Some reading on IRIs and IDNs

[Stephane Bortzmeyer]

On Thu, Dec 10, 2020 at 08:12:04PM -0500,
 Gary Johnson <lambdatronic at disroot.org> wrote 
 a message of 69 lines which said:

> 1. Punycode the hostname.

Not always, for the reasons explained in RFC 6055. To summarize: the
application does not always know which name resolution system will be used.

gemini://gemini.bortzmeyer.org/rfc-mirror/rfc6055.txt

> 3. Make a DNS query with the punycoded hostname.

Most applications don't do DNS queries, both because DNS is
complicated and because there are other name resolutions system. They
call a system routine (getaddrinfo() in C) to do the resolution.

> There is also the open question of whether servers should convert
> punycoded hostnames back into unicode hostnames for the purposes of
> virtual hosting (either via SNI or post-handshake). Since at least one
> poster has indicated that the widespread unevenness in DNS support for
> unicode has lead to the need to store A records in their punycoded form,
> this suggests to me that virtual hosting may be performed most
> universally by just directly matching the received punycoded domain
> names.

This is what Apache and Nginx do in the Web world (which does not mean
they are right).