lib/sethostname.c

   1 /* sethostname emulation for glibc compliance.
   2
   3    Copyright (C) 2011-2019 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Ben Walton <bwalton@artsci.utoronto.ca> */
  19
  20 #include <config.h>
  21
  22 #if !(defined _WIN32 || defined __CYGWIN__)
  23 /* Unix API.  */
  24
  25 /* Specification.  */
  26 #include <unistd.h>
  27
  28 #include <errno.h>
  29 #include <stdio.h>
  30 #include <limits.h>
  31
  32 /* Set up to LEN chars of NAME as system hostname.
  33    Return 0 if ok, set errno and return -1 on error. */
  34
  35 int
  36 sethostname (const char *name, size_t len)
  37 {
  38   /* Ensure the string isn't too long.  glibc does allow setting an
  39      empty hostname so no point in enforcing a lower bound. */
  40   if (len > HOST_NAME_MAX)
  41     {
  42       errno = EINVAL;
  43       return -1;
  44     }
  45
  46 #ifdef __minix /* Minix */
  47   {
  48     FILE *hostf;
  49     int r = 0;
  50
  51     /* glibc returns EFAULT, EINVAL, and EPERM on error.  None of
  52        these are appropriate for us to set, even if they may match the
  53        situation, during failed open/write/close operations, so we
  54        leave errno alone and rely on what the system sets up. */
  55     hostf = fopen ("/etc/hostname.file", "w");
  56     if (hostf == NULL)
  57       r = -1;
  58     else
  59       {
  60         fprintf (hostf, "%.*s\n", (int) len, name);
  61         if (ferror (hostf))
  62           {
  63             /* Close hostf, preserving the errno from the fprintf call.  */
  64             int saved_errno = errno;
  65             fclose (hostf);
  66             errno = saved_errno;
  67             r = -1;
  68           }
  69         else
  70           {
  71             if (fclose (hostf))
  72               /* fclose sets errno on failure.  */
  73               r = -1;
  74           }
  75       }
  76
  77     return r;
  78   }
  79 #else
  80   /* For platforms that we don't have a better option for, simply bail
  81      out.  */
  82   errno = ENOSYS;
  83   return -1;
  84 #endif
  85 }
  86
  87 #else
  88 /* Native Windows API.  Also used on Cygwin.  */
  89
  90 /* Ensure that <windows.h> declares SetComputerNameEx.  */
  91 #undef _WIN32_WINNT
  92 #define _WIN32_WINNT _WIN32_WINNT_WIN2K
  93
  94 #define WIN32_LEAN_AND_MEAN
  95
  96 /* Specification.  */
  97 #include <unistd.h>
  98
  99 #include <errno.h>
 100 #include <limits.h>
 101 #include <string.h>
 102
 103 #include <windows.h>
 104 /* The mingw header files don't define GetComputerNameEx, SetComputerNameEx.  */
 105 #ifndef GetComputerNameEx
 106 # define GetComputerNameEx GetComputerNameExA
 107 #endif
 108 #ifndef SetComputerNameEx
 109 # define SetComputerNameEx SetComputerNameExA
 110 #endif
 111
 112 /* Set up to LEN chars of NAME as system hostname.
 113    Return 0 if ok, set errno and return -1 on error. */
 114
 115 int
 116 sethostname (const char *name, size_t len)
 117 {
 118   char name_asciz[HOST_NAME_MAX + 1];
 119   char old_name[HOST_NAME_MAX + 1];
 120   DWORD old_name_len;
 121
 122   /* Ensure the string isn't too long.  glibc does allow setting an
 123      empty hostname so no point in enforcing a lower bound. */
 124   if (len > HOST_NAME_MAX)
 125     {
 126       errno = EINVAL;
 127       return -1;
 128     }
 129
 130   /* Prepare a NUL-terminated copy of name.  */
 131   memcpy (name_asciz, name, len);
 132   name_asciz[len] = '\0';
 133
 134   /* Save the old NetBIOS name.  */
 135   old_name_len = sizeof (old_name) - 1;
 136   if (! GetComputerNameEx (ComputerNamePhysicalNetBIOS,
 137                            old_name, &old_name_len))
 138     old_name_len = 0;
 139
 140   /* Set both the NetBIOS and the first part of the IP / DNS name.  */
 141   if (! SetComputerNameEx (ComputerNamePhysicalNetBIOS, name_asciz))
 142     {
 143       errno = (GetLastError () == ERROR_ACCESS_DENIED ? EPERM : EINVAL);
 144       return -1;
 145     }
 146   if (! SetComputerNameEx (ComputerNamePhysicalDnsHostname, name_asciz))
 147     {
 148       errno = (GetLastError () == ERROR_ACCESS_DENIED ? EPERM : EINVAL);
 149       /* Restore the old NetBIOS name.  */
 150       if (old_name_len > 0)
 151         {
 152           old_name[old_name_len] = '\0';
 153           SetComputerNameEx (ComputerNamePhysicalNetBIOS, old_name);
 154         }
 155       return -1;
 156     }
 157
 158   /* Note that the new host name becomes effective only after a reboot!  */
 159   return 0;
 160 }
 161
 162 #endif