ovs-actions(7) — Linux manual page

NAME | INTRODUCTION | OUTPUT ACTIONS | ENCAPSULATION AND DECAPSULATION ACTIONS | FIELD MODIFICATION ACTIONS | METADATA ACTIONS | FIREWALLING ACTIONS | PROGRAMMING AND CONTROL FLOW ACTIONS | OTHER ACTIONS | INSTRUCTIONS | AUTHOR | COPYRIGHT | COLOPHON

OVS-ACTIONS(7)                Open vSwitch                OVS-ACTIONS(7)

NAME         top

       ovs-actions - OpenFlow actions and instructions with Open vSwitch
       extensions

INTRODUCTION         top

       This document aims to comprehensively document all of the
       OpenFlow actions and instructions, both standard and
       non-standard, supported by Open vSwitch, regardless of origin.
       The document includes information of interest to Open vSwitch
       users, such as the semantics of each supported action and the
       syntax used by Open vSwitch tools, and to developers seeking to
       build controllers and switches compatible with Open vSwitch, such
       as the wire format for each supported message.

   Actions
       In this document, we define an action as an OpenFlow action,
       which is a kind of command that specifies what to do with a
       packet.  Actions are used in OpenFlow flows to describe what to
       do when the flow matches a packet, and in a few other places in
       OpenFlow.  Each version of the OpenFlow specification defines
       standard actions, and beyond that many OpenFlow switches,
       including Open vSwitch, implement extensions to the standard.

       OpenFlow groups actions in two ways: as an action list or an
       action set, described below.

   Action Lists
       An action list, a concept present in every version of OpenFlow,
       is simply an ordered sequence of actions.  The OpenFlow
       specifications require a switch to execute actions within an
       action list in the order specified, and to refuse to execute an
       action list entirely if it cannot implement the actions in that
       order [OpenFlow 1.0, section 3.3], with one exception: when an
       action list outputs multiple packets, the switch may output the
       packets in an order different from that specified.  Usually, this
       exception is not important, especially in the common case when
       the packets are output to different ports.

   Action Sets
       OpenFlow 1.1 introduced the concept of an action set.  An action
       set is also a sequence of actions, but the switch reorders the
       actions and drops duplicates according to rules specified in the
       OpenFlow specifications.  Because of these semantics, some
       standard OpenFlow actions cannot usefully be included in an
       action set.  For some, but not all, Open vSwitch extension
       actions, Open vSwitch defines its own action set semantics and
       ordering.

       The OpenFlow pipeline has an action set associated with it as a
       packet is processed.  After pipeline processing is otherwise
       complete, the switch executes the actions in the action set.

       Open vSwitch applies actions in an action set in the following
       order: Except as noted otherwise below, the action set only
       executes at most a single action of each type, and when more than
       one action of a given type is present, the one added to the set
       later replaces the earlier action:

          1.  strip_vlan

          2.  pop_mpls

          3.  decap

          4.  encap

          5.  push_mpls

          6.  push_vlan

          7.  dec_ttl

          8.  dec_mpls_ttl

          9.  dec_nsh_ttl

          10. All of the following actions are executed in the order
              added to the action set, with cumulative effect.  That is,
              when multiple actions modify the same part of a field, the
              later modification takes effect, and when they modify
              different parts of a field (or different fields), then
              both modifications are applied:

                  • loadmovemod_dl_dstmod_dl_srcmod_nw_dstmod_nw_srcmod_nw_tosmod_nw_ecnmod_nw_ttlmod_tp_dstmod_tp_srcmod_vlan_pcpmod_vlan_vidset_fieldset_tunnelset_tunnel64

          11. set_queue

          12. group, output, resubmit, ct_clear, or ct.  If more than
              one of these actions is present, then the one listed
              earliest above is executed and the others are ignored,
              regardless of the order in which they were added to the
              action set.  (If none of these actions is present, the
              action set has no real effect, because the modified packet
              is not sent anywhere and thus the modifications are not
              visible.)

       An action set may only contain the actions listed above.

   Error Handling
       Packet processing can encounter a variety of errors:

       Bridge not found
              Open vSwitch supports an extension to the standard
              OpenFlow controller action called a continuation, which
              allows the controller to interrupt and later resume the
              processing of a packet through the switch pipeline.  This
              error occurs when such a packet’s processing cannot be
              resumed, e.g.  because the bridge processing it has been
              destroyed.  Open vSwitch reports this error to the
              controller as Open vSwitch extension error NXR_STALE.

              This error prevents packet processing entirely.

       Recursion too deep
              While processing a given packet, Open vSwitch limits the
              flow table recursion depth to 64, to ensure that packet
              processing uses a finite amount of time and space.
              Actions that count against the recursion limit include
              resubmit from a given OpenFlow table to the same or an
              earlier table, group, and output to patch ports.

              A resubmit from one table to a later one (or,
              equivalently, a goto_table instruction) does not count
              against the depth limit because resubmits to strictly
              monotonically increasing tables will eventually terminate.
              OpenFlow tables are most commonly traversed in numerically
              increasing order, so this limit has little effect on
              conventionally designed OpenFlow pipelines.

              This error terminates packet processing.  Any previous
              side effects (e.g. output actions) are retained.

              Usually this error indicates a loop or other bug in the
              OpenFlow flow tables.  To assist debugging, when this
              error occurs, Open vSwitch 2.10 and later logs a trace of
              the packet execution, as if by ovs-appctl ofproto/trace,
              rate-limited to one per minute to reduce the log volume.

       Too many resubmits
              Open vSwitch limits the total number of resubmit actions
              that a given packet can execute to 4,096.  For this
              purpose, goto_table instructions and output to the table
              port are treated like resubmit.  This limits the amount of
              time to process a single packet.

              Unlike the limit on recursion depth, the limit on
              resubmits counts all resubmits, regardless of direction.

              This error has the same effect, including logging, as
              exceeding the recursion depth limit.

       Stack too deep
              Open vSwitch limits the amount of data that the push
              action can put onto the stack at one time to 64 kB of
              data.

              This error terminates packet processing.  Any previous
              side effects (e.g. output actions) are retained.

       No recirculation context / Recirculation conflict
              These errors indicate internal errors inside Open vSwitch
              and should generally not occur.  If you notice recurring
              log messages about these errors, please report a bug.

       Too many MPLS labels
              Open vSwitch can process packets with any number of MPLS
              labels, but its ability to push and pop MPLS labels is
              limited, currently to 3 labels.  Attempting to push more
              than the supported number of labels onto a packet, or to
              pop any number of labels from a packet with more than the
              supported number, raises this error.

              This error terminates packet processing, retaining any
              previous side effects (e.g. output actions).  When this
              error arises within the execution of a group bucket, it
              only terminates that bucket’s execution, not packet
              processing overall.

       Invalid tunnel metadata
              Open vSwitch raises this error when it processes a Geneve
              packet that has TLV options with an invalid form, e.g.
              where the length in a TLV would extend past the end of the
              options.

              This error prevents packet processing entirely.

       Unsupported packet type
              When a encap action encapsulates a packet, Open vSwitch
              raises this error if it does not support the combination
              of the new encapsulation with the current packet.
              encap(ethernet) raises this error if the current packet is
              not an L3 packet, and encap(nsh) raises this error if the
              current packet is not Ethernet, IPv4, IPv6, or NSH.

              The decap action is supported only for packet types
              ethernet, NSH and MPLS.  Openvswitch raises this error for
              other packet types.  When a decap action decapsulates a
              packet, Open vSwitch raises this error if it does not
              support the type of inner packet.  decap of an Ethernet
              header raises this error if a VLAN header is present,
              decap of a NSH packet raises this error if the NSH inner
              packet is not Ethernet, IPv4, IPv6, or NSH.

              This error terminates packet processing, retaining any
              previous side effects (e.g. output actions).  When this
              error arises within the execution of a group bucket, it
              only terminates that bucket’s execution, not packet
              processing overall.

   Inconsistencies
       OpenFlow 1.0 allows any action to be part of any flow, regardless
       of the flow’s match.  Some combinations do not make sense, e.g.
       an set_nw_tos action in a flow that matches only ARP packets or
       strip_vlan in a flow that matches packets without VLAN tags.
       Other combinations have varying results depending on the kind of
       packet that the flow processes, e.g. a set_nw_src action in a
       flow that does not match on Ethertype will be treated as a no-op
       when it processes a non-IPv4 packet.  Nevertheless OVS allows all
       of the above in conformance with OpenFlow 1.0, that is, the
       following will succeed:

          $ ovs-ofctl -O OpenFlow10 add-flow br0 arp,actions=mod_nw_tos:12
          $ ovs-ofctl -O OpenFlow10 add-flow br0 dl_vlan=0xffff,actions=strip_vlan
          $ ovs-ofctl -O OpenFlow10 add-flow br0 actions=mod_nw_src:1.2.3.4

       Open vSwitch calls these kinds of combinations inconsistencies
       between match and actions.  OpenFlow 1.1 and later forbid
       inconsistencies, and disallow the examples described above by
       preventing such flows from being added.  All of the above, for
       example, will fail with an error message if one replaces
       OpenFlow10 by OpenFlow11.

       OpenFlow 1.1 and later cannot detect and disallow all
       inconsistencies.  For example, the write_actions instruction
       arbitrarily delays execution of the actions inside it, which can
       even be canceled with clear_actions, so that there is no way to
       ensure that its actions are consistent with the packet at the
       time they execute.  Thus, actions with write_actions and some
       other contexts are exempt from consistency requirements.

       When OVS executes an action inconsistent with the packet, it
       treats it as a no-op.

   Inter-Version Compatibility
       Open vSwitch supports multiple OpenFlow versions simultaneously
       on a single switch.  When actions are added with one OpenFlow
       version and then retrieved with another, Open vSwitch does its
       best to translate between them.

       Inter-version compatibility issues can still arise when different
       connections use different OpenFlow versions.  Backward
       compatibility is the most obvious case.  Suppose, for example,
       that an OpenFlow 1.1 session adds a flow with a push_vlan action,
       for which there is no equivalent in OpenFlow 1.0.  If an OpenFlow
       1.0 session retrieves this flow, Open vSwitch must somehow
       represent the action.

       Forward compatibility can also be an issue, because later
       OpenFlow versions sometimes remove functionality.  The best
       example is the enqueue action from OpenFlow 1.0, which OpenFlow
       1.1 removed.

       In practice, Open vSwitch uses a variety of strategies for
       inter-version compatibility:

       • Most standard OpenFlow actions, such as output actions,
         translate without compatibility issues.

