sysdeps/unix/sysv/linux/if_index.c

   1 /* Copyright (C) 1997-2024 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    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <string.h>
  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 <libc-lock.h>
  27 #include <not-cancel.h>
  28
  29 #include "netlinkaccess.h"
  30
  31
  32 unsigned int
  33 __if_nametoindex (const char *ifname)
  34 {
  35 #ifndef SIOCGIFINDEX
  36   __set_errno (ENOSYS);
  37   return 0;
  38 #else
  39   struct ifreq ifr;
  40   if (strlen (ifname) >= IFNAMSIZ)
  41     {
  42       __set_errno (ENODEV);
  43       return 0;
  44     }
  45
  46   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
  47
  48   int fd = __opensock ();
  49
  50   if (fd < 0)
  51     return 0;
  52
  53   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
  54     {
  55       int saved_errno = errno;
  56       __close_nocancel_nostatus (fd);
  57       if (saved_errno == EINVAL)
  58         __set_errno (ENOSYS);
  59       return 0;
  60     }
  61   __close_nocancel_nostatus (fd);
  62   return ifr.ifr_ifindex;
  63 #endif
  64 }
  65 libc_hidden_def (__if_nametoindex)
  66 weak_alias (__if_nametoindex, if_nametoindex)
  67 libc_hidden_weak (if_nametoindex)
  68
  69
  70 void
  71 __if_freenameindex (struct if_nameindex *ifn)
  72 {
  73   struct if_nameindex *ptr = ifn;
  74   while (ptr->if_name || ptr->if_index)
  75     {
  76       free (ptr->if_name);
  77       ++ptr;
  78     }
  79   free (ifn);
  80 }
  81 libc_hidden_def (__if_freenameindex)
  82 weak_alias (__if_freenameindex, if_freenameindex)
  83 libc_hidden_weak (if_freenameindex)
  84
  85
  86 static struct if_nameindex *
  87 if_nameindex_netlink (void)
  88 {
  89   struct netlink_handle nh = { 0, 0, 0, NULL, NULL };
  90   struct if_nameindex *idx = NULL;
  91
  92   if (__netlink_open (&nh) < 0)
  93     return NULL;
  94
  95
  96   /* Tell the kernel that we wish to get a list of all
  97      active interfaces.  Collect all data for every interface.  */
  98   if (__netlink_request (&nh, RTM_GETLINK) < 0)
  99     goto exit_free;
 100
 101   /* Count the interfaces.  */
 102   unsigned int nifs = 0;
 103   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
 104     {
 105       struct nlmsghdr *nlh;
 106       size_t size = nlp->size;
 107
 108       if (nlp->nlh == NULL)
 109         continue;
 110
 111       /* Walk through all entries we got from the kernel and look, which
 112          message type they contain.  */
 113       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 114         {
 115           /* Check if the message is what we want.  */
 116           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 117             continue;
 118
 119           if (nlh->nlmsg_type == NLMSG_DONE)
 120             break;              /* ok */
 121
 122           if (nlh->nlmsg_type == RTM_NEWLINK)
 123             ++nifs;
 124         }
 125     }
 126
 127   idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
 128   if (idx == NULL)
 129     {
 130     nomem:
 131       __set_errno (ENOBUFS);
 132       goto exit_free;
 133     }
 134
 135   /* Add the interfaces.  */
 136   nifs = 0;
 137   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
 138     {
 139       struct nlmsghdr *nlh;
 140       size_t size = nlp->size;
 141
 142       if (nlp->nlh == NULL)
 143         continue;
 144
 145       /* Walk through all entries we got from the kernel and look, which
 146          message type they contain.  */
 147       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 148         {
 149           /* Check if the message is what we want.  */
 150           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 151             continue;
 152
 153           if (nlh->nlmsg_type == NLMSG_DONE)
 154             break;              /* ok */
 155
 156           if (nlh->nlmsg_type == RTM_NEWLINK)
 157             {
 158               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlh);
 159               struct rtattr *rta = IFLA_RTA (ifim);
 160               size_t rtasize = IFLA_PAYLOAD (nlh);
 161
 162               idx[nifs].if_index = ifim->ifi_index;
 163
 164               while (RTA_OK (rta, rtasize))
 165                 {
 166                   char *rta_data = RTA_DATA (rta);
 167                   size_t rta_payload = RTA_PAYLOAD (rta);
 168
 169                   if (rta->rta_type == IFLA_IFNAME)
 170                     {
 171                       idx[nifs].if_name = __strndup (rta_data, rta_payload);
 172                       if (idx[nifs].if_name == NULL)
 173                         {
 174                           idx[nifs].if_index = 0;
 175                           __if_freenameindex (idx);
 176                           idx = NULL;
 177                           goto nomem;
 178                         }
 179                       break;
 180                     }
 181
 182                   rta = RTA_NEXT (rta, rtasize);
 183                 }
 184
 185               ++nifs;
 186             }
 187         }
 188     }
 189
 190   idx[nifs].if_index = 0;
 191   idx[nifs].if_name = NULL;
 192
 193  exit_free:
 194   __netlink_free_handle (&nh);
 195   __netlink_close (&nh);
 196
 197   return idx;
 198 }
 199
 200
 201 struct if_nameindex *
 202 __if_nameindex (void)
 203 {
 204 #ifndef SIOCGIFINDEX
 205   __set_errno (ENOSYS);
 206   return NULL;
 207 #else
 208   struct if_nameindex *result = if_nameindex_netlink ();
 209   return result;
 210 #endif
 211 }
 212 weak_alias (__if_nameindex, if_nameindex)
 213 libc_hidden_weak (if_nameindex)
 214
 215
 216 char *
 217 __if_indextoname (unsigned int ifindex, char ifname[IF_NAMESIZE])
 218 {
 219   /* We may be able to do the conversion directly, rather than searching a
 220      list.  This ioctl is not present in kernels before version 2.1.50.  */
 221   struct ifreq ifr;
 222   int fd;
 223   int status;
 224
 225   fd = __opensock ();
 226
 227   if (fd < 0)
 228     return NULL;
 229
 230   ifr.ifr_ifindex = ifindex;
 231   status = __ioctl (fd, SIOCGIFNAME, &ifr);
 232
 233   __close_nocancel_nostatus (fd);
 234
 235   if (status  < 0)
 236     {
 237       if (errno == ENODEV)
 238         /* POSIX requires ENXIO.  */
 239         __set_errno (ENXIO);
 240
 241       return NULL;
 242     }
 243   else
 244     return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
 245 }
 246 weak_alias (__if_indextoname, if_indextoname)
 247 libc_hidden_weak (if_indextoname)