OVS-FLOWVIZ(8) Open vSwitch OVS-FLOWVIZ(8)

NAME
ovs-flowviz - utility for visualizing OpenFlow and datapath flows

SYNOPSIS
ovs-flowviz [-i [alias,]file | --input [alias,]file] [-c file | --con‐
fig file] [-f filter | --filter filter] [-l filter | --highlight fil‐
ter] [--style style] flow-type format [args…]

ovs-flowviz --help

DESCRIPTION
ovs-flowviz helps visualize OpenFlow and datapath flow dumps in differ‐
ent formats in order to make them more easily understood.

ovs-flowviz reads flows from stdin or from a file specified by the
--input option, filters them, highlights them, and finally outputs them
in one of the predefined formats.

OPTIONS
-h, --help
Print a brief help message to the console.

-i [<alias>,]<file>, --input [<alias>,]<file>
File to read flows from. If not provided, ovs-flowviz will read
flows from stdin.

This option can be specified multiple times. The file path can
prepended by an alias that will be shown in the output. For ex‐
ample: --input node1,/path/to/file1 --input node2,/path/to/file2

-c <file>, --config <file>
Style configuration file to use, overriding the default one.
Styles defined in the style configuration file can be selected
using the --style option.

For more details on the style configuration file, see the Style
Configuration File section below.

-f <filter>, --filter <filter>
Flow filter expression. Only those flows matching the expression
will be shown (although some formats implement filtering differ‐
ently, see the Datapath tree format section below).

The filtering syntax is detailed in Filtering Syntax.

-l <filter>, --highlight <filter>
Highlight the flows that match the provided filter expression.

The filtering syntax is detailed in Filtering Syntax.

--style <style>
Style. The selected style must be defined in the style configu‐
ration file.

flow-type
openflow or datapath.

format See the Supported formats section.

SUPPORTED FORMATS
ovs-flowviz supports several visualization formats for both OpenFlow
and datapath flows:
┌───────────┬─────────┬─────────────────────┐
│ Flow Type │ Format │ Description │
├───────────┼─────────┼─────────────────────┤
│ Both │ console │ Prints the flows in │
│ │ │ a configurable, │
│ │ │ colorful style in │
│ │ │ the console. │
├───────────┼─────────┼─────────────────────┤
│ Both │ json │ Prints the flows in │
│ │ │ JSON format. │
├───────────┼─────────┼─────────────────────┤
│ Both │ html │ Prints the flows in │
│ │ │ an HTML list. │
├───────────┼─────────┼─────────────────────┤
│ OpenFlow │ cookie │ Prints the flows in │
│ │ │ the console sorted │
│ │ │ by cookie. │
├───────────┼─────────┼─────────────────────┤
│ OpenFlow │ logic │ Prints the logical │
│ │ │ structure of flows │
│ │ │ in the console. │
├───────────┼─────────┼─────────────────────┤
│ Datapath │ tree │ Prints the flows as │
│ │ │ a tree structure │
│ │ │ arranged by re‐ │
│ │ │ circ_id and │
│ │ │ in_port. │
├───────────┼─────────┼─────────────────────┤
│ Datapath │ graph │ Prints a graphviz │
│ │ │ graph of the flows │
│ │ │ arranged by re‐ │
│ │ │ circ_id and │
│ │ │ in_port. │
└───────────┴─────────┴─────────────────────┘

Console format
The console format works for both OpenFlow and datapath flow types, and
prints flows in the terminal using the style determined by the --style
option.

Arguments:

-h, --heat-map
Color of the packet and byte counters to reflect their relative
size. The color gradient goes through the following colors:
blue (coldest, lowest), cyan, green, yellow, red (hottest, high‐
est)

Note filtering is applied before the range is calculated.

JSON format
The json format works for both OpenFlow and datapath flow types, and
prints flows in JSON format. See the JSON Syntax section for more de‐
tails.

HTML format
The html format works for both OpenFlow and datapath flows, and prints
flows in an HTML table that offers some basic interactivity. OpenFlow
flows are sorted in tables and datapath flows are arranged in flow
trees (see Datapath tree format for more details).

Styles defined via Style Configuration File and selected via --style
option also apply to the html format.

OpenFlow cookie format
The OpenFlow cookie format is similar to the console format but instead
of arranging the flows by table, it arranges the flows by cookie.

