From patchwork Tue Nov 16 03:30:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Lu X-Patchwork-Id: 12621265 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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8BC27C433FE for ; Tue, 16 Nov 2021 03:31:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 73C7C61B66 for ; Tue, 16 Nov 2021 03:31:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346957AbhKPDey (ORCPT ); Mon, 15 Nov 2021 22:34:54 -0500 Received: from out30-54.freemail.mail.aliyun.com ([115.124.30.54]:48912 "EHLO out30-54.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347205AbhKPDd7 (ORCPT ); Mon, 15 Nov 2021 22:33:59 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0UwnkGTh_1637033457; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0UwnkGTh_1637033457) by smtp.aliyun-inc.com(127.0.0.1); Tue, 16 Nov 2021 11:30:58 +0800 From: Tony Lu To: kgraul@linux.ibm.com Cc: kuba@kernel.org, davem@davemloft.net, guwen@linux.alibaba.com, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org Subject: [PATCH RFC net] net/smc: Ensure the active closing peer first closes clcsock Date: Tue, 16 Nov 2021 11:30:12 +0800 Message-Id: <20211116033011.16658-1-tonylu@linux.alibaba.com> X-Mailer: git-send-email 2.33.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC We found an issue when replacing TCP with SMC. When the actively closed peer called close() in userspace, the clcsock of peer doesn't enter TCP active close progress, but the passive closed peer close it first, and enters TIME_WAIT state. It means the behavior doesn't match what we expected. After reading RFC7609, there is no clear description of the order in which we close clcsock during close progress. Consider this, an application listen and accept connections, and a client connects the server. When client actively closes the socket, the peer's conneciton in server enters TIME_WAIT state, which means the address is occupied and won't be reused before TIME_WAIT dismissing. The server will be restarted failed for EADDRINUSE. Although SO_REUSEADDR can solve this issue, but not all the applications use it. It is very common to restart the server process for some reasons in product environment. If we wait for TIME_WAIT dismissing, the service will be unavailable for a long time. Here is a simple example to reproduce this issue. Run these commands: server: smc_run ./sockperf server --tcp -p 12345 client: smc_run ./sockperf pp --tcp -m 14 -i ${SERVER_IP} -t 10 -p 12345 After client benchmark finished, a TIME_WAIT connection will show up in the server, not the client, which will occupy the address: tcp 0 0 100.200.30.40:12345 100.200.30.41:53010 TIME_WAIT - If we restart server's sockperf, it will fail for: sockperf: ERROR: [fd=3] Can`t bind socket, IP to bind: 0.0.0.0:12345 (errno=98 Address already in use) Here is the process of closing for PeerConnAbort. We can observe this issue both in PeerConnAbort and PeerConnClosed. Client | Server close() // client actively close | smc_release() | smc_close_active() // SMC_PEERCLOSEWAIT1 | smc_close_final() // abort or closed = 1 | smc_cdc_get_slot_and_msg_send() | [ A ] | |smc_cdc_msg_recv_action() // SMC_ACTIVE | queue_work(smc_close_wq, &conn->close_work) | smc_close_passive_work() // SMC_PROCESSABORT or SMC_APPCLOSEWAIT1 | smc_close_passive_abort_received() // only in abort | |close() // server recv zero, close | smc_release() // SMC_PROCESSABORT or SMC_APPCLOSEWAIT1 | smc_close_active() | smc_close_abort() or smc_close_final() // SMC_CLOSED | smc_cdc_get_slot_and_msg_send() // abort or closed = 1 smc_cdc_msg_recv_action() | smc_clcsock_release() queue_work(smc_close_wq, &conn->close_work) | sock_release(tcp) // actively close clc, enter TIME_WAIT smc_close_passive_work() // SMC_PEERCLOSEWAIT1 | smc_conn_free() smc_close_passive_abort_received() // SMC_CLOSED| smc_conn_free() | smc_clcsock_release() | sock_release(tcp) // passive close clc | To solve this issue, clcsock can be shutdown before the passive closed peer closing it, to perform the TCP active close progress first. RFC7609 said the main idea of termination flows, is to terminate the normal TCP connection in the end [1]. But there is no possible to release clcsock before server calling sock_release(tcp), so shutdown the clcsock in [A], which is the only place before server closing it. Link: https://datatracker.ietf.org/doc/html/rfc7609#section-4.8.1 [1] Fixes: b38d732477e4 ("smc: socket closing and linkgroup cleanup") Signed-off-by: Tony Lu Reviewed-by: Wen Gu --- net/smc/smc_close.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c index 0f9ffba07d26..04620b53b74a 100644 --- a/net/smc/smc_close.c +++ b/net/smc/smc_close.c @@ -228,6 +228,12 @@ int smc_close_active(struct smc_sock *smc) /* send close request */ rc = smc_close_final(conn); sk->sk_state = SMC_PEERCLOSEWAIT1; + + /* actively shutdown clcsock before peer close it, + * prevent peer from entering TIME_WAIT state. + */ + if (smc->clcsock && smc->clcsock->sk) + rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR); } else { /* peer event has changed the state */ goto again;