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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.ipfilter;
17  
18  import io.netty.channel.Channel;
19  import io.netty.channel.ChannelFuture;
20  import io.netty.channel.ChannelFutureListener;
21  import io.netty.channel.ChannelHandlerContext;
22  import io.netty.channel.ChannelInboundHandlerAdapter;
23  
24  import java.net.SocketAddress;
25  
26  /**
27   * This class provides the functionality to either accept or reject new {@link Channel}s
28   * based on their IP address.
29   * <p>
30   * You should inherit from this class if you would like to implement your own IP-based filter. Basically you have to
31   * implement {@link #accept(ChannelHandlerContext, SocketAddress)} to decided whether you want to accept or reject
32   * a connection from the remote address.
33   * <p>
34   * Furthermore overriding {@link #channelRejected(ChannelHandlerContext, SocketAddress)} gives you the
35   * flexibility to respond to rejected (denied) connections. If you do not want to send a response, just have it return
36   * null.  Take a look at {@link RuleBasedIpFilter} for details.
37   */
38  public abstract class AbstractRemoteAddressFilter<T extends SocketAddress> extends ChannelInboundHandlerAdapter {
39  
40      @Override
41      public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
42          handleNewChannel(ctx);
43          ctx.fireChannelRegistered();
44      }
45  
46      @Override
47      public void channelActive(ChannelHandlerContext ctx) throws Exception {
48          if (!handleNewChannel(ctx)) {
49              throw new IllegalStateException("cannot determine to accept or reject a channel: " + ctx.channel());
50          } else {
51              ctx.fireChannelActive();
52          }
53      }
54  
55      private boolean handleNewChannel(ChannelHandlerContext ctx) throws Exception {
56          @SuppressWarnings("unchecked")
57          T remoteAddress = (T) ctx.channel().remoteAddress();
58  
59          // If the remote address is not available yet, defer the decision.
60          if (remoteAddress == null) {
61              return false;
62          }
63  
64          // No need to keep this handler in the pipeline anymore because the decision is going to be made now.
65          // Also, this will prevent the subsequent events from being handled by this handler.
66          ctx.pipeline().remove(this);
67  
68          if (accept(ctx, remoteAddress)) {
69              channelAccepted(ctx, remoteAddress);
70          } else {
71              ChannelFuture rejectedFuture = channelRejected(ctx, remoteAddress);
72              if (rejectedFuture != null) {
73                  rejectedFuture.addListener(ChannelFutureListener.CLOSE);
74              } else {
75                  ctx.close();
76              }
77          }
78  
79          return true;
80      }
81  
82      /**
83       * This method is called immediately after a {@link io.netty.channel.Channel} gets registered.
84       *
85       * @return Return true if connections from this IP address and port should be accepted. False otherwise.
86       */
87      protected abstract boolean accept(ChannelHandlerContext ctx, T remoteAddress) throws Exception;
88  
89      /**
90       * This method is called if {@code remoteAddress} gets accepted by
91       * {@link #accept(ChannelHandlerContext, SocketAddress)}.  You should override it if you would like to handle
92       * (e.g. respond to) accepted addresses.
93       */
94      @SuppressWarnings("UnusedParameters")
95      protected void channelAccepted(ChannelHandlerContext ctx, T remoteAddress) { }
96  
97      /**
98       * This method is called if {@code remoteAddress} gets rejected by
99       * {@link #accept(ChannelHandlerContext, SocketAddress)}.  You should override it if you would like to handle
100      * (e.g. respond to) rejected addresses.
101      *
102      * @return A {@link ChannelFuture} if you perform I/O operations, so that
103      *         the {@link Channel} can be closed once it completes. Null otherwise.
104      */
105     @SuppressWarnings("UnusedParameters")
106     protected ChannelFuture channelRejected(ChannelHandlerContext ctx, T remoteAddress) {
107         return null;
108     }
109 }