At the core of fast network packet processing lies the ability to filter packets, or in other words, to apply a set of rules on packets, usually consisting of a pattern to match (L2 to L4 source and destination addresses and ports, protocols, etc.) and corresponding actions (redirect to a given queue, or drop the packet, etc.). Over the years, several filtering frameworks have been added to Linux. While at the lower level, ethtool can be used to configure N-tuple rules on the receive side for the hardware, the upper layers of the stack got equipped with rules for firewalling (Netfilter), traffic shaping (TC), or packet switching (Open vSwitch for example).

This presentation reviews the needs for those filtering frameworks and the particularities of each one. Then it focuses on the changes brought by eBPF and XDP in this landscape: as BPF programs allow for very flexible processing and can be attached very low in the stack—at the driver level, or even run on the NIC itself—they offer filtering capabilities with no precedent in terms of performance and versatility in the kernel. Lastly, the third part would explore potential leads in order to create bridges between the different rule formats and to make it easier for users to build their filtering eBPF programs.