path: root/ovn/ovn-nb.xml

<?xml version="1.0" encoding="utf-8"?>
<database name="ovn-nb" title="OVN Northbound Database">
  <p>
    This database is the interface between OVN and the cloud management system
    (CMS), such as OpenStack, running above it.  The CMS produces almost all of
    the contents of the database.  The <code>ovn-northd</code> program
    monitors the database contents, transforms it, and stores it into the <ref
    db="OVN_Southbound"/> database.
  </p>

  <p>
    We generally speak of ``the'' CMS, but one can imagine scenarios in
    which multiple CMSes manage different parts of an OVN deployment.
  </p>

  <h2>External IDs</h2>

  <p>
    Each of the tables in this database contains a special column, named
    <code>external_ids</code>.  This column has the same form and purpose each
    place it appears.
  </p>

  <dl>
    <dt><code>external_ids</code>: map of string-string pairs</dt>
    <dd>
      Key-value pairs for use by the CMS.  The CMS might use certain pairs, for
      example, to identify entities in its own configuration that correspond to
      those in this database.
    </dd>
  </dl>

  <table name="Logical_Switch" title="L2 logical switch">
    <p>
      Each row represents one L2 logical switch.  A given switch's ports are
      the <ref table="Logical_Port"/> rows whose <ref table="Logical_Port"
      column="lswitch"/> column points to its row.
    </p>

    <column name="name">
      <p>
        A name for the logical switch.  This name has no special meaning or purpose
        other than to provide convenience for human interaction with the ovn-nb
        database.  There is no requirement for the name to be unique.  The
        logical switch's UUID should be used as the unique identifier.
      </p>
    </column>

    <column name="router_port">
      <p>
        The router port to which this logical switch is connected, or empty if
        this logical switch is not connected to any router.  A switch may be
        connected to at most one logical router, but this is not a significant
        restriction because logical routers may be connected into arbitrary
        topologies.
      </p>
    </column>

    <group title="Common Columns">
      <column name="external_ids">
        See <em>External IDs</em> at the beginning of this document.
      </column>
    </group>
  </table>

  <table name="Logical_Port" title="L2 logical switch port">
    <p>
      A port within an L2 logical switch.
    </p>

    <column name="lswitch">
      The logical switch to which the logical port is connected.
    </column>

    <column name="name">
      <p>
      The logical port name.
      </p>

      <p>
      For entities (VMs or containers) that are spawned in the hypervisor,
      the name used here must match those used in the <ref key="iface-id"
      table="Interface" column="external_ids" db="Open_vSwitch"/> in the
      <ref db="Open_vSwitch"/> database's <ref table="Interface"
      db="Open_vSwitch"/> table, because hypervisors use <ref key="iface-id"
      table="Interface" column="external_ids" db="Open_vSwitch"/> as a lookup
      key to identify the network interface of that entity.
      </p>

      <p>
      For containers that are spawned inside a VM, the name can be
      any unique identifier.  In such a case, <ref column="parent_name"/>
      must be populated.
      </p>
    </column>

    <column name="parent_name">
      When <ref column="name"/> identifies the interface of a container
      spawned inside a tenant VM, this column represents the VM interface
      through which the container interface sends its network traffic.
      The name used here must match those used in the <ref key="iface-id"
      table="Interface" column="external_ids" db="Open_vSwitch"/> in the
      <ref db="Open_vSwitch"/> table, because hypervisors in this case use
      <ref key="iface-id" table="Interface" column="external_ids"
      db="Open_vSwitch"/> as a lookup key to identify the network interface
      of the tenant VM.
    </column>

    <column name="tag">
      When <ref column="name"/> identifies the interface of a container
      spawned inside a tenant VM, this column identifies the VLAN tag in
      the network traffic associated with that container's network interface.
      When there are multiple container interfaces inside a VM, all of
      them send their network traffic through a single VM network interface and
      this value helps OVN identify the correct container interface.
    </column>

    <column name="up">
      This column is populated by <code>ovn-northd</code>, rather than by
      the CMS plugin as is most of this database.  When a logical port is bound
      to a physical location in the OVN Southbound database <ref
      db="OVN_Southbound" table="Bindings"/> table, <code>ovn-northd</code>
      sets this column to <code>true</code>; otherwise, or if the port
      becomes unbound later, it sets it to <code>false</code>.  This
      allows the CMS to wait for a VM's (or container's) networking to
      become active before it allows the VM (or container) to start.
    </column>

    <column name="macs">
      The logical port's own Ethernet address or addresses, each in the form
      <var>xx</var>:<var>xx</var>:<var>xx</var>:<var>xx</var>:<var>xx</var>:<var>xx</var>.
      Like a physical Ethernet NIC, a logical port ordinarily has a single
      fixed Ethernet address.  The string <code>unknown</code> is also allowed
      to indicate that the logical port has an unknown set of (additional)
      source addresses.
    </column>

