我的机器上有三个接口(eth0,Loopback,wlan0)，我想使用Java-API来获取mac地址。
Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
for (NetworkInterface netint : Collections.list(nets))
displayInterfaceInformation(netint);
}
static void displayInterfaceInformation(NetworkInterface netint)
throws SocketException
{
System.out.println("Display name: "
+ netint.getDisplayName());
System.out.println("Hardware address: "
+ Arrays.toString(netint.getHardwareAddress()));
}
wlan0,loopback，但错过了eth0 。 更新
strace -f java Networks 2>&1| grep ioctl).. 空白(空)。 java -version Java版本“1.7.0_21”
Java(TM)SE运行时环境(内部版本1.7.0_21-b11)
Java HotSpot(TM)64位服务器VM(内部版本23.21-b01，混合模式)
ioctl(4, SIOCGIFCONF, {80, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"wlan0", {AF_INET, inet_addr("192.168.1.101")}}}}) = 0
ioctl(5, SIOCGIFFLAGS, {ifr_name="eth0", ifr_flags=IFF_UP|IFF_BROADCAST|IFF_MULTICAST}) = 0
ioctl(5, SIOCGIFHWADDR, {ifr_name="eth0", ifr_hwaddr=-----------------}) = 0
ioctl(5, SIOCGIFMETRIC, {ifr_name="eth0", ifr_metric=0}) = 0
ioctl(5, SIOCGIFMTU, {ifr_name="eth0", ifr_mtu=1500}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="eth0", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="eth0", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFTXQLEN, {ifr_name="eth0", ifr_qlen=1000}) = 0
ioctl(4, SIOCGIFADDR, {ifr_name="eth0", ???}) = -1 EADDRNOTAVAIL (Cannot assign requested address)
ioctl(5, SIOCGIFFLAGS, {ifr_name="lo", ifr_flags=IFF_UP|IFF_LOOPBACK|IFF_RUNNING}) = 0
ioctl(5, SIOCGIFHWADDR, {ifr_name="lo", ifr_hwaddr=00:00:00:00:00:00}) = 0
ioctl(5, SIOCGIFMETRIC, {ifr_name="lo", ifr_metric=0}) = 0
ioctl(5, SIOCGIFMTU, {ifr_name="lo", ifr_mtu=16436}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="lo", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="lo", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFTXQLEN, {ifr_name="lo", ifr_qlen=0}) = 0
ioctl(4, SIOCGIFADDR, {ifr_name="lo", ifr_addr={AF_INET, inet_addr("127.0.0.1")}}) = 0
ioctl(4, SIOCGIFDSTADDR, {ifr_name="lo", ifr_dstaddr={AF_INET, inet_addr("127.0.0.1")}}) = 0
ioctl(4, SIOCGIFBRDADDR, {ifr_name="lo", ifr_broadaddr={AF_INET, inet_addr("0.0.0.0")}}) = 0
ioctl(4, SIOCGIFNETMASK, {ifr_name="lo", ifr_netmask={AF_INET, inet_addr("255.0.0.0")}}) = 0
ioctl(5, SIOCGIFFLAGS, {ifr_name="wlan0", ifr_flags=IFF_UP|IFF_BROADCAST|IFF_RUNNING|IFF_MULTICAST}) = 0
ioctl(5, SIOCGIFHWADDR, {ifr_name="wlan0", ifr_hwaddr=---------------}) = 0
ioctl(5, SIOCGIFMETRIC, {ifr_name="wlan0", ifr_metric=0}) = 0
ioctl(5, SIOCGIFMTU, {ifr_name="wlan0", ifr_mtu=1500}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="wlan0", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFMAP, {ifr_name="wlan0", ifr_map={mem_start=0, mem_end=0, base_addr=0, irq=0, dma=0, port=0}}) = 0
ioctl(5, SIOCGIFTXQLEN, {ifr_name="wlan0", ifr_qlen=1000}) = 0
ioctl(4, SIOCGIFADDR, {ifr_name="wlan0", ifr_addr={AF_INET, inet_addr("192.168.1.101")}}) = 0
ioctl(4, SIOCGIFDSTADDR, {ifr_name="wlan0", ifr_dstaddr={AF_INET, inet_addr("192.168.1.101")}}) = 0
ioctl(4, SIOCGIFBRDADDR, {ifr_name="wlan0", ifr_broadaddr={AF_INET, inet_addr("192.168.1.255")}}) = 0
ioctl(4, SIOCGIFNETMASK, {ifr_name="wlan0", ifr_netmask={AF_INET, inet_addr("255.255.255.0")}}) = 0
ifconfig
$ ifconfig
eth0 Link encap:Ethernet HWaddr -------------
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
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:1695 errors:0 dropped:0 overruns:0 frame:0
TX packets:1695 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:129949 (129.9 KB) TX bytes:129949 (129.9 KB)
wlan0 Link encap:Ethernet HWaddr -------------------
inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::-------------- Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8396 errors:0 dropped:0 overruns:0 frame:0
TX packets:5524 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3959941 (3.9 MB) TX bytes:1513934 (1.5 MB)
参考方案
显然，我一开始就错了:即使ifconfig和Java API都在使用
相同的ioctl()系统调用，它们的行为会有所不同。
首先，SIOCGIFCONF ioctl()记录如下(请参阅http://linux.die.net/man/7/netdevice):
SIOCGIFCONF
Return a list of interface (transport layer) addresses.
...
The kernel fills the ifreqs with all current L3 interface
addresses that are running.
So, the SIOCGIFCONF ioctl() which is used by both ifconfig and the JAVA API only returns the running interfaces. This can also be seen in the strace ifconfig ... output from the question - the very first ioctl only returns lo and wlan0, but not eth0.
Then, where does ifconfig get the eth0 from at all? Checking the ifconfig source code (from the net-tools package on Debian/Ubuntu), we see
that ifconfig is not using the result from the ioctl() as the basis for the network device enumeration,
but first of all reads the /proc filesystem to determine all network interfaces. Then, it uses the ioctl() syscalls to determine further information about each interface.
Unfortunately, the java.net.NetworkInterface.getByName() method does not even return a network interface object
for an unconfigured interface if we explicitly pass the name, like eth0.
Essentially, there remain three different approaches to get the hardware addresses of all devices on Linux:
- Call
ifconfigand parse the output (should be last resort) - Implement a JNI library to do the same what
ifconfigdoes (requires an architecture dependent shared library) - Read the data directly from the
/procand the/sysfilesystems.
All of these approaches are system dependant and not portable. The benefit of the third approach is that it can be
implemented in pure Java. The following is a sample implementation of the third approach which worked well in my environment:
static void printHardwareAddresses() throws SocketException {
if (System.getProperty("os.name").equals("Linux")) {
// Read all available device names
List<String> devices = new ArrayList<>();
Pattern pattern = Pattern.compile("^ *(.*):");
try (FileReader reader = new FileReader("/proc/net/dev")) {
BufferedReader in = new BufferedReader(reader);
String line = null;
while( (line = in.readLine()) != null) {
Matcher m = pattern.matcher(line);
if (m.find()) {
devices.add(m.group(1));
}
}
} catch (IOException e) {
e.printStackTrace();
}
// read the hardware address for each device
for (String device : devices) {
try (FileReader reader = new FileReader("/sys/class/net/" + device + "/address")) {
BufferedReader in = new BufferedReader(reader);
String addr = in.readLine();
System.out.println(String.format("%5s: %s", device, addr));
} catch (IOException e) {
e.printStackTrace();
}
}
} else {
// use standard API for Windows & Others (need to test on each platform, though!!)
...
}
}
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