[gpsd-users] How to get shared memory access from gpsd to ntpd to work?

[Etaoin Shrdlu]

Hi all, 

I've been battling for some time with getting ntpd to set the date/time
from gpsd's shared memory locations. My GPS device is on the network
and sends GPS messages every minute over UDP. This is picked up by gpsd
and it appears I get a good fix with all the required data. It also
looks as if the shared memory locations are being set up correctly. But
whatever I do, ntpd time source "reach" stubbornly remains at zero,
even when running ntpd as root. I would be most grateful if someone
could cast their eyes on the configurations and log output below, and
let me know if you can see were it's going wrong! 


# syslog gpsd startup: 

Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: launching (Version 3.11)
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: listening on port gpsd
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: NTPD shmat(0,0,0) succeeded, 
segment 0
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: NTPD shmat(32769,0,0) succeeded, 
segment 1
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: NTPD shmat(65538,0,0) succeeded, 
segment 2
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: NTPD shmat(98307,0,0) succeeded, 
segment 3
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: successfully connected to the 
DBUS system bus
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: shmat() succeeded, segment 131076
Aug  6 19:28:16 computer gpsd[374]: gpsd:PROG: shared-segment creation 
succeeded,
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: stashing device 
udp://192.168.13.100:10110 at slot 0
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: opening UDP feed at 
192.168.13.100, port 10110.
Aug  6 19:28:16 computer gpsd[374]: gpsd:ERROR: UDP device open error can't 
connect to host/port pair.
Aug  6 19:28:16 computer gpsd[374]: gpsd:ERROR: initial GPS device 
udp://192.168.13.100:10110 open failed
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: running with effective group ID 
20
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: running with effective user ID 
110
Aug  6 19:28:16 computer gpsd[374]: gpsd:INFO: startup at 
2017-08-06T19:28:16.000Z (1502047696)

# syslog ntpd startup:

Aug  6 19:28:24 computer ntpd[609]: ntpd address@hidden Mon Jul 25 22:35:28 UTC 
2016 (1)
Aug  6 19:28:24 computer ntp[582]: Starting NTP server: ntpd.
Aug  6 19:28:24 computer ntpd[652]: proto: precision = 0.781 usec
Aug  6 19:28:24 computer ntpd[652]: Listen and drop on 0 v4wildcard 0.0.0.0 UDP 
123
Aug  6 19:28:24 computer systemd[1]: Started LSB: Start NTP daemon.
Aug  6 19:28:25 computer ntpd[652]: Listen and drop on 1 v6wildcard :: UDP 123
Aug  6 19:28:25 computer ntpd[652]: Listen normally on 2 lo 127.0.0.1 UDP 123
Aug  6 19:28:25 computer ntpd[652]: Listen normally on 3 eth0 192.168.13.100 
UDP 123
Aug  6 19:28:25 computer ntpd[652]: Listen normally on 4 lo ::1 UDP 123
Aug  6 19:28:25 computer ntpd[652]: Listen normally on 5 eth0 
fe80::6a89:f1d3:7ec0:510 UDP 123
Aug  6 19:28:25 computer ntpd[652]: peers refreshed
Aug  6 19:28:25 computer ntpd[652]: Listening on routing socket on fd #22 for 
interface updates

# syslog gpsd sample: 

Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPGGA,185748.0,1234.567890,N,00012.345678,E,1,10,0.9,13.6,M,47.0,M,,*6B
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: GPGGA sentence timestamped 
185748.00.
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: GPGGA starts a reporting cycle.
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPRMC,185748.0,A,1234.567890,N,00012.345678,E,0.0,,060817,0.0,E,A*2B
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: GPRMC sentence timestamped 
185748.00.
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: GPRMC ends a reporting cycle.
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPVTG,,T,0.0,M,0.0,N,0.0,K,A*0D
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPGSA,A,2,01,03,06,09,11,17,19,22,23,31,,,1.2,0.9,0.8*31
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: GPGSA sets mode 2
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPGSV,4,1,13,01,31,136,41,03,67,068,35,06,32,303,31,09,34,202,41*78
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: Partial satellite data (1 of 4).
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPGSV,4,2,13,11,09,153,39,17,40,243,40,19,42,272,30,22,42,082,40*78
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: Partial satellite data (2 of 4).
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: 
$GPGSV,4,3,13,23,61,174,46,31,19,047,36,12,04,329,,14,00,039,*76
Aug  6 19:56:42 computer gpsd[374]: gpsd:PROG: Partial satellite data (3 of 4).
Aug  6 19:56:42 computer gpsd[374]: gpsd:IO: <= GPS: $GPGSV,4,4,13,25,01,001,*4C


# /etc/default/gpsd

START_DAEMON="true"
USBAUTO="false"
DEVICES="udp://192.168.13.100:10110"
GPSD_OPTIONS="-n -D5"


# ntpd.conf: 

GPS Serial data reference (NTP0)
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 0.0 refid GPS

