements are unscaled.

Good spotting Kevin, thanks a lot.

I changed your patch slightly so that there is only one
expansion of ntohs().  Longer term we should make all
the include/linux/byteorder/swab.h routines inline functions
instead of macros and then mark them with __attribute__((pure)).

Thanks again Kevin.

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.1377  -> 1.1378 
#	net/ipv4/tcp_input.c	1.46    -> 1.47   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/10/28	kml@patheticgeek.net	1.1378
# [TCP]: When SYN is set, the window is not scaled.
# --------------------------------------------
#
diff -Nru a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c

--- a/net/ipv4/tcp_input.c	Tue Oct 28 08:38:22 2003
+++ b/net/ipv4/tcp_input.c	Tue Oct 28 08:38:22 2003

@@ -1967,7 +1967,10 @@
 				 struct sk_buff *skb, u32 ack, u32 ack_seq)
 {
 	int flag = 0;
-	u32 nwin = ntohs(skb->h.th->window) << tp->snd_wscale;
+	u32 nwin = ntohs(skb->h.th->window);
+
+	if (likely(!skb->h.th->syn))
+		nwin <<= tp->snd_wscale;
 
 	if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
 		flag |= FLAG_WIN_UPDATE;