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

Danny Mayer mayer at ntp.org
Tue Nov 19 20:40:26 UTC 2013


On 11/19/2013 2:47 PM, Rick Jones wrote:
> Brian Utterback <brian.utterback at oracle.com> wrote:
>> On 11/19/2013 12:33 PM, Rick Jones wrote:
> 
>>> Later, when interfaces started getting auto-configured, local
>>> scope IPv6 addresses, there was a call to change that to be "don't
>>> return IPv6 addresses unless there is a better-than-local-scope
>>> IPv6 address assigned."  Started causing me all manner of pain in
>>> netperf :( Not sure where that stands now in the Linux world.
>>>
>>> rick jones
> 
>> Yes, that was the issue. Further complicating it was what do you
>> return if you have no IPv6 interfaces and you set AI_ADDRCONFIG and
>> you pass in a literal IPv6 address.  The problem is that getaddrinfo
>> replaces both gethostbyname and inet_aton, each of which you might
>> expect to have different results in that case. We had people citing
>> two RFC's and the ipng working group mailing list. Great fun.
> 
> That passing-in a literal IPv6 address is precisely where I first
> started noticing problems with netperf.  For ages (in Internet Time at
> least) it "just worked" even when all I had were local-scope
> (link-scope?) IPv6 addresses configured.  Then someone made a libc
> change and life became Quite Unpleasant (tm).

You should not be using literal IP addresses of either flavor without
also setting the AI_NUMERICHOST flag otherwise it tries to do a DNS
lookup. That's poorly written code otherwise.

Danny



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