ovn-sb(5) — Linux manual page

NAME | TABLE SUMMARY | SB_Global TABLE | Chassis TABLE | Encap TABLE | Address_Set TABLE | Port_Group TABLE | Logical_Flow TABLE | Multicast_Group TABLE | Meter TABLE | Meter_Band TABLE | Datapath_Binding TABLE | Port_Binding TABLE | MAC_Binding TABLE | DHCP_Options TABLE | DHCPv6_Options TABLE | Connection TABLE | SSL TABLE | DNS TABLE | RBAC_Role TABLE | RBAC_Permission TABLE | Gateway_Chassis TABLE | HA_Chassis TABLE | HA_Chassis_Group TABLE | Controller_Event TABLE | IP_Multicast TABLE | IGMP_Group TABLE | COLOPHON

ovn-sb(5)                  Open vSwitch Manual                 ovn-sb(5)

NAME         top

       ovn-sb - OVN_Southbound database schema

       This database holds logical and physical configuration and state
       for the Open Virtual Network (OVN) system to support virtual
       network abstraction. For an introduction to OVN, please see
       ovn-architecture(7).

       The OVN Southbound database sits at the center of the OVN
       architecture. It is the one component that speaks both southbound
       directly to all the hypervisors and gateways, via
       ovn-controller/ovn-controller-vtep, and northbound to the Cloud
       Management System, via ovn-northd:

   Database Structure
       The OVN Southbound database contains classes of data with
       different properties, as described in the sections below.

     Physical network

       Physical network tables contain information about the chassis
       nodes in the system. This contains all the information necessary
       to wire the overlay, such as IP addresses, supported tunnel
       types, and security keys.

       The amount of physical network data is small (O(n) in the number
       of chassis) and it changes infrequently, so it can be replicated
       to every chassis.

       The Chassis and Encap tables are the physical network tables.

     Logical Network

       Logical network tables contain the topology of logical switches
       and routers, ACLs, firewall rules, and everything needed to
       describe how packets traverse a logical network, represented as
       logical datapath flows (see Logical Datapath Flows, below).

       Logical network data may be large (O(n) in the number of logical
       ports, ACL rules, etc.). Thus, to improve scaling, each chassis
       should receive only data related to logical networks in which
       that chassis participates.

       The logical network data is ultimately controlled by the cloud
       management system (CMS) running northbound of OVN. That CMS
       determines the entire OVN logical configuration and therefore the
       logical network data at any given time is a deterministic
       function of the CMS’s configuration, although that happens
       indirectly via the OVN_Northbound database and ovn-northd.

       Logical network data is likely to change more quickly than
       physical network data. This is especially true in a container
       environment where containers are created and destroyed (and
       therefore added to and deleted from logical switches) quickly.

       The Logical_Flow, Multicast_Group, Address_Group, DHCP_Options,
       DHCPv6_Options, and DNS tables contain logical network data.

     Logical-physical bindings

       These tables link logical and physical components. They show the
       current placement of logical components (such as VMs and VIFs)
       onto chassis, and map logical entities to the values that
       represent them in tunnel encapsulations.

       These tables change frequently, at least every time a VM powers
       up or down or migrates, and especially quickly in a container
       environment. The amount of data per VM (or VIF) is small.

       Each chassis is authoritative about the VMs and VIFs that it
       hosts at any given time and can efficiently flood that state to a
       central location, so the consistency needs are minimal.

       The Port_Binding and Datapath_Binding tables contain binding
       data.

     MAC bindings

       The MAC_Binding table tracks the bindings from IP addresses to
       Ethernet addresses that are dynamically discovered using ARP (for
       IPv4) and neighbor discovery (for IPv6). Usually, IP-to-MAC
       bindings for virtual machines are statically populated into the
       Port_Binding table, so MAC_Binding is primarily used to discover
       bindings on physical networks.

   Common Columns
       Some tables contain a special column named external_ids. This
       column has the same form and purpose each place that it appears,
       so we describe it here to save space later.

              external_ids: map of string-string pairs
                     Key-value pairs for use by the software that
                     manages the OVN Southbound database rather than by
                     ovn-controller/ovn-controller-vtep. In particular,
                     ovn-northd can use key-value pairs in this column
                     to relate entities in the southbound database to
                     higher-level entities (such as entities in the OVN
                     Northbound database). Individual key-value pairs in
                     this column may be documented in some cases to aid
                     in understanding and troubleshooting, but the
                     reader should not mistake such documentation as
                     comprehensive.

TABLE SUMMARY         top

       The following list summarizes the purpose of each of the tables
       in the OVN_Southbound database.  Each table is described in more
       detail on a later page.

       Table     Purpose
       SB_Global Southbound configuration
       Chassis   Physical Network Hypervisor and Gateway Information
       Encap     Encapsulation Types
       Address_Set
                 Address Sets
       Port_Group
                 Port Groups
       Logical_Flow
                 Logical Network Flows
       Multicast_Group
                 Logical Port Multicast Groups
       Meter     Meter entry
       Meter_Band
                 Band for meter entries
       Datapath_Binding
                 Physical-Logical Datapath Bindings
       Port_Binding
                 Physical-Logical Port Bindings
       MAC_Binding
                 IP to MAC bindings
       DHCP_Options
                 DHCP Options supported by native OVN DHCP
       DHCPv6_Options
                 DHCPv6 Options supported by native OVN DHCPv6
       Connection
                 OVSDB client connections.
       SSL       SSL configuration.
       DNS       Native DNS resolution
       RBAC_Role RBAC_Role configuration.
       RBAC_Permission
                 RBAC_Permission configuration.
       Gateway_Chassis
                 Gateway_Chassis configuration.
       HA_Chassis
                 HA_Chassis configuration.
       HA_Chassis_Group
                 HA_Chassis_Group configuration.
       Controller_Event
                 Controller Event table
       IP_Multicast
                 IP_Multicast configuration.
       IGMP_Group
                 IGMP_Group configuration.

SB_Global TABLE         top

       Southbound configuration for an OVN system. This table must have
       exactly one row.

   Summary:
       Status:
         nb_cfg                      integer
       Common Columns:
         external_ids                map of string-string pairs
         options                     map of string-string pairs
       Common options:
         options                     map of string-string pairs
         Options for configuring BFD:
            options : bfd-min-rx     optional string
            options : bfd-decay-min-rx
                                     optional string
            options : bfd-min-tx     optional string
            options : bfd-mult       optional string
       Connection Options:
         connections                 set of Connections
         ssl                         optional SSL
       Security Configurations:
         ipsec                       boolean

   Details:
     Status:

       This column allow a client to track the overall configuration
       state of the system.

       nb_cfg: integer
              Sequence number for the configuration. When a CMS or
              ovn-nbctl updates the northbound database, it increments
              the nb_cfg column in the NB_Global table in the northbound
              database. In turn, when ovn-northd updates the southbound
              database to bring it up to date with these changes, it
              updates this column to the same value.

     Common Columns:

       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.

       options: map of string-string pairs

     Common options:

       options: map of string-string pairs
              This column provides general key/value settings. The
              supported options are described individually below.

     Options for configuring BFD:

       These options apply when ovn-controller configures BFD on tunnels
       interfaces.

       options : bfd-min-rx: optional string
              BFD option min-rx value to use when configuring BFD on
              tunnel interfaces.

       options : bfd-decay-min-rx: optional string
              BFD option decay-min-rx value to use when configuring BFD
              on tunnel interfaces.

       options : bfd-min-tx: optional string
              BFD option min-tx value to use when configuring BFD on
              tunnel interfaces.

       options : bfd-mult: optional string
              BFD option mult value to use when configuring BFD on
              tunnel interfaces.

     Connection Options:

       connections: set of Connections
              Database clients to which the Open vSwitch database server
              should connect or on which it should listen, along with
              options for how these connections should be configured.
              See the Connection table for more information.

       ssl: optional SSL
              Global SSL configuration.

     Security Configurations:

       ipsec: boolean
              Tunnel encryption configuration. If this column is set to
              be true, all OVN tunnels will be encrypted with IPsec.

Chassis TABLE         top

       Each row in this table represents a hypervisor or gateway (a
       chassis) in the physical network. Each chassis, via
       ovn-controller/ovn-controller-vtep, adds and updates its own row,
       and keeps a copy of the remaining rows to determine how to reach
       other hypervisors.

       When a chassis shuts down gracefully, it should remove its own
       row. (This is not critical because resources hosted on the
       chassis are equally unreachable regardless of whether the row is
       present.) If a chassis shuts down permanently without removing
       its row, some kind of manual or automatic cleanup is eventually
       needed; we can devise a process for that as necessary.

   Summary:
       name                          string (must be unique within
                                     table)
       hostname                      string
       nb_cfg                        integer
       external_ids : ovn-bridge-mappings
                                     optional string
       external_ids : datapath-type  optional string
       external_ids : iface-types    optional string
       external_ids : ovn-cms-options
                                     optional string
       transport_zones               set of strings
       external_ids : ovn-chassis-mac-mappings
                                     optional string
       Common Columns:
         external_ids                map of string-string pairs
       Encapsulation Configuration:
         encaps                      set of 1 or more Encaps
       Gateway Configuration:
         vtep_logical_switches       set of strings

   Details:
       name: string (must be unique within table)
              OVN does not prescribe a particular format for chassis
              names. ovn-controller populates this column using
              external_ids:system-id in the Open_vSwitch database’s
              Open_vSwitch table. ovn-controller-vtep populates this
              column with name in the hardware_vtep database’s
              Physical_Switch table.

       hostname: string
              The hostname of the chassis, if applicable. ovn-controller
              will populate this column with the hostname of the host it
              is running on. ovn-controller-vtep will leave this column
              empty.

       nb_cfg: integer
              Sequence number for the configuration. When ovn-controller
              updates the configuration of a chassis from the contents
              of the southbound database, it copies nb_cfg from the
              SB_Global table into this column.

       external_ids : ovn-bridge-mappings: optional string
              ovn-controller populates this key with the set of bridge
              mappings it has been configured to use. Other applications
              should treat this key as read-only. See ovn-controller(8)
              for more information.

       external_ids : datapath-type: optional string
              ovn-controller populates this key with the datapath type
              configured in the datapath_type column of the Open_vSwitch
              database’s Bridge table. Other applications should treat
              this key as read-only. See ovn-controller(8) for more
              information.

       external_ids : iface-types: optional string
              ovn-controller populates this key with the interface types
              configured in the iface_types column of the Open_vSwitch
              database’s Open_vSwitch table. Other applications should
              treat this key as read-only. See ovn-controller(8) for
              more information.

       external_ids : ovn-cms-options: optional string
              ovn-controller populates this key with the set of options
              configured in the external_ids:ovn-cms-options column of
              the Open_vSwitch database’s Open_vSwitch table. See
              ovn-controller(8) for more information.

       transport_zones: set of strings
              ovn-controller populates this key with the transport zones
              configured in the external_ids:ovn-transport-zones column
              of the Open_vSwitch database’s Open_vSwitch table. See
              ovn-controller(8) for more information.

       external_ids : ovn-chassis-mac-mappings: optional string
              ovn-controller populates this key with the set of options
              configured in the external_ids:ovn-chassis-mac-mappings
              column of the Open_vSwitch database’s Open_vSwitch table.
              See ovn-controller(8) for more information.

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

     Encapsulation Configuration:

       OVN uses encapsulation to transmit logical dataplane packets
       between chassis.

       encaps: set of 1 or more Encaps
              Points to supported encapsulation configurations to
              transmit logical dataplane packets to this chassis. Each
              entry is a Encap record that describes the configuration.

     Gateway Configuration:

       A gateway is a chassis that forwards traffic between the OVN-
       managed part of a logical network and a physical VLAN, extending
       a tunnel-based logical network into a physical network. Gateways
       are typically dedicated nodes that do not host VMs and will be
       controlled by ovn-controller-vtep.

       vtep_logical_switches: set of strings
              Stores all VTEP logical switch names connected by this
              gateway chassis. The Port_Binding table entry with
              options:vtep-physical-switch equal Chassis name, and
              options:vtep-logical-switch value in Chassis
              vtep_logical_switches, will be associated with this
              Chassis.

