Use UTI_GetRandomBytes() instead of random() to calculate the random
part of the timeout. This was the only remaining use of random() in the
code and the srandom() call can be removed.
In client packets set the leap, stratum, reference ID, reference time,
root delay and root dispersion to constant values to not reveal the
state of the synchronization. Use precision 32 to make the receive and
transmit timestamps completely random and not reveal the local time.
Use UTI_GetRandomBytes() instead of random() to generate random bits
below precision. Save the result in NTP_int64 in the network order and
allow precision in the full range from -32 to 32. With precision 32
the fuzzing now makes the timestamp completely random and can be used to
hide the time.
Add a function to fill a buffer with random bytes which uses a better
PRNG than random(). Use arc4random() if it's available on the system.
Fall back to reading from /dev/urandom, which should be available on
all currently supported systems.
After sending a client packet, schedule a timeout to close the socket
at the time when all server replies would fail the delay test, so the
socket is not open for longer than necessary (e.g. when the server is
unreachable). With the default maxdelay of 3 seconds the timeout is 7
seconds.
For testA in the client mode require also that the time the server
needed to process the client request is not longer than 4 seconds.
With maximum peer delay this limits the interval in which the client can
accept a server reply.
To avoid problems in the very unlikely case where a timeout is so long
and new IDs are allocated so frequently that they would have a chance
to overflow and catch up with it, make sure before returning new ID that
it's currently not in use.
Timeout ID of zero can be now safely used to indicate that the timer is
not running. Remove the extra timer_running variables that were
necessary to track that.
This is useful on computers that have an RTC, but there is no battery to
keep the time when they are turned off and start with the same time on
each boot.
Instead of calling the handler directly schedule a timeout with zero
delay for resolving to make the function behave similarly to the real
asynchronous resolver. This should prevent problems with code that
inadvertently depends on this behavior and which would break only when
compiled without support for asynchronous resolving.
