Appendix O: Open Virtual Network (OVN)¶
Overview¶
As of the 19.10 OpenStack Charms release, with OpenStack Train or later, support for integration with Open Virtual Network (OVN) is available. As of the 20.05 OpenStack Charms release OVN is the preferred default for our OpenStack Base bundle reference implementation.
Note
There are feature gaps from ML2/OVS and deploying legacy ML2/OVS with the OpenStack Charms is still available.
OVN charms:
neutron-api-plugin-ovn
ovn-central
ovn-chassis
ovn-dedicated-chassis
Deployment¶
OVN makes use of Public Key Infrastructure (PKI) to authenticate and authorize
control plane communication. The charm requires a Certificate Authority to be
present in the model as represented by the certificates
relation.
Follow the instructions for deployment and configuration of Vault in the Vault and Certificate Lifecycle Management appendices.
OVN can then be deployed:
juju config neutron-api manage-neutron-plugin-legacy-mode=false
juju deploy neutron-api-plugin-ovn
juju deploy ovn-central -n 3 --config source=cloud:bionic-ussuri
juju deploy ovn-chassis
juju add-relation neutron-api-plugin-ovn:certificates vault:certificates
juju add-relation neutron-api-plugin-ovn:neutron-plugin \
neutron-api:neutron-plugin-api-subordinate
juju add-relation neutron-api-plugin-ovn:ovsdb-cms ovn-central:ovsdb-cms
juju add-relation ovn-central:certificates vault:certificates
juju add-relation ovn-chassis:ovsdb ovn-central:ovsdb
juju add-relation ovn-chassis:certificates vault:certificates
juju add-relation ovn-chassis:nova-compute nova-compute:neutron-plugin
The OVN components used for the data plane is deployed by the ovn-chassis subordinate charm. A subordinate charm is deployed together with a principle charm, nova-compute in the example above.
If you require a dedicated software gateway you may deploy the data plane components as a principle charm through the use of the ovn-dedicated-chassis charm.
Note
For a concrete example take a look at the OpenStack Base bundle.
High availability¶
OVN is HA by design; take a look at the OVN section of the OpenStack high availability appendix.
Configuration¶
OVN integrates with OpenStack through the OVN ML2 driver. On OpenStack Ussuri and onwards the OVN ML2 driver is maintained as an in-tree driver in Neutron. On OpenStack Train it is maintained separately as per the networking-ovn plugin.
General Neutron configuration is still done through the neutron-api charm, and the subset of configuration specific to OVN is done through the neutron-api-plugin-ovn charm.
Hardware offloading support¶
It is possible to configure chassis to prepare network interface cards (NICs) for use with hardware offloading and make them available to OpenStack.
Warning
Support for hardware offload in conjunction with OVN is an experimental feature. OVN programs flow tables in a different way than legacy ML2+OVS and this has had less exposure to validation in NIC firmware and driver support.
To use the feature you need to use supported network interface card (NIC) hardware. We have done feature validation using the Mellanox ConnectX-5 NICs.
Please refer to the NIC hardware offload appendix for more background on the feature.
Hardware offload support makes use of SR-IOV as an underlying mechanism to accelerate the data path between a virtual machine instance and the NIC hardware. But as opposed to traditional SR-IOV support the accelerated ports can be connected to the Open vSwitch integration bridge which allows instances to take part in regular tenant networks. The NIC also supports hardware offloading of tunnel encapsulation and decapsulation.
With OVN the Layer3 routing features are implemented as flow rules in Open vSwitch. This in turn may allow Layer 3 routing to also be offloaded to NICs with appropriate driver and firmware support.
Prerequisites¶
Please refer to the SR-IOV for networking support section and the NIC hardware offload appendix for information on hardware and kernel configuration.
Charm configuration¶
The below example bundle excerpt will enable hardware offloading for an OVN deployment.
applications:
ovn-chassis:
charm: cs:ovn-chassis
options:
enable-hardware-offload: true
sriov-numvfs: "enp3s0f0:64 enp3s0f1:0"
neutron-api:
charm: cs:neutron-api
options:
enable-hardware-offload: true
nova-compute:
charm: cs:nova-compute
options:
pci-passthrough-whitelist: '{"address": "*:03:*", "physical_network": null}'
Boot an instance¶
Now we can tell OpenStack to boot an instance and attach it to an hardware
offloaded port. This must be done in two stages, first we create a port with
vnic-type
‘direct’ and binding-profile
with ‘switchdev’ capabilities.
