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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License.
18   *
19   */
20  
21  package org.apache.mina.filter.firewall;
22  
23  import java.net.Inet4Address;
24  import java.net.InetAddress;
25  
26  /**
27   * A IP subnet using the CIDR notation. Currently, only IP version 4
28   * address are supported.
29   *
30   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
31   */
32  public class Subnet {
33  
34      private static final int IP_MASK = 0x80000000;
35  
36      private static final int BYTE_MASK = 0xFF;
37  
38      private InetAddress subnet;
39  
40      private int subnetInt;
41  
42      private int subnetMask;
43  
44      private int suffix;
45  
46      /**
47       * Creates a subnet from CIDR notation. For example, the subnet
48       * 192.168.0.0/24 would be created using the {@link InetAddress}  
49       * 192.168.0.0 and the mask 24.
50       * @param subnet The {@link InetAddress} of the subnet
51       * @param mask The mask
52       */
53      public Subnet(InetAddress subnet, int mask) {
54          if (subnet == null) {
55              throw new IllegalArgumentException("Subnet address can not be null");
56          }
57          if (!(subnet instanceof Inet4Address)) {
58              throw new IllegalArgumentException("Only IPv4 supported");
59          }
60  
61          if (mask < 0 || mask > 32) {
62              throw new IllegalArgumentException("Mask has to be an integer between 0 and 32");
63          }
64  
65          this.subnet = subnet;
66          this.subnetInt = toInt(subnet);
67          this.suffix = mask;
68  
69          // binary mask for this subnet
70          this.subnetMask = IP_MASK >> (mask - 1);
71      }
72  
73      /** 
74       * Converts an IP address into an integer
75       */
76      private int toInt(InetAddress inetAddress) {
77          byte[] address = inetAddress.getAddress();
78          int result = 0;
79          for (int i = 0; i < address.length; i++) {
80              result <<= 8;
81              result |= address[i] & BYTE_MASK;
82          }
83          return result;
84      }
85  
86      /**
87       * Converts an IP address to a subnet using the provided 
88       * mask
89       * @param address The address to convert into a subnet
90       * @return The subnet as an integer
91       */
92      private int toSubnet(InetAddress address) {
93          return toInt(address) & subnetMask;
94      }
95  
96      /**
97       * Checks if the {@link InetAddress} is within this subnet
98       * @param address The {@link InetAddress} to check
99       * @return True if the address is within this subnet, false otherwise
100      */
101     public boolean inSubnet(InetAddress address) {
102         return toSubnet(address) == subnetInt;
103     }
104 
105     /**
106      * @see Object#toString()
107      */
108     @Override
109     public String toString() {
110         return subnet.getHostAddress() + "/" + suffix;
111     }
112 
113     @Override
114     public boolean equals(Object obj) {
115         if (!(obj instanceof Subnet)) {
116             return false;
117         }
118 
119         Subnet other = (Subnet) obj;
120 
121         return other.subnetInt == subnetInt && other.suffix == suffix;
122     }
123 
124 }