Re: getaddrinfo and AF_UNSPEC w/ IPv4/6 messes up ai_canonname?

[Pekka Savola <pekkas at netcore dot fi>]

On Sun, 25 Aug 2002, Ulrich Drepper wrote:
> Pekka Savola wrote:
> >  1) with PF_INET, this does not happen (CNAME entry is returned, not
> > addresses -- at least as far as I could see): thus the current behaviour
> > does not seem the same between address families.  
> 
> I don't really know what you mean.  For PF_INET no IPv6 addresses are 
> returned so you cannot mean this.  The code used is the same if PF_INET 
> or PF_UNSPEC is used and so numeric addresses would also be returned if 
> the internal gethstbyaddr calll fails.

What I mean is if I modify the test code to set 'hints.ai_family =
PF_INET', the code does not return numeric _IPv4_ addresses but only the
name.

In the contrary, with 'hints.ai_family = PF_INET6' or PF_UNSPEC, the code 
returns first IPv6 addresses and then the name (with PF_UNSPEC).

So it appears with PF_INET6 does not return a name at all.  It appears to 
me that CNAME is associated with PF_INET here.

The name should always be returned first, if addresses should be returned
at all.  (At least intuition tells me the the user is looking for a
canonical *name* not addresses).

> >  2) (not really motivation, but still..) e.g. BSD libc does not return
> > addresses (the test works as "expected"); I haven't checked other
> > implementations.
> 
> That's indeed no motivation.  But you could do one thing: look at the 
> entire list of records returned on a BSD system.  Is the one you expect 
> really the only one?  Or is it just a matter of ordering.

On BSD system, the output of the modified code is:

host: ftp.kame.net, canon (if any): kame220.kame.net
host: ftp.kame.net, canon (if any): kame220.kame.net
host: ftp.kame.net, canon (if any): kame220.kame.net

On Glibc 2.2.5, it was:

host: ftp.kame.net, canon (if any): 2001:200:0:4819:210:f3ff:fe03:4d0
host: ftp.kame.net, canon (if any): 3ffe:501:4819:2000:210:f3ff:fe03:4d0
host: ftp.kame.net, canon (if any): kame220.kame.net

I don't know whether this behaviour is standardized or in the process of 
being done at the moment.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords