libnfnetlink is the low-level library for netfilter related 
kernel/userspace communication. It provides a generic messaging
infrastructure for in-kernel netfilter subsystems (such as 
nfnetlink_log, nfnetlink_queue, nfnetlink_conntrack) and their 
respective users and/or management tools in userspace.
This library is not meant as a public API for application 
developers; it is only used by other netfilter.org projects.