ZOOKEEPER-2949: using hostname and port to create SSLEngine

If the server has more than one host name, and serve each host name with different certificates. then the ssl client must provide the server name in the ssl Hello packet, to tell the server which certificate to use.
This is especially important when the client connect to a load balancer with different backend services.

https://en.wikipedia.org/wiki/Server_Name_Indication

Author: f00231050 <shaobao.feng@huawei.com>

Reviewers: Andor Molnár <andor@cloudera.com>, Abraham Fine <afine@apache.org>

Closes #423 from abel-von/ZOOKEEPER-2949

src/java/main/org/apache/zookeeper/ClientCnxnSocketNetty.java

@@ -112,7 +112,7 @@ public class ClientCnxnSocketNetty extends ClientCnxnSocket {
 
         ClientBootstrap bootstrap = new ClientBootstrap(channelFactory);
 
-        bootstrap.setPipelineFactory(new ZKClientPipelineFactory());
+        bootstrap.setPipelineFactory(new ZKClientPipelineFactory(addr.getHostString(), addr.getPort()));
         bootstrap.setOption("soLinger", -1);
         bootstrap.setOption("tcpNoDelay", true);
 
@@ -340,6 +340,7 @@ public class ClientCnxnSocketNetty extends ClientCnxnSocket {
             return instance;
         }
     }
+
     /**
      * ZKClientPipelineFactory is the netty pipeline factory for this netty
      * connection implementation.
@@ -347,6 +348,13 @@ public class ClientCnxnSocketNetty extends ClientCnxnSocket {
     private class ZKClientPipelineFactory implements ChannelPipelineFactory {
         private SSLContext sslContext = null;
         private SSLEngine sslEngine = null;
+        private String host;
+        private int port;
+
+        public ZKClientPipelineFactory(String host, int port) {
+            this.host = host;
+            this.port = port;
+        }
 
         @Override
         public ChannelPipeline getPipeline() throws Exception {
@@ -363,7 +371,7 @@ public class ClientCnxnSocketNetty extends ClientCnxnSocket {
         private synchronized void initSSL(ChannelPipeline pipeline) throws SSLContextException {
             if (sslContext == null || sslEngine == null) {
                 sslContext = X509Util.createSSLContext(clientConfig);
-                sslEngine = sslContext.createSSLEngine();
+                sslEngine = sslContext.createSSLEngine(host,port);
                 sslEngine.setUseClientMode(true);
             }
             pipeline.addLast("ssl", new SslHandler(sslEngine));