[ntp:questions] Re: ntpd transmit timestamp precision

David L. Mills mills at udel.edu
Wed Feb 15 04:37:15 UTC 2006


Please don't copy my presonal mailbox with postings to this list. I 
routinely throw them away without reading.

See ntp-dev/libntp/systime.c line 85.


Damion de Soto wrote:
> Hi Guys,
> Brian Utterback wrote:
>> I think that this is Damion's point. If you look at the code itself,
>> the fuzz code is not used if:
>> 1. You are using clock_gettime.
>> or
>> 2. You are using getclock
>> or
>> 3. You are using the simulator.
>> So, the fact that the simulator is doing okay is irrelevant, since it 
>> does not use the fuzz code. But more to the point, the clock_gettime 
>> and getclock functions claim to return nanoseconds, so there are only two
>> bits available to fuzz, so the code does not bother to fuzz those last
>> two bits. Damion's point is that the actual precision of the clock
>> on his system is much more coarse, so more bits are really 
>> non-significant and should be fuzzed, but they are not.
> I have just disabled the use of clock_gettime() and am still not seeing
> any bit randomization/fuzz. (Athough I'm sure I saw some yesterday....)
> Where exactly is the code to fuzz the gettimeofday() value?
> I can't find anything obvious.
> Thanks,

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