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README.Debian for openvswitch-switch
---------------------------------
To use the Linux kernel-based switch implementation, you will need an
Open vSwitch kernel module. There are multiple ways to obtain one.
In order of increasing manual effort, these are:
* Use a Linux kernel 3.3 or later, which has an integrated Open
vSwitch kernel module.
The upstream Linux kernel module lacks a few features that
are in the third-party module. For details, please see the
FAQ, "What features are not available in the Open vSwitch
kernel datapath that ships as part of the upstream Linux
kernel?".
* Install the "openvswitch-datapath-dkms" Debian package that
you built earlier. This should automatically build and
install the Open vSwitch kernel module for your running
kernel.
This option requires that you have a compiler and toolchain
installed on the machine where you run Open vSwitch, which
may be unacceptable in some production server environments.
* Install the "openvswitch-datapath-source" Debian package, use
"module-assistant" to build a Debian package of the Open
vSwitch kernel module for your kernel, and then install that
Debian package.
You can install the kernel module Debian packages that you
build this way on the same machine where you built it or on
another machine or machines, which means that you don't
necessarily have to have any build infrastructure on the
machines where you use the kernel module.
/usr/share/doc/openvswitch-datapath-source/README.Debian has
details on the build process.
* Build and install the kernel module by hand.
Debian network scripts integration
----------------------------------
This package lets a user to optionally configure Open vSwitch bridges
and ports from /etc/network/interfaces. Please refer to the interfaces(5)
manpage for more details regarding /etc/network/interfaces.
The stanzas that configure the OVS bridges should begin with "allow-ovs"
followed by name of the bridge. Here is an example.
allow-ovs br0
The stanzas that configure the OVS ports should begin with
"allow-${bridge-name}" followed by name of the port. Here is an example.
allow-br0 eth0
The following OVS specific "command" options are supported:
- ovs_type: This can either be OVSBridge, OVSPort, OVSIntPort, OVSBond,
OVSPatchPort or OVSTunnel depending on whether you configure a bridge,
port, an internal port, a bond, a patch port or a tunnel. This is a
required option.
- ovs_ports: This option specifies all the ports that belong to a bridge.
- ovs_bridge: This options specifies a bridge to which a port belongs.
This is a required option for a port.
- ovs_bonds: This option specifies the list of physical interfaces to be
bonded together.
- ovs_patch_peer: For "OVSPatchPort" interfaces, this field specifies
the patch's peer on the other bridge.
- ovs_tunnel_type: For "OVSTunnel" interfaces, the type of the tunnel.
For example, "gre", "vxlan", etc.
- ovs_tunnel_options: For "OVSTunnel" interfaces, this field should be
used to specify the tunnel options like remote_ip, key, etc.
- ovs_options: This option lets you add extra arguments to a ovs-vsctl
command. See examples.
- ovs_extra: This option lets you run additional ovs-vsctl commands,
separated by "--" (double dash). Variables can be part of the "ovs_extra"
option. You can provide all the standard environmental variables
described in the interfaces(5) man page. You can also pass shell
commands.
More implementation specific details can be seen in the examples.
Examples:
--------
ex 1: A standalone bridge.
allow-ovs br0
iface br0 inet static
address 192.168.1.1
netmask 255.255.255.0
ovs_type OVSBridge
ex 2: A bridge with one port.
allow-ovs br0
iface br0 inet dhcp
ovs_type OVSBridge
ovs_ports eth0
allow-br0 eth0
iface eth0 inet manual
ovs_bridge br0
ovs_type OVSPort
ex 3: A bridge with multiple physical ports.
allow-ovs br0
iface br0 inet dhcp
ovs_type OVSBridge
ovs_ports eth0 eth1
allow-br0 eth0
iface eth0 inet manual
ovs_bridge br0
ovs_type OVSPort
allow-br0 eth1
iface eth1 inet manual
ovs_bridge br0
ovs_type OVSPort
ex 4: A bridge with an OVS internal port.
allow-ovs br1
iface br1 inet static
address 192.168.1.1
netmask 255.255.255.0
ovs_type OVSBridge
ovs_ports vlan100
allow-br1 vlan100
iface vlan100 inet manual
ovs_bridge br1
ovs_type OVSIntPort
ovs_options tag=100
ovs_extra set interface ${IFACE} external-ids:iface-id=$(hostname -s)
ex 5: Bonding.
allow-ovs br2
iface br2 inet static
address 192.170.1.1
netmask 255.255.255.0
ovs_type OVSBridge
ovs_ports bond0
allow-br2 bond0
iface bond0 inet manual
ovs_bridge br2
ovs_type OVSBond
ovs_bonds eth2 eth3
ovs_options bond_mode=balance-tcp lacp=active
ex 6: Patch ports.
allow-ovs br0
iface br0 inet manual
ovs_type OVSBridge
ovs_ports patch0
allow-br0 patch0
iface patch0 inet manual
ovs_bridge br0
ovs_type OVSPatchPort
ovs_patch_peer patch1
allow-ovs br1
iface br1 inet manual
ovs_type OVSBridge
ovs_ports patch1
allow-br1 patch1
iface patch1 inet manual
ovs_bridge br1
ovs_type OVSPatchPort
ovs_patch_peer patch0
ex 7: Tunnel.
allow-ovs br1
iface br1 inet static
address 192.168.1.1
netmask 255.255.255.0
ovs_type OVSBridge
ovs_ports gre1
allow-br1 gre1
iface gre1 inet manual
ovs_bridge br1
ovs_type OVSTunnel
ovs_tunnel_type gre
ovs_tunnel_options options:remote_ip=182.168.1.2 options:key=1
ex 8: Create and destroy bridges.
ifup --allow=ovs $list_of_bridges
ifdown --allow=ovs $list_of_bridges
Notes on dependencies:
---------------------
openvswitch-switch depends on $network, $named $remote_fs and $syslog to start.
This creates some startup dependency issues.
* Since openvswitch utilities are placed in /usr and /usr can be mounted
through NFS, openvswitch has to start after it. But if a user uses openvswitch
for all his networking needs and hence to mount NFS, there will be a deadlock.
So, if /usr is mounted through NFS and openvswitch is used for all networking,
the administrator should figure out a way to mount NFS before starting OVS.
One way to do this is in initramfs.
* Since openvswitch starts after $network, $remote_fs and $syslog, any startup
script that depends on openvswitch but starts before it, needs to be changed
to depend on openvswitch-switch too.
* Ideally, an admin should not add openvswitch bridges in the 'auto'
section of the 'interfaces' file (i.e., if "br0" is a OVS bridge, you should
not have a line "auto br0"). This is because, when ifupdown starts
working on bridges listed in 'auto', openvswitch has not yet started.
But, if the admin wants to go down this route and adds openvswitch bridges
in the 'auto' section, openvswitch-switch will forcefully be started when
ifupdown kicks in. In a case like this, the admin needs to make sure that /usr
has already been mounted and that a remote $syslog (if used) is ready to
receive openvswitch logs.
* With systemd, adding openvswitch bridges in the 'auto' section of the
'interfaces' file can cause race conditions (i.e., if "br0" is a OVS bridge,
you should not have a line "auto br0"). Debian systems have added a
systemd ifup@.service file. This file will call ifdown and ifup on interfaces
in "auto" section automatically when the interfaces disappear and appear
respectively. This will cause race conditions if you delete and add the same
bridges using tools like "ovs-vsctl" or "ovs-dpctl". This is also a problem
when you upgrade your openvswitch kernel module using commands like
'force-reload-kmod'.