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

[Doug Lea]

On 09/16/2013 08:46 AM, Peter Levart wrote:

What worries me is that InetAddress.getLocalHost() involves name
service look-up. It depends on configuration, but on my computer, it takes about
5s to evaluate the hostname -> IP mapping the first time the program is run.

NetworkInterface also has one method called getHardwareAddress(). This might me
interesting too...

Using NetworkInterface.getHardwareAddress() is a good idea; thanks!
Using only one of them should suffice. And just giving up on
SecurityException seems fine.

Could you check that this performs reasonably on your
unusually-configured machine?

 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();
            if (ifcs.hasMoreElements()) {
                byte[] bs = ifcs.nextElement().getHardwareAddress();
                if (bs != null) {
                    for (int i = 0; i < 8 && i < bs.length; ++i)
                        h = (h << 8) ^ bs[i];
                }
            }
        } catch (Exception ignore) {
        }
        return (mix64(h ^ System.currentTimeMillis()) ^
                mix64(System.nanoTime()));