summaryrefslogtreecommitdiffstats
path: root/cmd/zgenhostid/zgenhostid.c
blob: 5a9bdad7c38d5fa80c3a9be57d52842a37f80607 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
/*
 * 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 http://www.opensolaris.org/os/licensing.
 * 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 void usage(void);

static 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);
	/* NOTREACHED */
}

int
main(int argc, char **argv)
{
	/* default file path, can be optionally set by user */
	char path[PATH_MAX] = "/etc/hostid";
	/* holds converted user input or lrand48() generated value */
	unsigned long input_i = 0;

	int opt;
	int pathlen;
	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':
			pathlen = snprintf(path, sizeof (path), "%s", optarg);
			if (pathlen >= sizeof (path)) {
				fprintf(stderr, "%s\n", strerror(EOVERFLOW));
				exit(EXIT_FAILURE);
			} else if (pathlen < 1) {
				fprintf(stderr, "%s\n", strerror(EINVAL));
				exit(EXIT_FAILURE);
			}
			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);
}