From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [Qemu-devel] [RFC v2 PATCH 5/4 PATCH] virtio-net: send gratuitous packet when needed Date: Mon, 24 Oct 2011 11:11:05 +0200 Message-ID: <1319447465.31243.15.camel@deadeye> References: <20111022054311.21798.3340.stgit@dhcp-8-146.nay.redhat.com> <87ty6z10f8.fsf@rustcorp.com.au> <20111024052526.GA2362@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Rusty Russell , Jason Wang , , , , , , , , To: "Michael S. Tsirkin" Return-path: Received: from mail.solarflare.com ([216.237.3.220]:25123 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753344Ab1JXJLc (ORCPT ); Mon, 24 Oct 2011 05:11:32 -0400 In-Reply-To: <20111024052526.GA2362@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2011-10-24 at 07:25 +0200, Michael S. Tsirkin wrote: > On Mon, Oct 24, 2011 at 02:54:59PM +1030, Rusty Russell wrote: > > On Sat, 22 Oct 2011 13:43:11 +0800, Jason Wang wrote: > > > This make let virtio-net driver can send gratituous packet by a new > > > config bit - VIRTIO_NET_S_ANNOUNCE in each config update > > > interrupt. When this bit is set by backend, the driver would schedule > > > a workqueue to send gratituous packet through NETDEV_NOTIFY_PEERS. > > > > > > This feature is negotiated through bit VIRTIO_NET_F_GUEST_ANNOUNCE. > > > > > > Signed-off-by: Jason Wang > > > > This seems like a huge layering violation. Imagine this in real > > hardware, for example. > > commits 06c4648d46d1b757d6b9591a86810be79818b60c > and 99606477a5888b0ead0284fecb13417b1da8e3af > document the need for this: > > NETDEV_NOTIFY_PEERS notifier indicates that a device moved to a > different physical link. > and > In real hardware such notifications are only > generated when the device comes up or the address changes. > > So hypervisor could get the same behaviour by sending link up/down > events, this is just an optimization so guest won't do > unecessary stuff like try to reconfigure an IP address. > > > Maybe LOCATION_CHANGE would be a better name? [...] We also use this in bonding failover, where the system location doesn't change but a different link is used. However, I do recognise that the name ought to indicate what kind of change happened and not what the expected action is. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.