FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/cmd/zgenhostid.c

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    
    /*
     * Copyright (c) 2020, Georgy Yakovlev.  All rights reserved.
     */
    
    #include <errno.h>
    #include <fcntl.h>
    #include <getopt.h>
    #include <inttypes.h>
    #include <limits.h>
    #include <stdint.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <sys/stat.h>
    #include <time.h>
    #include <unistd.h>
    
    static __attribute__((noreturn)) void
    usage(void)
    {
            (void) fprintf(stderr,
                "usage: zgenhostid [-fh] [-o path] [value]\n\n"
                "  -f\t\t force hostid file write\n"
                "  -h\t\t print this usage and exit\n"
                "  -o <filename>\t write hostid to this file\n\n"
                "If hostid file is not present, store a hostid in it.\n"
                "The optional value should be an 8-digit hex number between"
                " 1 and 2^32-1.\n"
                "If the value is 0 or no value is provided, a random one"
                " will be generated.\n"
                "The value must be unique among your systems.\n");
            exit(EXIT_FAILURE);
    }
    
    int
    main(int argc, char **argv)
    {
            /* default file path, can be optionally set by user */
            const char *path = "/etc/hostid";
            /* holds converted user input or lrand48() generated value */
            unsigned long input_i = 0;
    
            int opt;
            int force_fwrite = 0;
            while ((opt = getopt_long(argc, argv, "fo:h?", 0, 0)) != -1) {
                    switch (opt) {
                    case 'f':
                            force_fwrite = 1;
                            break;
                    case 'o':
                            path = optarg;
                            break;
                    case 'h':
                    case '?':
                            usage();
                    }
            }
    
            char *in_s = argv[optind];
            if (in_s != NULL) {
                    /* increment pointer by 2 if string is 0x prefixed */
                    if (strncasecmp("0x", in_s, 2) == 0) {
                            in_s += 2;
                    }
    
                    /* need to be exactly 8 characters */
                    const char *hex = "0123456789abcdefABCDEF";
                    if (strlen(in_s) != 8 || strspn(in_s, hex) != 8) {
                            fprintf(stderr, "%s\n", strerror(ERANGE));
                            usage();
                    }
    
                    input_i = strtoul(in_s, NULL, 16);
                    if (errno != 0) {
                            perror("strtoul");
                            exit(EXIT_FAILURE);
                    }
    
                   if (input_i > UINT32_MAX) {
                           fprintf(stderr, "%s\n", strerror(ERANGE));
                           usage();
                   }
           }
   
           struct stat fstat;
           if (force_fwrite == 0 && stat(path, &fstat) == 0 &&
               S_ISREG(fstat.st_mode)) {
                   fprintf(stderr, "%s: %s\n", path, strerror(EEXIST));
                   exit(EXIT_FAILURE);
           }
   
           /*
            * generate if not provided by user
            * also handle unlikely zero return from lrand48()
            */
           while (input_i == 0) {
                   srand48(getpid() ^ time(NULL));
                   input_i = lrand48();
           }
   
           FILE *fp = fopen(path, "wb");
           if (!fp) {
                   perror("fopen");
                   exit(EXIT_FAILURE);
           }
   
           /*
            * we need just 4 bytes in native endianness
            * not using sethostid() because it may be missing or just a stub
            */
           uint32_t hostid = input_i;
           int written = fwrite(&hostid, 1, 4, fp);
           if (written != 4) {
                   perror("fwrite");
                   exit(EXIT_FAILURE);
           }
   
           fclose(fp);
           exit(EXIT_SUCCESS);
   }

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