ntpd never achieves synchronized, even with PPS source; ntpdig KOD
Robin H. Johnson
robbat2 at gentoo.org
Tue Dec 18 07:22:20 UTC 2018
TL;DR:
------
1. ntpdig localhost always gets KOD
2. ntpsec never gets syncronized state: ntpwait never gives success
3. local clock ends up drifting :-(
Background:
-----------
I previously had another GPS puck, without PPS, and used it with classic
ntpd; the puck eventually stopped working, and I replaced it with a
GPS+PPS u-blox puck via Mark Atwood's occasional sales.
Mark was trying to convince me to switchover to ntpsec as well, which I
didn't actually get to until recently.
However, in doing so, I found that ntpsec never gets to synchronized
state on my machine.
For the below demonstration, configuration is the stock 1.1.2:
default.conf: use-gpsd-shm, use-pool,
use-no-remote-configuration, use-minimal-logging
Fresh start to confirm state:
# ntpdig -s -S ca.pool.ntp.org
2018-12-17 22:44:35.987560 (+0700) +2.240546 +/- 0.019099
ca.pool.ntp.org 129.128.12.20 s2 no-leap
CLOCK: time stepped by 2.240546
# ntpdig -s -S ca.pool.ntp.org
2018-12-17 22:44:44.460024 (+0700) -0.000036 +/- 0.018989
ca.pool.ntp.org 129.128.12.20 s2 no-leap
CLOCK: time stepped by -0.000036
# /etc/init.d/ntp restart
ntp | * Starting ntp ...
ntp |2018-12-18T06:45:41 ntpd[11042]: INIT: ntpd ntpsec-1.1.2
2018-09-30T16:42:11Z: Starting
ntp |2018-12-18T06:45:41 ntpd[11042]: INIT: Command line:
/usr/sbin/ntpd -p /run/ntpd.pid -g -u ntp:ntp -x -c /etc/ntp.d/default.conf [ ok ]
# ntpq -p -n ; ntpdig -ddd localhost
remote refid st t when poll reach delay offset jitter
============================================================================================
+SHM(0) .GPS. 0 l 10 64 1 0.0000 -137.466 0.0000
*SHM(1) .PPS. 0 l 9 64 1 0.0000 -7.9009 0.0000
pool.ntp.org .POOL. 16 p - 256 0 0.0000 0.0000 0.0001
158.69.125.231 173.162.192.156 2 u - 64 1 60.8591 -11.9539 0.1667
+209.115.181.108 206.108.0.134 3 u - 64 1 13.8295 -6.0775 0.1698
144.217.240.204 213.251.128.249 2 u - 64 1 61.0646 -3.8776 0.1854
129.128.12.20 129.128.153.62 2 u - 64 1 23.4383 -5.5400 0.3409
ntpdig: querying ::1 (localhost)
ntpdig: Sent to ::1:
e3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 df c3 16 21 47 1e a0 00 ...........!G...
e4 00 00 e8 00 00 00 00 00 07 f2 0e 44 4f 57 4e ............DOWN
df c3 16 17 60 ca 48 4e df c3 16 21 47 1e a0 00 ....`.HN...!G...
df c3 16 21 47 22 21 8e df c3 16 21 47 29 f9 0c ...!G"!....!G)..
ntpdig: querying 127.0.0.1 (localhost)
ntpdig: Sent to 127.0.0.1:
e3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 df c3 16 21 47 1e a0 00 ...........!G...
e4 00 00 e8 00 00 00 00 00 07 f2 0e 44 4f 57 4e ............DOWN
df c3 16 17 60 ca 48 4e df c3 16 21 47 1e a0 00 ....`.HN...!G...
df c3 16 21 47 40 9a bc df c3 16 21 47 44 32 65 ...!G at .....!GD2e
ntpdig: localhost: Response dropped: stratum 0, probable KOD packet
ntpdig: localhost: Response dropped: stratum 0, probable KOD packet
ntpdig: no eligible servers
# ntpwait -v
Waiting for ntpd to synchronize... No!
ntpd did not synchronize.