Then we create an instance connected to the newly created port:
openstack port create --network my-network --vnic-type direct \
--binding-profile '{"capabilities": ["switchdev"]}' direct_port1
openstack server create --flavor my-flavor --key-name my-key \
--nic port-id=direct_port1 my-instance
Validate that traffic is offloaded¶
The traffic control monitor command can be used to observe updates to filters which is one of the mechanisms used to program the NIC switch hardware. Look for the ‘in_hw’ and ‘not_in_hw’ labels.
sudo tc monitor
replaced filter dev eth62 ingress protocol ip pref 3 flower chain 0 handle 0x9
dst_mac fa:16:3e:b2:20:82
src_mac fa:16:3e:b9:db:c8
eth_type ipv4
ip_proto tcp
ip_tos 67deeb90
dst_ip 10.42.0.17/28
tcp_flags 22
ip_flags nofrag
in_hw
action order 1: tunnel_key set
src_ip 0.0.0.0
dst_ip 10.6.12.8
key_id 4
dst_port 6081
csum pipe
index 15 ref 1 bind 1
action order 2: mirred (Egress Redirect to device genev_sys_6081) stolen
index 18 ref 1 bind 1
cookie d4885b4d38419f7fd7ae77a11bc78b0b
Open vSwitch has a rich set of tools to monitor traffic flows and you can use the data path control tools to monitor offloaded flows.
sudo ovs-appctl dpctl/dump-flows type=offloaded
tunnel(tun_id=0x4,src=10.6.12.3,dst=10.6.12.7,tp_dst=6081,geneve({class=0x102,type=0x80,len=4,0x20007/0x7fffffff}),flags(+key)),recirc_id(0),in_port(2),eth(src=fa:16:3e:f8:52:5c,dst=00:00:00:00:00:00/01:00:00:00:00:00),eth_type(0x0800),ipv4(proto=6,frag=no),tcp_flags(psh|ack), packets:2, bytes:204, used:5.710s, actions:7
tunnel(tun_id=0x4,src=10.6.12.3,dst=10.6.12.7,tp_dst=6081,geneve({class=0x102,type=0x80,len=4,0x20007/0x7fffffff}),flags(+key)),recirc_id(0),in_port(2),eth(src=fa:16:3e:f8:52:5c,dst=00:00:00:00:00:00/01:00:00:00:00:00),eth_type(0x0800),ipv4(proto=6,frag=no),tcp_flags(ack), packets:3, bytes:230, used:5.710s, actions:7
tunnel(tun_id=0x4,src=10.6.12.8,dst=10.6.12.7,tp_dst=6081,geneve({class=0x102,type=0x80,len=4,0x60007/0x7fffffff}),flags(+key)),recirc_id(0),in_port(2),eth(src=fa:16:3e:b2:20:82,dst=00:00:00:00:00:00/01:00:00:00:00:00),eth_type(0x0800),ipv4(proto=6,frag=no),tcp_flags(syn|ack), packets:0, bytes:0, used:6.740s, actions:7
tunnel(tun_id=0x4,src=10.6.12.8,dst=10.6.12.7,tp_dst=6081,geneve({class=0x102,type=0x80,len=4,0x60007/0x7fffffff}),flags(+key)),recirc_id(0),in_port(2),eth(src=fa:16:3e:b2:20:82,dst=00:00:00:00:00:00/01:00:00:00:00:00),eth_type(0x0800),ipv4(proto=6,frag=no),tcp_flags(ack), packets:180737, bytes:9400154, used:0.000s, actions:7
recirc_id(0),in_port(6),eth(src=26:8a:07:82:a7:2f,dst=01:80:c2:00:00:0e),eth_type(0x88cc), packets:5, bytes:990, used:14.340s, actions:drop
recirc_id(0),in_port(7),eth(src=fa:16:3e:b9:db:c8,dst=fa:16:3e:b2:20:82),eth_type(0x0800),ipv4(dst=10.42.0.16/255.255.255.240,proto=6,tos=0/0x3,frag=no),tcp_flags(syn), packets:0, bytes:0, used:6.910s, actions:set(tunnel(tun_id=0x4,dst=10.6.12.8,ttl=64,tp_dst=6081,key6(bad key length 1, expected 0)(01)geneve({class=0x102,type=0x80,len=4,0x70006}),flags(key))),2
recirc_id(0),in_port(7),eth(src=fa:16:3e:b9:db:c8,dst=fa:16:3e:b2:20:82),eth_type(0x0800),ipv4(dst=10.42.0.16/255.255.255.240,proto=6,tos=0/0x3,frag=no),tcp_flags(ack), packets:935904, bytes:7504070178, used:0.590s, actions:set(tunnel(tun_id=0x4,dst=10.6.12.8,ttl=64,tp_dst=6081,key6(bad key length 1, expected 0)(01)geneve({class=0x102,type=0x80,len=4,0x70006}),flags(key))),2
