The present application describes a compiler of a network packet classification programming language that generates code for processors such as an application processor and a processing engine. The programming language includes a variety of instructions including an instruction to declare a network protocol and an instruction to specify a rule and at least one action to perform if the rule applies. A processor executing instructions generated by the compiler assigns values based on instructions to declare a network protocol and applies the rule instructions to received packets. The programming language may also include other instructions such as an instruction to search a set of values and identify whether an encapsulated packet header is present in a packet.