Bill Unruh 75a7af9edc Fix handling of stratum zero. ...

Further to the discussion with John Hasler, here are new diffs which
handles the incoming stratum 0 claim of a remote server by redefining the
incoming stratum as one bigger than the Max if it is zero, as per the NTP
version 4 documentation.

If the incoming stratum is zero it sets it to NTP_MAX_STRATUM+1 . If our
current stratum is larger than the NTP_MAX_STRATUM, the outgoing stratum is
also set to zero as per the suggestions in the NTP docs.
Introduces the new NTP_INVALID_STRATUM of 0 for doing these tests or
setting the outgoing stratum.

It is unclear whether chrony wants to follow NTP in setting the outgoing
stratum to zero if it is unknown or invalid, rather than a number larger
than the max stratum. Setting it to zero seems silly, since zero is already
used to define the stratum of a hardware clock (GPS, atomic, etc). This
seems ripe for confusion. But the fact that the ntp docs state to do this,
and that ntp servers (eg ntp.ubc.ca) are already doing this (using 0 to
mean invalid) means that chrony has to handle it on the incoming packets
from the servers.

2007-06-26 23:46:33 +01:00

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