An UDP packet is periodically sent from one board to another using a real time thread. The receiving board uses the SO_TIMESTAMPING option to see when the packet entered the kernel, and generates timestamps with clock_gettime once the packets enters userspace to compute the time the packet spent in kernel and user space.
**Common test metadata:** Linux kernel version: 4.19, Boot Parameters: isolcpus, Interval: 1000us, ETF qdisc delta: 160us, Task priority: 99, Device and processor load: ssh, Test duration: 0h59, qdisc: etf, etf_offset: 600us, route: switch