NTP broadcasts break NTP synchronization (RTEMS)

[Ralph Lange]

The code that implements the NTP request based sync binds the receiver to the well-known NTP port 123 (instead of using an epheremal port). That way the receiver will not only get the answers to the requests, but also all broadcasts on the network. All incoming traffic is buffered in the socket, and the NTP sync code pulls out an old broadcast instead of the answer to its most recent request, thereby effectively stopping the IOC time. (generalTime does not allow backward jumps in time, but will stop advancing until the NTP answer eventually catches up.)

In other words: NTP broadcasts on the IOC network break the NTP synchronization.

[mdavidsaver (mdavidsaver)]

Switch the port which the RTEMS NTP client uses when sending requests to a random (>1024) port.

[Ralph Lange (ralph-lange)]

Pushed Michael Davidsaver's fix to the 3.14 branch.