Скачать или смотреть How to Set Up Loop Forwarding in DPDK using a Single NIC

Discover how to configure DPDK to enable loop forwarding with one NIC, ensuring TX packets can also be received on the same interface.
---
This video is based on the question https://stackoverflow.com/q/67957228/ asked by the user 'Alexcured' ( https://stackoverflow.com/u/16208018/ ) and on the answer https://stackoverflow.com/a/67968170/ provided by the user 'Vipin Varghese' ( https://stackoverflow.com/u/7665972/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to set a loop forwarding using one NIC to TX packets and RX them itself in DPDK testpmd?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Loop Forwarding in DPDK with a Single NIC

Setting up loop forwarding using DPDK (Data Plane Development Kit) can be quite a challenge, especially when you're trying to achieve it with just one Network Interface Card (NIC). Loop forwarding is essentially a technique where packets sent to a NIC are also received back on the same NIC, forming a loop. This technique can be useful for testing and debugging packet processing applications. In this post, we'll walk you through how to effectively implement a loop forwarding setup using just one NIC in a DPDK environment.

The Problem at Hand

In the original scenario, the goal was to create a packet flow where:

A packet is received in NIC's RXQ 0.

The NIC processes it and then sends it to its TXQ 0.

The packet needs to be sent back into NIC's RXQ 0, effectively completing a loop.

This sounds straightforward, but the challenge arises because DPDK typically expects multiple ports to establish a loop. However, with the right configuration and setup, you can still achieve this.

Solution: Configuring Loop Forwarding

Step 1: Configuration Requirements

To get started, you must ensure that your environment is set up correctly. Here are the requirements for implementing loop forwarding on a single NIC:

Dual Port Capable NIC: Though you're only using one port, the NIC should ideally support dual port capabilities for loopback scenarios.

Physical Connections: Implement one of the following configurations to facilitate RX and TX cross-connection:

Use a physical transceiver where the TX and RX are cross-connected.

If your NIC has an embedded switch, configure it in fabric loopback mode.

Connect your NIC to an external switch that supports MAC|PHY loopback.

Step 2: Setting Up DPDK

Now, once your NIC is physically connected in one of the aforementioned methods, proceed with setting up DPDK.

Begin by launching the DPDK application with the required parameters. Here’s an example command that reflects a proper setup for your test scenario:

[[See Video to Reveal this Text or Code Snippet]]

Key flags to set include --port-topology=loop, which establishes a logical loop within the DPDK software.

Step 3: Command Execution

After configuring your environment, the following commands need to be executed in sequence to activate loop forwarding:

Set the MAC Address: Use the set eth-peer command to define a target MAC address. For example:

[[See Video to Reveal this Text or Code Snippet]]

Toggle Forwarding Mode: Switch to the appropriate forwarding mode by executing:

[[See Video to Reveal this Text or Code Snippet]]

Start Packet Processing: Finally, initiate packet processing using:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Validation

To validate that the setup is working correctly, you might want to utilize an alternative way to run testpmd without a physical NIC. Here’s how to run a virtual interface instead:

[[See Video to Reveal this Text or Code Snippet]]

For detailed logging of received packets, increase verbosity by executing:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Setting up loop forwarding in DPDK with a single NIC is entirely achievable through careful configuration and the right physical setup. By following the steps outlined in this guide, you can create a functional loopback environment that efficiently manages packet reception and transmission back to the same port. Loop forwarding is a powerful tool for both testing and validation, enabling developers to simulate real-world traffic conditions within their applications.

If you have any questions or need further assistance with your DPDK configuration, feel free to reach out in the com