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0896dc19ef
While sending a reply to the monitor_cond_since request, server
includes the last transaction ID. And it sends new IDs with each
subsequent update. Current implementation doesn't use the one
supplied with a monitor reply, and only takes into account IDs
provided with monitor updates. That may cause various issues:
1. Performance: During initialization, the last-id is set to zero.
If re-connection will happen after receiving a monitor reply,
but before any monitor update, the client will send a new
monitor request with an all-zero last-id and will re-download
the whole database again.
2. Data inconsistency: Assuming one of the clients sends a
transaction, but our python client disconnects before receiving
a monitor update for this transaction. The last-id will point
to a database state before this transaction. On re-connection,
this last-id will be sent and the monitor reply will contain
a diff with a new data from that transaction. But if another
disconnection happens right after that, on second re-connection
our python client will send another monitor_cond_since with
exactly the same last-id. That will cause receiving the same
set of updates again. And since it's an update2 message with
a diff of the data, the client will remove previously applied
result of the transaction. At this point it will have a
different database view with the server potentially leading
to all sorts of data inconsistency problems.
Fix that by always updating the last-id from the latest monitor
reply.
Fixes: 46d44cf3be0d ("python: idl: Add monitor_cond_since support.")
Acked-by: Simon Horman <horms@ovn.org>
Acked-by: Han Zhou <hzhou@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
.. NOTE(stephenfin): If making changes to this file, ensure that the
start-after/end-before lines found in 'Documentation/intro/what-is-ovs'
are kept up-to-date.
============
Open vSwitch
============
.. image:: https://github.com/openvswitch/ovs/workflows/Build%20and%20Test/badge.svg
:target: https://github.com/openvswitch/ovs/actions
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.. image:: https://api.cirrus-ci.com/github/openvswitch/ovs.svg
:target: https://cirrus-ci.com/github/openvswitch/ovs
What is Open vSwitch?
---------------------
Open vSwitch is a multilayer software switch licensed under the open source
Apache 2 license. Our goal is to implement a production quality switch
platform that supports standard management interfaces and opens the forwarding
functions to programmatic extension and control.
Open vSwitch is well suited to function as a virtual switch in VM environments.
In addition to exposing standard control and visibility interfaces to the
virtual networking layer, it was designed to support distribution across
multiple physical servers. Open vSwitch supports multiple Linux-based
virtualization technologies including KVM, and VirtualBox.
The bulk of the code is written in platform-independent C and is easily ported
to other environments. The current release of Open vSwitch supports the
following features:
- Standard 802.1Q VLAN model with trunk and access ports
- NIC bonding with or without LACP on upstream switch
- NetFlow, sFlow(R), and mirroring for increased visibility
- QoS (Quality of Service) configuration, plus policing
- Geneve, GRE, VXLAN, STT, ERSPAN, GTP-U, SRv6, Bareudp, and LISP tunneling
- 802.1ag connectivity fault management
- OpenFlow 1.0 plus numerous extensions
- Transactional configuration database with C and Python bindings
- High-performance forwarding using a Linux kernel module
Open vSwitch can also operate entirely in userspace without assistance from
a kernel module. This userspace implementation should be easier to port than
the kernel-based switch. OVS in userspace can access Linux or DPDK devices.
Note Open vSwitch with userspace datapath and non DPDK devices is considered
experimental and comes with a cost in performance.
What's here?
------------
The main components of this distribution are:
- ovs-vswitchd, a daemon that implements the switch, along with a companion
Linux kernel module for flow-based switching.
- ovsdb-server, a lightweight database server that ovs-vswitchd queries to
obtain its configuration.
- ovs-dpctl, a tool for configuring the switch kernel module.
- Scripts and specs for building RPMs for Red Hat Enterprise Linux and
deb packages for Ubuntu/Debian.
- 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.
Open vSwitch also provides some tools:
- ovs-ofctl, a utility for querying and controlling OpenFlow switches and
controllers.
- ovs-pki, a utility for creating and managing the public-key infrastructure
for OpenFlow switches.
- ovs-testcontroller, a simple OpenFlow controller that may be useful for
testing (though not for production).
- A patch to tcpdump that enables it to parse OpenFlow messages.
What other documentation is available?
--------------------------------------
.. TODO(stephenfin): Update with a link to the hosting site of the docs, once
we know where that is
To install Open vSwitch on a regular Linux or FreeBSD host, please read the
`installation guide <Documentation/intro/install/general.rst>`__. For specifics
around installation on a specific platform, refer to one of the `other
installation guides <Documentation/intro/install/index.rst>`__
For answers to common questions, refer to the `FAQ <Documentation/faq>`__.
To learn about some advanced features of the Open vSwitch software switch, read
the `tutorial <Documentation/tutorials/ovs-advanced.rst>`__.
Each Open vSwitch userspace program is accompanied by a manpage. Many of the
manpages are customized to your configuration as part of the build process, so
we recommend building Open vSwitch before reading the manpages.
License
-------
The following is a summary of the licensing of files in this distribution.
As mentioned, Open vSwitch is licensed under the open source Apache 2 license.
Some files may be marked specifically with a different license, in which case
that license applies to the file in question.
Files under the datapath directory are licensed under the GNU General Public
License, version 2.
File build-aux/cccl is licensed under the GNU General Public License, version 2.
The following files are licensed under the 2-clause BSD license.
include/windows/getopt.h
lib/getopt_long.c
lib/conntrack-tcp.c
The following files are licensed under the 3-clause BSD-license
include/windows/netinet/icmp6.h
include/windows/netinet/ip6.h
lib/strsep.c
Files lib/sflow*.[ch] are licensed under the terms of either the
Sun Industry Standards Source License 1.1, that is available at:
http://host-sflow.sourceforge.net/sissl.html
or the InMon sFlow License, that is available at:
http://www.inmon.com/technology/sflowlicense.txt
Contact
-------
bugs@openvswitch.org