Openvswitch and Ovsdb

5/23/2018 Openvswitch and Ovsdb

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6/4/2014 Openvswitch and ovsdb | Sreenivas Makam's Blog

http://sreeninet.wordpress.com/2014/01/02/openvswitch-and-ovsdb/

Sreenivas Makam's Blog

Openvswitch and ovsdbJanuary 2, 2014 Opendaylight, ovsdb

In this blog, I will provide an overview of ovsdb, this is mainly a collection of information from various

locations.

Openvswitch is a virtual switch targeted for virtualized environments to switch traffic between VMs. Its

integrated into the latest Linux kernel.

Following are the critical components of Openvswitch.

ovs-vswitchd, a daemon that implements the switch, along with a companion Linux kernel

module for flow-based switching. We can talk to ovs-switchd using Openflow protocol.

ovsdb-server, a lightweight database server that ovs-vswitchd queries to obtain its configuration.

External clients can talk to ovsdb-server using ovsdb management protocol.

control and management cluster contains client tools to talk to ovsdb-server and ovs-vswitchd.

+----------------------+

| Control & | | Management |

| Cluster |

+----------------------+

| \

| OVSDB \ OpenFlow

| Mgmt \

| \

+============================================+

| +--------------+ +--------------+ | | | | | | |

| | ovsdb-server |-------| ovs-vswitchd | |

| | | | | |

| +--------------+ +--------------+ |

| | |

| +----------------+ |

| | Forwarding Path| |

| +----------------+ |Follow
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+============================================+

Following are some notes on the internals:

ovsdb-server maintains the switch table database and external clients can talk to ovsdb-server

using json rpc and json being the data format.

ovsdb database currently contains around 13 tables and these can be extended further.

Bridge Bridge configuration.

Port Port configuration.

Interface One physical network device in a Port.

Flow_Table OpenFlow table configuration

QoS Quality of Service configuration

Queue QoS output queue.

Mirror Port mirroring.

Controller OpenFlow controller configuration.

Manager OVSDB management connection.NetFlow NetFlow configuration.

SSL SSL configuration.

sFlow sFlow configuration.

IPFIX IPFIX configuration

ovsdb clients can use the ovsdb management protocol can manipulate the above tables.

Following are the different json rpc methods specified by the protocol.

list_dbs List databases

get_schema Get schema

transact operations on database

cancel cancel transact request

monitor monitor certain table columns

update sent by server to client for tables that are monitored

monitor_cancel cancelling monitor request

lock, steal, unlock locking, unlocking operations on database

echo to check liveliness

Using the transact rpc method, different database operations like select, insert, delete can be

done.

Following are some client tools that Open vswitch provides:

ovs-dpctl, a tool for configuring the switch kernel module.

ovs-ofctl, to list implemented flows in the OVS kernel module

ovs-vsctl, a utility for querying and updating the configuration of ovs-vswitchd.

ovs-appctl, a utility that sends commands to running Open vSwitch daemons.

ovsdb-client, a command line utility to ovsdb server.

Mininet uses openvswitch and ovsdb internally.

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To illustrate some of the theory above, I created following simple Mininet topology.

sudo mn --controller=remote,ip=192.168.56.101 --topo=linear,3

This is a 3 node linear topology.

Now, lets try to look at the contents of the database

mininet@mininet-vm:~$ sudo ovsdb-client list-dbs

Open_vSwitch

mininet@mininet-vm:~$ sudo ovsdb-client list-tables

Table

------------

Capability

SSL

Bridge

Controller

NetFlow

Port

Mirror

Queue

QoS

Interface

Open_vSwitch

sFlow

Manager

Above, we see the database and tables. Now, lets try to look at columns in bridge table:

mininet@mininet-vm:~$ sudo ovsdb-client list-columns Bridge

Column Type

------------- ---------------------------------------------------

---------------------------

status

{"key":"string","max":"unlimited","min":0,"value":"string"}

fail_mode {"key":{"enum":["set",

["secure","standalone"]],"type":"string"},"min":0}

other_config


_version "uuid"


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name "string"

datapath_type "string"

netflow {"key":

{"refTable":"NetFlow","type":"uuid"},"min":0}

ports {"key":

{"refTable":"Port","type":"uuid"},"max":"unlimited","min":0}

external_ids


flood_vlans {"key":

{"maxInteger":4095,"minInteger":0,"type":"integer"},"max":4096,"m

in":0}

_uuid "uuid"

controller {"key":

{"refTable":"Controller","type":"uuid"},"max":"unlimited","min":0

}

datapath_id {"key":"string","min":0}

stp_enable "boolean"

mirrors {"key":

{"refTable":"Mirror","type":"uuid"},"max":"unlimited","min":0}

sflow {"key":{"refTable":"sFlow","type":"uuid"},"min":0}

Now, lets try to dump the contents of bridge table.

mininet@mininet-vm:~$ sudo ovsdb-client dump Open_vSwitch

Bridge table

_uuid controller

datapath_id datapath_type external_ids fail_mode

flood_vlans mirrors name netflow other_config

ports

sflow status stp_enable

------------------------------------ ----------------------------

------------------------------------------------ ------------------ ------------- ------------ --------- ----------- ------- ----

------- -------------------------------- ------------------------

-----------------------------------------------------------------

--------------------------------------------------------------- -

---- ------ ----------

4aa95bd1-6e44-48c3-9836-a634a2b3bee9 [56efde50-b9a5-4696-98a9-

f632438ec860, 80454ec0-b75b-4ba1-83aa-c87c80e3c409]

