lib/libspl/os/linux/gethostid.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  * 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         uint32_t system_hostid;
  63
  64         /*
  65          * We do not use gethostid(3) because it can return a bogus ID,
  66          * depending on the libc and /etc/hostid presence,
  67          * and the kernel and userspace must agree.
  68          * See comments above hostid_read() in the SPL.
  69          */
  70         if (hostid == 0) {
  71                 int fd = open("/etc/hostid", O_RDONLY | O_CLOEXEC);
  72                 if (fd >= 0) {
  73                         if (read(fd, &system_hostid, sizeof (system_hostid))
  74                             != sizeof (system_hostid))
  75                                 hostid = 0;
  76                         else
  77                                 hostid = system_hostid;
  78                         (void) close(fd);
  79                 }
  80         }
  81
  82         return (hostid & HOSTID_MASK);
  83 }