OpenFlow logic format
The OpenFlow logic format helps visualize the logic structure of Open‐
Flow pipelines by arranging flows into logical blocks. A logical block
is a set of flows that have:

• Same priority.

• Match on the same fields (regardless of the match value and mask).

• Execute the same actions (regardless of the actions’ arguments, ex‐
cept for resubmit and output).

• Optionally, the cookie can be included as part of the logical flow.

Arguments:

-s, --show-flows
Show all the flows under each logical block.

-d, --ovn-detrace
Use ovn-detrace.py script to extract cookie information (implies
‘-c’).

-c, --cookie
Consider the cookie in the logical block.

--ovn-detrace-path <path>
Use an alternative path to search for ovn_detrace.py.

--ovnnb-db <conn>
OVN NB database connection method (implies ‘-d’). Default:
“unix:/var/run/ovn/ovnnb_db.sock”.

--ovnsb-db <conn>
OVN SB database connection method (implies ‘-d’). Default:
“unix:/var/run/ovn/ovnsb_db.sock”.

--o <filter>, --ovn-filter <filter>
Specify the filter to be run on the ovn-detrace information.
Syntax: python regular expression (See ‐
https://docs.python.org/3/library/re.html).

-h, --heat-map
Change the color of the packet and byte counters to reflect
their relative size. The color gradient goes through the follow‐
ing colors: blue (coldest, lowest), cyan, green, yellow, red
(hottest, highest)

Note filtering is applied before the range is calculated.

Datapath tree format
The datapath tree format arranges datapath flows in a hierarchical
tree. The tree is comprised of blocks with the same recirc_id and
in_port. Within those blocks, flows with the same action are combined.
And matches which are the same are omitted to reduce the visual noise.

When a flow’s actions includes the recirc() action with a specific re‐
circ_id, flows matching on that recirc_id and the same in_port are
listed below. This is done recursively for all actions.

The result is a hierarchical representation that shows how actions are
related to each other via recirculation. Note that flows with a spe‐
cific non-zero recirc_id are listed below each group of flows that have
a corresponding recirc() action. Therefore, the output contains dupli‐
cated flows and can be verbose.

Filtering works in a slightly different way for datapath flow trees.
Unlike other formats where a filter simply removes non-matching flows,
the output of a filtered datapath flow tree will show full sub-trees
that contain at least one flow that satisfies the filter.

The html format prints this same tree as an interactive HTML table and
the graph format shows the same tree as a graphviz graph.

Datapath graph format
The datapath graph generates a graphviz visual representation of the
same tree-like flow hierarchy that the tree format prints.

Arguments:

-h, --html
Print the graphviz format as an svg image alongside an interac‐
tive HTML table of flows.

JSON SYNTAX
Printing a single-file OpenFlow or datapath dump without PMD thread
blocks in json format results in a list of JSON objects, each repre‐
senting a flow.

This list can be found inside one or more levels of JSON dictionaries
if multiple files are processed (filename used as key) or if PMD thread
blocks are found in datapath flows (name of the thread used as key).

Each flow object includes the following keys:

orig Original flow string.

info Object with the flow information such as: cookie, duration, ta‐
ble, n_packets, n_bytes, etc.

match Object with the flow match. For each match, the object contains
a key-value where the key is the name of the match as defined in
ovs-fields(7) and ovs-ofctl(8), and the value represents the
match value. The way each value is represented depends on its
type. See Value representation.

actions
List of action objects. Each action is represented by an JSON
object that has one key and one value. The key corresponds to
the action name. The value represents the arguments of the key.
See Action representation.

ufid The UFID (datapath flows only).

Value representation
Values are represented differently depending on their type:

• Flags: The value of flags is true.

• Decimal / Hexadecimal: Represented by their integer value. If they
support masking, represented by a dictionary with two keys: value
contains the field value and mask contains the mask. Both are inte‐
gers.

• Ethernet: Represented by a string: {address}[/{mask}]

• IPv4 / IPv6: Represented by a string {address}[/{mask}]

• Registers: Represented by a dictionary with three keys: field` con‐
tains the field value (string), start, and end represent the first
and last bit of the register value.

For example, the register

NXM_NX_REG10[0..15]

is represented as

{
"field": "NXM_NX_REG10",
"start": 0,
"end": 15
},

Action representation
Actions are generally represented by an object that has a single key
and value. The key is the action name as defined ovs-actions(7).

