Optimized datapath troubleshooting with trace policy engine

A method implemented by a switch in a Software Defined Networking (SDN) network to trace packets, where the switch includes a packet processing pipeline that includes a plurality of flow tables, the method comprising:

• receiving a packet;
• determining, at a first flow table of the packet processing pipeline, whether the packet is a trace packet that was recirculated based on content of a first field associated with the packet;
• in response to the determination that the packet is a trace packet that was recirculated, the method further comprises:
• setting a first field associated with the packet to indicate that tracing is disabled for the packet, and
• setting a second field associated with the packet to indicate that tracing is enabled for the packet, determining a flow table of the packet processing pipeline from which the packet was recirculated, and directing the packet to the flow table from which the packet was recirculated;
• and
• in response to the determination that the packet is not a trace packet that was recirculated, the method further comprises:
• determining, at the first flow table, whether the packet is to be traced through the packet processing pipeline;
• and
• creating a copy of the packet, setting a first field associated with the copy of the packet to indicate that tracing is enabled for the copy of the packet, outputting the copy of the packet to a recirculate port, and directing the packet to a subsequent flow table of the packet processing pipeline in response to a determination that the packet is to be traced through the packet processing pipeline.