Standardized IPv6 ULA from PublicKey

[Arti Zirk]

On E, 2020-06-29 at 14:15 +0200, Toke Høiland-Jørgensen wrote:
> In general I'd say that deviating from the RFC needs a good reason.
> Expanding the number of bits we can use for the identifier may be a
> good reason to expand the LL interface ID width (although I'm not
> actually too worried about collisions even if we only use 64 bits).

Few more counter arguments against expanding identifier length:

1. There is a rejected errata 4406 that wants to do this
https://www.rfc-editor.org/errata/eid4406

2. FreeBSD and probably other *BSD/macOS use those unused 56 bits to
store the link scope_id. And support nonstandard fe80:1::30/64 notation
instead of fe80::30%1/64 to specify the scope.
https://stackoverflow.com/a/5891805/2303328
https://github.com/freebsd/freebsd/blob/76f9308e3e2b80e95630efcdd994f3c133806bf4/share/doc/IPv6/IMPLEMENTATION#L427
https://github.com/freebsd/freebsd/blob/e9a39e0c3c22543812afd4de74d1d0ad6782100b/sys/netinet6/scope6.c#L363