From c3d69f52e579da322ef1fe7a26a463fda3b7323f Mon Sep 17 00:00:00 2001
From: Yuta HIGUCHI <y-higuchi@ak.jp.nec.com>
Date: Mon, 8 Aug 2016 11:52:52 -0700
Subject: [PATCH] Fix NPE when there's no secondary path.

Change-Id: I3bb8eeb2abf140d44cf4dc7186cf1bf316c23f70
---
 .../api/src/main/java/org/onosproject/net/DisjointPath.java | 2 +-
 .../main/java/org/onosproject/common/DefaultTopology.java   | 6 ++++++
 .../src/main/java/org/onlab/graph/DisjointPathPair.java     | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/core/api/src/main/java/org/onosproject/net/DisjointPath.java b/core/api/src/main/java/org/onosproject/net/DisjointPath.java
index 39059f4f2c..39237eae5a 100644
--- a/core/api/src/main/java/org/onosproject/net/DisjointPath.java
+++ b/core/api/src/main/java/org/onosproject/net/DisjointPath.java
@@ -43,7 +43,7 @@ public interface DisjointPath extends Path {
     /**
      * Gets secondary path.
      *
-     * @return secondary path
+     * @return secondary path, or null if there is no secondary path available.
      */
     Path backup();
 }
diff --git a/core/common/src/main/java/org/onosproject/common/DefaultTopology.java b/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
index 8c4fbc84ec..72780d39cf 100644
--- a/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
+++ b/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
@@ -482,6 +482,12 @@ public class DefaultTopology extends AbstractModel implements Topology {
     }
 
     private DisjointPath networkDisjointPath(DisjointPathPair<TopologyVertex, TopologyEdge> path) {
+        if (!path.hasBackup()) {
+            // There was no secondary path available.
+            return new DefaultDisjointPath(CORE_PROVIDER_ID,
+                                           (DefaultPath) networkPath(path.primary()),
+                                           null);
+        }
         return new DefaultDisjointPath(CORE_PROVIDER_ID,
                                        (DefaultPath) networkPath(path.primary()),
                                        (DefaultPath) networkPath(path.secondary()));
diff --git a/utils/misc/src/main/java/org/onlab/graph/DisjointPathPair.java b/utils/misc/src/main/java/org/onlab/graph/DisjointPathPair.java
index 0e25116fe1..1e8d3d6140 100644
--- a/utils/misc/src/main/java/org/onlab/graph/DisjointPathPair.java
+++ b/utils/misc/src/main/java/org/onlab/graph/DisjointPathPair.java
@@ -66,7 +66,7 @@ public class DisjointPathPair<V extends Vertex, E extends Edge<V>> implements Pa
     /**
      * Returns the secondary path.
      *
-     * @return primary path
+     * @return secondary path, or null if there is no secondary path available.
      */
     public Path<V, E> secondary() {
         return secondary;