[src/trunk]: src/sys/net use cprng_fast instead of getmicrouptime to generate...

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/4cc1a12c860c
branches:  trunk
changeset: 784436:4cc1a12c860c
user:      yamt <yamt%NetBSD.org@localhost>
date:      Mon Jan 28 15:05:03 2013 +0000

description:
use cprng_fast instead of getmicrouptime to generate "random" mac address
because the latter often produces the same addresses for subsequent tap
instances.

diffstat:

 sys/net/if_tap.c |  15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)

diffs (51 lines):

diff -r a81679ebab10 -r 4cc1a12c860c sys/net/if_tap.c
--- a/sys/net/if_tap.c  Mon Jan 28 15:01:13 2013 +0000
+++ b/sys/net/if_tap.c  Mon Jan 28 15:05:03 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_tap.c,v 1.69 2013/01/28 15:01:13 yamt Exp $ */
+/*     $NetBSD: if_tap.c,v 1.70 2013/01/28 15:05:03 yamt Exp $ */
 
 /*
  *  Copyright (c) 2003, 2004, 2008, 2009 The NetBSD Foundation.
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_tap.c,v 1.69 2013/01/28 15:01:13 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_tap.c,v 1.70 2013/01/28 15:05:03 yamt Exp $");
 
 #if defined(_KERNEL_OPT)
 
@@ -46,6 +46,7 @@
 #include <sys/kernel.h>
 #include <sys/malloc.h>
 #include <sys/conf.h>
+#include <sys/cprng.h>
 #include <sys/device.h>
 #include <sys/file.h>
 #include <sys/filedesc.h>
@@ -265,8 +266,6 @@
        uint8_t enaddr[ETHER_ADDR_LEN] =
            { 0xf2, 0x0b, 0xa4, 0xff, 0xff, 0xff };
        char enaddrstr[3 * ETHER_ADDR_LEN];
-       struct timeval tv;
-       uint32_t ui;
 
        sc->sc_dev = self;
        sc->sc_sih = softint_establish(SOFTINT_CLOCK, tap_softintr, sc);
@@ -278,12 +277,10 @@
 
        /*
         * In order to obtain unique initial Ethernet address on a host,
-        * do some randomisation using the current uptime.  It's not meant
-        * for anything but avoiding hard-coding an address.
+        * do some randomisation.  It's not meant for anything but avoiding
+        * hard-coding an address.
         */
-       getmicrouptime(&tv);
-       ui = (tv.tv_sec ^ tv.tv_usec) & 0xffffff;
-       memcpy(enaddr+3, (uint8_t *)&ui, 3);
+       cprng_fast(&enaddr[3], 3);
 
        aprint_verbose_dev(self, "Ethernet address %s\n",
            ether_snprintf(enaddrstr, sizeof(enaddrstr), enaddr));