Added class InterfaceIpAddress and the corresponding unit test.

That class can be used to represent the IP address information
on an interface.

+package org.onlab.onos.net.host;
+
+import java.util.Objects;
+import org.onlab.packet.IpAddress;
+import org.onlab.packet.IpPrefix;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Represents a single IP address information on an interface.
+ *
+ * TODO:
+ *  - Add computation for the default broadcast address if it is not
+ *    specified
+ *  - Add explicit checks that each IP address or prefix belong to the
+ *    same IP version: IPv4/IPv6.
+ *  - Inside the copy constructor we should use copy constructors for each
+ *    field
+ */
+public class InterfaceIpAddress {
+    private final IpAddress ipAddress;
+    private final IpPrefix subnetAddress;
+    private final IpAddress broadcastAddress;
+    private final IpAddress peerAddress;
+
+    /**
+     * Copy constructor.
+     *
+     * @param other the object to copy from
+     */
+    public InterfaceIpAddress(InterfaceIpAddress other) {
+        // TODO: we should use copy constructors for each field
+        this.ipAddress = other.ipAddress;
+        this.subnetAddress = other.subnetAddress;
+        this.broadcastAddress = other.broadcastAddress;
+        this.peerAddress = other.peerAddress;
+    }
+
+    /**
+     * Constructor for a given IP address and a subnet address.
+     *
+     * @param ipAddress the IP address
+     * @param subnetAddress the IP subnet address
+     */
+    public InterfaceIpAddress(IpAddress ipAddress, IpPrefix subnetAddress) {
+        this.ipAddress = checkNotNull(ipAddress);
+        this.subnetAddress = checkNotNull(subnetAddress);
+        // TODO: Recompute the default broadcast address from the subnet
+        // address
+        this.broadcastAddress = null;
+        this.peerAddress = null;
+    }
+
+    /**
+     * Constructor for a given IP address and a subnet address.
+     *
+     * @param ipAddress the IP address
+     * @param subnetAddress the IP subnet address
+     * @param broadcastAddress the IP broadcast address. It can be used
+     * to specify non-default broadcast address
+     */
+    public InterfaceIpAddress(IpAddress ipAddress, IpPrefix subnetAddress,
+                              IpAddress broadcastAddress) {
+        this.ipAddress = checkNotNull(ipAddress);
+        this.subnetAddress = checkNotNull(subnetAddress);
+        this.broadcastAddress = broadcastAddress;
+        this.peerAddress = null;
+    }
+
+    /**
+     * Constructor for a given IP address and a subnet address.
+     *
+     * @param ipAddress the IP address
+     * @param subnetAddress the IP subnet address
+     * @param broadcastAddress the IP broadcast address. It can be used
+     * to specify non-default broadcast address. It should be null for
+     * point-to-point interfaces with a peer address
+     * @param peerAddress the peer IP address for point-to-point interfaces
+     */
+    public InterfaceIpAddress(IpAddress ipAddress, IpPrefix subnetAddress,
+                              IpAddress broadcastAddress,
+                              IpAddress peerAddress) {
+        this.ipAddress = checkNotNull(ipAddress);
+        this.subnetAddress = checkNotNull(subnetAddress);
+        this.broadcastAddress = broadcastAddress;
+        this.peerAddress = peerAddress;
+    }
+
+    /**
+     * Gets the IP address.
+     *
+     * @return the IP address
+     */
+    public IpAddress ipAddress() {
+        return ipAddress;
+    }
+
+    /**
+     * Gets the IP subnet address.
+     *
+     * @return the IP subnet address
+     */
+    public IpPrefix subnetAddress() {
+        return subnetAddress;
+    }
+
+    /**
+     * Gets the subnet IP broadcast address.
+     *
+     * @return the subnet IP broadcast address
+     */
+    public IpAddress broadcastAddress() {
+        return broadcastAddress;
+    }
+
+    /**
+     * Gets the IP point-to-point interface peer address.
+     *
+     * @return the IP point-to-point interface peer address
+     */
+    public IpAddress peerAddress() {
+        return peerAddress;
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+        if (!(other instanceof InterfaceIpAddress)) {
+            return false;
+        }
+        InterfaceIpAddress otherAddr = (InterfaceIpAddress) other;
+
+        return Objects.equals(this.ipAddress, otherAddr.ipAddress)
+            && Objects.equals(this.subnetAddress, otherAddr.subnetAddress)
+            && Objects.equals(this.broadcastAddress,
+                              otherAddr.broadcastAddress)
+            && Objects.equals(this.peerAddress, otherAddr.peerAddress);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(ipAddress, subnetAddress, broadcastAddress,
+                            peerAddress);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("ipAddress", ipAddress)
+            .add("subnetAddress", subnetAddress)
+            .add("broadcastAddress", broadcastAddress)
+            .add("peerAddress", peerAddress)
+            .omitNullValues().toString();
+    }
+}