1 <?xml version="1.0" encoding="utf-8"?>
2 <manpage program="ovn-northd" section="8" title="ovn-northd">
4 <p>ovn-northd -- Open Virtual Network central control daemon</p>
7 <p><code>ovn-northd</code> [<var>options</var>]</p>
11 <code>ovn-northd</code> is a centralized daemon responsible for
12 translating the high-level OVN configuration into logical
13 configuration consumable by daemons such as
14 <code>ovn-controller</code>. It translates the logical network
15 configuration in terms of conventional network concepts, taken
16 from the OVN Northbound Database (see <code>ovn-nb</code>(5)),
17 into logical datapath flows in the OVN Southbound Database (see
18 <code>ovn-sb</code>(5)) below it.
21 <h1>Configuration</h1>
23 <code>ovn-northd</code> requires a connection to the Northbound
24 and Southbound databases. The defaults are <code>ovnnb_db.sock</code>
25 and <code>ovnsb_db.sock</code> respectively
26 in the local Open vSwitch's "run" directory. This may be
27 overridden with the following commands:
32 <code>--ovnnb-db=<var>database</var></code>
35 The database containing the OVN Northbound Database.
40 <code>--ovnsb-db=<var>database</var></code>
43 The database containing the OVN Southbound Database.
48 The <var>database</var> argument must take one of the following forms:
53 <code>ssl:<var>ip</var>:<var>port</var></code>
56 The specified SSL <var>port</var> on the host at the given
57 <var>ip</var>, which must be expressed as an IP address (not a DNS
58 name) in IPv4 or IPv6 address format. If <var>ip</var> is an IPv6
59 address, then wrap <var>ip</var> with square brackets, e.g.:
60 <code>ssl:[::1]:6640</code>. The <code>--private-key</code>,
61 <code>--certificate</code>, and <code>--ca-cert</code> options are
62 mandatory when this form is used.
67 <code>tcp:<var>ip</var>:<var>port</var></code>
70 Connect to the given TCP <var>port</var> on <var>ip</var>, where
71 <var>ip</var> can be IPv4 or IPv6 address. If <var>ip</var> is an
72 IPv6 address, then wrap <var>ip</var> with square brackets, e.g.:
73 <code>tcp:[::1]:6640</code>.
78 <code>unix:<var>file</var></code>
81 On POSIX, connect to the Unix domain server socket named
85 On Windows, connect to a localhost TCP port whose value is written
91 <h1>Runtime Management Commands</h1>
93 <code>ovs-appctl</code> can send commands to a running
94 <code>ovn-northd</code> process. The currently supported commands
97 <dt><code>exit</code></dt>
99 Causes <code>ovn-northd</code> to gracefully terminate.
104 <h1>Logical Flow Table Structure</h1>
107 One of the main purposes of <code>ovn-northd</code> is to populate the
108 <code>Logical_Flow</code> table in the <code>OVN_Southbound</code>
109 database. This section describes how <code>ovn-northd</code> does this
110 for switch and router logical datapaths.
113 <h2>Logical Switch Datapaths</h2>
115 <h3>Ingress Table 0: Admission Control and Ingress Port Security - L2</h3>
118 Ingress table 0 contains these logical flows:
123 Priority 100 flows to drop packets with VLAN tags or multicast Ethernet
128 Priority 50 flows that implement ingress port security for each enabled
129 logical port. For logical ports on which port security is enabled,
130 these match the <code>inport</code> and the valid <code>eth.src</code>
131 address(es) and advance only those packets to the next flow table. For
132 logical ports on which port security is not enabled, these advance all
133 packets that match the <code>inport</code>.
138 There are no flows for disabled logical ports because the default-drop
139 behavior of logical flow tables causes packets that ingress from them to
143 <h3>Ingress Table 1: Ingress Port Security - IP</h3>
146 Ingress table 1 contains these logical flows:
152 For each element in the port security set having one or more IPv4 or
153 IPv6 addresses (or both),
158 Priority 90 flow to allow IPv4 traffic if it has IPv4 addresses
159 which match the <code>inport</code>, valid <code>eth.src</code>
160 and valid <code>ip4.src</code> address(es).
