MacAddressUtil.java — netty Source File

Source Code

/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project 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:
 *
 *   https://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 io.netty.util.internal;

import io.netty.util.NetUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ThreadLocalRandom;

import static io.netty.util.internal.EmptyArrays.EMPTY_BYTES;

public final class MacAddressUtil {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(MacAddressUtil.class);

    private static final int EUI64_MAC_ADDRESS_LENGTH = 8;
    private static final int EUI48_MAC_ADDRESS_LENGTH = 6;

    /**
     * Obtains the best MAC address found on local network interfaces.
     * Generally speaking, an active network interface used on public
     * networks is better than a local network interface.
     *
     * @return byte array containing a MAC. null if no MAC can be found.
     */
    public static byte[] bestAvailableMac() {
        // Find the best MAC address available.
        byte[] bestMacAddr = EMPTY_BYTES;
        InetAddress bestInetAddr = NetUtil.LOCALHOST4;

        // Retrieve the list of available network interfaces.
        Map<NetworkInterface, InetAddress> ifaces = new LinkedHashMap<NetworkInterface, InetAddress>();
        for (NetworkInterface iface: NetUtil.NETWORK_INTERFACES) {
            // Use the interface with proper INET addresses only.
            Enumeration<InetAddress> addrs = SocketUtils.addressesFromNetworkInterface(iface);
            if (addrs.hasMoreElements()) {
                InetAddress a = addrs.nextElement();
                if (!a.isLoopbackAddress()) {
// ... (211 more lines)