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/* Copyright (C) 1999, 2002, 2003, 2004 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Andreas Jaeger <aj@suse.de>.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, write to the Free

   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA

   02111-1307 USA.  */

#include "ifreq.h"

/* Variable to signal whether SIOCGIFCONF is not available.  */

#if __ASSUME_SIOCGIFNAME == 0 || 1

static int old_siocgifconf;

#else

# define old_siocgifconf 0

#endif

void

__ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)

{

  int fd = sockfd;

  struct ifconf ifc;

  int rq_len;

  int nifs;

# define RQ_IFS 4

  if (fd < 0)

    fd = __opensock ();

  if (fd < 0)

    {

      *num_ifs = 0;

      *ifreqs = NULL;

      return;

    }

  ifc.ifc_buf = NULL;

  /* We may be able to get the needed buffer size directly, rather than

     guessing.  */

  if (! old_siocgifconf)

    {

      ifc.ifc_buf = NULL;

      ifc.ifc_len = 0;

      if (ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)

        {

# if __ASSUME_SIOCGIFNAME == 0

          old_siocgifconf = 1;

# endif

          rq_len = RQ_IFS * sizeof (struct ifreq);

        }

      else

        rq_len = ifc.ifc_len;

    }

  else

    rq_len = RQ_IFS * sizeof (struct ifreq);

  /* Read all the interfaces out of the kernel.  */

  while (1)

    {

      ifc.ifc_len = rq_len;

      void *newp = realloc (ifc.ifc_buf, ifc.ifc_len);

      if (newp == NULL

          || (ifc.ifc_buf = newp, ioctl (fd, SIOCGIFCONF, &ifc)) < 0)

        {

          free (ifc.ifc_buf);

          if (fd != sockfd)

            close (fd);

          *num_ifs = 0;

          *ifreqs = NULL;

          return;

        }

      if (!old_siocgifconf || ifc.ifc_len < rq_len)

        break;

      rq_len *= 2;

    }

  nifs = ifc.ifc_len / sizeof (struct ifreq);

  if (fd != sockfd)

    close (fd);

  *num_ifs = nifs;

  *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));

}