       • Open vSwitch supports its extension actions in every OpenFlow
         version, so they do not pose inter-version compatibility
         problems.

       • Open vSwitch sometimes adds extension actions to ensure
         backward or forward compatibility.  For example, for backward
         compatibility with the group action added in OpenFlow 1.1, Open
         vSwitch includes an OpenFlow 1.0 extension group action.

       Perfect inter-version compatibility is not possible, so best
       results require OpenFlow connections to use a consistent version.
       One may enforce use of a particular version by setting the
       protocols column for a bridge, e.g. to force br0 to use only
       OpenFlow 1.3:

          ovs-vsctl set bridge br0 protocols=OpenFlow13

   Field Specifications
       Many Open vSwitch actions refer to fields.  In such cases, fields
       may usually be referred to by their common names, such as eth_dst
       for the Ethernet destination field, or by their full OXM or NXM
       names, such as NXM_OF_ETH_DST or OXM_OF_ETH_DST.  Before Open
       vSwitch 2.7, only OXM or NXM field names were accepted.

       Many actions that act on fields can also act on subfields, that
       is, parts of fields, written as field[start..end], where start is
       the first bit and end is the last bit to use in field, e.g.
       vlan_tci[13..15] for the VLAN PCP.  A single-bit subfield may
       also be written as field[offset], e.g. vlan_tci[13] for the
       least-significant bit of the VLAN PCP.  Empty brackets may be
       used to explicitly designate an entire field, e.g.  vlan_tci[]
       for the entire 16-bit VLAN TCI header.  Before Open vSwitch 2.7,
       brackets were required in field specifications.

       See ovs-fields(7) for a list of fields and their names.

   Port Specifications
       Many Open vSwitch actions refer to OpenFlow ports.  In such
       cases, the port may be specified as a numeric port number in the
       range 0 to 65,535, although Open vSwitch only assigns port
       numbers in the range 1 through 62,279 to ports.  OpenFlow 1.1 and
       later use 32-bit port numbers, but Open vSwitch never assigns a
       port number that requires more than 16 bits.

       In most contexts, the name of a port may also be used.  (The most
       obvious context where a port name may not be used is in an
       ovs-ofctl command along with the --no-names option.)  When a
       port’s name contains punctuation or could be ambiguous with other
       actions, the name may be enclosed in double quotes, with
       JSON-like string escapes supported (see [RFC 8259]).

       Open vSwitch also supports the following standard OpenFlow port
       names (even in contexts where port names are not otherwise
       supported).  The corresponding OpenFlow 1.0 and 1.1+ port numbers
       are listed alongside them but should not be used in flow syntax:

          • in_port (65528 or 0xfff8; 0xfffffff8)

          • table (65529 or 0xfff9; 0xfffffff9)

          • normal (65530 or 0xfffa; 0xfffffffa)

          • flood (65531 or 0xfffb; 0xfffffffb)

          • all (65532 or 0xfffc; 0xfffffffc)

          • controller (65533 or 0xfffd; 0xfffffffd)

          • local (65534 or 0xfffe; 0xfffffffe)

          • any or none (65535 or 0xffff; 0xffffffff)

          • unset (not in OpenFlow 1.0; 0xfffffff7)

OUTPUT ACTIONS         top

       These actions send a packet to a physical port or a controller.
       A packet that never encounters an output action on its trip
       through the Open vSwitch pipeline is effectively dropped.
       Because actions are executed in order, a packet modification
       action that is not eventually followed by an output action will
       not have an externally visible effect.

   The output action
       Syntax:
              port
              output:port
              output:field
              output(port=port, max_len=nbytes)

       Outputs the packet to an OpenFlow port most commonly specified as
       port.  Alternatively, the output port may be read from field, a
       field or subfield in the syntax described under Field
       Specifications above.  Either way, if the port is the packet’s
       input port, the packet is not output.

       The port may be one of the following standard OpenFlow ports:

          local  Outputs the packet on the local port that corresponds
                 to the network device that has the same name as the
                 bridge, unless the packet was received on the local
                 port.  OpenFlow switch implementations are not required
                 to have a local port, but Open vSwitch bridges always
                 do.

          in_port
                 Outputs the packet on the port on which it was
                 received.  This is the only standard way to output the
                 packet to the input port (but see Output to the Input
                 port, below).

       The port may also be one of the following additional OpenFlow
       ports, unless max_len is specified:

          normal Subjects the packet to the device’s normal L2/L3
                 processing.  This action is not implemented by all
                 OpenFlow switches, and each switch implements it
                 differently.  The section The OVS Normal Pipeline below
                 documents the OVS implementation.

          flood  Outputs the packet on all switch physical ports, except
                 the port on which it was received and any ports on
                 which flooding is disabled.  Flooding can be disabled
                 automatically on a port by Open vSwitch when IEEE
                 802.1D spanning tree (STP) or rapid spanning tree
                 (RSTP) is enabled, or by a controller using an OpenFlow
                 OFPT_MOD_PORT request to set the port’s OFPPC_NO_FLOOD
                 flag (ovs-ofctl mod-port provides a command-line
                 interface to set this flag).

          all    Outputs the packet on all switch physical ports except
                 the port on which it was received.

          controller
                 Sends the packet and its metadata to an OpenFlow
                 controller or controllers encapsulated in an OpenFlow
                 packet-in message.  The separate controller action,
                 described below, provides more options for output to a
                 controller.

       Open vSwitch rejects output to other standard OpenFlow ports,
       including none, unset, and port numbers reserved for future use
       as standard ports, with the error OFPBAC_BAD_OUT_PORT.

       With max_len, the packet is truncated to at most nbytes bytes
       before being output.  In this case, the output port may not be a
       patch port.  Truncation is just for the single output action, so
       that later actions in the OpenFlow pipeline work with the
       complete packet.  The truncation feature is meant for use in
       monitoring applications, e.g. for mirroring packets to a
       collector.

       When an output action specifies the number of a port that does
       not currently exist (and is not in the range for standard ports),
       the OpenFlow specification allows but does not require OVS to
       reject the action.  All versions of Open vSwitch treat such an
       action as a no-op.  If a port with the number is created later,
       then the action will be honored at that point.  (OpenFlow
       requires OVS to reject output to a port number that will never be
       valid, with OFPBAC_BAD_OUT_PORT, but this situation does not
       arise when OVS is a software switch, since the user can add or
       renumber ports at any time.)

       A controller can suppress output to a port by setting its
       OFPPC_NO_FORWARD flag using an OpenFlow OFPT_MOD_PORT request
       (ovs-ofctl mod-port provides a command-line interface to set this
       flag).  When output is disabled, output actions (and other
       actions that output to the port) are allowed but have no effect.

       Open vSwitch allows output to a port that does not exist,
       although OpenFlow allows switches to reject such actions.

       Conformance
              All versions of OpenFlow and Open vSwitch support output
              to a literal port.  Output to a register is an OpenFlow
              extension introduced in Open vSwitch 1.3.  Output with
              truncation is an OpenFlow extension introduced in Open
              vSwitch 2.6.

   Output to the Input Port
       OpenFlow requires a switch to ignore attempts to send a packet
       out its ingress port in the most straightforward way.  For
       example, output:234 has no effect if the packet has ingress port
       234.  The rationale is that dropping these packets makes it
       harder to loop the network.  Sometimes this behavior can even be
       convenient, e.g. it is often the desired behavior in a flow that
       forwards a packet to several ports (floods the packet).

       Sometimes one really needs to send a packet out its ingress port
       (hairpin).  In this case, use in_port to explicitly output the
       packet to its input port, e.g.:

          $ ovs-ofctl add-flow br0 in_port=2,actions=in_port

       This also works in some circumstances where the flow doesn’t
       match on the input port.  For example, if you know that your
       switch has five ports numbered 2 through 6, then the following
       will send every received packet out every port, even its ingress
       port:

          $ ovs-ofctl add-flow br0 actions=2,3,4,5,6,in_port

       or, equivalently:

          $ ovs-ofctl add-flow br0 actions=all,in_port

       Sometimes, in complicated flow tables with multiple levels of
       resubmit actions, a flow needs to output to a particular port
       that may or may not be the ingress port.  It’s difficult to take
       advantage of output to in_port in this situation.  To help, Open
       vSwitch provides, as an OpenFlow extension, the ability to modify
       the in_port field.  Whatever value is currently in the in_port
       field is both the port to which output will be dropped and the
       destination for in_port.  This means that the following adds
       flows that reliably output to port 2 or to ports 2 through 6,
       respectively:

          $ ovs-ofctl add-flow br0 "in_port=2,actions=load:0->in_port,2"
          $ ovs-ofctl add-flow br0 "actions=load:0->in_port,2,3,4,5,6"

       If in_port is important for matching or other reasons, one may
       save and restore it on the stack:

          $ ovs-ofctl add-flow br0 \
                actions="push:in_port,load:0->in_port,2,3,4,5,6,pop:in_port"

   The OVS Normal Pipeline
       This section documents how Open vSwitch implements output to the
       normal port.  The OpenFlow specification places no requirements
       on how this port works, so all of this documentation is specific
       to Open vSwitch.

       Open vSwitch uses the Open_vSwitch database, detailed in
       ovs-vswitchd.conf.db(5), to determine the details of the normal
       pipeline.

       The normal pipeline executes the following ingress stages for
       each packet.  Each stage either accepts the packet, in which case
       the packet goes on to the next stage, or drops the packet, which
       terminates the pipeline.  The result of the ingress stages is a
       set of output ports, which is the empty set if some ingress stage
       drops the packet:

       1.  Input port lookup: Looks up the OpenFlow in_port field’s
           value to the corresponding Port and Interface record in the
           database.

           The in_port is normally the OpenFlow port that the packet was
           received on.  If set_field or another actions changes the
           in_port, the updated value is honored.  Accept the packet if
           the lookup succeeds, which it normally will.  If the lookup
           fails, for example because in_port was changed to an unknown
           value, drop the packet.

       2.  Drop malformed packet: If the packet is malformed enough that
           it contains only part of an 802.1Q header, then drop the
           packet with an error.

       3.  Drop packets sent to a port reserved for mirroring: If the
           packet was received on a port that is configured as the
           output port for a mirror (that is, it is the output_port in
           some Mirror record), then drop the packet.

