[Pkg-utopia-maintainers] Bug#587961: Bug#587961: avahi-daemon: patch for #517160 affects more than just reflector

[Lennart Poettering]

On Sun, 11.07.10 10:44, Julien BLACHE (jblache at debian.org) wrote:

> Michael Biebl <biebl at debian.org> wrote:
> 
> Hi Michael,
> 
> > I just uploaded 0.6.26-1 which contains a fix for
> > http://avahi.org/ticket/300
> >
> > Could you please test if that also solves your particular issue and
> > report back.
> 
> Looking at the code again, the patch does the right thing and the code
> is now correct in its handling of link local addresses wrt reflector.
> 
> The remaining issue is that avahi should be better at choosing the IPv4
> address it sends back to the client when resolving a service. Working
> IPv4 LL is all but a given.
> 
> I think avahi should not return an IPv4 LL address when a global address
> is also advertised if the host doesn't have a link local address
> configured on the interface avahi got the mDNS response from.

Hmm, if I parse this correctly then you have two machines. One running
some mDNS stack that's not Avahi which announces both an IPv4LL and a global
address. And another one which runs Avahi and when contacting the first
machine ends up using the IPv4LL address of the first one, and you dont
want that to happen? Is that correct?

Avahi tries to be smart with the addresses it announces, and it only
announces one address at a timne, and picks the best local address it
can find for that. (i.e. preferring gloabl addresses over IPv4LL if both
are available).

Now, for the A/AAAA records it receives from other hosts it will just
return to the resolving applications the first one the hosts sends. This
is kinda mandated by the resolving scheme which basically says "browse
for an A/AAAA record and return the first one you find".

Or in other words: it should be the job of the announcer to pick the
best address to announce, not the lookup client to pick the best address
it finds. Because the former can have complete knowledge of what is
available and the latter cannot.

What really puzzles me though is why this is even a problem. Doesn't
Debian set up the IP4VLL routes properly? i.e. see:
http://avahi.org/wiki/AvahiAutoipd

If those routes are in place it shouldn't matter much which address
Avahi returns to the lookup clients, because all are equally usable.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.