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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 942BFC4321E for ; Thu, 16 Sep 2021 17:41:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AFC46124D for ; Thu, 16 Sep 2021 17:41:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354930AbhIPRks (ORCPT ); Thu, 16 Sep 2021 13:40:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:50270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353448AbhIPRdy (ORCPT ); Thu, 16 Sep 2021 13:33:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 840AD61882; Thu, 16 Sep 2021 16:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631810906; bh=nmZlJjMfVm8UXxDXZfpM14Y9C+so6nIKPHyHfBjxfQ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ok0sjFbccB1MfUy3D7kKjqp8Ly7ukYMpAvzoCuuxXaP9z90fVPvHgw/EdqdqIT0ei cNuopgRv7Kk+zP47F1tBScyPFqWr5rMTZ0B17j1/O2kz6/1UmmyTZF6W3rg1liC1us Kj+jGMch+47Ho07ewCwRksl4jfBcOtVmWUcC/1OQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luke Hsiao , Neal Cardwell , Yuchung Cheng , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.14 312/432] tcp: enable data-less, empty-cookie SYN with TFO_SERVER_COOKIE_NOT_REQD Date: Thu, 16 Sep 2021 18:01:01 +0200 Message-Id: <20210916155821.396157025@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210916155810.813340753@linuxfoundation.org> References: <20210916155810.813340753@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Luke Hsiao [ Upstream commit e3faa49bcecdfcc80e94dd75709d6acb1a5d89f6 ] Since the original TFO server code was implemented in commit 168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef ("tcp: TCP Fast Open Server - main code path") the TFO server code has supported the sysctl bit flag TFO_SERVER_COOKIE_NOT_REQD. Currently, when the TFO_SERVER_ENABLE and TFO_SERVER_COOKIE_NOT_REQD sysctl bit flags are set, a server connection will accept a SYN with N bytes of data (N > 0) that has no TFO cookie, create a new fast open connection, process the incoming data in the SYN, and make the connection ready for accepting. After accepting, the connection is ready for read()/recvmsg() to read the N bytes of data in the SYN, ready for write()/sendmsg() calls and data transmissions to transmit data. This commit changes an edge case in this feature by changing this behavior to apply to (N >= 0) bytes of data in the SYN rather than only (N > 0) bytes of data in the SYN. Now, a server will accept a data-less SYN without a TFO cookie if TFO_SERVER_COOKIE_NOT_REQD is set. Caveat! While this enables a new kind of TFO (data-less empty-cookie SYN), some firewall rules setup may not work if they assume such packets are not legit TFOs and will filter them. Signed-off-by: Luke Hsiao Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20210816205105.2533289-1-luke.w.hsiao@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/tcp_fastopen.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index 25fa4c01a17f..f1e90fc1cd18 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -379,8 +379,7 @@ struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb, return NULL; } - if (syn_data && - tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD)) + if (tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD)) goto fastopen; if (foc->len == 0) { -- 2.30.2