[ntp:questions] Is there something with greater detail on "interface" besides the manpage?

Rob nomail at example.com
Wed Nov 20 12:37:38 UTC 2013

Harlan Stenn <stenn at ntp.org> wrote:
> Rob writes:
>> Harlan Stenn <stenn at ntp.org> wrote:
>> > Rick Jones writes:
>> >> Harlan Stenn <stenn at ntp.org> wrote:
>> >> > You might want:
>> >> 
>> >> >  interface ignore all
>> >> >  interface listen     # if you want localhost ntpq to work
>> >> >  interface listen a.b.c.d       # enumerate the IPs you want to use
>> >> 
>> >> Thanks.  I take it then that wildcard charaters in matching on
>> >> interface names aren't a go :)
>> >
>> > Not yet, as best as I can recall.
>> >
>> >> My further complication is these systems get their IPs via DHCP (I
>> >> should have listed that in the first place, sorry) and some are bonded
>> >> and some are not bonded, but the component names of the interfaces in
>> >> the bond(s) are the same "namespace" as when they are not bonded.  For
>> >> example I may have systems with a bond0 using eth2 and eth3 and some
>> >> systems just using eth2.  I *may* though be able to split the config
>> >> files between such systems - that remains to be determined and if not
>> >> is, arguably a failing at my end.
>> >
>> > How much info that NTP would care about would come from DHCP?
>> - the address of the local system
>> - the addresses of the local NTP servers
> So all of the other information (bonded interfaces, etc.) are handled
> locally?  Does ntpd listen using the address of the local system or
> some other address?

That is a different subject.   You asked what info from DHCP could be
useful to NTP.  Note that ntpd does not use any info from DHCP, this has
to be hacked by integrators who have to modify ntpd configuration on the
fly after receiving a DHCP lease (which often leads to frustration for
people who want to change the configuration and don't know about the
mechanism implemented by the system integrator)

w.r.t. your current question:

It looks like ntpd enumerates all the local interfaces and creates sockets
for all the addresses it can find locally.

Why it does that, is beyond me.  It should use a single socket with
the wildcard address, until configuration directs it to listen only
on specific addresses.

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