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 4FA25FA3741 for ; Mon, 24 Oct 2022 12:05:13 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.429050.679822 (Exim 4.92) (envelope-from ) id 1omwCV-0008NP-7G; Mon, 24 Oct 2022 12:05:03 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 429050.679822; Mon, 24 Oct 2022 12:05:03 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1omwCV-0008NI-44; Mon, 24 Oct 2022 12:05:03 +0000 Received: by outflank-mailman (input) for mailman id 429050; Mon, 24 Oct 2022 12:05:02 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1omwCU-0008Ms-4w for xen-devel@lists.xenproject.org; Mon, 24 Oct 2022 12:05:02 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 14f86b15-5394-11ed-91b5-6bf2151ebd3b; Mon, 24 Oct 2022 14:05:00 +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-260-5LUlF93eMRuhxrfgfGRSFA-1; Mon, 24 Oct 2022 08:04:55 -0400 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 5FA3E8065E8; Mon, 24 Oct 2022 12:04:54 +0000 (UTC) Received: from maya.cloud.tilaa.com (ovpn-208-31.brq.redhat.com [10.40.208.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E2E5E200C0DA; Mon, 24 Oct 2022 12:04:53 +0000 (UTC) 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: 14f86b15-5394-11ed-91b5-6bf2151ebd3b DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666613098; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TN68KVpvR7XKYr0YdRyHBatb1VXNIh4kpbgamAYS4Zw=; b=hyZe1oIm3GjMDbconZbQuNvnE7S3VewWsWXE8LPa1aMmc7HhV6BY86waaT7IuTbbI7d4o0 HiGDli3zlqjBck0QUGOCNis1vU8CQmMOabKNkdnwdwqoGiQA5CqI6OAjutvBxcAZ0JzU1/ 5Om6uNMwEIqkmLRNU06lhFvIAgInOFE= X-MC-Unique: 5LUlF93eMRuhxrfgfGRSFA-1 Date: Mon, 24 Oct 2022 14:04:31 +0200 From: Stefano Brivio To: Markus Armbruster Cc: Laurent Vivier , qemu-devel@nongnu.org, Paul Durrant , Thomas Huth , "Daniel P. =?UTF-8?B?QmVy?= =?UTF-8?B?cmFuZ8Op?=" , "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 Message-ID: <20221024140431.2e93dd2b@elisabeth> In-Reply-To: <87tu3tsczq.fsf@pond.sub.org> 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> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 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. -- Stefano