Libnetstack

AF_NETLINK sockets allow one to enumerate networking stack elements, and subscribe to events regarding changes, additions, and deletions thereof. Netlink is kind of a pain in the ass to work with directly, though. My libnetlink enumerates all existing networking stack elements, subscribes to events, and makes all of this available to the user via queries and/or realtime callbacks. libnetstack has been designed to provide responsive service even in the presence of millions of routes with rapid churning of the route tables.

Code lives at https://github.com/dankamongmen/libnetstack.