Port flipping

Hi Robin,

I have a problem where a connection missing its SYN is not flipped correctly, because the client happened to choose a port that Bro thinks is a server port (IRC, 6666). What is confusing me is the special case in NetSessions::WantConnection() that prevents the flip. Your comments are about avoiding being confused by stealth scans, but I think that the flip will happen in every case except when the client is unlucky enough to use a “server” port number. Given that is most of the time, why have the special case at all?