recirc_id(0),in_port(7),eth(src=fa:16:3e:b9:db:c8,dst=fa:16:3e:b2:20:82),eth_type(0x0800),ipv4(dst=10.42.0.16/255.255.255.240,proto=6,tos=0/0x3,frag=no),tcp_flags(psh|ack), packets:3873, bytes:31053714, used:0.590s, actions:set(tunnel(tun_id=0x4,dst=10.6.12.8,ttl=64,tp_dst=6081,key6(bad key length 1, expected 0)(01)geneve({class=0x102,type=0x80,len=4,0x70006}),flags(key))),2
SR-IOV for networking support¶
Single root I/O virtualization (SR-IOV) enables splitting a single physical network port into multiple virtual network ports known as virtual functions (VFs). The division is done at the PCI level which allows attaching the VF directly to a virtual machine instance, bypassing the networking stack of the hypervisor hosting the instance.
The main use case for this feature is to support applications with high bandwidth requirements. For such applications the normal plumbing through the userspace virtio driver in QEMU will consume too much resources from the host.
It is possible to configure chassis to prepare network interface cards (NICs) for use with SR-IOV and make them available to OpenStack.
Prerequisites¶
To use the feature you need to use a NIC with support for SR-IOV.
Machines need to be pre-configured with appropriate kernel command-line parameters. The charm does not handle this facet of configuration and it is expected that the user configure this either manually or through the bare metal provisioning layer (for example MAAS). Example:
intel_iommu=on iommu=pt probe_vf=0
Charm configuration¶
Enable SR-IOV, map physical network name ‘physnet2’ to the physical port named ‘enp3s0f0’ and create 4 virtual functions on it:
juju config ovn-chassis enable-sriov=true
juju config ovn-chassis sriov-device-mappings=physnet2:enp3s0f0
juju config ovn-chassis sriov-numvfs=enp3s0f0:4
After enabling the virtual functions you should take note of the vendor_id
and product_id
of the virtual functions:
juju run --application ovn-chassis 'lspci -nn | grep "Virtual Function"'
03:10.0 Ethernet controller [0200]: Intel Corporation 82599 Ethernet Controller Virtual Function [8086:10ed] (rev 01)
03:10.2 Ethernet controller [0200]: Intel Corporation 82599 Ethernet Controller Virtual Function [8086:10ed] (rev 01)
03:10.4 Ethernet controller [0200]: Intel Corporation 82599 Ethernet Controller Virtual Function [8086:10ed] (rev 01)
03:10.6 Ethernet controller [0200]: Intel Corporation 82599 Ethernet Controller Virtual Function [8086:10ed] (rev 01)
In the above example vendor_id
is ‘8086’ and product_id
is ‘10ed’.
Add mapping between physical network name, physical port and Open vSwitch bridge:
juju config ovn-chassis ovn-bridge-mappings=physnet2:br-ex
juju config ovn-chassis bridge-interface-mappings br-ex:a0:36:9f:dd:37:a8
Note
The above configuration allows OVN to configure an ‘external’ port on one of the chassis for providing DHCP and metadata to instances connected directly to the network through SR-IOV.
For OpenStack to make use of the VFs the neutron-sriov-agent
needs to talk
to RabbitMQ:
juju add-relation ovn-chassis:amqp rabbitmq-server:amqp
OpenStack Nova also needs to know which PCI devices it is allowed to pass through to instances:
juju config nova-compute pci-passthrough-whitelist='{"vendor_id":"8086", "product_id":"10ed", "physical_network":"physnet2"}'
Boot an instance¶
Now we can tell OpenStack to boot an instance and attach it to an SR-IOV port.
