HDFS-14451. Incorrect header or version mismatch log message. Contributed by Shweta.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
(cherry picked from commit 93d7630062247793a4860704fad4a31437693de1)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java

@@ -2070,11 +2070,17 @@ public abstract class Server {
             setupHttpRequestOnIpcPortResponse();
             return -1;
           }
-          
-          if (!RpcConstants.HEADER.equals(dataLengthBuffer)
-              || version != CURRENT_VERSION) {
+
+          if(!RpcConstants.HEADER.equals(dataLengthBuffer)) {
+            LOG.warn("Incorrect RPC Header length from {}:{} "
+                + "expected length: {} got length: {}",
+                hostAddress, remotePort, RpcConstants.HEADER, dataLengthBuffer);
+            setupBadVersionResponse(version);
+            return -1;
+          }
+          if (version != CURRENT_VERSION) {
             //Warning is ok since this is not supposed to happen.
-            LOG.warn("Incorrect header or version mismatch from " + 
+            LOG.warn("Version mismatch from " +
                      hostAddress + ":" + remotePort +
                      " got version " + version + 
                      " expected version " + CURRENT_VERSION);