Installation and Usage of Open vSwitch

This page describes how to install and use OpenVSwitch (OVS). OVS is a software switch implementation designed to run on Linux. More information about the software can be found ​here.

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I Installation

OVS can be installed either from source or from binaries.

For installation from source, the steps followed here are based on the contents of INSTALL.Linux, included with the OVS tarball and also found ​here(also attached at the end of this page for your convenience). It should be found under the OVS root directory.

1.1 Prerequisites

The node used here is a NetFPGA cube, the standard node for !SandBox9. The node was imaged with ubuntu.ndz, based on Ubuntu 10.10 (Maverick). The steps have been tested successfully with up to Ubuntu 12.04.

1.2 Method 1: from source

1.2.1 Fetch source and dependencies

1. If your Ubuntu install is still fresh, run 'apt-get update'. If this fails, repeat after replacing all instances of 'apt:9999' with 'us.archive.ubuntu.com' in /etc/apt/sources.list .

2. Install packages for Open Vswitch:

   apt-get install pkg-config autoconf automake linux-libc-dev libtool
   

3. Fetch OVS tarball and untar. the latest source can be found at ​http://openvswitch.org/download/ .

   cd ~/
   wget http://openvswitch.org/releases/openvswitch-1.6.1.tar.gz
   tar -xf openvswitch-1.1.1.tar.gz
   

4. Build. On Debian (and its variants), Open vSwitch must be built as a kernel module. If everything is sound, installing OVS should be little more than following the steps in INSTALL.Linux.

   cd ~/openvswitch-1.1.1
   ./boot.sh
   ./configure --with-l26=/lib/modules/`uname -r`/build
   make
   make install
   

5. instantiate the kernel module:

   insmod datapath/linux-2.6/openvswitch_mod.ko
   

1.2.2 Some Sanity Checks.

If things don't go well, here are some things worth checking:

1. Check /usr/src/linux-headers-`uname -r`/.config for the following kernel configs:

• CONFIG_BRIDGE as module (=m)
• NET_CLS_ACT, NET_CLS_U32, NET_SCH_INGRESS as modules or built-in (=m or =y, respectively) if policing
• CONFIG_TUN if you need tunneling

Fix them as necessary.

2. The bridge module should not be loaded (e.g. should not show up when you do lsmod | grep bridge); remove it if it is loaded. If it seems to be loaded at boot time, there may be an entry for it somewhere in /etc/modules.

3. /lib/modules/$(uname -r)/build should be a link to the Linux kernel header directory:

   root@node1-1:~# ls -ald /lib/modules/$(uname -r)/build
   lrwxrwxrwx 1 root root 40 2011-07-26 13:41 /lib/modules/2.6.35-30-generic/build -> /usr/src/linux-headers-2.6.35-30-generic
   

This directory should contain (mostly) unbroken links. If not, repeat step 3 of the prerequisites with another kernel version, e.g. by upgrading the kernel as follows:

apt-get install linux-headers-2.6.35-30-generic linux-image-2.6.35-30-generic
reboot
apt-get install linux-source-2.6.35

When linux-image is installed, grub is updated so that the newest kernel is loaded automatically upon next reboot. Re-installing linux-source after reboot should install the proper version for the new kernel.

4. Modules may not get loaded properly; look for Open vSwitch modules with lsmod:

   root@node1-1:~/openvswitch-1.1.1# lsmod | grep open
   openvswitch_mod        68183  1 
   

5. In general, dmesg can be used to check for various anomalies when things e.g. insmod fail silently.

1.3 Method 2: from binaries

1.4 Section I References

The following links were referenced but aren't relevant overall; this is just for citation.

• ​http://www.cyberciti.biz/tips/build-linux-kernel-module-against-installed-kernel-source-tree.html
• ​http://forums.gentoo.org/viewtopic-t-118180-highlight-bridgeutils.html?sid=4d602c9e364130609caff99aa2a40c69
• ​https://help.ubuntu.com/community/Kernel/Compile
• ​http://ubuntuguide.net/ubuntu-11-04-upgrade-linux-kernel-to-2-6-39-0

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II Running OVS.

OVS has three main components that must be initialized:

• openvswitch_mod.ko, the OVS kernel module
• ovsdb, the database containing configurations
• ovs-vswitchd, the OVS switch daemon

The daemon configures itself using the data provided by the database; ovs-vsctl is used to modify the contents of the database in order to configure the OVS switch at runtime.

