Simple closedexec forcer so that open sockets don't stay open for childs.

This was useful in PHP which was linked inside Apache, if one then did an exec() of sorts even port 80 would go to the forked process and thus port 80 would be occupied when one would restart Apache and then Apache would not start, the process would die and you did not have a webserver... very nasty especially because log rotations used to cause restarts
Simple old way of doing connection ratelimitting, eg to avoid brute force SSH attacks and limit too many SMTP connections from spambots hammering on your servers
New version of ratelimiting script:
 - uses new conntrack (xt_CT) module instead of old 'conntrack' module
 - uses a separate chain for permanent blocking and the actual ratelimiting
 - multiple ports can be specified with help from the multiport module