Re: [gpsd-dev] New 0.5 draft of the SemPiTernal HOWTO

[Gary E. Miller]

Yo Frank!

On Thu, 5 May 2016 16:48:26 -0400
Frank Nicholas <address@hidden> wrote:

> > communicates with ntpd via SHM.  It's not clear why refclock 20
> > should survive thaat transition when gpsd is already better at
> > adapting to weird sentence inventories than it is.  
> 
> How portable is “SHM”?

Mostly portable, it is SYSV-r4, and POSIX-2001.  

Windows is different, but simple shims are possible.

Some people deprecate shmctl() and recommend the newer shm_open().

shm_open() is also POSIX-2001 and has UNIX everything is a file semantics.

> Is it covered everywhere NTPSec wants to go?

Windows....

> Is GPSd portable to everywhere NTPSec wants to go? (I’m asking, not
> arguing - I don’t know the answers).

Windows...

Rather than bump up to shm_open(), I'd like to add sockets.  Chronyd
uses sockets as an optional alternative to SHM.  This is more flexible,
more secure, and allows the consumer to wait for data instead of
polling.  Any process that can write to SHM can smash the clock.  It
does make things like ntpshmmon impossible.

Interesting to think about, but nothing actionable for short term.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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