In the highly dynamic and unpredictable environment of MANETs, cross-layer design is receiving growing interest but lacks experimental validation tools. This paper presents XIAN (Cross-layer Interface for wireless Ad hoc Networks), a generic framework for experimenting cross-layer designs in Linux testbeds with 802.11 wireless cards using the MadWifi driver. XIAN can be used as a service by other layers or system components to access MAC/PHY configuration and performance information. It provides experimenters with an open framework to create automatically complex metrics from both local and neighbour node measurements. The defined and implemented software architecture introduces the XIAN Nano-protocol and its automated management. We exemplify their benefits through the implementation of the well-known ETX (Expected Transmission count) metric and we provide results from real experimentations.