The value of actions that have no arguments (such as drop) is (boolean)
true.

The value of actions that have a list of arguments (e.g: resub‐
mit([port],[table],[ct])) is an object that has the name of the argu‐
ment as key. The argument names for each action is defined in ovs-ac‐
tions. For example, the action

resubmit(,10)

is represented as

{
"resubmit": {
"port": "",
"table": 10
}
}

The value of actions that have a key-word list as arguments (e.g:
ct([argument])) is an object whose keys correspond to the keys defined
in ovs-actions(7). The way values are represented depends on the type
of the argument. For example, the action

ct(table=14,zone=NXM_NX_REG12[0..15],nat)

is represented as

{
"ct": {
"table": 14,
"zone": {
"field": "NXM_NX_REG12",
"start": 0,
"end": 15
},
"nat": true
}
}

STYLE CONFIGURATION FILE
The style configuration file is selected via the --config option and
has INI syntax. It can define any number of styles to be used by both
console and html formats. Once defined in the configuration file, for‐
mats are selected using the --style option.

INI sections are used to define styles, [styles.mystyle] defines a
style called mystle. Within a section styles can be defined as:

[FORMAT].[PORTION].[SELECTOR].[ELEMENT] = [VALUE]

FORMAT Either console or html

PORTION
Part of the key-value the style applies to: key to indicate the
key part of a key-value, value to indicate the value part of a
key-value, flag to indicate a single flag or delim to indicate
delimiters such as parentheses, brackets, etc.

SELECTOR
Select the key-value the style applies to: highlighted to indi‐
cate highlighted key-values, type.<type> to indicate certain
types such as IPAddress or EthMask or <keyname> to select a par‐
ticular key name.

ELEMENT
Select the style element to modify: color or underline (only for
console format).

VALUE Ether a color hex, other color names defined in the rich python
library (‐
https://rich.readthedocs.io/en/stable/appendix/colors.html) or
true if the element is underline.

A default configuration file is shipped with ovs-flowviz and its path
is printed in the --help output. A detailed description of the syntax
alongside some examples are available there.

FILTERING SYNTAX
ovs-flowviz provides rich highlighting and filtering. The special com‐
mand ovs-flowviz filter dumps the filtering syntax:

$ ovs-flowviz filter
Filter Syntax
*************

[! | not ] {key}[[.subkey]...] [OPERATOR] {value})] [LOGICAL OPERATOR] ...

Comparison operators:
= equality
< less than
> more than
~= masking (valid for IP and Ethernet fields)

Logical operators:
!{expr}: NOT
{expr} && {expr}: AND
{expr} || {expr}: OR

Matches and flow metadata:
To compare against a match or info field, use the field directly, e.g:
priority=100
n_bytes>10
Use simple keywords for flags:
tcp and ip_src=192.168.1.1

Actions:
Actions values might be dictionaries, use subkeys to access individual
values, e.g:
output.port=3
Use simple keywords for flags
drop

Examples of valid filters:
nw_addr~=192.168.1.1 && (tcp_dst=80 || tcp_dst=443)
arp=true && !arp_tsa=192.168.1.1
n_bytes>0 && drop=true

Example expressions:

n_bytes > 0 and drop
nw_src~=192.168.1.1 or arp.tsa=192.168.1.1
! tcp && output.port=2

EXAMPLES
Print OpenFlow flows sorted by cookie adding OVN data to each one:

$ ovs-flowviz -i flows.txt openflow cookie --ovn-detrace

Print OpenFlow logical structure, showing the flows and heat-map:

$ ovs-flowviz -i flows.txt openflow logic --show-flows --heat-map

Display OpenFlow flows in HTML format with “light” style and highlight
drops:

$ ovs-flowviz -i flows.txt --style "light" --highlight "n_packets > 0 and drop" openflow html > flows.html

Display the datapath flows in an interactive graphviz + HTML view:

$ ovs-flowviz -i flows.txt datapath graph --html > flows.html

Display the datapath flow trees that lead to packets being sent to port
10:

$ ovs-flowviz -i flows.txt --filter "output.port=10" datapath tree

AUTHOR
The Open vSwitch Development Community

3.6 Aug 18, 2025 OVS-FLOWVIZ(8)