This must be done in two stages, first we create a port with vnic-type
‘direct’ and then we create an instance connected to the newly created port:
openstack port create --network my-network --vnic-type direct my-port
openstack server create --flavor my-flavor --key-name my-key \
--nic port-id=my-port my-instance
DPDK support¶
It is possible to configure chassis to use experimental DPDK userspace network acceleration.
Note
Currently instances are required to be attached to a external network (also known as provider network) for connectivity. OVN supports distributed DHCP for provider networks. For OpenStack workloads use of Nova config drive is required to provide metadata to instances.
Prerequisites¶
To use the feature you need to use a supported CPU architecture and network interface card (NIC) hardware. Please consult the DPDK supported hardware page.
Machines need to be pre-configured with appropriate kernel command-line parameters. The charm does not handle this facet of configuration and it is expected that the user configure this either manually or through the bare metal provisioning layer (for example MAAS).
Example:
default_hugepagesz=1G hugepagesz=1G hugepages=64 intel_iommu=on iommu=pt
For the communication between the host userspace networking stack and the guest virtual NIC driver to work the instances need to be configured to use hugepages. For OpenStack this can be accomplished by Customizing instance huge pages allocations.
Example:
openstack flavor set m1.large --property hw:mem_page_size=large
By default, the charm will configure Open vSwitch/DPDK to consume one processor
core + 1G of RAM from each NUMA node on the unit being deployed. This can be
tuned using the dpdk-socket-memory
and dpdk-socket-cores
configuration
options. The userspace kernel driver can be configured using the
dpdk-driver
configuration option. See config.yaml for more details.
Note
Changing dpdk related configuration options will trigger a restart of Open vSwitch, and subsequently interrupt instance connectivity.
DPDK bonding¶
Once Network interface cards are bound to DPDK they will be invisible to the standard Linux kernel network stack and subsequently it is not possible to use standard system tools to configure bonding.
For DPDK interfaces the charm supports configuring bonding in Open vSwitch.
This is accomplished through the dpdk-bond-mappings
and
dpdk-bond-config
configuration options. Example:
ovn-chassis:
options:
enable-dpdk: True
bridge-interface-mappings: br-ex:dpdk-bond0
dpdk-bond-mappings: "dpdk-bond0:00:53:00:00:00:42 dpdk-bond0:00:53:00:00:00:51"
dpdk-bond-config: ":balance-slb:off:fast"
In this example, the network interface cards associated with the two MAC addresses provided will be used to build a bond identified by a port named ‘dpdk-bond0’ which will be attached to the ‘br-ex’ bridge.
Internal DNS resolution¶
OVN supports Neutron internal DNS resolution. To configure this:
juju config neutron-api enable-ml2-dns=true
juju config neutron-api dns-domain=openstack.example.
juju config neutron-api-plugin-api dns-servers="1.1.1.1 8.8.8.8"
Note
The value for the dns-domain
configuration option must
not be set to ‘openstack.local.’ as that will effectively disable the
feature.
It is also important to end the string with a ‘.’ (dot).
When you set enable-ml2-dns
to ‘true’ and set a value for dns-domain
,
Neutron will add details such as instance name and DNS domain name to each
individual Neutron port associated with instances. The OVN ML2 driver will
populate the DNS
table of the Northbound and Southbound databases:
# ovn-sbctl list DNS
_uuid : 2e149fa8-d27f-4106-99f5-a08f60c443bf
datapaths : [b25ed99a-89f1-49cc-be51-d215aa6fb073]
external_ids : {dns_id="4c79807e-0755-4d17-b4bc-eb57b93bf78d"}
records : {"c-1"="192.0.2.239", "c-1.openstack.example"="192.0.2.239"}
On the chassis, OVN creates flow rules to redirect UDP port 53 packets (DNS)
to the local ovn-controller
process:
cookie=0xdeaffed, duration=77.575s, table=22, n_packets=0, n_bytes=0, idle_age=77, priority=100,udp6,metadata=0x2,tp_dst=53 actions=controller(userdata=00.00.00.06.00.00.00.00.00.01.de.10.00.00.00.64,pause),resubmit(,23)
cookie=0xdeaffed, duration=77.570s, table=22, n_packets=0, n_bytes=0, idle_age=77, priority=100,udp,metadata=0x2,tp_dst=53 actions=controller(userdata=00.00.00.06.00.00.00.00.00.01.de.10.00.00.00.64,pause),resubmit(,23)
The local ovn-controller
process then decides if it should respond to the
DNS query directly or if it needs to be forwarded to the real DNS server.
