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Mon, 2 Nov 2020 09:44:49 +0100 (CET) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Subject: Re: [PATCH 00/11] sockets: Attempt to drain the abstract socket swamp References: <20201029133833.3450220-1-armbru@redhat.com> <87pn50vxa0.fsf@dusky.pond.sub.org> <20201030102049.GI99222@redhat.com> Date: Mon, 02 Nov 2020 09:44:49 +0100 In-Reply-To: <20201030102049.GI99222@redhat.com> ("Daniel P. =?utf-8?Q?Ber?= =?utf-8?Q?rang=C3=A9=22's?= message of "Fri, 30 Oct 2020 10:20:49 +0000") Message-ID: <87zh40no5a.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=63.128.21.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/02 03:02:24 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , xiaoqiang zhao , QEMU , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Gerd Hoffmann , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > On Fri, Oct 30, 2020 at 11:11:19AM +0100, Markus Armbruster wrote: >> Marc-Andr=C3=A9 Lureau writes: >>=20 >> > Hi Markus, >> > >> > On Thu, Oct 29, 2020 at 5:43 PM Markus Armbruster = wrote: >> > >> >> In my opinion, the Linux-specific abstract UNIX domain socket feature >> >> introduced in 5.1 should have been rejected. The feature is niche, >> >> the interface clumsy, the implementation buggy and incomplete, and th= e >> >> test coverage insufficient. Review fail. >> >> >> > >> > I also failed (as chardev maintainer..) to not only review but weigh i= n and >> > discuss the merits or motivations behind it. >> > >> > I agree with you. Also the commit lacks motivation behind this "featur= e". >> > >> > >> >> Fixing the parts we can still fix now is regrettably expensive. If I >> >> had the power to decide, I'd unceremoniously revert the feature, >> >> compatibility to 5.1 be damned. But I don't, so here we go. >> >> >> >> I'm not sure this set of fixes is complete. However, I already spent >> >> too much time on this, so out it goes. Lightly tested. >> >> >> >> Regardless, I *will* make time for ripping the feature out if we >> >> decide to do that. Quick & easy way to avoid reviewing this series >> >> *hint* *hint*. >> >> >> > >> > well, fwiw, I would also take that approach too, to the risk of upsett= ing >> > the users. >>=20 >> Reverting the feature requires rough consensus and a patch. >>=20 >> I can provide a patch, but let's give everybody a chance to object >> first. Daniel, do you object, yes or no? I need to know to avoid wasting even more time. >> > But maybe we can get a clear reason behind it before that >> > happens. (sorry, I didn't dig the ML archive is such evidence is there= , it >> > should have been in the commit message too) >>=20 >> I just did, and found next to nothing. >>=20 >> This is the final cover letter: >>=20 >> qemu-sockets: add abstract UNIX domain socket support >>=20 >> qemu does not support abstract UNIX domain >> socket address. Add this ability to make qemu handy >> when abstract address is needed. >>=20 >> Boils down to "$feature is needed because it's handy when it's needed", >> which is less than helpful. > > Well if you have an existing application that uses abstract sockets, > and you want to connect QEMU to it, then QEMU needs to support it, > or you are forced to interject a proxy between your app and QEMU > which is an extra point of failure and lantency. I was interested > in whether there was a specific application they were using, but > that is largely just from a curiosity POV. There's enough usage of > abstract sockets in apps in general that is it clearly a desirable > feature to enable. > > Even if no external app is involved and you're just connecting > together 2 QEMU processes' chardevs, abstract sockets are interesting > because of their differing behaviour to non-abstract sockets. > > Most notably non-abstract sockets are tied to the filesystem mount > namespace in Linux, where as abstract sockets are tied to the network > namespace. This is a useful distinction in the container world. Ordinaril= y > you can't connect QEMUs in 2 separate containers together, because they > always have distinct mount namespaces. There is often the ability to > share network namespaces between containers though, and thus unlock > use of abstract sockets for communications.=20 If this was patch review, I'd now ask the patch submitter to work it into the commit message. Thanks anyway :) [...]