Encap TABLE         top

       The encaps column in the Chassis table refers to rows in this
       table to identify how OVN may transmit logical dataplane packets
       to this chassis. Each chassis, via ovn-controller(8) or
       ovn-controller-vtep(8), adds and updates its own rows and keeps a
       copy of the remaining rows to determine how to reach other
       chassis.

   Summary:
       type                          string, one of geneve, stt, or
                                     vxlan
       options                       map of string-string pairs
       options : csum                optional string, either true or
                                     false
       options : dst_port            optional string, containing an
                                     integer
       ip                            string
       chassis_name                  string

   Details:
       type: string, one of geneve, stt, or vxlan
              The encapsulation to use to transmit packets to this
              chassis. Hypervisors must use either geneve or stt.
              Gateways may use vxlan, geneve, or stt.

       options: map of string-string pairs
              Options for configuring the encapsulation, which may be
              type specific.

       options : csum: optional string, either true or false
              csum indicates whether this chassis can transmit and
              receive packets that include checksums with reasonable
              performance. It hints to senders transmitting data to this
              chassis that they should use checksums to protect OVN
              metadata. ovn-controller populates this key with the value
              defined in external_ids:ovn-encap-csum column of the
              Open_vSwitch database’s Open_vSwitch table. Other
              applications should treat this key as read-only. See
              ovn-controller(8) for more information.

              In terms of performance, checksumming actually
              significantly increases throughput in most common cases
              when running on Linux based hosts without NICs supporting
              encapsulation hardware offload (around 60% for bulk
              traffic). The reason is that generally all NICs are
              capable of offloading transmitted and received TCP/UDP
              checksums (viewed as ordinary data packets and not as
              tunnels). The benefit comes on the receive side where the
              validated outer checksum can be used to additionally
              validate an inner checksum (such as TCP), which in turn
              allows aggregation of packets to be more efficiently
              handled by the rest of the stack.

              Not all devices see such a benefit. The most notable
              exception is hardware VTEPs. These devices are designed to
              not buffer entire packets in their switching engines and
              are therefore unable to efficiently compute or validate
              full packet checksums. In addition certain versions of the
              Linux kernel are not able to fully take advantage of
              encapsulation NIC offloads in the presence of checksums.
              (This is actually a pretty narrow corner case though:
              earlier versions of Linux don’t support encapsulation
              offloads at all and later versions support both offloads
              and checksums well.)

              csum defaults to false for hardware VTEPs and true for all
              other cases.

              This option applies to geneve and vxlan encapsulations.

       options : dst_port: optional string, containing an integer
              If set, overrides the UDP (for geneve and vxlan) or TCP
              (for stt) destination port.

       ip: string
              The IPv4 address of the encapsulation tunnel endpoint.

       chassis_name: string
              The name of the chassis that created this encap.

Address_Set TABLE         top

       This table contains address sets synced from the Address_Set
       table in the OVN_Northbound database and address sets generated
       from the Port_Group table in the OVN_Northbound database.

       See the documentation for the Address_Set table and Port_Group
       table in the OVN_Northbound database for details.

   Summary:
       name                          string (must be unique within
                                     table)
       addresses                     set of strings

   Details:
       name: string (must be unique within table)

       addresses: set of strings

Port_Group TABLE         top

       This table contains names for the logical switch ports in the
       OVN_Northbound database that belongs to the same group that is
       defined in Port_Group in the OVN_Northbound database.

   Summary:
       name                          string (must be unique within
                                     table)
       ports                         set of strings

   Details:
       name: string (must be unique within table)

       ports: set of strings

Logical_Flow TABLE         top

       Each row in this table represents one logical flow. ovn-northd
       populates this table with logical flows that implement the L2 and
       L3 topologies specified in the OVN_Northbound database. Each
       hypervisor, via ovn-controller, translates the logical flows into
       OpenFlow flows specific to its hypervisor and installs them into
       Open vSwitch.

       Logical flows are expressed in an OVN-specific format, described
       here. A logical datapath flow is much like an OpenFlow flow,
       except that the flows are written in terms of logical ports and
       logical datapaths instead of physical ports and physical
       datapaths. Translation between logical and physical flows helps
       to ensure isolation between logical datapaths. (The logical flow
       abstraction also allows the OVN centralized components to do less
       work, since they do not have to separately compute and push out
       physical flows to each chassis.)

       The default action when no flow matches is to drop packets.

       Architectural Logical Life Cycle of a Packet

       This following description focuses on the life cycle of a packet
       through a logical datapath, ignoring physical details of the
       implementation. Please refer to Architectural Physical Life Cycle
       of a Packet in ovn-architecture(7) for the physical information.

       The description here is written as if OVN itself executes these
       steps, but in fact OVN (that is, ovn-controller) programs Open
       vSwitch, via OpenFlow and OVSDB, to execute them on its behalf.

       At a high level, OVN passes each packet through the logical
       datapath’s logical ingress pipeline, which may output the packet
       to one or more logical port or logical multicast groups. For each
       such logical output port, OVN passes the packet through the
       datapath’s logical egress pipeline, which may either drop the
       packet or deliver it to the destination. Between the two
       pipelines, outputs to logical multicast groups are expanded into
       logical ports, so that the egress pipeline only processes a
       single logical output port at a time. Between the two pipelines
       is also where, when necessary, OVN encapsulates a packet in a
       tunnel (or tunnels) to transmit to remote hypervisors.

       In more detail, to start, OVN searches the Logical_Flow table for
       a row with correct logical_datapath, a pipeline of ingress, a
       table_id of 0, and a match that is true for the packet. If none
       is found, OVN drops the packet. If OVN finds more than one, it
       chooses the match with the highest priority. Then OVN executes
       each of the actions specified in the row’s actions column, in the
       order specified. Some actions, such as those to modify packet
       headers, require no further details. The next and output actions
       are special.

       The next action causes the above process to be repeated
       recursively, except that OVN searches for table_id of 1 instead
       of 0. Similarly, any next action in a row found in that table
       would cause a further search for a table_id of 2, and so on. When
       recursive processing completes, flow control returns to the
       action following next.

       The output action also introduces recursion. Its effect depends
       on the current value of the outport field. Suppose outport
       designates a logical port. First, OVN compares inport to outport;
       if they are equal, it treats the output as a no-op by default. In
       the common case, where they are different, the packet enters the
       egress pipeline. This transition to the egress pipeline discards
       register data, e.g. reg0 ... reg9 and connection tracking state,
       to achieve uniform behavior regardless of whether the egress
       pipeline is on a different hypervisor (because registers aren’t
       preserve across tunnel encapsulation).

       To execute the egress pipeline, OVN again searches the
       Logical_Flow table for a row with correct logical_datapath, a
       table_id of 0, a match that is true for the packet, but now
       looking for a pipeline of egress. If no matching row is found,
       the output becomes a no-op. Otherwise, OVN executes the actions
       for the matching flow (which is chosen from multiple, if
       necessary, as already described).

       In the egress pipeline, the next action acts as already
       described, except that it, of course, searches for egress flows.
       The output action, however, now directly outputs the packet to
       the output port (which is now fixed, because outport is read-only
       within the egress pipeline).

       The description earlier assumed that outport referred to a
       logical port. If it instead designates a logical multicast group,
       then the description above still applies, with the addition of
       fan-out from the logical multicast group to each logical port in
       the group. For each member of the group, OVN executes the logical
       pipeline as described, with the logical output port replaced by
       the group member.

       Pipeline Stages

       ovn-northd populates the Logical_Flow table with the logical
       flows described in detail in ovn-northd(8).

   Summary:
       logical_datapath              Datapath_Binding
       pipeline                      string, either egress or ingress
       table_id                      integer, in range 0 to 23
       priority                      integer, in range 0 to 65,535
       match                         string
       actions                       string
       external_ids : stage-name     optional string
       external_ids : stage-hint     optional string, containing an uuid
       external_ids : source         optional string
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       logical_datapath: Datapath_Binding
              The logical datapath to which the logical flow belongs.

       pipeline: string, either egress or ingress
              The primary flows used for deciding on a packet’s
              destination are the ingress flows. The egress flows
              implement ACLs. See Logical Life Cycle of a Packet, above,
              for details.

       table_id: integer, in range 0 to 23
              The stage in the logical pipeline, analogous to an
              OpenFlow table number.

       priority: integer, in range 0 to 65,535
              The flow’s priority. Flows with numerically higher
              priority take precedence over those with lower. If two
              logical datapath flows with the same priority both match,
              then the one actually applied to the packet is undefined.

       match: string
              A matching expression. OVN provides a superset of OpenFlow
              matching capabilities, using a syntax similar to Boolean
              expressions in a programming language.

              The most important components of match expression are
              comparisons between symbols and constants, e.g. ip4.dst ==
              192.168.0.1, ip.proto == 6, arp.op == 1, eth.type ==
              0x800. The logical AND operator && and logical OR operator
              || can combine comparisons into a larger expression.

              Matching expressions also support parentheses for
              grouping, the logical NOT prefix operator !, and literals
              0 and 1 to express ``false’’ or ``true,’’ respectively.
              The latter is useful by itself as a catch-all expression
              that matches every packet.

              Match expressions also support a kind of function syntax.
              The following functions are supported:

              is_chassis_resident(lport)
                     Evaluates to true on a chassis on which logical
                     port lport (a quoted string) resides, and to false
                     elsewhere. This function was introduced in OVN 2.7.

              Symbols

              Type. Symbols have integer or string type. Integer symbols
              have a width in bits.

              Kinds. There are three kinds of symbols:

              •      Fields. A field symbol represents a packet header
                     or metadata field. For example, a field named
                     vlan.tci might represent the VLAN TCI field in a
                     packet.

                     A field symbol can have integer or string type.
                     Integer fields can be nominal or ordinal (see Level
                     of Measurement, below).

              •      Subfields. A subfield represents a subset of bits
                     from a larger field. For example, a field vlan.vid
                     might be defined as an alias for vlan.tci[0..11].
                     Subfields are provided for syntactic convenience,
                     because it is always possible to instead refer to a
                     subset of bits from a field directly.

                     Only ordinal fields (see Level of Measurement,
                     below) may have subfields. Subfields are always
                     ordinal.

              •      Predicates. A predicate is shorthand for a Boolean
                     expression. Predicates may be used much like 1-bit
                     fields. For example, ip4 might expand to eth.type
                     == 0x800. Predicates are provided for syntactic
                     convenience, because it is always possible to
                     instead specify the underlying expression directly.

                     A predicate whose expansion refers to any nominal
                     field or predicate (see Level of Measurement,
                     below) is nominal; other predicates have Boolean
                     level of measurement.

              Level of Measurement. See
              http://en.wikipedia.org/wiki/Level_of_measurement for the
              statistical concept on which this classification is based.
              There are three levels:

              •      Ordinal. In statistics, ordinal values can be
                     ordered on a scale. OVN considers a field (or
                     subfield) to be ordinal if its bits can be examined
                     individually. This is true for the OpenFlow fields
                     that OpenFlow or Open vSwitch makes ``maskable.’’

                     Any use of a ordinal field may specify a single bit
                     or a range of bits, e.g. vlan.tci[13..15] refers to
                     the PCP field within the VLAN TCI, and eth.dst[40]
                     refers to the multicast bit in the Ethernet
                     destination address.

                     OVN supports all the usual arithmetic relations
                     (==, !=, <, <=, >, and >=) on ordinal fields and
                     their subfields, because OVN can implement these in
                     OpenFlow and Open vSwitch as collections of bitwise
                     tests.

              •      Nominal. In statistics, nominal values cannot be
                     usefully compared except for equality. This is true
                     of OpenFlow port numbers, Ethernet types, and IP
                     protocols are examples: all of these are just
                     identifiers assigned arbitrarily with no deeper
                     meaning. In OpenFlow and Open vSwitch, bits in
                     these fields generally aren’t individually
                     addressable.

