Yo Hal! On Sun, 23 Apr 2017 03:20:48 -0700 Hal Murray <[email protected]> wrote:
> [email protected] said: > > I'd have ntpd reject any time prior to EPOCH. > > How do you decide whether to reject it or pivot it into the future? If you know unambiguously the time is past then you can reject. Otherwise pivot. > >> Allow the user to specify the pivot time and/or life time, either > >> at build time or at run time or both. > > EPOCH is used for NMEA, so that is covered at build time. > > I could see adding an option to specify the EPOCH at run time too. > > My build time comment was mostly for life time. I was assuming that > EPOCH would be used for pivoting. Incomplete assumption, BUILD_EPOCH is also used to disambihuate century for 2 digit years in NMEA and some other drivers. As was __DATE__ previously. > I know about three pivots to consider. One is GPS 10 bits for weeks > with a 20 year step size. Another is 2 digit year numbers with a 100 > year step size. The third is 32 bits of seconds in NTP packets with > a 136 year step size. Are there any others I've overlooked? Some GPS use 13 bit weeks. For completeness, there is still the 2038 pivot for time32_t in use by some 32 bit OS. > If we want our software to last more than 20 years while talking to > crappy GPS receivers, we need a way to update the pivot date at run > time. (I'm using "last" to mean without rebuilding.) Fair enough. I keep suggesting being able to override BUILD_EPOCH in ntp.conf. hen leave the problem to others how to get that set right. > If we want our software to reject bogus time, we have to balance the > tradeoff between long life and good filtering. Run time parameters > will allow the user to choose. Choose to shoot himself in the foot too. But gotta take that risk. > I have a pre-software scope that's over 35 years old. Ditto here. Just one? > The combination of long life and crappy GPS seems obscure enough that > I'm willing to document it as a limitation. It's the kind of code > that Eric would love to rip out if he found it a year ago. Doc is a good start. > The documentation issue gets interesting. A feature isn't any good > if you can't figure out how to use it. I wonder if the web will > solve that problem. Will NTPsec still be online 20 years from now? > Will we maintain online versions of 20 year old releases? As I've previously said, I have friend running 20 year binaries of NTP classic. > Would anybody notice a warning message from a program that's been > running for 19 years? Prolly not... RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 [email protected] Tel:+1 541 382 8588 Veritas liberabit vos. -- Quid est veritas? "If you can’t measure it, you can’t improve it." - Lord Kelvin
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