| 1 | /* |
| 2 | * magic.c - PPP Magic Number routines. |
| 3 | * |
| 4 | * Copyright (c) 1989 Carnegie Mellon University. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms are permitted |
| 8 | * provided that the above copyright notice and this paragraph are |
| 9 | * duplicated in all such forms and that any documentation, |
| 10 | * advertising materials, and other materials related to such |
| 11 | * distribution and use acknowledge that the software was developed |
| 12 | * by Carnegie Mellon University. The name of the |
| 13 | * University may not be used to endorse or promote products derived |
| 14 | * from this software without specific prior written permission. |
| 15 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR |
| 16 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED |
| 17 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. |
| 18 | */ |
| 19 | |
| 20 | #ifndef lint |
| 21 | static char rcsid[] = "$Id: magic.c,v 1.1 1993/11/11 03:54:25 paulus Exp $"; |
| 22 | #endif |
| 23 | |
| 24 | #include <stdio.h> |
| 25 | #include <sys/types.h> |
| 26 | #include <sys/time.h> |
| 27 | |
| 28 | #include "magic.h" |
| 29 | |
| 30 | |
| 31 | static u_long next; /* Next value to return */ |
| 32 | |
| 33 | extern u_long gethostid __ARGS((void)); |
| 34 | extern long random __ARGS((void)); |
| 35 | extern void srandom __ARGS((int)); |
| 36 | |
| 37 | |
| 38 | /* |
| 39 | * magic_init - Initialize the magic number generator. |
| 40 | * |
| 41 | * Computes first magic number and seed for random number generator. |
| 42 | * Attempts to compute a random number seed which will not repeat. |
| 43 | * The current method uses the current hostid and current time. |
| 44 | */ |
| 45 | void magic_init() |
| 46 | { |
| 47 | struct timeval tv; |
| 48 | |
| 49 | next = gethostid(); |
| 50 | if (gettimeofday(&tv, NULL)) { |
| 51 | perror("gettimeofday"); |
| 52 | exit(1); |
| 53 | } |
| 54 | next ^= (u_long) tv.tv_sec ^ (u_long) tv.tv_usec; |
| 55 | |
| 56 | srandom((int) next); |
| 57 | } |
| 58 | |
| 59 | |
| 60 | /* |
| 61 | * magic - Returns the next magic number. |
| 62 | */ |
| 63 | u_long magic() |
| 64 | { |
| 65 | u_long m; |
| 66 | |
| 67 | m = next; |
| 68 | next = (u_long) random(); |
| 69 | return (m); |
| 70 | } |