External connectivity¶
Interface and network to bridge mapping is done through the ovn-chassis charm.
OVN provides a more flexible way of configuring external Layer3 networking than
the legacy ML2+DVR configuration as OVN does not require every node
(Chassis
in OVN terminology) in a deployment to have direct external
connectivity. This plays nicely with Layer3-only datacenter fabrics (RFC 7938).
East/West traffic is distributed by default. North/South traffic is highly available by default. Liveness detection is done using the Bidirectional Forwarding Detection (BFD) protocol.
Networks for use with external Layer3 connectivity should have mappings on chassis located in the vicinity of the datacenter border gateways. Having two or more chassis with mappings for a Layer3 network will have OVN automatically configure highly available routers with liveness detection provided by the Bidirectional Forwarding Detection (BFD) protocol.
Chassis without direct external mapping to a external Layer3 network will forward traffic through a tunnel to one of the chassis acting as a gateway for that network.
Note
It is not necessary nor recommended to add mapping for external Layer3 networks to all chassis. Doing so will create a scaling problem at the physical network layer that needs to be resolved with globally shared Layer2 (does not scale) or tunneling at the top-of-rack switch layer (adds complexity) and is generally not a recommended configuration.
Example configuration:
juju config neutron-api flat-network-providers=physnet1
juju config ovn-chassis ovn-bridge-mappings=physnet1:br-provider
juju config ovn-chassis \
bridge-interface-mappings='br-provider:00:00:5e:00:00:42 \
br-provider:00:00:5e:00:00:51'
openstack network create --external --share --provider-network-type flat \
--provider-physical-network physnet1 ext-net
openstack subnet create --network ext-net \
--subnet-range 192.0.2.0/24 \
--no-dhcp --gateway 192.0.2.1 \
ext
Networks for use with external Layer2 connectivity should have mappings present on all chassis with potential to host the consuming payload.
Usage¶
Create networks, routers and subnets through the OpenStack API or CLI as you normally would.
The OVN ML2 driver will translate the OpenStack network constructs into high level logical rules in the OVN Northbound database.
The ovn-northd
daemon in turn translates this into data in the Southbound
database.
The local ovn-controller
daemon on each chassis consumes these rules and
programs flows in the local Open vSwitch database.
Information queries¶
The OVN databases are configured to use the Clustered Database Service Model. In this configuration only the leader processes transactions and the administrative client tools are configured to require a connection to the leader to operate.
The leader of the Northbound and Southbound databases does not have to coincide with the charm leader, so before querying databases you must consult the output of juju status to check which unit is the leader of the database you want to query. Example:
juju status ovn-central
Unit Workload Agent Machine Public address Ports Message
ovn-central/0* active idle 0/lxd/5 10.246.114.39 6641/tcp,6642/tcp Unit is ready (leader: ovnnb_db)
ovn-central/1 active idle 1/lxd/4 10.246.114.15 6641/tcp,6642/tcp Unit is ready (northd: active)
ovn-central/2 active idle 2/lxd/2 10.246.114.27 6641/tcp,6642/tcp Unit is ready (leader: ovnsb_db)
In the above example ‘ovn-central/0’ is the leader for the Northbound DB,
‘ovn-central/1’ has the active ovn-northd
daemon and ‘ovn-central/2’ is the
leader for the Southbound DB.
OVSDB Cluster status¶
The cluster status as conveyed through juju status is updated each time a hook is run, in some circumstances it may be necessary to get an immediate view of the current cluster status.
