Add Virtual Bridge Domain implementation

Change-Id: I427b709ac0af1ade365bc60148ddf778f7be458a
Signed-off-by: Robert Varga <nite@hq.sk>

5 files changed, 562 insertions, 0 deletions

diff --git a/vbd/impl/pom.xml b/vbd/impl/pom.xml
new file mode 100644
index 000000000..3d6d55aea
--- /dev/null
+++ b/vbd/impl/pom.xml
@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- vi: set et smarttab sw=4 tabstop=4: -->
+<!--
+ Copyright (c) 2015 Cisco and/or its affiliates.
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at:
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+  <parent>
+    <groupId>io.fd.honeycomb.common</groupId>
+    <artifactId>impl-parent</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <relativePath>../../common/impl-parent</relativePath>
+  </parent>
+
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>io.fd.honeycomb.vbd</groupId>
+  <artifactId>vbd-impl</artifactId>
+  <version>1.0.0-SNAPSHOT</version>
+  <packaging>bundle</packaging>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>io.fd.honeycomb.vbd</groupId>
+        <artifactId>vbd-artifacts</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>vbd-api</artifactId>
+    </dependency>
+
+    <!-- Testing Dependencies -->
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-all</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>
diff --git a/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/BridgeDomain.java b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/BridgeDomain.java
new file mode 100644
index 000000000..aff03b2a6
--- /dev/null
+++ b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/BridgeDomain.java
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package io.fd.honeycomb.vbd.impl;
+
+import com.google.common.base.Preconditions;
+import java.util.Collection;
+import javax.annotation.concurrent.GuardedBy;
+import org.opendaylight.controller.md.sal.binding.api.BindingTransactionChain;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.controller.md.sal.binding.api.DataObjectModification;
+import org.opendaylight.controller.md.sal.binding.api.DataObjectModification.ModificationType;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeChangeListener;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeIdentifier;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeModification;
+import org.opendaylight.controller.md.sal.binding.api.WriteTransaction;
+import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.vbridge.topology.rev160129.Topology1;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.Topology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.TopologyKey;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.topology.Node;
+import org.opendaylight.yangtools.concepts.ListenerRegistration;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.KeyedInstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implementation of a single Virtual Bridge Domain. It is bound to a particular network topology instance, manages
+ * bridge members and projects state into the operational data store.
+ */
+final class BridgeDomain implements DataTreeChangeListener<Topology> {
+    private static final Logger LOG = LoggerFactory.getLogger(BridgeDomain.class);
+    private final KeyedInstanceIdentifier<Topology, TopologyKey> topology;
+
+    @GuardedBy("this")
+    private final BindingTransactionChain chain;
+    private final ListenerRegistration<?> reg;
+    private Topology1 config;
+
+    private BridgeDomain(final DataBroker dataBroker, final KeyedInstanceIdentifier<Topology, TopologyKey> topology,
+            final BindingTransactionChain chain) {
+        this.topology = Preconditions.checkNotNull(topology);
+        this.chain = Preconditions.checkNotNull(chain);
+
+        reg = dataBroker.registerDataTreeChangeListener(
+            new DataTreeIdentifier<>(LogicalDatastoreType.CONFIGURATION, topology), this);
+    }
+
+    static BridgeDomain create(final DataBroker dataBroker,
+            final KeyedInstanceIdentifier<Topology, TopologyKey> topology, final BindingTransactionChain chain) {
+
+        LOG.debug("Wiping operational state of {}", topology);
+
+        final WriteTransaction tx = chain.newWriteOnlyTransaction();
+        tx.delete(LogicalDatastoreType.OPERATIONAL, topology);
+        tx.submit();
+
+        return new BridgeDomain(dataBroker, topology, chain);
+    }
+
+    synchronized void forceStop() {
+        LOG.info("Bridge domain {} for {} going down", this, topology);
+        reg.close();
+        chain.close();
+        LOG.info("Bridge domain {} for {} is down", this, topology);
+    }
+
+    synchronized void stop() {
+        LOG.debug("Bridge domain {} for {} shutting down", this, topology);
+
+        final WriteTransaction tx = chain.newWriteOnlyTransaction();
+        tx.delete(LogicalDatastoreType.OPERATIONAL, topology);
+        tx.submit();
+        chain.close();
+    }
+
+    @Override
+    public synchronized void onDataTreeChanged(final Collection<DataTreeModification<Topology>> changes) {
+        for (DataTreeModification<Topology> c : changes) {
+            LOG.debug("Domain {} for {} processing change {}", this, topology, c);
