cmd/zgenhostid.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or https://opensource.org/licenses/CDDL-1.0.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 2020, Georgy Yakovlev.  All rights reserved.
  24  */
  25
  26 #include <errno.h>
  27 #include <fcntl.h>
  28 #include <getopt.h>
  29 #include <inttypes.h>
  30 #include <limits.h>
  31 #include <stdint.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <sys/stat.h>
  36 #include <time.h>
  37 #include <unistd.h>
  38
  39 static __attribute__((noreturn)) void
  40 usage(void)
  41 {
  42         (void) fprintf(stderr,
  43             "usage: zgenhostid [-fh] [-o path] [value]\n\n"
  44             "  -f\t\t force hostid file write\n"
  45             "  -h\t\t print this usage and exit\n"
  46             "  -o <filename>\t write hostid to this file\n\n"
  47             "If hostid file is not present, store a hostid in it.\n"
  48             "The optional value should be an 8-digit hex number between"
  49             " 1 and 2^32-1.\n"
  50             "If the value is 0 or no value is provided, a random one"
  51             " will be generated.\n"
  52             "The value must be unique among your systems.\n");
  53         exit(EXIT_FAILURE);
  54 }
  55
  56 int
  57 main(int argc, char **argv)
  58 {
  59         /* default file path, can be optionally set by user */
  60         const char *path = "/etc/hostid";
  61         /* holds converted user input or lrand48() generated value */
  62         unsigned long input_i = 0;
  63
  64         int opt;
  65         int force_fwrite = 0;
  66         while ((opt = getopt_long(argc, argv, "fo:h?", 0, 0)) != -1) {
  67                 switch (opt) {
  68                 case 'f':
  69                         force_fwrite = 1;
  70                         break;
  71                 case 'o':
  72                         path = optarg;
  73                         break;
  74                 case 'h':
  75                 case '?':
  76                         usage();
  77                 }
  78         }
  79
  80         char *in_s = argv[optind];
  81         if (in_s != NULL) {
  82                 /* increment pointer by 2 if string is 0x prefixed */
  83                 if (strncasecmp("0x", in_s, 2) == 0) {
  84                         in_s += 2;
  85                 }
  86
  87                 /* need to be exactly 8 characters */
  88                 const char *hex = "0123456789abcdefABCDEF";
  89                 if (strlen(in_s) != 8 || strspn(in_s, hex) != 8) {
  90                         fprintf(stderr, "%s\n", strerror(ERANGE));
  91                         usage();
  92                 }
  93
  94                 input_i = strtoul(in_s, NULL, 16);
  95                 if (errno != 0) {
  96                         perror("strtoul");
  97                         exit(EXIT_FAILURE);
  98                 }
  99
 100                 if (input_i > UINT32_MAX) {
 101                         fprintf(stderr, "%s\n", strerror(ERANGE));
 102                         usage();
 103                 }
 104         }
 105
 106         struct stat fstat;
 107         if (force_fwrite == 0 && stat(path, &fstat) == 0 &&
 108             S_ISREG(fstat.st_mode)) {
 109                 fprintf(stderr, "%s: %s\n", path, strerror(EEXIST));
 110                 exit(EXIT_FAILURE);
 111         }
 112
 113         /*
 114          * generate if not provided by user
 115          * also handle unlikely zero return from lrand48()
 116          */
 117         while (input_i == 0) {
 118                 srand48(getpid() ^ time(NULL));
 119                 input_i = lrand48();
 120         }
 121
 122         FILE *fp = fopen(path, "wb");
 123         if (!fp) {
 124                 perror("fopen");
 125                 exit(EXIT_FAILURE);
 126         }
 127
 128         /*
 129          * we need just 4 bytes in native endianness
 130          * not using sethostid() because it may be missing or just a stub
 131          */
 132         uint32_t hostid = input_i;
 133         int written = fwrite(&hostid, 1, 4, fp);
 134         if (written != 4) {
 135                 perror("fwrite");
 136                 exit(EXIT_FAILURE);
 137         }
 138
 139         fclose(fp);
 140         exit(EXIT_SUCCESS);
 141 }