Understanding JDK 1.6 on Ubuntu Linux IPv6 output handling
I'm running Ubuntu 10.10 and my hosts configuration are as following:
root@maxim-desktop:~# cat /etc/hosts
192.168.20.20 maxim-desktop # Added by NetworkManager
192.168.10.20 maxim-lp
127.0.0.1 localhost.localdomain localhost
::1 maxim-desktop localhost6.localdomain6 localhost6
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
root@maxim-desktop:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.20.1
root@maxim-desktop:~# cat /etc/hostname
maxim-desktop
root@maxim-desktop:~# hostname
maxim-desktop
root@maxim-desktop:~# hostname --fqdn
root@maxim-desktop:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:1c:c0:f2:ba:89
inet addr:192.168.20.20 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::21c:c0ff:fef2:ba89/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:9023854 errors:0 dropped:0 overruns:0 frame:0
TX packets:8532803 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4839992361 (4.8 GB) TX bytes:1067998152 (1.0 GB)
Interrupt:20 Memory:d3300000-d3320000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:12333251 errors:0 dropped:0 overruns:0 frame:0
TX packets:12333251 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3216352432 (3.2 GB) TX bytes:3216352432 (3.2 GB)
I'm trying to reach the same result from within java code.
Sadly, the following code just doesn't seem to cut it through.
//Copyright (c) 2011, Maxim Veksler
//All rights reserved.
//
//Redistribution and use in source and binary forms, with or without
//modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of the <organization> nor the
// names of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
//
//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
//ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
//WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
//DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
//DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
//(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
//LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
//ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
//(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
//SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Hostname and IP address info, based on JDK6 NetworkInterface
*
* @author Maxim Veksler <maxim@vekslers.org>
*/
public class NetworkUtil {
private static Logger log = LoggerFactory.getLogger(NetworkUtil.class);
public static void main(String[] args) {
System.out.println("MAC: " + NetworkUtil.getMachineMac());
System.out.println("HOSTNAME: " + NetworkUtil.getMachineHostname());
System.out.println("IP: " + NetworkUtil.getMachineIPAddress());
System.out.println("HOSTNAME ipv6: " + NetworkUtil.getMachineIPv6Hostname());
System.out.println("IP ipv6: " + NetworkUtil.getMachineIPv6Address());
}
/**
* Get the MAC address of the remote IP (if on local LAN).
* @param hostnameOrIP The target IP or Hostname (if you have DNS configured).
*
* @return MAC address if IP in local LAN, null if not.
*/
public static String getRemoteHostMac(String hostnameOrIP) {
try {
InetAddress address = InetAddress.getByName(hostnameOrIP);
NetworkInterface networkInterface = NetworkInterface.getByInetAddress(address);
return obtainMACFromAddress(networkInterface);
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain MAC address for address " + hostnameOrIP, e);
}
}
// Means we had a failure.
return null;
}
/**
* Get the machine address of the machine we are currently running on.
* @return something like 08-00-27-DC-4A-9E or null if can't obtain mac
*/
public static String getMachineMac() {
try {
return obtainMACFromAddress(getNonLoopbackNetworkInterface());
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain MAC address for localhost", e);
}
}
return null;
}
/**
* Get machine hostname, based on IPv4 configurations.
*
* @return String representing FQDN or null if can't find hostname
*/
public static String getMachineHostname() {
try {
NetworkInterface networkInterface = getNonLoopbackNetworkInterface();
Inet4Address address = getInet4Address(networkInterface);
if(address != null)
return address.getCanonicalHostName();
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain MachineHostname", e);
}
}
return null;
}
/**
* Get machine hostname, based on IPv6 configurations.
* @return String representing FQDN or null if can't find hostname
*/
public static String getMachineIPv6Hostname() {
try {
NetworkInterface networkInterface = getNonLoopbackNetworkInterface();
Inet6Address address = getInet6Address(networkInterface);
if(address != null)
return address.getCanonicalHostName();
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain IPv6Hostname", e);
}
}
return null;
}
/**
* Get machine IP, based on IPv4 configurations.
