Generic XDP Under Embedded SoC Constraints: A Lightweight L2 Data Plane with Cost Decomposition Analysis

With the proliferation of edge computing and the Internet of Things (IoT), embedded SoC devices are increasingly expected to provide data-plane functions such as network access, data aggregation, and Layer-2 forwarding. On resource-constrained platforms, however, the conventional Linux Bridge forwarding path traverses a relatively long protocol stack and bridging pipeline, incurring a high per-packet processing cost and making the system prone to CPU saturation under small-packet and high-concurrency workloads. Meanwhile, high-performance forwarding solutions designed for server environments often rely on specific hardware and driver capabilities; most legacy NICs in embedded deployments only support XDP in generic mode, making direct reuse of these solutions difficult. To address these challenges, this paper designs and implements a lightweight Layer-2 data-plane system based on XDP generic, tailored for embedded SoC constraints. The system performs minimal forwarding decisions early in the kernel receive path and streamlines the data-path structure via direct redirection, thereby reducing the structural overhead caused by repeated protocol-stack traversal. To provide a unified explanation for performance evolution across packet sizes, we further decompose the forwarding cost under the dual upper bounds of CPU capacity and link bandwidth. This framework characterizes the cost differences between XDP generic and Linux Bridge across workload regimes and elucidates the mechanism by which the bottleneck shifts from CPU-bound to bandwidth-bound operation. Experimental results on an RK3588 platform show that, under embedded generic-XDP constraints, the proposed design exhibits reproducible structural advantages over Linux Bridge in the CPU-bound small-packet and high-PPS regime, while the gap naturally narrows as the bottleneck shifts toward the link-bandwidth limit. These results indicate that, even under the strong constraints of XDP generic—where copy operations and sk_buff-related overheads remain—the forwarding path can still benefit from structural simplification in embedded environments. The study therefore provides empirical support for both the source of benefit and its applicability boundary and offers an explanatory framework for understanding lightweight Layer-2 forwarding on resource-constrained edge devices.