Segment Routing with IPv6 (SRv6) is a leading Hybrid SDN (HSDN) architecture, as it fully exploits standard IP routing and forwarding both in the control plane and in the data plane. In this paper we design, implement and evaluate a programmable data plane solution for Linux routers called HIKE (HybrId Kernel/eBPF forwarding), integrated in an HSDN/SRv6 architecture. HIKE integrates the conventional Linux kernel packet forwarding with custom designed eBPF/XDP (extended Berkeley Packet Filter/eXtreme Data Path) bypass to speed up performance of SRv6 software routers. Thus, in addition to the hybrid IP/SDN forwarding, we foster an additional hybrid approach inside a Linux forwarding engine combining eBPF/XDP and kernel based forwarding, taking the best from both worlds. Therefore, considering the two different conceptual levels of hybridization, we call our overall solution Hybrid squared or Ĥ2. We have applied the Ĥ2 solution to Performance Monitoring (PM) in Hybrid SDNs, and we show how our HIKE data plane architecture supports SRv6 networking and Performance Monitoring (in particular Loss Monitoring) allowing a significant increase in performance: our implementation results show a remarkable throughput improvement (5x) with respect to a conventional Linux based solution. © 2020