From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [patch iproute2 1/6] iproute2: ipa: show switch id Date: Thu, 04 Dec 2014 14:55:07 -0600 Message-ID: <87388vw2xg.fsf@x220.int.ebiederm.org> References: <1417683438-10935-1-git-send-email-jiri@resnulli.us> <1417683438-10935-2-git-send-email-jiri@resnulli.us> <87y4qne6if.fsf@x220.int.ebiederm.org> <20141204163024.GG1861@nanopsycho.orion> <87388v9ua6.fsf@x220.int.ebiederm.org> <20141204182451.GI1861@nanopsycho.orion> <87k327450a.fsf@x220.int.ebiederm.org> <20141204191926.GK1861@nanopsycho.orion> <87wq672p49.fsf@x220.int.ebiederm.org> <87h9xbxjrd.fsf@x220.int.ebiederm.org> <20141204202742.GM1861@nanopsycho.orion> Mime-Version: 1.0 Content-Type: text/plain Cc: netdev@vger.kernel.org, davem@davemloft.net, nhorman@tuxdriver.com, andy@greyhouse.net, tgraf@suug.ch, dborkman@redhat.com, ogerlitz@mellanox.com, jesse@nicira.com, pshelar@nicira.com, azhou@nicira.com, ben@decadent.org.uk, stephen@networkplumber.org, jeffrey.t.kirsher@intel.com, vyasevic@redhat.com, xiyou.wangcong@gmail.com, john.r.fastabend@intel.com, edumazet@google.com, jhs@mojatatu.com, sfeldma@gmail.com, f.fainelli@gmail.com, roopa@cumulusnetworks.com, linville@tuxdriver.com, jasowang@redhat.com, nicolas.dichtel@6wind.com, ryazanov.s.a@gmail.com, buytenh@wantstofly.org, aviadr@mellanox.com, nbd@openwrt.org, alexei.starovoitov@gmail.com, Neil.Jerram@metaswitch.com, ronye@mellanox.com, simon.horman@netronome.com, alexander.h.duyck@redhat.com, john.ronciak@intel.com, mleitner@redhat.com, shrijeet@gmail.com, gospo@cumulusnetworks.com, bcrl@kvack.org, hemal@broadcom.c To: Jiri Pirko Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]:33932 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753161AbaLDU5Z (ORCPT ); Thu, 4 Dec 2014 15:57:25 -0500 In-Reply-To: <20141204202742.GM1861@nanopsycho.orion> (Jiri Pirko's message of "Thu, 4 Dec 2014 21:27:42 +0100") Sender: netdev-owner@vger.kernel.org List-ID: Jiri Pirko writes: > Thu, Dec 04, 2014 at 09:06:14PM CET, ebiederm@xmission.com wrote: >>ebiederm@xmission.com (Eric W. Biederman) writes: >> >>> Jiri Pirko writes: >>> >>>>>So this id needs to be globally unique? >>>> >>>> No. It is enough to be unique within a single system. It serves for no >>>> more than to find out 2 ids are same or not, no other info value. >>>> >>>> So when the drivers uses sane ids (like mac for example, or in case of >>>> rocker an id which is passed by qemu command line), the chances of >>>> collision are very very close to none (never say never). >> >>Thinking about what you said a little more. >> >>Two different sources of persistent numbers picking numbers by >>completely different algorithms can give you no assurance that you don't >>produce conflicts. >> >>The switch id as desisgned can not work. >> >>There are expected to be between 2**36 to 2**40 devices in this world. >>Your first switch id is a 64it number. At the very best by the birthday >>pardox predicts there will be a conflict ever 2**32 devices or between >>2**4 and 2**8 devices in the world with conflicts. If the ids are not >>randomly distributed (which they won't be) things could easily be much >>much worse. >> >>That is just good enough the code could get out there and run for years >>before you have the nightmare of having to fix all of userspace. That >>is a nightmare no one needs. >> >>So please remove this broken code, and this broken concept from the >>kernel and go back to the drawing board. > > In that case the phys port id is broken in the same way. Let's rather > think about how to avoid conflicts for both. Given the fact the > conflicts should be avoided only on a single baremetal, that should be > doable (for (bad) example using driver name mixed with driver created > id). No. phys_port_id is not broken in the same way, and phys_port_id does not have the same set of properties. phys_port_id's in practice all have an IEEE prefix that identifies the manufacturer and a manufacture assigned serial number. Aka a mac address or a EUID-64. What the mlx4 ethernet driver is doing retunring a 64bit EUID-64 I don't know. If there are problems in the worst case issues with phys_port_id are fixable by simple driver tweaks, because fundamentally we are working with globally uniuqe identifiers. Well globally unique baring manufacturing bugs in eeproms. I agree with you that the switch id concept can be saved. But I think we should fix switch id before we export it to userspace so we don't have to break userspace later. My intuition says we want something like ifindex, but I am not at all certain how switch id is planned to be used. Given that it is single box I don't expect you are sending it out over the wire. *shrug* Why does switch id need to be persistent? Why can't switch id be property like ifindex? What are the actual requirements. Eric