       4.  VLAN input processing: This stage determines what VLAN the
           packet is in.  It also verifies that this VLAN is valid for
           the port; if not, drop the packet.  How the VLAN is
           determined and which ones are valid vary based on the
           vlan-mode in the input port’s Port record:

              trunk  The packet is in the VLAN specified in its 802.1Q
                     header, or in VLAN 0 if there is no 802.1Q header.
                     The trunks column in the Port record lists the
                     valid VLANs; if it is empty, all VLANs are valid.

              access The packet is in the VLAN specified in the tag
                     column of its Port record.  The packet must not
                     have an 802.1Q header with a nonzero VLAN ID; if it
                     does, drop the packet.

              native-tagged / native-untagged
                     Same as trunk except that the VLAN of a packet
                     without an 802.1Q header is not necessarily zero;
                     instead, it is taken from the tag column.

              dot1q-tunnel
                     The packet is in the VLAN specified in the tag
                     column of its Port record, which is a QinQ service
                     VLAN with the Ethertype specified by the Port’s
                     other_config:qinq-ethtype.  If the packet has an
                     802.1Q header, then it specifies the customer VLAN.
                     The cvlans column specifies the valid customer
                     VLANs; if it is empty, all customer VLANs are
                     valid.

       5.  Drop reserved multicast addresses: If the packet is addressed
           to a reserved Ethernet multicast address and the Bridge
           record does not have other_config:forward-bpdu set to true,
           drop the packet.

       6.  LACP bond admissibility: This step applies only if the input
           port is a member of a bond (a Port with more than one
           Interface) and that bond is configured to use LACP.
           Otherwise, skip to the next step.

           The behavior here depends on the state of LACP negotiation:

              • If LACP has been negotiated with the peer, accept the
                packet if the bond member is enabled (i.e. carrier is up
                and it hasn’t been administratively disabled).
                Otherwise, drop the packet.

              • If LACP negotiation is incomplete, then drop the packet.
                There is one exception: if fallback to active-backup
                mode is enabled, continue with the next step, pretending
                that the active-backup balancing mode is in use.

       7.  Non-LACP bond admissibility: This step applies if the input
           port is a member of a bond without LACP configured, or if a
           LACP bond falls back to active-backup as described in the
           previous step.  If neither of these applies, skip to the next
           step.

           If the packet is an Ethernet multicast or broadcast, and not
           received on the bond’s active member, drop the packet.

           The remaining behavior depends on the bond’s balancing mode:

              L4 (aka TCP balancing)
                     Drop the packet (this balancing mode is only
                     supported with LACP).

              Active-backup
                     Accept the packet only if it was received on the
                     active member.

              SLB (Source Load Balancing)
                     Drop the packet if the bridge has not learned the
                     packet’s source address (in its VLAN) on the port
                     that received it.  Otherwise, accept the packet
                     unless it is a gratuitous ARP.  Otherwise, accept
                     the packet if the MAC entry we found is ARP-locked.
                     Otherwise, drop the packet.  (See the SLB Bonding
                     section in the OVS bonding document for more
                     information and a rationale.)

       8.  Learn source MAC: If the source Ethernet address is not a
           multicast address, then insert a mapping from packet’s source
           Ethernet address and VLAN to the input port in the bridge’s
           MAC learning table.  (This is skipped if the packet’s VLAN is
           listed in the switch’s Bridge record in the flood_vlans
           column, since there is no use for MAC learning when all
           packets are flooded.)

           When learning happens on a non-bond port, if the packet is a
           gratuitous ARP, the entry is marked as ARP-locked.  The lock
           expires after 5 seconds.  (See the SLB Bonding section in the
           OVS bonding document for more information and a rationale.)

       9.  IP multicast path: If multicast snooping is enabled on the
           bridge, and the packet is an Ethernet multicast but not an
           Ethernet broadcast, and the packet is an IP packet, then the
           packet takes a special processing path.  This path is not yet
           documented here.

       10. Output port set: Search the MAC learning table for the port
           corresponding to the packet’s Ethernet destination and VLAN.
           If the search finds an entry, the output port set is just the
           learned port.  Otherwise (including the case where the packet
           is an Ethernet multicast or in flood_vlans), the output port
           set is all of the ports in the bridge that belong to the
           packet’s VLAN, except for any ports that were disabled for
           flooding via OpenFlow or that are configured in a Mirror
           record as a mirror destination port.

       The following egress stages execute once for each element in the
       set of output ports.  They execute (conceptually) in parallel, so
       that a decision or action taken for a given output port has no
       effect on those for another one:

       1. Drop loopback: If the output port is the same as the input
          port, drop the packet.

       2. VLAN output processing: This stage adjusts the packet to
          represent the VLAN in the correct way for the output port.
          Its behavior varies based on the vlan-mode in the output
          port’s Port record:

             trunk / native-tagged / native-untagged
                    If the packet is in VLAN 0 (for native-untagged, if
                    the packet is in the native VLAN) drops any 802.1Q
                    header.  Otherwise, ensures that there is an 802.1Q
                    header designating the VLAN.

             access Remove any 802.1Q header that was present.

             dot1q-tunnel
                    Ensures that the packet has an outer 802.1Q header
                    with the QinQ Ethertype and the specified configured
                    tag, and an inner 802.1Q header with the packet’s
                    VLAN.

       3. VLAN priority tag processing: If VLAN output processing
          discarded the 802.1Q headers, but priority tags are enabled
          with other_config:priority-tags in the output port’s Port
          record, then a priority-only tag is added (perhaps only if the
          priority would be nonzero, depending on the configuration).

       4. Bond member choice: If the output port is a bond, the code
          chooses a particular member.  This step is skipped for
          non-bonded ports.

          If the bond is configured to use LACP, but LACP negotiation is
          incomplete, then normally the packet is dropped.  The
          exception is that if fallback to active-backup mode is
          enabled, the egress pipeline continues choosing a bond member
          as if active-backup mode was in use.

          For active-backup mode, the output member is the active
          member.  Other modes hash appropriate header fields and use
          the hash value to choose one of the enabled members.

       5. Output: The pipeline sends the packet to the output port.

   The controller action
       Syntax:
              controller
              controller:max_len
              controller(key[=value], ...)

       Sends the packet and its metadata to an OpenFlow controller or
       controllers encapsulated in an OpenFlow packet-in message.  The
       supported options are:

          max_len=max_len
                 Limit to max_len the number of bytes of the packet to
                 send in the packet-in.  A max_len of 0 prevents any of
                 the packet from being sent (thus, only metadata is
                 included).  By default, the entire packet is sent,
                 equivalent to a max_len of 65535.  This option has no
                 effect in Open vSwith 2.7 and later: the entire packet
                 will always be sent.

          reason=reason
                 Specify reason as the reason for sending the message in
                 the packet-in.  The supported reasons are no_match,
                 action, invalid_ttl, action_set, group, and packet_out.
                 The default reason is action.

          id=controller_id
                 Specify controller_id, a 16-bit integer, as the
                 connection ID of the OpenFlow controller or controllers
                 to which the packet-in message should be sent.  The
                 default is zero.  Zero is also the default connection
                 ID for each controller connection, and a given
                 controller connection will only have a nonzero
                 connection ID if its controller uses the
                 NXT_SET_CONTROLLER_ID Open vSwitch extension to
                 OpenFlow.

          userdata=hh...
                 Supplies the bytes represented as hex digits hh as
                 additional data to the controller in the packet-in
                 message.  Pairs of hex digits may be separated by
                 periods for readability.

          pause  Causes the switch to freeze the packet’s trip through
                 Open vSwitch flow tables and serializes that state into
                 the packet-in message as a continuation, an additional
                 property in the NXT_PACKET_IN2 message.  The controller
                 can later send the continuation back to the switch in
                 an NXT_RESUME message, which will restart the packet’s
                 traversal from the point where it was interrupted.
                 This permits an OpenFlow controller to interpose on a
                 packet midway through processing in Open vSwitch.

       Conformance
              All versions of OpenFlow and Open vSwitch support
              controller action and its max_len option.  The userdata
              and pause options require the Open vSwitch
              NXAST_CONTROLLER2 extension action added in Open vSwitch
              2.6. In the absence of these options, the reason (other
              than reason=action) and controller_id (option than
              controller_id=0) options require the Open vSwitch
              NXAST_CONTROLLER extension action added in Open vSwitch
              1.6.

              Open vSwitch 2.7 and later is configured to not buffer
              packets for the packet-in event.  As a result, the full
              packet is always sent to controllers.  This means that the
              max_len option has no effect on the controller action, and
              all values (even 0) are equivalent to the default value of
              65535.

   The enqueue action
       Syntax:
              enqueue(port,queue)
              enqueue:port:queue

       Enqueues the packet on the specified queue within port port.

       port must be an OpenFlow port number or name as described under
       Port Specifications above.  port may be in_port or local but the
       other standard OpenFlow ports are not allowed.

       queue must be a number between 0 and 4294967294 (0xfffffffe),
       inclusive.  The number of actually supported queues depends on
       the switch.  Some OpenFlow implementations do not support queuing
       at all.  In Open vSwitch, the supported queues vary depending on
       the operating system, datapath, and hardware in use.  Use the QoS
       and Queue tables in the Open vSwitch database to configure
       queuing on individual OpenFlow ports (see ovs-vswitchd.conf.db(5)
       for more information).

       Conformance
              Only OpenFlow 1.0 supports enqueue.  OpenFlow 1.1 added
              the set_queue action to use in its place along with
              output.

              Open vSwitch translates enqueue to a sequence of three
              actions in OpenFlow 1.1 or later:
              set_queue:queue,output:port,pop_queue.  This is equivalent
              in behavior as long as the flow table does not otherwise
              use set_queue, but it relies on the pop_queue Open vSwitch
              extension action.

   The bundle and bundle_load actions
       Syntax:
              bundle(fields,basis,algorithm,ofport,members:port...)
              bundle_load(fields,basis,algorithm,ofport,dst,members:port...)

       These actions choose a port (a member) from a comma-separated
       OpenFlow port list.  After selecting the port, bundle outputs to
       it, whereas bundle_load writes its port number to dst, which must
       be a 16-bit or wider field or subfield in the syntax described
       under Field Specifications above.

       These actions hash a set of fields using basis as a universal
       hash parameter, then apply the bundle link selection algorithm to
       choose a port.

       fields must be one of the following.  For the options with
       symmetric in the name, reversing source and destination addresses
       yields the same hash:

          eth_src
                 Ethernet source address.

          nw_src IPv4 or IPv6 source address.

          nw_dst IPv4 or IPv6 destination address.

          symmetric_l4
                 Ethernet source and destination, Ethernet type, VLAN ID
                 or IDs (if any), IPv4 or IPv6 source and destination,
                 IP protocol, TCP or SCTP (but not UDP) source and
                 destination.

          symmetric_l3l4
                 IPv4 or IPv6 source and destination, IP protocol, TCP
                 or SCTP (but not UDP) source and destination.

          symmetric_l3l4+udp
                 Like symmetric_l3l4 but include UDP ports.

       algorithm must be one of the following:

          active_backup
                 Chooses the first live port listed in members.

          hrw (Highest Random Weight)
                 Computes the following, considering only the live ports
                 in members:

                     for i in [1, n_members]:
                         weights[i] = hash(flow, i)
                     member = { i such that weights[i] >= weights[j] for all j != i }

                 This algorithm is specified by RFC 2992.

