Re: [Qemu-devel] [PATCHv7 9/9] qapi-schema, qemu-options & slirp: Adding Qemu options for IPv6 addresses

[Samuel Thibault]

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.

Samuel