"0000000000000001" "" {} secure []


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[] "s1" [] {datapath-id="0000000000000001"} [1ecfc08a-

cccb-432b-a6f2-a88b6953b27b, 20338ec9-a7ed-4275-9a1a-

4dce0d17f9d0, d026cd6a-c6e5-418c-bfae-8912beccbab8]

[] {} false

31ade9d7-3a84-4809-a067-21d6ab13d3a0 [c309252b-384e-4120-9180-

8c6f3e21d52d, df9f8e75-32a0-4bab-81ae-22161e5d8ce5]

"0000000000000002" "" {} secure []

[] "s2" [] {datapath-id="0000000000000002"} [4a304026-

d090-4163-8328-0d9c1f55ef51, 504ea36c-2ec6-4010-91d5-

ff9ebe6d792f, 8ddd5e79-9b74-48f2-b251-d8ee521146e4, c8e82b90-

41d5-4834-aa9b-05d6faf0baf4] [] {} false

0a3f793d-4958-44a5-9639-a36384927f58 [9e921896-32e9-4f4e-b1e2-

332fb2339f76, fc81e564-6aa5-4ad0-9518-58ce3094451b]

"0000000000000003" "" {} secure []

[] "s3" [] {datapath-id="0000000000000003"} [0c5005d8-

b999-4c6b-bf6e-a638032737f8, 25c8166d-28d8-47f5-b1fc-

69940ec42960, cc54c4d5-32b9-4e0e-9aff-42dd4fdcd1a5]

[] {} false

Above, we see the 3 bridges along with their properties.

Now, lets try to change some properties of this topology using ovs-vsctl. Lets try to delete 1 of the ports in

the bridge.

sudo ovs-vsctl del-port s2 s2-eth2

When we look at the controller for the topology now, we should see the link between s2 and s1 go away.

Once we add it back,

sudo ovs-vsctl add-port s2 s2-eth2

Link should show back on the controller topology.

Following is the generic format for ovs-vsctl.

ovs-vsctl


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Lets say, we want to mirror packets from s2-eth2 interface of bridge s2 and send towards interface s2-

eth3, we can execute the following command. This will modify the bridge and mirror table appropriately.

sudo ovs-vsctl set bridge s2 mirrors=@m -- --id=@eth2 get port

s2-eth2 -- --id=@eth3 get Port s2-eth3 -- --id=@m create mirror

name=mymirror select-dst-port=@eth2 select-src-port=@eth2 output-

port=@eth3

Do a pingall from Mininet and allow simpleforwarding controller application to install flows. To dump

the flow table, we can use ovs-ofctl. Flows can also be dumped using raw dump of the flow table from

ovs-vsctl or ovsdb-client.

mininet@mininet-vm:~$ sudo ovs-ofctl dump-flows s2

NXST_FLOW reply (xid=0x4):cookie=0x0, duration=79.866s, table=0, n_packets=1, n_bytes=98,

priority=1,ip,nw_dst=10.0.0.3 actions=output:3

cookie=0x0, duration=79.898s, table=0, n_packets=4, n_bytes=392,

priority=1,ip,nw_dst=10.0.0.1 actions=output:5

cookie=0x0, duration=79.884s, table=0, n_packets=2, n_bytes=196,

priority=1,ip,nw_dst=10.0.0.2

actions=mod_dl_dst:d2:87:9b:ac:c0:9f,output:4

We can also create a network and configure the network without using Mininet. Following is an example

for doing this:

sudo ovs-vsctl add-br s1



sudo ovs-vsctl add-port s1 patch-s1

sudo ovs-vsctl set interface patch-s1 type=patch

sudo ovs-vsctl set interface patch-s1 options:peer=patch-s2

sudo ovs-vsctl add-port s2 patch-s2

sudo ovs-vsctl set interface patch-s2 type=patch

sudo ovs-vsctl set interface patch-s2 options:peer=patch-s1

sudo ovs-vsctl set-controller tcp:192.168.56.101:6633

sudo ovs-vsctl set-controller s1 tcp:192.168.56.101:6633

sudo ovs-vsctl set-controller s2 tcp:192.168.56.101:6633


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The above set of commands will create a linear 2 node topology with a patch connection between the 2

nodes. Its not clear to me how mininet creates connection between nodes since I did not observe a patch

connection with Mininet created topology.

Opendaylight and ovsdb:

As part of Opendaylight Hydrogen release planned early 2014, ovsdb southbound plugin will be

introduced. This can allow the controller to manage vswitch using ovsdb protocol. Openflow plugin wasalready supported which allowed openflow flows to be installed. There is also a Openstack+Opendaylight

integration project happening that will allow the Openstack to use the ML2 plugin of ODL for the

networking stuff. ML2 plugin will talk to ovsdb southbound plugin. More details on this later once I

understand this better.

Following link captures more details on the integration of ovsdb with Opendaylight. I have tried this

tutorial which shows a practical example of ovsdb integration with Opendaylight. This would need us to

compile ovsdb code and copy to controller. Instructions for this is present in the tutorial as well.

References:

Open vswitch database management protocol

Open vswitch database

Opendaylight OVSDB integration

Brents blog on getting started with OVSDB

Open Vswitch project

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Openvswitch and Ovsdb

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