From patchwork Mon Mar 27 17:54:39 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Fastabend X-Patchwork-Id: 13189779 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2371EC761A6 for ; Mon, 27 Mar 2023 17:55:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232597AbjC0RzM (ORCPT ); Mon, 27 Mar 2023 13:55:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232480AbjC0RzA (ORCPT ); Mon, 27 Mar 2023 13:55:00 -0400 Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D43C26A2; Mon, 27 Mar 2023 10:54:58 -0700 (PDT) Received: by mail-pg1-x532.google.com with SMTP id q206so5645679pgq.9; Mon, 27 Mar 2023 10:54:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679939698; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=5HnEXOYmvzE8cKApqzizcKudiq0fvSHKWy9J37Q8ln4=; b=ZwW8SEt4LGFc6U/LUMlbh3Dqew+OucsAgxTqoklNX/CmG8nNiiS3MRuHZETlkWySL0 W8sxc0tcKhv2hkSOnEGHqtlTj1LWOg7duu2p9vhhIP3jekPmfOitjLzOOxUGU7HH67XS p91n+DmqMSgcD1EB5fLWPqCtacmyqlwJwLxqIeYM6DHEnnbovPSX9G6myZMkkAgSVaPV B7ha7s7qx2hTZWvJpjeIboGIxKElJKCsNZsSoDlf484C5aJTJi8K99nlva+Qn+0ENW4M 9ESqCK3nT6bdse1BtJPIuWdO7Zf9IeiiQv2ULMDvUFaGH77WEkpNa2VW5cJxTFbTGm0r h5NQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679939698; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=5HnEXOYmvzE8cKApqzizcKudiq0fvSHKWy9J37Q8ln4=; b=TrQdnvS5Bq6UR61wA4vjaZjUTv2RD+a+MiVH3cMbb/fWvNLXaLsVAVXeidadZWw0hc oI9TVHAihhsCl6/vhv4MX9YC5qm9r7uUyUw9P28ccuKjaPDU2ULBdvmfMUOqzuo/HhC4 1ZgDpKB/wq1uKx/l/wOWRYtt4ouTE2JOyr4bSa89EliTGZIQhRdw5ZwDPBZ45X2MnDa1 7FroQxHzZnn040cix1ITf+oo7RNZB1Xcrv2/szrEHvMksZpiV7DJVULCkY16q/7e489Q lANbG3M2yW46kIKnsfn7Gym6zfejcN9qWGc0H72z2gjD02PHufFagdFP1pFVphyi83ze GMaw== X-Gm-Message-State: AAQBX9eGKk2ISX93uZzAxhkM3XQmSJdBGoYEH4m2yzh2bbf3sAcbYxUw MURe0F4jxNavec75QIutC6Y= X-Google-Smtp-Source: AKy350Yvq/+zoWDCU6gfg33ajI/1zCReghYPGkCdyPosCclz59VsPY/GiNFraRtveOFqpFa2T9YSLQ== X-Received: by 2002:aa7:950d:0:b0:5a8:ad9d:83f with SMTP id b13-20020aa7950d000000b005a8ad9d083fmr11971485pfp.24.1679939698065; Mon, 27 Mar 2023 10:54:58 -0700 (PDT) Received: from john.lan ([98.97.117.131]) by smtp.gmail.com with ESMTPSA id r1-20020a62e401000000b005a8ba70315bsm19408316pfh.6.2023.03.27.10.54.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Mar 2023 10:54:57 -0700 (PDT) From: John Fastabend To: cong.wang@bytedance.com, jakub@cloudflare.com, daniel@iogearbox.net, lmb@isovalent.com, edumazet@google.com Cc: john.fastabend@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org, ast@kernel.org, andrii@kernel.org, will@isovalent.com Subject: [PATCH bpf v2 05/12] bpf: sockmap, TCP data stall on recv before accept Date: Mon, 27 Mar 2023 10:54:39 -0700 Message-Id: <20230327175446.98151-6-john.fastabend@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20230327175446.98151-1-john.fastabend@gmail.com> References: <20230327175446.98151-1-john.fastabend@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net A common mechanism to put a TCP socket into the sockmap is to hook the BPF_SOCK_OPS_{ACTIVE_PASSIVE}_ESTABLISHED_CB event with a BPF program that can map the socket info to the correct BPF verdict parser. When the user adds the socket to the map the psock is created and the new ops are assigned to ensure the verdict program will 'see' the sk_buffs as they arrive. Part of this process hooks the sk_data_ready op with a BPF specific handler to wake up the BPF verdict program when data is ready to read. The logic is simple enough (posted here for easy reading) static void sk_psock_verdict_data_ready(struct sock *sk) { struct socket *sock = sk->sk_socket; if (unlikely(!sock || !sock->ops || !sock->ops->read_skb)) return; sock->ops->read_skb(sk, sk_psock_verdict_recv); } The oversight here is sk->sk_socket is not assigned until the application accepts() the new socket. However, its entirely ok for the peer application to do a connect() followed immediately by sends. The socket on the receiver is sitting on the backlog queue of the listening socket until its accepted and the data is queued up. If the peer never accepts the socket or is slow it will eventually hit data limits and rate limit the session. But, important for BPF sockmap hooks when this data is received TCP stack does the sk_data_ready() call but the read_skb() for this data is never called because sk_socket is missing. The data sits on the sk_receive_queue. Then once the socket is accepted if we never receive more data from the peer there will be no further sk_data_ready calls and all the data is still on the sk_receive_queue(). Then user calls recvmsg after accept() and for TCP sockets in sockmap we use the tcp_bpf_recvmsg_parser() handler. The handler checks for data in the sk_msg ingress queue expecting that the BPF program has already run from the sk_data_ready hook and enqueued the data as needed. So we are stuck. To fix do an unlikely check in recvmsg handler for data on the sk_receive_queue and if it exists wake up data_ready. We have the sock locked in both read_skb and recvmsg so should avoid having multiple runners. Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()") Signed-off-by: John Fastabend --- net/ipv4/tcp_bpf.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 3a0f43f3afd8..2c75bbcbefed 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -209,6 +209,26 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk, return tcp_recvmsg(sk, msg, len, flags, addr_len); lock_sock(sk); + + /* We may have received data on the sk_receive_queue pre-accept and + * then we can not use read_skb in this context because we haven't + * assigned a sk_socket yet so have no link to the ops. The work-around + * is to check the sk_receive_queue and in these cases read skbs off + * queue again. The read_skb hook is not running at this point because + * of lock_sock so we avoid having multiple runners in read_skb. + */ + if (unlikely(!skb_queue_empty(&sk->sk_receive_queue))) { + tcp_data_ready(sk); + /* This handles the ENOMEM errors if we both receive data + * pre accept and are already under memory pressure. At least + * let user no to retry. + */ + if (unlikely(!skb_queue_empty(&sk->sk_receive_queue))) { + copied = -EAGAIN; + goto out; + } + } + msg_bytes_ready: copied = sk_msg_recvmsg(sk, psock, msg, len, flags); /* The typical case for EFAULT is the socket was gracefully