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ntp 4.2.6p5

    1: /*
    2:  * Copyright (C) 2004, 2005, 2007  Internet Systems Consortium, Inc. ("ISC")
    3:  * Copyright (C) 1999-2003  Internet Software Consortium.
    4:  *
    5:  * Permission to use, copy, modify, and/or distribute this software for any
    6:  * purpose with or without fee is hereby granted, provided that the above
    7:  * copyright notice and this permission notice appear in all copies.
    8:  *
    9:  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
   10:  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
   11:  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
   12:  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
   13:  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
   14:  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
   15:  * PERFORMANCE OF THIS SOFTWARE.
   16:  */
   17: 
   18: /* $Id: random.c,v 1.1.1.1 2012/05/29 12:08:38 misho Exp $ */
   19: 
   20: /*! \file */
   21: 
   22: #include <config.h>
   23: 
   24: #include <stdlib.h>
   25: #include <time.h>		/* Required for time(). */
   26: #ifdef HAVE_SYS_TYPES_H
   27: #include <sys/types.h>
   28: #endif
   29: #ifdef HAVE_UNISTD_H
   30: #include <unistd.h>
   31: #endif
   32: 
   33: #include <isc/mutex.h>
   34: #include <isc/once.h>
   35: #include <isc/random.h>
   36: #include <isc/string.h>
   37: #include <isc/util.h>
   38: 
   39: static isc_once_t once = ISC_ONCE_INIT;
   40: 
   41: static void
   42: initialize_rand(void)
   43: {
   44: #ifndef HAVE_ARC4RANDOM
   45: 	unsigned int pid = getpid();
   46: 	
   47: 	/*
   48: 	 * The low bits of pid generally change faster.
   49: 	 * Xor them with the high bits of time which change slowly.
   50: 	 */
   51: 	pid = ((pid << 16) & 0xffff0000) | ((pid >> 16) & 0xffff);
   52: 
   53: 	srand(time(NULL) ^ pid);
   54: #endif
   55: }
   56: 
   57: static void
   58: initialize(void)
   59: {
   60: 	RUNTIME_CHECK(isc_once_do(&once, initialize_rand) == ISC_R_SUCCESS);
   61: }
   62: 
   63: void
   64: isc_random_seed(isc_uint32_t seed)
   65: {
   66: 	initialize();
   67: 
   68: #ifndef HAVE_ARC4RANDOM
   69: 	srand(seed);
   70: #else
   71: 	arc4random_addrandom((u_char *) &seed, sizeof(isc_uint32_t));
   72: #endif
   73: }
   74: 
   75: void
   76: isc_random_get(isc_uint32_t *val)
   77: {
   78: 	REQUIRE(val != NULL);
   79: 
   80: 	initialize();
   81: 
   82: #ifndef HAVE_ARC4RANDOM
   83: 	/*
   84: 	 * rand()'s lower bits are not random.
   85: 	 * rand()'s upper bit is zero.
   86: 	 */
   87: 	*val = ((rand() >> 4) & 0xffff) | ((rand() << 12) & 0xffff0000);
   88: #else
   89: 	*val = arc4random();
   90: #endif
   91: }
   92: 
   93: isc_uint32_t
   94: isc_random_jitter(isc_uint32_t max, isc_uint32_t jitter) {
   95: 	REQUIRE(jitter < max);
   96: 	if (jitter == 0)
   97: 		return (max);
   98: 	else
   99: #ifndef HAVE_ARC4RANDOM
  100: 		return (max - rand() % jitter);
  101: #else
  102: 		return (max - arc4random() % jitter);
  103: #endif
  104: }