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 8CF6FC433FE for ; Wed, 30 Nov 2022 13:21:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p0N0v-00087k-V1; Wed, 30 Nov 2022 08:20:38 -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 1p0N0m-00085s-V9 for qemu-devel@nongnu.org; Wed, 30 Nov 2022 08:20:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p0N0h-0004OD-FD for qemu-devel@nongnu.org; Wed, 30 Nov 2022 08:20:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669814421; 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=hlYBIbZ8bPrm1fSbt67PAPFS/mJn7XUum0mfxbQKGoQ=; b=OUdCq5yxqDvItu020ZEZzUgcVS8QYxEiHyclQX636vxPrH0xhjsVsE27jDG8HI1fk/cThg XVzWpR8JS+rEnQ1VN8bkOjUT3riCD0R9Li9dPi84rHR3ilIylkZdIgaOsTxmLx3qappi+a NXe4366uBnvASW+Cl/t4WzQ+6A5yeJc= 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-319-jqDfdY3ZPNGtdOmnfvDMzA-1; Wed, 30 Nov 2022 08:20:20 -0500 X-MC-Unique: jqDfdY3ZPNGtdOmnfvDMzA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BCAD6801585 for ; Wed, 30 Nov 2022 13:20:19 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.63]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9FB522028CE4; Wed, 30 Nov 2022 13:20:18 +0000 (UTC) Date: Wed, 30 Nov 2022 13:20:14 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: qemu-devel@nongnu.org, Peter Krempa , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Gerd Hoffmann Subject: Re: Who / what uses QMP command add_client? Message-ID: References: <878rjtretb.fsf@pond.sub.org> <878rjsmxos.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <878rjsmxos.fsf@pond.sub.org> User-Agent: Mutt/2.2.7 (2022-08-07) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Received-SPF: pass client-ip=170.10.129.124; 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, Nov 30, 2022 at 01:30:43PM +0100, Markus Armbruster wrote: > Daniel P. Berrangé writes: > > > On Tue, Nov 29, 2022 at 03:54:56PM +0100, Markus Armbruster wrote: > >> QMP command add_client's schema: > >> > >> ## > >> # @add_client: > >> # > >> # Allow client connections for VNC, Spice and socket based > >> # character devices to be passed in to QEMU via SCM_RIGHTS. > >> # > >> # @protocol: protocol name. Valid names are "vnc", "spice", "@dbus-display" or > >> # the name of a character device (eg. from -chardev id=XXXX) > >> # > >> # @fdname: file descriptor name previously passed via 'getfd' command > >> # > >> # @skipauth: whether to skip authentication. Only applies > >> # to "vnc" and "spice" protocols > >> # > >> # @tls: whether to perform TLS. Only applies to the "spice" > >> # protocol > >> # > >> # Returns: nothing on success. > >> # > >> # Since: 0.14 > >> # > >> # Example: > >> # > >> # -> { "execute": "add_client", "arguments": { "protocol": "vnc", > >> # "fdname": "myclient" } } > >> # <- { "return": {} } > >> # > >> ## > >> { 'command': 'add_client', > >> 'data': { 'protocol': 'str', 'fdname': 'str', '*skipauth': 'bool', > >> '*tls': 'bool' } } > >> > >> Spot the design flaw! > >> > >> It's overloaded @protocol. Two issues. > > > > My bad. Can't imagine why I called its impl add_graphics_client > > but then made it work for graphics clients and chardevs all > > the way back in day 1. > > We had a lot less experience with QMP interface design back then. > > The obvious fix (if we want to) is to add protocol "chardev" with > additional member for the chardev's ID, and deprecate use of chardev IDs > as protocol. > > Compatibility break: a chardev with ID "chardev" no longer works. > > Could also use "socket" instead of "chardev"if we're confident no other > chardev type will ever be needed here. Or introduce a new 'id' field that are refer to a qdev ID, since we can assign IDs to VNC/SPICE server instances too, when there are multiple instances, and they'll be non-overlapping with chardev IDs ? IOW we make 'protocol' and 'id' both optional in QAPI schema, and declare them mutually exclusive. Deprecate 'protocol' in favour of 'id'. Then eventually delete 'protocol' and make 'id' mandatory. > >> Are there any known uses with character devices? > > See [*] below. > > >> If not, any ideas why one would want to use the command with character > >> devices? > > > > Ordinarily a client will directly connect() to QEMU to setup the > > socket connection. Depending on the protocol this may involve both > > TLS negotiation and authentication. This is a good thing when exposed > > over a public IP address. It is tedious when connecting from a local > > client though. > > > > The idea behind the 'add_client' method was to enable short circuiting > > of encryption and authentication, for local only clients. For example, > > virt-viewer/virt-manager can do socketpair() and pass one of the FDs > > across to QEMU, and bypass any VNC authentication. This is still secure, > > as FD passing is mediated by libvirt which the app has already > > authenticated against. > > > > This is conceptually useful for any backend exposed as a network > > socket, accepting ad-hoc client connections. So it is in scope for > > chardevs, nbd, vnc, spice. > > Does libvirt implement this with socket character devices? Opps, I meant to say that libvirt only uses add_client for graphics devices. We've never used it for chardevs AFAICT. 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 :|