Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755512AbYKUMS7 (ORCPT ); Fri, 21 Nov 2008 07:18:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753568AbYKUMSr (ORCPT ); Fri, 21 Nov 2008 07:18:47 -0500 Received: from styx.suse.cz ([82.119.242.94]:39108 "EHLO mail.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753556AbYKUMSp (ORCPT ); Fri, 21 Nov 2008 07:18:45 -0500 From: Petr Tesarik Organization: SUSE LINUX, s.r.o. To: netdev@vger.kernel.org Subject: [PATCH] Do not use TSO/GSO when there is urgent data User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: linux-kernel@vger.kernel.org, "David S. Miller" , Ilpo =?utf-8?q?J=C3=A4rvinen?= , Jan =?utf-8?q?=C5=A0embera?= MIME-Version: 1.0 Content-Disposition: inline Date: Fri, 21 Nov 2008 13:19:45 +0100 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200811211319.45515.ptesarik@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2463 Lines: 65 This patch fixes http://bugzilla.kernel.org/show_bug.cgi?id=12014 Since most (if not all) implementations of TSO and even the in-kernel software GSO do not update the urgent pointer when splitting a large segment, it is necessary to turn off TSO/GSO for all outgoing traffic with the URG pointer set. Looking at tcp_current_mss (and the preceding comment) I even think this was the original intention. However, this approach is insufficient, because TSO/GSO is turned off only for newly created frames, not for frames which were already pending at the arrival of a message with MSG_OOB set. These frames were created when TSO/GSO was enabled, so they may be large, and they will have the urgent pointer set in tcp_transmit_skb(). With this patch, such large packets will be fragmented again before going to the transmit routine. As a side note, at least the following NICs are known to screw up the urgent pointer in the TCP header when doing TSO: Intel 82566MM (PCI ID 8086:1049) Intel 82566DC (PCI ID 8086:104b) Intel 82541GI (PCI ID 8086:1076) Broadcom NetXtreme II BCM5708 (PCI ID 14e4:164c) Signed-off-by: Petr Tesarik CC: Jan Sembera CC: Ilpo Jarvinen -- tcp_output.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -722,7 +722,8 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) { - if (skb->len <= mss_now || !sk_can_gso(sk)) { + if (skb->len <= mss_now || !sk_can_gso(sk) || + tcp_urg_mode(tcp_sk(sk))) { /* Avoid the costly divide in the normal * non-TSO case. */ @@ -1163,7 +1164,9 @@ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, { int tso_segs = tcp_skb_pcount(skb); - if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { + if (!tso_segs || + (tso_segs > 1 && (tcp_skb_mss(skb) != mss_now || + tcp_urg_mode(tcp_sk(sk))))) { tcp_set_skb_tso_segs(sk, skb, mss_now); tso_segs = tcp_skb_pcount(skb); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/