Merge "Port binding event extended information for Nova"
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=============================================
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Port binding records, capabilities and events
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=============================================
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https://bugs.launchpad.net/neutron/+bug/1821058
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There are several cases in the Nova/Neutron/os-vif interaction where the
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knowledge of the neutron core plugin or ML2 driver would be useful to
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facilitate a more robust handling of guest networking. For example,
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[3]_.
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This spec aims to enhance the port binding API via the introduction of a new
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extension to provide the additional information required to enable Nova and
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os-vif to make more intelligent use of port binding info.
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Please remember os-vif was only intended to remove the VIF plugging process
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from Nova. The hypervisor configuration (e.g.: libvirt XML generation) is still
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Nova's responsibility. Although os-vif removes the networking back-end logic
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related to the plug and unplug process, Nova still needs to handle the
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information proposed in this spec.
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Problem Description
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===================
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This spec aims to resolve 3 related problems.
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Network connectivity
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--------------------
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[3]_ blueprint seeks to enable the use of instances with ip_allocation=none.
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The port parameter "ip_allocation" was introduced in the [1]_, to "distinguish
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the unaddressed port case from the deferred IP allocation case where routed
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networks is involved" (extracted from [2]_).
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To do this safely and guarantee the guest will have network connectivity, Nova
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must ensure that the network backend that bound the port provides L2
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connectivity.
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For example, in a mixed Calico/SR-IOV deployment, it is valid to use
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ip_allocation=none for any port that is bound by the SR-IOV ML2 driver, but not
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for the Calico backend. In this case, the only connectivity Calico provides to
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a guest is L3, therefore is not possible to spawn a VM without an IP address.
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Network isolation
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-----------------
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In resolving [4]_, a new config option was required in os-vif to allow
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enabling VIF isolation for the ML2/ovs backend. As Nova cannot differentiate
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between VIF_TYPE=”ovs” that is bound by ML2/odl or ML2/ovs it cannot
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automatically instruct os-vif to enable or disable VIF isolation for ML2/ovs
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hosts. If the ML2 driver(s) that bound the port are recorded in the port
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binding details, Nova and os-vif can use that information to more
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intelligently enable backend specific code paths without requiring additional
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network backend specific config options.
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Bandwidth scheduling
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--------------------
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The network driver information can be used too for the bandwidth scheduling
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featured implemented in Stein, as pointed out in this [6]_. Currently Nova
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cannot handle the case where the PF is used by one ML2 driver while the VF is
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managed by the SR-IOV ML2 driver.
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Proposed Change
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===============
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To address the 3 problems stated above, the following additions to the
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``binding:vif_details`` dictionary in the port object are proposed:
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* A new ``connectivity`` field will be introduced with allowed values of "l2",
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"l3" and "legacy". The "legacy" ``connectivity`` value will be the default
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and is a sentinel to indicate the driver does not support this extension yet
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and no connectivity info is available. "l2" drivers provide layer 2
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connectivity, like for example Linux Bridge, Open vSwitch or SR-IOV. "l3"
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drivers provide only layer 3 connectivity, like for example Calico [8]_.
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* A new ``bound_drivers`` field will be added that is a dictionary mapping
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binding_level to driver name. The driver name will be the stevedore entry
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point name for the driver which is already used in config files and intended
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to be stable. A POC is available in [7]_.
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To enable declaration of the ``connectivity``, a new property will be added to
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the ML2 driver base class which will default to "legacy". ML2 drivers that
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inherit from this will override the property.
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The ``bound_drivers`` field will be used by the OVS os-vif plugin to remove the
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need for [5]_. We can enable this option only when
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needed.
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Examples
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--------
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ML2/ovs:
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.. code-block:: python
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binding_details: {
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...
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"connectivity": "l2",
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"bound_drivers": {"0": "openvswtich"}
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}
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ML2/odl v1:
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.. code-block:: python
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binding_details: {
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...
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"connectivity": "legacy",
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"bound_drivers": {"0": "opendaylight"}
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}
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ML2/odl v2:
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.. code-block:: python
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binding_details: {
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...
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"connectivity": "l2",
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"bound_drivers": {"0": "opendaylight_v2"}
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}
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ML2/calico
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.. code-block:: python
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binding_details: {
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...
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"connectivity": "l3",
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"bound_drivers": {"0": "calico"}
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}
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References
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==========
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.. [1] `BP Allow vm to boot without l3 address`:
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https://blueprints.launchpad.net/neutron/+spec/vm-without-l3-address
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.. [2] `commit 361455`:
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https://review.openstack.org/#/c/361455/
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.. [3] `Boot a VM with an unaddressed port`:
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https://blueprints.launchpad.net/nova/+spec/boot-vm-with-unaddressed-port
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.. [4] `bug 1734320`:
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https://bugs.launchpad.net/neutron/+bug/1734320
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.. [5] `isolate_vif config option`:
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https://github.com/openstack/os-vif/blob/stable/stein/vif_plug_ovs/ovs.py#L146-L159
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.. [6] `review 1`:
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https://review.opendev.org/#/c/623543/40/nova/compute/manager.py@2161
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.. [7] `review 2`:
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https://review.openstack.org/#/c/635083
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.. [8] `Calico project`:
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https://docs.openstack.org/networking-calico/latest/
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