[ntp:questions] ntpd 4.2.0a (+debian patches) polls 1 packet/second with some servers

Anthony DeRobertis netnews at derobert.net
Sat Dec 24 04:09:10 UTC 2005


It appears that the ntpd in Debian Sarge sometimes decides to poll once
per second, despite having standard a minpoll set. I have reported this
bug to Debian, see [1] for the bug report.

It appears this is happening when the server sends an invalid response
containing a poll interval of 0. I'm bringing it up here because (a) I
know this is where the ntp experts hang out; (b) I'd like to know if this
is a Debian-specific problem or not.

Frame 2 (90 bytes on wire, 90 bytes captured)
Ethernet II, Src: 00:90:7f:04:cb:83, Dst: 00:30:48:76:86:da
Internet Protocol, Src Addr: 69.17.7.16 (69.17.7.16), Dst Addr: 172.16.1.31 (172.16.1.31)
User Datagram Protocol, Src Port: ntp (123), Dst Port: ntp (123)
Network Time Protocol
    Flags: 0x24
        00.. .... = Leap Indicator: no warning (0)
        ..10 0... = Version number: NTP Version 4 (4)
        .... .100 = Mode: server (4)
    Peer Clock Stratum: secondary reference (2)
    Peer Polling Interval: invalid (0)
    Peer Clock Precision: 0.015625 sec
    Root Delay:    0.0403 sec
    Clock Dispersion:    0.0141 sec
    Reference Clock ID: 192.5.41.40
    Reference Clock Update Time: Dec 19, 2005 17:50:44.7940 UTC
    Originate Time Stamp: Dec 19, 2005 17:51:13.7451 UTC
    Receive Time Stamp: Dec 19, 2005 17:51:13.7645 UTC
    Transmit Time Stamp: Dec 19, 2005 17:51:13.7645 UTC

0000  00 30 48 76 86 da 00 90 7f 04 cb 83 08 00 45 00   .0Hv..........E.
0010  00 4c 00 00 00 00 75 11 4c 51 45 11 07 10 ac 10   .L....u.LQE.....
0020  01 1f 00 7b 00 7b 00 38 ef 63 24 02 00 fa 00 00   ...{.{.8.c$.....
0030  0a 52 00 00 03 9b c0 05 29 28 c7 51 71 74 cb 44   .R......)(.Qqt.D
0040  e8 00 c7 51 71 91 be bf fc da c7 51 71 91 c3 b4   ...Qq......Qq...
0050  a0 00 c7 51 71 91 c3 b6 80 00                     ...Qq.....


I'm not sure if 69.17.7.16 is still serving NTP with this broken server
(it was in pool.ntp.org, quite possible it was DoS'd off the face of the
earth)


[1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=344289




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