[ntp:hackers] Privacy: refclock_nmea is now munging lat/long
Dave Hart
davehart at gmail.com
Mon May 18 11:35:46 UTC 2009
On Sat, Apr 25, 2009 at 11:45 PM, Dave Hart <davehart at gmail.com> wrote:
> Arguing for simply reverting the change, the operator can choose to
> use the $GPZDA NMEA sentence that lacks position information,
> providing privacy with no changes to the traditional
> ntpd+refclock_nmea code.
I attempted to use this approach but discovered my GPS 18x LVC doesn't
support $GPZDA. Disagreeing with the assertion that I should block
public ntpq queries entirely if I am seriously concerned about that
level of privacy, I added support in refclock_nmea as of 4.2.5p176 for
optionally removing the location fields from the saved timecode
visible via "ntpq -c clockvar" and recorded in clockstats. If you use
refclock_nmea and would prefer to keep your GPS antenna's precise
location private, use
fudge 127.127.20.__ flag4 1
Which results in:
C:\ntp>ntpq -c cv davehart.net
associd=0 status=00f0 , 15 events, clk_unspec,
device="NMEA GPS Clock",
timecode="$GPGGA,113411,____.____,N,_____.____,W,2,07,1.2,121.8,M,-18.0,M,,*__",
poll=14417, noreply=0, badformat=0, baddata=0, fudgetime1=-3.500,
stratum=0, refid=gPPS, flags=8
C:\ntp>
Cheers,
Dave Hart
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