                     OVN only supports arithmetic tests for equality on
                     nominal fields, because OpenFlow and Open vSwitch
                     provide no way for a flow to efficiently implement
                     other comparisons on them. (A test for inequality
                     can be sort of built out of two flows with
                     different priorities, but OVN matching expressions
                     always generate flows with a single priority.)

                     String fields are always nominal.

              •      Boolean. A nominal field that has only two values,
                     0 and 1, is somewhat exceptional, since it is easy
                     to support both equality and inequality tests on
                     such a field: either one can be implemented as a
                     test for 0 or 1.

                     Only predicates (see above) have a Boolean level of
                     measurement.

                     This isn’t a standard level of measurement.

              Prerequisites. Any symbol can have prerequisites, which
              are additional condition implied by the use of the symbol.
              For example, For example, icmp4.type symbol might have
              prerequisite icmp4, which would cause an expression
              icmp4.type == 0 to be interpreted as icmp4.type == 0 &&
              icmp4, which would in turn expand to icmp4.type == 0 &&
              eth.type == 0x800 && ip4.proto == 1 (assuming icmp4 is a
              predicate defined as suggested under Types above).

              Relational operators

              All of the standard relational operators ==, !=, <, <=, >,
              and >= are supported. Nominal fields support only == and
              !=, and only in a positive sense when outer ! are taken
              into account, e.g. given string field inport, inport ==
              "eth0" and !(inport != "eth0") are acceptable, but not
              inport != "eth0".

              The implementation of == (or != when it is negated), is
              more efficient than that of the other relational
              operators.

              Constants

              Integer constants may be expressed in decimal, hexadecimal
              prefixed by 0x, or as dotted-quad IPv4 addresses, IPv6
              addresses in their standard forms, or Ethernet addresses
              as colon-separated hex digits. A constant in any of these
              forms may be followed by a slash and a second constant
              (the mask) in the same form, to form a masked constant.
              IPv4 and IPv6 masks may be given as integers, to express
              CIDR prefixes.

              String constants have the same syntax as quoted strings in
              JSON (thus, they are Unicode strings).

              Some operators support sets of constants written inside
              curly braces { ... }. Commas between elements of a set,
              and after the last elements, are optional. With ==,
              ``field == { constant1, constant2, ... }’’ is syntactic
              sugar for ``field == constant1 || field == constant2 ||
              .... Similarly, ``field != { constant1, constant2, ... }’’
              is equivalent to ``field != constant1 && field !=
              constant2 && ...’’.

              You may refer to a set of IPv4, IPv6, or MAC addresses
              stored in the Address_Set table by its name. An
              Address_Set with a name of set1 can be referred to as
              $set1.

              You may refer to a group of logical switch ports stored in
              the Port_Group table by its name. An Port_Group with a
              name of port_group1 can be referred to as @port_group1.

              Additionally, you may refer to the set of addresses
              belonging to a group of logical switch ports stored in the
              Port_Group table by its name followed by a suffix
              ’_ip4’/’_ip6’. The IPv4 address set of a Port_Group with a
              name of port_group1 can be referred to as
              $port_group1_ip4, and the IPv6 address set of the same
              Port_Group can be referred to as $port_group1_ip6

              Miscellaneous

              Comparisons may name the symbol or the constant first,
              e.g. tcp.src == 80 and 80 == tcp.src are both acceptable.

              Tests for a range may be expressed using a syntax like
              1024 <= tcp.src <= 49151, which is equivalent to 1024 <=
              tcp.src && tcp.src <= 49151.

              For a one-bit field or predicate, a mention of its name is
              equivalent to symobl == 1, e.g. vlan.present is equivalent
              to vlan.present == 1. The same is true for one-bit
              subfields, e.g. vlan.tci[12]. There is no technical
              limitation to implementing the same for ordinal fields of
              all widths, but the implementation is expensive enough
              that the syntax parser requires writing an explicit
              comparison against zero to make mistakes less likely, e.g.
              in tcp.src != 0 the comparison against 0 is required.

              Operator precedence is as shown below, from highest to
              lowest. There are two exceptions where parentheses are
              required even though the table would suggest that they are
              not: && and || require parentheses when used together, and
              ! requires parentheses when applied to a relational
              expression. Thus, in (eth.type == 0x800 || eth.type ==
              0x86dd) && ip.proto == 6 or !(arp.op == 1), the
              parentheses are mandatory.

              •      ()==   !=   <   <=   >   >=!&&   ||

              Comments may be introduced by //, which extends to the
              next new-line. Comments within a line may be bracketed by
              /* and */. Multiline comments are not supported.

              Symbols

              Most of the symbols below have integer type. Only inport
              and outport have string type. inport names a logical port.
              Thus, its value is a logical_port name from the
              Port_Binding table. outport may name a logical port, as
              inport, or a logical multicast group defined in the
              Multicast_Group table. For both symbols, only names within
              the flow’s logical datapath may be used.

              The regX symbols are 32-bit integers. The xxregX symbols
              are 128-bit integers, which overlay four of the 32-bit
              registers: xxreg0 overlays reg0 through reg3, with reg0
              supplying the most-significant bits of xxreg0 and reg3 the
              least-signficant. xxreg1 similarly overlays reg4 through
              reg7.

              •      reg0...reg9xxreg0 xxreg1inport outportflags.loopbacketh.src eth.dst eth.typevlan.tci vlan.vid vlan.pcp vlan.presentip.proto ip.dscp ip.ecn ip.ttl ip.fragip4.src ip4.dstip6.src ip6.dst ip6.labelarp.op arp.spa arp.tpa arp.sha arp.thatcp.src tcp.dst tcp.flagsudp.src udp.dstsctp.src sctp.dsticmp4.type icmp4.codeicmp6.type icmp6.codend.target nd.sll nd.tllct_mark ct_labelct_state, which has several Boolean subfields. The
                     ct_next action initializes the following subfields:

                     •      ct.trk: Always set to true by ct_next to
                            indicate that connection tracking has taken
                            place. All other ct subfields have ct.trk as
                            a prerequisite.

                     •      ct.new: True for a new flow

                     •      ct.est: True for an established flow

                     •      ct.rel: True for a related flow

                     •      ct.rpl: True for a reply flow

                     •      ct.inv: True for a connection entry in a bad
                            state

                     The ct_dnat, ct_snat, and ct_lb actions initialize
                     the following subfields:

                     •      ct.dnat: True for a packet whose destination
                            IP address has been changed.

                     •      ct.snat: True for a packet whose source IP
                            address has been changed.

              The following predicates are supported:

              •      eth.bcast expands to eth.dst == ff:ff:ff:ff:ff:ffeth.mcast expands to eth.dst[40]vlan.present expands to vlan.tci[12]ip4 expands to eth.type == 0x800ip4.mcast expands to ip4.dst[28..31] == 0xeip6 expands to eth.type == 0x86ddip expands to ip4 || ip6icmp4 expands to ip4 && ip.proto == 1icmp6 expands to ip6 && ip.proto == 58icmp expands to icmp4 || icmp6ip.is_frag expands to ip.frag[0]ip.later_frag expands to ip.frag[1]ip.first_frag expands to ip.is_frag &&
                     !ip.later_fragarp expands to eth.type == 0x806nd expands to icmp6.type == {135, 136} &&
                     icmp6.code == 0 && ip.ttl == 255nd_ns expands to icmp6.type == 135 && icmp6.code ==
                     0 && ip.ttl == 255nd_na expands to icmp6.type == 136 && icmp6.code ==
                     0 && ip.ttl == 255nd_rs expands to icmp6.type == 133 && icmp6.code ==
                     0 && ip.ttl == 255nd_ra expands to icmp6.type == 134 && icmp6.code ==
                     0 && ip.ttl == 255tcp expands to ip.proto == 6udp expands to ip.proto == 17sctp expands to ip.proto == 132

       actions: string
              Logical datapath actions, to be executed when the logical
              flow represented by this row is the highest-priority
              match.

              Actions share lexical syntax with the match column. An
              empty set of actions (or one that contains just white
              space or comments), or a set of actions that consists of
              just drop;, causes the matched packets to be dropped.
              Otherwise, the column should contain a sequence of
              actions, each terminated by a semicolon.

              The following actions are defined:

              output;
                     In the ingress pipeline, this action executes the
                     egress pipeline as a subroutine. If outport names a
                     logical port, the egress pipeline executes once; if
                     it is a multicast group, the egress pipeline runs
                     once for each logical port in the group.

                     In the egress pipeline, this action performs the
                     actual output to the outport logical port. (In the
                     egress pipeline, outport never names a multicast
                     group.)

                     By default, output to the input port is implicitly
                     dropped, that is, output becomes a no-op if outport
                     == inport. Occasionally it may be useful to
                     override this behavior, e.g. to send an ARP reply
                     to an ARP request; to do so, use flags.loopback = 1
                     to allow the packet to "hair-pin" back to the input
                     port.

              next;
              next(table);
              next(pipeline=pipeline, table=table);
                   Executes the given logical datapath table in pipeline
                   as a subroutine. The default table is just after the
                   current one. If pipeline is specified, it may be
                   ingress or egress; the default pipeline is the one
                   currently executing. Actions in the ingress pipeline
                   may not use next to jump into the egress pipeline
                   (use the output instead), but transitions in the
                   opposite direction are allowed.

              field = constant;
                   Sets data or metadata field field to constant value
                   constant, e.g. outport = "vif0"; to set the logical
                   output port. To set only a subset of bits in a field,
                   specify a subfield for field or a masked constant,
                   e.g. one may use vlan.pcp[2] = 1; or vlan.pcp = 4/4;
                   to set the most sigificant bit of the VLAN PCP.

                   Assigning to a field with prerequisites implicitly
                   adds those prerequisites to match; thus, for example,
                   a flow that sets tcp.dst applies only to TCP flows,
                   regardless of whether its match mentions any TCP
                   field.

                   Not all fields are modifiable (e.g. eth.type and
                   ip.proto are read-only), and not all modifiable
                   fields may be partially modified (e.g. ip.ttl must
                   assigned as a whole). The outport field is modifiable
                   in the ingress pipeline but not in the egress
                   pipeline.

              ovn_field = constant;
                   Sets OVN field ovn_field to constant value constant.

                   OVN supports setting the values of certain fields
                   which are not yet supported in OpenFlow to set or
                   modify them.

                   Below are the supported OVN fields:

                   •      icmp4.frag_mtu

                          This field sets the low-order 16 bits of the
                          ICMP4 header field that is labelled "unused"
                          in the ICMP specification as defined in the
                          RFC 1191 with the value specified in constant.

                          Eg. icmp4.frag_mtu = 1500;

              field1 = field2;
                   Sets data or metadata field field1 to the value of
                   data or metadata field field2, e.g. reg0 = ip4.src;
                   copies ip4.src into reg0. To modify only a subset of
                   a field’s bits, specify a subfield for field1 or
                   field2 or both, e.g. vlan.pcp = reg0[0..2]; copies
                   the least-significant bits of reg0 into the VLAN PCP.

                   field1 and field2 must be the same type, either both
                   string or both integer fields. If they are both
                   integer fields, they must have the same width.

                   If field1 or field2 has prerequisites, they are added
                   implicitly to match. It is possible to write an
                   assignment with contradictory prerequisites, such as
                   ip4.src = ip6.src[0..31];, but the contradiction
                   means that a logical flow with such an assignment
                   will never be matched.

              field1 <-> field2;
                   Similar to field1 = field2; except that the two
                   values are exchanged instead of copied. Both field1
                   and field2 must modifiable.

              ip.ttl--;
                   Decrements the IPv4 or IPv6 TTL. If this would make
                   the TTL zero or negative, then processing of the
                   packet halts; no further actions are processed. (To
                   properly handle such cases, a higher-priority flow
                   should match on ip.ttl == {0, 1};.)

                   Prerequisite: ip

              ct_next;
                   Apply connection tracking to the flow, initializing
                   ct_state for matching in later tables. Automatically
                   moves on to the next table, as if followed by next.

