sysdeps/unix/sysv/linux/ifreq.h

   1 /* Copyright (C) 1999,2002 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 <stdio.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <net/if.h>
  24 #include <sys/socket.h>
  25 #include <sys/ioctl.h>
  26 #include "kernel-features.h"
  27
  28 /* Variable to signal whether SIOCGIFCONF is not available.  */
  29 #if __ASSUME_SIOCGIFNAME == 0 || 1
  30 static int old_siocgifconf;
  31 #else
  32 # define old_siocgifconf 0
  33 #endif
  34
  35
  36 static inline void
  37 __ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)
  38 {
  39   int fd = sockfd;
  40   struct ifconf ifc;
  41   int rq_len;
  42   int nifs;
  43 # define RQ_IFS 4
  44
  45   if (fd < 0)
  46     fd = __opensock ();
  47   if (fd < 0)
  48     {
  49       *num_ifs = 0;
  50       *ifreqs = NULL;
  51       return;
  52     }
  53
  54   ifc.ifc_buf = NULL;
  55
  56   /* We may be able to get the needed buffer size directly, rather than
  57      guessing.  */
  58   if (! old_siocgifconf)
  59     {
  60       ifc.ifc_buf = NULL;
  61       ifc.ifc_len = 0;
  62       if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
  63         {
  64 # if __ASSUME_SIOCGIFNAME == 0
  65           old_siocgifconf = 1;
  66 # endif
  67           rq_len = RQ_IFS * sizeof (struct ifreq);
  68         }
  69       else
  70         rq_len = ifc.ifc_len;
  71     }
  72   else
  73     rq_len = RQ_IFS * sizeof (struct ifreq);
  74
  75   /* Read all the interfaces out of the kernel.  */
  76   while (1)
  77     {
  78       ifc.ifc_len = rq_len;
  79       ifc.ifc_buf = realloc (ifc.ifc_buf, ifc.ifc_len);
  80       if (ifc.ifc_buf == NULL || __ioctl (fd, SIOCGIFCONF, &ifc) < 0)
  81         {
  82           if (ifc.ifc_buf)
  83             free (ifc.ifc_buf);
  84
  85           if (fd != sockfd)
  86             __close (fd);
  87
  88           *num_ifs = 0;
  89           *ifreqs = NULL;
  90           return;
  91         }
  92
  93       if (!old_siocgifconf || ifc.ifc_len < rq_len)
  94         break;
  95
  96       rq_len *= 2;
  97     }
  98
  99   nifs = ifc.ifc_len / sizeof (struct ifreq);
 100
 101   if (fd != sockfd)
 102     __close (fd);
 103
 104   *num_ifs = nifs;
 105   *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));
 106 }
 107
 108 static inline struct ifreq *
 109 __if_nextreq (struct ifreq *ifr)
 110 {
 111   return ifr + 1;
 112 }
 113
 114 static inline void
 115 __if_freereq (struct ifreq *ifreqs, int num_ifs)
 116 {
 117   free (ifreqs);
 118 }