UUIDGenerator broken on Windows...

[clebert.suconic]

public final UUID generateTimeBasedUUID(byte[] byteAddr)
 {
 byte[] contents = new byte[16];
 int pos = 12;
 for (int i = 0; i < 4; ++i)
 {
 contents[pos + i] = byteAddr; <<-- NPE on byteAddr
 }

It only happens on Windows.

byteAddr is null.

[timfox]

Can you show a complete test case?

[clebert.suconic]

Actually.. It is ArrayIndexOutOfBoundException...

getHardwareAddress is returning a byte[0];

[timfox]

The only way that could possibly fail is if the byte[] byteAddr was less than 16

[clebert.suconic]

"timfox" wrote:
Can you show a complete test case?

I" m just running UUIDTest on Windows.

[timfox]

Ok, so this is a bug in Jeff's network address code. It should never return a zero length byte[]

[clebert.suconic]

"timfox" wrote:
The only way that could possibly fail is if the byte[] byteAddr was less than 16

Yep... and it is returning byteArray[0] on my Windows.

[timfox]

Guess... you could probably fix this by checking for zero length byte[] in getHardwareAddress() and returning null.

[timfox]

BTW - are you running in a security manager?

If not, then I am surprised getNetworkInterfaces() doesn't return any real interfaces.... that might point to a real bug, or issue in the Windows implementation of said function.

[clebert.suconic]

No SecurityManager.. I'm just running the test inside Eclipse on Windows.


I've added some hacking around getHardwareAddress, to discard anything that had address.length == 0.

My windows returned an address with 6 bytes then. At that point I got an outOfMemoryError, while calilng UUID.toString. (i.e. the code was in loop)


Then I rejected everything that had length != 16... it eventually returned null, and I got the infinite loop throwing an OME again.

[clebert.suconic]

i.e. There is an issue on the Windows implementation.

[clebert.suconic]

Actually, I made the test to pass, by changing the method as this:

public final static byte[] getHardwareAddress()
 {
 Method getHardwareAddressMethod;
 try
 {
 getHardwareAddressMethod = NetworkInterface.class.getMethod("getHardwareAddress", null);
 }
 catch (Throwable t)
 {
 // not on Java 6 or not enough security permission
 return null;
 }

 try
 {
 Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
 while (networkInterfaces.hasMoreElements())
 {
 NetworkInterface networkInterface = (NetworkInterface)networkInterfaces.nextElement();
 Object res = getHardwareAddressMethod.invoke(networkInterface, null);
 if (res instanceof byte[])
 {
 byte[] address = (byte[])res;
 if (address.length == 16)
 {
 if (log.isDebugEnabled())
 {
 log.debug("using hardware address " + asString(address));
 }
 return address;
 }
 }
 }
 }
 catch (Throwable t)
 {
 }

 return null;
 }

But this is aways returning null on windows.

But I still have an OME on timing.UUIDTest, but it is not caused by an infinite loop as I though.

[clebert.suconic]

"timfox" wrote:
Guess... you could probably fix this by checking for zero length byte[] in getHardwareAddress() and returning null.

Just saw this post...

yes, This is how I fixed it (see my previous post).. but I will let Jeff decide if it should be committed or if he can think of another way of fixing it.

[timfox]

aha. my guess is you're using ipv6 so the address returned is not length 16!

[jmesnil]

in UUIDGenerator.generateTimeBasedUUID, we use only the 1st 4 bytes of the address so that it works with IPv4 (4 bytes), IPv4 (16 bytes) and MAC (6 bytes).

The check on getHardwareAddress should be (address.length >= 4) so that we can safely use the byte array.

However, I'm surprised that Windows returns a 0-sized array.

Clebert, could you run this code on Java *6* on Windows to check what it returns:

public static void main(String[] args) throws SocketException
 {

 Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
 while (networkInterfaces.hasMoreElements())
 {
 NetworkInterface networkInterface = (NetworkInterface)networkInterfaces.nextElement();
 byte[] hardwareAddress = networkInterface.getHardwareAddress();
 if (hardwareAddress == null)
 {
 System.out.println(networkInterface.getDisplayName() + ":null");
 } else
 {
 String s = "";
 for (int i = 0; i < hardwareAddress.length - 1; i++)
 {
 s += Integer.toHexString(hardwareAddress) + ":";
 }
 s += hardwareAddress[hardwareAddress.length - 1];
 System.out.println(networkInterface.getDisplayName() + ":" + s);
 }
 }
 }