Re: [Int-dir] side note RFC 4291 2nd par sec. 2.1 LL on loopback

[神明達哉 <[e-mail]>]

At Tue, 16 Apr 2019 12:52:37 +0200,
Alexandre Petrescu <[e-mail]> wrote:

> >  > That RFC4291 section 2.1 says:
> >  > >    All interfaces are required to have at least one Link-Local
unicast
> >  > >    address (see Section 2.8 for additional required addresses).
> >  >
> >  > Sidenote: I think the loopback interface does not have a link-local
> >  > address.  Probably it is not all interfaces that must have at least
> > one ll(
> >
> > Indeed, there's some subtle point here.  RFC4007 somewhat tries to
> > clarifies it:

> Well,  RFC4007 predates RFC4291, so it is little meaningful to say it
> clarifies it.

Could we be stop nitpicking?  I didn't say RFC4007 clarified RFC4291;
I meant it clarified the requirement of having a link-local address on
all interfaces, which I thought was clear from the context.  For that
matter, the above exact same text has existed since RFC2373.  Even
RFC1884 (the very first address architecture RFC) essentially says the
same thing in Section 2.7.

> Maybe we can say that RFC4291 must be updated given all these issues.

> > BTW, whether a loopback interface has an fe80 address is actually
> > implementation dependent.  BSDs usually assign ::1 on a loopback
> > interface while also generating an fe80 address on it:
> >
> > % ifconfig lo0
> > lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
> >      options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6>
> >      inet6 ::1 prefixlen 128
> >      inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2
>
> Ah?  It self-forms that fe80 address without a sysadmin requesting it?

Yes.

> In other OSs like linux, windows, there is no fe80::1 unless the
> sysadmin adds it.
>
> In that sense, this is an additional reason (together with the
> RFC4291-violating fe80:1::1 potentially breaking in BSD) to think that
> RFC4291 and co. are mostly for BSDs.

You're free to think so.  But that doesn't change the fact that
fe80:1::1 violates the RFC, so you'll need to update it if you want it
to be allowed.

Note also that MacOS is derived from BSD in case you don't
remember/know it.  And, in fact it also generates both "fe80::1" and
"::1" on the "lo0" interface.

Anyway, I don't think this discussion affects your draft?  If you want
to continue it, 6man would be a better place, if only to reduce the
noise in the original thread.

--
JINMEI, Tatuya