Re: nscd and IPv6

[Philip Blundell <Philip dot Blundell at pobox dot com>]

>I think there is much more IPv6 code in the glibc which is bogus, for example 
>in the NIS NSS modules.

Very possibly.  Do point out anything you aren't sure about.  Now that 
distributions such as Debian are starting to work on IPv6 support this code 
will be exercised for the first time and it's likely there will be all sorts 
of bugs.  It doesn't help that the IPv6 API has been a moving target for the 
last few years.

>One question about gethostbyname: If I use a hostname which has
>only IPv6 addresses in /etc/hosts, this call always fails. Is
>this correct ? 

Yes.  You should get back `No data associated with name' or something similar.
The reason is that this API provides no way for the caller to specify what 
sort of data it wants - old programs may fail if they are unexpectedly handed 
IPv6 addreses.  If you want to be able to receive IPv6 information you should 
use getaddrinfo or the new getipnodebyname call (which is a replacement for 
gethostbyname2 and is not yet implemented in glibc as far as I know).  The 
latter of these does allow you to request that v4 addresses should be mapped 
to v6 on a per-call basis.

>And we use:
>  if (_res.options & RES_USE_INET6)
>
>When will _res.options be set ? And how can a user change this ?

See RFC2133 for the gory details of this option.  It was intended that user 
applications would mess directly with _res.options.  Fortunately this is 
pretty much obsolete now and should almost certainly not be used.

p.