inet/ifreq.c

   1 /* Copyright (C) 1999, 2002, 2003, 2004 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Andreas Jaeger <aj@suse.de>.
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include "ifreq.h"
  21
  22
  23 void
  24 __ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)
  25 {
  26   int fd = sockfd;
  27   struct ifconf ifc;
  28   int rq_len;
  29   int nifs;
  30 # define RQ_IFS 4
  31
  32   if (fd < 0)
  33     fd = __opensock ();
  34   if (fd < 0)
  35     {
  36       *num_ifs = 0;
  37       *ifreqs = NULL;
  38       return;
  39     }
  40
  41   ifc.ifc_buf = NULL;
  42   rq_len = RQ_IFS * sizeof (struct ifreq) / 2; /* Doubled in the loop.  */
  43   do
  44     {
  45       ifc.ifc_len = rq_len *= 2;
  46       void *newp = realloc (ifc.ifc_buf, ifc.ifc_len);
  47       if (newp == NULL || __ioctl (fd, SIOCGIFCONF, &ifc) < 0)
  48         {
  49           free (ifc.ifc_buf);
  50
  51           if (fd != sockfd)
  52             __close (fd);
  53           *num_ifs = 0;
  54           *ifreqs = NULL;
  55           return;
  56         }
  57       ifc.ifc_buf = newp;
  58     }
  59   while (rq_len < sizeof (struct ifreq) + ifc.ifc_len);
  60
  61   if (fd != sockfd)
  62     __close (fd);
  63
  64 #ifdef _HAVE_SA_LEN
  65   struct ifreq *ifr = *ifreqs;
  66   nifs = 0;
  67   while ((char *) ifr < ifc.ifc_buf + ifc.ifc_len)
  68     {
  69       ++nifs;
  70       ifr = __if_nextreq (ifr);
  71       if (ifr == NULL)
  72         break;
  73     }
  74 #else
  75   nifs = ifc.ifc_len / sizeof (struct ifreq);
  76 #endif
  77
  78   *num_ifs = nifs;
  79   *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));
  80 }