From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Dichtel Subject: Re: [PATCH] ipv6: default route for link local address is not added while assigning a address Date: Mon, 03 Feb 2014 17:26:12 +0100 Message-ID: <52EFC324.1030102@6wind.com> References: <52E8A2AA.3090507@linux.vnet.ibm.com> <52E8DA37.7010208@6wind.com> <20140130232909.GH25336@order.stressinduktion.org> <52EF42FF.60907@linux.vnet.ibm.com> <52EFB454.1040908@6wind.com> <20140203160838.GA17999@order.stressinduktion.org> Reply-To: nicolas.dichtel@6wind.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE To: Sohny Thomas , netdev , linux-kernel@vger.kernel.org, yoshfuji@linux-ipv6.org, davem@davemloft.net, kumuda Return-path: In-Reply-To: <20140203160838.GA17999@order.stressinduktion.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Le 03/02/2014 17:08, Hannes Frederic Sowa a =C3=A9crit : > Hello! > > On Mon, Feb 03, 2014 at 04:23:00PM +0100, Nicolas Dichtel wrote: >> Le 03/02/2014 08:19, Sohny Thomas a =C3=A9crit : >>> >>>> Actually I am not so sure, there is no defined semantic of flush. = I would >>>> be ok with all three solutions: leave it as is, always add link-lo= cal >>>> address (it does not matter if we don't have a link-local address = on >> It matters. This address is required. >> RFC 4291 >> Section 2.1: >> All interfaces are required to have at least one Link-Local unic= ast >> address (see Section 2.8 for additional required addresses). >> Section 2.8: >> o Its required Link-Local address for each interface. > > Yes, sure, it is required. But you also can manually delete the LL ad= dress and > we don't guard against that. Sure. It's why I don't like this patch, it fix a user error. > >>>> that interface, as a global scoped one is just fine enough) or mak= e flush >>>> not >>>> remove the link-local address (but this seems a bit too special ca= sed for >>>> me). >>> >>> 1) In case if we leave it as it is, there is rfc 6724 rule 2 to be >>> considered ( >>> previously rfc 3484) >>> >>> Rule 2: Prefer appropriate scope. >>> If Scope(SA) < Scope(SB): If Scope(SA) < Scope(D), then prefer = SB and >>> otherwise prefer SA. Similarly, if Scope(SB) < Scope(SA): If >>> Scope(SB) < Scope(D), then prefer SA and otherwise prefer SB. >>> >>> Test: >>> >>> Destination: fe80::2(LS) >>> Candidate Source Addresses: 3ffe::1(GS) or fec0::1(SS) or LLA(= LS) >>> Result: LLA(LS) >>> Scope(LLA) < Scope(fec0::1): If Scope(LLA) < Scope(fe80::2), = no, >>> prefer LLA >>> Scope(LLA) < Scope(3ffe::1): If Scope(LLA) < Scope(fe80::2), = no, >>> prefer LLA >>> >>> >>> Now the above test fails since the route itself is not present, and= the >>> test >>> assumes that the route gets added since the LLA is not removed duri= ng the >>> test >> In your scenario, the link local route has been removed manually, no= t by the >> kernel. What is your network manager? > > The test scenario is outlined here: > > > Basically, the command in question is this one: > > [root@localhost ~]# ip -6 -statistics -statistics route flush dev et= h0 > > which removes the fe80::/64 route. > >>> 2) having a LLA always helps in NDP i think >> A link-local Address yes, it's a MUST. But having only the link loca= l route >> will >> not help. > > Agreed, the LL address should be available, too. I currently don't kn= ow > what will break if LL address is not available. I guess MLD won't wor= k > properly and thus even basic connectivity won't work with some switch= es. > >>> 3) making flush not remove link-local address will be chnaging >>> functionality of >>> ip flush command >> You can flush by specifying the prototype: >> ip -6 route flush proto static > > So we have four possiblities now: > > 1) leave it as is > > seems still acceptable to me > > 2) add fe80::/64 route unconditionally if any address gets added > > Sohny's patch already looks good in doing so at first look. I don't like this solution, because it's a kernel patch to fix a config= uration problem. > > 3) add fe80::/64 route in case LL address gets added via inet6_rtm_ne= waddr > > would be ok, too. I tend towards this solution somehow by now. This seems right also, but I'm not sure that this will fix Sohny's pb. > > 4) make flush not remove the fe80::/64 address > > Least favourable to me. I guess this also woud need iproute change > and seems most difficult to do. Why using this command 'ip -6 route flush proto static' isn't possible? I think that we know what kind of route is added for these TAHI tests, = hence it's better to remove only routes added manually (or by a routing daemo= n if it's the case). Removing kernel routes may hide bugs: imagine the kernel adds a wrong r= oute, TAHI will not detect it. Regards, Nicolas