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# CNI - the Container Network Interface

## What is CNI?

The CNI (_Container Network Interface_) project consists of a specification and libraries for writing plugins to configure network interfaces in Linux containers, along with a number of supported plugins.
CNI concerns itself only with network connectivity of containers and removing allocated resources when the container is deleted.
Because of this focus, CNI has a wide range of support and the specification is simple to implement.

As well as the [specification](SPEC.md), this repository contains the Go source code of a library for integrating CNI into applications, an example command-line tool, a template for making new plugins, and the supported plugins.

The template code makes it straight-forward to create a CNI plugin for an existing container networking project.
CNI also makes a good framework for creating a new container networking project from scratch.

## Why develop CNI?

Application containers on Linux are a rapidly evolving area, and within this area networking is not well addressed as it is highly environment-specific.
We believe that many container runtimes and orchestrators will seek to solve the same problem of making the network layer pluggable.

To avoid duplication, we think it is prudent to define a common interface between the network plugins and container execution: hence we put forward this specification, along with libraries for Go and a set of plugins.

## Who is using CNI?

- [rkt - container engine](https://coreos.com/blog/rkt-cni-networking.html)
- [Kurma - container runtime](http://kurma.io/)
- [Kubernetes - a system to simplify container operations](http://kubernetes.io/docs/admin/network-plugins/)
- [Cloud Foundry - a platform for cloud applications](https://github.com/cloudfoundry-incubator/guardian-cni-adapter)
- [Weave - a multi-host Docker network](https://github.com/weaveworks/weave)
- [Project Calico - a layer 3 virtual network](https://github.com/projectcalico/calico-cni)
- [Contiv Networking - policy networking for various use cases](https://github.com/contiv/netplugin)
- [Mesos - a distributed systems kernel](https://github.com/apache/mesos/blob/master/docs/cni.md)

## Contributing to CNI

We welcome contributions, including [bug reports](https://github.com/containernetworking/cni/issues), and code and documentation improvements.
If you intend to contribute to code or documentation, please read [CONTRIBUTING.md](CONTRIBUTING.md). Also see the [contact section](#contact) in this README.

## How do I use CNI?

### Requirements

CNI requires Go 1.5+ to build.

Go 1.5 users will need to set GO15VENDOREXPERIMENT=1 to get vendored
dependencies. This flag is set by default in 1.6.

### Included Plugins

This repository includes a number of common plugins in the `plugins/` directory.
Please see the [Documentation/](Documentation/) directory for documentation about particular plugins.

### Running the plugins

The scripts/ directory contains two scripts, `priv-net-run.sh` and `docker-run.sh`, that can be used to exercise the plugins.

**note - priv-net-run.sh depends on `jq`**

Start out by creating a netconf file to describe a network:

```bash
$ mkdir -p /etc/cni/net.d
$ cat >/etc/cni/net.d/10-mynet.conf <<EOF
{
	"name": "mynet",
	"type": "bridge",
	"bridge": "cni0",
	"isGateway": true,
	"ipMasq": true,
	"ipam": {
		"type": "host-local",
		"subnet": "10.22.0.0/16",
		"routes": [
			{ "dst": "0.0.0.0/0" }
		]
	}
}
EOF
$ cat >/etc/cni/net.d/99-loopback.conf <<EOF
{
	"type": "loopback"
}
EOF
```

The directory `/etc/cni/net.d` is the default location in which the scripts will look for net configurations.

Next, build the plugins:

```bash
$ ./build
```

Finally, execute a command (`ifconfig` in this example) in a private network namespace that has joined the `mynet` network:

```bash
$ CNI_PATH=`pwd`/bin
$ cd scripts
$ sudo CNI_PATH=$CNI_PATH ./priv-net-run.sh ifconfig
eth0      Link encap:Ethernet  HWaddr f2:c2:6f:54:b8:2b  
          inet addr:10.22.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::f0c2:6fff:fe54:b82b/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:1 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:90 (90.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
```

The environment variable `CNI_PATH` tells the scripts and library where to look for plugin executables.

## Running a Docker container with network namespace set up by CNI plugins

Use the instructions in the previous section to define a netconf and build the plugins.
Next, docker-run.sh script wraps `docker run`, to execute the plugins prior to entering the container:

```bash
$ CNI_PATH=`pwd`/bin
$ cd scripts
$ sudo CNI_PATH=$CNI_PATH ./docker-run.sh --rm busybox:latest ifconfig
eth0      Link encap:Ethernet  HWaddr fa:60:70:aa:07:d1  
          inet addr:10.22.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::f860:70ff:feaa:7d1/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:1 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:90 (90.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
```

## What might CNI do in the future?

CNI currently covers a wide range of needs for network configuration due to it simple model and API.
However, in the future CNI might want to branch out into other directions:

- Dynamic updates to existing network configuration
- Dynamic policies for network bandwidth and firewall rules

If these topics of are interest, please contact the team via the mailing list or IRC and find some like-minded people in the community to put a proposal together.

## Contact

For any questions about CNI, please reach out on the mailing list:
- Email: [cni-dev](https://groups.google.com/forum/#!forum/cni-dev)
- IRC: #[containernetworking](irc://irc.freenode.org:6667/#containernetworking) channel on freenode.org