Re: Please support download setup-x86_64.exe on IPv6-only network

[Lee <ler762@gmail.com>]

On Tue, Nov 21, 2023 at 12:35 AM Brian Inglis wrote:
>
> On 2023-11-20 17:45, Lee via Cygwin wrote:
> > On Mon, Nov 20, 2023 at 7:13 PM Backwoods BC via Cygwin wrote:
> >>
> >> On Thu, Nov 16, 2023 at 12:41 PM Brian Inglis via Cygwin wrote:
> >>> The whole IP v4 internet is available as a compatibility subnet ::ffff:0:a.b.c.d
> >>> on IP v6, so there is no excuse for not supporting interconnection, as it will
> >>> be required until the last backbone routers drop IP v4 support.
> >>
> >> Just a small correction for the mail archives as this appears solved.
> >> The correct IPV6 address for the IPV4 address range is
> >> ::ffff:a.b.c.d  (no '0')
> >
> > If you're going for correcting the record, let's make it correct.
> > ::ffff:a.b.c.d is not a solution for IPv6 => IPv4 interconnection over
> > the Internet.
> >
> > from:  https://www.rfc-editor.org/rfc/rfc5156
> >
> > 2.2.  IPv4-Mapped Addresses
> >
> >     ::FFFF:0:0/96 are the IPv4-mapped addresses [RFC4291].  Addresses
> >     within this block should not appear on the public Internet.
>
> These internal addresses are used by dual stack hosts to allow clients or
> servers to handle connections to IPv4 hosts the same as IPv6 hosts.

I think that at best you're terribly confused, but let's play this out.

> Whereas ::ffff:0:0:0/96 == ::ffff:0:a.b.c.d allows IPv6 only hosts without
> assigned IPv4 addresses to connect to IPv4 only hosts via SIIT see:
>
>         https://www.rfc-editor.org/rfc/rfc7915 Stateless IP/ICMP Translation.

I did see RFC 7915.  I searched for 'ffff' and there were no matches.

You need something else to back up your claim that
  ::ffff:0:0:0/96 == ::ffff:0:a.b.c.d allows IPv6 only hosts without
  assigned IPv4 addresses to connect to IPv4 only hosts.

And please explain how an ipv6 host is going to get a packet with a
0::/8 address delivered across the internet.

see:  https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml

An ipv6 prefix of 2000::/3 is defined as Global Unicast.  In other
words, an ipv6 unicast address MUST start off with 2000::/3 to be
routed across the Internet.

And look at footnotes 3 and 4
::ffff:0:0/96 reserved for IPv4-mapped Address [RFC4291].
0::/96 deprecated by [RFC4291]. Formerly defined as the
"IPv4-compatible IPv6 address" prefix.

Nothing about ::ffff:0:0:0/96

Regards,
Lee