Optimizations

[dc3-tsd]

This merge request contains some optimizations to help improve processing speed.

This was made after the discovery that if dshell can't determine when a connection is closed, it will hold onto the connection in the _connection_tracker. This was causing the _connection_handler() to slow down proportionally to the number of lingering open connections.

This caused a 244 MB pcap to take multiple hours to complete. After these changes, processing only took 20 minutes.

• Added a limiter to timeout connections if a maximum of 1000 (arbitrarily determined) connections is hit. (This goes along with the 1 hour timeout already implemented.)
• Set the check for timing out connections to happen after every 300 packets instead of being run with each packet.
• Set produce_packets() to be run even on the last plugin in the chains. This is to ensure resources are periodically cleaned up and we don't miss handling a lingering connection.
• Moved connection handling to occur during produce_connections() and set _connection_queue to be a priority queue to help ensure connections are processed in order relative to packet capture.

[dev195]

These changes look good and will be merged shortly.

A useful future feature might be to allow users to change the max connections and timeout values from the command-line, if they have the need and available memory for it.