sysdeps/gnu/ifaddrs.c

   1 /* getifaddrs -- get names and addresses of all network interfaces
   2    Copyright (C) 2002 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <ifaddrs.h>
  21 #include <net/if.h>
  22 #include <sys/socket.h>
  23 #include <sys/ioctl.h>
  24 #include <unistd.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <errno.h>
  28 #include <netinet/in.h>
  29
  30 #include "ifreq.h"
  31
  32 /* Create a linked list of `struct ifaddrs' structures, one for each
  33    network interface on the host machine.  If successful, store the
  34    list in *IFAP and return 0.  On errors, return -1 and set `errno'.  */
  35 int
  36 getifaddrs (struct ifaddrs **ifap)
  37 {
  38   /* This implementation handles only IPv4 interfaces.
  39      The various ioctls below will only work on an AF_INET socket.
  40      Some different mechanism entirely must be used for IPv6.  */
  41   int fd = __socket (AF_INET, SOCK_DGRAM, 0);
  42   struct ifreq *ifreqs;
  43   int nifs, i;
  44
  45   if (fd < 0)
  46     return -1;
  47
  48   __ifreq (&ifreqs, &nifs, fd);
  49   if (ifreqs == NULL)           /* XXX doesn't distinguish error vs none */
  50     {
  51       __close (fd);
  52       return -1;
  53     }
  54
  55   /* Now we have the list of interfaces and each one's address.
  56      Put it into the expected format and fill in the remaining details.  */
  57   if (nifs == 0)
  58     *ifap = NULL;
  59   else
  60     {
  61       struct
  62       {
  63         struct ifaddrs ia;
  64         struct sockaddr addr, netmask, broadaddr;
  65         char name[IF_NAMESIZE];
  66       } *storage;
  67
  68       storage = malloc (nifs * sizeof storage[0]);
  69       if (storage == NULL)
  70         {
  71           __close (fd);
  72           __if_freereq (ifreqs, nifs);
  73           return -1;
  74         }
  75
  76       i = 0;
  77       do
  78         {
  79           struct ifreq *const ifr = &ifreqs[i];
  80
  81           /* Fill in all pointers to the storage we've already allocated.  */
  82           storage[i].ia.ifa_next = &storage[i + 1].ia;
  83           storage[i].ia.ifa_addr = &storage[i].addr;
  84           storage[i].ia.ifa_netmask = &storage[i].netmask;
  85           storage[i].ia.ifa_broadaddr = &storage[i].broadaddr; /* & dstaddr */
  86
  87           /* Now copy the information we already have from SIOCGIFCONF.  */
  88           storage[i].ia.ifa_name = strncpy (storage[i].name, ifr->ifr_name,
  89                                             sizeof storage[i].name);
  90           storage[i].addr = ifr->ifr_addr;
  91
  92           /* The SIOCGIFCONF call filled in only the name and address.
  93              Now we must also ask for the other information we need.  */
  94
  95           if (__ioctl (fd, SIOCGIFFLAGS, ifr) < 0)
  96             break;
  97           storage[i].ia.ifa_flags = ifr->ifr_flags;
  98
  99           ifr->ifr_addr = storage[i].addr;
 100           if (__ioctl (fd, SIOCGIFNETMASK, ifr) < 0)
 101             break;
 102           storage[i].netmask = ifr->ifr_netmask;
 103
 104           if (ifr->ifr_flags & IFF_BROADCAST)
 105             {
 106               ifr->ifr_addr = storage[i].addr;
 107               if (__ioctl (fd, SIOCGIFBRDADDR, ifr) < 0)
 108                 break;
 109               storage[i].broadaddr = ifr->ifr_broadaddr;
 110             }
 111           else if (ifr->ifr_flags & IFF_POINTOPOINT)
 112             {
 113               ifr->ifr_addr = storage[i].addr;
 114               if (__ioctl (fd, SIOCGIFDSTADDR, ifr) < 0)
 115                 break;
 116               storage[i].broadaddr = ifr->ifr_dstaddr;
 117             }
 118           else
 119             /* Just 'cause.  */
 120             memset (&storage[i].broadaddr, 0, sizeof storage[i].broadaddr);
 121
 122           storage[i].ia.ifa_data = NULL; /* Nothing here for now.  */
 123
 124         } while (++i < nifs);
 125       if (i < nifs)             /* Broke out early on error.  */
 126         {
 127           __close (fd);
 128           free (storage);
 129           __if_freereq (ifreqs, nifs);
 130           return -1;
 131         }
 132       storage[i - 1].ia.ifa_next = NULL;
 133
 134       *ifap = &storage[0].ia;
 135
 136       __close (fd);
 137       __if_freereq (ifreqs, nifs);
 138     }
 139
 140   return 0;
 141 }
 142
 143 void
 144 freeifaddrs (struct ifaddrs *ifa)
 145 {
 146   free (ifa);
 147 }