Comment 93 for bug 1815989

Reviewed: https://review.opendev.org/c/openstack/nova/+/790447
Committed: https://opendev.org/openstack/nova/commit/23a4b27dc0c156ad6cbe5260d518da3fd62294b8
Submitter: "Zuul (22348)"
Branch: stable/wallaby

commit 23a4b27dc0c156ad6cbe5260d518da3fd62294b8
Author: Stephen Finucane <email address hidden>
Date: Fri Apr 30 12:51:35 2021 +0100

    libvirt: Delegate OVS plug to os-vif

    os-vif 1.15.0 added the ability to create an OVS port during plugging
    by specifying the 'create_port' attribute in the 'port_profile' field.
    By delegating port creation to os-vif, we can rely on it's 'isolate_vif'
    config option [1] that will temporarily configure the VLAN to 4095
    (0xfff), which is reserved for implementation use [2] and is used by
    neutron to as a dead VLAN [3]. By doing this, we ensure VIFs are plugged
    securely, preventing guests from accessing other tenants' networks
    before the neutron OVS agent can wire up the port.

    This change requires a little dance as part of the live migration flow.
    Since we can't be certain the destination host has a version of os-vif
    that supports this feature, we need to use a sentinel to indicate when
    it does. Typically we would do so with a field in
    'LibvirtLiveMigrateData', such as the 'src_supports_numa_live_migration'
    and 'dst_supports_numa_live_migration' fields used to indicate support
    for NUMA-aware live migration. However, doing this prevents us
    backporting this important fix since o.vo changes are not backportable.
    Instead, we (somewhat evilly) rely on the free-form nature of the
    'VIFMigrateData.profile_json' string field, which stores JSON blobs and
    is included in 'LibvirtLiveMigrateData' via the 'vifs' attribute, to
    transport this sentinel. This is a hack but is necessary to work around
    the lack of a free-form "capabilities" style dict that would allow us do
    backportable fixes to live migration features.

    Note that this change has the knock on effect of modifying the XML
    generated for OVS ports: when hybrid plug is false will now be of type
    'ethernet' rather than 'bridge' as before. This explains the larger than
    expected test damage but should not affect users.

    Changes:
      lower-constraints.txt
      requirements.txt
      nova/network/os_vif_util.py
      nova/tests/unit/virt/libvirt/test_vif.py
      nova/tests/unit/virt/libvirt/test_driver.py
      nova/virt/libvirt/driver.py

    NOTE(stephenfin): Change I362deb1088c88cdcd8219922da9dc9a01b10a940
    ("objects: Fix VIFMigrateData.supports_os_vif_delegation setter") which
    contains an important fix for the original change, is squashed into this
    change. In addition, the os-vif version bump we introduced in the
    original version of this patch is not backportable and as a result, we
    must introduce two additional checks. Both checks ensure we have a
    suitable version of os-vif and skip the new code paths if not. The first
    check is in the libvirt driver's 'check_can_live_migrate_destination'
    function, which as the name suggests runs on the destination host early
    in the live migration process. If os-vif is not new enough on the
    destination, we will report that we cannot support os-vif delegation.
    The other check is in the '_nova_to_osvif_vif_ovs' helper in
    'nova.network.os_vif_util'. This simply ensures we don't try to set an
    invalid attribute on the os-vif object if the version isn't new enough.
    Two tests are modified to accommodate these checks with similar version
    check logic. The lower-constraints job can be relied on to validate
    behavior on the older version of os-vif.

    [1] https://opendev.org/openstack/os-vif/src/tag/2.4.0/vif_plug_ovs/ovs.py#L90-L93
    [2] https://en.wikipedia.org/wiki/IEEE_802.1Q#Frame_format
    [3] https://answers.launchpad.net/neutron/+question/231806

    NOTE(auniyal):
      * libvirt: Always delegate OVS plug to os-vif is squashed
    https://github.com/openstack/nova/commit/fa0fb2fe3d61de1cb871c48ee97053cf2fb5827a
      * Updated fakelibvirt.Domain.XMLDesc to add pci address
    for ovs interface, which is a patial backport of
    https://github.com/openstack/nova/commit/1ad287bf9a8f65ce68c14f4634775f58abda15c2

    Change-Id: I11fb5d3ada7f27b39c183157ea73c8b72b4e672e
    Depends-On: Id12486b3127ab4ac8ad9ef2b3641da1b79a25a50
    Closes-Bug: #1734320
    Closes-Bug: #1815989
    (cherry picked from commit a62dd42c0dbb6b2ab128e558e127d76962738446)