Allow an IP family to be specified in the socket initialization in order
to globally disable the other family. This replaces the ntp_io and
cmdmon code handling the -4/-6 options and fixes a case where the NTP
client could still use a disabled family if the source was specified
with an IP address.
With asymmetric routing (e.g. with BGP) it may not be possible to
respond to a request using the same interface. In such case, setting the
interface index in IP*_PKTINFO* causes the packet to be silently dropped
by the kernel.
Until we can predict if sending with the specified interface will
succeed, or provide only a hint, don't set the interface and leave it
to the kernel to select an interface.
This reverts commit 5fc7674e36 ("ntp: set interface index in
IP*_PKTINFO when responding").
Reported-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
Don't require the caller to provide a SCK_Message (on stack). Modify the
SCK_ReceiveMessage*() functions to return a pointer to static buffers,
as the message buffer which SCK_Message points to already is.
On Linux, enable the SO_REUSEPORT option on sockets bound to a port in
order to support load balancing with multiple chronyd instances
(configured to not adjust the system clock).
The IP_FREEBIND option already allowed different instances to bind to
the same address and port, but only one was actually receiving packets.
As the instances don't share their state, sharing the NTP port doesn't
work well with the interleaved mode, symmetric mode, and rate limiting.
Sharing the NTS-KE port will not work until the server keys can be
derived from a shared key.
Don't call bind() if the specified local address of a socket has port 0
and the "any" address. It will be bound automatically on connect() or
sendmsg().
On start, check if the SOCK_CLOEXEC and SOCK_NONBLOCK flags are
supported in the socket() call and use them instead of fcntl() in order
to reduce the number of system calls required to send a client request.
All networking code in chronyd (NTP server/client, signd client, cmdmon
server) assumes sending a message will not block, but only the signd
client actually checks for a write event and only the NTP server
requests a non-blocking socket. The cmdmon server and NTP client
(if using one socket for all servers) might be blocked.
chronyc doesn't need a non-blocking socket, but it is not expected to
block as it sends only one message at a time.
Prefer dropped messages over blocking in all cases. Remove the
SCK_FLAG_NONBLOCK flag and make all sockets non-blocking.
Add a new file implementing support for opening sockets, sending and
receiving messages with control messages (e.g. addresses, timestamps),
and related operations, which should be simpler to use than the system
functions and allow their features to be reused between different parts
of the chrony code.
It is based on the ntp_io.c and ntp_io_linux.c files. It will be used by
the NTP client/server, cmdmon server, client, and others.
