vfs_fruit: Time Machine/FULLSYNC: add mDNS/DNS-SD advertisement

[Ralph Böhme]

On Sun, Jul 23, 2017 at 02:31:20AM -0700, Omri Mor wrote:
> I’ve looked into it a bit further.  It looks like dns_sd support was never
> exposed in Waf build and was only available in autoconf.  Autoconf was removed
> four years ago in cd4b413; I only found FreeBSD to be patching in dns_sd
> support to the Waf build (more below).  When I added —enable-dnssd as an
> option to the Waf build (defining WITH_DNSSD_SUPPORT and linking to Avahi’s
> dns_sd compatibility library), the build broke: source3/client/dnsbrowse.c
> attempts to TALLOC_FREE a nonexistent variable ‘fdset’.  There *are* reference
> to an (unused) fdsetz variable, but it is defined as an int, not a pointer.

<https://svnweb.freebsd.org/ports/head/net/samba46/files/patch-source3__client__dnsbrowse.c?view=markup>

> That enabling dns_sd results in compilation errors signifies to me that *no
> one* is using it.  Working around the problems in dnsbrowse.c (by commenting
> out the code), dnsregister.c does exactly what I expected it to do: deregister
> the service almost immediately.
> 
> In short, all support for dns_sd in Samba appears to be broken and is not
> being maintained.

Looks like. But at least FreeBSD has patches so it might be working there and
someone might be using it.

> There was a bug report about the missing dnssd switch from Waf, as well as the
> dnsbrowse.c compilation problems on the FreeBSD bugtracker:
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=183885
> <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=183885> I found that
> through a somewhat-related bug (11628,
> https://bugzilla.samba.org/show_bug.cgi?id=11628
> <https://bugzilla.samba.org/show_bug.cgi?id=11628>).  Volker responded to that
> one, but it appears that the submitter never followed up and thus the patch
> was never upstreamed.
> 
> FreeBSD is actively using dns_sd/mDNSResponder in their Samba builds, but they
> patch in support.  They also ship Avahi, so removing dns_sd wouldn’t impact
> them much.  What are your thoughts on simply removing the dns_sd code?

I have no idea. As long as it doesn't hurt or cause actuall work I'd say let's
keep it. Picking up the patches from FreeBSD would be nice.

-slow