164 Priority 90 flow to allow IPv4 DHCP discovery traffic if it has a
165 valid <code>eth.src</code>. This is necessary since DHCP discovery
166 messages are sent from the unspecified IPv4 address (0.0.0.0) since
167 the IPv4 address has not yet been assigned.
171 Priority 90 flow to allow IPv6 traffic if it has IPv6 addresses
172 which match the <code>inport</code>, valid <code>eth.src</code> and
173 valid <code>ip6.src</code> address(es).
177 Priority 90 flow to allow IPv6 DAD (Duplicate Address Detection)
178 traffic if it has a valid <code>eth.src</code>. This is is
179 necessary since DAD include requires joining an multicast group and
180 sending neighbor solicitations for the newly assigned address. Since
181 no address is yet assigned, these are sent from the unspecified
186 Priority 80 flow to drop IP (both IPv4 and IPv6) traffic which
187 match the <code>inport</code> and valid <code>eth.src</code>.
193 One priority-0 fallback flow that matches all packets and advances to
198 <h3>Ingress Table 2: Ingress Port Security - Neighbor discovery</h3>
201 Ingress table 2 contains these logical flows:
207 For each element in the port security set,
212 Priority 90 flow to allow ARP traffic which match the
213 <code>inport</code> and valid <code>eth.src</code> and
214 <code>arp.sha</code>. If the element has one or more
215 IPv4 addresses, then it also matches the valid
216 <code>arp.spa</code>.
220 Priority 90 flow to allow IPv6 Neighbor Solicitation and
221 Advertisement traffic which match the <code>inport</code>,
222 valid <code>eth.src</code> and
223 <code>nd.sll</code>/<code>nd.tll</code>.
224 If the element has one or more IPv6 addresses, then it also
225 matches the valid <code>nd.target</code> address(es) for Neighbor
226 Advertisement traffic.
230 Priority 80 flow to drop ARP and IPv6 Neighbor Solicitation and
231 Advertisement traffic which match the <code>inport</code> and
232 valid <code>eth.src</code>.
238 One priority-0 fallback flow that matches all packets and advances to
243 <h3>Ingress Table 3: <code>from-lport</code> Pre-ACLs</h3>
246 This table prepares flows for possible stateful ACL processing in
247 ingress table <code>ACLs</code>. It contains a priority-0 flow that
248 simply moves traffic to the next table. If stateful ACLs are used in the
249 logical datapath, a priority-100 flow is added that sends IP packets to
250 the connection tracker before advancing to ingress table
254 <h3>Ingress table 4: <code>from-lport</code> ACLs</h3>
257 Logical flows in this table closely reproduce those in the
258 <code>ACL</code> table in the <code>OVN_Northbound</code> database
259 for the <code>from-lport</code> direction. <code>allow</code>
260 ACLs translate into logical flows with the <code>next;</code>
261 action, <code>allow-related</code> ACLs translate into logical
262 flows with the <code>ct_commit; next;</code> actions, other ACLs
263 translate to <code>drop;</code>. The <code>priority</code> values
264 from the <code>ACL</code> table have a limited range and have 1000
265 added to them to leave room for OVN default flows at both higher
266 and lower priorities.
270 This table also contains a priority 0 flow with action
271 <code>next;</code>, so that ACLs allow packets by default. If the
272 logical datapath has a statetful ACL, the following flows will
278 A priority-1 flow to commit IP traffic to the connection
279 tracker. This is needed for the default allow policy because,
280 while the initiater's direction may not have any stateful rules,
281 the server's may and then its return traffic would not be known
282 and marked as invalid.
286 A priority-65535 flow that allows any traffic that has been
287 committed to the connection tracker (i.e., established flows).
291 A priority-65535 flow that allows any traffic that is considered
292 related to a committed flow in the connection tracker (e.g., an
293 ICMP Port Unreachable from a non-listening UDP port).
297 A priority-65535 flow that drops all traffic marked by the
298 connection tracker as invalid.
302 <h3>Ingress Table 5: ARP responder</h3>
305 This table implements ARP responder for known IPs. It contains these
311 Priority-100 flows to skip ARP responder if inport is of type
312 <code>localnet</code>, and advances directly to the next table.
