For sources specified by an IP address, keep the original address as the
source's name and pass it to the NCR instance. Allow the sources to go
through the replacement process if their address has changed.
This will be useful with NTS-KE negotiation.
The IP-based source names are now provided via cmdmon. This means
chronyc -n and -N can show two different addresses for a source.
This commit updates the FAQ with a new entry.
chronyd's Linux RTC driver (rtc_linux.c) requires the following ioctl
requests to be functional:
RTC_UIE_ON
RTC_UIE_OFF
However, a Linux system's RTC driver does not necessarily implement them,
as noted in these previous commits:
d66b2f2b24
rtc: handle RTCs that don't support interrupts
Tue Dec 10 17:45:28 2019 +0100
bff3f51d13
rtc: extend check for RTCs that don't support interrupts
Thu Dec 12 12:50:19 2019 +0100
Fortunately, the Linux kernel can be built with software emulation of
these hardware requests, by enabling the following config variable:
CONFIG_RTC_INTF_DEV_UIE_EMUL
Provides an emulation for RTC_UIE if the underlying rtc chip
driver does not expose RTC_UIE ioctls. Those requests generate
once-per-second update interrupts, used for synchronization.
The emulation code will read the time from the hardware
clock several times per second, please enable this option
only if you know that you really need it.
This commit records these facts for the benefit of the user.
GNU readline switched to GPLv3+ in version 6.0, which is incompatible
with the chrony's GPLv2 license.
Drop support for the readline library. Only editline is supported now.
The -U option can be used to start chronyd under a non-root user if it
is provided with all capabilities and access to files, directories, and
devices, needed to operate correctly in the specified configuration. It
is not recommended in cases where the configuration is unknown.
Make the precision of the system clock configurable. This can be useful
on servers using hardware timestamping to reduce the amount of noise
added to the NTP timestamps and improve stability of NTP measurements.
The directive sets the DSCP value in transmitted NTP packets, which can
be useful in local networks where switches/routers are configured to
prioritise packets with specific DSCP values.
If the daemon transmit timestamp is saved for processing of a future
response or responding in the interleaved mode, get a more accurate
timestamp right before calling NIO_SendPacket(). Avoid unnecessary
reading of the clock for the transmit timestamp in the packet (i.e.
in interleaved modes and client basic mode).
This should improve accuracy and stability when authentication is
enabled in the client and symmetric basic modes and also interleaved
modes if kernel/hardware timestamps are not available.
Add binddevice, bindacqdevice, and bindcmddevice directive to specify
the interface for binding the NTP server, NTP client, and command socket
respectively.
Instead of making the initial burst only once and immediately after
chronyd start (even when iburst is specified together with the offline
option), trigger the burst whenever the connectivity changes from
offline to online.
Add -p option to chronyd to print lines from the configuration as they
are parsed and exit. It can be used to verify the syntax and get the
whole configuration when it is split into multiple files.
Instead of sharing the NTP rate limiting with NTS-KE, specify a new
service for NTS-KE and use it in the NTS-KE server.
Add ntsratelimit directive for configuration.
Add a new field to the CLIENT_ACCESSES_BY_INDEX request to specify the
minimum number of NTP or cmdmon packets for a client to be reported.
Add -p option to the chronyc clients command to specify the threshold
(by default 0). This option can be used to minimize the number of cmdmon
requests when interested only in clients sending a large number
of requests.
Add a flag to the CLIENT_ACCESSES_BY_INDEX request to reset the
NTP/cmdmon hits/dropped counters after reporting the current values.
Add -r option to the chronyc clients command to perform the reset. This
should make it easier to find clients that send large number of requests
over short periods of time.
Add a confdirs directive to include *.conf files from multiple
directories. If a file with the same name exists in multiple
directories, only the first one in the order of the specified
directories will be included.
When authentication is enabled for an NTP source, unauthenticated NTP
sources need to be disabled or limited in selection. That might be
difficult to do when the configuration comes from different sources
(e.g. networking scripts adding servers from DHCP).
Define four modes for the source selection to consider authentication:
require, prefer, mix, ignore. In different modes different selection
options (require, trust, noselect) are added to authenticated and
unauthenticated sources.
The mode can be selected by the authselectmode directive. The mix mode
is the default. The ignore mode enables the old behavior, where all
sources are used exactly as specified in the configuration.
The reset command drops all measurements and switches the reference to
the unsynchronised state. This command can help chronyd with recovery
when the measurements are known to be no longer valid or accurate, e.g.
due to moving the computer to a different network, or resuming the
computer from a low-power state (which resets the system clock).
Add -a option to the sources and sourcestats commands to print all
sources, including those that don't have a resolved address yet. By
default, only sources that have a real address are printed for
compatibility. Remove the "210 Number of sources" messages to avoid
confusion. Also, modify the ntpdata command to always print only sources
with a resolved address.