       The algorithms take port liveness into account when selecting
       members.  The definition of whether a port is live is subject to
       change.  It currently takes into account carrier status and link
       monitoring protocols such as BFD and CFM.  If none of the members
       is live, bundle does not output the packet and bundle_load stores
       OFPP_NONE (65535) in the output field.

       Example: bundle(eth_src,0,hrw,ofport,members:4,8) uses an
       Ethernet source hash with basis 0, to select between OpenFlow
       ports 4 and 8 using the Highest Random Weight algorithm.

       Conformance
              Open vSwitch 1.2 introduced the bundle and bundle_load
              OpenFlow extension actions.

   The group action
       Syntax:
              group:group

       Outputs the packet to the OpenFlow group group, which must be a
       number in the range 0 to 4294967040 (0xffffff00).  The group must
       exist or Open vSwitch will refuse to add the flow.  When a group
       is deleted, Open vSwitch also deletes all of the flows that
       output to it.

       Groups contain action sets, whose semantics are described above
       in the section Action Sets.  The semantics of action sets can be
       surprising to users who expect action list semantics, since
       action sets reorder and sometimes ignore actions.

       A group action usually executes the action set or sets in one or
       more group buckets.  Open vSwitch saves the packet and metadata
       before it executes each bucket, and then restores it afterward.
       Thus, when a group executes more than one bucket, this means that
       each bucket executes on the same packet and metadata.  Moreover,
       regardless of the number of buckets executed, the packet and
       metadata are the same before and after executing the group.

       Sometimes saving and restoring the packet and metadata can be
       undesirable.  In these situations, workarounds are possible.  For
       example, consider a pipeline design in which a select group
       bucket is to communicate to a later stage of processing a value
       based on which bucket was selected.  An obvious design would be
       for the bucket to communicate the value via set_field on a
       register.  This does not work because registers are part of the
       metadata that group saves and restores.  The following
       alternative bucket designs do work:

          • Recursively invoke the rest of the pipeline with resubmit.

          • Use resubmit into a table that uses push to put the value on
            the stack for the caller to pop off.  This works because
            group preserves only packet data and metadata, not the
            stack.

            (This design requires indirection through resubmit because
            actions sets may not contain push or pop actions.)

       An exit action within a group bucket terminates only execution of
       that bucket, not other buckets or the overall pipeline.

       Conformance
              OpenFlow 1.1 introduced group.  Open vSwitch 2.6 and later
              also supports group as an extension to OpenFlow 1.0.

ENCAPSULATION AND DECAPSULATION ACTIONS         top

   The strip_vlan and pop actions
       Syntax:
              strip_vlan
              pop_vlan

       Removes the outermost VLAN tag, if any, from the packet.

       The two names for this action are synonyms with no semantic
       difference.  The OpenFlow 1.0 specification uses the name
       strip_vlan and later versions use pop_vlan, but OVS accepts
       either name regardless of version.

       In OpenFlow 1.1 and later, consistency rules allow strip_vlan
       only in a flow that matches only packets with a VLAN tag (or
       following an action that pushes a VLAN tag, such as push_vlan).
       See Inconsistencies, above, for more information.

       Conformance
              All versions of OpenFlow and Open vSwitch support this
              action.

   The push_vlan action
       Syntax:
              push_vlan:ethertype

       Pushes a new outermost VLAN onto the packet.  Uses TPID
       ethertype, which must be 0x8100 for an 802.1Q C-tag or 0x88a8 for
       a 802.1ad S-tag.

       Conformance
              OpenFlow 1.1 and later supports this action.  Open vSwitch
              2.8 added support for multiple VLAN tags (with a limit of
              2) and 802.1ad S-tags.

   The push_mpls action
       Syntax:
              push_mpls:ethertype

       Pushes a new outermost MPLS label stack entry (LSE) onto the
       packet and changes the packet’s Ethertype to ethertype, which
       must be either B0x8847 or 0x8848.  If the packet did not already
       contain any MPLS labels, initializes the new LSE as:

          Label  2, if the packet contains IPv6, 0 otherwise.

          TC     The low 3 bits of the packet’s DSCP value, or 0 if the
                 packet is not IP.

          TTL    Copied from the IP TTL, or 64 if the packet is not IP.

       If the packet did already contain an MPLS label, initializes the
       new outermost label as a copy of the existing outermost label.

       OVS currently supports at most 3 MPLS labels.

       This action applies only to Ethernet packets.

       Conformance
              Open vSwitch 1.11 introduced support for MPLS.  OpenFlow
              1.1 and later support push_mpls.  Open vSwitch implements
              push_mpls as an extension to OpenFlow 1.0.

   The pop_mpls action
       Syntax:
              pop_mpls:ethertype

       Strips the outermost MPLS label stack entry and changes the
       packet’s Ethertype to ethertype.  This action applies only to
       Ethernet packets with at least one MPLS label.  If there is more
       than one MPLS label, then ethertype should be an MPLS Ethertype
       (B0x8847 or 0x8848).

       Conformance
              Open vSwitch 1.11 introduced support for MPLS.  OpenFlow
              1.1 and later support pop_mpls.  Open vSwitch implements
              pop_mpls as an extension to OpenFlow 1.0.

   The encap action
       Syntax:
              encap(nsh([md_type=md_type], [tlv(class,type,value)]...))
              encap(ethernet)
              encap(mpls)
              encap(mpls_mc)

       The encap action encapsulates a packet with a specified header.
       It has variants for different kinds of encapsulation.

       The encap(nsh(...)) variant encapsulates an Ethernet frame with
       NSH.  The md_type may be 1 or 2 for metadata type 1 or 2,
       defaulting to 1.  For metadata type 2, TLVs may be specified with
       class as a 16-bit hexadecimal integer beginning with 0x, type as
       an 8-bit decimal integer, and value a sequence of pairs of hex
       digits beginning with 0x.  For example:

          encap(nsh(md_type=1))
                 Encapsulates the packet with an NSH header with
                 metadata type 1.

          encap(nsh(md_type=2,tlv(0x1000,10,0x12345678)))
                 Encapsulates the packet with an NSH header, NSH
                 metadata type 2, and an NSH TLV with class 0x1000, type
                 10, and the 4-byte value 0x12345678.

       The encap(ethernet) variant encapsulate a bare L3 packet in an
       Ethernet frame.  The Ethernet type is initialized to the L3
       packet’s type, e.g. 0x0800 if the L3 packet is IPv4.  The
       Ethernet source and destination are initially zeroed.

       The encap(mpls) variant adds a MPLS header at the start of the
       packet.  When encap(ethernet) is applied after this action, the
       ethertype of ethernet header will be populated with MPLS unicast
       ethertype (0x8847).

       The encap(mpls_mc) variant adds a MPLS header at the start of the
       packet.  When encap(ethernet) is applied after this action, the
       ethertype of ethernet header will be populated with MPLS
       multicast ethertype (0x8848).

       Conformance
              This action is an Open vSwitch extension to OpenFlow 1.3
              and later, introduced in Open vSwitch 2.8.

              The MPLS support for this action is added in Open vSwitch
              2.17.

   The decap action
       Syntax:
              decap
              decap(packet_type(ns=namespace,type=type))

       Removes an outermost encapsulation from the packet:

          • If the packet is an Ethernet packet, removes the Ethernet
            header, which changes the packet into a bare L3 packet.  If
            the packet has VLAN tags, raises an unsupported packet type
            error (see Error Handling, above).

          • Otherwise, if the packet is an NSH packet, removes the NSH
            header, revealing the inner packet.  Open vSwitch supports
            Ethernet, IPv4, IPv6, and NSH inner packet types.  Other
            types raise unsupported packet type errors.

          • Otherwise, if the packet is encapsulated inside a MPLS
            header, removes the MPLS header and classifies the inner
            packet as mentioned in the packet type argument of the
            decap.  The packet_type field specifies the type of the
            packet in the format specified in OpenFlow 1.5 chapter
            7.2.3.11 Packet Type Match Field.  The inner packet will be
            incorrectly classified, if the inner packet is different
            from mentioned in the packet_type field.

          • Otherwise, raises an unsupported packet type error.

       Conformance
              This action is an Open vSwitch extension to OpenFlow 1.3
              and later, introduced in Open vSwitch 2.8.

              The MPLS support for this action is added in Open vSwitch
              2.17.

FIELD MODIFICATION ACTIONS         top

       These actions modify packet data and metadata fields.

   The set_field and load actions
       Syntax:
              set_field:value[/mask]->dst
              load:value->dst

       These actions loads a literal value into a field or part of a
       field.  The set_field action takes value in the customary syntax
       for field dst, e.g. 00:11:22:33:44:55 for an Ethernet address,
       and dst as the field’s name.  The optional mask allows part of a
       field to be set.

       The load action takes value as an integer value (in decimal or
       prefixed by 0x for hexadecimal) and dst as a field or subfield in
       the syntax described under Field Specifications above.

       The following all set the Ethernet source address to
       00:11:22:33:44:55:

          • set_field:00:11:22:33:44:55->eth_srcload:0x001122334455->eth_srcload:0x001122334455->OXM_OF_ETH_SRC[]

       The following all set the multicast bit in the Ethernet
       destination address:

          • set_field:01:00:00:00:00:00/01:00:00:00:00:00->eth_dstload:1->eth_dst[40]

       Open vSwitch prohibits a set_field or load action whose dst is
       not guaranteed to be part of the packet; for example, set_field
       of nw_dst is only allowed in a flow that matches on Ethernet type
       0x800.  In some cases, such as in an action set, Open vSwitch
       can’t statically check that dst is part of the packet, and in
       that case if it is not then Open vSwitch treats the action as a
       no-op.

       Conformance
              Open vSwitch 1.1 introduced NXAST_REG_LOAD as a extension
              to OpenFlow 1.0 and used load to express it.  Later,
              OpenFlow 1.2 introduced a standard OFPAT_SET_FIELD action
              that was restricted to loading entire fields, so Open
              vSwitch added the form set_field with this restriction.
              OpenFlow 1.5 extended OFPAT_SET_FIELD to the point that it
              became a superset of NXAST_REG_LOAD.  Open vSwitch
              translates either syntax as necessary for the OpenFlow
              version in use: in OpenFlow 1.0 and 1.1, NXAST_REG_LOAD;
              in OpenFlow 1.2, 1.3, and 1.4, NXAST_REG_LOAD for load or
              for loading a subfield, OFPAT_SET_FIELD otherwise; and
              OpenFlow 1.5 and later, OFPAT_SET_FIELD.

