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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D1799CA0ED3 for ; Wed, 4 Sep 2024 07:14:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1slkCq-0006Ua-TP; Wed, 04 Sep 2024 03:13:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1slkCp-0006U6-NM for qemu-devel@nongnu.org; Wed, 04 Sep 2024 03:13:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1slkCn-0004P8-8T for qemu-devel@nongnu.org; Wed, 04 Sep 2024 03:13:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1725434007; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ukw6/zzlE1EDLQwBaifqbwmT9by9oZAgte8hve1TF9Y=; b=TQkHE+prHtaB8+0w+A5/6fLn/rKrMW8inu5AMoLHdHuHv8g4bd9XXrOiaSXR6iTrKseHKp eXSFpFZwbuqez+QUuLIOA6cYvmLiJdOgXhdp8QS1VcCLdsTMfox/ggEwYwDxhpQb1KTe8L 99hkqvJfo6xqAfvX8xu7ic3NyP138OQ= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-372-jnFbFS6wNhStfpKHtk9hBw-1; Wed, 04 Sep 2024 03:13:23 -0400 X-MC-Unique: jnFbFS6wNhStfpKHtk9hBw-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DADB41955F41; Wed, 4 Sep 2024 07:13:21 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.53]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 69B8219560A3; Wed, 4 Sep 2024 07:13:20 +0000 (UTC) Date: Wed, 4 Sep 2024 08:13:17 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Subject: Re: [PATCH] tests/functional/test_vnc: Reduce raciness in find_free_ports() Message-ID: References: <20240903143553.16877-1-philmd@linaro.org> <73ba8035-9fa6-440e-9ca9-0b6934525489@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <73ba8035-9fa6-440e-9ca9-0b6934525489@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 11 X-Spam_score: 1.1 X-Spam_bar: + X-Spam_report: (1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.142, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Sep 04, 2024 at 08:20:12AM +0200, Thomas Huth wrote: > On 03/09/2024 16.50, Daniel P. Berrangé wrote: > > On Tue, Sep 03, 2024 at 04:35:53PM +0200, Philippe Mathieu-Daudé wrote: > > > Pass the port range as argument. In order to reduce races > > > when looking for free ports, use a per-target per-process > > > base port (based on the target built-in hash). > > > > > > Signed-off-by: Philippe Mathieu-Daudé > > > --- > > > Based-on: <20240830133841.142644-33-thuth@redhat.com> > > > --- > > > tests/functional/test_vnc.py | 12 ++++++++---- > > > 1 file changed, 8 insertions(+), 4 deletions(-) > > > > > > diff --git a/tests/functional/test_vnc.py b/tests/functional/test_vnc.py > > > index b769d3b268..508db0709d 100755 > > > --- a/tests/functional/test_vnc.py > > > +++ b/tests/functional/test_vnc.py > > > @@ -10,6 +10,7 @@ > > > # This work is licensed under the terms of the GNU GPL, version 2 or > > > # later. See the COPYING file in the top-level directory. > > > +import os > > > import socket > > > from typing import List > > > @@ -18,7 +19,6 @@ > > > VNC_ADDR = '127.0.0.1' > > > VNC_PORT_START = 32768 > > > -VNC_PORT_END = VNC_PORT_START + 1024 > > > def check_bind(port: int) -> bool: > > > @@ -41,9 +41,10 @@ def check_connect(port: int) -> bool: > > > return True > > > -def find_free_ports(count: int) -> List[int]: > > > +# warning, racy function > > > +def find_free_ports(portrange, count: int) -> List[int]: > > > result = [] > > > - for port in range(VNC_PORT_START, VNC_PORT_END): > > > + for port in portrange: > > > if check_bind(port): > > > result.append(port) > > > if len(result) >= count: > > > @@ -91,7 +92,10 @@ def test_change_password(self): > > > password='new_password') > > > def test_change_listen(self): > > > - a, b, c = find_free_ports(3) > > > + per_arch_port_base = abs((os.getpid() + hash(self.arch)) % (10 ** 4)) > > > + port_start = VNC_PORT_START + per_arch_port_base > > > + port_stop = port_start + 100 > > > + a, b, c = find_free_ports(range(port_start, port_stop), 3) > > > self.assertFalse(check_connect(a)) > > > self.assertFalse(check_connect(b)) > > > self.assertFalse(check_connect(c)) > > > > As your comment says, this is still racey, and its also not too > > nice to read & understand this logic. How about we just make > > test_vnc.py be serialized wrt itself ? > > We'll likely have more tests that need a free port in the future... > tests/avocado/migration.py and tests/avocado/reverse_debugging.py use > find_free_ports(), too, so we should maybe think of a logic that avoids > clashes between different tests, too. Create a context manager that holds a fcntl lockfile on disk, while giving you a free port ? class FreePort: def __enter__(self): self.num = find_free_port() ..acquire fcntl lock... def __exit__(self): ...release fcntl lock.. Letting tests do with FreePort() as port: ..do some test that uses port.num.... With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|