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1   /*
2    * Copyright 2016 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  
17  package io.netty.util.internal;
18  
19  import io.netty.util.NetUtil;
20  import io.netty.util.internal.logging.InternalLogger;
21  import io.netty.util.internal.logging.InternalLoggerFactory;
22  
23  import java.net.InetAddress;
24  import java.net.NetworkInterface;
25  import java.net.SocketException;
26  import java.util.Arrays;
27  import java.util.Enumeration;
28  import java.util.LinkedHashMap;
29  import java.util.Map;
30  import java.util.Map.Entry;
31  
32  import static io.netty.util.internal.EmptyArrays.EMPTY_BYTES;
33  
34  public final class MacAddressUtil {
35      private static final InternalLogger logger = InternalLoggerFactory.getInstance(MacAddressUtil.class);
36  
37      private static final int EUI64_MAC_ADDRESS_LENGTH = 8;
38      private static final int EUI48_MAC_ADDRESS_LENGTH = 6;
39  
40      /**
41       * Obtains the best MAC address found on local network interfaces.
42       * Generally speaking, an active network interface used on public
43       * networks is better than a local network interface.
44       *
45       * @return byte array containing a MAC. null if no MAC can be found.
46       */
47      public static byte[] bestAvailableMac() {
48          // Find the best MAC address available.
49          byte[] bestMacAddr = EMPTY_BYTES;
50          InetAddress bestInetAddr = NetUtil.LOCALHOST4;
51  
52          // Retrieve the list of available network interfaces.
53          Map<NetworkInterface, InetAddress> ifaces = new LinkedHashMap<NetworkInterface, InetAddress>();
54          try {
55              Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
56              if (interfaces != null) {
57                  while (interfaces.hasMoreElements()) {
58                      NetworkInterface iface = interfaces.nextElement();
59                      // Use the interface with proper INET addresses only.
60                      Enumeration<InetAddress> addrs = SocketUtils.addressesFromNetworkInterface(iface);
61                      if (addrs.hasMoreElements()) {
62                          InetAddress a = addrs.nextElement();
63                          if (!a.isLoopbackAddress()) {
64                              ifaces.put(iface, a);
65                          }
66                      }
67                  }
68              }
69          } catch (SocketException e) {
70              logger.warn("Failed to retrieve the list of available network interfaces", e);
71          }
72  
73          for (Entry<NetworkInterface, InetAddress> entry: ifaces.entrySet()) {
74              NetworkInterface iface = entry.getKey();
75              InetAddress inetAddr = entry.getValue();
76              if (iface.isVirtual()) {
77                  continue;
78              }
79  
80              byte[] macAddr;
81              try {
82                  macAddr = SocketUtils.hardwareAddressFromNetworkInterface(iface);
83              } catch (SocketException e) {
84                  logger.debug("Failed to get the hardware address of a network interface: {}", iface, e);
85                  continue;
86              }
87  
88              boolean replace = false;
89              int res = compareAddresses(bestMacAddr, macAddr);
90              if (res < 0) {
91                  // Found a better MAC address.
92                  replace = true;
93              } else if (res == 0) {
94                  // Two MAC addresses are of pretty much same quality.
95                  res = compareAddresses(bestInetAddr, inetAddr);
96                  if (res < 0) {
97                      // Found a MAC address with better INET address.
98                      replace = true;
99                  } else if (res == 0) {
100                     // Cannot tell the difference.  Choose the longer one.
101                     if (bestMacAddr.length < macAddr.length) {
102                         replace = true;
103                     }
104                 }
105             }
106 
107             if (replace) {
108                 bestMacAddr = macAddr;
109                 bestInetAddr = inetAddr;
110             }
111         }
112 
113         if (bestMacAddr == EMPTY_BYTES) {
114             return null;
115         }
116 
117         switch (bestMacAddr.length) {
118             case EUI48_MAC_ADDRESS_LENGTH: // EUI-48 - convert to EUI-64
119                 byte[] newAddr = new byte[EUI64_MAC_ADDRESS_LENGTH];
120                 System.arraycopy(bestMacAddr, 0, newAddr, 0, 3);
121                 newAddr[3] = (byte) 0xFF;
122                 newAddr[4] = (byte) 0xFE;
123                 System.arraycopy(bestMacAddr, 3, newAddr, 5, 3);
124                 bestMacAddr = newAddr;
125                 break;
126             default: // Unknown
127                 bestMacAddr = Arrays.copyOf(bestMacAddr, EUI64_MAC_ADDRESS_LENGTH);
128         }
129 
130         return bestMacAddr;
131     }
132 
133     /**
134      * Returns the result of {@link #bestAvailableMac()} if non-{@code null} otherwise returns a random EUI-64 MAC
135      * address.
