ovs-test(1) Open vSwitch Manual ovs-test(1)
ovs-test - check Linux drivers for performance, vlan and L3 tunneling
ovs-test -s port
ovs-test -c server1 server2 [-b targetbandwidth] [-i testinterval] [-d]
[-l vlantag] [-t tunnelmodes]
[-h | --help] [-V | --version]
The ovs-test program may be used to check for problems sending 802.1Q
or GRE traffic that Open vSwitch may uncover. These problems, for exam‐
ple, can occur when Open vSwitch is used to send 802.1Q traffic through
physical interfaces running certain drivers of certain Linux kernel
versions. To run a test, configure IP addresses on server1 and server2
for interfaces you intended to test. These interfaces could also be
already configured OVS bridges that have a physical interface attached
to them. Then, on one of the nodes, run ovs-test in server mode and on
the other node run it in client mode. The client will connect to
ovs-test server and schedule tests between both of them. The ovs-test
client will perform UDP and TCP tests.
UDP tests can report packet loss and achieved bandwidth for various
datagram sizes. By default target bandwidth for UDP tests is 1Mbit/s.
TCP tests report only achieved bandwidth, because kernel TCP stack
takes care of flow control and packet loss. TCP tests are essential to
detect potential TSO related issues.
To determine whether Open vSwitch is encountering any problems, the
user must compare packet loss and achieved bandwidth in a setup where
traffic is being directly sent and in one where it is not. If in the
802.1Q or L3 tunneled tests both ovs-test processes are unable to com‐
municate or the achieved bandwidth is much lower compared to direct
setup, then, most likely, Open vSwitch has encountered a pre-existing
kernel or driver bug.
Some examples of the types of problems that may be encountered are:
· When NICs use VLAN stripping on receive they must pass a pointer
to a vlan_group when reporting the stripped tag to the network‐
ing core. If no vlan_group is in use then some drivers just
drop the extracted tag. Drivers are supposed to only enable
stripping if a vlan_group is registered but not all of them do
· On receive, some drivers handle priority tagged packets spe‐
cially and don't pass the tag onto the network stack at all, so
Open vSwitch never has a chance to see it.
· Some drivers size their receive buffers based on whether a
vlan_group is enabled, meaning that a maximum size packet with a
VLAN tag will not fit if no vlan_group is configured.
· On transmit, some drivers expect that VLAN acceleration will be
used if it is available, which can only be done if a vlan_group
is configured. In these cases, the driver may fail to parse the
packet and correctly setup checksum offloading or TSO.
An ovs-test client will connect to two ovs-test servers and will ask
them to exchange test traffic. It is also possible to spawn an ovs-test
server automatically from the client.
To conduct tests, two ovs-test servers must be running on two different
hosts where the client can connect. The actual test traffic is
exchanged only between both ovs-test servers. It is recommended that
both servers have their IP addresses in the same subnet, otherwise one
would have to make sure that routing is set up correctly.
Run in server mode and wait for the client to establish XML RPC
Control Connection on this TCP port. It is recommended to have
ethtool(8) installed on the server so that it could retrieve
information about the NIC driver.
-c server1 server2
--client server1 server2
Run in client mode and schedule tests between server1 and
server2, where each server must be given in the following format
- OuterIP[:OuterPort],InnerIP[/Mask][:InnerPort]. The OuterIP
must be already assigned to the physical interface which is
going to be tested. This is the IP address where client will
try to establish XML RPC connection. If OuterIP is 127.0.0.1
then client will automatically spawn a local instance of
ovs-test server. OuterPort is TCP port where server is listening
for incoming XML/RPC control connections to schedule tests (by
default it is 15531). The ovs-test will automatically assign
InnerIP[/Mask] to the interfaces that will be created on the fly
for testing purposes. It is important that InnerIP[/Mask] does
not interfere with already existing IP addresses on both
ovs-test servers and client. InnerPort is port which will be
used by server to listen for test traffic that will be encapsu‐
lated (by default it is 15532).
Target bandwidth for UDP tests. The targetbandwidth must be
given in bits per second. It is possible to use postfix M or K
to alter the target bandwidth magnitude.
How long each test should run. By default 5 seconds.
--help Prints a brief help message to the console.
Prints version information to the console.
The following test modes are supported by ovs-test. It is possible to
combine multiple of them in a single ovs-test invocation.
Perform direct tests between both OuterIP addresses. These tests
could be used as a reference to compare 802.1Q or L3 tunneling
Perform 802.1Q tests between both servers. These tests will cre‐
ate a temporary OVS bridge, if necessary, and attach a VLAN
tagged port to it for testing purposes.
Perform L3 tunneling tests. The given argument is a comma sepa‐
rated string that specifies all the L3 tunnel modes that should
be tested (e.g. gre). The L3 tunnels are terminated on interface
that has the OuterIP address assigned.
On host 220.127.116.11 start ovs-test in server mode:
ovs-test -s 15531
On host 18.104.22.168 start ovs-test in client mode and do direct, VLAN and
GRE tests between both nodes:
ovs-test -c 127.0.0.1,22.214.171.124/30 126.96.36.199,188.8.131.52/30 -d -l 123 -t
ovs-vswitchd(8), ovs-ofctl(8), ovs-vsctl(8), ovs-vlan-test(8), eth‐
Open vSwitch 2.5.90 ovs-test(1)