001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.lib.servlet;
020
021
022import org.apache.hadoop.classification.InterfaceAudience;
023
024import javax.servlet.Filter;
025import javax.servlet.FilterChain;
026import javax.servlet.FilterConfig;
027import javax.servlet.ServletException;
028import javax.servlet.ServletRequest;
029import javax.servlet.ServletResponse;
030import java.io.IOException;
031import java.net.InetAddress;
032import java.net.UnknownHostException;
033import org.slf4j.Logger;
034import org.slf4j.LoggerFactory;
035
036/**
037 * Filter that resolves the requester hostname.
038 */
039@InterfaceAudience.Private
040public class HostnameFilter implements Filter {
041  static final ThreadLocal<String> HOSTNAME_TL = new ThreadLocal<String>();
042  private static final Logger log = LoggerFactory.getLogger(HostnameFilter.class);
043
044  /**
045   * Initializes the filter.
046   * <p/>
047   * This implementation is a NOP.
048   *
049   * @param config filter configuration.
050   *
051   * @throws ServletException thrown if the filter could not be initialized.
052   */
053  @Override
054  public void init(FilterConfig config) throws ServletException {
055  }
056
057  /**
058   * Resolves the requester hostname and delegates the request to the chain.
059   * <p/>
060   * The requester hostname is available via the {@link #get} method.
061   *
062   * @param request servlet request.
063   * @param response servlet response.
064   * @param chain filter chain.
065   *
066   * @throws IOException thrown if an IO error occurrs.
067   * @throws ServletException thrown if a servet error occurrs.
068   */
069  @Override
070  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
071    throws IOException, ServletException {
072    try {
073      String hostname;
074      try {
075        String address = request.getRemoteAddr();
076        if (address != null) {
077          hostname = InetAddress.getByName(address).getCanonicalHostName();
078        } else {
079          log.warn("Request remote address is NULL");
080          hostname = "???";
081        }
082      } catch (UnknownHostException ex) {
083        log.warn("Request remote address could not be resolved, {0}", ex.toString(), ex);
084        hostname = "???";
085      }
086      HOSTNAME_TL.set(hostname);
087      chain.doFilter(request, response);
088    } finally {
089      HOSTNAME_TL.remove();
090    }
091  }
092
093  /**
094   * Returns the requester hostname.
095   *
096   * @return the requester hostname.
097   */
098  public static String get() {
099    return HOSTNAME_TL.get();
100  }
101
102  /**
103   * Destroys the filter.
104   * <p/>
105   * This implementation is a NOP.
106   */
107  @Override
108  public void destroy() {
109  }
110}