OVS-TEST(8) Open vSwitch OVS-TEST(8)
NAME
ovs-test - Check Linux drivers for performance, vlan and L3 tunneling
problems
SYNOPSIS
ovs-test -s port
ovs-test -c server1 server2 [-b targetbandwidth] [-i testinterval] [-d]
[-l vlantag] [-t tunnelmodes]
DESCRIPTION
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 al‐
ready 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 networking 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 that.
• On receive, some drivers handle priority tagged packets specially 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 config‐
ured. In these cases, the driver may fail to parse the packet and
correctly setup checksum offloading or TSO.
Client Mode
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.
Server Mode
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.
OPTIONS
-s <port>, --server <port>
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 in‐
formation 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 for‐
mat:
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 lis‐
tening 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 In‐
nerIP[/Mask] does not interfere with already existing IP ad‐
dresses on both ovs-test servers and client. InnerPort is port
which will be used by server to listen for test traffic that
will be encapsulated (by default it is 15532).
-b <targetbandwidth>, --bandwidth <targetbandwidth>
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.
-i <testinterval>, --interval <testinterval>
How long each test should run. By default 5 seconds.
-h, --help
Prints a brief help message to the console.
-V, --version
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.
-d, --direct
Perform direct tests between both OuterIP addresses. These tests
could be used as a reference to compare 802.1Q or L3 tunneling
test results.
-l <vlantag>, --vlan-tag <vlantag>
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.
-t <tunnelmodes>, --tunnel-modes <tunnelmodes>
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 inter‐
face that has the OuterIP address assigned.
EXAMPLES
On host 1.2.3.4 start ovs-test in server mode:
ovs-test -s 15531
On host 1.2.3.5 start ovs-test in client mode and do direct, VLAN and
GRE tests between both nodes:
ovs-test -c 127.0.0.1,1.1.1.1/30 1.2.3.4,1.1.1.2/30 -d -l 123 -t
gre
SEE ALSO
ovs-vswitchd(8), ovs-ofctl(8), ovs-vsctl(8), ovs-vlan-test, ethtool(8),
uname(1)
AUTHOR
The Open vSwitch Development Community
COPYRIGHT
2016-2024, The Open vSwitch Development Community
3.4 Nov 16, 2024 OVS-TEST(8)