From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754460AbcHUPsa (ORCPT ); Sun, 21 Aug 2016 11:48:30 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:55816 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932762AbcHUPfB (ORCPT ); Sun, 21 Aug 2016 11:35:01 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Soheil Hassas Yeganeh , "David S . Miller" , Willy Tarreau Subject: [PATCH 3.10 049/180] tcp: consider recv buf for the initial window scale Date: Sun, 21 Aug 2016 17:29:39 +0200 Message-Id: <1471793510-13022-50-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1471793510-13022-1-git-send-email-w@1wt.eu> References: <1471793510-13022-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Soheil Hassas Yeganeh commit f626300a3e776ccc9671b0dd94698fb3aa315966 upstream. tcp_select_initial_window() intends to advertise a window scaling for the maximum possible window size. To do so, it considers the maximum of net.ipv4.tcp_rmem[2] and net.core.rmem_max as the only possible upper-bounds. However, users with CAP_NET_ADMIN can use SO_RCVBUFFORCE to set the socket's receive buffer size to values larger than net.ipv4.tcp_rmem[2] and net.core.rmem_max. Thus, SO_RCVBUFFORCE is effectively ignored by tcp_select_initial_window(). To fix this, consider the maximum of net.ipv4.tcp_rmem[2], net.core.rmem_max and socket's initial buffer space. Fixes: b0573dea1fb3 ("[NET]: Introduce SO_{SND,RCV}BUFFORCE socket options") Signed-off-by: Soheil Hassas Yeganeh Suggested-by: Neal Cardwell Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Willy Tarreau --- net/ipv4/tcp_output.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 76c80b59..276b283 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -222,7 +222,8 @@ void tcp_select_initial_window(int __space, __u32 mss, /* Set window scaling on max possible window * See RFC1323 for an explanation of the limit to 14 */ - space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); + space = max_t(u32, space, sysctl_tcp_rmem[2]); + space = max_t(u32, space, sysctl_rmem_max); space = min_t(u32, space, *window_clamp); while (space > 65535 && (*rcv_wscale) < 14) { space >>= 1; -- 2.8.0.rc2.1.gbe9624a