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Expose Helper to obtain the "best" mac address.

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Motivation:

The implementation of obtaining the best possible mac address is very good. There are many sub-par implementations proposed on stackoverflow.
While not strictly a netty concern, it would be nice to offer this util also to netty users.

Modifications:

extract DefaultChannelId#defaultMachineId code obtaining the "best" mac into a new helper called MacAddress, keep the random bytes fallback in DefaultChannelID.

Result:

New helper available.
This commit is contained in:
Fabian Lange 2016-02-03 17:28:39 +01:00 committed by Norman Maurer
parent d9f938ca03
commit a51e2c8769
2 changed files with 228 additions and 179 deletions
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221
common/src/main/java/io/netty/util/internal/MacAddressUtil.java Normal file
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@ -0,0 +1,221 @@
/*
* 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:
*
* http://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 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 io.netty.util.NetUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
public final class MacAddressUtil {
/**
* Length of a valid MAC address.
*/
public static final int MAC_ADDRESS_LENGTH = 8;
private static final byte[] NOT_FOUND = { -1 };
private static final InternalLogger logger = InternalLoggerFactory.getInstance(MacAddressUtil.class);
/**
* 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 = NOT_FOUND;
InetAddress bestInetAddr = NetUtil.LOCALHOST4;
// Retrieve the list of available network interfaces.
Map<NetworkInterface, InetAddress> ifaces = new LinkedHashMap<NetworkInterface, InetAddress>();
try {
for (Enumeration<NetworkInterface> i = NetworkInterface.getNetworkInterfaces(); i.hasMoreElements();) {
NetworkInterface iface = i.nextElement();
// Use the interface with proper INET addresses only.
Enumeration<InetAddress> addrs = iface.getInetAddresses();
if (addrs.hasMoreElements()) {
InetAddress a = addrs.nextElement();
if (!a.isLoopbackAddress()) {
ifaces.put(iface, a);
}
}
}
} catch (SocketException e) {
logger.warn("Failed to retrieve the list of available network interfaces", e);
}
for (Entry<NetworkInterface, InetAddress> entry: ifaces.entrySet()) {
NetworkInterface iface = entry.getKey();
InetAddress inetAddr = entry.getValue();
if (iface.isVirtual()) {
continue;
}
byte[] macAddr;
try {
macAddr = iface.getHardwareAddress();
} catch (SocketException e) {
logger.debug("Failed to get the hardware address of a network interface: {}", iface, e);
continue;
}
boolean replace = false;
int res = compareAddresses(bestMacAddr, macAddr);
if (res < 0) {
// Found a better MAC address.
replace = true;
} else if (res == 0) {
// Two MAC addresses are of pretty much same quality.
res = compareAddresses(bestInetAddr, inetAddr);
if (res < 0) {
// Found a MAC address with better INET address.
replace = true;
} else if (res == 0) {
// Cannot tell the difference. Choose the longer one.
if (bestMacAddr.length < macAddr.length) {
replace = true;
}
}
}
if (replace) {
bestMacAddr = macAddr;
bestInetAddr = inetAddr;
}
}
if (bestMacAddr == NOT_FOUND) {
return null;
}
switch (bestMacAddr.length) {
case 6: // EUI-48 - convert to EUI-64
byte[] newAddr = new byte[MAC_ADDRESS_LENGTH];
System.arraycopy(bestMacAddr, 0, newAddr, 0, 3);
newAddr[3] = (byte) 0xFF;
newAddr[4] = (byte) 0xFE;
System.arraycopy(bestMacAddr, 3, newAddr, 5, 3);
bestMacAddr = newAddr;
break;
default: // Unknown
bestMacAddr = Arrays.copyOf(bestMacAddr, MAC_ADDRESS_LENGTH);
}
return bestMacAddr;
}
/**
* @param addr byte array of a MAC address.
* @return hex formatted MAC address.
*/
public static String formatAddress(byte[] addr) {
StringBuilder buf = new StringBuilder(24);
for (byte b: addr) {
buf.append(String.format("%02x:", b & 0xff));
}
return buf.substring(0, buf.length() - 1);
}
/**
* @return positive - current is better, 0 - cannot tell from MAC addr, negative - candidate is better.
*/
private static int compareAddresses(byte[] current, byte[] candidate) {
if (candidate == null) {
return 1;
}
// Must be EUI-48 or longer.
if (candidate.length < 6) {
return 1;
}
// Must not be filled with only 0 and 1.
boolean onlyZeroAndOne = true;
for (byte b: candidate) {
if (b != 0 && b != 1) {
onlyZeroAndOne = false;
break;
}
}
if (onlyZeroAndOne) {
return 1;
}
// Must not be a multicast address
if ((candidate[0] & 1) != 0) {
return 1;
}
// Prefer globally unique address.
if ((current[0] & 2) == 0) {
if ((candidate[0] & 2) == 0) {
// Both current and candidate are globally unique addresses.
return 0;
} else {
// Only current is globally unique.
return 1;
}
} else {
if ((candidate[0] & 2) == 0) {
// Only candidate is globally unique.
return -1;
} else {
// Both current and candidate are non-unique.
return 0;
}
}
}
/**
* @return positive - current is better, 0 - cannot tell, negative - candidate is better
*/
private static int compareAddresses(InetAddress current, InetAddress candidate) {
return scoreAddress(current) - scoreAddress(candidate);
}
private static int scoreAddress(InetAddress addr) {
if (addr.isAnyLocalAddress() || addr.isLoopbackAddress()) {
return 0;
}
if (addr.isMulticastAddress()) {
return 1;
}
if (addr.isLinkLocalAddress()) {
return 2;
}
if (addr.isSiteLocalAddress()) {
return 3;
}
return 4;
}
private MacAddressUtil() { }
}