+
+            final DataObjectModification<Topology> mod = c.getRootNode();
+            switch (mod.getModificationType()) {
+                case DELETE:
+                    LOG.debug("Topology {} deleted, expecting shutdown", topology);
+                    break;
+                case SUBTREE_MODIFIED:
+                    // First check if the configuration has changed
+                    final DataObjectModification<Topology1> newConfig = mod.getModifiedAugmentation(Topology1.class);
+                    if (newConfig != null) {
+                        if (newConfig.getModificationType() != ModificationType.DELETE) {
+                            LOG.debug("Topology {} modified configuration {}", topology, newConfig);
+                            updateConfiguration(newConfig);
+                        } else {
+                            // FIXME: okay, what can we do about this one?
+                            LOG.error("Topology {} configuration deleted, good luck!", topology);
+                        }
+                    }
+
+                    for (DataObjectModification<? extends DataObject> child : mod.getModifiedChildren()) {
+                        LOG.debug("Topology {} modified child {}", topology, child);
+
+                        if (Node.class.isAssignableFrom(child.getDataType())) {
+                            modifyNode((DataObjectModification<Node>) child);
+                        }
+                    }
+
+                    break;
+                case WRITE:
+                    final Topology data = mod.getDataAfter();
+
+                    // Read configuration
+                    final Topology1 config = data.getAugmentation(Topology1.class);
+                    if (config != null) {
+                        setConfiguration(config);
+                    } else {
+                        LOG.error("Topology {} has no configuration, good luck!", topology);
+                    }
+
+                    // FIXME: deal with nodes
+
+                    break;
+                default:
+                    LOG.warn("Unhandled topology modification {}", mod);
+                    break;
+            }
+        }
+    }
+
+    private void modifyNode(final DataObjectModification<Node> child) {
+        switch (child.getModificationType()) {
+            case DELETE:
+                LOG.debug("Topology {} node {} deleted", topology, child.getIdentifier());
+                // FIXME: do something
+                break;
+            case SUBTREE_MODIFIED:
+                LOG.debug("Topology {} node {} modified", topology, child.getIdentifier());
+                // FIXME: do something
+                break;
+            case WRITE:
+                LOG.debug("Topology {} node {} created", topology, child.getIdentifier());
+                // FIXME: do something
+                break;
+            default:
+                LOG.warn("Unhandled node modification {} in topology {}", child, topology);
+                break;
+        }
+    }
+
+    private void setConfiguration(final Topology1 config) {
+        LOG.debug("Topology {} configuration set to {}", topology, config);
+
+        this.config = config;
+    }
+
+    @GuardedBy("this")
+    private void updateConfiguration(final DataObjectModification<Topology1> mod) {
+        LOG.debug("Topology {} configuration changed", topology);
+
+        // FIXME: do something smarter
+        setConfiguration(mod.getDataAfter());
+    }
+}
diff --git a/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/TopologyMonitor.java b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/TopologyMonitor.java
new file mode 100644
index 000000000..b2e52c37e
--- /dev/null
+++ b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/TopologyMonitor.java
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package io.fd.honeycomb.vbd.impl;
+
+import com.google.common.base.Preconditions;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import javax.annotation.concurrent.GuardedBy;
+import org.opendaylight.controller.md.sal.binding.api.BindingTransactionChain;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.controller.md.sal.binding.api.DataObjectModification;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeChangeListener;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeModification;
+import org.opendaylight.controller.md.sal.common.api.data.AsyncTransaction;
+import org.opendaylight.controller.md.sal.common.api.data.TransactionChain;
+import org.opendaylight.controller.md.sal.common.api.data.TransactionChainListener;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.vbridge.topology.rev160129.network.topology.topology.topology.types.VbridgeTopology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.Topology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.TopologyKey;
+import org.opendaylight.yangtools.yang.binding.KeyedInstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Class responsible for monitoring /network-topology/topology and activating a {@link BridgeDomain} when a particular
+ * topology is marked as a bridge domain.
