  As the number of WiFi devices and their traffic demands continue to rise, the
need for a scalable and high-performance wireless infrastructure becomes
increasingly essential. Central to this infrastructure are WiFi Access Points
(APs), which facilitate packet switching between Ethernet and WiFi interfaces.
Despite APs' reliance on the Linux kernel's data plane for packet switching,
the detailed operations and complexities of switching packets between Ethernet
and WiFi interfaces have not been investigated in existing works. This paper
makes the following contributions towards filling this research gap. Through
macro and micro-analysis of empirical experiments, our study reveals insights
in two distinct categories. Firstly, while the kernel's statistics offer
valuable insights into system operations, we identify and discuss potential
pitfalls that can severely affect system analysis. For instance, we reveal the
implications of device drivers on the meaning and accuracy of the statistics
related to packet-switching tasks and processor utilization. Secondly, we
analyze the impact of the packet switching path and core configuration on
performance and power consumption. Specifically, we identify the differences in
Ethernet-to-WiFi and WiFi-to-Ethernet data paths regarding processing
components, multi-core utilization, and energy efficiency. We show that the
WiFi-to-Ethernet data path leverages better multi-core processing and exhibits
lower power consumption.