317 Priority-50 flows that matches ARP requests to each known IP address
318 <var>A</var> of logical port <var>P</var>, and respond with ARP
319 replies directly with corresponding Ethernet address <var>E</var>:
324 eth.src = <var>E</var>;
325 arp.op = 2; /* ARP reply. */
327 arp.sha = <var>E</var>;
329 arp.spa = <var>A</var>;
330 outport = <var>P</var>;
331 inport = ""; /* Allow sending out inport. */
336 These flows are omitted for logical ports (other than router ports)
342 One priority-0 fallback flow that matches all packets and advances to
347 <h3>Ingress Table 6: Destination Lookup</h3>
350 This table implements switching behavior. It contains these logical
356 A priority-100 flow that outputs all packets with an Ethernet broadcast
357 or multicast <code>eth.dst</code> to the <code>MC_FLOOD</code>
358 multicast group, which <code>ovn-northd</code> populates with all
359 enabled logical ports.
363 One priority-50 flow that matches each known Ethernet address against
364 <code>eth.dst</code> and outputs the packet to the single associated
369 One priority-0 fallback flow that matches all packets and outputs them
370 to the <code>MC_UNKNOWN</code> multicast group, which
371 <code>ovn-northd</code> populates with all enabled logical ports that
372 accept unknown destination packets. As a small optimization, if no
373 logical ports accept unknown destination packets,
374 <code>ovn-northd</code> omits this multicast group and logical flow.
378 <h3>Egress Table 0: <code>to-lport</code> Pre-ACLs</h3>
381 This is similar to ingress table <code>Pre-ACLs</code> except for
382 <code>to-lport</code> traffic.
385 <h3>Egress Table 1: <code>to-lport</code> ACLs</h3>
388 This is similar to ingress table <code>ACLs</code> except for
389 <code>to-lport</code> ACLs.
392 <h3>Egress Table 2: Egress Port Security - IP</h3>
395 This is similar to the port security logic in table
396 <code>Ingress Port Security - IP</code> except that <code>outport</code>,
397 <code>eth.dst</code>, <code>ip4.dst</code> and <code>ip6.dst</code>
398 are checked instead of <code>inport</code>, <code>eth.src</code>,
399 <code>ip4.src</code> and <code>ip6.src</code>
402 <h3>Egress Table 3: Egress Port Security - L2</h3>
405 This is similar to the ingress port security logic in ingress table
406 <code>Admission Control and Ingress Port Security - L2</code>,
407 but with important differences. Most obviously, <code>outport</code> and
408 <code>eth.dst</code> are checked instead of <code>inport</code> and
409 <code>eth.src</code>. Second, packets directed to broadcast or multicast
410 <code>eth.dst</code> are always accepted instead of being subject to the
411 port security rules; this is implemented through a priority-100 flow that
412 matches on <code>eth.mcast</code> with action <code>output;</code>.
413 Finally, to ensure that even broadcast and multicast packets are not
414 delivered to disabled logical ports, a priority-150 flow for each
415 disabled logical <code>outport</code> overrides the priority-100 flow
416 with a <code>drop;</code> action.
419 <h2>Logical Router Datapaths</h2>
422 Logical router datapaths will only exist for <ref table="Logical_Router"
423 db="OVN_Northbound"/> rows in the <ref db="OVN_Northbound"/> database
424 that do not have <ref column="enabled" table="Logical_Router"
425 db="OVN_Northbound"/> set to <code>false</code>
428 <h3>Ingress Table 0: L2 Admission Control</h3>
431 This table drops packets that the router shouldn't see at all based on
432 their Ethernet headers. It contains the following flows:
437 Priority-100 flows to drop packets with VLAN tags or multicast Ethernet
442 For each enabled router port <var>P</var> with Ethernet address
443 <var>E</var>, a priority-50 flow that matches <code>inport ==
444 <var>P</var> && (eth.mcast || eth.dst ==
445 <var>E</var></code>), with action <code>next;</code>.