+ */
+final class TopologyMonitor implements DataTreeChangeListener<VbridgeTopology>, AutoCloseable {
+    private static final Logger LOG = LoggerFactory.getLogger(TopologyMonitor.class);
+
+    @GuardedBy("this")
+    private final Map<TopologyKey, BridgeDomain> domains = new HashMap<>();
+    private final DataBroker dataBroker;
+
+    TopologyMonitor(final DataBroker dataBroker) {
+        this.dataBroker = Preconditions.checkNotNull(dataBroker);
+    }
+
+    @Override
+    public synchronized void onDataTreeChanged(final Collection<DataTreeModification<VbridgeTopology>> changes) {
+        for (DataTreeModification<VbridgeTopology> c : changes) {
+            @SuppressWarnings("unchecked")
+            final KeyedInstanceIdentifier<Topology, TopologyKey> topology =
+                    (KeyedInstanceIdentifier<Topology, TopologyKey>) c.getRootPath().getRootIdentifier()
+                    .firstIdentifierOf(Topology.class);
+
+            Preconditions.checkArgument(!topology.isWildcarded(), "Wildcard topology %s is not supported", topology);
+
+            final DataObjectModification<VbridgeTopology> mod = c.getRootNode();
+            switch (mod.getModificationType()) {
+                case DELETE:
+                    LOG.debug("Topology {} removed", topology);
+                    stopDomain(topology);
+                    break;
+                case WRITE:
+                    LOG.debug("Topology {} added", topology);
+                    startDomain(topology);
+                    break;
+                default:
+                    LOG.warn("Ignoring unhandled modification type {}", mod.getModificationType());
+                    break;
+            }
+        }
+    }
+
+    private synchronized void completeDomain(final KeyedInstanceIdentifier<Topology, TopologyKey> topology) {
+        LOG.debug("Bridge domain for {} completed operation", topology);
+        domains.remove(topology);
+
+        synchronized (domains) {
+            domains.notify();
+        }
+    }
+
+    private synchronized void restartDomain(final KeyedInstanceIdentifier<Topology, TopologyKey> topology) {
+        final BridgeDomain prev = domains.remove(topology);
+        if (prev == null) {
+            LOG.warn("No domain for {}, not restarting", topology);
+            return;
+        }
+
+        prev.forceStop();
+        startDomain(topology);
+    }
+
+    @GuardedBy("this")
+    private void startDomain(final KeyedInstanceIdentifier<Topology, TopologyKey> topology) {
+        final BridgeDomain prev = domains.get(topology.getKey());
+        if (prev != null) {
+            LOG.warn("Bridge domain {} for {} already started", prev, topology);
+            return;
+        }
+
+        LOG.debug("Starting bridge domain for {}", topology);
+
+        final BindingTransactionChain chain = dataBroker.createTransactionChain(new TransactionChainListener() {
+            @Override
+            public void onTransactionChainSuccessful(final TransactionChain<?, ?> chain) {
+                completeDomain(topology);
+            }
+
+            @Override
+            public void onTransactionChainFailed(final TransactionChain<?, ?> chain,
+                    final AsyncTransaction<?, ?> transaction, final Throwable cause) {
+                LOG.warn("Bridge domain for {} failed, restarting it", cause);
+                restartDomain(topology);
+            }
+        });
+
+        final BridgeDomain domain = BridgeDomain.create(dataBroker, topology, chain);
+        domains.put(topology.getKey(), domain);
+
+        LOG.debug("Bridge domain {} for {} started", domain, topology);
+    }
+
+    @GuardedBy("this")
+    private void stopDomain(final KeyedInstanceIdentifier<Topology, TopologyKey> topology) {
+        final BridgeDomain domain = domains.remove(topology.getKey());
+        if (domain == null) {
+            LOG.warn("Bridge domain for {} not present", topology);
+            return;
+        }
+
+        domain.stop();
+    }
+
+    @Override
+    public synchronized void close() {
+        LOG.debug("Topology monitor {} shut down started", this);