   The move action
       Syntax:
              move:src->dst

       Copies the named bits from field or subfield src to field or
       subfield dst.  src and dst should fields or subfields in the
       syntax described under Field Specifications above.  The two
       fields or subfields must have the same width.

       Examples:

          • move:reg0[0..5]->reg1[26..31] copies the six bits numbered 0
            through 5 in register 0 into bits 26 through 31 of register
            1.

          • move:reg0[0..15]->vlan_tci copies the least significant 16
            bits of register 0 into the VLAN TCI field.

       Conformance
              In OpenFlow 1.0 through 1.4, move ordinarily uses an Open
              vSwitch extension to OpenFlow.  In OpenFlow 1.5, move uses
              the OpenFlow 1.5 standard OFPAT_COPY_FIELD action.  The
              ONF has also made OFPAT_COPY_FIELD available as an
              extension to OpenFlow 1.3.  Open vSwitch 2.4 and later
              understands this extension and uses it if a controller
              uses it, but for backward compatibility with older
              versions of Open vSwitch, ovs-ofctl does not use it.

   The mod_dl_src and mod_dl_dst actions
       Syntax:
              mod_dl_src:mac
              mod_dl_dst:mac

       Sets the Ethernet source or destination address, respectively, to
       mac, which should be expressed in the form xx:xx:xx:xx:xx:xx.

       For L3-only packets, that is, those that lack an Ethernet header,
       this action has no effect.

       Conformance
              OpenFlow 1.0 and 1.1 have specialized actions for these
              purposes.  OpenFlow 1.2 and later do not, so Open vSwitch
              translates them to appropriate OFPAT_SET_FIELD actions for
              those versions,

   The mod_nw_src and mod_nw_dst actions
       Syntax:
              mod_nw_src:ip
              mod_nw_dst:ip

       Sets the IPv4 source or destination address, respectively, to ip,
       which should be expressed in the form w.x.y.z.

       In OpenFlow 1.1 and later, consistency rules allow these actions
       only in a flow that matches only packets that contain an IPv4
       header (or following an action that adds an IPv4 header, e.g.
       pop_mpls:0x0800).  See Inconsistencies, above, for more
       information.

       Conformance
              OpenFlow 1.0 and 1.1 have specialized actions for these
              purposes.  OpenFlow 1.2 and later do not, so Open vSwitch
              translates them to appropriate OFPAT_SET_FIELD actions for
              those versions,

   The mod_nw_tos and mod_nw_ecn actions
       Syntax:
              mod_nw_tos:tos
              mod_nw_ecn:ecn

       The mod_nw_tos action sets the DSCP bits in the IPv4 ToS/DSCP or
       IPv6 traffic class field to tos, which must be a multiple of 4
       between 0 and 255.  This action does not modify the two least
       significant bits of the ToS field (the ECN bits).

       The mod_nw_ecn action sets the ECN bits in the IPv4 ToS or IPv6
       traffic class field to ecn, which must be a value between 0 and
       3, inclusive.  This action does not modify the six most
       significant bits of the field (the DSCP bits).

       In OpenFlow 1.1 and later, consistency rules allow these actions
       only in a flow that matches only packets that contain an IPv4 or
       IPv6 header (or following an action that adds such a header).
       See Inconsistencies, above, for more information.

       Conformance
              OpenFlow 1.0 has a mod_nw_tos action but not mod_nw_ecn.
              Open vSwitch implements the latter in OpenFlow 1.0 as an
              extension using NXAST_REG_LOAD.  OpenFlow 1.1 has
              specialized actions for these purposes.  OpenFlow 1.2 and
              later do not, so Open vSwitch translates them to
              appropriate OFPAT_SET_FIELD actions for those versions.

   The mod_tp_src and mod_tp_dst actions
       Syntax:
              mod_tp_src:port
              mod_tp_dst:port

       Sets the TCP or UDP or SCTP source or destination port,
       respectively, to port.  Both IPv4 and IPv6 are supported.

       In OpenFlow 1.1 and later, consistency rules allow these actions
       only in a flow that matches only packets that contain a TCP or
       UDP or SCTP header.  See Inconsistencies, above, for more
       information.

       Conformance
              OpenFlow 1.0 and 1.1 have specialized actions for these
              purposes.  OpenFlow 1.2 and later do not, so Open vSwitch
              translates them to appropriate OFPAT_SET_FIELD actions for
              those versions,

   The dec_ttl action
       Syntax:
              dec_ttl
              dec_ttl(id1[,id2[, ...]])

       Decrement TTL of IPv4 packet or hop limit of IPv6 packet.  If the
       TTL or hop limit is initially 0 or 1, no decrement occurs, as
       packets reaching TTL zero must be rejected.  Instead, Open
       vSwitch sends a packet-in message with reason code
       OFPR_INVALID_TTL to each connected controller that has enabled
       receiving such messages, and stops processing the current set of
       actions.  (However, if the current set of actions was reached
       through resubmit, the remaining actions in outer levels resume
       processing.)

       As an Open vSwitch extension to OpenFlow, this action supports
       the ability to specify a list of controller IDs.  Open vSwitch
       will only send the message to controllers with the given ID or
       IDs.  Specifying no list is equivalent to specifying a single
       controller ID of zero.

       In OpenFlow 1.1 and later, consistency rules allow these actions
       only in a flow that matches only packets that contain an IPv4 or
       IPv6 header.  See Inconsistencies, above, for more information.

       Conformance
              All versions of OpenFlow and Open vSwitch support this
              action.

   The set_mpls_label, set_mpls_tc, and set_mpls_ttl actions
       Syntax:
              set_mpls_label:label
              set_mpls_tc:tc
              set_mpls_ttl:ttl

       The set_mpls_label action sets the label of the packet’s outer
       MPLS label stack entry.  label should be a 20-bit value that is
       decimal by default; use a 0x prefix to specify the value in
       hexadecimal.

       The set_mpls_tc action sets the traffic class of the packet’s
       outer MPLS label stack entry.  tc should be in the range 0 to 7,
       inclusive.

       The set_mpls_ttl action sets the TTL of the packet’s outer MPLS
       label stack entry.  ttl should be in the range 0 to 255
       inclusive.  In OpenFlow 1.1 and later, consistency rules allow
       these actions only in a flow that matches only packets that
       contain an MPLS label (or following an action that adds an MPLS
       label, e.g. push_mpls:0x8847).  See Inconsistencies, above, for
       more information.

       Conformance
              OpenFlow 1.0 does not support MPLS, but Open vSwitch
              implements these actions as extensions.  OpenFlow 1.1 has
              specialized actions for these purposes.  OpenFlow 1.2 and
              later do not, so Open vSwitch translates them to
              appropriate OFPAT_SET_FIELD actions for those versions,

   The dec_mpls_ttl and dec_nsh_ttl actions
       Syntax:
              dec_mpls_ttl
              dec_nsh_ttl

       These actions decrement the TTL of the packet’s outer MPLS label
       stack entry or its NSH header, respectively.  If the TTL is
       initially 0 or 1, no decrement occurs.  Instead, Open vSwitch
       sends a packet-in message with reason code BOFPR_INVALID_TTL to
       OpenFlow controllers with ID 0, if it has enabled receiving them.
       Processing the current set of actions then stops.  (However, if
       the current set of actions was reached through resubmit,
       remaining actions in outer levels resume processing.)

       In OpenFlow 1.1 and later, consistency rules allow this actions
       only in a flow that matches only packets that contain an MPLS
       label or an NSH header, respectively.  See Inconsistencies,
       above, for more information.

       Conformance
              Open vSwitch 1.11 introduced support for MPLS.  OpenFlow
              1.1 and later support dec_mpls_ttl.  Open vSwitch
              implements dec_mpls_ttl as an extension to OpenFlow 1.0.

              Open vSwitch 2.8 introduced support for NSH, although the
              NSH draft changed after release so that only Open vSwitch
              2.9 and later conform to the final protocol specification.
              The dec_nsh_ttl action and NSH support in general is an
              Open vSwitch extension not supported by any version of
              OpenFlow.

   The check_pkt_larger action
       Syntax:
              check_pkt_larger(pkt_len)->dst

       Checks if the packet is larger than the specified length in
       pkt_len.  If so, stores 1 in dst, which should be a 1-bit field;
       if not, stores 0.

       The packet length to check against the argument pkt_len includes
       the L2 header and L2 payload of the packet, but not the VLAN tag
       (if present).

       Examples:

          • check_pkt_larger(1500)->reg0[0]check_pkt_larger(8000)->reg9[10]

       This action was added in Open vSwitch 2.12.

   The delete_field action
       Syntax:
              delete_field:field

       The delete_field action deletes a field in the syntax described
       under Field Specifications above.  Currently, only the
       tun_metadata fields are supported.

       This action was added in Open vSwitch 2.14.

METADATA ACTIONS         top

   The set_tunnel action
       Syntax:
              set_tunnel:id
              set_tunnel64:id

       Many kinds of tunnels support a tunnel ID, e.g. VXLAN and Geneve
       have a 24-bit VNI, and GRE has an optional 32-bit key.  This
       action sets the value used for tunnel ID in such tunneled
       packets, although whether it is used for a particular tunnel
       depends on the tunnel’s configuration.  See the tunnel ID
       documentation in ovs-fields(7) for more information.

       Conformance
              These actions are OpenFlow extensions.  set_tunnel was
              introduced in Open vSwitch 1.0.  set_tunnel64, which is
              needed if id is wider than 32 bits, was added in Open
              vSwitch 1.1.  Both actions always set the entire tunnel ID
              field.  Open vSwitch supports these actions in all
              versions of OpenFlow, but in OpenFlow 1.2 and later it
              translates them to an appropriate standardized
              OFPAT_SET_FIELD action.

   The set_queue and pop_queue actions
       Syntax:
              set_queue:queue
              pop_queue

       The set_queue action sets the queue ID to be used for subsequent
       output actions to queue, which must be a 32-bit integer.  The
       range of meaningful values of queue, and their meanings, varies
       greatly from one OpenFlow implementation to another.  Even within
       a single implementation, there is no guarantee that all OpenFlow
       ports have the same queues configured or that all OpenFlow ports
       in an implementation can be configured the same way queue-wise.
       For more information, see the documentation for the output queue
       field in ovs-fields(7).

