sysdeps/gnu/ifaddrs.c

   1 /* getifaddrs -- get names and addresses of all network interfaces
   2    Copyright (C) 2002-2023 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <ifaddrs.h>
  20 #include <net/if.h>
  21 #include <sys/socket.h>
  22 #include <sys/ioctl.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <errno.h>
  27 #include <netinet/in.h>
  28
  29 #include "ifreq.h"
  30
  31 /* Create a linked list of `struct ifaddrs' structures, one for each
  32    network interface on the host machine.  If successful, store the
  33    list in *IFAP and return 0.  On errors, return -1 and set `errno'.  */
  34 int
  35 __getifaddrs (struct ifaddrs **ifap)
  36 {
  37   /* This implementation handles only IPv4 interfaces.
  38      The various ioctls below will only work on an AF_INET socket.
  39      Some different mechanism entirely must be used for IPv6.  */
  40   int fd = __socket (AF_INET, SOCK_DGRAM, 0);
  41   struct ifreq *ifreqs;
  42   int nifs;
  43
  44   if (fd < 0)
  45     return -1;
  46
  47   __ifreq (&ifreqs, &nifs, fd);
  48   if (ifreqs == NULL)           /* XXX doesn't distinguish error vs none */
  49     {
  50       __close (fd);
  51       return -1;
  52     }
  53
  54   /* Now we have the list of interfaces and each one's address.
  55      Put it into the expected format and fill in the remaining details.  */
  56   if (nifs == 0)
  57     *ifap = NULL;
  58   else
  59     {
  60       struct
  61       {
  62         struct ifaddrs ia;
  63         struct sockaddr addr, netmask, broadaddr;
  64         char name[IF_NAMESIZE];
  65       } *storage;
  66       struct ifreq *ifr;
  67       int i;
  68
  69       storage = malloc (nifs * sizeof storage[0]);
  70       if (storage == NULL)
  71         {
  72           __close (fd);
  73           __if_freereq (ifreqs, nifs);
  74           return -1;
  75         }
  76
  77       i = 0;
  78       ifr = ifreqs;
  79       do
  80         {
  81           /* Fill in 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
  85           /* Now copy the information we already have from SIOCGIFCONF.  */
  86           storage[i].ia.ifa_name = strncpy (storage[i].name, ifr->ifr_name,
  87                                             sizeof storage[i].name);
  88           storage[i].addr = ifr->ifr_addr;
  89
  90           /* The SIOCGIFCONF call filled in only the name and address.
  91              Now we must also ask for the other information we need.  */
  92
  93           if (__ioctl (fd, SIOCGIFFLAGS, ifr) < 0)
  94             break;
  95           storage[i].ia.ifa_flags = ifr->ifr_flags;
  96
  97           ifr->ifr_addr = storage[i].addr;
  98
  99           if (__ioctl (fd, SIOCGIFNETMASK, ifr) < 0)
 100             storage[i].ia.ifa_netmask = NULL;
 101           else
 102             {
 103               storage[i].ia.ifa_netmask = &storage[i].netmask;
 104               storage[i].netmask = ifr->ifr_netmask;
 105             }
 106
 107           if (ifr->ifr_flags & IFF_BROADCAST)
 108             {
 109               ifr->ifr_addr = storage[i].addr;
 110               if (__ioctl (fd, SIOCGIFBRDADDR, ifr) < 0)
 111                 storage[i].ia.ifa_broadaddr = NULL;
 112               {
 113                 storage[i].ia.ifa_broadaddr = &storage[i].broadaddr;
 114                 storage[i].broadaddr = ifr->ifr_broadaddr;
 115               }
 116             }
 117           else if (ifr->ifr_flags & IFF_POINTOPOINT)
 118             {
 119               ifr->ifr_addr = storage[i].addr;
 120               if (__ioctl (fd, SIOCGIFDSTADDR, ifr) < 0)
 121                 storage[i].ia.ifa_broadaddr = NULL;
 122               else
 123                 {
 124                   storage[i].ia.ifa_broadaddr = &storage[i].broadaddr;
 125                   storage[i].broadaddr = ifr->ifr_dstaddr;
 126                 }
 127             }
 128           else
 129             storage[i].ia.ifa_broadaddr = NULL;
 130
 131           storage[i].ia.ifa_data = NULL; /* Nothing here for now.  */
 132
 133           ifr = __if_nextreq (ifr);
 134         } while (++i < nifs);
 135       if (i < nifs)             /* Broke out early on error.  */
 136         {
 137           __close (fd);
 138           free (storage);
 139           __if_freereq (ifreqs, nifs);
 140           return -1;
 141         }
 142
 143       storage[i - 1].ia.ifa_next = NULL;
 144
 145       *ifap = &storage[0].ia;
 146
 147       __close (fd);
 148       __if_freereq (ifreqs, nifs);
 149     }
 150
 151   return 0;
 152 }
 153 weak_alias (__getifaddrs, getifaddrs)
 154 libc_hidden_def (__getifaddrs)
 155 #ifndef getifaddrs
 156 libc_hidden_weak (getifaddrs)
 157 #endif
 158
 159 void
 160 __freeifaddrs (struct ifaddrs *ifa)
 161 {
 162   free (ifa);
 163 }
 164 weak_alias (__freeifaddrs, freeifaddrs)
 165 libc_hidden_def (__freeifaddrs)
 166 libc_hidden_weak (freeifaddrs)