Packet processing match and action pipeline structure with dependency calculation removing false dependencies
An embodiment of the invention includes a plurality of tables in a hardware network for performing packet processing. Each table in the plurality of tables includes a table declaration. The table declaration includes a first set of fields used for input matching and a second set of fields used as inputs for action processing. A first table is selected from the plurality of tables. Successor tables to the first table are selected from the plurality of tables. There is a third set of fields for each successor table of the successor tables. The contents of the third set of fields are output fields where the output fields are modified by the first table when a next table of the first table is the successor table of the first table.
1. Hardware architecture for performing packet processing comprising:
an ingress processor;
a plurality of match and action stages wherein data parsed from header fields of a packet are presented to a first match and action stage from the plurality of match and action stages;
a plurality of tables wherein each table in the plurality of tables comprises:
a table declaration, the table declaration comprising:
a first set of fields used as inputs for matching processing;
a second set of fields used as inputs for action processing;
a first table, the first table selected from the plurality of tables;
an egress processor;
successor tables to the first table, the successor tables selected from the plurality of tables;
wherein the first match and action stage chooses a subset of the packet header fields, performs an associative match in the first table, and as a result of a match, performs actions which modify the packet header fields;
wherein packet processing proceeds with modified packet header fields flowing through a succession of match and action stages of the plurality of match and action stages, wherein each match and action stage in the succession of match and action stage of the plurality of match and action stages chooses different fields to match against and modifies a different selection of fields;
wherein modified output ports are declared separately for each possible table destination.
2. The hardware architecture of claim 1 wherein match dependencies between the first table and the successor table are calculated as an intersection between the modified output fields of the first table for the successor table and the first set of fields that are used as inputs for matching by the successor table.
3. The hardware architecture of claim 2 wherein action dependencies between the first table and the successor table are calculated as an intersection between the modified output fields of the first table for the successor and the set of fields that are used as inputs for action processing by the successor table.