       The pop_queue restores the output queue to the default that was
       set when the packet entered the switch (generally 0).

       Four billion queues ought to be enough for anyone:
       https://mailman.stanford.edu/pipermail/openflow-spec/2009-August/000394.html 

       Conformance
              OpenFlow 1.1 introduced the set_queue action.  Open
              vSwitch also supports it as an extension in OpenFlow 1.0.

              The pop_queue action is an Open vSwitch extension.

FIREWALLING ACTIONS         top

       Open vSwitch is often used to implement a firewall.  The
       preferred way to implement a firewall is connection tracking,
       that is, to keep track of the connection state of individual TCP
       sessions.  The ct action described in this section, added in Open
       vSwitch 2.5, implements connection tracking.  For new
       deployments, it is the recommended way to implement firewalling
       with Open vSwitch.

       Before ct was added, Open vSwitch did not have built-in support
       for connection tracking.  Instead, Open vSwitch supported the
       learn action, which allows a received packet to add a flow to an
       OpenFlow flow table.  This could be used to implement a primitive
       form of connection tracking: packets passing through the firewall
       in one direction could create flows that allowed response packets
       back through the firewall in the other direction.  The additional
       fin_timeout action allowed the learned flows to expire quickly
       after TCP session termination.

   The ct action
       Syntax:
              ct([argument]...)
              ct(commit[,argument]...)

       The action has two modes of operation, distinguished by whether
       commit is present.  The following arguments may be present in
       either mode:

          zone=value
                 A zone is a 16-bit id that isolates connections into
                 separate domains, allowing overlapping network
                 addresses in different zones.  If a zone is not
                 provided, then the default is 0. The value may be
                 specified either as a 16-bit integer literal or a field
                 or subfield in the syntax described under Field
                 Specifications above.

       Without commit, this action sends the packet through the
       connection tracker.  The connection tracker keeps track of the
       state of TCP connections for packets passed through it.  For each
       packet through a connection, it checks that it satisfies TCP
       invariants and signals the connection state to later actions
       using the ct_state metadata field, which is documented in
       ovs-fields(7).

       In this form, ct forks the OpenFlow pipeline:

          • In one fork, ct passes the packet to the connection tracker.
            Afterward, it reinjects the packet into the OpenFlow
            pipeline with the connection tracking fields initialized.
            The ct_state field is initialized with connection state and
            ct_zone to the connection tracking zone specified on the
            zone argument.  If the connection is one that is already
            tracked, ct_mark and ct_label to its existing mark and
            label, respectively; otherwise they are zeroed.  In
            addition, ct_nw_proto, ct_nw_src, ct_nw_dst, ct_ipv6_src,
            ct_ipv6_dst, ct_tp_src, and ct_tp_dst are initialized
            appropriately for the original direction connection.  See
            the resubmit action for a way to search the flow table with
            the connection tracking original direction fields swapped
            with the packet 5-tuple fields.  See ovs-fields(7) for
            details on the connection tracking fields.

          • In the other fork, the original instance of the packet
            continues independent processing following the ct action.
            The ct_state field and other connection tracking metadata
            are cleared.

       Without commit, the ct action accepts the following arguments:

          table=table
                 Sets the OpenFlow table where the packet is reinjected.
                 The table must be a number between 0 and 254 inclusive,
                 or a table’s name.  If table is not specified, then the
                 packet is not reinjected.

          nat

          nat(type=addrs[:ports][,flag]...)
                 Specify address and port translation for the connection
                 being  tracked.  The type must be src, for source
                 address/port translation (SNAT), or dst, for
                 destination address/port translation (DNAT).  Setting
                 up address translation for a new connection takes
                 effect only if the connection is later committed with
                 ct(commit ...).

                 The src and dst options take the following arguments:

                     addrs  The IP address addr or range addr1-addr2
                            from which the translated address should be
                            selected.  If only one address is given,
                            then that address will always be selected,
                            otherwise the address selection can be
                            informed by the optional persistent flag as
                            described below.  Either IPv4 or IPv6
                            addresses can be provided, but both
                            addresses must be of the same type, and the
                            datapath behavior is undefined in case of
                            providing IPv4 address range for an IPv6
                            packet, or IPv6 address range for an IPv4
                            packet.  IPv6 addresses must be bracketed
                            with [ and ] if a port range is also given.

                     ports  The L4 port or range port1-port2 from which
                            the translated port should be selected. When
                            a port range is specified, fallback to
                            ephemeral ports does not happen, else, it
                            will.  The port number selection can be
                            informed by the optional random and hash
                            flags described below.

                 The optional flags are:

                     random The selection of the port from the given
                            range should be done using a fresh random
                            number.  This flag is mutually exclusive
                            with hash.

                     hash   The selection of the port from the given
                            range should be done using a datapath
                            specific hash of the packet’s IP addresses
                            and the other, non-mapped port number.  This
                            flag is mutually exclusive with random.

                     persistent
                            The selection of the IP address from the
                            given range should be done so that the same
                            mapping can be provided after the system
                            restarts.

                 If alg is specified for the committing ct action that
                 also includes nat with a src or dst attribute, then the
                 datapath tries to set up the helper to be NAT-aware.
                 This functionality is datapath specific and may not be
                 supported by all datapaths.

                 A bare nat argument with no options will only translate
                 the packet being processed in the way the connection
                 has been set up with an earlier, committed ct action.
                 A nat action with src or dst, when applied to a packet
                 belonging to an established (rather than new)
                 connection, will behave the same as a bare nat.

                 For SNAT, there is a special case when the src IP
                 address is configured as all 0’s, i.e.,
                 nat(src=0.0.0.0). In this case, when a source port
                 collision is detected during the commit, the source
                 port will be translated to an ephemeral port. If there
                 is no collision, no SNAT is performed.

                 Open vSwitch 2.6 introduced nat.  Linux 4.6 was the
                 earliest upstream kernel that implemented ct support
                 for nat.

       With commit, the connection tracker commits the connection to the
       connection tracking module.  The commit flag should only be used
       from the pipeline within the first fork of ct without commit.
       Information about the connection is stored beyond the lifetime of
       the packet in the pipeline.  Some ct_state flags are only
       available for committed connections.

       The following options are available only with commit:

          force  A committed connection always has the directionality of
                 the packet that caused the connection to be committed
                 in the first place.  This is the original direction of
                 the connection, and the opposite direction is the reply
                 direction.  If a connection is already committed, but
                 it is in the wrong direction, force effectively
                 terminates the existing connection and starts a new one
                 in the current direction.  This flag has no effect if
                 the original direction of the connection is already the
                 same as that of the current packet.

          exec(action...)
                 Perform each action within the context of connection
                 tracking.  Only actions which modify the ct_mark or
                 ct_label fields are accepted within exec action, and
                 these fields may only be modified with this option. For
                 example:

                 set_field:value[/mask]->ct_mark
                        Store a 32-bit metadata value with the
                        connection.  Subsequent lookups for packets in
                        this connection will populate ct_mark when the
                        packet is sent to the connection tracker with
                        the table specified.

                 set_field:value[/mask]->ct_label
                        Store a 128-bit metadata value with the
                        connection.  Subsequent lookups for packets in
                        this connection will populate ct_label when the
                        packet is sent to the connection tracker with
                        the table specified.

          alg=alg
                 Specify application layer gateway alg to track specific
                 connection types.  If subsequent related connections
                 are sent through the ct action, then the rel flag in
                 the ct_state field will be set.  Supported types
                 include:

                 ftp    Look for negotiation of FTP data connections.
                        Specify this option for FTP control connections
                        to detect related data connections and populate
                        the rel flag for the data connections.

                 tftp   Look for negotiation of TFTP data connections.
                        Specify this option for TFTP control connections
                        to detect related data connections and populate
                        the rel flag for the data connections.

                 Related connections inherit ct_mark from that stored
                 with the original connection (i.e. the connection
                 created by ct(alg=...).

       With the Linux datapath, global sysctl options affect ct
       behavior.  In particular, if net.netfilter.nf_conntrack_helper is
       enabled, which it is by default until Linux 4.7, then application
       layer gateway helpers may be executed even if alg is not
       specified.  For security reasons, the netfilter team recommends
       users disable this option.  For further details, please see
       http://www.netfilter.org/news.html#2012-04-03  .

       The ct action may be used as a primitive to construct stateful
       firewalls by selectively committing some traffic, then matching
       ct_state to allow established connections while denying new
       connections.  The following flows provide an example of how to
       implement a simple firewall that allows new connections from port
       1 to port 2, and only allows established connections to send
       traffic from port 2 to port 1:

          table=0,priority=1,action=drop
          table=0,priority=10,arp,action=normal
          table=0,priority=100,ip,ct_state=-trk,action=ct(table=1)
          table=1,in_port=1,ip,ct_state=+trk+new,action=ct(commit),2
          table=1,in_port=1,ip,ct_state=+trk+est,action=2
          table=1,in_port=2,ip,ct_state=+trk+new,action=drop
          table=1,in_port=2,ip,ct_state=+trk+est,action=1

       If ct is executed on IPv4 (or IPv6) fragments, then the message
       is implicitly reassembled before sending to the connection
       tracker and refragmented upon output, to the original maximum
       received fragment size.  Reassembly occurs within the context of
       the zone, meaning that IP fragments in different zones are not
       assembled together.  Pipeline processing for the initial
       fragments is halted.  When the final fragment is received, the
       message is assembled and pipeline processing continues for that
       flow.  Packet ordering is not guaranteed by IP protocols, so it
       is not possible to determine which IP fragment will cause message
       reassembly (and therefore continue pipeline processing). As such,
       it is strongly recommended that multiple flows should not execute
       ct to reassemble fragments from the same IP message.

       Conformance
              The ct action was introduced in Open vSwitch 2.5.  Some of
              its features were introduced later, noted individually
              above.

   The ct_clear action
       Syntax:
              ct_clear

       Clears connection tracking state from the flow, zeroing ct_state,
       ct_zone, ct_mark, and ct_label.

       This action was introduced in Open vSwitch 2.7.

   The learn action
       Syntax:
              learn(argument...)

       The learn action adds or modifies a flow in an OpenFlow table,
       similar to ovs-ofctl --strict mod-flows.  The arguments specify
       the match fields, actions, and other properties of the flow to be
       added or modified.

