Re: After enabling IPv6 curl github.com fails, succeeds with IPv4

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Wed, 22 Jul 2026 08:37:13 +0200
    From:        Martin Husemann <martin%duskware.de@localhost>
    Message-ID:  <amBlGfpvQjsnS39G%big-apple.aprisoft.de@localhost>

  | P.S.: what we didn't find out so far: why is this related to enabling
  | IPv6 in your setup?

github.com has an IPv4 addr, which would be found before trying adding
any suffixes to that.   It has no v6 addr, so when that is sought, nothing
is found, and the resolver attempts to add the domain part of the hostname,
and finds github.com.in.

Things would perhaps be nicer if the IETF had added (something like this
was once suggested) an "ADDR" type query, which would return both v4 and
v6 (and anything else qualifying a network address which might exist).
But they didn't (meta queries like that have issues with lifetimes and
negative responses).

I agree, the naming of what is used in this general area is very ambiguous,
everything looked up in the DNS is a domain name in that sense, but that's
not what is meant in this context, where your "domain" is the thing you
register with some domain naming registry, and then you allocate hostnames
(or sub-domains if you want) inside that domain.   A hostname's domain in
this sense is everything after the first '.'.   In an internal DNS context
that distinction is absurd, but it is also ancient, and is the way people
tend to think.

kre