ovs-vswitchd(8) Open vSwitch Manual ovs-vswitchd(8)

NAME
ovs-vswitchd - Open vSwitch daemon

SYNOPSIS
ovs-vswitchd [database]

DESCRIPTION
A daemon that manages and controls any number of Open vSwitch switches
on the local machine.

The database argument specifies how ovs-vswitchd connects to
ovsdb-server. database may be an OVSDB active or passive connection
method, as described in ovsdb(7). The default is unix:/usr/lo‐
cal/var/run/openvswitch/db.sock.

ovs-vswitchd retrieves its configuration from database at startup. It
sets up Open vSwitch datapaths and then operates switching across each
bridge described in its configuration files. As the database changes,
ovs-vswitchd automatically updates its configuration to match.

ovs-vswitchd switches may be configured with any of the following fea‐
tures:

• L2 switching with MAC learning.

• NIC bonding with automatic fail-over and source MAC-based TX
load balancing ("SLB").

• 802.1Q VLAN support.

• Port mirroring, with optional VLAN tagging.

• NetFlow v5 flow logging.

• sFlow(R) monitoring.

• Connectivity to an external OpenFlow controller, such as NOX.

Only a single instance of ovs-vswitchd is intended to run at a time. A
single ovs-vswitchd can manage any number of switch instances, up to
the maximum number of supported Open vSwitch datapaths.

ovs-vswitchd does all the necessary management of Open vSwitch data‐
paths itself. Thus, ovs-dpctl(8) (and its userspace datapath counter‐
parts accessible via ovs-appctl dpctl/command) are not needed with
ovs-vswitchd and should not be used because they can interfere with its
operation. These tools are still useful for diagnostics.

An Open vSwitch datapath kernel module must be loaded for ovs-vswitchd
to be useful. Refer to the documentation for instructions on how to
build and load the Open vSwitch kernel module.

OPTIONS
--mlockall
Causes ovs-vswitchd to call the mlockall() function, to attempt
to lock all of its process memory into physical RAM, preventing
the kernel from paging any of its memory to disk. This helps to
avoid networking interruptions due to system memory pressure.

Some systems do not support mlockall() at all, and other systems
only allow privileged users, such as the superuser, to use it.
ovs-vswitchd emits a log message if mlockall() is unavailable or
unsuccessful.

DPDK Options
For details on initializing ovs-vswitchd to use DPDK ports, refer to
the documentation or ovs-vswitchd.conf.db(5).

DPDK HW Access Options
--hw-rawio-access
Tells ovs-vswitchd to retain the CAP_SYS_RAWIO capability, to
allow userspace drivers access to raw hardware memory. This
will also allow the ovs-vswitchd daemon to call iopl() and iop‐
erm() functions as well as access memory devices to set port ac‐
cess. This is a very powerful capability, so generally only en‐
able as needed for specific hardware (for example mlx5 with full
hardware offload via rte_flow).

Daemon Options
The following options are valid on POSIX based platforms.

--pidfile[=pidfile]
Causes a file (by default, ovs-vswitchd.pid) to be created indi‐
cating the PID of the running process. If the pidfile argument
is not specified, or if it does not begin with /, then it is
created in /usr/local/var/run/openvswitch.

If --pidfile is not specified, no pidfile is created.

--overwrite-pidfile
By default, when --pidfile is specified and the specified pid‐
file already exists and is locked by a running process,
ovs-vswitchd refuses to start. Specify --overwrite-pidfile to
cause it to instead overwrite the pidfile.

When --pidfile is not specified, this option has no effect.

--detach
Runs ovs-vswitchd as a background process. The process forks,
and in the child it starts a new session, closes the standard
file descriptors (which has the side effect of disabling logging
to the console), and changes its current directory to the root
(unless --no-chdir is specified). After the child completes its
initialization, the parent exits. ovs-vswitchd detaches only
after it has connected to the database, retrieved the initial
configuration, and set up that configuration.

--monitor
Creates an additional process to monitor the ovs-vswitchd dae‐
mon. If the daemon dies due to a signal that indicates a pro‐
gramming error (SIGABRT, SIGALRM, SIGBUS, SIGFPE, SIGILL, SIG‐
PIPE, SIGSEGV, SIGXCPU, or SIGXFSZ) then the monitor process
starts a new copy of it. If the daemon dies or exits for an‐
other reason, the monitor process exits.

This option is normally used with --detach, but it also func‐
tions without it.

--no-chdir
By default, when --detach is specified, ovs-vswitchd changes its
current working directory to the root directory after it de‐
taches. Otherwise, invoking ovs-vswitchd from a carelessly cho‐
sen directory would prevent the administrator from unmounting
the file system that holds that directory.

Specifying --no-chdir suppresses this behavior, preventing
ovs-vswitchd from changing its current working directory. This
may be useful for collecting core files, since it is common be‐
havior to write core dumps into the current working directory
and the root directory is not a good directory to use.

This option has no effect when --detach is not specified.

--no-self-confinement
By default daemon will try to self-confine itself to work with
files under well-known directories determined during build. It
is better to stick with this default behavior and not to use
this flag unless some other Access Control is used to confine
daemon. Note that in contrast to other access control implemen‐
tations that are typically enforced from kernel-space (e.g. DAC
or MAC), self-confinement is imposed from the user-space daemon
itself and hence should not be considered as a full confinement
strategy, but instead should be viewed as an additional layer of
security.

--user Causes ovs-vswitchd to run as a different user specified in
"user:group", thus dropping most of the root privileges. Short
forms "user" and ":group" are also allowed, with current user or
group are assumed respectively. Only daemons started by the root
user accepts this argument.

On Linux, daemons will be granted CAP_IPC_LOCK and
CAP_NET_BIND_SERVICES before dropping root privileges. Daemons
that interact with a datapath, such as ovs-vswitchd, will be
granted three additional capabilities, namely CAP_NET_ADMIN,
CAP_NET_BROADCAST and CAP_NET_RAW. The capability change will
apply even if the new user is root.

On Windows, this option is not currently supported. For security
reasons, specifying this option will cause the daemon process
not to start.

Service Options
The following options are valid only on Windows platform.

--service
Causes ovs-vswitchd to run as a service in the background. The
service should already have been created through external tools
like SC.exe.

--service-monitor
Causes the ovs-vswitchd service to be automatically restarted by
the Windows services manager if the service dies or exits for
unexpected reasons.

When --service is not specified, this option has no effect.

Public Key Infrastructure Options
-p privkey.pem
--private-key=privkey.pem
Specifies a PEM file containing the private key used as
ovs-vswitchd's identity for outgoing SSL connections.

-c cert.pem
--certificate=cert.pem
Specifies a PEM file containing a certificate that certifies the
private key specified on -p or --private-key to be trustworthy.
The certificate must be signed by the certificate authority (CA)
that the peer in SSL connections will use to verify it.

-C cacert.pem
--ca-cert=cacert.pem
Specifies a PEM file containing the CA certificate that
ovs-vswitchd should use to verify certificates presented to it
by SSL peers. (This may be the same certificate that SSL peers
use to verify the certificate specified on -c or --certificate,
or it may be a different one, depending on the PKI design in
use.)

-C none
--ca-cert=none
Disables verification of certificates presented by SSL peers.
This introduces a security risk, because it means that certifi‐
cates cannot be verified to be those of known trusted hosts.