       Match fields for the new flow are specified as follows.  At least
       one match field should ordinarily be specified:

          field=value
                 Specifies that field, in the new flow, must match the
                 literal value, e.g. dl_type=0x800.  Shorthand match
                 syntax, such as ip in place of dl_type=0x800, is not
                 supported.

          field=src
                 Specifies that field in the new flow must match src
                 taken from the packet currently being processed.  For
                 example, udp_dst=udp_src, applied to a UDP packet with
                 source port 53, creates a flow which matches
                 udp_dst=53.  field and src must have the same width.

          field  Shorthand for the previous form when field and src are
                 the same.  For example, udp_dst, applied to a UDP
                 packet with destination port 53, creates a flow which
                 matches udp_dst=53.

       The field and src arguments above should be fields or subfields
       in the syntax described under Field Specifications above.

       Match field specifications must honor prerequisites for both the
       flow with the learn and the new flow that it creates.  Consider
       the following complete flow, in the syntax accepted by ovs-ofctl.
       If the flow’s match on udp were omitted, then the flow would not
       satisfy the prerequisites for the learn action’s use of udp_src.
       If dl_type=0x800 or nw_proto were omitted from learn, then the
       new flow would not satisfy the prerequisite for its match on
       udp_dst.  For more information on prerequisites, please refer to
       ovs-fields(7):

          udp, actions=learn(dl_type=0x800, nw_proto=17, udp_dst=udp_src)

       Actions for the new flow are specified as follows.  At least one
       action should ordinarily be specified:

          load:value->dst
                 Adds a load action to the new flow that loads the
                 literal value into dst.  The syntax is the same as the
                 load action explained in the Field Modification Actions
                 section.

          load:src->dst
                 Adds a load action to the new flow that loads src, a
                 field or subfield from the packet being processed, into
                 dst.

          output:field
                 Adds an output action to the new flow’s actions that
                 outputs to the OpenFlow port taken from field, which
                 must be a field as described above.

          fin_idle_timeout=seconds / fin_hard_timeout=seconds
                 Adds a fin_timeout action with the specified arguments
                 to the new flow.  This feature was added in Open
                 vSwitch 1.6.

       The following additional arguments are optional:
          idle_timeout=seconds

          hard_timeout=seconds

          priority=value

          cookie=value

          send_flow_rem
                 These arguments have the same meaning as in the usual
                 flow syntax documented in ovs-ofctl(8).

          table=table
                 The table in which the new flow should be inserted.
                 Specify a decimal number between 0 and 254 inclusive or
                 the name of a table.  The default, if table is
                 unspecified, is table 1 (not 0).

          delete_learned
                 When this flag is specified, deleting the flow that
                 contains the learn action will also delete the flows
                 created by learn.  Specifically, when the last learn
                 action with this flag and particular table and cookie
                 values is removed, the switch deletes all of the flows
                 in the specified table with the specified cookie.

                 This flag was added in Open vSwitch 2.4.

          limit=number
                 If the number of flows in the new flow’s table with the
                 same cookie exceeds number, the action will not add a
                 new flow.  By default, or with limit=0, there is no
                 limit.

                 This flag was added in Open vSwitch 2.8.

          result_dst=field[bit]
                 If learn fails (because the number of flows exceeds
                 limit), the action sets field[bit] to 0, otherwise it
                 will be set to 1.  field[bit] must be a single bit.

                 This flag was added in Open vSwitch 2.8.

       By itself, the learn action can only put two kinds of actions
       into the flows that it creates: load and output actions.  If
       learn is used in isolation, these are severe limits.

       However, learn is not meant to be used in isolation.  It is a
       primitive meant to be used together with other Open vSwitch
       features to accomplish a task.  Its existing features are enough
       to accomplish most tasks.

       Here is an outline of a typical pipeline structure that allows
       for versatile behavior using learn:

          • Flows in table A contain a learn action, that populates
            flows in table L, that use a load action to populate
            register R with information about what was learned.

          • Flows in table B contain two sequential resubmit actions:
            one to table L and another one to table B + 1.

          • Flows in table B + 1 match on register R and act differently
            depending on what the flows in table L loaded into it.

       This approach can be used to implement many learn-based features.
       For example:

          • Resubmit to a table selected based on learned information,
            e.g. see
            https://mail.openvswitch.org/pipermail/ovs-discuss/2016-June/021694.html 
            .

          • MAC learning in the middle of a pipeline, as described in
            the Open vSwitch Advanced Features Tutorial in the OVS
            documentation.

          • TCP state based firewalling, by learning outgoing
            connections based on SYN packets and matching them up with
            incoming packets.  (This is usually better implemented using
            the ct action.)

          • At least some of the features described in T. A. Hoff,
            Extending Open vSwitch to Facilitate Creation of Stateful
            SDN Applications.

       Conformance
              The learn action is an Open vSwitch extension to OpenFlow
              added in Open vSwitch 1.3.  Some features of learn were
              added in later versions, as noted individually above.

   The fin_timeout action
       Syntax:
              fin_timeout(key=value...)

       This action changes the idle timeout or hard timeout, or both, of
       the OpenFlow flow that contains it, when the flow matches a TCP
       packet with the FIN or RST flag.  When such a packet is observed,
       the action reduces the rule’s timeouts to those specified on the
       action.  If the rule’s existing timeout is already shorter than
       the one that the action specifies, then that timeout is
       unaffected.

       The timeouts are specified as key-value pairs:

          idle_timeout=seconds
                 Causes the flow to expire after the given number of
                 seconds of inactivity.

          hard_timeout=seconds
                 Causes the flow to expire after the given number of
                 seconds, regardless of activity.  (seconds specifies
                 time since the flow’s creation, not since the receipt
                 of the FIN or RST.)

       This action is normally added to a learned flow by the learn
       action.  It is unlikely to be useful otherwise.

       Conformance
              This Open vSwitch extension action was added in Open
              vSwitch 1.6.

PROGRAMMING AND CONTROL FLOW ACTIONS         top

   The resubmit action
       Syntax:
              resubmit:port
              resubmit([port],[table][,ct])``

       Searches an OpenFlow flow table for a matching flow and executes
       the actions found, if any, before continuing to the following
       action in the current flow entry.  Arguments can customize the
       search:

          • If port is given as an OpenFlow port number or name, then it
            specifies a value to use for the input port metadata field
            as part of the search, in place of the input port currently
            in the flow.  Specifying in_port as port is equivalent to
            omitting it.

          • If table is given as an integer between 0 and 254 or a table
            name, it specifies the OpenFlow table to search.  If it is
            not specified, the table from the current flow is used.

          • If ct is specified, then the search is done with packet
            5-tuple fields swapped with the corresponding conntrack
            original direction tuple fields.  See the documentation for
            ct above, for more information about connection tracking, or
            ovs-fields(7) for details about the connection tracking
            fields.

            This flag requires a valid connection tracking state as a
            match prerequisite in the flow where this action is placed.
            Examples of valid connection tracking state matches include
            ct_state=+new, ct_state=+est, ct_state=+rel, and
            ct_state=+trk-inv.

       The changes, if any, to the input port and connection tracking
       fields are just for searching the flow table.  The changes are
       not visible to actions or to later flow table lookups.

       The most common use of resubmit is to visit another flow table
       without port or ct, like this: resubmit(,table).

       Recursive resubmit actions are permitted.

       Conformance
              The resubmit action is an Open vSwitch extension.
              However, the goto_table instruction in OpenFlow 1.1 and
              later can be viewed as a kind of restricted resubmit.

              Open vSwitch 1.3 added table.  Open vSwitch 2.7 added ct.

              Open vSwitch imposes a limit on resubmit recursion that
              varies among version:

                 • Open vSwitch 1.0.1 and earlier did not support
                   recursion.

                 • Open vSwitch 1.0.2 and 1.0.3 limited recursion to 8
                   levels.

                 • Open vSwitch 1.1 and 1.2 limited recursion to 16
                   levels.

                 • Open vSwitch 1.2 through 1.8 limited recursion to 32
                   levels.

                 • Open vSwitch 1.9 through 2.0 limited recursion to 64
                   levels.

                 • Open vSwitch 2.1 through 2.5 limited recursion to 64
                   levels and impose a total limit of 4,096 resubmits
                   per flow translation (earlier versions did not impose
                   any total limit).

                 • Open vSwitch 2.6 and later imposes the same limits as
                   2.5, with one exception: resubmit from table x to any
                   table y > x does not count against the recursion
                   depth limit.

   The clone action
       Syntax:
              clone(action...)

       Executes each nested action, saving much of the packet and
       pipeline state beforehand and then restoring it afterward.  The
       state that is saved and restored includes all flow data and
       metadata (including, for example, in_port and ct_state), the
       stack accessed by push and pop actions, and the OpenFlow action
       set.

       This action was added in Open vSwitch 2.7.

   The push and pop actions
       Syntax:
              push:src
              pop:dst

       The push action pushes src on a general-purpose stack.  The pop
       action pops an entry off the stack into dst.  src and dst should
       be fields or subfields in the syntax described under Field
       Specifications above.

       Controllers can use the stack for saving and restoring data or
       metadata around resubmit actions, for swapping or rearranging
       data and metadata, or for other purposes.  Any data or metadata
       field, or part of one, may be pushed, and any modifiable field or
       subfield may be popped.

       The number of bits pushed in a stack entry do not have to match
       the number of bits later popped from that entry.  If more bits
       are popped from an entry than were pushed, then the entry is
       conceptually left-padded with 0-bits as needed.  If fewer bits
       are popped than pushed, then bits are conceptually trimmed from
       the left side of the entry.

       The stack’s size is limited.  The limit is intended to be high
       enough that normal use will not pose problems.  Stack overflow or
       underflow is an error that stops action execution (see Stack too
       deep under Error Handling, above).

       Examples:

          • push:reg2[0..5] or push:NXM_NX_REG2[0..5] pushes on the
            stack the 6 bits in register 2 bits 0 through 5.

          • pop:reg2[0..5] or pop:NXM_NX_REG2[0..5] pops the value from
            top of the stack and copy bits 0 through 5 of that value
            into bits 0 through 5 of register 2.

       Conformance
              Open vSwitch 1.2 introduced push and pop as OpenFlow
              extension actions.

   The exit action
       Syntax:
              exit

       This action causes Open vSwitch to immediately halt execution of
       further actions.  Actions which have already been executed are
       unaffected.  Any further actions, including those which may be in
       other tables, or different levels of the resubmit call stack, are
       ignored.  However, an exit action within a group bucket
       terminates only execution of that bucket, not other buckets or
       the overall pipeline.  Actions in the action set are still
       executed (specify clear_actions before exit to discard them).

