eHDL: Turning eBPF/XDP Programs into Hardware Designs for the NIC

Scaling network packet processing performance to meet the increasing speed of network ports requires software programs to carefully leverage the network devices' hardware features. This is a complex task for network programmers, who need to learn and deal with the heterogeneity of device architectures, and re-think their software to leverage them. In this paper we make first steps to reverse this design process, enabling the automatic generation of tailored hardware designs starting from a network packet processing program. We introduce eHDL, a high-level synthesis tool that automatically generates hardware pipelines from unmodified Linux's eBPF/XDP programs. eHDL is designed to enable software developers to directly define and implement the hardware functions they need in the NIC. We prototype eHDL targeting a Xilinx Alveo U50 FPGA NIC, and evaluate it with a set of 5 eBPF/XDP programs. Our results show that the generated pipelines are efficient in terms of required hardware resources, using only 6.5%-13.3% of the FPGA, and always achieve the line rate forwarding throughput with about 1 microsecond of per-packet forwarding latency. Compared to other network-specific high-level synthesis tool, eHDL enables software programmers with no hardware expertise to describe stateful functions that operate on the entire packet data. Compared to alternative processor-based solutions that perform eBFP/XDP offloading to a NIC, eHDL provides 10-100x higher throughput.