The Shared File Systems service architecture defines an abstraction
layer for network resource provisioning and allowing administrators to
choose from a different options for how network resources are assigned
to their projects’ networked storage. There are a set of network
plug-ins that provide a variety of integration approaches with the
network services that are available with OpenStack.

What is a network plugin in
Manila?

A network plugin is a python class that uses a specific facility
(e.g. Neutron network) to provide network resources to the manila-share service.

When to use a network plugin?

A Manila share driver may be
configured in one of two modes, where it is managing the lifecycle of
share servers on its own or where it is
merely providing storage resources on a pre-configured share server.
This mode is defined using the boolean option driver_handles_share_servers in the Manila
configuration file. A network plugin is only useful when a driver is
handling its own share servers.

When driver_handles_share_servers is
set to True, a share driver will be
called to create share servers for shares using information provided
within a share network. This information
will be provided to one of the enabled network plugins that will handle
reservation, creation and deletion of network resources including IP addresses and network interfaces.

The Shared File Systems service may need a network resource
provisioning if share service with specified driver works in mode, when
a share driver manages lifecycle of share servers on its own. This
behavior is defined by a flag driver_handles_share_servers
in share service configuration. When
driver_handles_share_servers is set to True, a
share driver will be called to create share servers for shares using
information provided within a share network. This information will be
provided to one of the enabled network plug-ins that will handle
reservation, creation and deletion of network resources including IP
addresses and network interfaces.

What network plug-ins are
available?

There are three network plug-ins and three python classes in the
Shared File Systems service:

1. Network plug-in for using the OpenStack Networking service. It
   allows to use any network segmentation that the Networking service
   supports. It is up to each share driver to support at least one network
   segmentation type.

   1. manila.network.neutron.neutron_network_plugin.NeutronNetworkPlugin.
      This is a default network plug-in. It requires the
      neutron_net_id and the neutron_subnet_id to be
      provided when defining the share network that will be used for the
      creation of share servers. The user may define any number of share
      networks corresponding to the various physical network segments in a
      project environment.
   2. manila.network.neutron.neutron_network_plugin.NeutronSingleNetworkPlugin.
      This is a simplification of the previous case. It accepts values for
      neutron_net_id and neutron_subnet_id from the
      manila.conf configuration file and uses one network for all
      shares.
   3. manila.network.neutron.neutron_network_plugin.NeutronBindNetworkPlugin.
      This driver waits for active binding and fails if a Neutron port can’t
      be bound or an error occurs. This plugin is useful for agent based
      binding (like OVS with docker driver) and fabric binding where real
      hardware reconfiguration is taking place. The existing
      NeutronBindSingleNetworkPlugin is a combination of 1b and 1c.

   When only a single network is needed, the NeutronSingleNetworkPlugin
   (1.b) is a simple solution. Otherwise NeutronNetworkPlugin (1.a) should
   be chosen.

2. Network plug-in for specifying networks independently from
   OpenStack networking services.

   1. manila.network.standalone_network_plugin.StandaloneNetworkPlugin.
      This plug-in uses a pre-existing network that is available to the
      manila-share host. This network may be handled either by OpenStack or be
      created independently by any other means. The plug-in supports any type
      of network – flat and segmented. As above, it is completely up to the
      share driver to support the network type for which the network plug-in
      is configured.