2.1 Initialization

1. Load openVswitch kernel module

    cd datapath/linux/
    insmod openvswitch_mod.ko
   

Note, OVS and Linux bridging may not be used at the same time. This step will fail if the bridge module (bridge.ko) is loaded. You may need to reboot the node in order to unload bridge.ko.
If this is the first time OVS is being run, make am openvswitch directory in /usr/local/etc/ and run ovsdb-tool to create the database file:

 mkdir -p /usr/local/etc/openvswitch
 ovsdb-tool create /usr/local/etc/openvswitch/conf.db vswitchd/vswitch.ovsschema

2. Start ovs-db:

    ovsdb/ovsdb-server --remote=punix:/usr/local/var/run/openvswitch/db.sock \
           --remote=db:Open_vSwitch,manager_options \
           --pidfile --detach
   

3. Initialize the database:

    utilities/ovs-vsctl --no-wait init
   

the --no-wait allows the database to be initialized before ovs-vswitchd is invoked.

4. Start ovs-vswitchd:

    vswitchd/ovs-vswitchd unix:/usr/local/var/run/openvswitch/db.sock --pidfile --detach
   

The 'unix:…db.sock' specifies that the process attach to the socket opened by ovsdb.

2.2 Configuring OVS

Once OVS is running, virtual switches may be created and configured. In general, a virtual switch is comprised of a bridge interface (usually named brx), and one or more interfaces associated with it. A single vswitchd can control multiple virtual switches with arbitrary number of ports each.

2.2.1 Creating virtual switches

The following steps create a bridge interface (br0) and associate an interface to it:

 ovs-vsctl add-br br0
 ovs-vsctl add-port br0 eth0

The same steps can be used to add VLAN interfaces:

 ovs-vsctl add-port br0 eth0.222

In this case, the ports added to the bridge interface are trunked by default. Using the option tag=VLAN ID makes the interfaces behave as access ports for the VLAN ID specified:

 ovs-vsctl add-port br0 eth0.111 tag=111
 ovs-vsctl add-port br0 eth0.222 tag=222

2.2.2 Network configuration

The bridge interface can be configured like any other *nic interface. Its configurations may be stored in /etc/network/interfaces for persistence.

2.3 OVS with OpenFlow

OVS switches may be run as OpenFlow switches. The following steps describe how to run OVS in OpenFlow mode.

1. If it has not been done already, fire up an OpenFlow controller. The procedures for this step differ according to the controller in use, and are discussed in the pages for each respective controller.
   

A sanity check for this step is to test your virtual switch with the OVS built-in controller, ovs-controller, which may be initialized on the same node running OVS:

ovs-controller -v ptcp:6633

When ovs-controller is used, the controller IP is, unsurprisingly, 127.0.0.1.

2. Point ovs-vswitchd to the OpenFlow controller.

   ovs-vsctl set-controller br0 tcp:172.16.0.14:6633
   

In this example, the OVS process is pointed to a BSN controller (kvm-big) on 172.16.0.14, listening on port 6633. With a properly initialized and configured database, ovs-vswitchd will spit out a bunch of messages as it attempts to connect to the controller. Its output should look something similar to this:

root@node1-4:/opt/openvswitch-1.2.2# vswitchd/ovs-vswitchd unix:/usr/local/var/run/openvswitch/db.sock --pidfile --detach
Nov 07 17:37:02|00001|reconnect|INFO|unix:/usr/local/var/run/openvswitch/db.sock: connecting...
Nov 07 17:37:02|00002|reconnect|INFO|unix:/usr/local/var/run/openvswitch/db.sock: connected
Nov 07 17:37:02|00003|bridge|INFO|created port br0 on bridge br0
Nov 07 17:37:02|00004|bridge|INFO|created port eth0.101 on bridge br0
Nov 07 17:37:02|00005|bridge|INFO|created port eth0.102 on bridge br0
Nov 07 17:37:02|00006|ofproto|INFO|using datapath ID 0000002320b91d13
Nov 07 17:37:02|00007|ofproto|INFO|datapath ID changed to 000002972599b1ca
Nov 07 17:37:02|00008|rconn|INFO|br0<->tcp:172.16.0.14:6633: connecting...

The OpenvSwitch OpenFlow switch should be functional as soon as it finds and connects to the controller. As you can see above, a DPID is chosen at random; if a random DPID does not suit your needs, a DPID may be specified manually using ovs-vsctl:

ovs-vsctl set bridge <mybr> other-config:datapath-id=<datapathid>

Where <datapathid> is a 16-digit hex value. For our network node, this becomes:

ovs-vsctl set bridge br0 other-config:datapath-id=0000009900113300

Once running, all typical things applicable to an OpenFlow switch applies to the running OVS switch.