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Subject: Re: [ISC-Bugs #36101] IDN support in host/dig/nslookup using GNU libidn(2)
Thread-Index: ZFxjTXqhTd5b5wtfLJ9nk6+jKqW6Gg==
Date: Tue, 27 May 2014 12:33:10 -0400 (EDT)
Thread-Topic: IDN support in host/dig/nslookup using GNU libidn(2)
To: bind-suggest@isc.org
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From: Tomas Hozza <thozza@redhat.com>
RT-Message-ID: <rt-3.8.6-35155-1401208394-747.36101-0-0@isc.org>
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----- Original Message -----
> > I'm not sure if there is already a ISC-Bugs # number for this. However
> > I would like to know if you would be interested in adding support
> > for libidn.
> 
> Yes.

Great!

> > - introduce new configure option to turn on the usage of GNU libidn
> >   (something like --with-gnu-libidn)
> > - use libidn2 for IDN -> ACE conversion (as libidn2 suppoerts IDNA2008 [1]
> >   whereas libidn supports only IDNA2003)
> > - use libidn for ACE -> IDN conversion where needed (as libidn2 apparently
> >   does not include support for this)
> 
> Pardon my confusion here, but do you mean that two different versions
> of libidn would be in use at the same time?

Well I have to admit that I was also little bit confused when looking at the idnkit
code in dighost.c.

The process seems to work like this:
1. the domain name from the CLI is converted to UTF-8
2. the origin is converted to UTF-8
3. UTF-8 domain name and UTF-8 origin are joined.
4. the joined domain name is conveted to the translated IDN name (ACE)

5. there is output_format() function for converting the translated
   IDN ascii (ACE) name to locale when printing it to the CLI.

Now the "old" a.k.a. IDNA2003 library "libidn" has all the necessary
functions (part of stringprep.h) for conversions of locale <-> UTF-8 <-> ACE.

However the libidn2 (IDNA2008) library has only functions for conversion
of locale -> translated IDN as UTF-8 and UTF-8 -> translated IDN as UTF-8.

But I think there is still need for the functions to convert the translated IDN in UTF-8
to ACE, locale -> UTF-8 without the IDN translation, ACE -> locale (in output_filter).

There is library libunistring that could solve this, but it is also yet another
library.

Maybe it would make sense to add compile time option for libidn, which would be used
by default if compiled with it. Then provide yet another compile time option to use
also libidn2 in addition to the libidn library and make the usage of it dependent on
some runtime option (like -8 meaning IDNA2008 or something different).

I'm open to any suggestions. Maybe I missed something...

Thanks!

Regards,
-- 
Tomas Hozza
Software Engineer - EMEA ENG Developer Experience

PGP: 1D9F3C2D
Red Hat Inc.                               http://cz.redhat.com