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.
Don't update the leap and stratum used in source selection if they
indicate an unsynchronized source.
Fixes: 2582be8754 ("sources: separate update of leap status")
It is not sufficient to check for disabled server sockets as they are
not open only after the special reference modes end (e.g. initstepslew).
Fixes: 004986310d ("ntp: skip loop test if no server socket is open")
In the NTS-NTP client instance, maintain a local copy of the NTP address
instead of using a pointer to the NCR's address, which may change at
unexpected times.
Also, change the NNC_CreateInstance() to accept only the NTP port to
make it clear the initial NTP address is the same as the NTS-KE address
and to make it consistent with NNC_ChangeAddress(), which accepts only
one address.
Remove stratum from the NTP sample and update it together with the leap
status. This enables a faster update when samples are dropped by the NTP
filters.
Don't accept NTPv4 packets which have a MAC longer than 24 octets to
strictly follow RFC 7822, which specifies the maximum length of a MAC
and the minimum length of the last extension field to avoid an ambiguity
in parsing of the packet.
This removes an ugly hack that was needed to accept packets that
contained one or more extension fields without a MAC, before RFC 7822
was written and NTP implementations started using truncated MACs.
The long MACs were used by chrony in versions 2.x when configured to
authenticate a server or peer with a key using a 256-bit or longer hash
(e.g. SHA256). For compatibility with chrony >= 4.0, these clients/peers
will need to have "version 3" added to the server/peer line in
chrony.conf.
The daemon transmit timestamps are precompensated for the time it takes
to generate a MAC using a symmetric key (as measured on chronyd start)
and also an average round-trip time of the Samba signing of MS-SNTP
responses. This improves accuracy of the transmit timestamp, but it
has some issues.
The correction has a random error which is changing over time due to
variable CPU frequency, system load, migration to a different machine,
etc. If the measured delay is too large, the correction may cause the
transmit timestamp to be later than the actual transmission. Also, the
delay is measured for a packet of a minimal length with no extension
fields, and there is no support for NTS.
Drop the precompensation in favor of the interleaved mode, which now
avoids the authentication delay even when no kernel/hardware timestamps
are available.
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.
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.
Refactor the client record and clientlog API to reuse more code between
different services and enumerate the services instead of hardcoding NTP
and cmdmon.
Refactor the code to allow the selection options of the current sources
to be modified when other sources are added and removed. Also, make the
authentication status of each source available to the code which makes
the modifications.
When replacing an NTP source, update the NTS address before the NTP
address to save cookies with the old NTP address instead of the newly
resolved address (which may immediately change to an address provided by
NTS-KE).
Remove leap status from the NTP sample and set it independently from
the sample accumulation in order to accept a leap second sooner when
samples are filtered.
Add an option to enable NTS for an NTP source. Check for NTS-specific
extension fields and pass the packets to the NTS-NTP code in order to
enable the NTS client and server.
This will allow a source to have its address changed due to NTS-KE
server negotiation, which allows the NTS-KE server to have a different
address than the NTP server.
Move most of the authentication-specific code to a new file and
introduce authenticator instances in order to support other
authentication mechanisms (e.g. NTS).
Rework the code to detect the authentication mode and count extension
fields in the first parsing of the packet and store this information in
the new packet info structure.
When sending a response in the server or passive mode, make sure the
response is not longer than the request to prevent amplification
attacks when resposes may contain extension fields (e.g. NTS).
Add a structure for length and other information about received and
transmitted NTP packets to minimize the number of parameters and avoid
repeated parsing of the packet.
Improve the client's test D to compare the stratum, reference ID,
reference timestamp, and root delay from the received packet with its
own reference data in order to prevent it from synchronizing to itself,
e.g. due to a misconfiguration.
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.
