From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC] ethernet: avoid pre-assigned OUI values in random_ether_addr Date: Mon, 16 May 2011 08:46:44 -0700 Message-ID: <20110516084644.483290f6@nehalam> References: <20110513171729.247b126e@nehalam> <1305488809.3120.162.camel@edumazet-laptop> <1305490850.8178.57.camel@Joe-Laptop> <1305493826.3120.174.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Joe Perches , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from mail.vyatta.com ([76.74.103.46]:44519 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756198Ab1EPPqr convert rfc822-to-8bit (ORCPT ); Mon, 16 May 2011 11:46:47 -0400 In-Reply-To: <1305493826.3120.174.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, 15 May 2011 23:10:26 +0200 Eric Dumazet wrote: > Le dimanche 15 mai 2011 =C3=A0 13:20 -0700, Joe Perches a =C3=A9crit = : > > On Sun, 2011-05-15 at 21:46 +0200, Eric Dumazet wrote: > > > Le vendredi 13 mai 2011 =C3=A0 17:17 -0700, Stephen Hemminger a =C3= =A9crit : > > > > There are some addresses in the assigned vendor block that don'= t obey > > > > the locally assigned convention. These should be avoided by ran= dom_ether_addr > > > > assignment. > > > We call random_ether_addr() for some virtual devices, maybe we ca= n add a > > > __random_ether_addr() helper for them and not avoid these OUI ? > >=20 > > Unless it's speed critical, it's probably not worthwhile. > >=20 >=20 > Speed was not my concern, but getting idea of why avoiding pre-assign= ed > OUI was a concern for them, if they dont hit a real Ethernet domain. My concern was that after some discussion with IEEE committee that many virtual environments are using locally assigned addresses that get brid= ged onto real networks. That started me thinking that the current code should be more careful to avoid potential conflicts. My opinion is that this not worth worryin= g about because the likelihood of conflict with any one of these old addresses is as about as the unlikely as two hosts choosing the same value. But I wanted to raise the issue for explicit discussion and fram= e it with what would be required to handle it. --=20