[ntp:questions] Pool returns IPv6 address to IPv4 query

Brian Utterback brian.utterback at oracle.com
Tue Nov 19 14:02:28 UTC 2013

Just as a point of interest, one of the most heated debates I have ever 
been involved in internally here at Oracle was concerning whether 
getaddrinfo (as defined by POSIX) should or should not return IPv6 
addresses if the system only has IPv4 interfaces and/or only the 
loopback IPv6 address. The getaddrinfo call was designed to work 
efficiently on both dual stack and single stack systems, but the wording 
in the standard is slightly ambiguous especially considering the case 
that the host you are looking up might actually belong to the system you 
are on.

On 11/18/13 16:01, Danny Mayer wrote:
> On 11/18/2013 2:44 PM, A C wrote:
>> On 11/18/2013 11:18, Majdi S. Abbas wrote:
>>> 	The fact that it's even trying means you didn't start ntpd with
>>> -4, and the host has at least one IPv6 interface (this might be as
>>> simple as v6 enabled on the loopback.)
>>> 	So, either ensure that v6 is fully disabled on the host, or add
>>> -4 to your ntpd startup parameters.
>> lo0 did indeed have a v6 address configured (hadn't noticed) though my
>> eth0 does not.  I would not have expected ntpd to use v6 if any one
>> interface did not have it.  Up until this point it never returned a v6
>> address on lookup so that's probably why I never noticed that v6 had
>> been enabled again (recent upgrade of OS).  I've disabled all v6 now and
>> added -4 for good measure.
> ntpd will use whatever addresses it gets back from DNS. If you don't
> specify that you only want IPv4 addresses and it gets an IPv6 address it
> will attempt to use it. This is a DNS and configuration issue not an ntp
> issue. This is true of all applications (whether client or server) these
> days.
> Danny
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Always code as if the guy who ends up maintaining your code will be a
violent psychopath who knows where you live. - Martin Golding
Brian Utterback - Solaris RPE, Oracle Corporation.
Ph:603-262-3916, Em:brian.utterback at oracle.com

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