/t4p4s

Retargetable compiler for the P4 language

Primary LanguageCApache License 2.0Apache-2.0

P4@ELTE/p4c User Guide

P4@ELTE is a small, university based research team at Eötvös Loránd University, Budapest, Hungary. p4c is our retargetable compiler for P4.

Required software

Common pitfalls

  • Do not forget to set the RTE_SDK environment variable to the directory of your DPDK.
  • DPDK will need pcap header files (you can get them by installing pcap, e.g. the libpcap-dev package)
  • You may also need the setuptools Python package for a successful HLIR install.

Running the examples

To execute the commands below, a root or sudoer account is necessary. In the latter case, the system will ask for your password when you run it for the first time.

The most comfortable, all-inclusive choice is to run launch.sh (with proper parameters, see below). This will compile and run the switch in one go.

./launch.sh <P4 file> <controller> <controller params file> -- <DPDK parameters>
  • The controller is predefined for the examples, and can be omitted.
  • You may have to use different DPDK settings to make the following examples work on your system.
  • You can find more information about DPDK command line options here.
## Test examples (will work without any real network configuration)

# using the L2 example without a real network configuration
P4DPDK_VARIANT=no_nic_l2 ./launch.sh ./examples/l2_switch_test.p4 -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""

# using the L3 example without a real network configuration
P4DPDK_VARIANT=no_nic_l3 ./launch.sh ./examples/l3_routing_test.p4 -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""

# the same as above, with verbose output
P4_GCC_OPTS="-DP4DPDK_DEBUG" P4DPDK_VARIANT=no_nic_l3 ./launch.sh ./examples/l3_routing_test.p4 -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""


## The following examples will only work if you have a real network configuration with DPDK

# supplying DPDK options directly
./launch.sh examples/l3_routing_test.p4 -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""

# supplying DPDK options via environment variable
export P4DPDK_OPTS="-c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config \"(0,0,0),(1,0,1)\""
./launch.sh examples/l3_routing_test.p4

# using the L3 example with a configuration file for the control plane
# and manual specification of the controller ("dpdk_controller")
./launch.sh ./examples/l3_routing_test.p4 dpdk_controller examples/l3_switch_test_ctrl.txt -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""

# verbose output
# "default" means that we use the default controller (applicable to example programs only)
P4_GCC_OPTS="-DP4DPDK_DEBUG" ./launch.sh ./examples/l3_routing_test.p4 default -- -c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config "\"(0,0,0),(1,0,1)\""

Running the examples, details

You can compile, make and run the code in separate steps.

  1. Compile the P4 file into C code using compile.sh and setup files for make.

    • The compiled files are placed within the directory build/<P4-source-name>.
    ./compile.sh examples/l3_routing_test.p4

  2. Run make in the directory build/<P4-source-name>.

    • The executable file is generated as build/<P4-source-name>/build/<P4-source-name>.

  3. Run the executable.

    • If you prefer to do so, you can invoke the generated executable directly.
    • As the executable will require a controller to function, there is a convenience script run.sh that you can invoke. For each example, the appropriate controller is started before running the switch.
    • The parameters for run.sh are the same as for launch.sh except for the first one: here, you have to supply the name of the generated executable.
    ./run.sh ./build/l3_routing_test/build/l3_routing_test -- -c 0xf -n 1 --log-level 3 -- -P -p 0x3

# supplying DPDK options via environment variable
export P4DPDK_OPTS="-c 0x3 -n 4 - --log-level 3 -- -p 0x3 --config \"(0,0,0),(1,0,1)\""
./run.sh ./build/l3_routing_test/build/l3_routing_test

Environment variables

You can set the following parameters via environment variables.

  • In general, for DPDK
    • RTE_SDK: the directory of DPDK
    • RTE_TARGET: the target architecture, will default to x86_64-native-linuxapp-gcc if unspecified
  • Relevant in the make step
    • MAKE_CMD
      • You can specify a program other than make to be invoked.
    • P4DPDK_GCC_OPTS
      • You can specify additional parameters for your compiler.
      • To see debug messages, include -NP4DPDK_DEBUG in its contents.
    • P4DPDK_VARIANT
      • Possible values are no_nic_l2 and no_nic_l3 (or leave it unset).
      • Causes src/hardware_dep/dpdk/main_loop_<variant>.c to replace src/hardware_dep/dpdk/main_loop.c during compilation.
      • Mainly used for testing purposes, for DPDK installations without a real network environment.
  • Relevant in run.sh
    • P4DPDK_OPTS: DPDK options for the compiled switch
      • If set, this overrides the parameters given after the first -- on the command line of launch.sh.

Limitations

This compiler supports P414. An upcoming compiler will include further support for P416.

Please note that the following language elements are not (fully) supported yet:

  • calculated/variable length fields
  • saturating fields
  • masked field modification
  • action profiles
  • parser exceptions
  • checksums
  • meters and registers
  • resubmission and cloning

Experimental branch

The experimental branch contains preliminary implementations of features. Currently, the branch contains the following:

  • registers
    • registers bigger than 32 bits are not supported
    • registers with layout or binding are not supported