From: Daniel Berger <djberg96@...>
Date: 2002-09-01T04:57:33+09:00
Subject: Re: gethostbyname() requires reverse lookup to work?

ts wrote:

>>>>>> "D" == Daniel Berger <djberg96@attbi.com> writes:
> 
> D> Couldn't you simply check RES_USE_INT6 and call gethostbyname or
> D> gethostbyname2 as appropriate?  I'm looking at Stevens, "Unix Network
> D> Programming", p.240-249
> 
>  RFC 2553
> 
> 6.1 Nodename-to-Address Translation
> 
>    The commonly used function gethostbyname() is inadequate for many
>    applications, first because it provides no way for the caller to
>    specify anything about the types of addresses desired (IPv4 only,
>    IPv6 only, IPv4-mapped IPv6 are OK, etc.), and second because many
>    implementations of this function are not thread safe.  RFC 2133
>    defined a function named gethostbyname2() but this function was also
>    inadequate, first because its use required setting a global option
>    (RES_USE_INET6) when IPv6 addresses were required, and second because
>    a flag argument is needed to provide the caller with additional
>    control over the types of addresses required.
> 
> 
> 
> Guy Decoux

Ok, but the question I have to ask is whether or not this actually affects 
anyone.  Looking through the Perl 5.8 source code, I don't even *see* any 
refernce to gethostbyname2, although they use the reentrant functions where 
available.

Using Google, I searched through the comp.lang.perl.misc archives.  With 
over 10 years of posts, I found exactly 31 posts regarding IPv6, and NONE 
of them (that I saw) have any complaints with regards to incompatibility 
and/or thread problems with IPv6 (although, I realize Perl didn't really 
support threads until recently).  I also couldn't find a single reference 
to RFC 2553.

My point is, I think the code should be written so as not to worry about 
those (very?) rare cases where it might fail with regards to IPv6.  I think 
reverse lookups are likely to be a much more prevalent cause of failures.

Just my .02

Regards,

Dan