/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.NetworkInterface;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.URI;
import java.net.UnknownHostException;
import java.net.ConnectException;
import java.nio.channels.SocketChannel;
import java.util.Map.Entry;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

import javax.net.SocketFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.ipc.Server;
import org.apache.hadoop.ipc.VersionedProtocol;
import org.apache.hadoop.syscall.LinuxSystemCall;
import org.apache.hadoop.util.ReflectionUtils;

public class NetUtils {
	private static final Log LOG = LogFactory.getLog(NetUtils.class);
	// Insure that Network Control bits in sock will never be used,
	// allow to set them may cause issue on the network, killing network
	// control traffic.
	// NC bits are: 
	// in TOS Dec: 192 and up.
	public static final int IP_TOS_MAX_VALUE = 191;
	public static final int NOT_SET_IP_TOS = -1;
	
	private static Map<String, String> hostToResolved = 
			new HashMap<String, String>();

  /**
   * Get the socket factory for the given class according to its
   * configuration parameter
   * <tt>hadoop.rpc.socket.factory.class.&lt;ClassName&gt;</tt>. When no
   * such parameter exists then fall back on the default socket factory as
   * configured by <tt>hadoop.rpc.socket.factory.class.default</tt>. If
   * this default socket factory is not configured, then fall back on the JVM
   * default socket factory.
   * 
   * @param conf the configuration
   * @param clazz the class (usually a {@link VersionedProtocol})
   * @return a socket factory
   */
  public static SocketFactory getSocketFactory(Configuration conf,
      Class<?> clazz) {

    SocketFactory factory = null;

    String propValue =
        conf.get("hadoop.rpc.socket.factory.class." + clazz.getSimpleName());
    if ((propValue != null) && (propValue.length() > 0))
      factory = getSocketFactoryFromProperty(conf, propValue);

    if (factory == null)
      factory = getDefaultSocketFactory(conf);

    return factory;
  }

  /**
   * Get the default socket factory as specified by the configuration
   * parameter <tt>hadoop.rpc.socket.factory.default</tt>
   * 
   * @param conf the configuration
   * @return the default socket factory as specified in the configuration or
   *         the JVM default socket factory if the configuration does not
   *         contain a default socket factory property.
   */
  public static SocketFactory getDefaultSocketFactory(Configuration conf) {

    String propValue = conf.get("hadoop.rpc.socket.factory.class.default");
    if ((propValue == null) || (propValue.length() == 0))
      return SocketFactory.getDefault();

    return getSocketFactoryFromProperty(conf, propValue);
  }

  /**
   * Get the socket factory corresponding to the given proxy URI. If the
   * given proxy URI corresponds to an absence of configuration parameter,
   * returns null. If the URI is malformed raises an exception.
   * 
   * @param propValue the property which is the class name of the
   *        SocketFactory to instantiate; assumed non null and non empty.
   * @return a socket factory as defined in the property value.
   */