--bootstrap-ca-cert=cacert.pem
When cacert.pem exists, this option has the same effect as -C or
--ca-cert. If it does not exist, then ovs-vswitchd will attempt
to obtain the CA certificate from the SSL peer on its first SSL
connection and save it to the named PEM file. If it is success‐
ful, it will immediately drop the connection and reconnect, and
from then on all SSL connections must be authenticated by a cer‐
tificate signed by the CA certificate thus obtained.

This option exposes the SSL connection to a man-in-the-middle
attack obtaining the initial CA certificate, but it may be use‐
ful for bootstrapping.

This option is only useful if the SSL peer sends its CA certifi‐
cate as part of the SSL certificate chain. The SSL protocol
does not require the server to send the CA certificate.

This option is mutually exclusive with -C and --ca-cert.

--peer-ca-cert=peer-cacert.pem
Specifies a PEM file that contains one or more additional cer‐
tificates to send to SSL peers. peer-cacert.pem should be the
CA certificate used to sign ovs-vswitchd's own certificate, that
is, the certificate specified on -c or --certificate. If
ovs-vswitchd's certificate is self-signed, then --certificate
and --peer-ca-cert should specify the same file.

This option is not useful in normal operation, because the SSL
peer must already have the CA certificate for the peer to have
any confidence in ovs-vswitchd's identity. However, this offers
a way for a new installation to bootstrap the CA certificate on
its first SSL connection.

Logging Options
-v[spec]
--verbose=[spec]
Sets logging levels. Without any spec, sets the log level for
every module and destination to dbg. Otherwise, spec is a list
of words separated by spaces or commas or colons, up to one from
each category below:

• A valid module name, as displayed by the vlog/list com‐
mand on ovs-appctl(8), limits the log level change to the
specified module.

• syslog, console, or file, to limit the log level change
to only to the system log, to the console, or to a file,
respectively. (If --detach is specified, ovs-vswitchd
closes its standard file descriptors, so logging to the
console will have no effect.)

On Windows platform, syslog is accepted as a word and is
only useful along with the --syslog-target option (the
word has no effect otherwise).

• off, emer, err, warn, info, or dbg, to control the log
level. Messages of the given severity or higher will be
logged, and messages of lower severity will be filtered
out. off filters out all messages. See ovs-appctl(8)
for a definition of each log level.

Case is not significant within spec.

Regardless of the log levels set for file, logging to a file
will not take place unless --log-file is also specified (see be‐
low).

For compatibility with older versions of OVS, any is accepted as
a word but has no effect.

-v
--verbose
Sets the maximum logging verbosity level, equivalent to --ver‐
bose=dbg.

-vPATTERN:destination:pattern
--verbose=PATTERN:destination:pattern
Sets the log pattern for destination to pattern. Refer to
ovs-appctl(8) for a description of the valid syntax for pattern.

-vFACILITY:facility
--verbose=FACILITY:facility
Sets the RFC5424 facility of the log message. facility can be
one of kern, user, mail, daemon, auth, syslog, lpr, news, uucp,
clock, ftp, ntp, audit, alert, clock2, local0, local1, local2,
local3, local4, local5, local6 or local7. If this option is not
specified, daemon is used as the default for the local system
syslog and local0 is used while sending a message to the target
provided via the --syslog-target option.

--log-file[=file]
Enables logging to a file. If file is specified, then it is
used as the exact name for the log file. The default log file
name used if file is omitted is /usr/local/var/log/open‐
vswitch/ovs-vswitchd.log.

--syslog-target=host:port
Send syslog messages to UDP port on host, in addition to the
system syslog. The host must be a numerical IP address, not a
hostname.

--syslog-method=method
Specify method how syslog messages should be sent to syslog dae‐
mon. Following forms are supported:

• libc, use libc syslog() function. Downside of using this
options is that libc adds fixed prefix to every message
before it is actually sent to the syslog daemon over
/dev/log UNIX domain socket.

• unix:file, use UNIX domain socket directly. It is possi‐
ble to specify arbitrary message format with this option.
However, rsyslogd 8.9 and older versions use hard coded
parser function anyway that limits UNIX domain socket
use. If you want to use arbitrary message format with
older rsyslogd versions, then use UDP socket to localhost
IP address instead.

• udp:ip:port, use UDP socket. With this method it is pos‐
sible to use arbitrary message format also with older
rsyslogd. When sending syslog messages over UDP socket
extra precaution needs to be taken into account, for ex‐
ample, syslog daemon needs to be configured to listen on
the specified UDP port, accidental iptables rules could
be interfering with local syslog traffic and there are
some security considerations that apply to UDP sockets,
but do not apply to UNIX domain sockets.

• null, discards all messages logged to syslog.

The default is taken from the OVS_SYSLOG_METHOD environment
variable; if it is unset, the default is libc.

Other Options
--unixctl=socket
Sets the name of the control socket on which ovs-vswitchd lis‐
tens for runtime management commands (see RUNTIME MANAGEMENT
COMMANDS, below). If socket does not begin with /, it is inter‐
preted as relative to /usr/local/var/run/openvswitch. If
--unixctl is not used at all, the default socket is /usr/lo‐
cal/var/run/openvswitch/ovs-vswitchd.pid.ctl, where pid is
ovs-vswitchd's process ID.

On Windows a local named pipe is used to listen for runtime man‐
agement commands. A file is created in the absolute path as
pointed by socket or if --unixctl is not used at all, a file is
created as ovs-vswitchd.ctl in the configured OVS_RUNDIR direc‐
tory. The file exists just to mimic the behavior of a Unix do‐
main socket.

Specifying none for socket disables the control socket feature.

-h
--help Prints a brief help message to the console.

-V
--version
Prints version information to the console.

RUNTIME MANAGEMENT COMMANDS
ovs-appctl(8) can send commands to a running ovs-vswitchd process. The
currently supported commands are described below. The command descrip‐
tions assume an understanding of how to configure Open vSwitch.

GENERAL COMMANDS
exit --cleanup
Causes ovs-vswitchd to gracefully terminate. If --cleanup is
specified, deletes flows from datapaths and releases other data‐
path resources configured by ovs-vswitchd. Otherwise, datapath
flows and other resources remains undeleted. Resources of data‐
paths that are integrated into ovs-vswitchd (e.g. the netdev
datapath type) are always released regardless of --cleanup ex‐
cept for ports with internal type. Use --cleanup to release in‐
ternal ports too.

qos/show-types interface
Queries the interface for a list of Quality of Service types
that are configurable via Open vSwitch for the given interface.

qos/show interface
Queries the kernel for Quality of Service configuration and sta‐
tistics associated with the given interface.

bfd/show [interface]
Displays detailed information about Bidirectional Forwarding De‐
tection configured on interface. If interface is not specified,
then displays detailed information about all interfaces with BFD
enabled.

bfd/set-forwarding [interface] status
Force the fault status of the BFD module on interface (or all
interfaces if none is given) to be status. status can be
"true", "false", or "normal" which reverts to the standard be‐
havior.

cfm/show [interface]
Displays detailed information about Connectivity Fault Manage‐
ment configured on interface. If interface is not specified,
then displays detailed information about all interfaces with CFM
enabled.

cfm/set-fault [interface] status
Force the fault status of the CFM module on interface (or all
interfaces if none is given) to be status. status can be
"true", "false", or "normal" which reverts to the standard be‐
havior.

stp/tcn [bridge]
Forces a topology change event on bridge if it's running STP.
This may cause it to send Topology Change Notifications to its
peers and flush its MAC table. If no bridge is given, forces a
topology change event on all bridges.

stp/show [bridge]
Displays detailed information about spanning tree on the bridge.
If bridge is not specified, then displays detailed information
about all bridges with STP enabled.

rstp/tcn [bridge]
Forces a topology change event on bridge if it's running RSTP.
This may cause it to send Topology Change Notifications to its
peers and flush its MAC table. If no bridge is given, forces a
topology change event on all bridges.

rstp/show [bridge]
Displays detailed information about rapid spanning tree on the
bridge. If bridge is not specified, then displays detailed in‐
formation about all bridges with RSTP enabled.

