Programming pins for external PHC timestamping was added in Linux 3.15,
but the PHC subsystem is older than that. Compile the programming code
only when the ioctl is defined.
On some systems, passing NULL as the first argument to adjtime, will
result in returning the amount of adjustment outstanding from a previous
call to adjtime().
On macOS this is not allowed and the adjtime call will fault. We can
simulate the behaviour of the other systems by cancelling the current
adjustment then restarting the adjustment using the outstanding time
that was returned. On macOS 10.13 and later, the netbsd driver is now
used and must use these semantics when making/measuring corrections.
The sources and sourcestats commands accept -v as an option, but the
glibc implementation of getopt() reorders the arguments and parses the
option as a command-line option of chronyc.
Add '+' to the getopt string to disable this feature. Other getopt()
implementations should consider it a new command-line option, which will
be handled as an error if present.
This allows transmissions in symmetric mode to be scheduled
independently from client transmissions. This reduces maximum delay
in scheduling when chronyd is configured with a larger number of
servers.
Fix a sign error in conversion of HW time to local time, which caused
the jitter to be amplified instead of reduced. NTP with HW timestamping
should now be more stable and able to ignore occasionally delayed
readings of PHC.
In basic client mode, set the origin and receive timestamp to zero.
This reduces the amount of information useful for fingerprinting and
improves privacy as the origin timestamp allows a passive observer to
track individual NTP clients as they move across networks. (With chrony
clients that assumes the timestamp wasn't reset by the chronyc offline
and online commands.)
This follows recommendations from the current version of IETF draft on
NTP data minimization [1].
The timestamp could be theoretically useful for enhanced rate limiting
which can limit individual clients behind NAT and better deal with DoS
attacks, but no server implementation is known to do that.
[1] https://tools.ietf.org/html/draft-ietf-ntp-data-minimization-01
When no default route is configured, check each source if it has a
route. If the system has multiple network interfaces, this prevents
setting local NTP servers to offline when they can still be reached over
one of the interfaces.
In interleaved client mode, when so many consecutive requests were lost
that the first valid (interleaved) response would be dropped for being
too old, switch to basic mode so the response can be accepted if it
doesn't fail in the other tests.
This reworks commit 16afa8eb50.
In symmetric mode, don't send a packet in interleaved mode unless it is
the first response to the last valid request received from the peer and
there was just one response to the previous valid request. This prevents
the peer from matching the transmit timestamp with an older response if
it can't detect missed responses.
In interleaved symmetric mode, check if the remote TX timestamp is
before RX timestamp. Only the first response from the peer after
receiving a request should pass this test. Check also the interval
between last two remote transmit timestamps when we know the remote poll
can't be constrained by minpoll. Use the minimum of previous remote and
local poll as a lower bound of the actual interval between peer's
transmissions.
If synchronised to a stratum 15 source, return stratum of 16 instead of
0 in the tracking report. It will not match the value in server mode
packets, but it should be less confusing.
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.
If no CFLAGS are specified, check if common security hardening options
are supported and add them to the CFLAGS/LDFLAGS. These are typically
enabled in downstream packages, but users compiling chrony from sources
with default CFLAGS should get hardened binaries too.
macOS 10.13 will implement the ntp_adjtime() system call, allowing
better control over the system clock than is possible with the existing
adjtime() system call. chronyd will support both the older and newer
calls, enabling binary code to run without recompilation on macOS 10.9
through macOS 10.13.
Early releases of macOS 10.13 have a very buggy adjtime() call. The
macOS driver tests adjtime() to see if the bug has been fixed. If the
bug persists then the timex driver is invoked otherwise the netbsd
driver.
If the -Q option is specified, disable by default pidfile, ntpport,
cmdport, Unix domain command socket, and clock control, in order to
allow starting chronyd without root privileges and/or when another
chronyd instance is already running.
The tai field in struct timex is a Linux-specific feature. It's possible
to read the current offset with ntp_gettime() (or ntp_gettimex() on
Linux), but apparently not all libc implementations support it.
Rework the code to save and adjust the last value instead of reading
the current value from the kernel.
