Check how many responses were missing before accumulating a sample using
old timestamps to avoid correcting the clock with an offset extrapolated
over a long interval.
This should be eventually done in sourcestats for all sources.
With the new selection of timestamps in the interleaved mode it's no
longer necessary to reverse the poll tracking in order to reduce the
local and remote intervals of measurements that makes the peer with
higher stratum.
This reverts commit 4a24368763.
Use previous local TX and remote RX timestamps for the new sample in the
interleaved mode if it will make the local and remote intervals
significantly shorter in order to improve the accuracy of the measured
delay.
Unlike in the basic mode, the peer with a higher stratum needs to wait
for a response before sending the next request in order to minimize the
delay of the measurement and error in the measured delay.
Slightly increase the delay adjustment to make it work with older chrony
versions.
Update the remote poll and remote stratum even for unsychronised peers,
and handle stratum of 0 as 16, so the peers work with the opposite
differences between their strata and can adjust their polling intervals
in order to interleave the packets.
When the poll value in a client request is smaller than the server's NTP
rate limiting interval, set poll in the response to the rate limiting
interval to suggest the client to increase its polling interval.
This follows ntpd as a server. No current client implementation seems to
be increasing its interval by the poll, but it may change in the future.
It was never used for anything and messages in debug output already
include filenames, which can be easily grepped if there is a need
to see log messages only from a particular file.
While the measurements log can be useful for debugging problems in NTP
configuration (e.g. authentication failures with symmetric keys), it
seems most users are interested only in valid measurements (e.g. for
producing graphs) and don't expect/handle entries where some of the RFC
5905 tests 1-7 failed. Modify the measurements log option to log only
valid measurements, and for debugging purposes add a new rawmeasurements
option.
When the server's transmit timestamp was updated with a kernel/HW
timestamp, it didn't include the time smoothing offset. If the offset
was larger than one second, the update failed and clients using the
interleaved mode received less accurate timestamps. If the update
succeeded, the clients received timestamps that were not adjusted for
the time smoothing offset, which added an error of up to 0.5s/1s to
their measured offset/delay.
Fix the update to include the smoothing offset in the new timestamp.
Before sending an NTP packet, check whether the TX timestamp is not
equal to the RX timestamp. If it is, generate a new TX timestamp and try
again. This is extremely unlikely to happen in normal operation, but it
is needed for reliable detection of the interleaved mode.
Instead of a worst-case delay use a mean value and relate it to the
source's time. This makes it more stable in the interleaved and
symmetric modes, which should improve the weighting and asymmetry
correction. Modify the test A and B to work with a minimum estimated
delay (delay - dispersion).
If the MAC in NTPv4 requests would be truncated, use version 3 by
default to avoid the truncation. This is necessary for compatibility
with older chronyd servers, which do not respond to messages with
truncated MACs.
In order to allow deterministic parsing of NTPv4 extension fields, the
MAC must not be longer than 192 bits (RFC 7822). One way to get around
this limitation when using symmetric keys which produce longer MACs is
to truncate them to 192 bits (32-bit key ID and 160-bit hash).
Modify the code to accept NTPv4 packets with MACs truncated to 192
bits, but still allow long MACs in NTPv4 packets to not break
compatibility with older chrony clients.
In a burst of three requests (two presend + one normal) the server can
detect the client is using the interleaved mode and save the transmit
timestamp of the second response for the third response. This shortens
the interval in which the server has to keep the state.
Rework the code to make a real request for presend and process the
response, but don't accumulate the sample. This allows presend to work
in the interleaved client mode.