186
transport/src/main/java/io/netty/channel/DefaultChannelId.java
View File

@ -17,6 +17,7 @@
package io.netty.channel;
import io.netty.buffer.ByteBufUtil;
import io.netty.util.internal.MacAddressUtil;
import io.netty.util.internal.EmptyArrays;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.SystemPropertyUtil;
@ -25,15 +26,7 @@ import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.lang.reflect.Method;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
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.atomic.AtomicInteger;
import java.util.regex.Pattern;
@ -47,7 +40,7 @@ final class DefaultChannelId implements ChannelId {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultChannelId.class);
private static final Pattern MACHINE_ID_PATTERN = Pattern.compile("^(?:[0-9a-fA-F][:-]?){6,8}$");
private static final int MACHINE_ID_LEN = 8;
private static final int MACHINE_ID_LEN = MacAddressUtil.MAC_ADDRESS_LENGTH;
private static final byte[] MACHINE_ID;
private static final int PROCESS_ID_LEN = 4;
// Maximal value for 64bit systems is 2^22. See man 5 proc.
@ -107,7 +100,7 @@ final class DefaultChannelId implements ChannelId {
if (machineId == null) {
machineId = defaultMachineId();
if (logger.isDebugEnabled()) {
logger.debug("-Dio.netty.machineId: {} (auto-detected)", formatAddress(machineId));
logger.debug("-Dio.netty.machineId: {} (auto-detected)", MacAddressUtil.formatAddress(machineId));
}
}
@ -128,182 +121,17 @@ final class DefaultChannelId implements ChannelId {
}
private static byte[] defaultMachineId() {
// Find the best MAC address available.
final byte[] NOT_FOUND = { -1 };
byte[] bestMacAddr = NOT_FOUND;
InetAddress bestInetAddr = null;
try {
bestInetAddr = InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 });
} catch (UnknownHostException e) {
// Never happens.
PlatformDependent.throwException(e);
}
// Retrieve the list of available network interfaces.
Map<NetworkInterface, InetAddress> ifaces = new LinkedHashMap<NetworkInterface, InetAddress>();
try {
for (Enumeration<NetworkInterface> i = NetworkInterface.getNetworkInterfaces(); i.hasMoreElements();) {
NetworkInterface iface = i.nextElement();
// Use the interface with proper INET addresses only.
Enumeration<InetAddress> addrs = iface.getInetAddresses();
if (addrs.hasMoreElements()) {
InetAddress a = addrs.nextElement();
if (!a.isLoopbackAddress()) {
ifaces.put(iface, a);
}
}
}
} catch (SocketException e) {
logger.warn("Failed to retrieve the list of available network interfaces", e);
}
for (Entry<NetworkInterface, InetAddress> entry: ifaces.entrySet()) {
NetworkInterface iface = entry.getKey();
InetAddress inetAddr = entry.getValue();
if (iface.isVirtual()) {
continue;
}
byte[] macAddr;
try {
macAddr = iface.getHardwareAddress();
} catch (SocketException e) {
logger.debug("Failed to get the hardware address of a network interface: {}", iface, e);
continue;
}
boolean replace = false;
int res = compareAddresses(bestMacAddr, macAddr);
if (res < 0) {
// Found a better MAC address.
replace = true;
