Open Virtual Networking With Docker

This document describes how to use Open Virtual Networking with Docker 1.9.0 or later.

Important

Requires Docker version 1.9.0 or later. Only Docker 1.9.0+ comes with support for multi-host networking. Consult www.docker.com for instructions on how to install Docker.

Note

You must build and install Open vSwitch before proceeding with the below guide. Refer to Installing Open Virtual Network (OVN) for more information.

Setup

For multi-host networking with OVN and Docker, Docker has to be started with a distributed key-value store. For example, if you decide to use consul as your distributed key-value store and your host IP address is $HOST_IP, start your Docker daemon with:

$ docker daemon --cluster-store=consul://127.0.0.1:8500 \
    --cluster-advertise=$HOST_IP:0

OVN provides network virtualization to containers. OVN’s integration with Docker currently works in two modes - the “underlay” mode or the “overlay” mode.

In the “underlay” mode, OVN requires a OpenStack setup to provide container networking. In this mode, one can create logical networks and can have containers running inside VMs, standalone VMs (without having any containers running inside them) and physical machines connected to the same logical network. This is a multi-tenant, multi-host solution.

In the “overlay” mode, OVN can create a logical network amongst containers running on multiple hosts. This is a single-tenant (extendable to multi-tenants depending on the security characteristics of the workloads), multi-host solution. In this mode, you do not need a pre-created OpenStack setup.

For both the modes to work, a user has to install and start Open vSwitch in each VM/host that they plan to run their containers on.

The “overlay” mode

Note

OVN in “overlay” mode needs a minimum Open vSwitch version of 2.5.

Start the central components.

OVN architecture has a central component which stores your networking intent in a database. On one of your machines, with an IP Address of $CENTRAL_IP, where you have installed and started Open vSwitch, you will need to start some central components.

Start ovn-northd daemon. This daemon translates networking intent from Docker stored in the OVN_Northbound database to logical flows in OVN_Southbound database. For example:
$ /usr/share/ovn/scripts/ovn-ctl start_northd
With Open vSwitch version of 2.7 or greater, you need to run the following additional commands (Please read the manpages of ovn-nb for more control on the types of connection allowed.)
$ ovn-nbctl set-connection ptcp:6641
$ ovn-sbctl set-connection ptcp:6642

One time setup

On each host, where you plan to spawn your containers, you will need to run the below command once. You may need to run it again if your OVS database gets cleared. It is harmless to run it again in any case:
```
$ ovs-vsctl set Open_vSwitch . \
    external_ids:ovn-remote="tcp:$CENTRAL_IP:6642" \
    external_ids:ovn-nb="tcp:$CENTRAL_IP:6641" \
    external_ids:ovn-encap-ip=$LOCAL_IP \
    external_ids:ovn-encap-type="$ENCAP_TYPE"
```
where:
$LOCAL_IP
is the IP address via which other hosts can reach this host. This acts as your local tunnel endpoint.

$ENCAP_TYPE
is the type of tunnel that you would like to use for overlay networking. The options are geneve or stt. Your kernel must have support for your chosen $ENCAP_TYPE. Both geneve and stt are part of the Open vSwitch kernel module that is compiled from this repo. If you use the Open vSwitch kernel module from upstream Linux, you will need a minimum kernel version of 3.18 for geneve. There is no stt support in upstream Linux. You can verify whether you have the support in your kernel as follows:
$ lsmod | grep $ENCAP_TYPE
In addition, each Open vSwitch instance in an OVN deployment needs a unique, persistent identifier, called the system-id. If you install OVS from distribution packaging for Open vSwitch (e.g. .deb or .rpm packages), or if you use the ovs-ctl utility included with Open vSwitch, it automatically configures a system-id. If you start Open vSwitch manually, you should set one up yourself. For example:
```
$ id_file=/etc/openvswitch/system-id.conf
$ test -e $id_file || uuidgen > $id_file
$ ovs-vsctl set Open_vSwitch . external_ids:system-id=$(cat $id_file)
```
Start the ovn-controller.

You need to run the below command on every boot:
```
$ /usr/share/ovn/scripts/ovn-ctl start_controller
```
Start the Open vSwitch network driver.

By default Docker uses Linux bridge for networking. But it has support for external drivers. To use Open vSwitch instead of the Linux bridge, you will need to start the Open vSwitch driver.