    <column name="port_security">
      <p>
        A set of L2 (Ethernet) or L3 (IPv4 or IPv6) addresses or L2+L3 pairs
        from which the logical port is allowed to send packets and to which it
        is allowed to receive packets.  If this column is empty, all addresses
        are permitted.
      </p>

      <p>
        Exact syntax is TBD.  One could simply use comma- or
        space-separated L2 and L3 addresses in each set member, or
        replace this by a subset of the general-purpose expression
        language used for the <ref column="match" table="Pipeline"
        db="OVN_Southbound"/> column in the OVN Southbound database's
        <ref table="Pipeline" db="OVN_Southbound"/> table.
      </p>
    </column>

    <group title="Common Columns">
      <column name="external_ids">
        See <em>External IDs</em> at the beginning of this document.
      </column>
    </group>
  </table>

  <table name="ACL" title="Access Control List (ACL) rule">
    <p>
      Each row in this table represents one ACL rule for the logical switch in
      its <ref column="lswitch"/> column.  The <ref column="action"/> column for
      the highest-<ref column="priority"/> matching row in this table
      determines a packet's treatment.  If no row matches, packets are allowed
      by default.  (Default-deny treatment is possible: add a rule with <ref
      column="priority"/> 0, <code>true</code> as <ref column="match"/>, and
      <code>deny</code> as <ref column="action"/>.)
    </p>

    <column name="lswitch">
      The switch to which the ACL rule applies.  The expression in the
      <ref column="match"/> column may match against logical ports
      within this switch.
    </column>

    <column name="priority">
      The ACL rule's priority.  Rules with numerically higher priority take
      precedence over those with lower.  If two ACL rules with the same
      priority both match, then the one actually applied to a packet is
      undefined.
    </column>

    <column name="match">
      The packets that the ACL should match, in the same expression
      language used for the <ref column="match" table="Pipeline"
      db="OVN_Southbound"/> column in the OVN Southbound database's <ref
      table="Pipeline" db="OVN_Southbound"/> table.  Match
      <code>inport</code> and <code>outport</code> against names of
      logical ports within <ref column="lswitch"/> to implement ingress
      and egress ACLs, respectively.  In logical switches connected to
      logical routers, the special port name <code>ROUTER</code> refers
      to the logical router port.
    </column>

    <column name="action">
      <p>The action to take when the ACL rule matches:</p>
      
      <ul>
	<li>
	  <code>allow</code>: Forward the packet.
	</li>

	<li>
	  <code>allow-related</code>: Forward the packet and related traffic
	  (e.g. inbound replies to an outbound connection).
	</li>

	<li>
	  <code>drop</code>: Silently drop the packet.
	</li>

	<li>
	  <code>reject</code>: Drop the packet, replying with a RST for TCP or
	  ICMP unreachable message for other IP-based protocols.
	</li>
      </ul>
    </column>

    <column name="log">
      If set to <code>true</code>, packets that match the ACL will trigger a
      log message on the transport node or nodes that perform ACL processing.
      Logging may be combined with any <ref column="action"/>.
    </column>

    <group title="Common Columns">
      <column name="external_ids">
        See <em>External IDs</em> at the beginning of this document.
      </column>
    </group>
  </table>

  <table name="Logical_Router" title="L3 logical router">
    <p>
      Each row represents one L3 logical router.  A given router's ports are
      the <ref table="Logical_Router_Port"/> rows whose <ref
      table="Logical_Router_Port" column="router"/> column points to its row.
    </p>

    <column name="ip">
      The logical router's own IP address.  The logical router uses this
      address for ICMP replies (e.g. network unreachable messages) and other
      traffic that it originates and responds to traffic destined to this
      address (e.g. ICMP echo requests).
    </column>

    <column name="default_gw">
      IP address to use as default gateway, if any.
    </column>

    <group title="Common Columns">
      <column name="external_ids">
        See <em>External IDs</em> at the beginning of this document.
      </column>
    </group>
  </table>

  <table name="Logical_Router_Port" title="L3 logical router port">
    <p>
      A port within an L3 logical router.
    </p>

    <p>
      A router port is always attached to a switch port.  The connection can be
      identified by following the <ref column="router_port"
      table="Logical_Port"/> column from an appropriate <ref
      table="Logical_Port"/> row.
    </p>

    <column name="router">
      The router to which the port belongs.
    </column>

    <column name="network">
      The IP network and netmask of the network on the router port.  Used for
      routing.
    </column>

    <column name="mac">
      The Ethernet address that belongs to this router port.
    </column>

    <group title="Common Columns">
      <column name="external_ids">
        See <em>External IDs</em> at the beginning of this document.
      </column>
    </group>
  </table>
</database>