Znail is a network emulator inteded to run on a computer with two network interfaces. Equipped with two network interfaces, Znail acts as a network bridge. Znail can then control network traffic passing through the bridge.

With a system under test connected to the network through this bridge, Znail can help you answer question about how that system behaves under various network conditions.

• Emulate packet delay
• Emulate packet loss
• Emulate packet duplication
• Emulate packet reordering
• Emulate packet corruption
• Control packet rate
• Capture network packets
• Emulate a disconnect (by powering down one of its network interfaces)
• Override answers to DNS queries (by redirecting DNS traffic to its internal DNS server)
• Redirect IP traffic from one host to another
• Not apply any of the above for certain hosts using a whitelist

Znail can be managed in one of two ways, using its web interface or its REST API.

The easiest way to get started with Znail is to download an image with Znail pre-installed.

The image can then be installed on a suitable target system, for example a Raspberry Pi or a NanoPi R2S.

The default SSH username for the pre-built image is pi and the password is raspberry.

The default SSH username for the pre-built image is root and the password is 1234.

To set up the environment on an Ubuntu 20.04 system, run the following commands:

sudo apt update
sudo apt install -y coreutils quilt parted qemu-user-static debootstrap zerofree zip dosfstools bsdtar libcap2-bin grep rsync xz-utils file git curl

To generate an image:

make image

The resulting images can be found in the dist/image directory.

Generating the different images can take quite some time. If you are looking to only build one specific kind of image more narrow make targets are available. See make help for more information.

The Python environment requires that the pip tool is installed.

To set up the development environment on an Ubuntu 20.04 system, run the following commands:

sudo apt update
sudo apt install -y python3-pip python3-venv

To build and activate the virtual Python environment:

source ./activate

To automatically format the code:

make format

To run tests and static code analysis:

make check

More information about what targets the build system provides:

make help

Special thanks to Alice Persson for contributing the Znail logotype.

Distributed under the terms of the Apache License 2.0.