When resolving of a pool name succeeds, don't remove the remaining
unresolved sources, i.e. try to get all maxsources (default 4) sources,
even if it takes multiple DNS requests.
Add a new command to print the original name of a source specified by
address. This could be useful in scripts to avoid having to run the
sources command with and without -N.
Add -N option to chronyc to print the original names by which the
sources were specified instead of using reverse DNS lookup. The option
works in the sources, sourcestats and tracking commands.
Modify the request for adding a source to provide the name of the source
instead of its address (resolved in chronyc) in order to enable chronyd
to replace the source, support an "add pool" command, and enable an NTS
client to verify the server's certificate.
The name resolving does not block the response. Success is indicated
even if the name cannot be resolved, or a source with the same address
is already present.
To prevent unresolvable names from getting to chronyd, chronyc does not
send the request if it could not resolve the name itself (assuming they
are both running on the same host using the same resolver).
Allow a cipher (AES128 or AES256) to be specified as the type of a key
in the key file to authenticate NTP packets with a CMAC instead of the
NTPv4 (RFC 5905) MAC using a hash function. This follows RFC 8573.
An analysis by Tim Ruffing [1] shows that a length extension attack
adding valid extension fields to NTPv4 packets is possible with some
specific key lengths and hash functions using little-endian length like
MD5 and RIPEMD160.
chronyd currently doesn't process or generate any extension fields, but
it could be a problem in future when a non-authentication extension
field is supported.
Drop support for all RIPEMD functions as they don't seem to be secure in
the context of the NTPv4 MAC. MD5 is kept only for compatibility.
[1] https://mailarchive.ietf.org/arch/msg/ntp/gvibuB6bTbDRBumfHNdJ84Kq4kA
Setting maxsamples to 1 or 2 prevented the source from being selected as
the regression would always fail. Handle this as a special case with
disabled frequency tracking in order to enable a fast reference update
with the -q/-Q option.
Real-time scheduling and memory locking is available on posix compliant
OSs. This patch centralizes this functionality and brings support to
FreeBSD, NetBSD, and Solaris.
[ML: updated coding style]
Add an option to use the median filter to reduce noise in measurements
before they are accumulated to sourcestats, similarly to reference
clocks. The option specifies how many samples are reduced to a single
sample.
The filter is intended to be used with very short polling intervals in
local networks where it is acceptable to generate a lot of NTP traffic.
Instead of counting missing responses, switch to the offline state
immediately when sendmsg() fails.
This makes the option usable with servers and networks that may drop
packets, and the effect will be consistent with the onoffline command.
The onoffline command tells chronyd to switch all sources to the online
or offline status according to the current network configuration. A
source is considered online if it is possible to send requests to it,
i.e. a route to the network is present.
When the burst option is specified in the server/pool directive and the
current poll is longer than the minimum poll, initiate on each poll a
burst with 1 good sample and 2 or 4 total samples according to the
difference between the current and minimum poll.
This option is for indicating to chronyd that the reference clock is
kept in TAI and that chrony should attempt to convert from TAI to UTC by
using the timezone configured by the "leapsectz" directive.
Similarly to the maxdelaydevratio test, include in the maximum delay
dispersion which accumulated in the interval since the last sample.
Also, enable the test for symmetric associations.
If no rxfilter is specified in the hwtimestamp directive and the NIC
doesn't support the all or ntp filter, enable TX-only HW timestamping
with the none filter.
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.
Use the timezone specified by the leapsectz directive to get the
current TAI-UTC offset and set the offset of the system clock in order
to provide correct TAI time to applications using ntp_adjtime(),
ntp_gettime(), or clock_gettime(CLOCK_TAI).
Add a new clock driver that doesn't actually try to adjust the clock.
It allows chronyd to run without the capability to adjust/set the system
clock, e.g. in some containers. It can be enabled by the -x option.
Always write the measurement history on exit when the dump directory is
specified and silently ignore the dumponexit directive. There doesn't
seem to be a good use case for dumpdir and -r without dumponexit as the
history would be invalidated by adjustments of the clock that happened
between the dump command and chronyd exit.
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.
Change the default NTP rate limiting leak to 2 (25%). Change the default
command rate limiting interval to -4 (16 packets per second) and burst
to 8, so the interval is the only difference between NTP and command
rate limiting defaults.
This reverts commit 50022e9286.
Testing showed that ntpd as an NTP client performs poorly when it's
getting only 25% of responses. At least for now, disable rate limiting
by default again.
Change the default interval of both NTP and command rate limiting to -10
(1024 packets per second) and the burst to 16. The default NTP leak is 2
(rate limiting is enabled by default) and the default command leak is 0
(rate limiting is disabled by default).
