Handle ping correctly in NioTransport (#25462)

Our current TCPTransport logic assumes that we do not pass pings to
the TCPTransport level.

This commit fixes an issue where NioTransport was passing pings to
TCPTransport and leading to exceptions.

Author: Tim-Brooks

test/framework/src/main/java/org/elasticsearch/transport/nio/channel/TcpReadContext.java

@@ -67,6 +67,8 @@ public int read() throws IOException {
 
         BytesReference message;
 
+        // Frame decoder will throw an exception if the message is improperly formatted, the header is incorrect,
+        // or the message is corrupted
         while ((message = frameDecoder.decode(createCompositeBuffer(), rawBytesCount)) != null) {
             int messageLengthWithHeader = message.length();
             NetworkBytesReference.vectorizedIncrementReadIndexes(references, messageLengthWithHeader);
@@ -75,7 +77,11 @@ public int read() throws IOException {
 
             try {
                 BytesReference messageWithoutHeader = message.slice(6, message.length() - 6);
-                handler.handleMessage(messageWithoutHeader, channel, channel.getProfile(), messageWithoutHeader.length());
+
+                // A message length of 6 bytes it is just a ping. Ignore for now.
+                if (messageLengthWithHeader != 6) {
+                    handler.handleMessage(messageWithoutHeader, channel, channel.getProfile(), messageWithoutHeader.length());
+                }
             } catch (Exception e) {
                 handler.handleException(channel, e);
             }