Re: [Ntp] Leap second draft

[Warner Losh <[e-mail]>]

On Thu, Jan 23, 2020 at 4:04 PM Watson Ladd <[e-mail]> wrote:

>
>
> On Wed, Mar 27, 2019, 9:47 AM Daniel Franke <[e-mail]> wrote:
>
>> I'm writing up an I-D clarifying how NTP implementations are to behave
>> in proximity to a leap second and also introducing an extension field
>> that provides better leap-second-related information than is
>> expressible using header fields alone, including giving the TAI-UTC
>> offset.
>>
>> Karen, you mentioned a possible CfA for
>> draft-stenn-ntp-extended-information if Harlan revises it to comply
>> with RFC 7822 (-04 does not appear to comply). Our two drafts are
>> partly redundant in purpose since they both provide TAI-UTC offset and
>> we won't want to adopt both. Of course I think mine is the one we
>> should adopt, but I'll strive to get a -00 submitted promptly so that
>> they can be considered side-by-side without unduly delaying Harlan's
>> CfA.
>>
>
> Apologies for the necromancy but someone at work just asked me which
> second is repeated in an NTP timestamp and to make sure all our sources use
> the right one.
>

NTP timestamp repeats the last second of the day. Once without the leap bit
set and then again with it set.

POSIX doesn't specify, and so systems choose a number of different ways of
coping (repeat the last second of the day, repeat the first second of the
next day, freeze time during leap second, do some crazy smear to pretend
reality matches the POSIX spec, kernel panic, etc).

Warner