                   As a side effect, IP fragments will be reassembled
                   for matching. If a fragmented packet is output, then
                   it will be sent with any overlapping fragments
                   squashed. The connection tracking state is scoped by
                   the logical port when the action is used in a flow
                   for a logical switch, so overlapping addresses may be
                   used. To allow traffic related to the matched flow,
                   execute ct_commit . Connection tracking state is
                   scoped by the logical topology when the action is
                   used in a flow for a router.

                   It is possible to have actions follow ct_next, but
                   they will not have access to any of its side-effects
                   and is not generally useful.

              ct_commit;
              ct_commit(ct_mark=value[/mask]);
              ct_commit(ct_label=value[/mask]);
              ct_commit(ct_mark=value[/mask], ct_label=value[/mask]);
                   Commit the flow to the connection tracking entry
                   associated with it by a previous call to ct_next.
                   When ct_mark=value[/mask] and/or
                   ct_label=value[/mask] are supplied, ct_mark and/or
                   ct_label will be set to the values indicated by
                   value[/mask] on the connection tracking entry.
                   ct_mark is a 32-bit field. ct_label is a 128-bit
                   field. The value[/mask] should be specified in hex
                   string if more than 64bits are to be used.

                   Note that if you want processing to continue in the
                   next table, you must execute the next action after
                   ct_commit. You may also leave out next which will
                   commit connection tracking state, and then drop the
                   packet. This could be useful for setting ct_mark on a
                   connection tracking entry before dropping a packet,
                   for example.

              ct_dnat;
              ct_dnat(IP);
                   ct_dnat sends the packet through the DNAT zone in
                   connection tracking table to unDNAT any packet that
                   was DNATed in the opposite direction. The packet is
                   then automatically sent to to the next tables as if
                   followed by next; action. The next tables will see
                   the changes in the packet caused by the connection
                   tracker.

                   ct_dnat(IP) sends the packet through the DNAT zone to
                   change the destination IP address of the packet to
                   the one provided inside the parentheses and commits
                   the connection. The packet is then automatically sent
                   to the next tables as if followed by next; action.
                   The next tables will see the changes in the packet
                   caused by the connection tracker.

              ct_snat;
              ct_snat(IP);
                   ct_snat sends the packet through the SNAT zone to
                   unSNAT any packet that was SNATed in the opposite
                   direction. The packet is automatically sent to the
                   next tables as if followed by the next; action. The
                   next tables will see the changes in the packet caused
                   by the connection tracker.

                   ct_snat(IP) sends the packet through the SNAT zone to
                   change the source IP address of the packet to the one
                   provided inside the parenthesis and commits the
                   connection. The packet is then automatically sent to
                   the next tables as if followed by next; action. The
                   next tables will see the changes in the packet caused
                   by the connection tracker.

              ct_clear;
                   Clears connection tracking state.

              clone { action; ... };
                   Makes a copy of the packet being processed and
                   executes each action on the copy. Actions following
                   the clone action, if any, apply to the original,
                   unmodified packet. This can be used as a way to
                   ``save and restore’’ the packet around a set of
                   actions that may modify it and should not persist.

              arp { action; ... };
                   Temporarily replaces the IPv4 packet being processed
                   by an ARP packet and executes each nested action on
                   the ARP packet. Actions following the arp action, if
                   any, apply to the original, unmodified packet.

                   The ARP packet that this action operates on is
                   initialized based on the IPv4 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change:

                   •      eth.src unchanged

                   •      eth.dst unchanged

                   •      eth.type = 0x0806arp.op = 1 (ARP request)

                   •      arp.sha copied from eth.srcarp.spa copied from ip4.srcarp.tha = 00:00:00:00:00:00arp.tpa copied from ip4.dst

                   The ARP packet has the same VLAN header, if any, as
                   the IP packet it replaces.

                   Prerequisite: ip4

              get_arp(P, A);
                   Parameters: logical port string field P, 32-bit IP
                   address field A.

                   Looks up A in P’s mac binding table. If an entry is
                   found, stores its Ethernet address in eth.dst,
                   otherwise stores 00:00:00:00:00:00 in eth.dst.

                   Example: get_arp(outport, ip4.dst);

              put_arp(P, A, E);
                   Parameters: logical port string field P, 32-bit IP
                   address field A, 48-bit Ethernet address field E.

                   Adds or updates the entry for IP address A in logical
                   port P’s mac binding table, setting its Ethernet
                   address to E.

                   Example: put_arp(inport, arp.spa, arp.sha);

              nd_ns { action; ... };
                   Temporarily replaces the IPv6 packet being processed
                   by an IPv6 Neighbor Solicitation packet and executes
                   each nested action on the IPv6 NS packet. Actions
                   following the nd_ns action, if any, apply to the
                   original, unmodified packet.

                   The IPv6 NS packet that this action operates on is
                   initialized based on the IPv6 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change:

                   •      eth.src unchanged

                   •      eth.dst set to IPv6 multicast MAC address

                   •      eth.type = 0x86ddip6.src copied from ip6.srcip6.dst set to IPv6 Solicited-Node multicast
                          address

                   •      icmp6.type = 135 (Neighbor Solicitation)

                   •      nd.target copied from ip6.dst

                   The IPv6 NS packet has the same VLAN header, if any,
                   as the IP packet it replaces.

                   Prerequisite: ip6

              nd_na { action; ... };
                   Temporarily replaces the IPv6 neighbor solicitation
                   packet being processed by an IPv6 neighbor
                   advertisement (NA) packet and executes each nested
                   action on the NA packet. Actions following the nd_na
                   action, if any, apply to the original, unmodified
                   packet.

                   The NA packet that this action operates on is
                   initialized based on the IPv6 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change:

                   •      eth.dst exchanged with eth.srceth.type = 0x86ddip6.dst copied from ip6.srcip6.src copied from nd.targeticmp6.type = 136 (Neighbor Advertisement)

                   •      nd.target unchanged

                   •      nd.sll = 00:00:00:00:00:00nd.tll copied from eth.dst

                   The ND packet has the same VLAN header, if any, as
                   the IPv6 packet it replaces.

                   Prerequisite: nd_ns

              nd_na_router { action; ... };
                   Temporarily replaces the IPv6 neighbor solicitation
                   packet being processed by an IPv6 neighbor
                   advertisement (NA) packet, sets ND_NSO_ROUTER in the
                   RSO flags and executes each nested action on the NA
                   packet. Actions following the nd_na_router action, if
                   any, apply to the original, unmodified packet.

                   The NA packet that this action operates on is
                   initialized based on the IPv6 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change:

                   •      eth.dst exchanged with eth.srceth.type = 0x86ddip6.dst copied from ip6.srcip6.src copied from nd.targeticmp6.type = 136 (Neighbor Advertisement)

                   •      nd.target unchanged

                   •      nd.sll = 00:00:00:00:00:00nd.tll copied from eth.dst

                   The ND packet has the same VLAN header, if any, as
                   the IPv6 packet it replaces.

                   Prerequisite: nd_ns

              get_nd(P, A);
                   Parameters: logical port string field P, 128-bit IPv6
                   address field A.

                   Looks up A in P’s mac binding table. If an entry is
                   found, stores its Ethernet address in eth.dst,
                   otherwise stores 00:00:00:00:00:00 in eth.dst.

                   Example: get_nd(outport, ip6.dst);

              put_nd(P, A, E);
                   Parameters: logical port string field P, 128-bit IPv6
                   address field A, 48-bit Ethernet address field E.

                   Adds or updates the entry for IPv6 address A in
                   logical port P’s mac binding table, setting its
                   Ethernet address to E.

                   Example: put_nd(inport, nd.target, nd.tll);

              R = put_dhcp_opts(D1 = V1, D2 = V2, ..., Dn = Vn);
                   Parameters: one or more DHCP option/value pairs,
                   which must include an offerip option (with code 0).

                   Result: stored to a 1-bit subfield R.

                   Valid only in the ingress pipeline.

                   When this action is applied to a DHCP request packet
                   (DHCPDISCOVER or DHCPREQUEST), it changes the packet
                   into a DHCP reply (DHCPOFFER or DHCPACK,
                   respectively), replaces the options by those
                   specified as parameters, and stores 1 in R.

                   When this action is applied to a non-DHCP packet or a
                   DHCP packet that is not DHCPDISCOVER or DHCPREQUEST,
                   it leaves the packet unchanged and stores 0 in R.

                   The contents of the DHCP_Option table control the
                   DHCP option names and values that this action
                   supports.

                   Example: reg0[0] = put_dhcp_opts(offerip = 10.0.0.2,
                   router = 10.0.0.1, netmask = 255.255.255.0,
                   dns_server = {8.8.8.8, 7.7.7.7});

              R = put_dhcpv6_opts(D1 = V1, D2 = V2, ..., Dn = Vn);
                   Parameters: one or more DHCPv6 option/value pairs.

                   Result: stored to a 1-bit subfield R.

                   Valid only in the ingress pipeline.

                   When this action is applied to a DHCPv6 request
                   packet, it changes the packet into a DHCPv6 reply,
                   replaces the options by those specified as
                   parameters, and stores 1 in R.

                   When this action is applied to a non-DHCPv6 packet or
                   an invalid DHCPv6 request packet , it leaves the
                   packet unchanged and stores 0 in R.

                   The contents of the DHCPv6_Options table control the
                   DHCPv6 option names and values that this action
                   supports.

                   Example: reg0[3] = put_dhcpv6_opts(ia_addr = aef0::4,
                   server_id = 00:00:00:00:10:02,
                   dns_server={ae70::1,ae70::2});

              set_queue(queue_number);
                   Parameters: Queue number queue_number, in the range 0
                   to 61440.

                   This is a logical equivalent of the OpenFlow
                   set_queue action. It affects packets that egress a
                   hypervisor through a physical interface. For nonzero
                   queue_number, it configures packet queuing to match
                   the settings configured for the Port_Binding with
                   options:qdisc_queue_id matching queue_number. When
                   queue_number is zero, it resets queuing to the
                   default strategy.

                   Example: set_queue(10);

              ct_lb;
              ct_lb(ip[:port]...);
                   With one or more arguments, ct_lb commits the packet
                   to the connection tracking table and DNATs the
                   packet’s destination IP address (and port) to the IP
                   address or addresses (and optional ports) specified
                   in the string. If multiple comma-separated IP
                   addresses are specified, each is given equal weight
                   for picking the DNAT address. Processing
                   automatically moves on to the next table, as if next;
                   were specified, and later tables act on the packet as
                   modified by the connection tracker. Connection
                   tracking state is scoped by the logical port when the
                   action is used in a flow for a logical switch, so
                   overlapping addresses may be used. Connection
                   tracking state is scoped by the logical topology when
                   the action is used in a flow for a router.

                   Without arguments, ct_lb sends the packet to the
                   connection tracking table to NAT the packets. If the
                   packet is part of an established connection that was
                   previously committed to the connection tracker via
                   ct_lb(...), it will automatically get DNATed to the
                   same IP address as the first packet in that
                   connection.

              R = dns_lookup();
                   Parameters: No parameters.

                   Result: stored to a 1-bit subfield R.

                   Valid only in the ingress pipeline.

                   When this action is applied to a valid DNS request (a
                   UDP packet typically directed to port 53), it
                   attempts to resolve the query using the contents of
                   the DNS table. If it is successful, it changes the
                   packet into a DNS reply and stores 1 in R. If the
                   action is applied to a non-DNS packet, an invalid DNS
                   request packet, or a valid DNS request for which the
                   DNS table does not supply an answer, it leaves the
                   packet unchanged and stores 0 in R.

                   Regardless of success, the action does not make any
                   of the changes to the flow that are necessary to
                   direct the packet back to the requester. The logical
                   pipeline can implement this behavior with matches and
                   actions in later tables.

                   Example: reg0[3] = dns_lookup();

                   Prerequisite: udp

              R = put_nd_ra_opts(D1 = V1, D2 = V2, ..., Dn = Vn);
                   Parameters: The following IPv6 ND Router
                   Advertisement option/value pairs as defined in RFC
                   4861.