To get an immediate view of the database clusters:
juju run --application ovn-central 'ovn-appctl -t \
/var/run/ovn/ovnnb_db.ctl cluster/status OVN_Northbound'
juju run --application ovn-central 'ovn-appctl -t \
/var/run/ovn/ovnsb_db.ctl cluster/status OVN_Southbound'
Querying DBs¶
To query the individual databases:
juju run --unit ovn-central/0 'ovn-nbctl show'
juju run --unit ovn-central/2 'ovn-sbctl show'
juju run --unit ovn-central/2 'ovn-sbctl lflow-list'
As an alternative you may provide the administrative client tools with command-line arguments for path to certificates and IP address of servers so that you can run the client from anywhere:
ovn-nbctl \
-p /etc/ovn/key_host \
-C /etc/ovn/ovn-central.crt \
-c /etc/ovn/cert_host \
--db ssl:10.246.114.39:6641,ssl:10.246.114.15:6641,ssl:10.246.114.27:6641 \
show
Note that for remote administrative write access to the Southbound DB you must use port number ‘16642’. This is due to OVN RBAC being enabled on the standard ‘6642’ port:
ovn-sbctl \
-p /etc/ovn/key_host \
-C /etc/ovn/ovn-central.crt \
-c /etc/ovn/cert_host \
--db ssl:10.246.114.39:16642,ssl:10.246.114.15:16642,ssl:10.246.114.27:16642 \
show
Data plane flow tracing¶
SSH into one of the chassis units to get access to various diagnostic tools:
juju ssh ovn-chassis/0
sudo ovs-vsctl show
sudo ovs-ofctl -O OpenFlow13 dump-flows br-int
sudo ovs-appctl -t ovs-vswitchd \
ofproto/trace br-provider \
in_port=enp3s0f0,icmp,nw_src=192.0.2.1,nw_dst=192.0.2.100'
sudo ovn-trace \
-p /etc/ovn/key_host \
-C /etc/ovn/ovn-chassis.crt \
-c /etc/ovn/cert_host \
--db ssl:10.246.114.39:6642,ssl:10.246.114.15:6642,ssl:10.246.114.27:6642 \
--ovs ext-net 'inport=="provnet-dde76bc9-0620-44f7-b99a-99cfc66e1095" && \
eth.src==30:e1:71:5c:7a:b5 && \
eth.dst==fa:16:3e:f7:15:73 && \
ip4.src==10.172.193.250 && \
ip4.dst==10.246.119.8 && \
icmp4.type==8 && \
ip.ttl == 64'
Note
OVN makes use of OpenFlow 1.3 or newer and as such the charm configures bridges to use these protocols. To be able to successfully use the ovs-ofctl command you must specify the OpenFlow version as shown in the example above.
You may issue the ovs-vsctl list bridge command to show what protocols are enabled on the bridges.
Migration from Neutron ML2+OVS to ML2+OVN¶
MTU considerations¶
When migrating from ML2+OVS to ML2+OVN there will be a change of encapsulation
for the tunnels in the overlay network to geneve
. A side effect of the
change of encapsulation is that the packets transmitted on the physical network
get larger.
You must examine the existing configuration of network equipment, physical links on hypervisors and configuration of existing virtual project networks to determine if there is room for this growth.
Making room for the growth could be accomplished by increasing the MTU configuration on the physical network equipment and hypervisor physical links. If this can be done then steps #1 and #9 below can be skipped, where it is shown how to reduce the MTU on all existing cloud instances.
Remember to take any other encapsulation used in your physical network equipment into account when calculating the MTU (VLAN tags, MPLS labels etc.).
Encapsulation types and their overhead:
Encapsulation |
Overhead |
Difference from Geneve |
---|---|---|
Geneve |
38 Bytes |
0 Bytes |
VXLAN |
30 Bytes |
8 Bytes |
GRE |
22 Bytes |
16 bytes |
Confirmation of migration actions¶
Many of the actions used for the migration require a confirmation from the
operator by way of the i-really-mean-it
parameter.
This parameter accepts the values ‘true’ or ‘false’. If ‘false’ the requested operation will either not be performed, or will be performed in dry-run mode, if ‘true’ the requested operation will be performed.
In the examples below the parameter will not be listed, this is deliberate to avoid accidents caused by cutting and pasting the wrong command into a terminal.
Prepare for migration¶
This section contains the preparation steps that will ensure minimal instance down time during the migration. Ensure that you have studied them in advance of the actual migration.
Important
Allow for at least 24 hours to pass between the completion of the preparation steps and the commencement of the actual migration steps. This is particularly necesseary because depending on your physical network configuration, it may be required to reduce the MTU size on all cloud instances as part of the migration.
Reduce MTU on all instances in the cloud if required
Please refer to the MTU considerations section above.
Instances using DHCP can be controlled centrally by the cloud operator by overriding the MTU advertised by the DHCP server.
juju config neutron-gateway instance-mtu=1300 juju config neutron-openvswitch instance-mtu=1300
Instances using IPv6 RA or SLAAC will automatically adjust their MTU as soon as OVN takes over announcing the RAs.
