ethtool

ethtool is a powerful utility for managing Ethernet device configurations in Linux environments. It allows administrators to query current settings and make changes to parameters such as link speed, duplex mode, auto-negotiation, Wake-on-LAN, and various offload features. This tool is essential for network troubleshooting, performance tuning, and hardware diagnostics.

Common use cases include adjusting interrupt coalescing parameters to optimize CPU usage, configuring RX/TX ring buffer sizes for high-throughput scenarios, enabling or disabling hardware offloads like TCP segmentation offload (TSO), and performing hardware self-tests. ethtool supports a wide range of network interface controllers and provides detailed statistics and diagnostic capabilities.

The tool interacts directly with kernel network drivers through the ethtool ioctl interface, making it a low-level utility for precise network interface control. It's particularly valuable in server environments, embedded systems, and performance-critical networking applications where fine-grained control over NIC behavior is required.

ethtool communicates with network drivers via the Linux ethtool kernel interface (SIOCETHTOOL ioctl). It sends commands to query or modify device-specific settings stored in driver private data structures. The tool supports standardized generic options (speed, duplex, autoneg) as well as driver-specific features through extended command sets. Operations like ring parameter changes modify queue depths and buffer allocations, while offload toggles enable/disable hardware acceleration for checksum calculation, packet segmentation, and flow classification. Diagnostic functions access hardware registers, EEPROM contents, and PHY status through MDIO/MDC interfaces.