BRIDGE COMMANDS
These commands manage bridges.

fdb/add bridge port vlan mac
Adds mac address to a port and vlan on a bridge. This utility
can be used to pre-populate fdb table without relying on dynamic
mac learning.

fdb/del bridge vlan mac
Deletes mac address from a port and vlan on a bridge.

fdb/flush [bridge]
Flushes bridge MAC address learning table, or all learning ta‐
bles if no bridge is given.

fdb/show bridge
Lists each MAC address/VLAN pair learned by the specified
bridge, along with the port on which it was learned and the age
of the entry, in seconds.

fdb/stats-clear [bridge]
Clear bridge MAC address learning table statistics, or all sta‐
tistics if no bridge is given.

fdb/stats-show bridge
Show MAC address learning table statistics for the specified
bridge.

mdb/flush [bridge]
Flushes bridge multicast snooping table, or all snooping tables
if no bridge is given.

mdb/show bridge
Lists each multicast group/VLAN pair learned by the specified
bridge, along with the port on which it was learned and the age
of the entry, in seconds.

bridge/reconnect [bridge]
Makes bridge drop all of its OpenFlow controller connections and
reconnect. If bridge is not specified, then all bridges drop
their controller connections and reconnect.

This command might be useful for debugging OpenFlow controller
issues.

bridge/dump-flows [--offload-stats] bridge
Lists all flows in bridge, including those normally hidden to
commands such as ovs-ofctl dump-flows. Flows set up by mecha‐
nisms such as in-band control and fail-open are hidden from the
controller since it is not allowed to modify or override them.
If --offload-stats are specified then also list statistics for
offloaded packets and bytes, which are a subset of the total
packets and bytes.

BOND COMMANDS
These commands manage bonded ports on an Open vSwitch's bridges. To
understand some of these commands, it is important to understand a de‐
tail of the bonding implementation called ``source load balancing''
(SLB). Instead of directly assigning Ethernet source addresses to mem‐
bers, the bonding implementation computes a function that maps an
48-bit Ethernet source addresses into an 8-bit value (a ``MAC hash''
value). All of the Ethernet addresses that map to a single 8-bit value
are then assigned to a single member.

bond/list
Lists all of the bonds, and their members, on each bridge.

bond/show [port]
Lists all of the bond-specific information (updelay, downdelay,
time until the next rebalance) about the given bonded port, or
all bonded ports if no port is given. Also lists information
about each members: whether it is enabled or disabled, the time
to completion of an updelay or downdelay if one is in progress,
whether it is the active member, the hashes assigned to the mem‐
ber. Any LACP information related to this bond may be found us‐
ing the lacp/show command.

bond/migrate port hash member
Only valid for SLB bonds. Assigns a given MAC hash to a new
member. port specifies the bond port, hash the MAC hash to be
migrated (as a decimal number between 0 and 255), and member the
new member to be assigned.

The reassignment is not permanent: rebalancing or fail-over will
cause the MAC hash to be shifted to a new member in the usual
manner.

A MAC hash cannot be migrated to a disabled member.

bond/set-active-member port member
Sets member as the active member on port. member must currently
be enabled.

The setting is not permanent: a new active member will be se‐
lected if member becomes disabled.

bond/enable-member port member
bond/disable-member port member
Enables (or disables) member on the given bond port, skipping
any updelay (or downdelay).

This setting is not permanent: it persists only until the car‐
rier status of member changes.

bond/hash mac [vlan] [basis]
Returns the hash value which would be used for mac with vlan and
basis if specified.

lacp/show [port]
Lists all of the LACP related information about the given port:
active or passive, aggregation key, system id, and system prior‐
ity. Also lists information about each member: whether it is
enabled or disabled, whether it is attached or detached, port id
and priority, actor information, and partner information. If
port is not specified, then displays detailed information about
all interfaces with CFM enabled.

lacp/stats-show [port]
Lists various stats about LACP PDUs (number of RX/TX PDUs, bad
PDUs received) and member state (number of times its state ex‐
pired/defaulted and carrier status changed) for the given port.
If port is not specified, then displays stats of all interfaces
with LACP enabled.

DPCTL DATAPATH DEBUGGING COMMANDS
The primary way to configure ovs-vswitchd is through the Open vSwitch
database, e.g. using ovs-vsctl(8). These commands provide a debugging
interface for managing datapaths. They implement the same features
(and syntax) as ovs-dpctl(8). Unlike ovs-dpctl(8), these commands work
with datapaths that are integrated into ovs-vswitchd (e.g. the netdev
datapath type).

Do not use commands to add or remove or modify datapaths if
ovs-vswitchd is running because this interferes with ovs-vswitchd's own
datapath management.

dpctl/add-dp dp [netdev[,option]...]
Creates datapath dp, with a local port also named dp. This will
fail if a network device dp already exists.

If netdevs are specified, ovs-vswitchd adds them to the new
datapath, just as if add-if was specified.

dpctl/del-dp dp
Deletes datapath dp. If dp is associated with any network de‐
vices, they are automatically removed.

dpctl/add-if dp netdev[,option]...
Adds each netdev to the set of network devices datapath dp moni‐
tors, where dp is the name of an existing datapath, and netdev
is the name of one of the host's network devices, e.g. eth0.
Once a network device has been added to a datapath, the datapath
has complete ownership of the network device's traffic and the
network device appears silent to the rest of the system.

A netdev may be followed by a comma-separated list of options.
The following options are currently supported:

type=type
Specifies the type of port to add. The default type is
system.

port_no=port
Requests a specific port number within the datapath. If
this option is not specified then one will be automati‐
cally assigned.

key=value
Adds an arbitrary key-value option to the port's configu‐
ration.

ovs-vswitchd.conf.db(5) documents the available port types and
options.

dpctl/set-if dp port[,option]...
Reconfigures each port in dp as specified. An option of the
form key=value adds the specified key-value option to the port
or overrides an existing key's value. An option of the form
key=, that is, without a value, deletes the key-value named key.
The type and port number of a port cannot be changed, so type
and port_no are only allowed if they match the existing configu‐
ration.

dpctl/del-if dp netdev...
Removes each netdev from the list of network devices datapath dp
monitors.

dpctl/dump-dps
Prints the name of each configured datapath on a separate line.

dpctl/show [-s | --statistics] [dp...]
Prints a summary of configured datapaths, including their data‐
path numbers and a list of ports connected to each datapath.
(The local port is identified as port 0.) If -s or --statistics
is specified, then packet and byte counters are also printed for
each port.

The datapath numbers consists of flow stats and mega flow mask
stats.

The "lookups" row displays three stats related to flow lookup
triggered by processing incoming packets in the datapath. "hit"
displays number of packets matches existing flows. "missed" dis‐
plays the number of packets not matching any existing flow and
require user space processing. "lost" displays number of pack‐
ets destined for user space process but subsequently dropped be‐
fore reaching userspace. The sum of "hit" and "miss" equals to
the total number of packets datapath processed.

The "flows" row displays the number of flows in datapath.

