libnftnl (pre-requisite for nftables)

libnftnl is a userspace library providing a low-level netlink interface (API) to
the in-kernel nf_tables subsystem. The library libnftnl has been previously
known as libnftables. This library is currently used by nftables.

To benefit from libnftnl (but not to build it), you need a kernel that includes
the nf_tables subsystem (initial support >= 3.14).