magic.c

uClinux上的ppp拨号驱动及测试程序

/*
 * magic.c - PPP Magic Number routines.
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>

#include "magic.h"

#ifndef linux
static u_int32_t next;		/* Next value to return */
#else
#include <sys/stat.h>
#include <fcntl.h>

/* on Linux we use /dev/urandom as random numbers source 
   I find it really cool :) */
int rfd = 0;	/* /dev/urandom */
#endif

/*
 * magic_init - Initialize the magic number generator.
 *
 * Attempts to compute a random number seed which will not repeat.
 * The current method uses the current hostid, current process ID
 * and current time, currently.
 */
void
magic_init()
{
    long seed;
    struct timeval t;

#ifdef linux
	rfd = open("/dev/urandom", O_RDONLY);
	if(rfd != -1) 
			return;
	else {
		rfd = 0;
#endif
	/* if /dev/urandom fails, we try traditional method */
    gettimeofday(&t, NULL);
    seed = gethostid() ^ t.tv_sec ^ t.tv_usec ^ getpid();
    srand48(seed);
#ifdef linux
	}
#endif
}

/*
 * magic - Returns the next magic number.
 */
u_int32_t
magic()
{
#ifdef linux
	u_int32_t ret = 0;

	if(rfd) 
	{
		read(rfd, &ret, sizeof(ret));
		return(ret);
	}
	else
    	return (u_int32_t) mrand48();
#else
    return (u_int32_t) mrand48();
#endif
}

#ifdef NO_DRAND48
/*
 * Substitute procedures for those systems which don't have
 * drand48 et al.
 */

double
drand48()
{
    return (double)random() / (double)0x7fffffffL; /* 2**31-1 */
}

long
mrand48()
{
    return random();
}

void
srand48(seedval)
long seedval;
{
    srandom((int)seedval);
}

#endif