In some examples, a method includes parsing, by a network device, a section of source code associated with a network function provided by a middlebox in a network; extracting, by the network device, a packet processing slice and a state transition slice from the section of source code; generating, by the network device, a plurality of execution paths from the packet processing slice and the state transition slice; and modeling the middlebox by inserting, by the network device, the plurality of execution paths to a match-action table that describes a packet processing model for the middlebox.