wiki:Documentation/fSDN/aSwitchImage

OpenVSwitch

This page describes how to install and use OpenVSwitch (OVS). OVS is a software switch implementation designed to run on Linux. More information about Open vSwitch can be found at their website.

Contents

I. Installation

1.1 from source
1.2 from binaries

II. Running OVS

2.1 initialization
2.2 Configuring OVS
2.3 OVS with KVM
2.4 OVS with OpenFlow

III. References


I Installation

OVS can be installed either from source or from binaries. Section 1.1 covers how to build from source, and section 1.2 covers install from binaries.

Prerequisites

OVS should install/work with relatively little effort on Ubuntu (or perhaps other Linuxes as well). The following installation/operation steps were successfully done on Ubuntu 10.10 through 12.04.

1.1 Method 1: from source

The steps followed in this section 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.

1.1.1 Getting the 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 dependencies:
    apt-get install pkg-config autoconf automake linux-libc-dev libtool
    
  3. Fetch the 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
    

1.1.2 Some Sanity Checks.

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

  • 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.
  • 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.
  • /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.

  • Modules may not be loaded properly; look for the OVS module with lsmod:
    root@node1-1:~/openvswitch-1.1.1# lsmod | grep open
    openvswitch_mod        68183  1 
    
  • In general, dmesg can be used to check for various anomalies when things e.g. insmod fail silently.

1.2 Method 2: from binaries

Binaries are easier to set up, but lag in OVS version and support a narrower range of architectures and kernel versions.

  1. Install the openvswitch packages. Do not use the Ubuntu repositories since the install the incorrect versions of the package; Download the packages that match your kernel version from here
    For an x86_64 system, the following are needed (The package openvswitch-brcompat_1.2.2.10448_amd64.deb should be added if bridge compatibility is needed):
    openvswitch-datapath-module-2.6.38-8-server_1.2.2.10448_amd64.deb
    openvswitch-common_1.2.2.10448_amd64.deb
    openvswitch-switch_1.2.2.10448_amd64.deb
    
    Install them in that order with "dpkg -i". It will recommend a restart.
  2. The module should be loaded automatically upon installation and system reboot. You should be able to query the module:
    root@external3:~# ovs-vsctl show
    d03e1847-34f4-4129-8821-63fff3403553
    ovs_version: "1.2.2.10448"
    
    lsmod should also show the running openvswitch_mod.

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

For an OVS switch to behave as a plain vanilla switch, both bridge interface and associated network interfaces must be up and configured with IP layer information. The bridge interface can be configured with tools such as ifconfig (or even DHCP) like any other *nic interface. Its configurations may even be stored in /etc/network/interfaces for persistence:

#static bridge interface configs
auto br0
iface br0 inet static
        address 192.168.1.10
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.1.255
        gateway 192.168.1.1
#bridges can use dynamic configuration as well
auto br1
iface br1 inet dhcp

2.3 OVS with KVM

OVS can be used with KVM. The instructions for setting this up can be found here, or in the root directory of the source as INSTALL.KVM. A use case is documented in this separate wiki entry.

2.4 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.

  1. 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.


III References

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

Last modified 2 years ago Last modified on 05/11/15 12:07:44

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