From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81385C43381 for ; Mon, 1 Apr 2019 17:49:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53B5020828 for ; Mon, 1 Apr 2019 17:49:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554140940; bh=nEK0d3pnvd/tvvPlby+v6yFu2EsnIgNsNQJXVbAlhKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Ssy7hb1gB2BY2+Rf02IZLMb3WlJu2htvSvNnQYJK38Rit4NZMj42RDIHq2vvGBLi7 tkw9GNgdLqvNnQBsHqZnJCSFMKCeZCIXX4F9yyz7eUvCVI8jTto6dy2FAvOLqSVSCj V0HtOtMkt8Osm10FFsjww4DzDmkibPc/84/NPlt8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733121AbfDARai (ORCPT ); Mon, 1 Apr 2019 13:30:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:37710 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732717AbfDARah (ORCPT ); Mon, 1 Apr 2019 13:30:37 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DE4002070B; Mon, 1 Apr 2019 17:30:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554139836; bh=nEK0d3pnvd/tvvPlby+v6yFu2EsnIgNsNQJXVbAlhKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sTjYyyG2ZB1n/yvtnqKgzC9fYR7z4t0Jtto4Pg2wnErB3KD3RQonT4DS7WX2Zt7XF wf6ln6S2Yzvdq8Tqq2HA/8B/m7X46S4Puri/ItQlDNWcDAFfUL69Zi7IH/gdlGmIBR imPxMJjnTqAU5ZkM9/peI79+MS6TWLIadfF3pWHw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Neal Cardwell , Yuchung Cheng , "David S. Miller" , Arnd Bergmann Subject: [PATCH 4.4 028/131] tcp/dccp: drop SYN packets if accept queue is full Date: Mon, 1 Apr 2019 19:01:38 +0200 Message-Id: <20190401170054.443690517@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190401170051.645954551@linuxfoundation.org> References: <20190401170051.645954551@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071 upstream. Per listen(fd, backlog) rules, there is really no point accepting a SYN, sending a SYNACK, and dropping the following ACK packet if accept queue is full, because application is not draining accept queue fast enough. This behavior is fooling TCP clients that believe they established a flow, while there is nothing at server side. They might then send about 10 MSS (if using IW10) that will be dropped anyway while server is under stress. Signed-off-by: Eric Dumazet Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- include/net/inet_connection_sock.h | 5 ----- net/dccp/ipv4.c | 8 +------- net/dccp/ipv6.c | 2 +- net/ipv4/tcp_input.c | 8 +------- 4 files changed, 3 insertions(+), 20 deletions(-) --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -289,11 +289,6 @@ static inline int inet_csk_reqsk_queue_l return reqsk_queue_len(&inet_csk(sk)->icsk_accept_queue); } -static inline int inet_csk_reqsk_queue_young(const struct sock *sk) -{ - return reqsk_queue_len_young(&inet_csk(sk)->icsk_accept_queue); -} - static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk) { return inet_csk_reqsk_queue_len(sk) >= sk->sk_max_ack_backlog; --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -592,13 +592,7 @@ int dccp_v4_conn_request(struct sock *sk if (inet_csk_reqsk_queue_is_full(sk)) goto drop; - /* - * Accept backlog is full. If we have already queued enough - * of warm entries in syn queue, drop request. It is better than - * clogging syn queue with openreqs with exponentially increasing - * timeout. - */ - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) + if (sk_acceptq_is_full(sk)) goto drop; req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true); --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -324,7 +324,7 @@ static int dccp_v6_conn_request(struct s if (inet_csk_reqsk_queue_is_full(sk)) goto drop; - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) + if (sk_acceptq_is_full(sk)) goto drop; req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true); --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6305,13 +6305,7 @@ int tcp_conn_request(struct request_sock goto drop; } - - /* Accept backlog is full. If we have already queued enough - * of warm entries in syn queue, drop request. It is better than - * clogging syn queue with openreqs with exponentially increasing - * timeout. - */ - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) { + if (sk_acceptq_is_full(sk)) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); goto drop; }