Re: [chrony-dev] chrony report of IP for PPS

[worley@xxxxxxxxxxxx (Dale R. Worley)]

Bill Unruh <unruh@xxxxxxxxxxxxxx> writes:
> I just noticed that chronyc reports an ID of 80.80.83.45 for PPS0 
> That is actually a valid IP address for some network in Barcelona Spain.(It is
> also the ascii for PPS0) It makes me uncomfortable using a valid IP for the
> report, when for other servers it uses the actual valid IP.

I think this is a pattern that was inherited from ntpd.  The ntpd status
reports show a "ref id" for non-server sources that is always a 4
character string, and I suspect that that is an interpretation of a
4-byte magic value of a field in the protocol which usually carries an
IP address.  So it might be hard to change this hack without
restructuring some part of the NTP protocol.

Ah, it's laid out in RFC 5905 section 7.3:

   Reference ID (refid): 32-bit code identifying the particular server
   or reference clock.  The interpretation depends on the value in the
   stratum field.  For packet stratum 0 (unspecified or invalid), this
   is a four-character ASCII [RFC1345] string, called the "kiss code",
   used for debugging and monitoring purposes.  For stratum 1 (reference
   clock), this is a four-octet, left-justified, zero-padded ASCII
   string assigned to the reference clock.  The authoritative list of
   Reference Identifiers is maintained by IANA; however, any string
   beginning with the ASCII character "X" is reserved for unregistered
   experimentation and development.  The identifiers in Figure 12 have
   been used as ASCII identifiers:

     +------+----------------------------------------------------------+
     | ID   | Clock Source                                             |
     +------+----------------------------------------------------------+
     | GOES | Geosynchronous Orbit Environment Satellite               |
     | GPS  | Global Position System                                   |
     | GAL  | Galileo Positioning System                               |
     | PPS  | Generic pulse-per-second                                 |
     | IRIG | Inter-Range Instrumentation Group                        |
     | WWVB | LF Radio WWVB Ft. Collins, CO 60 kHz                     |
     | DCF  | LF Radio DCF77 Mainflingen, DE 77.5 kHz                  |
     | HBG  | LF Radio HBG Prangins, HB 75 kHz                         |
     | MSF  | LF Radio MSF Anthorn, UK 60 kHz                          |
     | JJY  | LF Radio JJY Fukushima, JP 40 kHz, Saga, JP 60 kHz       |
     | LORC | MF Radio LORAN C station, 100 kHz                        |
     | TDF  | MF Radio Allouis, FR 162 kHz                             |
     | CHU  | HF Radio CHU Ottawa, Ontario                             |
     | WWV  | HF Radio WWV Ft. Collins, CO                             |
     | WWVH | HF Radio WWVH Kauai, HI                                  |
     | NIST | NIST telephone modem                                     |
     | ACTS | NIST telephone modem                                     |
     | USNO | USNO telephone modem                                     |
     | PTB  | European telephone modem                                 |
     +------+----------------------------------------------------------+

See also http://www.iana.org/assignments/ntp-parameters/ntp-parameters.xhtml#ntp-parameters-1

                     Figure 12: Reference Identifiers

   Above stratum 1 (secondary servers and clients): this is the
   reference identifier of the server and can be used to detect timing
   loops.  If using the IPv4 address family, the identifier is the four-
   octet IPv4 address.  If using the IPv6 address family, it is the
   first four octets of the MD5 hash of the IPv6 address.  Note that,
   when using the IPv6 address family on an NTPv4 server with a NTPv3
   client, the Reference Identifier field appears to be a random value
   and a timing loop might not be detected.

Whether the refid is an address or a special code is determined by the
stratum number.

Dale

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