The "masks" row displays the mega flow mask stats. This row is
omitted for datapath not implementing mega flow. "hit" displays
the total number of masks visited for matching incoming packets.
"total" displays number of masks in the datapath. "hit/pkt" dis‐
plays the average number of masks visited per packet; the ratio
between "hit" and total number of packets processed by the data‐
path.

If one or more datapaths are specified, information on only
those datapaths are displayed. Otherwise, ovs-vswitchd displays
information about all configured datapaths.

DATAPATH FLOW TABLE DEBUGGING COMMANDS
The following commands are primarily useful for debugging Open vSwitch.
The flow table entries (both matches and actions) that they work with
are not OpenFlow flow entries. Instead, they are different and consid‐
erably simpler flows maintained by the Open vSwitch kernel module. Do
not use commands to add or remove or modify datapath flows if
ovs-vswitchd is running because it interferes with ovs-vswitchd's own
datapath flow management. Use ovs-ofctl(8), instead, to work with
OpenFlow flow entries.

The dp argument to each of these commands is optional when exactly one
datapath exists, in which case that datapath is the default. When mul‐
tiple datapaths exist, then a datapath name is required.

dpctl/dump-flows [-m | --more] [--names | --no-names] [dp] [filter=fil‐
ter] [type=type] [pmd=pmd]
Prints to the console all flow entries in datapath dp's flow ta‐
ble. Without -m or --more, output omits match fields that a
flow wildcards entirely; with -m or --more, output includes all
wildcarded fields.

If filter=filter is specified, only displays the flows that
match the filter. filter is a flow in the form similar to that
accepted by ovs-ofctl(8)'s add-flow command. (This is not an
OpenFlow flow: besides other differences, it never contains
wildcards.) The filter is also useful to match wildcarded
fields in the datapath flow. As an example, fil‐
ter='tcp,tp_src=100' will match the datapath flow containing
'tcp(src=80/0xff00,dst=8080/0xff)'.

If pmd=pmd is specified, only displays flows of the specified
pmd. Using pmd=-1 will restrict the dump to flows from the main
thread. This option is only supported by the userspace data‐
path.

If type=type is specified, only displays flows of the specified
types. This option supported only for ovs-appctl
dpctl/dump-flows. type is a comma separated list, which can
contain any of the following:
ovs - displays flows handled in the ovs dp
tc - displays flows handled in the tc dp
dpdk - displays flows fully offloaded by dpdk
offloaded - displays flows offloaded to the HW
non-offloaded - displays flows not offloaded to the HW
partially-offloaded - displays flows where only part of their
proccessing is done in HW
all - displays all the types of flows

By default all the types of flows are displayed. ovs-dpctl al‐
ways acts as if the type was ovs.

dpctl/add-flow [dp] flow actions

dpctl/mod-flow [--clear] [--may-create] [-s | --statistics] [dp] flow
actions
Adds or modifies a flow in dp's flow table that, when a packet
matching flow arrives, causes actions to be executed.

The add-flow command succeeds only if flow does not already ex‐
ist in dp. Contrariwise, mod-flow without --may-create only
modifies the actions for an existing flow. With --may-create,
mod-flow will add a new flow or modify an existing one.

If -s or --statistics is specified, then mod-flow prints the
modified flow's statistics. A flow's statistics are the number
of packets and bytes that have passed through the flow, the
elapsed time since the flow last processed a packet (if ever),
and (for TCP flows) the union of the TCP flags processed through
the flow.

With --clear, mod-flow zeros out the flow's statistics. The
statistics printed if -s or --statistics is also specified are
those from just before clearing the statistics.

NOTE: flow and actions do not match the syntax used with
ovs-ofctl(8)'s add-flow command.

Usage Examples

Forward ARP between ports 1 and 2 on datapath myDP:

ovs-dpctl add-flow myDP \
"in_port(1),eth(),eth_type(0x0806),arp()" 2

ovs-dpctl add-flow myDP \
"in_port(2),eth(),eth_type(0x0806),arp()" 1

Forward all IPv4 traffic between two addresses on ports 1 and 2:

ovs-dpctl add-flow myDP \
"in_port(1),eth(),eth_type(0x800),\
ipv4(src=172.31.110.4,dst=172.31.110.5)" 2

ovs-dpctl add-flow myDP \
"in_port(2),eth(),eth_type(0x800),\
ipv4(src=172.31.110.5,dst=172.31.110.4)" 1

dpctl/add-flows [dp] file
dpctl/mod-flows [dp] file
dpctl/del-flows [dp] file
Reads flow entries from file (or stdin if file is -) and adds,
modifies, or deletes each entry to the datapath. Each flow
specification (e.g., each line in file) may start with add, mod‐
ify, or delete keyword to specify whether a flow is to be added,
modified, or deleted. A flow specification without one of these
keywords is treated based on the used command. All flow modifi‐
cations are executed as individual transactions in the order
specified.

dpctl/del-flow [-s | --statistics] [dp] flow
Deletes the flow from dp's flow table that matches flow. If -s
or --statistics is specified, then del-flow prints the deleted
flow's statistics.

dpctl/get-flow [dp] ufid:ufid [-m | --more] [--names | --no-names]
Fetches the flow from dp's flow table with unique identifier
ufid. ufid must be specified as a string of 32 hexadecimal
characters.

dpctl/del-flows [dp]
Deletes all flow entries from datapath dp's flow table.

DATAPATH FLOW CACHE COMMANDS
The following commands are useful for debugging and configuring the
datapath flow cache settings.

dpctl/cache-get-size [dp]
Prints the current cache sizes to the console.

dpctl/cache-set-size dp cache size
Set the dp's specific cache to the given size. The cache name
can be found by using the cache-get-size command.

CONNECTION TRACKING TABLE COMMANDS
The following commands are useful for debugging and configuring the
connection tracking table in the datapath.

N.B.(Linux specific): the system datapaths (i.e. the Linux kernel mod‐
ule Open vSwitch datapaths) share a single connection tracking table
(which is also used by other kernel subsystems, such as iptables, nfta‐
bles and the regular host stack). Therefore, the following commands do
not apply specifically to one datapath.

dpctl/ipf-set-enabled [dp] v4|v6
dpctl/ipf-set-disabled [dp] v4|v6
Enables or disables IP fragmentation handling for the userspace
connection tracker. Either v4 or v6 must be specified. Both
IPv4 and IPv6 fragment reassembly are enabled by default. Only
supported for the userspace datapath.

dpctl/ipf-set-min-frag [dp] v4|v6 minfrag
Sets the minimum fragment size (L3 header and data) for non-fi‐
nal fragments to minfrag. Either v4 or v6 must be specified.
For enhanced DOS security, higher minimum fragment sizes can
usually be used. The default IPv4 value is 1200 and the clamped
minimum is 400. The default IPv6 value is 1280, with a clamped
minimum of 400, for testing flexibility. The maximum fragment
size is not clamped, however, setting this value too high might
result in valid fragments being dropped. Only supported for
userspace datapath.

dpctl/ipf-set-max-nfrags [dp] maxfrags
Sets the maximum number of fragments tracked by the userspace
datapath connection tracker to maxfrags. The default value is
1000 and the clamped maximum is 5000. Note that packet buffers
can be held by the fragmentation module while fragments are in‐
complete, but will timeout after 15 seconds. Memory pool sizing
should be set accordingly when fragmentation is enabled. Only
supported for userspace datapath.

dpctl/ipf-get-status [dp] [-m | --more]
Gets the configuration settings and fragment counters associated
with the fragmentation handling of the userspace datapath con‐
nection tracker. With -m or --more, also dumps the IP fragment
lists. Only supported for userspace datapath.

dpctl/dump-conntrack [-m | --more] [-s | --statistics] [dp] [zone=zone]
Prints to the console all the connection entries in the tracker
used by dp. If zone=zone is specified, only shows the connec‐
tions in zone. With --more, some implementation specific de‐
tails are included. With --statistics timeouts and timestamps
are added to the output.

dpctl/dump-conntrack-exp [dp] [zone=zone]
Prints to the console all the expectation entries in the tracker
used by dp. If zone=zone is specified, only shows the expecta‐
tions in zone. Only supported for userspace datapath.

dpctl/flush-conntrack [dp] [zone=zone] [ct-origin-tuple [ct-reply-tu‐
ple]]
Flushes the connection entries in the tracker used by dp based
on zone and connection tracking tuple ct-origin-tuple. If ct-
tuple is not provided, flushes all the connection entries. If
zone=zone is specified, only flushes the connections in zone.

