sysdeps/unix/sysv/linux/if_index.c

   1 /* Copyright (C) 1997-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <alloca.h>
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <net/if.h>
  25 #include <sys/socket.h>
  26 #include <sys/ioctl.h>
  27 #include <bits/libc-lock.h>
  28 #include <not-cancel.h>
  29
  30 #include "netlinkaccess.h"
  31
  32
  33 unsigned int
  34 if_nametoindex (const char *ifname)
  35 {
  36 #ifndef SIOCGIFINDEX
  37   __set_errno (ENOSYS);
  38   return 0;
  39 #else
  40   struct ifreq ifr;
  41   int fd = __opensock ();
  42
  43   if (fd < 0)
  44     return 0;
  45
  46   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
  47   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
  48     {
  49       int saved_errno = errno;
  50       close_not_cancel_no_status (fd);
  51       if (saved_errno == EINVAL)
  52         __set_errno (ENOSYS);
  53       return 0;
  54     }
  55   close_not_cancel_no_status (fd);
  56   return ifr.ifr_ifindex;
  57 #endif
  58 }
  59 libc_hidden_def (if_nametoindex)
  60
  61
  62 void
  63 if_freenameindex (struct if_nameindex *ifn)
  64 {
  65   struct if_nameindex *ptr = ifn;
  66   while (ptr->if_name || ptr->if_index)
  67     {
  68       free (ptr->if_name);
  69       ++ptr;
  70     }
  71   free (ifn);
  72 }
  73 libc_hidden_def (if_freenameindex)
  74
  75
  76 static struct if_nameindex *
  77 if_nameindex_netlink (void)
  78 {
  79   struct netlink_handle nh = { 0, 0, 0, NULL, NULL };
  80   struct if_nameindex *idx = NULL;
  81
  82   if (__netlink_open (&nh) < 0)
  83     return NULL;
  84
  85
  86   /* Tell the kernel that we wish to get a list of all
  87      active interfaces.  Collect all data for every interface.  */
  88   if (__netlink_request (&nh, RTM_GETLINK) < 0)
  89     goto exit_free;
  90
  91   /* Count the interfaces.  */
  92   unsigned int nifs = 0;
  93   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
  94     {
  95       struct nlmsghdr *nlh;
  96       size_t size = nlp->size;
  97
  98       if (nlp->nlh == NULL)
  99         continue;
 100
 101       /* Walk through all entries we got from the kernel and look, which
 102          message type they contain.  */
 103       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 104         {
 105           /* Check if the message is what we want.  */
 106           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 107             continue;
 108
 109           if (nlh->nlmsg_type == NLMSG_DONE)
 110             break;              /* ok */
 111
 112           if (nlh->nlmsg_type == RTM_NEWLINK)
 113             ++nifs;
 114         }
 115     }
 116
 117   idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
 118   if (idx == NULL)
 119     {
 120     nomem:
 121       __set_errno (ENOBUFS);
 122       goto exit_free;
 123     }
 124
 125   /* Add the interfaces.  */
 126   nifs = 0;
 127   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
 128     {
 129       struct nlmsghdr *nlh;
 130       size_t size = nlp->size;
 131
 132       if (nlp->nlh == NULL)
 133         continue;
 134
 135       /* Walk through all entries we got from the kernel and look, which
 136          message type they contain.  */
 137       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 138         {
 139           /* Check if the message is what we want.  */
 140           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 141             continue;
 142
 143           if (nlh->nlmsg_type == NLMSG_DONE)
 144             break;              /* ok */
 145
 146           if (nlh->nlmsg_type == RTM_NEWLINK)
 147             {
 148               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlh);
 149               struct rtattr *rta = IFLA_RTA (ifim);
 150               size_t rtasize = IFLA_PAYLOAD (nlh);
 151
 152               idx[nifs].if_index = ifim->ifi_index;
 153
 154               while (RTA_OK (rta, rtasize))
 155                 {
 156                   char *rta_data = RTA_DATA (rta);
 157                   size_t rta_payload = RTA_PAYLOAD (rta);
 158
 159                   if (rta->rta_type == IFLA_IFNAME)
 160                     {
 161                       idx[nifs].if_name = __strndup (rta_data, rta_payload);
 162                       if (idx[nifs].if_name == NULL)
 163                         {
 164                           idx[nifs].if_index = 0;
 165                           if_freenameindex (idx);
 166                           idx = NULL;
 167                           goto nomem;
 168                         }
 169                       break;
 170                     }
 171
 172                   rta = RTA_NEXT (rta, rtasize);
 173                 }
 174
 175               ++nifs;
 176             }
 177         }
 178     }
 179
 180   idx[nifs].if_index = 0;
 181   idx[nifs].if_name = NULL;
 182
 183  exit_free:
 184   __netlink_free_handle (&nh);
 185   __netlink_close (&nh);
 186
 187   return idx;
 188 }
 189
 190
 191 struct if_nameindex *
 192 if_nameindex (void)
 193 {
 194 #ifndef SIOCGIFINDEX
 195   __set_errno (ENOSYS);
 196   return NULL;
 197 #else
 198   struct if_nameindex *result = if_nameindex_netlink ();
 199   return result;
 200 #endif
 201 }
 202 libc_hidden_def (if_nameindex)
 203
 204
 205 char *
 206 if_indextoname (unsigned int ifindex, char *ifname)
 207 {
 208   /* We may be able to do the conversion directly, rather than searching a
 209      list.  This ioctl is not present in kernels before version 2.1.50.  */
 210   struct ifreq ifr;
 211   int fd;
 212   int status;
 213
 214   fd = __opensock ();
 215
 216   if (fd < 0)
 217     return NULL;
 218
 219   ifr.ifr_ifindex = ifindex;
 220   status = __ioctl (fd, SIOCGIFNAME, &ifr);
 221
 222   close_not_cancel_no_status (fd);
 223
 224   if (status  < 0)
 225     {
 226       if (errno == ENODEV)
 227         /* POSIX requires ENXIO.  */
 228         __set_errno (ENXIO);
 229
 230       return NULL;
 231     }
 232   else
 233     return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
 234 }
 235 libc_hidden_def (if_indextoname)