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