From: Alan Johnson <alan.wayne.johnson@...>
Date: 2008-11-29T04:21:54+09:00
Subject: [ruby-core:20154] Re: [Bug #743] Socket.gethostbyname returns odd values

On Wed, Nov 26, 2008 at 5:04 PM, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
> Hi,
>
> In message "Re: [ruby-core:19989] [Bug #743] Socket.gethostbyname returns odd values"
>    on Wed, 19 Nov 2008 18:58:25 +0900, Alan Johnson <redmine@ruby-lang.org> writes:
>
> |File bug743.patch added
> |
> |gethostbyname/gethostbyaddr seem to work oddly in many respects.
> |
> |1) Socket.gethostbyname works differently than TCPSocket.gethostbyname.  The latter doesn't seem to have any real purpose for existing.
> |2) The alias array is always empty.
> |3) When a host has multiple IP addresses, they are tacked onto the end of the array.  To more faithfully represent a struct hostent, the fourth array member should itself be an array of addresses (matching h_addr_list).
> |
> |These problems mostly seem to stem from the fact that instead of faithfully calling the underlying library implementation, they ALSO call getaddrinfo.
>
> It's implemented using getaddrinfo because at the time of coding (long
> ago) it was virtually only way to support IPv6 addresses.  And you
> patch seems destruct IPv6 support.  I'd happy to address above issues,
> but we are not going to disable IPv6 support.
>
>                                                        matz.
>
>

(Replying via mailing list because the topic has strayed from that of
the bug report.)

Forgive me if this sounds like a stupid question ... why do you care
about ipv6 support in gethostbyname/gethostbyaddr?  These functions
(the POSIX ones, not ruby) are known for having poor ipv6 support,
which is a major reason why getaddrinfo/getnameinfo exist, and those
should be the preferred methods used by anyone needing ipv6.  Trying
to retroactively add support to gethostbyname leads to nonsensical
results like the following:

irb(main):002:0> Socket.gethostbyname('host1.example.com')
=> ["host1.example.com", [], 2, "\xC0\xA8\x01\x02",
"\xC0\xA8\x01\x03", "\xC0\xA8\x01\x01",
"\xFC\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01",
"\xFC\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02",
"\xFC\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03"]

Note that the address family is reported as 2 (AF_INET) but three of
the results do not belong in that address family.

As I understand it, the Socket class exists to provide low level
support for the underlying socket implementation.  It is confusing for
Ruby's implementation of a function to behave differently from the
platform's implementation.

-- 
Alan