sysdeps/unix/ifreq.c

   1 /* Copyright (C) 1999-2017 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "ifreq.h"
  20
  21
  22 void
  23 __ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)
  24 {
  25   int fd = sockfd;
  26   struct ifconf ifc;
  27   int rq_len;
  28   int nifs;
  29 # define RQ_IFS 4
  30
  31   if (fd < 0)
  32     fd = __opensock ();
  33   if (fd < 0)
  34     {
  35       *num_ifs = 0;
  36       *ifreqs = NULL;
  37       return;
  38     }
  39
  40   ifc.ifc_buf = NULL;
  41   rq_len = RQ_IFS * sizeof (struct ifreq) / 2; /* Doubled in the loop.  */
  42   do
  43     {
  44       ifc.ifc_len = rq_len *= 2;
  45       void *newp = realloc (ifc.ifc_buf, ifc.ifc_len);
  46       if (newp == NULL || __ioctl (fd, SIOCGIFCONF, &ifc) < 0)
  47         {
  48           free (ifc.ifc_buf);
  49
  50           if (fd != sockfd)
  51             __close (fd);
  52           *num_ifs = 0;
  53           *ifreqs = NULL;
  54           return;
  55         }
  56       ifc.ifc_buf = newp;
  57     }
  58   while (rq_len < sizeof (struct ifreq) + ifc.ifc_len);
  59
  60   if (fd != sockfd)
  61     __close (fd);
  62
  63 #ifdef _HAVE_SA_LEN
  64   struct ifreq *ifr = *ifreqs;
  65   nifs = 0;
  66   while ((char *) ifr < ifc.ifc_buf + ifc.ifc_len)
  67     {
  68       ++nifs;
  69       ifr = __if_nextreq (ifr);
  70       if (ifr == NULL)
  71         break;
  72     }
  73 #else
  74   nifs = ifc.ifc_len / sizeof (struct ifreq);
  75 #endif
  76
  77   *num_ifs = nifs;
  78   *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));
  79 }