Re: ADDRINFO use [Was: Windows breakage with cr_net.h]

Le mar 22 jun 2004 à 08:31:25 -0700, Mike Houston a tapoté sur son clavier :
> Samuel Thibault wrote:
> >Le lun 21 jun 2004 à 17:23:28 -0700, Mike Houston a tapoté sur son clavier 
> >:
> >>The other oddity is that the changes to support IPv6 seem to always kick 
> >>us into using ADDRINFO on recent versions of Linux.  This works,
> >
> >Of course it does, to support IPv6 whenever available. getaddrinfo()'s
> >interface was specially design to always work: the dns lookup may
> >report ipv4 and ipv6 addresses, getaddrinfo() gives them all. If an
> >ipv6 address is given but doesn't work either because lack of support
> >in the kernel (ENOAFSUPPORT) or for network reasons, the connection
> >will revert back to ipv4.
> 
> I understand why it works, I just thought it was odd to ALWAYS use it.

The getaddrinfo() way is quite better in many ways: since it may return
several addresses, hosts with multiple ips may be correctly handled:
every ip will be tried until one works.

> some TOE's and most of the IP interception routines for highspeed
> networks only work if AF_INET is used.

Ah, ok. For this, just make sure that dns replies don't give any ipv6
address, and it will work. If needed, use a special dns entry.

> My point is whether we should use AF_INET in general and detect
> IPv6 another way.

The user may set IPv6 addresses by hand, but for this, getaddrinfo()
must be used. Using getaddrinfo() replies for determining whether
IPv6 is possible (or asked by hand) really is the fine way.

> Is anyone using IPv6?

Yes, some people at the INSA of Lyon actually contacted me because they
needed IPv6 working.

> How often does anyone need to run IPv6 across a cluster?

Well, IPv6 is actually in several ways more efficient that IPv4, and QoS
is quite better supported.

> Is it really just for remote stream support?

I guess people at INSA use Chromium over VTHD, a very high bandwidth
WAN used for research. IPv6's QoS is quite useful there for instance.

Regards,
Samuel Thibault


-------------------------------------------------------
This SF.Net email sponsored by Black Hat Briefings & Training.
Attend Black Hat Briefings & Training, Las Vegas July 24-29 - 
digital self defense, top technical experts, no vendor pitches, 
unmatched networking opportunities. Visit www.blackhat.com