Graphs Backend

Table of Contents

• • Dependencies
  • Usage
  • Format of json output
  • Example

This backend produces visual representations of a P4 program as dot files. For now it supports the generation of graphs for top-level control and parser blocks, generation of fullGraph, which merges graphs for top-level program blocks and json representation of fullGraph.

dot files can be processed by the dot command from Graphviz, which can lay out the nodes and edges of the graphs and write the result in many different graphical file formats.

Dependencies

In addition to other P4C dependencies, this backend requires the Boost graph headers. On a Debian system, they can be installed with sudo apt-get install libboost-graph-dev.

Usage

mkdir out
p4c-graphs <prog.p4> --graphs-dir out
cd out
dot <name>.dot -Tpng > <name>.png

For generation of dot fullGraph, use option --fullGraph and for generation of fullGraph represented in json, use option --jsonOut.

Format of json output

Output in json format is an object with fields:

• info (object)
  • name - Filename of P4 program.
• nodes (array) - Contains objects, representing program blocks.
  • type - Type of program block. Valid values are "parser" and "control".
  • name - Name of program block.
  • nodes (array) - Contains object, representing nodes of CFG.
    • node_nmb - Index of given object in array nodes.
    • name - Node label.
    • type - Type of node.
    • type_enum - Enum value, representing type of node in backend p4c-graphs.
  • transitions (array) - Contains objects, representing transitions between nodes in nodes.
    • from - Index to node in nodes, from which edge starts.
    • to - Index to node in nodes, in which edge ends.
    • cond - Edge label.

Objects which represent program blocks are ordered in nodes, in the order in which they are defined in the main declaration of P4 program.

Example

Here is the graph generated for the ingress control block of the flowlet_switching-bmv2.p4 test program:

Flowlet switching ingress graph

Here is the graph generated for the egress control block of the flowlet_switching-bmv2.p4 test program:

Flowlet switching egress graph

Here is the graph generated for the parser block of the flowlet_switching-bmv2.p4 test program:

Flowlet switching ingress graph

Examples of generated fullGraph for flowlet_switching-bmv2.p4 program and firewall.p4 program can be found in resources, also with json fullGraph.