testenv

Test environment script

This directory contains a setup script that you can use to create test environments for testing your XDP programs. It works by creating virtual ethernet (veth) interface pairs and moving one end of each pair to another network namespace. You can load the XDP program in the other namespace and send traffic to it through the interface that is visible in the root namespace.

Run ./testenv.sh with no parameter to get a list of available commands, or run ./testenv.sh --help to get the full help listing with all options. The script can maintain several environments active at the same time, and you can switch between them using the --name option.

If you don’t specify a name, the most recently used environment will be used. If you don’t specify a name when setting up a new environment, a random name will be generated for you.

Examples:

Setup new environment named “test”: ./testenv.sh setup --name=test

Create a shell alias for easy use of script from anywhere: eval $(./testenv.sh alias)

See the currently active environment, and a list of all active environment names (with alias defined as above): t status

Enter the currently active environment: t enter

Execute a command inside the environment: t exec -- ip a

Teardown the environment: t teardown

Understanding the network topology

When setting up a test environment, there will be a virtual link between the environment inside the new namespace, and the interface visible from the host system root namespace. The new namespace will be named after the environment name passed to the script, as will the interface visible in the outer namespace. The interface inside the namespace will always be named ‘veth0’.

To illustrate this, creating a test environment with the name ‘test01’ (with t setup --name test01 will result in the following environment being set up:

+-----------------------------+                          +-----------------------------+
| Root namespace              |                          | Testenv namespace 'test01'  |
|                             |      From 'test01'       |                             |
|                    +--------+ TX->                RX-> +--------+                    |
|                    | test01 +--------------------------+  veth0 |                    |
|                    +--------+ <-RX                <-TX +--------+                    |
|                             |       From 'veth0'       |                             |
+-----------------------------+                          +-----------------------------+

The ‘test01’ interface visible in the root namespace is the one we will be installing XDP programs on in the tutorial lessons. The XDP program will see packets being received on this interface; as you can see from the diagram, this means all packets being transmitted from inside the new namespace.

The setup is created this way to simulate the case where the host machine have physical interfaces; but instead of the traffic arriving from outside hosts on physical interfaces, they will arrive from inside the namespace on the virtual interface. This also means that when you generate traffic to test your XDP programs, you need to generate it from inside the test environment. The t ping command will start the ping inside the test environment by default, and you can run arbitrary programs inside the environment by using t exec -- <command>, or simply spawning a shell with t enter.