From 9799353ee81405564854458abe4da5e306162eed Mon Sep 17 00:00:00 2001
From: Suresh Srinivas <suresh@apache.org>
Date: Wed, 28 Sep 2011 17:47:20 +0000
Subject: [PATCH] HADOOP-7668. Add a NetUtils method that can tell if an
 InetAddress belongs to local host. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1176986 13f79535-47bb-0310-9956-ffa450edef68
---
 .../hadoop-common/CHANGES.txt                 |  3 ++
 .../java/org/apache/hadoop/net/NetUtils.java  | 23 +++++++++++++
 .../org/apache/hadoop/net/TestNetUtils.java   | 32 +++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 336737f0c2..3960abe922 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -19,6 +19,9 @@ Trunk (unreleased changes)
 
     HADOOP-7635. RetryInvocationHandler should release underlying resources on
                  close (atm)
+    
+    HADOOP-7668. Add a NetUtils method that can tell if an InetAddress 
+    belongs to local host. (suresh)
 
   BUGS
 
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java
index b22aaa009c..9b744ed3ee 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java
@@ -516,4 +516,27 @@ public static InetAddress getLocalInetAddress(String host)
     } catch (UnknownHostException ignore) { }
     return addr;
   }
+  
+  /**
+   * Given an InetAddress, checks to see if the address is a local address, by
+   * comparing the address with all the interfaces on the node.
+   * @param addr address to check if it is local node's address
+   * @return true if the address corresponds to the local node
+   */
+  public static boolean isLocalAddress(InetAddress addr) {
+    // Check if the address is any local or loop back
+    boolean local = addr.isAnyLocalAddress() || addr.isLoopbackAddress();
+    System.out.println("address is any or loopback address " + addr);
+
+    // Check if the address is defined on any interface
+    if (!local) {
+      try {
+        local = NetworkInterface.getByInetAddress(addr) != null;
+      } catch (SocketException e) {
+        local = false;
+      }
+    }
+        System.out.println("address " + addr + " is local " + local);
+    return local;
+  }
 }
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestNetUtils.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestNetUtils.java
index f49d4c886e..7cc6f4d521 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestNetUtils.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestNetUtils.java
@@ -18,13 +18,17 @@
 package org.apache.hadoop.net;
 
 import org.junit.Test;
+
 import static org.junit.Assert.*;
 
+import java.net.InetAddress;
+import java.net.NetworkInterface;
 import java.net.Socket;
 import java.net.ConnectException;
 import java.net.SocketException;
 import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
+import java.util.Enumeration;
 
 import org.apache.hadoop.conf.Configuration;
 
@@ -88,4 +92,32 @@ public void testVerifyHostnamesNoException() {
       fail("NetUtils.verifyHostnames threw unexpected UnknownHostException");
     }
   }
+  
+  /** 
+   * Test for {@link NetUtils#isLocalAddress(java.net.InetAddress)}
+   */
+  @Test
+  public void testIsLocalAddress() throws Exception {
+    // Test - local host is local address
+    assertTrue(NetUtils.isLocalAddress(InetAddress.getLocalHost()));
+    
+    // Test - all addresses bound network interface is local address
+    Enumeration<NetworkInterface> interfaces = NetworkInterface
+        .getNetworkInterfaces();
+    if (interfaces != null) { // Iterate through all network interfaces
+      while (interfaces.hasMoreElements()) {
+        NetworkInterface i = interfaces.nextElement();
+        Enumeration<InetAddress> addrs = i.getInetAddresses();
+        if (addrs == null) {
+          continue;
+        }
+        // Iterate through all the addresses of a network interface
+        while (addrs.hasMoreElements()) {
+          InetAddress addr = addrs.nextElement();
+          assertTrue(NetUtils.isLocalAddress(addr));
+        }
+      }
+    }
+    assertFalse(NetUtils.isLocalAddress(InetAddress.getByName("8.8.8.8")));
+  }
 }