From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: [PATCH] tcp: limit window scaling if window is clamped Date: Fri, 18 Aug 2006 10:29:38 -0700 Message-ID: <20060818102938.5abc1bcf@dxpl.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Received: from smtp.osdl.org ([65.172.181.4]:29671 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751426AbWHRR3g (ORCPT ); Fri, 18 Aug 2006 13:29:36 -0400 To: "David S. Miller" Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This small change allows for easy per-route workarounds for broken hosts or middleboxes that are not compliant with TCP standards for window scaling. Rather than having to turn off window scaling globally. This patch allows reducing or disabling window scaling if window clamp is present. Example: Mark Lord reported a problem with 2.6.17 kernel being unable to access http://www.everymac.com # ip route add 216.145.246.23/32 via 10.8.0.1 window 65535 I would argue this ought to go in stable kernel as well. Signed-off-by: Stephen Hemminger --- net-2.6.19.orig/net/ipv4/tcp_output.c +++ net-2.6.19/net/ipv4/tcp_output.c @@ -201,6 +201,7 @@ void tcp_select_initial_window(int __spa * See RFC1323 for an explanation of the limit to 14 */ space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); + space = min_t(u32, space, *window_clamp); while (space > 65535 && (*rcv_wscale) < 14) { space >>= 1; (*rcv_wscale)++;