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 BD895C46467 for ; Wed, 11 Jan 2023 15:24:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pFcx5-0001tN-Uh; Wed, 11 Jan 2023 10:23:43 -0500 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 1pFcx2-0001rt-Qr for qemu-devel@nongnu.org; Wed, 11 Jan 2023 10:23:42 -0500 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 1pFcwv-0002cC-2e for qemu-devel@nongnu.org; Wed, 11 Jan 2023 10:23:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673450594; 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=Iy6Hn/CgEo3cgODNktw+HdQfgZ1+vD4tOakW+P0rhwg=; b=CYSPSTio4n9qADGXP+aIkxVJWHF5dOggMOQHllD/XKmDgQGEIKQEXgi42GbAJWsrHJRR/u NKlgO6UnQVJ5Kaiyeh+SoSAC3TzOqTtUr+4FBXOe71fM6gQPou/HRI7wDNCptJXbGm0YBC QK7p40OrgGx/y9p91+w/2yRYKzFBm44= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-214-fjQFl5h_PBqZYIYyYUAbbw-1; Wed, 11 Jan 2023 10:23:12 -0500 X-MC-Unique: fjQFl5h_PBqZYIYyYUAbbw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7E0B9882825; Wed, 11 Jan 2023 15:23:12 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.119]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1D84E40C1141; Wed, 11 Jan 2023 15:23:10 +0000 (UTC) Date: Wed, 11 Jan 2023 15:23:08 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: John Snow Cc: Peter Delevoryas , crosa@redhat.com, bleal@redhat.com, philmd@linaro.org, wainersm@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH v4 1/1] python/machine: Fix AF_UNIX path too long on macOS Message-ID: References: <20230110080756.38271-1-peter@pjd.dev> <20230110080756.38271-2-peter@pjd.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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, Jan 11, 2023 at 10:06:49AM -0500, John Snow wrote: > On Wed, Jan 11, 2023 at 4:07 AM Daniel P. Berrangé wrote: > > > > On Tue, Jan 10, 2023 at 06:18:29PM -0500, John Snow wrote: > > > On Tue, Jan 10, 2023 at 3:34 AM Peter Delevoryas wrote: > > > > > > > > On macOS, private $TMPDIR's are the default. These $TMPDIR's are > > > > generated from a user's unix UID and UUID [1], which can create a > > > > relatively long path: > > > > > > > > /var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T/ > > > > > > > > QEMU's avocado tests create a temporary directory prefixed by > > > > "avo_qemu_sock_", and create QMP sockets within _that_ as well. > > > > The QMP socket is unnecessarily long, because a temporary directory > > > > is created for every QEMUMachine object. > > > > > > > > /avo_qemu_sock_uh3w_dgc/qemu-37331-10bacf110-monitor.sock > > > > > > > > The path limit for unix sockets on macOS is 104: [2] > > > > > > > > /* > > > > * [XSI] Definitions for UNIX IPC domain. > > > > */ > > > > struct sockaddr_un { > > > > unsigned char sun_len; /* sockaddr len including null */ > > > > sa_family_t sun_family; /* [XSI] AF_UNIX */ > > > > char sun_path[104]; /* [XSI] path name (gag) */ > > > > }; > > > > > > > > This results in avocado tests failing on macOS because the QMP unix > > > > socket can't be created, because the path is too long: > > > > > > > > ERROR| Failed to establish connection: OSError: AF_UNIX path too long > > > > > > > > This change resolves by reducing the size of the socket directory prefix > > > > and the suffix on the QMP and console socket names. > > > > > > > > The result is paths like this: > > > > > > > > pdel@pdel-mbp:/var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T > > > > $ tree qemu* > > > > qemu_df4evjeq > > > > qemu_jbxel3gy > > > > qemu_ml9s_gg7 > > > > qemu_oc7h7f3u > > > > qemu_oqb1yf97 > > > > ├── 10a004050.con > > > > └── 10a004050.qmp > > > > > > > > [1] https://apple.stackexchange.com/questions/353832/why-is-mac-osx-temp-directory-in-weird-path > > > > [2] /Library/Developer/CommandLineTools/SDKs/MacOSX12.3.sdk/usr/include/sys/un.h > > > > > > > > Signed-off-by: Peter Delevoryas > > > > > > I'm tentatively staging this with a benefit-of-the-doubt [1] -- my > > > tests are still running -- but I do have a question: > > > > > > > --- > > > > python/qemu/machine/machine.py | 6 +++--- > > > > tests/avocado/avocado_qemu/__init__.py | 2 +- > > > > 2 files changed, 4 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py > > > > index 748a0d807c9d..d70977378305 100644 > > > > --- a/python/qemu/machine/machine.py > > > > +++ b/python/qemu/machine/machine.py > > > > @@ -157,7 +157,7 @@ def __init__(self, > > > > self._wrapper = wrapper > > > > self._qmp_timer = qmp_timer > > > > > > > > - self._name = name or f"qemu-{os.getpid()}-{id(self):02x}" > > > > + self._name = name or f"{id(self):x}" > > > > > > Why is it safe to not differentiate based on the process ID? > > > > > > ... I suppose the thinking is: by default, in machine.py, this is a > > > temp dir created by tempfile.mkdtemp which will be unique per-process. > > > I suppose there's no protection against a caller supplying the same > > > tempdir (or sockdir) to multiple instances, but I suppose in those > > > cases we get to argue that "Well, don't do that, then." > > > > Every process will have a separate tempdir, and if there are > > multiple instances of this class, 'id(self)' will provide > > uniqueness within the process. > > Right. The only small thing is if a caller passes the same directory > to multiple instances across multiple processes, you could > *theoretically* get a collision, and we don't guard against it. It's > not a super likely occurrence so I'm fine with ignoring it, but I > think it's technically possible. If they want to be insane, then they can also pass a 'name' explicitly to override the default socket path choice. 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 :|