GPS PPS reference (NTP1)
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid PPS


# ntpq -p                                                                       
                                                                  Sun Aug  6 
19:48:25 2017

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 SHM(0)          .GPS.            0 l    -   16    0    0.000    0.000   0.000
 SHM(1)          .PPS.            0 l    -   16    0    0.000    0.000   0.000


# cat /proc/sysvipc/shm                                                         
                                                                  Sun Aug  6 
19:30:45 2017

       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  
cgid      atime      dtime      ctime        rss       swap
1314148400          0   600         80   374   652      2     0     0     0     
0 1502047705          0 1502047696       4096          0
1314148401      32769   600         80   374   652      2     0     0     0     
0 1502047705          0 1502047696       4096          0
1314148402      65538   666         80   374   374      1     0     0     0     
0 1502047696          0 1502047696          0          0
1314148403      98307   666         80   374   374      1     0     0     0     
0 1502047696          0 1502047696          0          0
1196446532     131076   666      31616   374   374      1     0     0     0     
0 1502047696          0 1502047696          0          0


# gpsmon:

tcp://localhost:2947          JSON slave driver>
(83) 
{"class":"VERSION","release":"3.11","rev":"3.11-3","proto_major":3,"proto_minor":9}
(125) 
{"class":"DEVICES","devices":[{"class":"DEVICE","path":"udp://192.168.13.100:10110","activated":"2017-08-06T19:31:50.526Z"}]}
(122) 
{"class":"WATCH","enable":true,"json":false,"nmea":false,"raw":2,"scaled":false,"timing":false,"split24":false,"pps":true}

tcp://localhost:2947          NMEA0183>
┌──────────────────────────────────────────────────────────────────────────────┐
│Time: 2017-08-06T18:33:45.000Z Lat:  12 34' 56.789" N Lon:   0 12' 34.567" E  │
└───────────────────────────────── Cooked TPV ─────────────────────────────────┘
┌──────────────────────────────────────────────────────────────────────────────┐
│ GPGGA GPRMC GPVTG GPGSA GPGSV                                                │
└───────────────────────────────── Sentences ──────────────────────────────────┘
┌──────────────────┐┌────────────────────────────┐┌────────────────────────────┐
│Ch PRN  Az El S/N ││Time:      183345.0         ││Time:      183345.0         │
│ 0   1 130 42  35 ││Latitude:   1234.567890 N   ││Latitude:  1234.567890      │
│ 1   3  52 78  40 ││Longitude:  00012.34567 E   ││Longitude: 00012.34567      │
│ 2   9 201 22  40 ││Speed:     0.0              ││Altitude:  109.4            │
│ 3  11 151 20  45 ││Course:                     ││Quality:   1   Sats: 10     │
│ 4  17 257 46  25 ││Status:    A       FAA: A   ││HDOP:      0.9              │
│ 5  19 288 41  34 ││MagVar:    0.0  E           ││Geoid:     47.0             │
│ 6  22  77 52  39 │└─────────── RMC ────────────┘└─────────── GGA ────────────┘
│ 7  23 180 50  38 │┌────────────────────────────┐┌────────────────────────────┐
│ 8  31  59 19  26 ││Mode: A2 Sats:              ││UTC:           RMS:         │
│ 9 120   0  0  35 ││DOP: H=0.9   V=0.8   P=1.2  ││MAJ:           MIN:         │
│10  12 338  5   0 ││TOFF:  3535.132782450       ││ORI:           LAT:         │
│11  14  39  9   0 ││PPS:                        ││LON:           ALT:         │
└────── GSV ───────┘└──────── GSA + PPS ─────────┘└─────────── GST ────────────┘
(83) 
{"class":"VERSION","release":"3.11","rev":"3.11-3","proto_major":3,"proto_minor":9}
(125) 
{"class":"DEVICES","devices":[{"class":"DEVICE","path":"udp://192.168.13.100:10110","activated":"2017-08-06T19:31:50.526Z"}]}
(122) 
{"class":"WATCH","enable":true,"json":false,"nmea":false,"raw":2,"scaled":false,"timing":false,"split24":false,"pps":true}
(73) $GPGGA,183345.0,1234.567890,N,00012.345678,E,1,10,0.9,9.4,M,47.0,M,,*5D
(71) $GPRMC,183345.0,A,1234.334342,N,00012.345678,E,0.0,,060817,0.0,E,A*24
(34) $GPVTG,,T,0.0,M,0.0,N,0.0,K,A*0D
(59) $GPGSA,A,2,01,03,06,09,11,17,19,22,23,31,,,1.2,0.9,0.8*31
(70) $GPGSV,3,1,12,01,42,130,35,03,78,052,40,09,22,201,40,11,20,151,45*7C
(70) $GPGSV,3,2,12,17,46,257,25,19,41,288,34,22,52,077,39,23,50,180,38*7B
(61) $GPGSV,3,3,12,31,19,059,26,33,,,35,12,05,338,,14,09,039,*46