HDFS-7431. log message for InvalidMagicNumberException may be incorrect. Contributed by Yi Liu.

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -618,6 +618,9 @@ Release 2.7.0 - UNRELEASED
     HDFS-7494. Checking of closed in DFSInputStream#pread() should be protected
     by synchronization (Ted Yu via Colin P. McCabe)
 
+    HDFS-7431. log message for InvalidMagicNumberException may be incorrect.
+    (Yi Liu via cnauroth)
+
 Release 2.6.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/sasl/InvalidMagicNumberException.java

@@ -31,14 +31,26 @@ import org.apache.hadoop.classification.InterfaceAudience;
 public class InvalidMagicNumberException extends IOException {
 
   private static final long serialVersionUID = 1L;
+  private final boolean handshake4Encryption;
 
   /**
    * Creates a new InvalidMagicNumberException.
    *
    * @param magicNumber expected value
    */
-  public InvalidMagicNumberException(int magicNumber) {
+  public InvalidMagicNumberException(final int magicNumber, 
+      final boolean handshake4Encryption) {
     super(String.format("Received %x instead of %x from client.",
         magicNumber, SASL_TRANSFER_MAGIC_NUMBER));
+    this.handshake4Encryption = handshake4Encryption;
+  }
+  
+  /**
+   * Return true if it's handshake for encryption
+   * 
+   * @return boolean true if it's handshake for encryption
+   */
+  public boolean isHandshake4Encryption() {
+    return handshake4Encryption;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/sasl/SaslDataTransferServer.java

@@ -357,7 +357,8 @@ public class SaslDataTransferServer {
 
     int magicNumber = in.readInt();
     if (magicNumber != SASL_TRANSFER_MAGIC_NUMBER) {
-      throw new InvalidMagicNumberException(magicNumber);
+      throw new InvalidMagicNumberException(magicNumber, 
+          dnConf.getEncryptDataTransfer());
     }
     try {
       // step 1

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiver.java

@@ -192,10 +192,17 @@ class DataXceiver extends Receiver implements Runnable {
           HdfsConstants.SMALL_BUFFER_SIZE);
         socketOut = saslStreams.out;
       } catch (InvalidMagicNumberException imne) {
+        if (imne.isHandshake4Encryption()) {
           LOG.info("Failed to read expected encryption handshake from client " +
               "at " + peer.getRemoteAddressString() + ". Perhaps the client " +
               "is running an older version of Hadoop which does not support " +
               "encryption");
+        } else {
+          LOG.info("Failed to read expected SASL data transfer protection " +
+              "handshake from client at " + peer.getRemoteAddressString() + 
+              ". Perhaps the client is running an older version of Hadoop " +
+              "which does not support SASL data transfer protection");
+        }
         return;
       }
       

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/protocol/datatransfer/sasl/TestSaslDataTransfer.java

@@ -25,16 +25,22 @@ import static org.junit.Assert.*;
 
 import java.io.IOException;
 
+import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.fs.BlockLocation;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FileSystemTestHelper;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.http.HttpConfig;
 import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.test.GenericTestUtils;
+import org.apache.hadoop.test.GenericTestUtils.LogCapturer;
 import org.junit.After;
+import org.junit.Assert;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -110,12 +116,28 @@ public class TestSaslDataTransfer extends SaslDataTransferTestCase {
   public void testServerSaslNoClientSasl() throws Exception {
     HdfsConfiguration clusterConf = createSecureConfig(
       "authentication,integrity,privacy");
+    // Set short retry timeouts so this test runs faster
+    clusterConf.setInt(DFSConfigKeys.DFS_CLIENT_RETRY_WINDOW_BASE, 10);
     startCluster(clusterConf);
     HdfsConfiguration clientConf = new HdfsConfiguration(clusterConf);
     clientConf.set(DFS_DATA_TRANSFER_PROTECTION_KEY, "");
-    exception.expect(IOException.class);
-    exception.expectMessage("could only be replicated to 0 nodes");
+
+    LogCapturer logs = GenericTestUtils.LogCapturer.captureLogs(
+        LogFactory.getLog(DataNode.class));
+    try {
       doTest(clientConf);
+      Assert.fail("Should fail if SASL data transfer protection is not " +
+          "configured or not supported in client");
+    } catch (IOException e) {
+      GenericTestUtils.assertMatches(e.getMessage(), 
+          "could only be replicated to 0 nodes");
+    } finally {
+      logs.stopCapturing();
+    }
+
+    GenericTestUtils.assertMatches(logs.getOutput(),
+        "Failed to read expected SASL data transfer protection " +
+        "handshake from client at");
   }
 
   @Test