Libipq

libipq is a development library for iptables userspace packet queuing. Libipq provides an API for communicating with ip_queue.
Libipq has been deprecated in favour of the newer libnetfilter_queue in Linux kernel-2.6.14 onwards.
Use in widely used software applications.
libipq has been used by some widely deployed applications as their interface to the Linux kernel-space iptables packet filter. 