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.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 43380C38A2D for ; Mon, 24 Oct 2022 12:30:13 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.429073.679866 (Exim 4.92) (envelope-from ) id 1omwai-0004qG-67; Mon, 24 Oct 2022 12:30:04 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 429073.679866; Mon, 24 Oct 2022 12:30:04 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1omwai-0004pI-1n; Mon, 24 Oct 2022 12:30:04 +0000 Received: by outflank-mailman (input) for mailman id 429073; Mon, 24 Oct 2022 12:30:02 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1omwag-0004Ra-R3 for xen-devel@lists.xenproject.org; Mon, 24 Oct 2022 12:30:02 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 9420c54b-5397-11ed-8fd0-01056ac49cbb; Mon, 24 Oct 2022 14:30:01 +0200 (CEST) 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-599-AMNzz533PcWqfjPTKcwZtQ-1; Mon, 24 Oct 2022 08:29:49 -0400 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 46285185A78F; Mon, 24 Oct 2022 12:29:49 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.195.118]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EA8A340C6FA3; Mon, 24 Oct 2022 12:29:47 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 3BDE921E6936; Mon, 24 Oct 2022 14:29:46 +0200 (CEST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 9420c54b-5397-11ed-8fd0-01056ac49cbb DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666614600; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ugzIHUs7cdf/Kh5OtlOT6I99mijCPbdrWfAqkmqdgDM=; b=DJThtJFD95Mt2gjNJohdDZf2rOexKNSowaeHLVU5wzqxPvntpexygzpfGydQSs2u29v5Ec 4dSLuiBQLJotYOFK1rZgjKD2PC9gtX4MUs9bVqfVbot5utJnR+IcComgB/krWTl+m8GOt1 cUQKJheHCMa3nRZYWJfG5rZxn7KwxPY= X-MC-Unique: AMNzz533PcWqfjPTKcwZtQ-1 From: Markus Armbruster To: Stefano Brivio Cc: Laurent Vivier , qemu-devel@nongnu.org, Paul Durrant , Thomas Huth , =?utf-8?Q?Danie?= =?utf-8?Q?l_P=2E_Berrang=C3=A9?= , "Dr. David Alan Gilbert" , Greg Kurz , Stefano Stabellini , David Gibson , Eric Blake , xen-devel@lists.xenproject.org, "Michael S. Tsirkin" , Stefan Weil , Paolo Bonzini , Jason Wang , Samuel Thibault , Anthony Perard , Laine Stump Subject: Re: [PATCH v13 17/17] net: stream: add QAPI events to report connection state References: <20221020162558.123284-1-lvivier@redhat.com> <20221020162558.123284-18-lvivier@redhat.com> <87pmel4th4.fsf@pond.sub.org> <52e989b9-6f8d-99c6-ef04-3ce32006b002@redhat.com> <87lep935hn.fsf@pond.sub.org> <87tu3tsczq.fsf@pond.sub.org> <20221024140431.2e93dd2b@elisabeth> Date: Mon, 24 Oct 2022 14:29:46 +0200 In-Reply-To: <20221024140431.2e93dd2b@elisabeth> (Stefano Brivio's message of "Mon, 24 Oct 2022 14:04:31 +0200") Message-ID: <87o7u1qu9x.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Stefano Brivio writes: > On Mon, 24 Oct 2022 13:00:09 +0200 > Markus Armbruster wrote: > >> Markus Armbruster writes: >> >> > Cc: Stefano Brivio >> > >> > Laurent Vivier writes: >> > >> >> On 10/21/22 07:48, Markus Armbruster wrote: >> >>> Laurent Vivier writes: >> >>> >> >>>> The netdev reports NETDEV_STREAM_CONNECTED event when the backend >> >>>> is connected, and NETDEV_STREAM_DISCONNECTED when it is disconnected. >> >>> >> >>> Use cases? >> >> >> >> This is asked by Stefano Brivio to allow libvirt to detect if connection to passt is lost and to restart passt. >> >> [...] >> >> >>> Could similar event signalling be useful for other kinds of netdev >> >>> backends? >> >> >> >> I was wondering, but it becomes more complicated to be generic. >> > >> > Making something complicated and generic where a simpler special >> > solution would do is the worst. >> > >> > Not quite as bad (but still plenty bad) is making a few special >> > solutions first, then replace them all with a generic solution. >> > >> > I believe we should have a good, hard think on possible applications of >> > a generic solution now. >> > >> > There is no need to hold back this series for that. >> > >> > If we conclude a generic solution is called for, we better replace this >> > special solution before it becomes ABI. Either by replacing it before >> > we release it, or by keeping it unstable until we replace it. >> >> Stefano, any thoughts on this? > > Actually, to me, it already looks as generic as it can be: stream > back-ends are the only ones connecting and disconnecting. > > I quickly tried to think about possible, similar events for other > back-ends: > > - user: handled by libslirp, there's no connection, and probably not > much we can or want to export from libslirp itself > > - tap, bridge: the closest equivalent would be interfaces changing > states, but that's something that's also externally observable with a > netlink socket, in case one needs to know. And in any case, it's > logically very different from a connection or disconnection. If we > want events for that, they should have different names > > - vhost-user, vde: we could implement something similar if the need > arises, but it should logically have a different name > > - l2tpv3: stateless, same as datagram-oriented socket. No states, no > events to report, I guess. > > All in all, to me, NETDEV_STREAM_{,DIS}CONNECTED events here don't look > very "special" or hackish. Thanks!