From patchwork Sat Jul 22 07:49:33 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Knut Omang X-Patchwork-Id: 792459 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xF2VZ1sbGz9s7m for ; Sat, 22 Jul 2017 19:32:52 +1000 (AEST) Received: from localhost ([::1]:46262 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dYqmH-00083x-S8 for incoming@patchwork.ozlabs.org; Sat, 22 Jul 2017 05:32:49 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37127) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dYqlv-00083o-9q for qemu-devel@nongnu.org; Sat, 22 Jul 2017 05:32:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dYqls-0005Uk-2T for qemu-devel@nongnu.org; Sat, 22 Jul 2017 05:32:27 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:42807) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dYqlr-0005Ug-OY for qemu-devel@nongnu.org; Sat, 22 Jul 2017 05:32:24 -0400 Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id v6M9WLX0020899 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 22 Jul 2017 09:32:21 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id v6M9WL9l000988 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 22 Jul 2017 09:32:21 GMT Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id v6M9WKIG006935; Sat, 22 Jul 2017 09:32:20 GMT Received: from abi.no.oracle.com (/10.172.144.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sat, 22 Jul 2017 00:49:51 -0700 From: Knut Omang To: "Daniel P . Berrange" , Gerd Hoffmann , Paolo Bonzini Date: Sat, 22 Jul 2017 09:49:33 +0200 Message-Id: X-Mailer: git-send-email 2.9.4 In-Reply-To: References: X-Source-IP: aserv0022.oracle.com [141.146.126.234] X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] [fuzzy] X-Received-From: 141.146.126.69 Subject: [Qemu-devel] [PATCH v5 4/4] sockets: Handle race condition between binds to the same port X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Knut Omang , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" If an offset of ports is specified to the inet_listen_saddr function(), and two or more processes tries to bind from these ports at the same time, occasionally more than one process may be able to bind to the same port. The condition is detected by listen() but too late to avoid a failure. This function is called by socket_listen() and used by all socket listening code in QEMU, so all cases where any form of dynamic port selection is used should be subject to this issue. Add code to close and re-establish the socket when this condition is observed, hiding the race condition from the user. Also clean up some issues with error handling to allow more accurate reporting of the cause of an error. This has been developed and tested by means of the test-listen unit test in the previous commit. Enable the test for make check now that it passes. Signed-off-by: Knut Omang Reviewed-by: Bhavesh Davda Reviewed-by: Yuval Shaia Reviewed-by: Girish Moodalbail Signed-off-by: Knut Omang --- tests/Makefile.include | 2 +- util/qemu-sockets.c | 51 ++++++++++++++++++++++++++++++++----------- 2 files changed, 39 insertions(+), 14 deletions(-) diff --git a/tests/Makefile.include b/tests/Makefile.include index b37c0c8..9d2131d 100644 --- a/tests/Makefile.include +++ b/tests/Makefile.include @@ -128,7 +128,7 @@ check-unit-y += tests/test-bufferiszero$(EXESUF) gcov-files-check-bufferiszero-y = util/bufferiszero.c check-unit-y += tests/test-uuid$(EXESUF) check-unit-y += tests/ptimer-test$(EXESUF) -#check-unit-y += tests/test-listen$(EXESUF) +check-unit-y += tests/test-listen$(EXESUF) gcov-files-ptimer-test-y = hw/core/ptimer.c check-unit-y += tests/test-qapi-util$(EXESUF) gcov-files-test-qapi-util-y = qapi/qapi-util.c diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 39f207c..8ca3ba6 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -210,7 +210,9 @@ static int inet_listen_saddr(InetSocketAddress *saddr, char port[33]; char uaddr[INET6_ADDRSTRLEN+1]; char uport[33]; - int slisten, rc, port_min, port_max, p; + int rc, port_min, port_max, p; + int slisten = 0; + int saved_errno = 0; Error *err = NULL; memset(&ai,0, sizeof(ai)); @@ -277,27 +279,50 @@ static int inet_listen_saddr(InetSocketAddress *saddr, port_max = saddr->has_to ? saddr->to + port_offset : port_min; for (p = port_min; p <= port_max; p++) { inet_setport(e, p); - if (try_bind(slisten, saddr, e) >= 0) { - goto listen; - } - if (p == port_max) { - if (!e->ai_next) { + rc = try_bind(slisten, saddr, e); + if (rc) { + if (errno == EADDRINUSE) { + continue; + } else { error_setg_errno(errp, errno, "Failed to bind socket"); + goto listen_failed; + } + } + rc = listen(slisten, 1); + if (!rc) { + goto listen_ok; + } else if (errno == EADDRINUSE) { + /* Someone else managed to bind to the same port and beat us + * to listen on it! Socket semantics does not allow us to + * recover from this situation, so we need to recreate the + * socket to allow bind attempts for subsequent ports: + */ + closesocket(slisten); + slisten = create_fast_reuse_socket(e, errp); + if (slisten >= 0) { + continue; } } + error_setg_errno(errp, errno, "Failed to listen on socket"); + goto listen_failed; } + } + if (err) { + error_propagate(errp, err); + } else { + error_setg_errno(errp, errno, "Failed to find an available port"); + } + +listen_failed: + saved_errno = errno; + if (slisten >= 0) { closesocket(slisten); } freeaddrinfo(res); + errno = saved_errno; return -1; -listen: - if (listen(slisten,1) != 0) { - error_setg_errno(errp, errno, "Failed to listen on socket"); - closesocket(slisten); - freeaddrinfo(res); - return -1; - } +listen_ok: if (update_addr) { g_free(saddr->host); saddr->host = g_strdup(uaddr);