On 09/16/2013 11:39 AM, Chris Hegarty wrote:
On some platforms, Windows, tunneling interfaces report a very "bad" mac
address, e.g. 00-00-00-00-00-00-00-E0. I wonder if it is worth skipping all
isVirtual() nifs?
Good idea. This makes it impossible to also take advantage of Guy's
de-uglification though. Leaving the following.
(This might stand as a record for the most expert attention
spent on the least important issue ever in JDK :-)! Recall that
the motivation is solely to act as a tie-breaker in the
incredibly unlikely scenario of a cluster of communicating
hosts all starting at the same time.)
private static long initialSeed() {
String pp = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction(
"java.util.secureRandomSeed"));
if (pp != null && pp.equalsIgnoreCase("true")) {
byte[] seedBytes = java.security.SecureRandom.getSeed(8);
long s = (long)(seedBytes[0]) & 0xffL;
for (int i = 1; i < 8; ++i)
s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
return s;
}
long h = 0L;
try {
Enumeration<NetworkInterface> ifcs =
NetworkInterface.getNetworkInterfaces();
boolean retry = false; // retry once if getHardwareAddress is null
while (ifcs.hasMoreElements()) {
NetworkInterface ifc = ifcs.nextElement();
if (!ifc.isVirtual()) { // skip fake addresses
byte[] bs = ifc.getHardwareAddress();
if (bs != null) {
for (int i = 0; i < 8 && i < bs.length; ++i)
h = (h << 8) ^ bs[i];
break;
}
else if (!retry)
retry = true;
else
break;
}
}
} catch (Exception ignore) {
}
return (mix64(h ^ System.currentTimeMillis()) ^
mix64(System.nanoTime()));
}