Any instances not using DHCP must be configured manually by the end user of the instance.
Confirm cloud subnet configuration
Confirm that all subnets have IP addresses available for allocation.
During the migration OVN may create a new port in subnets and allocate an IP address to it. Depending on the type of network, this port will be used for either the OVN metadata service or for the SNAT address assigned to an external router interface.
Warning
If a subnet has no free IP addresses for allocation the migration will fail.
Confirm that all subnets have a valid DNS server configuration.
OVN handles instance access to DNS differently to how ML2+OVS does. Please refer to the Internal DNS resolution paragraph in this document for details.
When the subnet
dns_nameservers
attribute is empty the OVN DHCP server will provide instances with the DNS addresses specified in the neutron-api-plugin-ovndns-servers
configuration option. If any of your subnets have thedns_nameservers
attribute set to the IP address ML2+OVS used for instance DNS (usually the .2 address of the project subnet) you will need to remove this configuration.
Make a fresh backup copy of the Neutron database
Deploy the OVN components and Vault
In your Juju model you can have a charm deployed multiple times using different application names. In the text below this will be referred to as “named application”. One example where this is common is for deployments with Octavia where it is common to use a separate named application for neutron-openvswtich for use with the Octavia units.
In addition to the central components you should deploy an ovn-chassis named application for every neutron-openvswitch named application in your deployment. For every neutron-gateway named application you should deploy an ovn-dedicated-chassis named application to the same set of machines.
At this point in time each hypervisor or gateway will have a Neutron Open vSwitch (OVS) agent managing the local OVS instance. Network loops may occur if an ovn-chassis unit is started as it will also attempt to manage OVS. To avoid this, deploy ovn-chassis (or ovn-dedicated-chassis) in a paused state by setting the
new-units-paused
configuration option to ‘true’:juju deploy ovn-central \ --series focal \ -n 3 \ --to lxd:0,lxd:1,lxd:2 juju deploy ovn-chassis \ --series focal \ --config new-units-paused=true \ --config bridge-interface-mappings='br-provider:00:00:5e:00:00:42' \ --config ovn-bridge-mappings=physnet1:br-provider juju deploy ovn-dedicated-chassis \ --series focal \ --config new-units-paused=true \ --config bridge-interface-mappings='br-provider:00:00:5e:00:00:51' \ --config ovn-bridge-mappings=physnet1:br-provider \ -n 2 \ --to 3,4 juju deploy --series focal mysql-router vault-mysql-router juju deploy --series focal vault juju add-relation vault-mysql-router:db-router \ mysql-innodb-cluster:db-router juju add-relation vault-mysql-router:shared-db vault:shared-db juju add-relation ovn-central:certificates vault:certificates juju add-relation ovn-chassis:certificates vault:certificates juju add-relation ovn-chassis:ovsdb ovn-central:ovsdb juju add-relation nova-compute:neutron-plugin ovn-chassis:nova-compute
The values to use for the
bridge-interface-mappings
andovn-bridge-mappings
configuration options can be found by looking at what is set for thedata-port
andbridge-mappings
configuration options on the neutron-openvswitch and/or neutron-gateway applications.Note
In the above example the placement given with the
--to
parameter to juju is just an example. Your deployment may also have multiple named applications of the neutron-openvswitch charm and/or mutliple applications related to the neutron-openvswitch named applications. You must tailor the commands to fit with your deployments topology.Unseal Vault, enable Certificate Lifecycle Management and validate that the services on ovn-central units are running as expected. Please refer to the the Usage section for more information.
Perform migration¶
Change firewall driver to ‘openvswitch’
To be able to successfully clean up after the Neutron agents on hypervisors we need to instruct the neutron-openvswitch charm to use the ‘openvswitch’ firewall driver. This is accomplished by setting the
firewall-driver
configuration option to ‘openvswitch’.juju config neutron-openvswitch firewall-driver=openvswitch
Pause neutron-openvswitch and/or neutron-gateway units.
