RFR 8024253: ThreadLocal random can use SecureRandom for the initial seed

[Doug Lea]

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()));
     }