ovn-sb(5)

NAME
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 three classes of data with different properties, as described in the sections below.

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

The Chassis table comprises the PN tables.

LN 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).

LN 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. Past experience shows that in the presence of large logical networks, even finer-grained partitioning of data, e.g. designing logical flows so that only the chassis hosting a logical port needs related flows, pays off scale-wise. (This is not necessary initially but it is worth bearing in mind in the design.)

The LN is a slave of the cloud management system running northbound of OVN. That CMS determines the entire OVN logical configuration and therefore the LN’s content 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.

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

Logical_Flow and Multicast_Group contain LN data.

Bindings data 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.

Bindings 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.

  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

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
Chassis
    Physical Network Hypervisor and Gateway Information
Encap
    Encapsulation Types
Logical_Flow
    Logical Network Flows
Multicast_Group
    Logical Port Multicast Groups
Datapath_Binding
    Physical-Logical Datapath Bindings
Port_Binding
    Physical-Logical Port Bindings

Chassis TABLE
Each row in this table represents a hypervisor or gateway (a chassis) in the physical network (PN). 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)
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)
    A chassis name, taken from external_ids:system-id in the Open_vSwitch database’s Open_vSwitch table. OVN does not prescribe a particular format for chassis names. 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. 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
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 stt, geneve, or vxlan
options
    map of string-string pairs
ip
    string

  Details:

type: string, one of stt, geneve, 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, e.g. IPsec parameters when IPsec support is introduced. No options are currently defined.

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

Logical_Flow TABLE
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. 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 ... reg4 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 is responsible for populating the Logical_Flow table, so the stages are an implementation detail and subject to change. This section describes the current logical flow table.

The ingress pipeline consists of the following stages:

    •   Port Security (Table 0): Validates the source address, drops packets with a VLAN tag, and, if configured, verifies that the logical port is allowed to send with the source address.

    •   L2 Destination Lookup (Table 1): Forwards known unicast addresses to the appropriate logical port. Unicast packets to unknown hosts are forwarded to logical ports configured with the special unknown mac address. Broadcast, and multicast are flooded to all ports in the logical switch.

The egress pipeline consists of the following stages:

    •   ACL (Table 0): Applies any specified access control lists.

    •   Port Security (Table 1): If configured, verifies that the logical port is allowed to receive packets with the destination address.

  Summary:
logical_datapath
    Datapath_Binding
pipeline
    string, either ingress or egress
table_id
    integer, in range 0 to 15
priority
    integer, in range 0 to 65,535
match
    string
actions
    string
external_ids : stage-name
    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 ingress or egress
    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 15
    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.

    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 nominal 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 && ...’’.

    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.

    •   reg0...reg4

    •   inport outport

    •   eth.src eth.dst eth.type

    •   vlan.tci vlan.vid vlan.pcp vlan.present

    •   ip.proto ip.dscp ip.ecn ip.ttl ip.frag

    •   ip4.src ip4.dst

    •   ip6.src ip6.dst ip6.label

    •   arp.op arp.spa arp.tpa arp.sha arp.tha

    •   tcp.src tcp.dst tcp.flags

    •   udp.src udp.dst

    •   sctp.src sctp.dst

    •   icmp4.type icmp4.code

    •   icmp6.type icmp6.code

    •   nd.target nd.sll nd.tll

    •   ct_state, which has the following Boolean subfields:

        •   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

        ct_state and its subfields are initialized by the ct_next action, described below.

    The following predicates are supported:

    •   eth.bcast expands to eth.dst == ff:ff:ff:ff:ff:ff

    •   eth.mcast expands to eth.dst[40]

    •   vlan.present expands to vlan.tci[12]

    •   ip4 expands to eth.type == 0x800

    •   ip4.mcast expands to ip4.dst[28..31] == 0xe

    •   ip6 expands to eth.type == 0x86dd

    •   ip expands to ip4 || ip6

    •   icmp4 expands to ip4 && ip.proto == 1

    •   icmp6 expands to ip6 && ip.proto == 58

    •   icmp expands to icmp4 || icmp6

    •   ip.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_frag

    •   arp expands to eth.type == 0x806

    •   nd expands to icmp6.type == {135, 136} && icmp6.code == 0

    •   tcp expands to ip.proto == 6

    •   udp expands to ip.proto == 17

    •   sctp 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.)

        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 inport = ""; to set the logical input port to an empty string (which should not be used as the name of any logical port).

    next;
    next(table);
        Executes another logical datapath table as a subroutine. By default, the table after the current one is executed. Specify table to jump to a specific table in the same pipeline.

    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.

    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, so overlapping addresses may be used. To allow traffic related to the matched flow, execute ct_commit.

        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;
        Commit the flow to the connection tracking entry associated with it by a previous call to ct_next.

    The following actions will likely be useful later, but they have not been thought out carefully.

    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 = 0x0806

        •   arp.op = 1 (ARP request)

        •   arp.sha copied from eth.src

        •   arp.spa copied from ip4.src

        •   arp.tha = 00:00:00:00:00:00

        •   arp.tpa copied from ip4.dst

        Prerequisite: ip4

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

        The ICMPv4 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. Ethernet and IPv4 fields not listed here are not changed:

        •   ip.proto = 1 (ICMPv4)

        •   ip.frag = 0 (not a fragment)

        •   icmp4.type = 3 (destination unreachable)

        •   icmp4.code = 1 (host unreachable)

        Details TBD.

        Prerequisite: ip4

    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.

        Details TBD.

        Prerequisite: tcp

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

Datapath_Binding TABLE
Each row in this table identifies physical bindings of a logical datapath. A logical datapath 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.

  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
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. 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. 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
Most rows in this table identify the physical location of a logical port. (The exceptions are logical patch ports, which do not have any physical location.)

For every Logical_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.md.

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)
    chassis
        optional weak reference to Chassis
    tunnel_key
        integer, in range 1 to 32,767
    mac
        set of strings
    type
        string
Patch Options:
    options : peer
        optional string
Localnet Options:
    options : network_name
        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
Nested Containers:
    parent_port
        optional string
    tag
        optional integer, in range 1 to 4,095

  Details:

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_Port table. OVN does not prescribe a particular format for the logical port ID.

chassis: optional weak reference to Chassis
    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/ovn-controller-vtep.

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.

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

    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.
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. 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:

    $ 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. 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. 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_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).