(Even after hours)
Sometime later to be sure:
# ntpq -p -n
remote refid st t when poll reach delay offset jitter
============================================================================================
xSHM(0) .GPS. 0 l 19 64 377 0.0000 -134.030 3.0875
*SHM(1) .PPS. 0 l 18 64 377 0.0000 -0.5434 4.6119
pool.ntp.org .POOL. 16 p - 256 0 0.0000 0.0000 0.0001
-158.69.125.231 173.162.192.156 2 u - 64 377 60.9259 -3.8232 5.9141
-209.115.181.108 206.108.0.134 3 u 62 64 377 14.1186 0.8184 5.4720
+144.217.240.204 213.251.128.249 2 u 65 64 377 61.4708 2.9191 5.3575
-129.128.12.20 129.128.153.62 2 u 59 64 377 23.4129 1.3014 5.4741
+158.69.226.90 213.251.128.249 2 u 9 64 377 61.0565 -0.5469 2.7180
-149.56.111.74 138.39.23.13 2 u 10 64 377 60.7539 0.3827 2.4776
-208.81.1.244 200.98.196.212 2 u 8 64 377 46.2660 -5.8013 2.7630
-206.108.0.131 .PPS. 1 u 13 64 377 57.2570 1.4152 2.4424
tcpdump of ntpwait -n 2:
23:17:26.828337 IP6 (flowlabel 0x5322d, hlim 64, next-header UDP (17) payload length: 20) ::1.58431 > ::1.123: [bad udp cksum 0x0027 -> 0x4506!] NTPv2, length 12
Reserved, Leap indicator: clock unsynchronized (192), Stratum 2 (secondary reference), poll 0 (1s), precision 1
Root Delay: 0.000000, Root dispersion: 0.000000 [|ntp]
23:17:26.828453 IP6 (class 0xb8, flowlabel 0xe50b0, hlim 64, next-header UDP (17) payload length: 380) ::1.123 > ::1.58431: [bad udp cksum 0x018f -> 0x815e!] NTPv2, length 372
Reserved, Leap indicator: clock unsynchronized (192), Stratum 130 (reserved), poll 0 (1s), precision 1
Root Delay: 50200.000000, Root dispersion: 0.005493, Reference-ID: 118.101.114.115
Reference Timestamp: 1768910397.134497907 (2092/02/26 10:28:13)
Originator Timestamp: 1679847028.439260803 (2089/05/01 15:38:44)
Receive Timestamp: 758197809.180452358 (2060/02/16 08:58:25)
Transmit Timestamp: 808532013.188372445 (2061/09/20 23:41:49)
Originator - Receive Timestamp: -921649219.258808445
Originator - Transmit Timestamp: -871315015.250888358
tcpdump of ntpdig -6 ::1
23:17:56.980230 IP6 (flowlabel 0xccae7, hlim 64, next-header UDP (17) payload length: 56) ::1.49497 > ::1.123: [bad udp cksum 0x004b -> 0xe251!] NTPv4, length 48
Client, Leap indicator: clock unsynchronized (192), Stratum 0 (unspecified), poll 0 (1s), precision 0
Root Delay: 0.000000, Root dispersion: 0.000000, Reference-ID: (unspec)
Reference Timestamp: 0.000000000
Originator Timestamp: 0.000000000
Receive Timestamp: 0.000000000
Transmit Timestamp: 3754106276.980171203 (2018/12/17 23:17:56)
Originator - Receive Timestamp: 0.000000000
Originator - Transmit Timestamp: 3754106276.980171203 (2018/12/17 23:17:56)
23:17:56.980341 IP6 (class 0xb8, flowlabel 0x25c82, hlim 64, next-header UDP (17) payload length: 56) ::1.123 > ::1.49497: [bad udp cksum 0x004b -> 0x47a9!] NTPv4, length 48
Server, Leap indicator: clock unsynchronized (192), Stratum 0 (unspecified), poll 0 (1s), precision -23
Root Delay: 0.000000, Root dispersion: 0.033187, Reference-ID: (unspec)
Reference Timestamp: 3754106274.113098032 (2018/12/17 23:17:54)
Originator Timestamp: 3754106276.980171203 (2018/12/17 23:17:56)
Receive Timestamp: 3754106276.980230634 (2018/12/17 23:17:56)
Transmit Timestamp: 3754106276.980324170 (2018/12/17 23:17:56)
Originator - Receive Timestamp: +0.000059431
Originator - Transmit Timestamp: +0.000152966
--
Robin Hugh Johnson
Gentoo Linux: Dev, Infra Lead, Foundation Treasurer
E-Mail : robbat2 at gentoo.org
GnuPG FP : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85
GnuPG FP : 7D0B3CEB E9B85B1F 825BCECF EE05E6F6 A48F6136
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