Start a new handshake from the server if we get an unknown ack.

If a client times out for some reason, or the server restarts, then the
server might get a packet for an unknown session that the client thinks
is valid.  Send a handshake packet with a fresh cookie in that case, to
tell the client it should resync.

Change-Id: I82d567b293043d30a3d687a3794d3b50123319e7
2 files changed