[ntp:hackers] What does "interface listen wildcard" do?

Danny Mayer mayer at ntp.org
Fri Jul 12 15:59:43 UTC 2013

On 7/12/2013 10:33 AM, Brian Utterback wrote:
> On 07/12/13 09:40, Danny Mayer wrote:
>> If IP_PKTINFO was generally available on all O/S's with all of the
>> information we needed it would have made some things easier but with the
>> resulting problem of how to deal with incoming packets sent to an
>> address that the admin didn't want to have people using.
> The same way we do now, drop it. Remember that we do bind and receive
> packets on the wildcard address, we just drop them.

It's not as simple as that. Admins want to make sure that NTP clients
don't try that address for NTP packets. They actually want it to return
"refused" so that those clients don't try. Accepting and dropping
packets means that something is accepting the packets. Dropping them is
not the same thing at all.

> Look, I think that the time has come to do some re-examination of some
> of the design choices and to decide what the minimum requirements for
> support are and look at doing some re-factoring based on those
> decisions. Maybe we could take a modular approach and hide a lot of the
> implementation details behind an abstraction layer, possibly turn some
> of the design choices plugins.

Yes. I'd like to break ntp_io.c apart again and put different pieces in
different files.

> We have had this same conversation nine years ago and then again five
> years ago. If getting broadcast working again is doable, great. If not,
> I can live with that. If we want to come out with an official "broadcast
> is deprecated, use multicast" document, even better. But how about we
> get down to it, define the minimum requirements and get cracking? We
> keep speculating on whether this or that feature is supported on this or
> that platform, but we don't really know, do we?

Yes. Hopefully that can be considered for the next major release.


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