From mboxrd@z Thu Jan 1 00:00:00 1970 From: Herbert Xu Subject: Re: [0/3] bridge: Do not send multicast queries by default Date: Sun, 15 Apr 2012 19:13:00 +0800 Message-ID: <20120415111300.GA14147@gondor.apana.org.au> References: <20120413123641.GA758@gondor.apana.org.au> <20120413.105345.319552552748408545.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from sting.hengli.com.au ([178.18.18.71]:38566 "EHLO fornost.hengli.com.au" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751534Ab2DOLNI (ORCPT ); Sun, 15 Apr 2012 07:13:08 -0400 Content-Disposition: inline In-Reply-To: <20120413.105345.319552552748408545.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Apr 13, 2012 at 10:53:45AM -0400, David Miller wrote: > From: Herbert Xu > Date: Fri, 13 Apr 2012 20:36:41 +0800 > > > (incidentally, I noticed that our IPv6 code has been "fixed" to not > > use zero source addresses, which is wrong as we may end up being THE > > MLD querier in a network). > > I seem to recall it was explicitly changed to be this way and that > there was a good reason for this, see the history. Right, the reason given is that RFC2710 (for MLD) requires the source address to be a link-local address. However, we're not implementing an RFC2710 node here. What we're doing is better described by RFC4541 (IGMP/MLD snooping), which calls for the use of a zero source address for both IPv4 and IPv6. The reason is precisely because it's invalid for normal querier nodes and as such they would ignore us (rather than elect us and potentially disrupt things). Now granted we may also end up having other nodes ignoring our queries where we'd rather that they answered us with reports. However, this isn't as bad because the whole querying mechanism in the snooping code is merely an optimisation to speed up convergence primarily during start-up. So if we don't see the reports straight away it's not a deal-breaker. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt