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/* magic.c - PPP Magic Number routines.
*
* Copyright (C) 1989 Carnegie Mellon University.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program - see the file COPYING.
*
* See `CHANGES' file for revision history.
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "magic.h"
static int rfd = -1; /* fd for /dev/urandom */
static int magic_inited = 0;
/*
* 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()
{
struct stat statbuf;
long seed;
struct timeval t;
if (magic_inited)
return;
magic_inited = 1;
/*
try using /dev/urandom
also check that it's a character device
If it doesn't exist, fallback to other method
*/
if (!lstat("/dev/urandom", &statbuf) && S_ISCHR(statbuf.st_mode)) {
rfd = open("/dev/urandom", O_RDONLY);
if (rfd >= 0)
return;
}
gettimeofday(&t, NULL);
seed = gethostid() ^ t.tv_sec ^ t.tv_usec ^ getpid();
srandom(seed);
}
/*
* magic - Returns the next magic number.
*/
u_int32_t
magic()
{
magic_init();
if(rfd > -1) {
u_int32_t ret;
int nb_read = read(rfd, &ret, sizeof(ret));
close(rfd);
if (nb_read < sizeof(ret)) {
/* on read() error fallback to other method */
return (u_int32_t)random();
}
return ret;
}
return (u_int32_t)random();
}
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