                   •      addr_mode

                          Mandatory parameter which specifies the
                          address mode flag to be set in the RA flag
                          options field. The value of this option is a
                          string and the following values can be defined
                          - "slaac", "dhcpv6_stateful" and
                          "dhcpv6_stateless".

                   •      slla

                          Mandatory parameter which specifies the link-
                          layer address of the interface from which the
                          Router Advertisement is sent.

                   •      mtu

                          Optional parameter which specifies the MTU.

                   •      prefix

                          Optional parameter which should be specified
                          if the addr_mode is "slaac" or
                          "dhcpv6_stateless". The value should be an
                          IPv6 prefix which will be used for stateless
                          IPv6 address configuration. This option can be
                          defined multiple times.

                   Result: stored to a 1-bit subfield R.

                   Valid only in the ingress pipeline.

                   When this action is applied to an IPv6 Router
                   solicitation request packet, it changes the packet
                   into an IPv6 Router Advertisement reply and adds the
                   options specified in the parameters, and stores 1 in
                   R.

                   When this action is applied to a non-IPv6 Router
                   solicitation packet or an invalid IPv6 request packet
                   , it leaves the packet unchanged and stores 0 in R.

                   Example: reg0[3] = put_nd_ra_opts(addr_mode =
                   "slaac", slla = 00:00:00:00:10:02, prefix =
                   aef0::/64, mtu = 1450);

              set_meter(rate);
              set_meter(rate, burst);
                   Parameters: rate limit int field rate in kbps, burst
                   rate limits int field burst in kbps.

                   This action sets the rate limit for a flow.

                   Example: set_meter(100, 1000);

              R = check_pkt_larger(L)
                   Parameters: packet length L to check for in bytes.

                   Result: stored to a 1-bit subfield R.

                   This is a logical equivalent of the OpenFlow
                   check_pkt_larger action. If the packet is larger than
                   the length specified in L, it stores 1 in the
                   subfield R.

                   Example: reg0[6] = check_pkt_larger(1000);

              log(key=value, ...);
                     Causes ovn-controller to log the packet on the
                     chassis that processes it. Packet logging currently
                     uses the same logging mechanism as other Open
                     vSwitch and OVN messages, which means that whether
                     and where log messages appear depends on the local
                     logging configuration that can be configured with
                     ovs-appctl, etc.

                     The log action takes zero or more of the following
                     key-value pair arguments that control what is
                     logged:

                     name=string
                            An optional name for the ACL. The string is
                            currently limited to 64 bytes.

                     severity=level
                            Indicates the severity of the event. The
                            level is one of following (from more to less
                            serious): alert, warning, notice, info, or
                            debug. If a severity is not provided, the
                            default is info.

                     verdict=value
                            The verdict for packets matching the flow.
                            The value must be one of allow, deny, or
                            reject.

                     meter=string
                            An optional rate-limiting meter to be
                            applied to the logs. The string should
                            reference a name entry from the Meter table.
                            The only meter action that is appriopriate
                            is drop.

              icmp4 { action; ... };
              icmp4_error { action; ... };
                   Temporarily replaces the IPv4 packet being processed
                   by an ICMPv4 packet and executes each nested action
                   on the ICMPv4 packet. Actions following these
                   actions, if any, apply to the original, unmodified
                   packet.

                   The ICMPv4 packet that these actions operates on is
                   initialized based on the IPv4 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change. Ethernet and
                   IPv4 fields not listed here are not changed:

                   •      ip.proto = 1 (ICMPv4)

                   •      ip.frag = 0 (not a fragment)

                   •      ip.ttl = 255icmp4.type = 3 (destination unreachable)

                   •      icmp4.code = 1 (host unreachable)

                   icmp4_error action is expected to be used to generate
                   an ICMPv4 packet in response to an error in original
                   IP packet. When this action generates the ICMPv4
                   packet, it also copies the original IP datagram
                   following the ICMPv4 header as per RFC 1122: 3.2.2.

                   Prerequisite: ip4

              icmp6 { action; ... };
                   Temporarily replaces the IPv6 packet being processed
                   by an ICMPv6 packet and executes each nested action
                   on the ICMPv6 packet. Actions following the icmp6
                   action, if any, apply to the original, unmodified
                   packet.

                   The ICMPv6 packet that this action operates on is
                   initialized based on the IPv6 packet being processed,
                   as follows. These are default values that the nested
                   actions will probably want to change. Ethernet and
                   IPv6 fields not listed here are not changed:

                   •      ip.proto = 58 (ICMPv6)

                   •      ip.ttl = 255icmp6.type = 1 (destination unreachable)

                   •      icmp6.code = 1 (administratively prohibited)

                   Prerequisite: ip6

              tcp_reset;
                   This action transforms the current TCP packet
                   according to the following pseudocode:

                   if (tcp.ack) {
                           tcp.seq = tcp.ack;
                   } else {
                           tcp.ack = tcp.seq + length(tcp.payload);
                           tcp.seq = 0;
                   }
                   tcp.flags = RST;

                   Then, the action drops all TCP options and payload
                   data, and updates the TCP checksum. IP ttl is set to
                   255.

                   Prerequisite: tcp

              trigger_event;
                   This action is used to allow ovs-vswitchd to report
                   CMS related events writing them in Controller_Event
                   table. Supported event:

                   •      empty_lb_backends. This event is raised if a
                          received packet is destined for a load
                          balancer VIP that has no configured backend
                          destinations. For this event, the event info
                          includes the load balancer VIP, the load
                          balancer UUID, and the transport protocol.

              igmp;
                   This action sends the packet to ovn-controller for
                   multicast snooping.

                   Prerequisite: igmp

       external_ids : stage-name: optional string
              Human-readable name for this flow’s stage in the pipeline.

       external_ids : stage-hint: optional string, containing an uuid
              UUID of a OVN_Northbound record that caused this logical
              flow to be created. Currently used only for attribute of
              logical flows to northbound ACL records.

       external_ids : source: optional string
              Source file and line number of the code that added this
              flow to the pipeline.

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

Multicast_Group TABLE         top

       The rows in this table define multicast groups of logical ports.
       Multicast groups allow a single packet transmitted over a tunnel
       to a hypervisor to be delivered to multiple VMs on that
       hypervisor, which uses bandwidth more efficiently.

       Each row in this table defines a logical multicast group numbered
       tunnel_key within datapath, whose logical ports are listed in the
       ports column.

   Summary:
       datapath                      Datapath_Binding
       tunnel_key                    integer, in range 32,768 to 65,535
       name                          string
       ports                         set of 1 or more weak reference to
                                     Port_Bindings

   Details:
       datapath: Datapath_Binding
              The logical datapath in which the multicast group resides.

       tunnel_key: integer, in range 32,768 to 65,535
              The value used to designate this logical egress port in
              tunnel encapsulations. An index forces the key to be
              unique within the datapath. The unusual range ensures that
              multicast group IDs do not overlap with logical port IDs.

       name: string
              The logical multicast group’s name. An index forces the
              name to be unique within the datapath. Logical flows in
              the ingress pipeline may output to the group just as for
              individual logical ports, by assigning the group’s name to
              outport and executing an output action.

              Multicast group names and logical port names share a
              single namespace and thus should not overlap (but the
              database schema cannot enforce this). To try to avoid
              conflicts, ovn-northd uses names that begin with _MC_.

       ports: set of 1 or more weak reference to Port_Bindings
              The logical ports included in the multicast group. All of
              these ports must be in the datapath logical datapath (but
              the database schema cannot enforce this).

Meter TABLE         top

       Each row in this table represents a meter that can be used for
       QoS or rate-limiting.

   Summary:
       name                          string (must be unique within
                                     table)
       unit                          string, either kbps or pktps
       bands                         set of 1 or more Meter_Bands

   Details:
       name: string (must be unique within table)
              A name for this meter.

              Names that begin with "__" (two underscores) are reserved
              for OVN internal use and should not be added manually.

       unit: string, either kbps or pktps
              The unit for rate and burst_rate parameters in the bands
              entry. kbps specifies kilobits per second, and pktps
              specifies packets per second.

       bands: set of 1 or more Meter_Bands
              The bands associated with this meter. Each band specifies
              a rate above which the band is to take the action action.
              If multiple bands’ rates are exceeded, then the band with
              the highest rate among the exceeded bands is selected.

Meter_Band TABLE         top

       Each row in this table represents a meter band which specifies
       the rate above which the configured action should be applied.
       These bands are referenced by the bands column in the Meter
       table.

   Summary:
       action                        string, must be drop
       rate                          integer, in range 1 to
                                     4,294,967,295
       burst_size                    integer, in range 0 to
                                     4,294,967,295

   Details:
       action: string, must be drop
              The action to execute when this band matches. The only
              supported action is drop.

       rate: integer, in range 1 to 4,294,967,295
              The rate limit for this band, in kilobits per second or
              bits per second, depending on whether the parent Meter
              entry’s unit column specified kbps or pktps.

       burst_size: integer, in range 0 to 4,294,967,295
              The maximum burst allowed for the band in kilobits or
              packets, depending on whether kbps or pktps was selected
              in the parent Meter entry’s unit column. If the size is
              zero, the switch is free to select some reasonable value
              depending on its configuration.

Datapath_Binding TABLE         top

       Each row in this table represents a logical datapath, which
       implements a logical pipeline among the ports in the Port_Binding
       table associated with it. In practice, the pipeline in a given
       logical datapath implements either a logical switch or a logical
       router.

       The main purpose of a row in this table is provide a physical
       binding for a logical datapath. A logical datapath does not have
       a physical location, so its physical binding information is
       limited: just tunnel_key. The rest of the data in this table does
       not affect packet forwarding.

   Summary:
       tunnel_key                    integer, in range 1 to 16,777,215
                                     (must be unique within table)
       OVN_Northbound Relationship:
         external_ids : logical-switch
                                     optional string, containing an uuid
         external_ids : logical-router
                                     optional string, containing an uuid
         Naming:
            external_ids : name      optional string
            external_ids : name2     optional string
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       tunnel_key: integer, in range 1 to 16,777,215 (must be unique
       within table)
              The tunnel key value to which the logical datapath is
              bound. The Tunnel Encapsulation section in
              ovn-architecture(7) describes how tunnel keys are
              constructed for each supported encapsulation.

     OVN_Northbound Relationship:

       Each row in Datapath_Binding is associated with some logical
       datapath. ovn-northd uses these keys to track the association of
       a logical datapath with concepts in the OVN_Northbound database.

       external_ids : logical-switch: optional string, containing an
       uuid
              For a logical datapath that represents a logical switch,
              ovn-northd stores in this key the UUID of the
              corresponding Logical_Switch row in the OVN_Northbound
              database.

       external_ids : logical-router: optional string, containing an
       uuid
              For a logical datapath that represents a logical router,
              ovn-northd stores in this key the UUID of the
              corresponding Logical_Router row in the OVN_Northbound
              database.

     Naming:

       ovn-northd copies these from the name fields in the
       OVN_Northbound database, either from name and
       external_ids:neutron:router_name in the Logical_Router table or
       from name and external_ids:neutron:network_name in the
       Logical_Switch table.

       external_ids : name: optional string
              A name for the logical datapath.

       external_ids : name2: optional string
              Another name for the logical datapath.

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

Port_Binding TABLE         top

       Each row in this table binds a logical port to a realization. For
       most logical ports, this means binding to some physical location,
       for example by binding a logical port to a VIF that belongs to a
       VM running on a particular hypervisor. Other logical ports, such
       as logical patch ports, can be realized without a specific
       physical location, but their bindings are still expressed through
       rows in this table.

       For every Logical_Switch_Port record in OVN_Northbound database,
       ovn-northd creates a record in this table. ovn-northd populates
       and maintains every column except the chassis column, which it
       leaves empty in new records.

       ovn-controller/ovn-controller-vtep populates the chassis column
       for the records that identify the logical ports that are located
       on its hypervisor/gateway, which
       ovn-controller/ovn-controller-vtep in turn finds out by
       monitoring the local hypervisor’s Open_vSwitch database, which
       identifies logical ports via the conventions described in
       IntegrationGuide.rst. (The exceptions are for Port_Binding
       records with type of l3gateway, whose locations are identified by
       ovn-northd via the options:l3gateway-chassis column in this
       table. ovn-controller is still responsible to populate the
       chassis column.)

