The netfilter.org project
What is the netfilter.org project? The netfilter project is a community-driven collaborative FOSS project that provides packet filtering software for the Linux 2.4.x and later kernel series. The netfilter project is commonly associated with iptables and its successor nftables. The netfilter project enables packet filtering, network address [and port] translation (NA[P]T), packet logging, userspace packet queueing and other packet mangling.
https://www.netfilter.org/
