We present a verified compiler for stateless firewall policies. The policy is first compiled into an intermediate representation taking the form of a binary decision diagram that is optimised in terms of decision nodes. The decision diagram is then compiled into a Clight program. The compiler is proved correct using the Coq proof assistant and extracted into OCaml code. Our preliminary experiments show promising results. The compiler generates code for relatively large firewall policies and the generated code outperforms a sequential evaluation of the policy rules.