       When a chassis shuts down gracefully, it should clean up the
       chassis column that it previously had populated. (This is not
       critical because resources hosted on the chassis are equally
       unreachable regardless of whether their rows are present.) To
       handle the case where a VM is shut down abruptly on one chassis,
       then brought up again on a different one,
       ovn-controller/ovn-controller-vtep must overwrite the chassis
       column with new information.

   Summary:
       Core Features:
         datapath                    Datapath_Binding
         logical_port                string (must be unique within
                                     table)
         encap                       optional weak reference to Encap
         chassis                     optional weak reference to Chassis
         gateway_chassis             set of Gateway_Chassiss
         ha_chassis_group            optional HA_Chassis_Group
         tunnel_key                  integer, in range 1 to 32,767
         mac                         set of strings
         type                        string
       Patch Options:
         options : peer              optional string
         nat_addresses               set of strings
       L3 Gateway Options:
         options : peer              optional string
         options : l3gateway-chassis
                                     optional string
         options : nat-addresses     optional string
         nat_addresses               set of strings
       Localnet Options:
         options : network_name      optional string
         tag                         optional integer, in range 1 to
                                     4,095
       L2 Gateway Options:
         options : network_name      optional string
         options : l2gateway-chassis
                                     optional string
         tag                         optional integer, in range 1 to
                                     4,095
       VTEP Options:
         options : vtep-physical-switch
                                     optional string
         options : vtep-logical-switch
                                     optional string
       VMI (or VIF) Options:
         options : requested-chassis
                                     optional string
         options : qos_max_rate      optional string
         options : qos_burst         optional string
         options : qdisc_queue_id    optional string, containing an
                                     integer, in range 1 to 61,440
       Chassis Redirect Options:
         options : distributed-port  optional string
         options : redirect-chassis  optional string
       Nested Containers:
         parent_port                 optional string
         tag                         optional integer, in range 1 to
                                     4,095
       Naming:
         external_ids : name         optional string
       Common Columns:
         external_ids                map of string-string pairs

   Details:
     Core Features:

       datapath: Datapath_Binding
              The logical datapath to which the logical port belongs.

       logical_port: string (must be unique within table)
              A logical port, taken from name in the OVN_Northbound
              database’s Logical_Switch_Port table. OVN does not
              prescribe a particular format for the logical port ID.

       encap: optional weak reference to Encap
              Points to supported encapsulation configurations to
              transmit logical dataplane packets to this chassis. Each
              entry is a Encap record that describes the configuration.

       chassis: optional weak reference to Chassis
              The meaning of this column depends on the value of the
              type column. This is the meaning for each type

              (empty string)
                     The physical location of the logical port. To
                     successfully identify a chassis, this column must
                     be a Chassis record. This is populated by
                     ovn-controller.

              vtep   The physical location of the hardware_vtep gateway.
                     To successfully identify a chassis, this column
                     must be a Chassis record. This is populated by
                     ovn-controller-vtep.

              localnet
                     Always empty. A localnet port is realized on every
                     chassis that has connectivity to the corresponding
                     physical network.

              localport
                     Always empty. A localport port is present on every
                     chassis.

              l3gateway
                     The physical location of the L3 gateway. To
                     successfully identify a chassis, this column must
                     be a Chassis record. This is populated by
                     ovn-controller based on the value of the
                     options:l3gateway-chassis column in this table.

              l2gateway
                     The physical location of this L2 gateway. To
                     successfully identify a chassis, this column must
                     be a Chassis record. This is populated by
                     ovn-controller based on the value of the
                     options:l2gateway-chassis column in this table.

       gateway_chassis: set of Gateway_Chassiss
              A list of Gateway_Chassis.

              This should only be populated for ports with type set to
              chassisredirect. This column defines the list of chassis
              used as gateways where traffic will be redirected through.

       ha_chassis_group: optional HA_Chassis_Group
              This should only be populated for ports with type set to
              chassisredirect. This column defines the HA chassis group
              with a list of HA chassis used as gateways where traffic
              will be redirected through.

       tunnel_key: integer, in range 1 to 32,767
              A number that represents the logical port in the key (e.g.
              STT key or Geneve TLV) field carried within tunnel
              protocol packets.

              The tunnel ID must be unique within the scope of a logical
              datapath.

       mac: set of strings
              The Ethernet address or addresses used as a source address
              on the logical port, each in the form xx:xx:xx:xx:xx:xx.
              The string unknown is also allowed to indicate that the
              logical port has an unknown set of (additional) source
              addresses.

              A VM interface would ordinarily have a single Ethernet
              address. A gateway port might initially only have unknown,
              and then add MAC addresses to the set as it learns new
              source addresses.

       type: string
              A type for this logical port. Logical ports can be used to
              model other types of connectivity into an OVN logical
              switch. The following types are defined:

              (empty string)
                     VM (or VIF) interface.

              patch  One of a pair of logical ports that act as if
                     connected by a patch cable. Useful for connecting
                     two logical datapaths, e.g. to connect a logical
                     router to a logical switch or to another logical
                     router.

              l3gateway
                     One of a pair of logical ports that act as if
                     connected by a patch cable across multiple chassis.
                     Useful for connecting a logical switch with a
                     Gateway router (which is only resident on a
                     particular chassis).

              localnet
                     A connection to a locally accessible network from
                     each ovn-controller instance. A logical switch can
                     only have a single localnet port attached. This is
                     used to model direct connectivity to an existing
                     network.

              localport
                     A connection to a local VIF. Traffic that arrives
                     on a localport is never forwarded over a tunnel to
                     another chassis. These ports are present on every
                     chassis and have the same address in all of them.
                     This is used to model connectivity to local
                     services that run on every hypervisor.

              l2gateway
                     An L2 connection to a physical network. The chassis
                     this Port_Binding is bound to will serve as an L2
                     gateway to the network named by
                     options:network_name.

              vtep   A port to a logical switch on a VTEP gateway
                     chassis. In order to get this port correctly
                     recognized by the OVN controller, the
                     options:vtep-physical-switch and
                     options:vtep-logical-switch must also be defined.

              chassisredirect
                     A logical port that represents a particular
                     instance, bound to a specific chassis, of an
                     otherwise distributed parent port (e.g. of type
                     patch). A chassisredirect port should never be used
                     as an inport. When an ingress pipeline sets the
                     outport, it may set the value to a logical port of
                     type chassisredirect. This will cause the packet to
                     be directed to a specific chassis to carry out the
                     egress pipeline. At the beginning of the egress
                     pipeline, the outport will be reset to the value of
                     the distributed port.

     Patch Options:

       These options apply to logical ports with type of patch.

       options : peer: optional string
              The logical_port in the Port_Binding record for the other
              side of the patch. The named logical_port must specify
              this logical_port in its own peer option. That is, the two
              patch logical ports must have reversed logical_port and
              peer values.

       nat_addresses: set of strings
              MAC address followed by a list of SNAT and DNAT external
              IP addresses, followed by is_chassis_resident("lport"),
              where lport is the name of a logical port on the same
              chassis where the corresponding NAT rules are applied.
              This is used to send gratuitous ARPs for SNAT and DNAT
              external IP addresses via localnet, from the chassis where
              lport resides. Example: 80:fa:5b:06:72:b7 158.36.44.22
              158.36.44.24 is_chassis_resident("foo1"). This would
              result in generation of gratuitous ARPs for IP addresses
              158.36.44.22 and 158.36.44.24 with a MAC address of
              80:fa:5b:06:72:b7 from the chassis where the logical port
              "foo1" resides.

     L3 Gateway Options:

       These options apply to logical ports with type of l3gateway.

       options : peer: optional string
              The logical_port in the Port_Binding record for the other
              side of the ’l3gateway’ port. The named logical_port must
              specify this logical_port in its own peer option. That is,
              the two ’l3gateway’ logical ports must have reversed
              logical_port and peer values.

       options : l3gateway-chassis: optional string
              The chassis in which the port resides.

       options : nat-addresses: optional string
              MAC address of the l3gateway port followed by a list of
              SNAT and DNAT external IP addresses. This is used to send
              gratuitous ARPs for SNAT and DNAT external IP addresses
              via localnet. Example: 80:fa:5b:06:72:b7 158.36.44.22
              158.36.44.24. This would result in generation of
              gratuitous ARPs for IP addresses 158.36.44.22 and
              158.36.44.24 with a MAC address of 80:fa:5b:06:72:b7. This
              is used in OVS versions prior to 2.8.

       nat_addresses: set of strings
              MAC address of the l3gateway port followed by a list of
              SNAT and DNAT external IP addresses. This is used to send
              gratuitous ARPs for SNAT and DNAT external IP addresses
              via localnet. Example: 80:fa:5b:06:72:b7 158.36.44.22
              158.36.44.24. This would result in generation of
              gratuitous ARPs for IP addresses 158.36.44.22 and
              158.36.44.24 with a MAC address of 80:fa:5b:06:72:b7. This
              is used in OVS version 2.8 and later versions.

     Localnet Options:

       These options apply to logical ports with type of localnet.

       options : network_name: optional string
              Required. ovn-controller uses the configuration entry
              ovn-bridge-mappings to determine how to connect to this
              network. ovn-bridge-mappings is a list of network names
              mapped to a local OVS bridge that provides access to that
              network. An example of configuring ovn-bridge-mappings
              would be: .IP
              $ ovs-vsctl set open . external-ids:ovn-bridge-mappings=physnet1:br-eth0,physnet2:br-eth1

              When a logical switch has a localnet port attached, every
              chassis that may have a local vif attached to that logical
              switch must have a bridge mapping configured to reach that
              localnet. Traffic that arrives on a localnet port is never
              forwarded over a tunnel to another chassis.

       tag: optional integer, in range 1 to 4,095
              If set, indicates that the port represents a connection to
              a specific VLAN on a locally accessible network. The VLAN
              ID is used to match incoming traffic and is also added to
              outgoing traffic.

     L2 Gateway Options:

       These options apply to logical ports with type of l2gateway.

       options : network_name: optional string
              Required. ovn-controller uses the configuration entry
              ovn-bridge-mappings to determine how to connect to this
              network. ovn-bridge-mappings is a list of network names
              mapped to a local OVS bridge that provides access to that
              network. An example of configuring ovn-bridge-mappings
              would be: .IP
              $ ovs-vsctl set open . external-ids:ovn-bridge-mappings=physnet1:br-eth0,physnet2:br-eth1

              When a logical switch has a l2gateway port attached, the
              chassis that the l2gateway port is bound to must have a
              bridge mapping configured to reach the network identified
              by network_name.

       options : l2gateway-chassis: optional string
              Required. The chassis in which the port resides.

       tag: optional integer, in range 1 to 4,095
              If set, indicates that the gateway is connected to a
              specific VLAN on the physical network. The VLAN ID is used
              to match incoming traffic and is also added to outgoing
              traffic.

     VTEP Options:

       These options apply to logical ports with type of vtep.

       options : vtep-physical-switch: optional string
              Required. The name of the VTEP gateway.

       options : vtep-logical-switch: optional string
              Required. A logical switch name connected by the VTEP
              gateway. Must be set when type is vtep.

     VMI (or VIF) Options:

       These options apply to logical ports with type having (empty
       string)

       options : requested-chassis: optional string
              If set, identifies a specific chassis (by name or
              hostname) that is allowed to bind this port. Using this
              option will prevent thrashing between two chassis trying
              to bind the same port during a live migration. It can also
              prevent similar thrashing due to a mis-configuration, if a
              port is accidentally created on more than one chassis.

       options : qos_max_rate: optional string
              If set, indicates the maximum rate for data sent from this
              interface, in bit/s. The traffic will be shaped according
              to this limit.

       options : qos_burst: optional string
              If set, indicates the maximum burst size for data sent
              from this interface, in bits.

       options : qdisc_queue_id: optional string, containing an integer,
       in range 1 to 61,440
              Indicates the queue number on the physical device. This is
              same as the queue_id used in OpenFlow in struct
              ofp_action_enqueue.

