From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Subject: Re: [PATCH] tcp_ack_update_window window scaling bug Date: Tue, 28 Oct 2003 08:35:23 -0800 Sender: netdev-bounce@oss.sgi.com Message-ID: <20031028083523.383f4b85.davem@redhat.com> References: <20031028161759.14346.qmail@patheticgeek.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@oss.sgi.com Return-path: To: "Kevin Lahey" In-Reply-To: <20031028161759.14346.qmail@patheticgeek.net> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Tue, 28 Oct 2003 08:17:59 -0800 "Kevin Lahey" 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;