   The multipath action
       Syntax:
              multipath(fields,basis,algorithm,n_links,arg,dst)

       Hashes fields using basis as a universal hash parameter, then the
       applies multipath link selection algorithm (with parameter arg)
       to choose one of n_links output links numbered 0 through n_links
       minus 1, and stores the link into dst, which must be a field or
       subfield in the syntax described under Field Specifications
       above.

       The bundle or bundle_load actions are usually easier to use than
       multipath.

       fields must be one of the following:

          eth_src
                 Hashes Ethernet source address only.

          symmetric_l4
                 Hashes Ethernet source, destination, and type, VLAN ID,
                 IPv4/IPv6 source, destination, and protocol, and TCP or
                 SCTP (but not UDP) ports.  The hash is computed so that
                 pairs of corresponding flows in each direction hash to
                 the same value, in environments where L2 paths are the
                 same in each direction.  UDP ports are not included in
                 the hash to support protocols such as VXLAN that use
                 asymmetric ports in each direction.

          symmetric_l3l4
                 Hashes IPv4/IPv6 source, destination, and protocol, and
                 TCP or SCTP (but not UDP) ports.  Like symmetric_l4,
                 this is a symmetric hash, but by excluding L2 headers
                 it is more effective in environments with asymmetric L2
                 paths (e.g. paths involving VRRP IP addresses on a
                 router).  Not an effective hash function for protocols
                 other than IPv4 and IPv6, which hash to a constant
                 zero.

          symmetric_l3l4+udp
                 Like symmetric_l3l4+udp, but UDP ports are included in
                 the hash.  This is a more effective hash when
                 asymmetric UDP protocols such as VXLAN are not a
                 consideration.

          symmetric_l3
                 Hashes network source address and network destination
                 address.

          nw_src Hashes network source address only.

          nw_dst Hashes network destination address only.

       The algorithm used to compute the final result link must be one
       of the following:

          modulo_n
                 Computes link = hash(flow) % n_links.

                 This algorithm redistributes all traffic when n_links
                 changes.  It has O(1) performance.

                 Use 65535 for max_link to get a raw hash value.

                 This algorithm is specified by RFC 2992.

          hash_threshold
                 Computes link = hash(flow) / (MAX_HASH / n_links).

                 Redistributes between one-quarter and one-half of
                 traffic when n_links changes.  It has O(1) performance.

                 This algorithm is specified by RFC 2992.

          hrw (Highest Random Weight)
                 Computes the following:

                     for i in [0, n_links]:
                         weights[i] = hash(flow, i)
                     link = { i such that weights[i] >= weights[j] for all j != i }

                 Redistributes 1 / n_links of traffic when n_links
                 changes.  It has O(n_links) performance.  If n_links is
                 greater than a threshold (currently 64, but subject to
                 change), Open vSwitch will substitute another algorithm
                 automatically.

                 This algorithm is specified by RFC 2992.

          iter_hash (Iterative Hash)
                 Computes the following:

                     i = 0
                     repeat:
                         i = i + 1
                         link = hash(flow, i) % arg
                     while link > max_link

                 Redistributes 1 / n_links of traffic when n_links
                 changes.  O(1) performance when arg / max_link is
                 bounded by a constant.

                 Redistributes all traffic when arg changes.

                 arg must be greater than max_link and for best
                 performance should be no more than approximately
                 max_link * 2.  If arg is outside the acceptable range,
                 Open vSwitch will automatically substitute the least
                 power of 2 greater than max_link.

                 This algorithm is specific to Open vSwitch.

       Only the iter_hash algorithm uses arg.

       It is an error if max_link is greater than or equal to 2**n_bits.

       Conformance
              This is an OpenFlow extension added in Open vSwitch 1.1.

OTHER ACTIONS         top

   The conjunction action
       Syntax:
              conjunction(id, k/n)

       This action allows for sophisticated conjunctive match flows.
       Refer to Conjunctive Match Fields in ovs-fields(7) for details.

       A flow that has one or more conjunction actions may not have any
       other actions except for note actions.

       Conformance
              Open vSwitch 2.4 introduced the conjunction action and
              conj_id field.  They are Open vSwitch extensions to
              OpenFlow.

   The note action
       Syntax:
              note:[hh]...

       This action does nothing at all.  OpenFlow controllers may use it
       to annotate flows with more data than can fit in a flow cookie.

       The action may include any number of bytes represented as hex
       digits hh.  Periods may separate pairs of hex digits, for
       readability.  The note action’s format doesn’t include an exact
       length for its payload, so the provided bytes will be padded on
       the right by enough bytes with value 0 to make the total number 6
       more than a multiple of 8.

       Conformance
              This action is an extension to OpenFlow introduced in Open
              vSwitch 1.1.

   The sample action
       Syntax:
              sample(argument...)

       Samples packets and sends one sample for every sampled packet.

       The following argument forms are accepted:

          probability=packets
                 The number of sampled packets out of 65535.  Must be
                 greater or equal to 1.

          collector_set_id=id
                 The unsigned 32-bit integer identifier of the set of
                 sample collectors to send sampled packets to.  Defaults
                 to 0.

          obs_domain_id=id
                 When sending samples to IPFIX collectors, the unsigned
                 32-bit integer Observation Domain ID sent in every
                 IPFIX flow record.  Defaults to 0.

          obs_point_id=id
                 When sending samples to IPFIX collectors, the unsigned
                 32-bit integer Observation Point ID sent in every IPFIX
                 flow record.  Defaults to 0.

          sampling_port=port
                 Sample packets on port, which should be the ingress or
                 egress port.  This option, which was added in Open
                 vSwitch 2.6, allows the IPFIX implementation to export
                 egress tunnel information.

          ingress

          egress Specifies explicitly that the packet is being sampled
                 on ingress to or egress from the switch.  IPFIX reports
                 sent by Open vSwitch before version 2.6 did not include
                 a direction.  From 2.6 until 2.7, IPFIX reports
                 inferred a direction from sampling_port: if it was the
                 packet’s output port, then the direction was reported
                 as egress, otherwise as ingress.  Open vSwitch 2.7
                 introduced these options, which allow the inferred
                 direction to be overridden.  This is particularly
                 useful when the ingress (or egress) port is not a
                 tunnel.

       Refer to ovs-vswitchd.conf.db(5) for more details on configuring
       sample collector sets.

       Conformance
              This action is an OpenFlow extension added in Open vSwitch
              2.4.

INSTRUCTIONS         top

       Every version of OpenFlow includes actions.  OpenFlow 1.1
       introduced the higher-level, related concept of instructions.  In
       OpenFlow 1.1 and later, actions within a flow are always
       encapsulated within an instruction.  Each flow has at most one
       instruction of each kind, which are executed in the following
       fixed order defined in the OpenFlow specification:

          1. Meter

          2. Apply-Actions

          3. Clear-Actions

          4. Write-Actions

          5. Write-Metadata

          6. Stat-Trigger (not supported by Open vSwitch)

          7. Goto-Table

       The most important instruction is Apply-Actions.  This
       instruction encapsulates any number of actions, which the
       instruction executes.  Open vSwitch does not explicitly represent
       Apply-Actions.  Instead, any action by itself is implicitly part
       of an Apply-Actions instructions.

       Open vSwitch syntax requires other instructions, if present, to
       be in the order listed above.  Otherwise it will flag an error.

   The meter action and instruction
       Syntax:
              meter:meter_id

       Apply meter meter_id.  If a meter band rate is exceeded, the
       packet may be dropped, or modified, depending on the meter band
       type.

       Conformance
              OpenFlow 1.3 introduced the meter instruction.  OpenFlow
              1.5 changes meter from an instruction to an action.

              OpenFlow 1.5 allows implementations to restrict meter to
              be the first action in an action list and to exclude meter
              from action sets, for better compatibility with OpenFlow
              1.3 and 1.4.  Open vSwitch restricts the meter action both
              ways.

              Open vSwitch 2.0 introduced OpenFlow protocol support for
              meters, but it did not include a datapath implementation.
              Open vSwitch 2.7 added meter support to the userspace
              datapath.  Open vSwitch 2.10 added meter support to the
              kernel datapath.  Open vSwitch 2.12 added support for
              meter as an action in OpenFlow 1.5.

   The clear_actions instruction
       Syntax:
              clear_actions

       Clears the action set.  See Action Sets, above, for more
       information.

       Conformance
              OpenFlow 1.1 introduced clear_actions.  Open vSwitch 2.1
              added support for clear_actions.

   The write_actions instruction
       Syntax:
              write_actions(action...)

       Adds each action to the action set.  The action set is carried
       between flow tables and then executed at the end of the pipeline.
       Only certain actions may be written to the action set.  See
       Action Sets, above, for more information.

       Conformance
              OpenFlow 1.1 introduced write_actions.  Open vSwitch 2.1
              added support for write_actions.

   The write_metadata instruction
       Syntax:
              write_metadata:value[/mask]

       Updates the flow’s metadata field.  If mask is omitted, metadata
       is set exactly to value; if mask is specified, then a 1-bit in
       mask indicates that the corresponding bit in metadata will be
       replaced with the corresponding bit from value.  Both value and
       mask are 64-bit values that are decimal by default; use a 0x
       prefix to specify them in hexadecimal.

       The metadata field can also be matched in the flow table and
       updated with actions such as set_field and move.

       Conformance
              OpenFlow 1.1 introduced write_metadata.  Open vSwitch 2.1
              added support for write_metadata.

   The goto_table instruction
       Syntax:
              goto_table:table

       Jumps to table as the next table in the process pipeline.  The
       table may be a number between 0 and 254 or a table name.

       It is an error if table is less than or equal to the table of the
       flow that contains it; that is, goto_table must move forward in
       the OpenFlow pipeline.  Since goto_table must be the last
       instruction in a flow, it never leads to recursion.  The resubmit
       extension action is more flexible.

       Conformance
              OpenFlow 1.1 introduced goto_table.  Open vSwitch 2.1
              added support for goto_table.

AUTHOR         top

       The Open vSwitch Development Community

COPYRIGHT         top

       2016-2024, The Open vSwitch Development Community

COLOPHON         top

       This page is part of the Open vSwitch (a distributed virtual
       multilayer switch) project.  Information about the project can be
       found at ⟨http://openvswitch.org/⟩.  If you have a bug report for
       this manual page, send it to [email protected].  This page was
       obtained from the project's upstream Git repository
       ⟨https://github.com/openvswitch/ovs.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-07.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       [email protected]

3.3.90                        Jun 13, 2024                OVS-ACTIONS(7)

Pages that refer to this page: ovn-nb(5)ovn-sb(5)ovs-vswitchd.conf.db(5)ovs-ofctl(8)