ICSim++: A CAN/CAN FD simulator for modern vehicle networks with LLM-assisted workflows

ICSim + + is an open-source CAN/CAN FD simulation platform designed to make vehicle-network experimentation more accessible, reproducible, and portable. It extends the original ICSim with (i) state-driven traffic generation from internal vehicle variables, (ii) segmented multi-bus network topologies connected via a virtual gateway, (iii) scriptable and repeatable experiment execution, (iv) enhanced logging with optional interpretive annotations, and (v) support for both Classical CAN and CAN FD. ICSim + + further introduces an optional LLM-assisted interaction layer for natural-language command generation and log interpretation, lowering the expertise barrier for CAN experimentation. Rather than targeting full vehicle or hardware-in-the-loop fidelity, ICSim + + focuses on message-, architectural-, and workflow-level fidelity sufficient for reproducible academic research and teaching. The software is publicly available, documented, and compatible with standard Linux SocketCAN workflows, making it suitable for automotive security experimentation, IDS evaluation, and education.