Some emerging applications in mobile ad hoc networks (MANETs) and mobile sensor networks (MSNs) have varying mobility patterns that entails different routing strategies at different times to maintain high performance. This requires the routing protocol to adapt to different situations for better overall routing performance. We propose a model-based approach to enable such situation-awareness for the Dynamic Source Routing (DSR) protocol in such challenging environments. Our model captures the access behavior of route cache (hit, miss, and false hit) and is simple enough to be used in real-world settings. We also present a feedback-based architecture that uses the model outputs to cope with mobility changes by adjusting caching strategy on-the-fly. We validate our model against ns-2 simulations for a variety of scenarios, including a real-world mobility. Our results show that the model can aptly drive adaptive routing that leads to consistent performance improvement over DSR for the scenarios considered.