AirXDP: A Flexible and Efficient User-Space Data Plane for WiFi Access Points

WiFi Access Points (APs) process and switch packets between the WiFi and Ethernet interfaces. These operations are managed by the Linux kernel's data plane; however, the kernelbased packet switching is inherently complex and challenging to monitor and modify. To address the growing demands for WiFi applications and services, and in particular to foster innovation in advancements of the data plane for WiFi APs, this work introduces AirXDP, a user-space packet switching architecture that leverages Linux's eXpress Data Path (XDP) framework. In this paper, we first present the AirXDP system architecture and the details of packet processing engine in the user-space. Next, we identify and address key limitations, such as the overhead caused by excessive polling of ingress queues as well as the increased RTTs resulting from standing queues. Through empirical and analytical evaluations, we demonstrate that techniques such as optimizing polling intervals, configuring core affinities, efficiently managing queues, and using XDP's native attach mode even on one interface enable AirXDP to achieve higher processing efficiency compared to packet switching performed by the Linux kernel. Overall, AirXDP provides an efficient packet switching framework for facilitating the enhancement of WiFi AP's data plane.