pf integration


BGP is efficient distributing lists of network prefixes
 
bgpd can add prefixes learned from neighbors into a pf table
prefixes are selected using the bgpd filter language
tables use a radix tree, fast even with lots of entries

pf tables can be used for pretty much anything
packet filtering
redirection to spamd (BGP distributed spam blacklists)
QoS processing

http://www.bgp-spamd.net/ uses that