Pivoting

[Eric S. Raymond]

Hal Murray <hmurray at megapathdsl.net>:
> More pivoting....
> 
> pylib calls ntp.ntpc.lfptofloat() in several places
> 
> ntpc_lfptofloat() calls lfp_stamp_to_tspec()
> That's an inline which calls ntpcal_ntp_to_time()
> 
> ntpcal_ntp_to_time takes an optional second argument, the pivot time.
> If it's NULL, it uses "now".

That is correct.  It is a known bug in the Python tools (I think we
inherited this from the C versions) that they can easily fail when
querying a server based in a different era if the local clock has not
yet been synced properly.  Thanks for reminding me of this; I will add
bug warnings to the ntpq and ntpmon manual pages.

> The code in step_systime() is really really ugly.  (to my eye)

Not just to yours...

> It starts by computing the pivot.  It gets the build time as a broken down 
> struct, subtracts 10 years, converts back to a time_t.  All that can be 
> precomputed.
> 
> It converts the step to a l_fp, gets the system time as a tspec, converts 
> that to l_fp, adds them together, then converts back to a tspec.  That 
> convert back uses the pivot.
> 
> Now that we have a nice simple EPOCH, I hope somebody cleans that up.

This is a major work item, but it's not an urgent one - we have 14 years
to get a fix working and deployed.  Discussion of pivoting vs. sanity
checking is still heavy; I want to see us arrive at some sort of
mutually checking consnsus before we cut code.

> Does the 10 year step back make any sense?

Not to me.  I've added it to the list of work items as a mystery to be
plumbed.
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