From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [Bugme-new] [Bug 9545] New: Cannot bring up a bridge interface without a MAC address set Date: Tue, 11 Dec 2007 21:36:59 -0800 Message-ID: <20071211213659.42591478@freepuppy.rosehill> References: <20071211132614.5854b0f1.akpm@linux-foundation.org> <20071211145243.66e1f66a@freepuppy.rosehill> <20071212015105.GB20618@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Andrew Morton , netdev@vger.kernel.org, bugme-daemon@bugzilla.kernel.org, berrange@redhat.com, Jeff Garzik , "Rafael J. Wysocki" To: Herbert Xu Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:53758 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757463AbXLLFja (ORCPT ); Wed, 12 Dec 2007 00:39:30 -0500 In-Reply-To: <20071212015105.GB20618@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 12 Dec 2007 09:51:05 +0800 Herbert Xu wrote: > On Tue, Dec 11, 2007 at 02:52:43PM -0800, Stephen Hemminger wrote: > > > > The tap devices have to have addresses don't they. So bringing up an empty > > bridge is meaningless. If you just add the device first then it will work. > > Actually bringing up a bridge with no constituents is useful for > a bridge that's made up of only virtual interfaces. Since each > vritual interface may be created or destroyed at run-time it'd > be quite awkward to check every time to see if that's the last > or first and act differently on the bridge. > > More importantly constiuents can be added to and removed from a > bridge without taking it down. > > > Could be fixed to prevent errors from existing scripts but it is not a complete showstopper. > > Well this stops FC8 working with Xen so for that it's a showstopper :) > > > The problem is that when device is brought up it propogates events up to > > other layers and applications, these layers will then query and see a bogus > > address. > > What exactly would it break for this scenario though? Well with earlier kernels, ipv6 and others would see an invalid address (all zeros). That could be a problem if some netlink watching program or udev script propagated that value into a database or management interface. But now using a random value, that won't happen. -- Stephen Hemminger