From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33860) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTxsf-00075W-Vc for qemu-devel@nongnu.org; Thu, 11 Feb 2016 15:30:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTxsb-0005tG-62 for qemu-devel@nongnu.org; Thu, 11 Feb 2016 15:30:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43226) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTxsb-0005t3-0N for qemu-devel@nongnu.org; Thu, 11 Feb 2016 15:30:21 -0500 References: <84232dbd5f99c4d811f64a2451df894220efe6a2.1454927009.git.samuel.thibault@ens-lyon.org> <56BB215E.6000702@redhat.com> <20160210124522.GD6020@var.bordeaux.inria.fr> <20160210130849.GB18383@redhat.com> From: Thomas Huth Message-ID: <56BCEF53.6090400@redhat.com> Date: Thu, 11 Feb 2016 21:30:11 +0100 MIME-Version: 1.0 In-Reply-To: <20160210130849.GB18383@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv7 9/9] qapi-schema, qemu-options & slirp: Adding Qemu options for IPv6 addresses List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" , Samuel Thibault Cc: zhanghailiang , Li Zhijian , Stefan Hajnoczi , Jason Wang , qemu-devel@nongnu.org, Vasiliy Tolstov , Dave Gilbert , Yann Bordenave , Gonglei , Jan Kiszka , Huangpeng , Yang Hongyang , Guillaume Subiron On 10.02.2016 14:08, Daniel P. Berrange wrote: > On Wed, Feb 10, 2016 at 01:45:22PM +0100, Samuel Thibault wrote: >> Thomas Huth, on Wed 10 Feb 2016 12:39:10 +0100, wrote: >>>> + if (!vprefix6) { >>>> + vprefix6 = "fec0::"; >>> >>> Site-local prefixes have already been deprecated (see rfc3879) ... would >>> it be feasible to use a ULA prefix instead (fd00::/8, >>> see rfc4193) ? >> >> The question is which ULA. Ideally we'd take a random one at each qemu >> startup, but then it's a pain for users to type IPs by hand, all the >> more so when it changes at each qemu startup. Another way is to have the >> same in all qemu instances, hardcoded in qemu, i.e. like >> >> https://xkcd.com/221/ >> >> proposes. That's still a pain to type, even if it is always the same, >> and can still (since it's the same for all qemu instances) pose some of >> the problems raised by rfc3879. The rfc1918 addresses we use in qemu >> for ipv4 have the same issues. That's why I considered that the issues >> mentioned by rfc3879 would not be relevant to qemu, and be simpler to >> just use fec0::, and let the user chose his public or ULA prefix if he >> needs it. > > I'm inclined to agree that fec0:: is a better bet for QEMU's default > usage, despite rfc3879. As you say it is no worse than what we have > with IPv4, and IMHO it is preferrable to using a fixed ULA since that > would be non-compliant with the RFC which requires randomness. Ok, then let's go with fec0:: first. We still can change it later if necessary. Thomas