Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751615AbaBLMTt (ORCPT ); Wed, 12 Feb 2014 07:19:49 -0500 Received: from smtp.citrix.com ([66.165.176.89]:32022 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751056AbaBLMTr (ORCPT ); Wed, 12 Feb 2014 07:19:47 -0500 X-IronPort-AV: E=Sophos;i="4.95,832,1384300800"; d="scan'208";a="101889625" Date: Wed, 12 Feb 2014 12:19:46 +0000 From: Wei Liu To: "Luis R. Rodriguez" CC: Ian Campbell , "netdev@vger.kernel.org" , , Paul Durrant , Wei Liu , , "linux-kernel@vger.kernel.org" Subject: Re: [RFC 2/2] xen-netback: disable multicast and use a random hw MAC address Message-ID: <20140212121946.GA31937@zion.uk.xensource.com> References: <1392071391-13215-1-git-send-email-mcgrof@do-not-panic.com> <1392071391-13215-3-git-send-email-mcgrof@do-not-panic.com> <1392108205.22033.16.camel@dagon.hellion.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 11, 2014 at 01:53:26PM -0800, Luis R. Rodriguez wrote: > Cc'ing kvm folks as they may have a shared interest on the shared > physical case with the bridge (non NAT). > > On Tue, Feb 11, 2014 at 12:43 AM, Ian Campbell wrote: > > On Mon, 2014-02-10 at 14:29 -0800, Luis R. Rodriguez wrote: > >> From: "Luis R. Rodriguez" > >> > >> Although the xen-netback interfaces do not participate in the > >> link as a typical Ethernet device interfaces for them are > >> still required under the current archtitecture. IPv6 addresses > >> do not need to be created or assigned on the xen-netback interfaces > >> however, even if the frontend devices do need them, so clear the > >> multicast flag to ensure the net core does not initiate IPv6 > >> Stateless Address Autoconfiguration. > > > > How does disabling SAA flow from the absence of multicast? > > See patch 1 in this series [0], but I explain the issue I see with > this on the cover letter [1]. In summary the RFCs on IPv6 make it > clear you need multicast for Stateless address autoconfiguration > (SLAAC is the preferred acronym) and DAD, however the net core has not > made this a requirement, and hence the patch. The caveat which I > address on the cover letter needs to be seriously considered though. > > [0] http://marc.info/?l=linux-netdev&m=139207142110535&w=2 > [1] http://marc.info/?l=linux-netdev&m=139207142110536&w=2 > > > Surely these should be controlled logically independently even if there is some > > notional linkage. > > When a node hops on a network it will query its network by sending a > router solicitation multicast request for its configuration > parameters, the router can respond with router advertisements to > disable SLAAC. > > Apart from that we have no other means to disable SLAAC neatly, and as > I gather that would be counter to the IPv6 RFCs anyway, and that makes > sense. > > > Can SAA not be disabled directly? > > Nope. The ipv6 core assumes all device want ipv6 and this is done upon > netdev registration, and as I noted on my patch 1 description -- > although ipv6 supports a module parameter to disable autoconfiguration > RFC4682 Section 5.4 makes it clear that DAD *MUST* be performed on all FWIW: RFC4862 :-) You had the same typo in patch 1. Wei. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/