[ntp:questions] nptq -p slowness

Danny Mayer mayer at ntp.isc.org
Sun Jan 28 21:20:43 UTC 2007


Serge Bets wrote:
> Hello everybody,
> 
> With ntp 4.2.4, I strangely get a very slow display of the ntp -p
> billboard. Example:
> 
> | $ ntpq -p
> |      remote           refid      st t when poll reach   delay   offset  jitter
> | ==============================================================================
> |  SHM(0)          .DCF.            0 l    -   64    0    0.000    0.000   0.004
> | *LOCAL(0)        .LOCL.           8 l   60   64  377    0.000    0.000   0.004
> 
> This takes more than a minute to display, line by line. A named querylog
> shows that it's due to DNS resolver delays until timeout. It seems that
> when showing a refid, ntpq does a DNS A request on the name
> "DCF.<localdomain>", gets immediatly a "does not exist" authoritative
> answer. Then it does an A request on "DCF" alone, without answer until
> timeout. Then only ntpq displays the line and ".DCF." with the added
> dots around. The same happens for other refids LOCL, INIT, and such.
> However when the refid is an ntp server, it's displayed as dotted quad
> immediatly, without delay.
> 

This is wrong and needs to get fixed.

> Now I have 2 questions:
> 
>  - Why does ntpq request A on refids? I remember the good old reverse
> PTR resolution long ago when refids were IPv4s. But why an A?

Are you looking at the wire and seeing these packets? If so please file
a bug report. As you said it shouldn't be attempting DNS lookups for these.

> 
>  - What's broken on my system so that not qualified hostnames are not
> considered local (my named forwards those A requests to my provider's
> servers)?
> 
Fully qualified domain names should always be used to avoid these problems.

What does your named.conf look like? You have to be explicit to request
that it forward zones for lookups. This part really belongs in
bind-users (comp.protocols.dns.bind if you prefer newsgroups).  named
will *not* qualify names and will take whatever it's given. dig doesn't
do that either unless you use the +search option. That's deliberate.

Danny
(Swapping his NTP hat for his BIND hat)
> 
> Thankfully, Serge.




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