450 Other packets are implicitly dropped.
453 <h3>Ingress Table 1: IP Input</h3>
456 This table is the core of the logical router datapath functionality. It
457 contains the following flows to implement very basic IP host
464 L3 admission control: A priority-100 flow drops packets that match
465 any of the following:
470 <code>ip4.src[28..31] == 0xe</code> (multicast source)
473 <code>ip4.src == 255.255.255.255</code> (broadcast source)
476 <code>ip4.src == 127.0.0.0/8 || ip4.dst == 127.0.0.0/8</code>
477 (localhost source or destination)
480 <code>ip4.src == 0.0.0.0/8 || ip4.dst == 0.0.0.0/8</code> (zero
481 network source or destination)
484 <code>ip4.src</code> is any IP address owned by the router.
487 <code>ip4.src</code> is the broadcast address of any IP network
495 ICMP echo reply. These flows reply to ICMP echo requests received
496 for the router's IP address. Let <var>A</var> be an IP address
497 owned by a router port. Then, for each <var>A</var>, a priority-90
498 flow matches on <code>ip4.dst == <var>A</var></code> and <code>
499 icmp4.type == 8 && icmp4.code == 0</code> (ICMP echo
500 request). The port of the router that receives the echo request
501 does not matter. Also, the ip.ttl of the echo request packet is not
502 checked, so it complies with RFC 1812, section 4.2.2.9. These flows
503 use the following actions where <var>S</var> is the router's IP
509 ip4.src = <var>S</var>;
512 inport = ""; /* Allow sending out inport. */
519 Reply to ARP requests.
523 These flows reply to ARP requests for the router's own IP address.
524 For each router port <var>P</var> that owns IP address <var>A</var>
525 and Ethernet address <var>E</var>, a priority-90 flow matches
526 <code>inport == <var>P</var> && arp.op == 1 &&
527 arp.tpa == <var>A</var></code> (ARP request) with the following
533 eth.src = <var>E</var>;
534 arp.op = 2; /* ARP reply. */
536 arp.sha = <var>E</var>;
538 arp.spa = <var>A</var>;
539 outport = <var>P</var>;
540 inport = ""; /* Allow sending out inport. */
547 These flows reply to ARP requests for the virtual IP addresses
548 configured in the router for DNAT. For a configured DNAT IP address
549 <var>A</var>, for each router port <var>P</var> with Ethernet
550 address <var>E</var>, a priority-90 flow matches
551 <code>inport == <var>P</var> && arp.op == 1 &&
552 arp.tpa == <var>A</var></code> (ARP request)
553 with the following actions:
558 eth.src = <var>E</var>;
559 arp.op = 2; /* ARP reply. */
561 arp.sha = <var>E</var>;
563 arp.spa = <var>A</var>;
564 outport = <var>P</var>;
565 inport = ""; /* Allow sending out inport. */
571 ARP reply handling. These flows use ARP replies to populate the
572 logical router's ARP table. A priority-90 flow with match <code>arp.op
573 == 2</code> has actions <code>put_arp(inport, arp.spa,
579 UDP port unreachable. Priority-80 flows generate ICMP port
580 unreachable messages in reply to UDP datagrams directed to the
581 router's IP address. The logical router doesn't accept any UDP
582 traffic so it always generates such a reply.
586 These flows should not match IP fragments with nonzero offset.
590 Details TBD. Not yet implemented.
596 TCP reset. Priority-80 flows generate TCP reset messages in reply to
597 TCP datagrams directed to the router's IP address. The logical
598 router doesn't accept any TCP traffic so it always generates such a
603 These flows should not match IP fragments with nonzero offset.
607 Details TBD. Not yet implemented.
613 Protocol unreachable. Priority-70 flows generate ICMP protocol
614 unreachable messages in reply to packets directed to the router's IP
615 address on IP protocols other than UDP, TCP, and ICMP.
