Explore Ethernet cable diagnostics using the Netlink Ethtool API in this Linux Plumbers Conference talk. Delve into the high-level workings of cable fault detection, including break and short identification, and distance estimation. Learn about the challenges of non-standardized diagnostics across PHY vendors and the ongoing efforts to create a flexible, generic API through ethtool's netlink socket implementation. Discover how this API enables PHY-specific diagnostic tests and result reporting, with a focus on Marvell PHYs as examples. Gain insights into structured wiring, Time Domain Reflectometry (TDR), pulse techniques, and the rationale behind using ethtool for diagnostics. Understand the state machine, flow, and data handling in drivers and user space. Examine the potential applications for both copper and optical Ethernet cables, encouraging driver writers to implement diagnostics for various PHYs.