If ct-[orig|reply]-tuple is provided, flushes the connection en‐
try specified by ct-[orig|reply]-tuple in zone. The zone de‐
faults to 0 if it is not provided. The userspace connection
tracker requires flushing with the original pre-NATed tuple and
a warning log will be otherwise generated. The tuple can be
partial and will remove all connections that are matching on the
specified fields. In order to specify only ct-reply-tuple, pro‐
vide empty string as ct-origin-tuple.

Note: Currently there is a limitation for matching on ICMP, in
order to partially match on ICMP parameters the ct-[orig|re‐
ply]-tuple has to include either source or destination IP.

An example of an IPv4 ICMP ct-[orig|reply]-tuple:

"ct_nw_src=10.1.1.1,ct_nw_dst=10.1.1.2,ct_nw_proto=1,icmp_type=8,icmp_code=0,icmp_id=10"

An example of an IPv6 TCP ct-[orig|reply]-tuple:

"ct_ipv6_src=fc00::1,ct_ipv6_dst=fc00::2,ct_nw_proto=6,ct_tp_src=1,ct_tp_dst=2"

dpctl/ct-stats-show [dp] [zone=zone] [-m | --more]
Displays the number of connections grouped by protocol used by
dp. If zone=zone is specified, numbers refer to the connections
in zone. With --more, groups by connection state for each pro‐
tocol.

dpctl/ct-bkts [dp] [gt=threshold]
For each conntrack bucket, displays the number of connections
used by dp. If gt=threshold is specified, bucket numbers are
displayed when the number of connections in a bucket is greater
than threshold.

dpctl/ct-set-maxconns [dp] maxconns
Sets the maximum limit of connection tracker entries to maxconns
on dp. This can be used to reduce the processing load on the
system due to connection tracking or simply limiting connection
tracking. If the number of connections is already over the new
maximum limit request then the new maximum limit will be en‐
forced when the number of connections decreases to that limit,
which normally happens due to connection expiry. Only supported
for userspace datapath.

dpctl/ct-get-maxconns [dp]
Prints the maximum limit of connection tracker entries on dp.
Only supported for userspace datapath.

dpctl/ct-get-nconns [dp]
Prints the current number of connection tracker entries on dp.
Only supported for userspace datapath.

dpctl/ct-enable-tcp-seq-chk [dp]
dpctl/ct-disable-tcp-seq-chk [dp]
Enables or disables TCP sequence checking. When set to dis‐
abled, all sequence number verification is disabled, including
for TCP resets. This is similar, but not the same as 'be_lib‐
eral' mode, as in Netfilter. Disabling sequence number verifi‐
cation is not an optimization in itself, but is needed for some
hardware offload support which might offer some performance ad‐
vantage. Sequence number checking is enabled by default to en‐
force better security and should only be disabled if required
for hardware offload support. This command is only supported
for the userspace datapath.

dpctl/ct-get-tcp-seq-chk [dp]
Prints whether TCP sequence checking is enabled or disabled on
dp. Only supported for the userspace datapath.

dpctl/ct-set-sweep-interval [dp] ms
Sets the sweep interval. Only supported for the userspace data‐
path.

dpctl/ct-get-sweep-interval [dp]
Prints the current sweep interval in ms. Only supported for the
userspace datapath.

dpctl/ct-set-limits [dp] [default=default_limit]
[zone=zone,limit=limit]...
Sets the maximum allowed number of connections in a connection
tracking zone. A specific zone may be set to limit, and multi‐
ple zones may be specified with a comma-separated list. If a
per-zone limit for a particular zone is not specified in the
datapath, it defaults to the default per-zone limit. A default
zone may be specified with the default=default_limit argument.
Initially, the default per-zone limit is unlimited. An unlim‐
ited number of entries may be set with 0 limit.

dpctl/ct-del-limits [dp] zone=zone[,zone]...
Deletes the connection tracking limit for zone. Multiple zones
may be specified with a comma-separated list.

dpctl/ct-get-limits [dp] [zone=zone[,zone]...]
Retrieves the maximum allowed number of connections and current
counts per-zone. If zone is given, only the specified zone(s)
are printed. If no zones are specified, all the zone limits and
counts are provided. The command always displays the default
zone limit.

DPDK COMMANDS
These commands manage DPDK components.

dpdk/lcore-list
Lists the DPDK lcores and their cpu affinity. When
RTE_MAX_LCORE lcores are registered, some OVS PMD threads won't
appear.

dpdk/log-list
Lists all DPDK components that emit logs and their logging lev‐
els.

dpdk/log-set [spec]
Sets DPDK components logging level. Without any spec, sets the
logging level for all DPDK components to debug. Otherwise, spec
is a list of words separated by spaces: a word can be either a
logging level (emergency, alert, critical, error, warning, no‐
tice, info or debug) or a pattern matching DPDK components (see
dpdk/log-list command on ovs-appctl(8)) separated by a colon
from the logging level to apply.

dpdk/get-malloc-stats
Prints the heap information statistics about DPDK malloc.

DPIF-NETDEV COMMANDS
These commands are used to expose internal information (mostly statis‐
tics) about the "dpif-netdev" userspace datapath. If there is only one
datapath (as is often the case, unless dpctl/ commands are used), the
dp argument can be omitted. By default the commands present data for
all pmd threads in the datapath. By specifying the "-pmd Core" option
one can filter the output for a single pmd in the datapath.

dpif-netdev/pmd-stats-show [-pmd core] [dp]
Shows performance statistics for one or all pmd threads of the
datapath dp. The special thread "main" sums up the statistics of
every non pmd thread.

The sum of "phwol hits", "simple match hits", "emc hits", "smc
hits", "megaflow hits" and "miss" is the number of packet
lookups performed by the datapath. Beware that a recirculated
packet experiences one additional lookup per recirculation, so
there may be more lookups than forwarded packets in the data‐
path.

The MFEX Opt hits displays the number of packets that are
processed by the optimized miniflow extract implementations.

Cycles are counted using the TSC or similar facilities (when
available on the platform). The duration of one cycle depends on
the processing platform.

"idle cycles" refers to cycles spent in PMD iterations not for‐
warding any any packets. "processing cycles" refers to cycles
spent in PMD iterations forwarding at least one packet, includ‐
ing the cost for polling, processing and transmitting said pack‐
ets.

