This import includes The basic blacklist library and utility programs,
to add a system-wide packet filtering notification mechanism to
FreeBSD.
The rational behind the daemon was given by Christos Zoulas in a
presentation at vBSDcon 2015: https://youtu.be/fuuf8G28mjs
Reviewed by: rpaulo
Approved by: rpaulo
Obtained from: NetBSD
Relnotes: YES
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D5912