} else if (res == 0) {
// Two MAC addresses are of pretty much same quality.
res = compareAddresses(bestInetAddr, inetAddr);
if (res < 0) {
// Found a MAC address with better INET address.
replace = true;
} else if (res == 0) {
// Cannot tell the difference. Choose the longer one.
if (bestMacAddr.length < macAddr.length) {
replace = true;
}
}
}
if (replace) {
bestMacAddr = macAddr;
bestInetAddr = inetAddr;
}
}
if (bestMacAddr == NOT_FOUND) {
bestMacAddr = new byte[MACHINE_ID_LEN];
byte[] bestMacAddr = MacAddressUtil.bestAvailableMac();
if (bestMacAddr == null) {
bestMacAddr = new byte[MacAddressUtil.MAC_ADDRESS_LENGTH];
ThreadLocalRandom.current().nextBytes(bestMacAddr);
logger.warn(
"Failed to find a usable hardware address from the network interfaces; using random bytes: {}",
formatAddress(bestMacAddr));
MacAddressUtil.formatAddress(bestMacAddr));
}
switch (bestMacAddr.length) {
case 6: // EUI-48 - convert to EUI-64
byte[] newAddr = new byte[MACHINE_ID_LEN];
System.arraycopy(bestMacAddr, 0, newAddr, 0, 3);
newAddr[3] = (byte) 0xFF;
newAddr[4] = (byte) 0xFE;
System.arraycopy(bestMacAddr, 3, newAddr, 5, 3);
bestMacAddr = newAddr;
break;
default: // Unknown
bestMacAddr = Arrays.copyOf(bestMacAddr, MACHINE_ID_LEN);
}
return bestMacAddr;
}
/**
* @return positive - current is better, 0 - cannot tell from MAC addr, negative - candidate is better.
*/
private static int compareAddresses(byte[] current, byte[] candidate) {
if (candidate == null) {
return 1;
}
// Must be EUI-48 or longer.
if (candidate.length < 6) {
return 1;
}
// Must not be filled with only 0 and 1.
boolean onlyZeroAndOne = true;
for (byte b: candidate) {
if (b != 0 && b != 1) {
onlyZeroAndOne = false;
break;
}
}
if (onlyZeroAndOne) {
return 1;
}
// Must not be a multicast address
if ((candidate[0] & 1) != 0) {
return 1;
}
// Prefer globally unique address.
if ((current[0] & 2) == 0) {
if ((candidate[0] & 2) == 0) {
// Both current and candidate are globally unique addresses.
return 0;
} else {
// Only current is globally unique.
return 1;
}
} else {
if ((candidate[0] & 2) == 0) {
// Only candidate is globally unique.
return -1;
} else {
// Both current and candidate are non-unique.
return 0;
}
}
}
/**
* @return positive - current is better, 0 - cannot tell, negative - candidate is better
*/
private static int compareAddresses(InetAddress current, InetAddress candidate) {
return scoreAddress(current) - scoreAddress(candidate);
}
private static int scoreAddress(InetAddress addr) {
if (addr.isAnyLocalAddress() || addr.isLoopbackAddress()) {
return 0;
}
if (addr.isMulticastAddress()) {
return 1;
}
if (addr.isLinkLocalAddress()) {
return 2;
}
if (addr.isSiteLocalAddress()) {
return 3;
}
return 4;
}
private static String formatAddress(byte[] addr) {
StringBuilder buf = new StringBuilder(24);
for (byte b: addr) {
buf.append(String.format("%02x:", b & 0xff));
}
return buf.substring(0, buf.length() - 1);
}
private static int defaultProcessId() {
final ClassLoader loader = PlatformDependent.getSystemClassLoader();
String value;