To reset these counters use dpif-netdev/pmd-stats-clear.

dpif-netdev/pmd-stats-clear [dp]
Resets to zero the per pmd thread performance numbers shown by
the dpif-netdev/pmd-stats-show and dpif-netdev/pmd-perf-show
commands. It will NOT reset datapath or bridge statistics, only
the values shown by the above commands.

dpif-netdev/pmd-perf-show [-nh] [-it iter_len] [-ms ms_len] [-pmd core]
[dp]
Shows detailed performance metrics for one or all pmds threads
of the user space datapath.

The collection of detailed statistics can be controlled by a new
configuration parameter "other_config:pmd-perf-metrics". By de‐
fault it is disabled. The run-time overhead, when enabled, is in
the order of 1%.

— used cycles
— forwared packets
— number of rx batches
— packets/rx batch
— max. vhostuser queue fill level
— number of upcalls
— cycles spent in upcalls

This raw recorded data is used threefold:

1. In histograms for each of the following metrics:
— cycles/iteration (logarithmic)
— packets/iteration (logarithmic)
— cycles/packet
— packets/batch
— max. vhostuser qlen (logarithmic)
— upcalls
— cycles/upcall (logarithmic) The histograms bins
are divided linear or logarithmic.
2. A cyclic history of the above metrics for 1024 iterations
3. A cyclic history of the cummulative/average values per
millisecond wall clock for the last 1024 milliseconds:
— number of iterations
— avg. cycles/iteration
— packets (Kpps)
— avg. packets/batch
— avg. max vhost qlen
— upcalls
— avg. cycles/upcall

The command options are:

-nh Suppress the histograms

-it iter_len
Display the last iter_len iteration stats

-ms ms_len
Display the last ms_len millisecond stats

The output always contains the following global PMD statistics:

Time: 15:24:55.270
Measurement duration: 1.008 s

pmd thread numa_id 0 core_id 1:

Iterations: 572817 (1.76 us/it)
- Used TSC cycles: 2419034712 ( 99.9 % of total cycles)
- idle iterations: 486808 ( 15.9 % of used cycles)
- busy iterations: 86009 ( 84.1 % of used cycles)
Rx packets: 2399607 (2381 Kpps, 848 cycles/pkt)
Datapath passes: 3599415 (1.50 passes/pkt)
- PHWOL hits: 0 ( 0.0 %)
- MFEX Opt hits: 3570133 ( 99.2 %)
- Simple Match hits: 0 ( 0.0 %)
- EMC hits: 336472 ( 9.3 %)
- SMC hits: 0 ( 0.0 %)
- Megaflow hits: 3262943 ( 90.7 %, 1.00 subtbl lookups/hit)
- Upcalls: 0 ( 0.0 %, 0.0 us/upcall)
- Lost upcalls: 0 ( 0.0 %)
Tx packets: 2399607 (2381 Kpps)
Tx batches: 171400 (14.00 pkts/batch)

Here "Rx packets" actually reflects the number of packets for‐
warded by the datapath. "Datapath passes" matches the number of
packet lookups as reported by the dpif-netdev/pmd-stats-show
command.

To reset the counters and start a new measurement use dpif-net‐
dev/pmd-stats-clear.

dpif-netdev/pmd-perf-log-set on|off [-b before] [-a after] [-e|-ne]
[-us usec] [-q qlen]
The userspace "netdev" datapath is able to supervise the PMD
performance metrics and detect iterations with suspicious sta‐
tistics according to the following criteria:

— The iteration lasts longer than usec microseconds (de‐
fault 250). This can be used to capture events where a
PMD is blocked or interrupted for such a period of time
that there is a risk for dropped packets on any of its Rx
queues.

— The max vhost qlen exceeds a threshold qlen (default
128). This can be used to infer virtio queue overruns and
dropped packets inside a VM, which are not visible in OVS
otherwise.

Such suspicious iterations can be logged together with their it‐
eration statistics in the ovs-vswitchd.log to be able to corre‐
late them to packet drop or other events outside OVS.

The above command enables (on) or disables (off) supervision and
logging at run-time and can be used to adjust the above thresh‐
olds for detecting suspicious iterations. By default supervision
and logging is disabled.

The command options are:

-b before
The number of iterations before the suspicious iteration
to be logged (default 5).

-a after
The number of iterations after the suspicious iteration
to be logged (default 5).

-e Extend logging interval if another suspicious iteration
is detected before logging occurs.

-ne Do not extend logging interval if another suspicious it‐
eration is detected before logging occurs (default).

-q qlen
Suspicious vhost queue fill level threshold. Increase
this to 512 if the Qemu supports 1024 virtio queue length
(default 128).

-us usec
Change the duration threshold for a suspicious iteration
(default 250 us).

Note: Logging of suspicious iterations itself consumes a considerable
amount of processing cycles of a PMD which may be visible in the itera‐
tion history. In the worst case this can lead OVS to detect another
suspicious iteration caused by logging.

If more than 100 iterations around a suspicious iteration have been
logged once, OVS falls back to the safe default values (-b 5 -a 5 -ne)
to avoid that logging itself continuously causes logging of further
suspicious iterations.

dpif-netdev/pmd-rxq-show [-pmd core] [dp]
For one or all pmd threads of the datapath dp show the list of
queue-ids with port names, which this thread polls.

dpif-netdev/pmd-rxq-rebalance [dp]
Reassigns rxqs to pmds in the datapath dp based on their current
usage.

dpif-netdev/bond-show [dp]
When "other_config:lb-output-action" is set to "true", the user‐
space datapath handles the load balancing of bonds directly in‐
stead of depending on flow recirculation (only in balance-tcp
mode).

When this is the case, the above command prints the load-balanc‐
ing information of the bonds configured in datapath dp showing
the interface associated with each bucket (hash).

dpif-netdev/subtable-lookup-prio-get
Lists the DPCLS implementations or lookup functions that are
available as well as their priorities.

dpif-netdev/subtable-lookup-prio-set lookup_function prio
Sets the priority of a lookup function by name, lookup_function,
and priority, prio, which should be a positive integer value.
The highest priority lookup function is used for classification.

The number of affected dpcls ports and subtables is returned.

dpif-netdev/dpif-impl-get
Lists the DPIF implementations that are available.

dpif-netdev/dpif-impl-set dpif_impl
Sets the DPIF to be used to dpif_impl. By default "dpif_scalar"
is used.

dpif-netdev/miniflow-parser-get
Lists the miniflow extract implementations that are available.

dpif-netdev/miniflow-parser-set [-pmd core] miniflow_impl [study_cnt]
Sets the miniflow extract to miniflow_impl for a specified PMD
or all PMDs in the case where no value is specified. By default
"scalar" is used. study_cnt defaults to 128 and indicates the
number of packets that the "study" miniflow implementation must
parse before choosing an optimal implementation.

DPIF-NETLINK COMMANDS
These commands are used to expose internal information of the "dpif-
netlink" kernel space datapath.

dpif-netlink/dispatch-mode
Displays the "dispatch-mode" for all datapaths.

NETDEV-DPDK COMMANDS
These commands manage DPDK related ports (type=dpdk*).

netdev-dpdk/set-admin-state [interface] up | down
Change the admin state for DPDK interface to up or down. If in‐
terface is not specified, then it applies to all DPDK ports.

netdev-dpdk/detach pci-address
Detaches device with corresponding pci-address from DPDK. This
command can be used to detach device if it wasn't detached auto‐
matically after port deletion. Refer to the documentation for
details and instructions.

netdev-dpdk/get-mempool-info [interface]
Prints the debug information about memory pool used by DPDK in‐
terface. If called without arguments, information of all the
available mempools will be printed. For additional mempool sta‐
tistics enable CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG while building
DPDK.

