emqx / esockd / 456

Pull #196

github

feat: enhance connection rate limit

Prior to this change, if connection rate is limited, the acceptors
will enter suspending state and stop accepting the sockets
leaving the sockets in the system backlog.

If the acceptor backlog (default=1024) is filled up, for long enough
time to cause the majority of the clients to have closed socket from
their end and try to reconnect aggressively, the acceptor may never
be able to get a normal socket again.

The fix is: in suspending state, accept the sockets and immediately
cose them to free up the backlog.
The close triggers TCP-RST to cut the TCP graceful close overheads.

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