ovs-ofctl: Use the prepared connection to dump flows in do_dump_flows__().

[openvswitch] / FAQ

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+++ b/FAQ
@@ -3,6 +3,171 @@
 Frequently Asked Questions
 ==========================
 
 Frequently Asked Questions
 ==========================
 

+General
+-------
+
+Q: What is Open vSwitch?
+
+A: Open vSwitch is a production quality open source software switch
+   designed to be used as a vswitch in virtualized server environments.  A
+   vswitch forwards traffic between different VMs on the same physical host
+   and also forwards traffic between VMs and the physical network.  Open
+   vSwitch supports standard management interfaces (e.g. sFlow, NetFlow,
+   RSPAN, CLI), and is open to programmatic extension and control using
+   OpenFlow and the OVSDB management protocol.
+
+   Open vSwitch as designed to be compatible with modern switching
+   chipsets.  This means that it can be ported to existing high-fanout
+   switches allowing the same flexible control of the physical
+   infrastructure as the virtual infrastructure.  It also means that
+   Open vSwitch will be able to take advantage of on-NIC switching
+   chipsets as their functionality matures.
+
+Q: What virtualization platforms can use Open vSwitch?
+
+A: Open vSwitch can currently run on any Linux-based virtualization
+   platform (kernel 2.6.18 and newer), including: KVM, VirtualBox, Xen,
+   Xen Cloud Platform, XenServer. As of Linux 3.3 it is part of the
+   mainline kernel.  The bulk of the code is written in platform-
+   independent C and is easily ported to other environments.  We welcome
+   inquires about integrating Open vSwitch with other virtualization
+   platforms.
+
+Q: How can I try Open vSwitch?
+
+A: The Open vSwitch source code can be built on a Linux system.  You can
+   build and experiment with Open vSwitch on any Linux machine.
+   Packages for various Linux distributions are available on many
+   platforms, including: Debian, Ubuntu, Fedora.
+
+   You may also download and run a virtualization platform that already
+   has Open vSwitch integrated.  For example, download a recent ISO for
+   XenServer or Xen Cloud Platform.  Be aware that the version
+   integrated with a particular platform may not be the most recent Open
+   vSwitch release.
+
+Q: Does Open vSwitch only work on Linux?
+
+A: No, Open vSwitch has been ported to a number of different operating
+   systems and hardware platforms.  Most of the development work occurs
+   on Linux, but the code should be portable to any POSIX system.  We've
+   seen Open vSwitch ported to a number of different platforms,
+   including FreeBSD, Windows, and even non-POSIX embedded systems.
+
+   By definition, the Open vSwitch Linux kernel module only works on
+   Linux and will provide the highest performance.  However, a userspace
+   datapath is available that should be very portable.
+
+Q: What's involved with porting Open vSwitch to a new platform or
+   switching ASIC?
+
+A: The PORTING document describes how one would go about porting Open
+   vSwitch to a new operating system or hardware platform.
+
+Q: Why would I use Open vSwitch instead of the Linux bridge?
+
+A: Open vSwitch is specially designed to make it easier to manage VM
+   network configuration and monitor state spread across many physical
+   hosts in dynamic virtualized environments.  Please see WHY-OVS for a
+   more detailed description of how Open vSwitch relates to the Linux
+   Bridge.
+
+Q: How is Open vSwitch related to distributed virtual switches like the
+   VMware vNetwork distributed switch or the Cisco Nexus 1000V?
+
+A: Distributed vswitch applications (e.g., VMware vNetwork distributed
+   switch, Cisco Nexus 1000V) provide a centralized way to configure and
+   monitor the network state of VMs that are spread across many physical
+   hosts.  Open vSwitch is not a distributed vswitch itself, rather it
+   runs on each physical host and supports remote management in a way
