P4 language extensions for stateful packet processing

The P4 language is the de facto standard to define how programmable switches must process packets. P4 is extensively employed in datacenter scenarios as it permits to support a wide set of network applications. However, P4 does not provide a clear description of stateful processing, especially on handling per-flow states. This paper extends both the P4 language and the P4 software switch (bmv2) with novel stateful primitives with a clear representation of per-flow states. Furthermore, we exploit these new functionalities by implementing a datacenter network function that implements a scalable tunneling mechanism. The developed network function differentiates the top talker flows directly handled by the switch and the other flows that are instead managed in a slow path involving specific network devices with large connection tables.