[$] Faster firewalls with bpfilter

Fromservers in a data center to desktop computers, many devicescommunicating on a network will eventually have to filter networktraffic, whether it's for security or performance reasons. As a result,this is a domain where a lot of work is put into improving performance:a tiny performance improvement can have considerable gains.Bpfilter is aproject that allows for packet filtering to easily be done with BPF, which canbe faster than other mechanisms.