SYN flood produces HardFault about picotcp HOT 3 CLOSED

This happens because the listening socket ignores the backlog parameter passed to it and opens new connections until the heap meets the stack.

This is field that should limit the number of clients, but it's never used again.
s->max_backlog = backlog;

from picotcp.

I implemented next mechanism to avoid SYN flooding:
- limit number of pending connections to max_backlog
- waiting some time (15 seconds) and if the socket wasn't accepted => drop the pending connection.
- when max_backlog is reached, next SYNs received will be dropped until a pending connection will be dropped (15 seconds) or become accepted.

Waiting for Daniele feedback.

from picotcp.

PICO_SOCKET_BOUND_TIMEOUT changed from 15 seconds to 30 seconds.
All SYN flood tests passed => Issue closed.

from picotcp.