ODP-EXECUTE COMMANDS
These commands manage the "odp-execute" component.

odp-execute/action-impl-show
Lists the actions implementations that are available and high‐
lights the currently enabled one.

odp-execute/action-impl-set action_impl
Sets the action implementation to any available implementation.
By default "scalar" is used.

DATAPATH DEBUGGING COMMANDS
These commands query and modify datapaths. They are are similar to
ovs-dpctl(8) commands. dpif/show has the additional functionality, be‐
yond dpctl/show of printing OpenFlow port numbers. The other commands
are redundant and will be removed in a future release.

dpif/dump-dps
Prints the name of each configured datapath on a separate line.

dpif/show
Prints a summary of configured datapaths, including statistics
and a list of connected ports. The port information includes
the OpenFlow port number, datapath port number, and the type.
(The local port is identified as OpenFlow port 65534.)

dpif/dump-flows [-m] dp
Prints to the console all flow entries in datapath dp's flow ta‐
ble. Without -m, output omits match fields that a flow wildcards
entirely; with -m output includes all wildcarded fields.

This command is primarily useful for debugging Open vSwitch.
The flow table entries that it displays are not OpenFlow flow
entries. Instead, they are different and considerably simpler
flows maintained by the datapath module. If you wish to see the
OpenFlow flow entries, use ovs-ofctl dump-flows.

dpif/del-flows dp
Deletes all flow entries from datapath dp's flow table and un‐
derlying datapath implementation (e.g., kernel datapath module).

This command is primarily useful for debugging Open vSwitch. As
discussed in dpif/dump-flows, these entries are not OpenFlow
flow entries.

OFPROTO COMMANDS
These commands manage the core OpenFlow switch implementation (called
ofproto).

ofproto/list
Lists the names of the running ofproto instances. These are the
names that may be used on ofproto/trace.

ofproto/trace [options] [dpname] odp_flow [packet]
ofproto/trace [options] bridge br_flow [packet]]
ofproto/trace-packet-out [options] [dpname] odp_flow [packet] actions
ofproto/trace-packet-out [options] bridge br_flow [packet] actions
Traces the path of an imaginary packet through switch and re‐
ports the path that it took. The initial treatment of the
packet varies based on the command:

• ofproto/trace looks the packet up in the OpenFlow flow
table, as if the packet had arrived on an OpenFlow port.

• ofproto/trace-packet-out applies the specified OpenFlow
actions, as if the packet, flow, and actions had been
specified in an OpenFlow ``packet-out'' request.

The packet's headers (e.g. source and destination) and metadata
(e.g. input port), together called its ``flow,'' are usually all
that matter for the purpose of tracing a packet. You can spec‐
ify the flow in the following ways:

dpname odp_flow
odp_flow is a flow in the form printed by ovs-dpctl(8)'s
dump-flows command. If all of your bridges have the same
type, which is the common case, then you can omit dpname,
but if you have bridges of different types (say, both
ovs-netdev and ovs-system), then you need to specify a
dpname to disambiguate.

bridge br_flow
br_flow is a flow in the form similar to that accepted by
ovs-ofctl(8)'s add-flow command. (This is not an Open‐
Flow flow: besides other differences, it never contains
wildcards.) bridge names of the bridge through which
br_flow should be traced.

These commands support the following options:

--generate
Generate a packet from the flow (see below for more in‐
formation).

--l7 payload
--l7-len length
Accepted only with --generate (see below for more infor‐
mation).

--consistent
Accepted by ofproto-trace-packet-out only. With this op‐
tion, the command rejects actions that are inconsistent
with the specified packet. (An example of an inconsis‐
tency is attempting to strip the VLAN tag from a packet
that does not have a VLAN tag.) Open vSwitch ignores
most forms of inconsistency in OpenFlow 1.0 and rejects
inconsistencies in later versions of OpenFlow. The op‐
tion is necessary because the command does not ordinarily
imply a particular OpenFlow version. One exception is
that, when actions includes an action that only OpenFlow
1.1 and later supports (such as push_vlan), --consistent
is automatically enabled.

--ct-next flags
When the traced flow triggers conntrack actions, of‐
proto/trace will automatically trace the forked packet
processing pipeline with user specified ct_state. This
option sets the ct_state flags that the conntrack module
will report. The flags must be a comma- or space-sepa‐
rated list of the following connection tracking flags:

• trk: Include to indicate connection tracking has
taken place.

• new: Include to indicate a new flow.

• est: Include to indicate an established flow.

• rel: Include to indicate a related flow.

• rpl: Include to indicate a reply flow.

• inv: Include to indicate a connection entry in a
bad state.

• dnat: Include to indicate a packet whose destina‐
tion IP address has been changed.

• snat: Include to indicate a packet whose source IP
address has been changed.

When --ct-next is unspecified, or when there are fewer
--ct-next options than ct actions, the flags default to
trk,new.

Most commonly, one specifies only a flow, using one of the forms
above, but sometimes one might need to specify an actual packet
instead of just a flow:

Side effects.
Some actions have side effects. For example, the normal
action can update the MAC learning table, and the learn
action can change OpenFlow tables. The trace commands
only perform side effects when a packet is specified. If
you want side effects to take place, then you must supply
a packet.

(Output actions are obviously side effects too, but the
trace commands never execute them, even when one speci‐
fies a packet.)

Incomplete information.
Most of the time, Open vSwitch can figure out everything
about the path of a packet using just the flow, but in
some special circumstances it needs to look at parts of
the packet that are not included in the flow. When this
is the case, and you do not supply a packet, then a trace
command will tell you it needs a packet.

If you wish to include a packet as part of a trace operation,
there are two ways to do it:

--generate
This option, added to one of the ways to specify a flow
already described, causes Open vSwitch to internally gen‐
erate a packet with the flow described and then to use
that packet. If your goal is to execute side effects,
then --generate is the easiest way to do it, but --gener‐
ate is not a good way to fill in incomplete information,
because it generates packets based on only the flow in‐
formation, which means that the packets really do not
have any more information than the flow.

By default, for protocols that allow arbitrary L7 pay‐
loads, the generated packet has 64 bytes of payload. Use
--l7-len to change the payload length, or --l7 to specify
the exact contents of the payload.

packet This form supplies an explicit packet as a sequence of
hex digits. An Ethernet frame is at least 14 bytes long,
so there must be at least 28 hex digits. Obviously, it
is inconvenient to type in the hex digits by hand, so the
ovs-pcap(1) and ovs-tcpundump(1) utilities provide easier
ways.

With this form, packet headers are extracted directly
from packet, so the odp_flow or br_flow should specify
only metadata. The metadata can be:

skb_priority
Packet QoS priority.

pkt_mark
Mark of the packet.

ct_state
Connection state of the packet.

ct_zone
Connection tracking zone for packet.

ct_mark
Connection mark of the packet.

ct_label
Connection label of the packet.

tun_id The tunnel ID on which the packet arrived.

in_port
The port on which the packet arrived.

The in_port value is kernel datapath port number for the first
format and OpenFlow port number for the second format. The num‐
bering of these two types of port usually differs and there is
no relationship.

