From patchwork Sat Nov 21 03:47:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11923153 X-Patchwork-Delegate: kuba@kernel.org 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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 58608C388F9 for ; Sat, 21 Nov 2020 03:48:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 143DE22269 for ; Sat, 21 Nov 2020 03:48:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kam1e2PW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726544AbgKUDrs (ORCPT ); Fri, 20 Nov 2020 22:47:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726485AbgKUDrs (ORCPT ); Fri, 20 Nov 2020 22:47:48 -0500 Received: from mail-qt1-x842.google.com (mail-qt1-x842.google.com [IPv6:2607:f8b0:4864:20::842]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F667C0613CF; Fri, 20 Nov 2020 19:47:48 -0800 (PST) Received: by mail-qt1-x842.google.com with SMTP id i12so8810894qtj.0; Fri, 20 Nov 2020 19:47:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:date:message-id:user-agent:mime-version :content-transfer-encoding; bh=OjtrnDz5pBQKChdFgy/uhtHZBB4JOLkyA/WpYevGjWo=; b=kam1e2PWrENckpMeGS7a0OAC3a1xolR7SDRd4z3UlWRdVPEwo2Vv+407kYhovlxWni tIjCJUO+9x63LNjdlmDVdCpEv8qZDIV2Bk/oh67fAcABWB8QJmhNSs3wgg280tA4Ks/1 qvwTIyuowJVx9pf1jmboCzzvZfNPvvtdNsywS/0IWcAJkK1ZwHjcRdltChWYt1fHSfPq gu9L+sVu5sLWq+OG0W0X6m2u6KBf/KZLCJt7aZ8FuF7OcKrkAQsRDzrHhy830nnEQBQo Vw8NcpKTEDRFSN9eGoheiSYighjZhoU0f16OA545HZLdI/XfaphMPO996/6oKSV+IDsb NwFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:date:message-id:user-agent :mime-version:content-transfer-encoding; bh=OjtrnDz5pBQKChdFgy/uhtHZBB4JOLkyA/WpYevGjWo=; b=lwHUBR+PboE+i9+jLuZr/1yTwgl00I8MrMrZhwQzXDcqapUP6TT3LvIKDVKvaqUbMN jDuzWUjiH2AQnp4J1ZOR0/1MwmmrOOEVpE6JB0xQk/N3nx2hgtGHRqi8i/seADF0V5vu ICKLubFir7poWNdujFu6E8ixKioKodoDq+rVwhEV6iXH4MCrSGLWQfAieMsHkedSH6fB K0Isol2e2yb9p5Lnv9dnJe6qjPiDZUyb+P1xa2AbALPB2qAtzC77v5iZQ+NNPVIcU55r jbCnITO+/hDnO8TDwZ+stjCaPj6ZRFqRWP7Nuoth/l2potly4ZGLJk3K0qwg5MDViaOY lBMw== X-Gm-Message-State: AOAM532ATNDZXPRzxyDs8FgtfB77n/uR8m08pMLFwB0oPcuCZ4B2+jbT C2YlYzsuNnF0RR1956VErZY= X-Google-Smtp-Source: ABdhPJw/YspS/LeeHsaXCUUAlosXVb9su95oJK+WPwnXgf6queWpcuPJiHzAtZkfWXNUB61NoW8lcw== X-Received: by 2002:ac8:5649:: with SMTP id 9mr18426812qtt.379.1605930467253; Fri, 20 Nov 2020 19:47:47 -0800 (PST) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id l22sm3507326qke.118.2020.11.20.19.47.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Nov 2020 19:47:46 -0800 (PST) Subject: [net PATCH] tcp: Set ECT0 bit in tos/tclass for synack when BPF needs ECN From: Alexander Duyck To: netdev@vger.kernel.org Cc: bpf@vger.kernel.org, daniel@iogearbox.net, kafai@fb.com, kernel-team@fb.com, edumazet@google.com, brakmo@fb.com, alexanderduyck@fb.com Date: Fri, 20 Nov 2020 19:47:44 -0800 Message-ID: <160593039663.2604.1374502006916871573.stgit@localhost.localdomain> User-Agent: StGit/0.23 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org From: Alexander Duyck When a BPF program is used to select between a type of TCP congestion control algorithm that uses either ECN or not there is a case where the synack for the frame was coming up without the ECT0 bit set. A bit of research found that this was due to the final socket being configured to dctcp while the listener socket was staying in cubic. To reproduce it all that is needed is to monitor TCP traffic while running the sample bpf program "samples/bpf/tcp_cong_kern.c". What is observed, assuming tcp_dctcp module is loaded or compiled in and the traffic matches the rules in the sample file, is that for all frames with the exception of the synack the ECT0 bit is set. To address that it is necessary to make one additional call to tcp_bpf_ca_needs_ecn using the request socket and then use the output of that to set the ECT0 bit for the tos/tclass of the packet. Fixes: 91b5b21c7c16 ("bpf: Add support for changing congestion control") Signed-off-by: Alexander Duyck --- net/ipv4/tcp_ipv4.c | 12 ++++++++---- net/ipv6/tcp_ipv6.c | 9 +++++++-- 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index c5f8b686aa82..d20d779b18f3 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -980,13 +980,17 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, skb = tcp_make_synack(sk, dst, req, foc, synack_type, syn_skb); - tos = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ? - tcp_rsk(req)->syn_tos & ~INET_ECN_MASK : - inet_sk(sk)->tos; - if (skb) { __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr); + tos = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ? + tcp_rsk(req)->syn_tos & ~INET_ECN_MASK : + inet_sk(sk)->tos; + + if (!INET_ECN_is_capable(tos) && + tcp_bpf_ca_needs_ecn((struct sock *)req)) + tos |= INET_ECN_ECT_0; + rcu_read_lock(); err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr, ireq->ir_rmt_addr, diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 3d49e8d0afee..e2b360e9bec4 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -527,11 +527,16 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst, if (np->repflow && ireq->pktopts) fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts)); - rcu_read_lock(); - opt = ireq->ipv6_opt; tclass = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ? tcp_rsk(req)->syn_tos & ~INET_ECN_MASK : np->tclass; + + if (!INET_ECN_is_capable(tclass) && + tcp_bpf_ca_needs_ecn((struct sock *)req)) + tclass |= INET_ECN_ECT_0; + + rcu_read_lock(); + opt = ireq->ipv6_opt; if (!opt) opt = rcu_dereference(np->opt); err = ip6_xmit(sk, skb, fl6, sk->sk_mark, opt,