Document how to add table entries to P4 DPDK using its native control plane API

[jafingerhut]

Building P4 DPDK, compiling a program for it using p4c-dpdk, and loading it into the P4 DPDK data plane has a repo documenting the steps here: https://github.com/Yi-Tseng/p4-dpdk-target-notes

Perhaps it is also documented how to add/modify/remove table entries into the data plane from a control program, but if so, I have not found it yet. Making an example of that would be useful.

If this were documented, it could help enable running automated CI tests on the P4 DPDK data plane in the https://github.com/p4lang/p4c repo, thus significantly improving test coverage of the P4 DPDK data plane, and p4c-dpdk compiler back end.

[jafingerhut]

Note: I have instructions here: https://github.com/jafingerhut/p4-guide/tree/master/ipdk

on how to install software called IPDK (Infrastructure Programmer Development Kit) that includes a P4Runtime API server with the P4 DPDK data plane, and for many kinds of table entries you can add/modify/remove them via a control program using the P4Runtime API protocol, similar to what you can do with simple_switch_grpc.

However, the last version of IPDK that I have been able to build from open source components was released in 2023-Jul, and as far as I can tell only the Intel IPU-specific version of IPDK has later versions released, not the purely open source part that interoperates with the P4 DPDK data plane. I would be happy if someone could demonstrate how to build more recent versions of IPDK released later than 2023-Jul that work with the P4 DPDK data plane.

Note: The instructions at the link above may say version 24.01 (from 2024-Jan) in them, but as far as I can tell that version still installs version 23.07 (from 2023-Jul) of most of the software.

[Vineet1101]

@jafingerhut I am working on it. Will submit a pr soon. Anything more you want to tell regarding the documentation

[jafingerhut]

I think a perfect example would be one that includes:

• A simple P4 program that has at least two tables:
  • one table that has 2 or 3 key fields, all exact match. If a table entry is added, make a simple action for entries that modifies the Ethernet header's source MAC address to the value of an action parameter. The default action should be NoAction, so that if a packet is processed and no table entry is matched, nothing in the packet is modified, and it is NOT dropped.
  • one table that has 2 or 3 key fields, all ternary match. Same as table above on action, except the hit action should modify a different packet field, e.g. the destination MAC address.
• A simple control plane program that successfully adds two example table entries, to each of the two tables mentioned above. Ideally it should also be able to read the table entries and print them out in some simple way.
• Instructions for compiling the P4 program, loading it into the P4 DPDK data plane, running the control plane program, then using Scapy or some other simple program that creates simple test packets to send in, and capture the output packets, and verify that the packet source and/or dest MAC addresses are changed in the expected ways, based on the packet contents and the actions that should have been executed.

Having all of that gives a way for someone to TRY OUT the example, rather than just reading about it. They can verify whether it works as written. Then from that starting point they can make simple changes to the P4 program and/or control plane program to try out their own variations.

Being able to try out the example is also a good way to check that the instructions actually work. WIthout having some test packets that have different behavior for packets that match a table entry and execute its action, vs. missing and executing NoAction, it is easy to write a control plane program that fails to add table entries, but you cannot tell that it fails.

[Vineet1101]

Hey @jafingerhut i have written the complete guide in which repo should i create the pull request??

[jafingerhut]

Hey @jafingerhut i have written the complete guide in which repo should i create the pull request??

Good question. I would recommend before creating a PR, to create an issue on this repository https://github.com/p4lang/p4-dpdk-target and ask this question to the maintainers of that repository to see if they think p4-dpdk-target is a good place, or if they would recommend some other place.

You can alert these people in the comment of the issue you create, to get their attention: swaroopsarma riyazahm22 jafingerhut (but put an @ in front of each of those Github user id names, to cause them to be notified. I did not put the @ here because I do not want to notify them about this comment).

[jafingerhut]

Feel free to mention that I suggested that you ask them, in case that helps get their attention sooner.

[Vineet1101]

@jafingerhut, can I use IPDK to run P4 DPDK programs and also add them in the documentation, or do I have to use the instructions given in the P4 DPDK repo and also IPDK uses docker as well as native installation methods while docker one is easy and fast to setup the native one gives more control so which method should I document and try??

[Dscano]

@jafingerhut, can I use IPDK to run P4 DPDK programs and also add them in the documentation, or do I have to use the instructions given in the P4 DPDK repo and also IPDK uses docker as well as native installation methods while docker one is easy and fast to setup the native one gives more control so which method should I document and try??

@Vineet1101 you should use only P4 DPDK, IPDK is an external project to the P4 ecosystem. This project idea was proposed with the goal of improving the P4 DPDK documentation and enabling automated CI tests for the P4 DPDK data plane.

So your starting work is correct: #27 (comment)

[Vineet1101]

@Dscano ok so I will use all the installation details mention in p4 dpdk repo

[Vineet1101]

@Dscano is there any document which I can refer to get some idea on adding and modifying tables?? or any other material

[Dscano]

@Dscano is there any document which I can refer to get some idea on adding and modifying tables?? or any other material

Hi @Vineet1101 ,

Do you mean installing and/or removing flow rules or modifying tables in P4 code? If you are referring to the first case, in the p4-dpdk-target/examples/ directory, you can find some BF_RT commands that are used to configure the P4 program tables.

[Dscano]

The installation script for p4-dpdk has been merged here: p4lang/p4-dpdk-target#116. However, documentation is still missing on how to install a P4 pipeline, add table entries, etc.

[Vineet1101]

@Dscano I am working on it will submit the following PR soon