619 These flows should not match IP fragments with nonzero offset.
623 Details TBD. Not yet implemented.
628 Drop other IP traffic to this router. These flows drop any other
629 traffic destined to an IP address of this router that is not already
630 handled by one of the flows above, which amounts to ICMP (other than
631 echo requests) and fragments with nonzero offsets. For each IP address
632 <var>A</var> owned by the router, a priority-60 flow matches
633 <code>ip4.dst == <var>A</var></code> and drops the traffic. An
634 exception is made and the above flow is not added if the router
635 port's own IP address is used to SNAT packets passing through that
641 The flows above handle all of the traffic that might be directed to the
642 router itself. The following flows (with lower priorities) handle the
643 remaining traffic, potentially for forwarding:
648 Drop Ethernet local broadcast. A priority-50 flow with match
649 <code>eth.bcast</code> drops traffic destined to the local Ethernet
650 broadcast address. By definition this traffic should not be forwarded.
654 Drop IP multicast. A priority-50 flow with match
655 <code>ip4.mcast</code> drops IP multicast traffic.
660 ICMP time exceeded. For each router port <var>P</var>, whose IP
661 address is <var>A</var>, a priority-40 flow with match <code>inport
662 == <var>P</var> && ip.ttl == {0, 1} &&
663 !ip.later_frag</code> matches packets whose TTL has expired, with the
664 following actions to send an ICMP time exceeded reply:
669 icmp4.type = 11; /* Time exceeded. */
670 icmp4.code = 0; /* TTL exceeded in transit. */
672 ip4.src = <var>A</var>;
684 TTL discard. A priority-30 flow with match <code>ip.ttl == {0,
685 1}</code> and actions <code>drop;</code> drops other packets whose TTL
686 has expired, that should not receive a ICMP error reply (i.e. fragments
687 with nonzero offset).
691 Next table. A priority-0 flows match all packets that aren't already
692 handled and uses actions <code>next;</code> to feed them to the ingress
697 <h3>Ingress Table 2: UNSNAT</h3>
700 This is for already established connections' reverse traffic.
701 i.e., SNAT has already been done in egress pipeline and now the
702 packet has entered the ingress pipeline as part of a reply. It is
709 For each configuration in the OVN Northbound database, that asks
710 to change the source IP address of a packet from <var>A</var> to
711 <var>B</var>, a priority-100 flow matches <code>ip &&
712 ip4.dst == <var>B</var></code> with an action
713 <code>ct_snat; next;</code>.
717 A priority-0 logical flow with match <code>1</code> has actions
723 <h3>Ingress Table 3: DNAT</h3>
726 Packets enter the pipeline with destination IP address that needs to
727 be DNATted from a virtual IP address to a real IP address. Packets
728 in the reverse direction needs to be unDNATed.
733 For each configuration in the OVN Northbound database, that asks
734 to change the destination IP address of a packet from <var>A</var> to
735 <var>B</var>, a priority-100 flow matches <code>ip &&
736 ip4.dst == <var>A</var></code> with an action <code>inport = "";
737 ct_dnat(<var>B</var>);</code>.
741 For all IP packets of a Gateway router, a priority-50 flow with an
742 action <code>inport = ""; ct_dnat;</code>.
746 A priority-0 logical flow with match <code>1</code> has actions
752 <h3>Ingress Table 4: IP Routing</h3>
755 A packet that arrives at this table is an IP packet that should be routed
756 to the address in <code>ip4.dst</code>. This table implements IP
757 routing, setting <code>reg0</code> to the next-hop IP address (leaving
758 <code>ip4.dst</code>, the packet's final destination, unchanged) and
759 advances to the next table for ARP resolution. It also sets
760 <code>reg1</code> to the IP address owned by the selected router port
761 (which is used later in table 6 as the IP source address for an ARP
766 This table contains the following logical flows:
772 Routing table. For each route to IPv4 network <var>N</var> with
773 netmask <var>M</var>, on router port <var>P</var> with IP address
774 <var>A</var> and Ethernet
775 address <var>E</var>, a logical flow with match <code>ip4.dst ==
776 <var>N</var>/<var>M</var></code>, whose priority is the number of
777 1-bits in <var>M</var>, has the following actions:
784 eth.src = <var>E</var>;
785 outport = <var>P</var>;
790 (Ingress table 1 already verified that <code>ip.ttl--;</code> will
791 not yield a TTL exceeded error.)
795 If the route has a gateway, <var>G</var> is the gateway IP address.
796 Instead, if the route is from a configured static route, <var>G</var>
797 is the next hop IP address. Else it is <code>ip4.dst</code>.