     Chassis Redirect Options:

       These options apply to logical ports with type of
       chassisredirect.

       options : distributed-port: optional string
              The name of the distributed port for which this
              chassisredirect port represents a particular instance.

       options : redirect-chassis: optional string
              The chassis that this chassisredirect port is bound to.
              This is taken from options:redirect-chassis in the
              OVN_Northbound database’s Logical_Router_Port table.

     Nested Containers:

       These columns support containers nested within a VM.
       Specifically, they are used when type is empty and logical_port
       identifies the interface of a container spawned inside a VM. They
       are empty for containers or VMs that run directly on a
       hypervisor.

       parent_port: optional string
              This is taken from parent_name in the OVN_Northbound
              database’s Logical_Switch_Port table.

       tag: optional integer, in range 1 to 4,095
              Identifies the VLAN tag in the network traffic associated
              with that container’s network interface.

              This column is used for a different purpose when type is
              localnet (see Localnet Options, above) or l2gateway (see
              L2 Gateway Options, above).

     Naming:

       external_ids : name: optional string
              For a logical switch port, ovn-northd copies this from
              external_ids:neutron:port_name in the Logical_Switch_Port
              table in the OVN_Northbound database, if it is a nonempty
              string.

              For a logical switch port, ovn-northd does not currently
              set this key.

     Common Columns:

       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.

              The ovn-northd program populates this column with all
              entries into the external_ids column of the
              Logical_Switch_Port table of the OVN_Northbound database.

MAC_Binding TABLE         top

       Each row in this table specifies a binding from an IP address to
       an Ethernet address that has been discovered through ARP (for
       IPv4) or neighbor discovery (for IPv6). This table is primarily
       used to discover bindings on physical networks, because IP-to-MAC
       bindings for virtual machines are usually populated statically
       into the Port_Binding table.

       This table expresses a functional relationship:
       MAC_Binding(logical_port, ip) = mac.

       In outline, the lifetime of a logical router’s MAC binding looks
       like this:

              1.  On hypervisor 1, a logical router determines that a
                  packet should be forwarded to IP address A on one of
                  its router ports. It uses its logical flow table to
                  determine that A lacks a static IP-to-MAC binding and
                  the get_arp action to determine that it lacks a
                  dynamic IP-to-MAC binding.

              2.  Using an OVN logical arp action, the logical router
                  generates and sends a broadcast ARP request to the
                  router port. It drops the IP packet.

              3.  The logical switch attached to the router port
                  delivers the ARP request to all of its ports. (It
                  might make sense to deliver it only to ports that have
                  no static IP-to-MAC bindings, but this could also be
                  surprising behavior.)

              4.  A host or VM on hypervisor 2 (which might be the same
                  as hypervisor 1) attached to the logical switch owns
                  the IP address in question. It composes an ARP reply
                  and unicasts it to the logical router port’s Ethernet
                  address.

              5.  The logical switch delivers the ARP reply to the
                  logical router port.

              6.  The logical router flow table executes a put_arp
                  action. To record the IP-to-MAC binding,
                  ovn-controller adds a row to the MAC_Binding table.

              7.  On hypervisor 1, ovn-controller receives the updated
                  MAC_Binding table from the OVN southbound database.
                  The next packet destined to A through the logical
                  router is sent directly to the bound Ethernet address.

   Summary:
       logical_port                  string
       ip                            string
       mac                           string
       datapath                      Datapath_Binding

   Details:
       logical_port: string
              The logical port on which the binding was discovered.

       ip: string
              The bound IP address.

       mac: string
              The Ethernet address to which the IP is bound.

       datapath: Datapath_Binding
              The logical datapath to which the logical port belongs.

DHCP_Options TABLE         top

       Each row in this table stores the DHCP Options supported by
       native OVN DHCP. ovn-northd populates this table with the
       supported DHCP options. ovn-controller looks up this table to get
       the DHCP codes of the DHCP options defined in the "put_dhcp_opts"
       action. Please refer to the RFC 2132
       "https://tools.ietf.org/html/rfc2132" for the possible list of
       DHCP options that can be defined here.

   Summary:
       name                          string
       code                          integer, in range 0 to 254
       type                          string, one of bool, ipv4,
                                     static_routes, str, uint16, uint32,
                                     or uint8

   Details:
       name: string
              Name of the DHCP option.

              Example. name="router"

       code: integer, in range 0 to 254
              DHCP option code for the DHCP option as defined in the RFC
              2132.

              Example. code=3

       type: string, one of bool, ipv4, static_routes, str, uint16,
       uint32, or uint8
              Data type of the DHCP option code.

              value: bool
                     This indicates that the value of the DHCP option is
                     a bool.

                     Example. "name=ip_forward_enable", "code=19",
                     "type=bool".

                     put_dhcp_opts(..., ip_forward_enable = 1,...)

              value: uint8
                     This indicates that the value of the DHCP option is
                     an unsigned int8 (8 bits)

                     Example. "name=default_ttl", "code=23",
                     "type=uint8".

                     put_dhcp_opts(..., default_ttl = 50,...)

              value: uint16
                     This indicates that the value of the DHCP option is
                     an unsigned int16 (16 bits).

                     Example. "name=mtu", "code=26", "type=uint16".

                     put_dhcp_opts(..., mtu = 1450,...)

              value: uint32
                     This indicates that the value of the DHCP option is
                     an unsigned int32 (32 bits).

                     Example. "name=lease_time", "code=51",
                     "type=uint32".

                     put_dhcp_opts(..., lease_time = 86400,...)

              value: ipv4
                     This indicates that the value of the DHCP option is
                     an IPv4 address or addresses.

                     Example. "name=router", "code=3", "type=ipv4".

                     put_dhcp_opts(..., router = 10.0.0.1,...)

                     Example. "name=dns_server", "code=6", "type=ipv4".

                     put_dhcp_opts(..., dns_server = {8.8.8.8
                     7.7.7.7},...)

              value: static_routes
                     This indicates that the value of the DHCP option
                     contains a pair of IPv4 route and next hop
                     addresses.

                     Example. "name=classless_static_route", "code=121",
                     "type=static_routes".

                     put_dhcp_opts(..., classless_static_route =
                     {30.0.0.0/24,10.0.0.4,0.0.0.0/0,10.0.0.1}...)

              value: str
                     This indicates that the value of the DHCP option is
                     a string.

                     Example. "name=host_name", "code=12", "type=str".

DHCPv6_Options TABLE         top

       Each row in this table stores the DHCPv6 Options supported by
       native OVN DHCPv6. ovn-northd populates this table with the
       supported DHCPv6 options. ovn-controller looks up this table to
       get the DHCPv6 codes of the DHCPv6 options defined in the
       put_dhcpv6_opts action. Please refer to RFC 3315 and RFC 3646 for
       the list of DHCPv6 options that can be defined here.

   Summary:
       name                          string
       code                          integer, in range 0 to 254
       type                          string, one of ipv6, mac, or str

   Details:
       name: string
              Name of the DHCPv6 option.

              Example. name="ia_addr"

       code: integer, in range 0 to 254
              DHCPv6 option code for the DHCPv6 option as defined in the
              appropriate RFC.

              Example. code=3

       type: string, one of ipv6, mac, or str
              Data type of the DHCPv6 option code.

              value: ipv6
                     This indicates that the value of the DHCPv6 option
                     is an IPv6 address(es).

                     Example. "name=ia_addr", "code=5", "type=ipv6".

                     put_dhcpv6_opts(..., ia_addr = ae70::4,...)

              value: str
                     This indicates that the value of the DHCPv6 option
                     is a string.

                     Example. "name=domain_search", "code=24",
                     "type=str".

                     put_dhcpv6_opts(..., domain_search =
                     ovn.domain,...)

              value: mac
                     This indicates that the value of the DHCPv6 option
                     is a MAC address.

                     Example. "name=server_id", "code=2", "type=mac".

                     put_dhcpv6_opts(..., server_id =
                     01:02:03:04L05:06,...)

Connection TABLE         top

       Configuration for a database connection to an Open vSwitch
       database (OVSDB) client.

       This table primarily configures the Open vSwitch database server
       (ovsdb-server).

       The Open vSwitch database server can initiate and maintain active
       connections to remote clients. It can also listen for database
       connections.

   Summary:
       Core Features:
         target                      string (must be unique within
                                     table)
         read_only                   boolean
         role                        string
       Client Failure Detection and Handling:
         max_backoff                 optional integer, at least 1,000
         inactivity_probe            optional integer
       Status:
         is_connected                boolean
         status : last_error         optional string
         status : state              optional string, one of ACTIVE,
                                     BACKOFF, CONNECTING, IDLE, or VOID
         status : sec_since_connect  optional string, containing an
                                     integer, at least 0
         status : sec_since_disconnect
                                     optional string, containing an
                                     integer, at least 0
         status : locks_held         optional string
         status : locks_waiting      optional string
         status : locks_lost         optional string
         status : n_connections      optional string, containing an
                                     integer, at least 2
         status : bound_port         optional string, containing an
                                     integer
       Common Columns:
         external_ids                map of string-string pairs
         other_config                map of string-string pairs

   Details:
     Core Features:

       target: string (must be unique within table)
              Connection methods for clients.

              The following connection methods are currently supported:

              ssl:host[:port]
                     The specified SSL port on the given host, which can
                     either be a DNS name (if built with unbound
                     library) or an IP address. A valid SSL
                     configuration must be provided when this form is
                     used, this configuration can be specified via
                     command-line options or the SSL table.

                     If port is not specified, it defaults to 6640.

                     SSL support is an optional feature that is not
                     always built as part of Open vSwitch.

              tcp:host[:port]
                     The specified TCP port on the given host, which can
                     either be a DNS name (if built with unbound
                     library) or an IP address (IPv4 or IPv6). If host
                     is an IPv6 address, wrap it in square brackets,
                     e.g. tcp:[::1]:6640.

                     If port is not specified, it defaults to 6640.

              pssl:[port][:host]
                     Listens for SSL connections on the specified TCP
                     port. Specify 0 for port to have the kernel
                     automatically choose an available port. If host,
                     which can either be a DNS name (if built with
                     unbound library) or an IP address, is specified,
                     then connections are restricted to the resolved or
                     specified local IP address (either IPv4 or IPv6
                     address). If host is an IPv6 address, wrap in
                     square brackets, e.g. pssl:6640:[::1]. If host is
                     not specified then it listens only on IPv4 (but not
                     IPv6) addresses. A valid SSL configuration must be
                     provided when this form is used, this can be
                     specified either via command-line options or the
                     SSL table.

                     If port is not specified, it defaults to 6640.

                     SSL support is an optional feature that is not
                     always built as part of Open vSwitch.

              ptcp:[port][:host]
                     Listens for connections on the specified TCP port.
                     Specify 0 for port to have the kernel automatically
                     choose an available port. If host, which can either
                     be a DNS name (if built with unbound library) or an
                     IP address, is specified, then connections are
                     restricted to the resolved or specified local IP
                     address (either IPv4 or IPv6 address). If host is
                     an IPv6 address, wrap it in square brackets, e.g.
                     ptcp:6640:[::1]. If host is not specified then it
                     listens only on IPv4 addresses.

                     If port is not specified, it defaults to 6640.

              When multiple clients are configured, the target values
              must be unique. Duplicate target values yield unspecified
              results.

       read_only: boolean
              true to restrict these connections to read-only
              transactions, false to allow them to modify the database.

       role: string
              String containing role name for this connection entry.

     Client Failure Detection and Handling:

       max_backoff: optional integer, at least 1,000
              Maximum number of milliseconds to wait between connection
              attempts. Default is implementation-specific.

       inactivity_probe: optional integer
              Maximum number of milliseconds of idle time on connection
              to the client before sending an inactivity probe message.
              If Open vSwitch does not communicate with the client for
              the specified number of seconds, it will send a probe. If
              a response is not received for the same additional amount
              of time, Open vSwitch assumes the connection has been
              broken and attempts to reconnect. Default is
              implementation-specific. A value of 0 disables inactivity
              probes.