+   that makes it easier for developers of virtualization/cloud
+   management platforms to offer distributed vswitch capabilities.
+
+   To aid in distribution, Open vSwitch provides two open protocols that
+   are specially designed for remote management in virtualized network
+   environments: OpenFlow, which exposes flow-based forwarding state,
+   and the OVSDB management protocol, which exposes switch port state.
+   In addition to the switch implementation itself, Open vSwitch
+   includes tools (ovs-controller, ovs-ofctl, ovs-vsctl) that developers
+   can script and extend to provide distributed vswitch capabilities
+   that are closely integrated with their virtualization management
+   platform.
+
+Q: Why doesn't Open vSwitch support distribution?
+
+A: Open vSwitch is intended to be a useful component for building
+   flexible network infrastructure. There are many different approaches
+   to distribution which balance trade-offs between simplicity,
+   scalability, hardware compatibility, convergence times, logical
+   forwarding model, etc. The goal of Open vSwitch is to be able to
+   support all as a primitive building block rather than choose a
+   particular point in the distributed design space.
+
+Q: How can I contribute to the Open vSwitch Community?
+
+A: You can start by joining the mailing lists and helping to answer
+   questions.  You can also suggest improvements to documentation.  If
+   you have a feature or bug you would like to work on, send a mail to
+   one of the mailing lists:
+
+       http://openvswitch.org/mlists/
+
+
+
+Releases
+--------
+
+Q: What does it mean for an Open vSwitch release to be LTS (long-term
+   support)?
+
+A: All official releases have been through a comprehensive testing
+   process and are suitable for production use.  Planned releases will
+   occur several times a year.  If a significant bug is identified in an
+   LTS release, we will provide an updated release that includes the
+   fix.  Releases that are not LTS may not be fixed and may just be
+   supplanted by the next major release.  The current LTS release is
+   1.4.x.
+
+Q: What features are not available in the Open vSwitch kernel datapath
+   that ships as part of the upstream Linux kernel?
+
+A: The kernel module in upstream Linux 3.3 and later does not include
+   the following features:
+
+       - Bridge compatibility, that is, support for the ovs-brcompatd
+         daemon that (if you enable it) lets "brctl" and other Linux
+         bridge tools transparently work with Open vSwitch instead.
+
+         We do not expect bridge compatibility to ever be available in
+         upstream Linux.  If you need bridge compatibility, use the
+         kernel module from the Open vSwitch distribution instead of the
+         upstream Linux kernel module.
+
+       - Tunnel virtual ports, that is, interfaces with type "gre",
+         "ipsec_gre", "capwap".  It is possible to create tunnels in
+         Linux and attach them to Open vSwitch as system devices.
+         However, they cannot be dynamically created through the OVSDB
+         protocol or set the tunnel ids as a flow action.
+
+         Work is in progress in adding these features to the upstream
+         Linux version of the Open vSwitch kernel module.  For now, if
+         you need these features, use the kernel module from the Open
+         vSwitch distribution instead of the upstream Linux kernel
+         module.
+
+       - Patch virtual ports, that is, interfaces with type "patch".
+         You can use Linux "veth" devices as a substitute.
+
+         We don't have any plans to add patch ports upstream.
+
+Q: What features are not available when using the userspace datapath?
+
+A: Tunnel and patch virtual ports are not supported, as described in the
+   previous answer.  It is also not possible to use queue-related
+   actions.  On Linux kernels before 2.6.39, maximum-sized VLAN packets
+   may not be transmitted.
+
+