136      */
137     public static byte[] defaultMachineId() {
138         byte[] bestMacAddr = bestAvailableMac();
139         if (bestMacAddr == null) {
140             bestMacAddr = new byte[EUI64_MAC_ADDRESS_LENGTH];
141             PlatformDependent.threadLocalRandom().nextBytes(bestMacAddr);
142             logger.warn(
143                     "Failed to find a usable hardware address from the network interfaces; using random bytes: {}",
144                     formatAddress(bestMacAddr));
145         }
146         return bestMacAddr;
147     }
148 
149     /**
150      * Parse a EUI-48, MAC-48, or EUI-64 MAC address from a {@link String} and return it as a {@code byte[]}.
151      * @param value The string representation of the MAC address.
152      * @return The byte representation of the MAC address.
153      */
154     public static byte[] parseMAC(String value) {
155         final byte[] machineId;
156         final char separator;
157         switch (value.length()) {
158             case 17:
159                 separator = value.charAt(2);
160                 validateMacSeparator(separator);
161                 machineId = new byte[EUI48_MAC_ADDRESS_LENGTH];
162                 break;
163             case 23:
164                 separator = value.charAt(2);
165                 validateMacSeparator(separator);
166                 machineId = new byte[EUI64_MAC_ADDRESS_LENGTH];
167                 break;
168             default:
169                 throw new IllegalArgumentException("value is not supported [MAC-48, EUI-48, EUI-64]");
170         }
171 
172         final int end = machineId.length - 1;
173         int j = 0;
174         for (int i = 0; i < end; ++i, j += 3) {
175             final int sIndex = j + 2;
176             machineId[i] = StringUtil.decodeHexByte(value, j);
177             if (value.charAt(sIndex) != separator) {
178                 throw new IllegalArgumentException("expected separator '" + separator + " but got '" +
179                         value.charAt(sIndex) + "' at index: " + sIndex);
180             }
181         }
182 
183         machineId[end] = StringUtil.decodeHexByte(value, j);
184 
185         return machineId;
186     }
187 
188     private static void validateMacSeparator(char separator) {
189         if (separator != ':' && separator != '-') {
190             throw new IllegalArgumentException("unsupported separator: " + separator + " (expected: [:-])");
191         }
192     }
193 
194     /**
195      * @param addr byte array of a MAC address.
196      * @return hex formatted MAC address.
197      */
198     public static String formatAddress(byte[] addr) {
199         StringBuilder buf = new StringBuilder(24);
200         for (byte b: addr) {
201             buf.append(String.format("%02x:", b & 0xff));
202         }
203         return buf.substring(0, buf.length() - 1);
204     }
205 
206     /**
207      * @return positive - current is better, 0 - cannot tell from MAC addr, negative - candidate is better.
208      */
209     // visible for testing
210     static int compareAddresses(byte[] current, byte[] candidate) {
211         if (candidate == null || candidate.length < EUI48_MAC_ADDRESS_LENGTH) {
212             return 1;
213         }
214 
215         // Must not be filled with only 0 and 1.
216         boolean onlyZeroAndOne = true;
217         for (byte b: candidate) {
218             if (b != 0 && b != 1) {
219                 onlyZeroAndOne = false;
220                 break;
221             }
222         }
223 
224         if (onlyZeroAndOne) {
225             return 1;
226         }
227 
228         // Must not be a multicast address
229         if ((candidate[0] & 1) != 0) {
230             return 1;
231         }
232 
233         // Prefer globally unique address.
234         if ((candidate[0] & 2) == 0) {
235             if (current.length != 0 && (current[0] & 2) == 0) {
236                 // Both current and candidate are globally unique addresses.
237                 return 0;
238             } else {
239                 // Only candidate is globally unique.
240                 return -1;
241             }
242         } else {
243             if (current.length != 0 && (current[0] & 2) == 0) {
244                 // Only current is globally unique.
245                 return 1;
246             } else {
247                 // Both current and candidate are non-unique.
248                 return 0;
249             }
250         }
251     }
252 
253     /**
254      * @return positive - current is better, 0 - cannot tell, negative - candidate is better
255      */
256     private static int compareAddresses(InetAddress current, InetAddress candidate) {
257         return scoreAddress(current) - scoreAddress(candidate);
258     }
259 
260     private static int scoreAddress(InetAddress addr) {
261         if (addr.isAnyLocalAddress() || addr.isLoopbackAddress()) {
262             return 0;
263         }
264         if (addr.isMulticastAddress()) {
265             return 1;
266         }
267         if (addr.isLinkLocalAddress()) {
268             return 2;
269         }
270         if (addr.isSiteLocalAddress()) {
271             return 3;
272         }
273 
274         return 4;
275     }
276 
277     private MacAddressUtil() { }
278 }