If your deployments have two neutron-gateway units and four neutron-openvswitch units the sequence of commands would be:
juju run-action neutron-gateway/0 pause juju run-action neutron-gateway/1 pause juju run-action neutron-openvswitch/0 pause juju run-action neutron-openvswitch/1 pause juju run-action neutron-openvswitch/2 pause juju run-action neutron-openvswitch/3 pause
Deploy the Neutron OVN plugin application
juju deploy neutron-api-plugin-ovn \ --series focal \ --config dns-servers=="1.1.1.1 8.8.8.8" juju add-relation neutron-api-plugin-ovn:neutron-plugin \ neutron-api:neutron-plugin-api-subordinate juju add-relation neutron-api-plugin-ovn:certificates \ vault:certificates juju add-relation neutron-api-plugin-ovn:ovsdb-cms ovn-central:ovsdb-cms
The values to use for the
dns-servers
configuration option can be found by looking at what is set for thedns-servers
configuration option on the neutron-openvswitch and/or neutron-gateway applications.Note
The plugin will not be activated until the neutron-api
manage-neutron-plugin-legacy-mode
configuration option is changed in step 9.Adjust MTU on overlay networks (if required)
Now that 24 hours have passed since we reduced the MTU on the instances running in the cloud as described in step 1, we can update the MTU setting for each individual Neutron network:
juju run-action --wait neutron-api-plugin-ovn/0 migrate-mtu
Enable the Neutron OVN plugin
juju config neutron-api manage-neutron-plugin-legacy-mode=false
Wait for the deployment to settle.
Pause the Neutron API units
juju run-action neutron-api/0 pause juju run-action neutron-api/1 pause juju run-action neutron-api/2 pause
Wait for the deployment to settle.
Perform initial synchronization of the Neutron and OVN databases
juju run-action --wait neutron-api-plugin-ovn/0 migrate-ovn-db
(Optional) Perform Neutron database surgery to update
network_type
of overlay networks to ‘geneve’.At the time of this writing the Neutron OVN ML2 driver will assume that all chassis participating in a network are using the ‘geneve’ tunnel protocol and it will ignore the value of the network_type field in any non-physical network in the Neutron database. It will also ignore the segmentation_id field and let OVN assign the VNIs.
The Neutron API currently does not support changing the type of a network, so when doing a migration the above described behaviour is actually a welcome one.
However, after the migration is done and all the primary functions are working, i.e. packets are forwarded. The end user of the cloud will be left with the false impression of their existing ‘gre’ or ‘vxlan’ typed networks still being operational on said tunnel protocols, while in reality ‘geneve’ is used under the hood.
The end user will also run into issues with modifying any existing networks with openstack network set throwing error messages about networks of type ‘gre’ or ‘vxlan’ not being supported.
After running this action said networks will have their network_type field changed to ‘geneve’ which will fix the above described problems.
juju run-action --wait neutron-api-plugin-ovn/0 offline-neutron-morph-db
Resume the Neutron API units
juju run-action neutron-api/0 resume juju run-action neutron-api/1 resume juju run-action neutron-api/2 resume
Wait for the deployment to settle.
Migrate hypervisors and gateways
The final step of the migration is to clean up after the Neutron agents on the hypervisors/gateways and enable the OVN services so that they can reprogram the local Open vSwitch.
This can be done one gateway / hypervisor at a time or all at once to your discretion.
Note
During the migration instances running on a non-migrated hypervisor will not be able to reach instances on the migrated hypervisors.
Caution
When migrating a cloud with Neutron ML2+OVS+DVR+SNAT topology care should be taken to take into account on which hypervisors essential agents are running to minimize downtime for any instances on other hypervisors with dependencies on them.
juju run-action --wait neutron-openvswitch/0 cleanup juju run-action --wait ovn-chassis/0 resume juju run-action --wait neutron-gateway/0 cleanup juju run-action --wait ovn-dedicated-chassis/0 resume
Post migration tasks
Remove the now redundant Neutron ML2+OVS agents from hypervisors and any dedicated gateways as well as the neutron-gateway and neutron-openvswitch applications from the Juju model:
juju run --application neutron-gateway '\ apt remove -y neutron-dhcp-agent neutron-l3-agent \ neutron-metadata-agent neutron-openvswitch-agent' juju remove-application neutron-gateway juju run --application neutron-openvswitch '\ apt remove -y neutron-dhcp-agent neutron-l3-agent \ neutron-metadata-agent neutron-openvswitch-agent' juju remove-application neutron-openvswitch
Remove the now redundant Neutron ML2+OVS agents from the Neutron database:
openstack network agent list openstack network agent delete ...