 Configuration Problems
 ----------------------
 
 Configuration Problems
 ----------------------
 


@@ -60,8 +225,8 @@ Q: I created a bridge and added a couple of Ethernet ports to it,
 
    and now my network seems to have melted: connectivity is unreliable
    (even connectivity that doesn't go through Open vSwitch), all the
 
    and now my network seems to have melted: connectivity is unreliable
    (even connectivity that doesn't go through Open vSwitch), all the

-   LEDs on my physical switches are blinking, and wireshark shows
-   duplicated packets.
+   LEDs on my physical switches are blinking, wireshark shows
+   duplicated packets, and CPU usage is very high.

 
 A: More than likely, you've looped your network.  Probably, eth0 and
    eth1 are connected to the same physical Ethernet switch.  This
 
 A: More than likely, you've looped your network.  Probably, eth0 and
    eth1 are connected to the same physical Ethernet switch.  This


@@ -129,6 +294,10 @@ A: Wireless base stations generally only allow packets with the source
    point, so the same problems will show up with the Linux bridge or
    any other way to do bridging.
 
    point, so the same problems will show up with the Linux bridge or
    any other way to do bridging.
 

+Q: Is there any documentation on the database tables and fields?
+
+A: Yes.  ovs-vswitchd.conf.db(5) is a comprehensive reference.
+

 
 VLANs
 -----
 
 VLANs
 -----


@@ -150,7 +319,7 @@ A: Many drivers in Linux kernels before version 3.3 had VLAN-related
          that works around bugs in kernel drivers.  To enable VLAN
          splinters on interface eth0, use the command:
 
          that works around bugs in kernel drivers.  To enable VLAN
          splinters on interface eth0, use the command:
 

-             ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true
+           ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true

 
          For VLAN splinters to be effective, Open vSwitch must know
          which VLANs are in use.  See the "VLAN splinters" section in
 
          For VLAN splinters to be effective, Open vSwitch must know
          which VLANs are in use.  See the "VLAN splinters" section in


@@ -243,6 +412,15 @@ A: The configuration for VLANs in the Open vSwitch database (e.g. via
 Controllers
 -----------
 
 Controllers
 -----------
 

+Q: What versions of OpenFlow does Open vSwitch support?
+
+A: Open vSwitch supports OpenFlow 1.0.  It also includes a number of
+   extensions that bring many of the features from later versions of
+   OpenFlow.  Work is underway to provide support for later versions and
+   can be tracked here:
+
+       http://openvswitch.org/development/openflow-1-x-plan/
+

 Q: I'm getting "error type 45250 code 0".  What's that?
 
 A: This is a Open vSwitch extension to OpenFlow error codes.  Open
 Q: I'm getting "error type 45250 code 0".  What's that?
 
 A: This is a Open vSwitch extension to OpenFlow error codes.  Open


@@ -315,6 +493,65 @@ Q: My OpenFlow controller doesn't see the VLANs that I expect.
 
 A: See answer under "VLANs", above.
 
 
 A: See answer under "VLANs", above.
 

+Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop"
+   but I got a funny message like this:
+
+       ofp_util|INFO|normalization changed ofp_match, details:
+       ofp_util|INFO| pre: nw_dst=192.168.0.1
+       ofp_util|INFO|post:
+
+   and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst
+   match had disappeared, so that the flow ends up matching every
+   packet.
+
+A: The term "normalization" in the log message means that a flow
+   cannot match on an L3 field without saying what L3 protocol is in
+   use.  The "ovs-ofctl" command above didn't specify an L3 protocol,
+   so the L3 field match was dropped.
+
+   In this case, the L3 protocol could be IP or ARP.  A correct
+   command for each possibility is, respectively:
+
+       ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop
+
+   and 
+
+       ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop
+
+   Similarly, a flow cannot match on an L4 field without saying what
+   L4 protocol is in use.  For example, the flow match "tp_src=1234"
+   is, by itself, meaningless and will be ignored.  Instead, to match
+   TCP source port 1234, write "tcp,tp_src=1234", or to match UDP
+   source port 1234, write "udp,tp_src=1234".
+
+Q: How can I figure out the OpenFlow port number for a given port?
+
+A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to
+   respond with an OFPT_FEATURES_REPLY that, among other information,
+   includes a mapping between OpenFlow port names and numbers.  From a
+   command prompt, "ovs-ofctl show br0" makes such a request and
+   prints the response for switch br0.
+
+   The Interface table in the Open vSwitch database also maps OpenFlow
+   port names to numbers.  To print the OpenFlow port number
+   associated with interface eth0, run:
+
+       ovs-vsctl get Interface eth0 ofport
+
+   You can print the entire mapping with:
+
+       ovs-vsctl -- --columns=name,ofport list Interface
+
+   but the output mixes together interfaces from all bridges in the
+   database, so it may be confusing if more than one bridge exists.
+
+   In the Open vSwitch database, ofport value -1 means that the
+   interface could not be created due to an error.  (The Open vSwitch
+   log should indicate the reason.)  ofport value [] (the empty set)
+   means that the interface hasn't been created yet.  The latter is
+   normally an intermittent condition (unless ovs-vswitchd is not
+   running).
+

 Contact 
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 Contact 
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