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Using Open vSwitch without kernel support
=========================================
Open vSwitch can operate, at a cost in performance, entirely in
userspace, without assistance from a kernel module. This file
explains how to install Open vSwitch in such a mode.
The userspace-only mode of Open vSwitch is considered experimental.
It has not been thoroughly tested.
This version of Open vSwitch should be built manually with "configure"
and "make". Debian packaging for Open vSwitch is also included, but
it has not been recently tested, and so Debian packages are not a
recommended way to use this version of Open vSwitch.
Building and Installing
-----------------------
The requirements and procedure for building, installing, and
configuring Open vSwitch are the same as those given in INSTALL.
You may omit configuring, building, and installing the kernel module,
and the related requirements.
On Linux, the userspace switch additionally requires the kernel
TUN/TAP driver to be available, either built into the kernel or loaded
as a module. If you are not sure, check for a directory named
/sys/class/misc/tun. If it does not exist, then attempt to load the
module with "modprobe tun".
The tun device must also exist as /dev/net/tun. If it does not exist,
then create /dev/net (if necessary) with "mkdir /dev/net", then create
/dev/net/tun with "mknod /dev/net/tun c 10 200".
On FreeBSD and NetBSD, the userspace switch additionally requires the
kernel tap(4) driver to be available, either built into the kernel or
loaded as a module.
Using the Userspace Datapath with ovs-vswitchd
----------------------------------------------
To use ovs-vswitchd in userspace mode, create a bridge with datapath_type
"netdev" in the configuration database. For example:
ovs-vsctl add-br br0
ovs-vsctl set bridge br0 datapath_type=netdev
ovs-vsctl add-port br0 eth0
ovs-vsctl add-port br0 eth1
ovs-vsctl add-port br0 eth2
ovs-vswitchd will create a TAP device as the bridge's local interface,
named the same as the bridge, as well as for each configured internal
interface.
Currently, on FreeBSD, the functionality required for in-band control
support is not implemented. To avoid related errors, you can disable
the in-band support with the following command.
ovs-vsctl set bridge br0 other_config:disable-in-band=true
Firewall Rules
--------------
On Linux, when a physical interface is in use by the userspace
datapath, packets received on the interface still also pass into the
kernel TCP/IP stack. This can cause surprising and incorrect
behavior. You can use "iptables" to avoid this behavior, by using it
to drop received packets. For example, to drop packets received on
eth0:
iptables -A INPUT -i eth0 -j DROP
iptables -A FORWARD -i eth0 -j DROP
Other settings
--------------
On NetBSD, depending on your network topology and applications, the
following configuration might help. See sysctl(7).
sysctl net.inet.ip.checkinterface=1
Bug Reporting
-------------
Please report problems to bugs@openvswitch.org.
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