The present disclosure is directed to packet processing via reconfigurable packet processing system. A network device is configured to identify a processing order of multiple function units based on a first flow parameter of a first packet, execute a first function unit according to the processing order, update a processing status for the first packet to indicate processing by the first function unit is complete, and transmit the first packet responsive to determining from the processing status that the processing order has been completed. The network device is configured to receive a second packet including a second flow parameter, identify the second packet as a response packet of the first packet based on the first and second flow parameters, identify a reverse of the first processing order of the multiple function units, and execute a second function unit according to the reverse processing order.