From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: Bridge stays down until a port is added Date: Mon, 26 Sep 2011 08:47:43 -0700 Message-ID: <20110926084743.35cb2ccc@nehalam.linuxnetplumber.net> References: <20110811070659.GA21307@torres.zugschlus.de> <20110811081706.7307e8b2@nehalam.ftrdhcpuser.net> <20110917204257.GA2636@torres.zugschlus.de> <1316550027.1783.102.camel@dcbw.foobar.com> <20110925082504.GA32712@torres.zugschlus.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Marc Haber Return-path: Received: from mail.vyatta.com ([76.74.103.46]:40548 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750928Ab1IZPrp (ORCPT ); Mon, 26 Sep 2011 11:47:45 -0400 In-Reply-To: <20110925082504.GA32712@torres.zugschlus.de> Sender: netdev-owner@vger.kernel.org List-ID: The root of this whole problem is really that IPv6 reports addresses in a tentative state to applications that can not be passed to the bind() system call. For most cases, this problem never happens because the tentative addresses are resolved by Duplicate Address Detection before the application starts. But I have seen (and fixed) this happen before this whole discussion started. 1. The problem is not unique to bridges. It happens with bridge, macvtap, even on wireless networks where the device is available but carrier is not asserted. 2. Any change to what the kernel does (like not reporting tentative addresses) would break applications even worse. 3. When the bridge was always reporting carrier, it was in effect breaking IPv6 Duplicate Address Detection. And that is bad.