Usage examples:

Trace an unicast ICMP echo request on ingress port 1 to destination
MAC 00:00:5E:00:53:01
ofproto/trace br in_port=1,icmp,icmp_type=8,\
dl_dst=00:00:5E:00:53:01

Trace an unicast ICMP echo reply on ingress port 1 to destination
MAC 00:00:5E:00:53:01
ofproto/trace br in_port=1,icmp,icmp_type=0,\
dl_dst=00:00:5E:00:53:01

Trace an ARP request on ingress port 1
ofproto/trace br in_port=1,arp,arp_op=1

Trace an ARP reply on ingress port 1
ofproto/trace br in_port=1,arp,arp_op=2

VLOG COMMANDS
These commands manage ovs-vswitchd's logging settings.

vlog/set [spec]
Sets logging levels. Without any spec, sets the log level for
every module and destination to dbg. Otherwise, spec is a list
of words separated by spaces or commas or colons, up to one from
each category below:

• A valid module name, as displayed by the vlog/list com‐
mand on ovs-appctl(8), limits the log level change to the
specified module.

• syslog, console, or file, to limit the log level change
to only to the system log, to the console, or to a file,
respectively.

On Windows platform, syslog is accepted as a word and is
only useful along with the --syslog-target option (the
word has no effect otherwise).

Case is not significant within spec.

Regardless of the log levels set for file, logging to a file
will not take place unless ovs-vswitchd was invoked with the
--log-file option.

For compatibility with older versions of OVS, any is accepted as
a word but has no effect.

vlog/set PATTERN:destination:pattern
Sets the log pattern for destination to pattern. Refer to
ovs-appctl(8) for a description of the valid syntax for pattern.

vlog/list
Lists the supported logging modules and their current levels.

vlog/list-pattern
Lists logging patterns used for each destination.

vlog/close
Causes ovs-vswitchd to close its log file, if it is open. (Use
vlog/reopen to reopen it later.)

vlog/reopen
Causes ovs-vswitchd to close its log file, if it is open, and
then reopen it. (This is useful after rotating log files, to
cause a new log file to be used.)

This has no effect unless ovs-vswitchd was invoked with the
--log-file option.

vlog/disable-rate-limit [module]...
vlog/enable-rate-limit [module]...
By default, ovs-vswitchd limits the rate at which certain mes‐
sages can be logged. When a message would appear more fre‐
quently than the limit, it is suppressed. This saves disk
space, makes logs easier to read, and speeds up execution, but
occasionally troubleshooting requires more detail. Therefore,
vlog/disable-rate-limit allows rate limits to be disabled at the
level of an individual log module. Specify one or more module
names, as displayed by the vlog/list command. Specifying either
no module names at all or the keyword any disables rate limits
for every log module.

The vlog/enable-rate-limit command, whose syntax is the same as
vlog/disable-rate-limit, can be used to re-enable a rate limit
that was previously disabled.

MEMORY COMMANDS
These commands report memory usage.

memory/show
Displays some basic statistics about ovs-vswitchd's memory us‐
age. ovs-vswitchd also logs this information soon after startup
and periodically as its memory consumption grows.

COVERAGE COMMANDS
These commands manage ovs-vswitchd's ``coverage counters,'' which count
the number of times particular events occur during a daemon's runtime.
In addition to these commands, ovs-vswitchd automatically logs coverage
counter values, at INFO level, when it detects that the daemon's main
loop takes unusually long to run.

Coverage counters are useful mainly for performance analysis and debug‐
ging.

coverage/show
Displays the averaged per-second rates for the last few seconds,
the last minute and the last hour, and the total counts of all
of the coverage counters.

coverage/read-counter counter
Displays the total count for the given coverage counter.

OPENVSWITCH TUNNELING COMMANDS
These commands query and modify OVS tunnel components.

ovs/route/add ip/plen output_bridge [gw] [pkt_mark=mark] [src=src_ip]
Adds ip/plen route to vswitchd routing table. output_bridge
needs to be OVS bridge name. This command is useful if OVS
cached routes does not look right.

ovs/route/show
Print all routes in OVS routing table, This includes routes
cached from system routing table and user configured routes.

ovs/route/del ip/plen [pkt_mark=mark]
Delete ip/plen route from OVS routing table.

tnl/neigh/show

tnl/arp/show
OVS builds ARP cache by snooping are messages. This command
shows ARP cache table.

tnl/neigh/set bridge ip mac

tnl/arp/set bridge ip mac
Adds or modifies an ARP cache entry in bridge, mapping ip to
mac.

tnl/neigh/flush

tnl/arp/flush
Flush ARP table.

tnl/neigh/aging [seconds]

tnl/arp/aging [seconds]
Changes the aging time. The accepted values of seconds are be‐
tween 1 and 3600. The new entries will get the value as speci‐
fied in seconds. For the existing entries, the aging time is up‐
dated only if the current expiration is greater than seconds.

If used without arguments, it prints the current aging value.

tnl/egress_port_range [num1] [num2]
Set range for UDP source port used for UDP based Tunnels. For
example VxLAN. If case of zero arguments this command prints
current range in use.

OPENFLOW IMPLEMENTATION
This section documents aspects of OpenFlow for which the OpenFlow spec‐
ification requires documentation.

Packet buffering.
The OpenFlow specification, version 1.2, says:

Switches that implement buffering are expected to expose,
through documentation, both the amount of available buffering,
and the length of time before buffers may be reused.

Open vSwitch does not maintains any packet buffers.

Bundle lifetime
The OpenFlow specification, version 1.4, says:

If the switch does not receive any OFPT_BUNDLE_CONTROL or
OFPT_BUNDLE_ADD_MESSAGE message for an opened bundle_id for a
switch defined time greater than 1s, it may send an ofp_er‐
ror_msg with OFPET_BUNDLE_FAILED type and OFPBFC_TIMEOUT code.
If the switch does not receive any new message in a bundle apart
from echo request and replies for a switch defined time greater
than 1s, it may send an ofp_error_msg with OFPET_BUNDLE_FAILED
type and OFPBFC_TIMEOUT code.

Open vSwitch implements default idle bundle lifetime of 10 seconds.
(This is configurable via other-config:bundle-idle-timeout in the
Open_vSwitch table. See ovs-vswitchd.conf.db(5) for details.)

LIMITS
We believe these limits to be accurate as of this writing. These lim‐
its assume the use of the Linux kernel datapath.

• ovs-vswitchd started through ovs-ctl(8) provides a limit of
65535 file descriptors. The limits on the number of bridges and
ports is decided by the availability of file descriptors. With
the Linux kernel datapath, creation of a single bridge consumes
three file descriptors and each port consumes one additional
file descriptor. Other platforms may have different limita‐
tions.

• 8,192 MAC learning entries per bridge, by default. (This is
configurable via other-config:mac-table-size in the Bridge ta‐
ble. See ovs-vswitchd.conf.db(5) for details.)

• Kernel flows are limited only by memory available to the kernel.
Performance will degrade beyond 1,048,576 kernel flows per
bridge with a 32-bit kernel, beyond 262,144 with a 64-bit ker‐
nel. (ovs-vswitchd should never install anywhere near that many
flows.)

• OpenFlow flows are limited only by available memory. Perfor‐
mance is linear in the number of unique wildcard patterns. That
is, an OpenFlow table that contains many flows that all match on
the same fields in the same way has a constant-time lookup, but
a table that contains many flows that match on different fields
requires lookup time linear in the number of flows.

• 255 ports per bridge participating in 802.1D Spanning Tree Pro‐
tocol.

• 32 mirrors per bridge.

• 15 bytes for the name of a port, for ports implemented in the
Linux kernel. Ports implemented in userspace, such as patch
ports, do not have an arbitrary length limitation. OpenFlow
also limit port names to 15 bytes.

SEE ALSO
ovs-appctl(8), ovsdb-server(1).

Open vSwitch 3.3.1 ovs-vswitchd(8)