Allow NTP messages to be exchanged as a payload of PTP messages to
enable full hardware timestamping on NICs that can timestamp PTP packets
only. Implemented is the protocol described in this draft (version 00):
https://datatracker.ietf.org/doc/draft-mlichvar-ntp-over-ptp/
This is an experimental feature. It can be changed or removed in future.
The used PTP domain is 123 and the NTP TLV type is 0x2023 from the "do
not propagate" experimental range.
The ptpport directive enables NTP-over-PTP as a server and as a client
for all sources that have the port option set to the PTP port. The port
should be the PTP event port (319) to trigger timestamping in the
hardware.
The implementation is contained to ntp_io. It is transparent to
ntp_core.
The files are read after dropping root privileges. They need to be
readable by the chrony user. The error message "Could not set
credentials : Error while reading file." does not make this requirement
very obvious.
The NTS RFC requires the recipient of the Server Negotiation NTS-KE
record to handle the name as a fully qualified domain name. Add a
trailing dot if not present to force the name to be resolved as one.
When reading a *.sources file require that each line is termined by the
newline character to avoid processing an unfinished line, e.g. due to an
unexpected call of the reload command when the file is being written in
place.
When separate client and server instances of chronyd are running on one
computer (e.g. for security or performance reasons) and are synchronized
to each other, the server instance provides a reference ID based on the
local address used for synchronization of its NTP clock, which breaks
detection of synchronization loops for its own clients.
Add a "copy" option to specify that the server and client are closely
related, no loop can form between them, and the client should assume the
reference ID and stratum of the server to fix detection of loops between
the server and clients of the client.
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.
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 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.
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.
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.