*
* @return String representing IP or null if can't find properly configured interface
*/
public static String getMachineIPAddress() {
try {
NetworkInterface networkInterface = getNonLoopbackNetworkInterface();
Inet4Address address = getInet4Address(networkInterface);
if(address != null)
return address.getHostAddress();
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain MachineIPAddress", e);
}
}
return null;
}
/**
* Get machine IP, based on IPv6 configurations.
*
* @return String representing IP or null if can't find properly configured interface
*/
public static String getMachineIPv6Address() {
try {
NetworkInterface networkInterface = getNonLoopbackNetworkInterface();
Inet6Address address = getInet6Address(networkInterface);
if(address != null)
return address.getHostAddress();
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("Failed to obtain MachineIPv6Address", e);
}
}
return null;
}
/*
* ########################
* Helper private functions
*/
private static String obtainMACFromAddress(NetworkInterface networkInterface) throws SocketException {
if(networkInterface != null) {
byte[] mac = networkInterface.getHardwareAddress();
if(mac == null)
throw new Error("Failed to obtain mac address from interface: " + networkInterface.getDisplayName());
StringBuilder stringBuilder = new StringBuilder(17);
/*
* Extract each array of mac address and convert it开发者_运维知识库 to hexa with the
* following format 08-00-27-DC-4A-9E.
*/
for (int i = 0; i < mac.length; i++) {
stringBuilder.append(String.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : ""));
}
return stringBuilder.toString();
}
return null;
}
private static Inet4Address getInet4Address(NetworkInterface networkInterface) {
if(networkInterface != null) {
Enumeration<InetAddress> NICAddresses = networkInterface.getInetAddresses();
while(NICAddresses.hasMoreElements()) {
InetAddress address = NICAddresses.nextElement();
if(address instanceof Inet4Address)
return (Inet4Address)address;
}
}
return null;
}
private static Inet6Address getInet6Address(NetworkInterface networkInterface) {
if(networkInterface != null) {
Enumeration<InetAddress> NICAddresses = networkInterface.getInetAddresses();
while(NICAddresses.hasMoreElements()) {
InetAddress address = NICAddresses.nextElement();
if(address instanceof Inet6Address)
return (Inet6Address)address;
}
}
return null;
}
private static NetworkInterface getNonLoopbackNetworkInterface() throws SocketException {
// We need to iterate over all NIC's machine has because stupid ubuntu does not assign
// MAC address to default loopback interface...
Enumeration<NetworkInterface> b = NetworkInterface.getNetworkInterfaces();
while(b.hasMoreElements()) {
NetworkInterface networkInterface = b.nextElement();
Enumeration<InetAddress> inetAddresses = networkInterface.getInetAddresses();
while(inetAddresses.hasMoreElements()) {
InetAddress address = inetAddresses.nextElement();
if(!address.isLoopbackAddress())
return networkInterface;
}
}
// Means we haven't found any non loopback interfaces. Bummer, return empty handed.
return null;
}
}
The following is printed on my machine:
MAC: 00-1C-C0-F2-BA-89
HOSTNAME: maxim-desktop
IP: 192.168.20.20
HOSTNAME ipv6: fe80:0:0:0:21c:c0ff:fef2:ba89%2
IP ipv6: fe80:0:0:0:21c:c0ff:fef2:ba89%2
- As you can see the hostname output for IPv4 & IPv6 are not the same, I wonder why should it be like this?
- Also, what is the meaning of the
%2that get's attached to ipv6 related queries - Is it a bug in my code or a JVM / Linux kernel issue?
Thank you,
Maxim.If you look at the code, here's what it does:
- find a non-loopback network interface (ie. in your case, eth0)
- query for the IP address of that interface (in your case, 192.168.20.20 or fe80:0:0:0:21c:c0ff:fef2:ba89%2)
- resolve the IP address. As you can see from your
hostsfile, 192.168.20.20 correctly resolves tomaxim-desktop, but there is no hostname corresponding to your IPv6 address.
IPv6 addresses beginning with
fe80(or, to be precise, addresses in thefe80::/10network) are link-local addresses, and that%2denotes which network interface the system should use.
加载中,请稍侯......
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