+
+        for (Entry<TopologyKey, BridgeDomain> e : domains.entrySet()) {
+            LOG.debug("Shutting down bridge domain {} (key {})", e.getValue(), e.getKey());
+            e.getValue().stop();
+        }
+
+        while (!domains.isEmpty()) {
+            LOG.debug("Waiting for domains for {} to complete", domains.keySet());
+            synchronized (domains) {
+                try {
+                    domains.wait();
+                } catch (InterruptedException e) {
+                    LOG.warn("Interrupted while waiting for domain shutdown, {} have not completed yet",
+                        domains.keySet(), e);
+                    break;
+                }
+            }
+        }
+
+        LOG.debug("Topology monitor {} shut down completed", this);
+    }
+}
diff --git a/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/VirtualBridgeDomainManager.java b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/VirtualBridgeDomainManager.java
new file mode 100644
index 000000000..37da73159
--- /dev/null
+++ b/vbd/impl/src/main/java/io/fd/honeycomb/vbd/impl/VirtualBridgeDomainManager.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package io.fd.honeycomb.vbd.impl;
+
+import com.google.common.base.Preconditions;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.controller.md.sal.binding.api.DataTreeIdentifier;
+import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.vbridge.topology.rev160129.TopologyTypes1;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.vbridge.topology.rev160129.network.topology.topology.topology.types.VbridgeTopology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.NetworkTopology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.Topology;
+import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.topology.TopologyTypes;
+import org.opendaylight.yangtools.concepts.ListenerRegistration;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Tip for the Virtual Bridge Domain implementation. This class is instantiated when the application is started
+ * and {@link #close()}d when it is shut down.
+ */
+public final class VirtualBridgeDomainManager implements AutoCloseable {
+    private static final Logger LOG = LoggerFactory.getLogger(VirtualBridgeDomainManager.class);
+    private static final DataTreeIdentifier<VbridgeTopology> LISTEN_TREE =
+            new DataTreeIdentifier<>(LogicalDatastoreType.CONFIGURATION,
+                    InstanceIdentifier.builder(NetworkTopology.class).child(Topology.class).child(TopologyTypes.class)
+                    .augmentation(TopologyTypes1.class).child(VbridgeTopology.class).build());
+
+    private final ListenerRegistration<TopologyMonitor> reg;
+    private boolean closed;
+
+    private VirtualBridgeDomainManager(final ListenerRegistration<TopologyMonitor> reg) {
+        this.reg = Preconditions.checkNotNull(reg);
+    }
+
+    public static VirtualBridgeDomainManager create(@Nonnull final DataBroker dataBroker) {
+        final ListenerRegistration<TopologyMonitor> reg =
+                dataBroker.registerDataTreeChangeListener(LISTEN_TREE, new TopologyMonitor(dataBroker));
+
+        return new VirtualBridgeDomainManager(reg);
+    }
+
+    @Override
+    public void close() {
+        if (!closed) {
+            LOG.debug("Virtual Bridge Domain manager shut down started");
+
+            final TopologyMonitor monitor = reg.getInstance();
+            reg.close();
+            LOG.debug("Topology monitor {} unregistered", monitor);
+            monitor.close();
+
+            closed = true;
+            LOG.debug("Virtual Bridge Domain manager shut down completed");
+        }
+    }
+}
diff --git a/vbd/impl/vbridge-workflow.txt b/vbd/impl/vbridge-workflow.txt
new file mode 100644
index 000000000..86ba544f4
--- /dev/null
+++ b/vbd/impl/vbridge-workflow.txt
@@ -0,0 +1,106 @@
+VPP Inventory/Topology
+----------------------
+
+- VPP management done through netconf-node-topology
+- Mount point management done by sal-netconf-connector
+
+
+Virtual Bridge Domain management
