From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38608) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTUVw-0005xS-I8 for qemu-devel@nongnu.org; Wed, 10 Feb 2016 08:09:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTUVs-0001jb-5a for qemu-devel@nongnu.org; Wed, 10 Feb 2016 08:09:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42603) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTUVr-0001jK-W9 for qemu-devel@nongnu.org; Wed, 10 Feb 2016 08:08:56 -0500 Date: Wed, 10 Feb 2016 13:08:49 +0000 From: "Daniel P. Berrange" Message-ID: <20160210130849.GB18383@redhat.com> References: <84232dbd5f99c4d811f64a2451df894220efe6a2.1454927009.git.samuel.thibault@ens-lyon.org> <56BB215E.6000702@redhat.com> <20160210124522.GD6020@var.bordeaux.inria.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160210124522.GD6020@var.bordeaux.inria.fr> Subject: Re: [Qemu-devel] [PATCHv7 9/9] qapi-schema, qemu-options & slirp: Adding Qemu options for IPv6 addresses Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Samuel Thibault Cc: Thomas Huth , 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 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. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|