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 http://www.opensolaris.org/os/licensing.
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  * Copyright (c) 2017, Lawrence Livermore National Security, LLC.
23  */
24 
25 #include <fcntl.h>
26 #include <stdlib.h>
27 #include <stdio.h>
28 #include <sys/types.h>
29 #include <sys/stat.h>
30 #include <sys/systeminfo.h>
31 
32 static unsigned long
33 get_spl_hostid(void)
34 {
35 	FILE *f;
36 	unsigned long hostid;
37 	char *env;
38 
39 	/*
40 	 * Allow the hostid to be subverted for testing.
41 	 */
42 	env = getenv("ZFS_HOSTID");
43 	if (env)
44 		return (strtoull(env, NULL, 0));
45 
46 	f = fopen("/proc/sys/kernel/spl/hostid", "re");
47 	if (!f)
48 		return (0);
49 
50 	if (fscanf(f, "%lx", &hostid) != 1)
51 		hostid = 0;
52 
53 	fclose(f);
54 
55 	return (hostid);
56 }
57 
58 unsigned long
59 get_system_hostid(void)
60 {
61 	unsigned long hostid = get_spl_hostid();
62 
63 	/*
64 	 * We do not use gethostid(3) because it can return a bogus ID,
65 	 * depending on the libc and /etc/hostid presence,
66 	 * and the kernel and userspace must agree.
67 	 * See comments above hostid_read() in the SPL.
68 	 */
69 	if (hostid == 0) {
70 		int fd = open("/etc/hostid", O_RDONLY | O_CLOEXEC);
71 		if (fd >= 0) {
72 			if (read(fd, &hostid, 4) < 0)
73 				hostid = 0;
74 			(void) close(fd);
75 		}
76 	}
77 
78 	return (hostid & HOSTID_MASK);
79 }
80