[ntp:hackers] Findinterface

Heiko Gerstung heiko.gerstung at meinberg.de
Fri Jun 10 02:03:16 PDT 2005


Hi John,

John Hay schrieb:

>On Fri, Jun 10, 2005 at 08:41:32AM +0200, Poul-Henning Kamp wrote:
>  
>
>>In message <20078.1118385538 at www.ntp.org>, Harlan Stenn writes:
>>    
>>
>>>Heiko,
>>>
>>>I would have to Dig Deep into the archives, but what I recall is that Dave
>>>has looked in to this and says it is Required for the public key stuff; we
>>>must know the interface on which to send the response.
>>>      
>>>
>>I think this is very suspect info.
>>
>>It should be enough to send the packet on a normal socket specifying
>>a from address identical to the to address in the received packet.
>>    
>>
>
>You might still need a little more info if you start the "session",
>iow you don't react to a packet. Also reacting to broadcast and
>multicast packets will need more interface info.
>
>  
>
Ok, given that condition I'd say that finding out the interface whenever 
you want to start a session would be the best idea. Very few people use 
the public key functions these days and I think it's not necessary to 
try to find out something for each and every server line which is only 
used by a small percentage afterwards.

My specific interest in that started when a customer of us who is still 
using NT4-SP6 servers (don't ask ...) found out that in recent versions 
of NTP this mechanism seems not to work anymore under NT.
See https://ntp.isc.org/bugs/show_bug.cgi?id=450 ...

Maybe it would be OK to simply skip the interface detection for every 
association which does not need public key crypto magic.

Kind regards,
Heiko


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