     Status:

       Key-value pair of is_connected is always updated. Other key-value
       pairs in the status columns may be updated depends on the target
       type.

       When target specifies a connection method that listens for
       inbound connections (e.g. ptcp: or punix:), both n_connections
       and is_connected may also be updated while the remaining key-
       value pairs are omitted.

       On the other hand, when target specifies an outbound connection,
       all key-value pairs may be updated, except the above-mentioned
       two key-value pairs associated with inbound connection targets.
       They are omitted.

       is_connected: boolean
              true if currently connected to this client, false
              otherwise.

       status : last_error: optional string
              A human-readable description of the last error on the
              connection to the manager; i.e. strerror(errno). This key
              will exist only if an error has occurred.

       status : state: optional string, one of ACTIVE, BACKOFF,
       CONNECTING, IDLE, or VOID
              The state of the connection to the manager:

              VOID   Connection is disabled.

              BACKOFF
                     Attempting to reconnect at an increasing period.

              CONNECTING
                     Attempting to connect.

              ACTIVE Connected, remote host responsive.

              IDLE   Connection is idle. Waiting for response to keep-
                     alive.

              These values may change in the future. They are provided
              only for human consumption.

       status : sec_since_connect: optional string, containing an
       integer, at least 0
              The amount of time since this client last successfully
              connected to the database (in seconds). Value is empty if
              client has never successfully been connected.

       status : sec_since_disconnect: optional string, containing an
       integer, at least 0
              The amount of time since this client last disconnected
              from the database (in seconds). Value is empty if client
              has never disconnected.

       status : locks_held: optional string
              Space-separated list of the names of OVSDB locks that the
              connection holds. Omitted if the connection does not hold
              any locks.

       status : locks_waiting: optional string
              Space-separated list of the names of OVSDB locks that the
              connection is currently waiting to acquire. Omitted if the
              connection is not waiting for any locks.

       status : locks_lost: optional string
              Space-separated list of the names of OVSDB locks that the
              connection has had stolen by another OVSDB client. Omitted
              if no locks have been stolen from this connection.

       status : n_connections: optional string, containing an integer,
       at least 2
              When target specifies a connection method that listens for
              inbound connections (e.g. ptcp: or pssl:) and more than
              one connection is actually active, the value is the number
              of active connections. Otherwise, this key-value pair is
              omitted.

       status : bound_port: optional string, containing an integer
              When target is ptcp: or pssl:, this is the TCP port on
              which the OVSDB server is listening. (This is particularly
              useful when target specifies a port of 0, allowing the
              kernel to choose any available port.)

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

       other_config: map of string-string pairs

SSL TABLE         top

       SSL configuration for ovn-sb database access.

   Summary:
       private_key                   string
       certificate                   string
       ca_cert                       string
       bootstrap_ca_cert             boolean
       ssl_protocols                 string
       ssl_ciphers                   string
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       private_key: string
              Name of a PEM file containing the private key used as the
              switch’s identity for SSL connections to the controller.

       certificate: string
              Name of a PEM file containing a certificate, signed by the
              certificate authority (CA) used by the controller and
              manager, that certifies the switch’s private key,
              identifying a trustworthy switch.

       ca_cert: string
              Name of a PEM file containing the CA certificate used to
              verify that the switch is connected to a trustworthy
              controller.

       bootstrap_ca_cert: boolean
              If set to true, then Open vSwitch will attempt to obtain
              the CA certificate from the controller on its first SSL
              connection and save it to the named PEM file. If it is
              successful, it will immediately drop the connection and
              reconnect, and from then on all SSL connections must be
              authenticated by a certificate signed by the CA
              certificate thus obtained. This option exposes the SSL
              connection to a man-in-the-middle attack obtaining the
              initial CA certificate. It may still be useful for
              bootstrapping.

       ssl_protocols: string
              List of SSL protocols to be enabled for SSL connections.
              The default when this option is omitted is
              TLSv1,TLSv1.1,TLSv1.2.

       ssl_ciphers: string
              List of ciphers (in OpenSSL cipher string format) to be
              supported for SSL connections. The default when this
              option is omitted is HIGH:!aNULL:!MD5.

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

DNS TABLE         top

       Each row in this table stores the DNS records. The OVN action
       dns_lookup uses this table for DNS resolution.

   Summary:
       records                       map of string-string pairs
       datapaths                     set of 1 or more Datapath_Bindings
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       records: map of string-string pairs
              Key-value pair of DNS records with DNS query name as the
              key and a string of IP address(es) separated by comma or
              space as the value.

              Example:  "vm1.ovn.org" = "10.0.0.4 aef0::4"

       datapaths: set of 1 or more Datapath_Bindings
              The DNS records defined in the column records will be
              applied only to the DNS queries originating from the
              datapaths defined in this column.

     Common Columns:

       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.

RBAC_Role TABLE         top

       Role table for role-based access controls.

   Summary:
       name                          string
       permissions                   map of string-weak reference to
                                     RBAC_Permission pairs

   Details:
       name: string
              The role name, corresponding to the role column in the
              Connection table.

       permissions: map of string-weak reference to RBAC_Permission
       pairs
              A mapping of table names to rows in the RBAC_Permission
              table.

RBAC_Permission TABLE         top

       Permissions table for role-based access controls.

   Summary:
       table                         string
       authorization                 set of strings
       insert_delete                 boolean
       update                        set of strings

   Details:
       table: string
              Name of table to which this row applies.

       authorization: set of strings
              Set of strings identifying columns and column:key pairs to
              be compared with client ID. At least one match is required
              in order to be authorized. A zero-length string is treated
              as a special value indicating all clients should be
              considered authorized.

       insert_delete: boolean
              When "true", row insertions and authorized row deletions
              are permitted.

       update: set of strings
              Set of strings identifying columns and column:key pairs
              that authorized clients are allowed to modify.

Gateway_Chassis TABLE         top

       Association of Port_Binding rows of type chassisredirect to a
       Chassis. The traffic going out through a specific chassisredirect
       port will be redirected to a chassis, or a set of them in high
       availability configurations.

   Summary:
       name                          string (must be unique within
                                     table)
       chassis                       optional weak reference to Chassis
       priority                      integer, in range 0 to 32,767
       options                       map of string-string pairs
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       name: string (must be unique within table)
              Name of the Gateway_Chassis.

              A suggested, but not required naming convention is
              ${port_name}_${chassis_name}.

       chassis: optional weak reference to Chassis
              The Chassis to which we send the traffic.

       priority: integer, in range 0 to 32,767
              This is the priority the specific Chassis among all
              Gateway_Chassis belonging to the same Port_Binding.

       options: map of string-string pairs
              Reserved for future use.

     Common Columns:

       The overall purpose of these columns is described under Common
       Columns at the beginning of this document.

       external_ids: map of string-string pairs

HA_Chassis TABLE         top

   Summary:
       chassis                       optional weak reference to Chassis
       priority                      integer, in range 0 to 32,767
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       chassis: optional weak reference to Chassis
              The Chassis which provides the HA functionality.

       priority: integer, in range 0 to 32,767
              Priority of the HA chassis. Chassis with highest priority
              will be the master in the HA chassis group.

     Common Columns:

       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.

HA_Chassis_Group TABLE         top

       Table representing a group of chassis which can provide High
       availability services. Each chassis in the group is represented
       by the table HA_Chassis. The HA chassis with highest priority
       will be the master of this group. If the master chassis failover
       is detected, the HA chassis with the next higher priority takes
       over the responsibility of providing the HA. If ha_chassis_group
       column of the table Port_Binding references this table, then this
       HA chassis group provides the gateway functionality and redirects
       the gateway traffic to the master of this group.

   Summary:
       name                          string (must be unique within
                                     table)
       ha_chassis                    set of HA_Chassiss
       ref_chassis                   set of weak reference to Chassiss
       Common Columns:
         external_ids                map of string-string pairs

   Details:
       name: string (must be unique within table)
              Name of the HA_Chassis_Group. Name should be unique.

       ha_chassis: set of HA_Chassiss
              A list of HA_Chassis which belongs to this group.

       ref_chassis: set of weak reference to Chassiss
              A list of chassis which references this HA chassis group.

     Common Columns:

       external_ids: map of string-string pairs
              See External IDs at the beginning of this document.

Controller_Event TABLE         top

       Database table used by ovn-controller to report CMS related
       events. Please note there is no guarantee a given event is
       written exactly once in the db. It is CMS responsibility to
       squash duplicated lines or to filter out duplicated events

   Summary:
       event_type                    string, must be empty_lb_backends
       event_info                    map of string-string pairs
       chassis                       optional weak reference to Chassis
       seq_num                       integer

   Details:
       event_type: string, must be empty_lb_backends
              Event type occurred

       event_info: map of string-string pairs
              Key-value pairs used to specify event info to the CMS.
              Possible values are:

              •      vip: VIP reported for the empty_lb_backends event

              •      protocol: Transport protocol reported for the
                     empty_lb_backends event

              •      load_balancer: UUID of the load balancer reported
                     for the empty_lb_backends event

       chassis: optional weak reference to Chassis
              This column is a Chassis record to identify the chassis
              that has managed a given event.

       seq_num: integer
              Event sequence number. Global counter for controller
              generated events. It can be used by the CMS to detect
              possible duplication of the same event.

IP_Multicast TABLE         top

       IP Multicast configuration options. For now only applicable to
       IGMP.

   Summary:
       datapath                      weak reference to Datapath_Binding
                                     (must be unique within table)
       enabled                       optional boolean
       querier                       optional boolean
       table_size                    optional integer
       idle_timeout                  optional integer
       query_interval                optional integer
       seq_no                        integer
       Querier configuration options:
         eth_src                     string
         ip4_src                     string
         query_max_resp              optional integer

   Details:
       datapath: weak reference to Datapath_Binding (must be unique
       within table)
              Datapath_Binding entry for which these configuration
              options are defined.

       enabled: optional boolean
              Enables/disables multicast snooping. Default: disabled.

       querier: optional boolean
              Enables/disables multicast querying. If enabled then
              multicast querying is enabled by default.

       table_size: optional integer
              Limits the number of multicast groups that can be learned.
              Default: 2048 groups per datapath.

       idle_timeout: optional integer
              Configures the idle timeout (in seconds) for IP multicast
              groups if multicast snooping is enabled. Default: 300
              seconds.

       query_interval: optional integer
              Configures the interval (in seconds) for sending multicast
              queries if snooping and querier are enabled. Default:
              idle_timeout/2 seconds.

       seq_no: integer
              ovn-controller reads this value and flushes all learned
              multicast groups when it detects that seq_no was changed.

     Querier configuration options:

       The ovn-controller process that runs on OVN hypervisor nodes uses
       the following columns to determine field values in IGMP queries
       that it originates:

       eth_src: string
              Source Ethernet address.

       ip4_src: string
              Source IPv4 address.

       query_max_resp: optional integer
              Value (in seconds) to be used as "max-response" field in
              multicast queries. Default: 1 second.

IGMP_Group TABLE         top

       Contains learned IGMP groups indexed by address/datapath/chassis.

   Summary:
       address                       string
       datapath                      optional weak reference to
                                     Datapath_Binding
       chassis                       optional weak reference to Chassis
       ports                         set of weak reference to
                                     Port_Bindings

   Details:
       address: string
              Destination IPv4 address for the IGMP group.

       datapath: optional weak reference to Datapath_Binding
              Datapath to which this IGMP group belongs.

       chassis: optional weak reference to Chassis
              Chassis to which this IGMP group belongs.

       ports: set of weak reference to Port_Bindings
              The destination port bindings for this IGMP group.

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 bugs@openvswitch.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://github.com/openvswitch/ovs.git⟩ on 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-20.)  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
       man-pages@man7.org

Open vSwitch 2.12.90         DB Schema 2.4.0                   ovn-sb(5)

Pages that refer to this page: ovs-sim(1)ovn-architecture(7)ovn-controller(8)ovn-controller-vtep(8)ovn-northd(8)ovn-sbctl(8)ovn-trace(8)