Re: [Tails-dev] htpdate - Why the perl version?

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Autore: intrigeri
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To: AK
CC: The Tails public development discussion list
Oggetto: Re: [Tails-dev] htpdate - Why the perl version?
Hi,

AK wrote (02 Jun 2014 09:10:35 GMT) :
> So you're saying that there's no daemon in the background that keeps
> adjusting the clock? It only adjusts once?


Exactly. https://tails.boum.org/contribute/design/Time_syncing/ has
the details.

> If that's the case, then yes it does increase monotonically, though
> it you wouldn't be able to leave it on for long...


I'm curious why :)

>> I don't think it will always increase monotonically even after the
>> initial sync. If the frequency of the cpu gets too fast, then the
>> clock will be ahead, so it will be set backwards (or if the HTTPS
>> servers are giving slightly early time). The adjtime() [1] call
>> ensures that the time increases monotically by either temporarily
>> increasing the CPU frequency to move it faster or decreasing it to
>> move it slower and let the real time catch up (from what I
>> understand).


Well, adjtime() changes the system clock in a monotonic way, but one
does not need adjtime() to have the system clock move forward in
a monotonic way all by itself. That's a clock, after all :)

>> So if you this set up, you can do an initial jump to set a Tails'
>> user's clock if it's needed, and then they can restart and be sure
>> that everything started and is still running with a smooth,
>> monotonic clock.


I'm afraid I don't get what you are suggesting. Note that Tails does
not save the state of the software clock to the hardware clock.

>> And maybe in the future you will find it useful.


:)

Cheers,
--
intrigeri
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