1  /* Miscellaneous definitions for libresolv.
       2     Copyright (C) 1995-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library 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 GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  /*
      20   * Copyright (c) 1995-1999 by Internet Software Consortium.
      21   *
      22   * Permission to use, copy, modify, and distribute this software for any
      23   * purpose with or without fee is hereby granted, provided that the above
      24   * copyright notice and this permission notice appear in all copies.
      25   *
      26   * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
      27   * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
      28   * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
      29   * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
      30   * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
      31   * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
      32   * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
      33   * SOFTWARE.
      34   */
      35  
      36  #include <resolv.h>
      37  
      38  /* This function belongs to libresolv, which is why it is not included
      39     in res-close.c.  */
      40  void
      41  __res_close (void)
      42  {
      43    /* Some programs call res_close before res_init.  Since _res._vcsock
      44       isn't explicitly initialized, these means that we could call
      45       close (0), which might lead to some security problems.  Therefore
      46       we check if res_init was called before by looking at the RES_INIT
      47       bit in _res.options.  If it hasn't been set we bail out
      48       early.  */
      49    if ((_res.options & RES_INIT) == 0)
      50      return;
      51    /* We don't free the name server addresses because we never did it
      52       and it would be done implicitly on shutdown.  */
      53    __res_iclose (&_res, false);
      54  }