The Open vSwitch driver uses the Python’s flask module to listen to Docker’s networking api calls. So, if your host does not have Python’s flask module, install it:
```
$ sudo pip install Flask
```
Start the Open vSwitch driver on every host where you plan to create your containers. Refer to the note on $OVS_PYTHON_LIBS_PATH that is used below at the end of this document:
```
$ PYTHONPATH=$OVS_PYTHON_LIBS_PATH ovn-docker-overlay-driver --detach
```
Note

The $OVS_PYTHON_LIBS_PATH variable should point to the directory where Open vSwitch Python modules are installed. If you installed Open vSwitch Python modules via the Debian package of python-openvswitch or via pip by running pip install ovs, you do not need to specify the PATH. If you installed it by following the instructions in OVN on Linux, FreeBSD and NetBSD, then you should specify the PATH. In this case, the PATH depends on the options passed to ./configure. It is usually either /usr/share/openvswitch/python or /usr/local/share/openvswitch/python

Docker has inbuilt primitives that closely match OVN’s logical switches and logical port concepts. Consult Docker’s documentation for all the possible commands. Here are some examples.

Create a logical switch

To create a logical switch with name ‘foo’, on subnet ‘192.168.1.0/24’, run:

$ NID=`docker network create -d openvswitch --subnet=192.168.1.0/24 foo`

List all logical switches

$ docker network ls

You can also look at this logical switch in OVN’s northbound database by running the following command:

$ ovn-nbctl --db=tcp:$CENTRAL_IP:6640 ls-list

Delete a logical switch

$ docker network rm bar

Create a logical port

Docker creates your logical port and attaches it to the logical network in a single step. For example, to attach a logical port to network foo inside container busybox, run:

$ docker run -itd --net=foo --name=busybox busybox

List all logical ports

Docker does not currently have a CLI command to list all logical ports but you can look at them in the OVN database by running:

$ ovn-nbctl --db=tcp:$CENTRAL_IP:6640 lsp-list $NID

Create and attach a logical port to a running container

$ docker network create -d openvswitch --subnet=192.168.2.0/24 bar
$ docker network connect bar busybox

Detach and delete a logical port from a running container

You can delete your logical port and detach it from a running container by running:

$ docker network disconnect bar busybox

The “underlay” mode

Note

This mode requires that you have a OpenStack setup pre-installed with OVN providing the underlay networking.

One time setup

A OpenStack tenant creates a VM with a single network interface (or multiple) that belongs to management logical networks. The tenant needs to fetch the port-id associated with the interface via which he plans to send the container traffic inside the spawned VM. This can be obtained by running the below command to fetch the ‘id’ associated with the VM:
```
$ nova list
```
and then by running:
```
$ neutron port-list --device_id=$id
```
Inside the VM, download the OpenStack RC file that contains the tenant information (henceforth referred to as openrc.sh). Edit the file and add the previously obtained port-id information to the file by appending the following line:
```
$ export OS_VIF_ID=$port_id
```
After this edit, the file will look something like:
```
#!/bin/bash
export OS_AUTH_URL=http://10.33.75.122:5000/v2.0
export OS_TENANT_ID=fab106b215d943c3bad519492278443d
export OS_TENANT_NAME="demo"
export OS_USERNAME="demo"
export OS_VIF_ID=e798c371-85f4-4f2d-ad65-d09dd1d3c1c9
```
Create the Open vSwitch bridge

If your VM has one ethernet interface (e.g.: ‘eth0’), you will need to add that device as a port to an Open vSwitch bridge ‘breth0’ and move its IP address and route related information to that bridge. (If it has multiple network interfaces, you will need to create and attach an Open vSwitch bridge for the interface via which you plan to send your container traffic.)

If you use DHCP to obtain an IP address, then you should kill the DHCP client that was listening on the physical Ethernet interface (e.g. eth0) and start one listening on the Open vSwitch bridge (e.g. breth0).

Depending on your VM, you can make the above step persistent across reboots. For example, if your VM is Debian/Ubuntu-based, read openvswitch-switch.README.Debian found in debian folder. If your VM is RHEL-based, refer to Fedora, RHEL 7.x+ Packaging for OVN.
Start the Open vSwitch network driver

The Open vSwitch driver uses the Python’s flask module to listen to Docker’s networking api calls. The driver also uses OpenStack’s python-neutronclient libraries. If your host does not have Python’s flask module or python-neutronclient you must install them. For example:
```
$ pip install python-neutronclient
$ pip install Flask
```
Once installed, source the openrc file:
```
$ . ./openrc.sh
```
Start the network driver and provide your OpenStack tenant password when prompted:
```
$ PYTHONPATH=$OVS_PYTHON_LIBS_PATH ovn-docker-underlay-driver \
    --bridge breth0 --detach
```

From here-on you can use the same Docker commands as described in docker-overlay.

Refer to the ovs-architecture man pages (man ovn-architecture) to understand OVN’s architecture in detail.