Introduces the Lua scripting environment

Netfilter is the component of the Linux kernel that is used when the network traffic needs to be inspected and/or manipulated. More specifically, Netfilter inserts five hooks into the networking stack (see Figure 2.1) :
• PREROUTING: All packets traverse this hook. It is called before any routing decision is made, but after all IP header sanity checks have succeeded. Typically, Port Address Translation (PAT), the redirection of packets, as well