803 Destination unreachable. For each router port <var>P</var>, which
804 owns IP address <var>A</var>, a priority-0 logical flow with match
805 <code>in_port == <var>P</var> && !ip.later_frag &&
806 !icmp</code> has the following actions:
811 icmp4.type = 3; /* Destination unreachable. */
812 icmp4.code = 0; /* Network unreachable. */
814 ip4.src = <var>A</var>;
821 (The <code>!icmp</code> check prevents recursion if the destination
822 unreachable message itself cannot be routed.)
826 These flows are omitted if the logical router has a default route,
827 that is, a route with netmask 0.0.0.0.
832 <h3>Ingress Table 5: ARP Resolution</h3>
835 Any packet that reaches this table is an IP packet whose next-hop IP
836 address is in <code>reg0</code>. (<code>ip4.dst</code> is the final
837 destination.) This table resolves the IP address in <code>reg0</code>
838 into an output port in <code>outport</code> and an Ethernet address in
839 <code>eth.dst</code>, using the following flows:
845 Static MAC bindings. MAC bindings can be known statically based on
846 data in the <code>OVN_Northbound</code> database. For router ports
847 connected to logical switches, MAC bindings can be known statically
848 from the <code>addresses</code> column in the
849 <code>Logical_Switch_Port</code> table. For router ports
850 connected to other logical routers, MAC bindings can be known
851 statically from the <code>mac</code> and <code>network</code>
852 column in the <code>Logical_Router_Port</code> table.
856 For each IP address <var>A</var> whose host is known to have Ethernet
857 address <var>E</var> on router port <var>P</var>, a priority-100 flow
858 with match <code>outport === <var>P</var> && reg0 ==
859 <var>A</var></code> has actions <code>eth.dst = <var>E</var>;
864 For each logical router port with an IP address <var>A</var> and
865 a mac address of <var>E</var> that is reachable via a different
866 logical router port <var>P</var>, a priority-100 flow with
867 match <code>outport === <var>P</var> && reg0 ==
868 <var>A</var></code> has actions <code>eth.dst = <var>E</var>;
875 Dynamic MAC bindings. This flows resolves MAC-to-IP bindings that
876 have become known dynamically through ARP. (The next table will
877 issue an ARP request for cases where the binding is not yet known.)
881 A priority-0 logical flow with match <code>1</code> has actions
882 <code>get_arp(outport, reg0); next;</code>.
887 <h3>Ingress Table 6: ARP Request</h3>
890 In the common case where the Ethernet destination has been resolved, this
891 table outputs the packet. Otherwise, it composes and sends an ARP
892 request. It holds the following flows:
898 Unknown MAC address. A priority-100 flow with match <code>eth.dst ==
899 00:00:00:00:00:00</code> has the following actions:
904 eth.dst = ff:ff:ff:ff:ff:ff;
906 arp.op = 1; /* ARP request. */
912 (Ingress table 4 initialized <code>reg1</code> with the IP address
913 owned by <code>outport</code>.)
917 The IP packet that triggers the ARP request is dropped.
922 Known MAC address. A priority-0 flow with match <code>1</code> has
923 actions <code>output;</code>.
927 <h3>Egress Table 0: SNAT</h3>
930 Packets that are configured to be SNATed get their source IP address
931 changed based on the configuration in the OVN Northbound database.
936 For each configuration in the OVN Northbound database, that asks
937 to change the source IP address of a packet from an IP address of
938 <var>A</var> or to change the source IP address of a packet that
939 belongs to network <var>A</var> to <var>B</var>, a flow matches
940 <code>ip && ip4.src == <var>A</var></code> with an action
941 <code>ct_snat(<var>B</var>);</code>. The priority of the flow
942 is calculated based on the mask of <var>A</var>, with matches
943 having larger masks getting higher priorities.
946 A priority-0 logical flow with match <code>1</code> has actions
952 <h3>Egress Table 1: Delivery</h3>
955 Packets that reach this table are ready for delivery. It contains
956 priority-100 logical flows that match packets on each enabled logical
957 router port, with action <code>output;</code>.