+--------------------------------
+
+Prerequisite: configured netconf-node-topology
+
+1) Create a Virtual Bridge Domain:
+
+	A) The UI creates a network topology instance in Controller Data Store
+	with:
+
+	- topology-types/vbridge-topology container
+	- tunnel-type set to tunnel-type-vxlan
+	- tunnel-parameters/vxlan/vni set to appropriate value
+	- any bridge domain parameters from v3po:bridge-domain-attributes
+
+	B) The Controller App receives a DataTreeChangeNotification about the
+	topology instance being created
+
+2) Assign a VPP into a Virtual Bridge Domain
+	Prerequisite: Virtual Bridge Domain exists
+
+	A) The UI creates a 'node' within the VBD network topology in the
+	Controller Data Store with:
+
+	- bridge-member container
+	- supporting-node pointing to the VPP node in the
+	  netconf-node-topology
+	
+	B) The Controller App receives a DataTreeChangeNotification about the
+	node being added, and:
+
+	- it looks at the supporting-node in the netconf topology and if the
+	  node is connected:
+	  - it creates a bridge domain with the name matching this VBD name,
+	    copying bridge domain parameters from VBD Topology configuration
+	    into the VPP
+	  - once that succeeds it creates the corresponding
+	    supporting-bridge-domain leaf in the Controller's operational
+	    datastore. The leaf contains a RESTCONF-encoded instance
+	    identifier of the bridge domain created in the VPP, relative to
+	    that VPP's mount point.
+	
+3) Assigning a physical VPP interface into a Virtual Bridge Domain
+	Prerequisite: The VPP itself has been added to the Virtual Bridge
+	              Domain
+
+	A) The UI creates a 'termination-point' inside the 'node' added in 2),
+	with:
+
+	- user-interface, containing RESTCONF-encoded instance identifier
+	  of the VPP interface, relative to that VPP's mount point in config
+	  data store.
+
+	B) The Controller App receives a notification of this being done and:
+	- looks if the VPP is connected, if it is, the app will:
+	  - add the interface into the VPP's bridge domain configuration
+
+Inverse operations are achieved by the UI deleting the corresponding nodes in
+the Controller's configuration data store.
+	  
+
+Virtual Bridge Domain tunnel management
+---------------------------------------
+
+Operation is triggered by adding more than one VPP into the virtual bridge
+domain, for sake of clarity this describes only one-way tunnel setup. The
+process is repeated until a full mesh is achieved (FUTURE: spanning tree?).
+The process is also simplified for demo purposes, real-world deployment would
+deal with day-1 configuration and multi-provider setups.
+
+Demo assumption: there is exactly one interface with a VRF and IP address
+assined, which is the interface to be used for tunnels
+
+The Controller App looks at the Source VPP:
+- it finds the only interface with VRF and IP addresses. It will use this VRF
+  as the vxlan tunnel VRF. It will use the IP address as the vxlan tunnel
+  source.
+
+The Controller App looks at the Destination VPP:
+- it finds the only interface with VRF and IP addresses. It will use the IP
+  address as the vxlan tunnel destination.
+
+The Controller App sets up the tunnel on the source VPP, using the VNI
+configured for this Virtual Bridge Domain and IP addresses as detailed above.
+
+The controller app creates a new termination point within the VBD's the
+controller's  operational data store, under the
+node representing the source VPP, with a generated ID (mechanism is TBD, must
+not conflict with VPP names) and 'tunnel-interface' leaf, which points to the
+vxlan interface created on the source VPP (e.g. VPP config state).
+
+This process is repeated in the reverse direction.
+
+Once that is done, the controller app will create a link from the newly-created
+source TP to the newly-created destination TP in the controller's operational
+data store, with leaf 'tunnel' pointing to the source VPP's interface operation
+state (e.g. VPP vxlan oper state). A reverse link will be created, with the
+'tunnel' leaf pointing to the destination VPP's interface state.
+