sysdeps/unix/sysv/linux/if_index.c

   1 /* Copyright (C) 1997-2025 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   if (strlen (ifname) >= IFNAMSIZ)
  36     {
  37       __set_errno (ENODEV);
  38       return 0;
  39     }
  40
  41   int fd = __opensock ();
  42   if (fd < 0)
  43     return 0;
  44
  45   struct ifreq ifr;
  46   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
  47
  48   int status = __ioctl (fd, SIOCGIFINDEX, &ifr);
  49   __close_nocancel_nostatus (fd);
  50
  51   return status < 0 ? 0 : ifr.ifr_ifindex;
  52 }
  53 libc_hidden_def (__if_nametoindex)
  54 weak_alias (__if_nametoindex, if_nametoindex)
  55 libc_hidden_weak (if_nametoindex)
  56
  57
  58 void
  59 __if_freenameindex (struct if_nameindex *ifn)
  60 {
  61   struct if_nameindex *ptr = ifn;
  62   while (ptr->if_name || ptr->if_index)
  63     {
  64       free (ptr->if_name);
  65       ++ptr;
  66     }
  67   free (ifn);
  68 }
  69 libc_hidden_def (__if_freenameindex)
  70 weak_alias (__if_freenameindex, if_freenameindex)
  71 libc_hidden_weak (if_freenameindex)
  72
  73
  74 struct if_nameindex *
  75 __if_nameindex (void)
  76 {
  77   struct netlink_handle nh = { 0, 0, 0, NULL, NULL };
  78   struct if_nameindex *idx = NULL;
  79
  80   if (__netlink_open (&nh) < 0)
  81     return NULL;
  82
  83
  84   /* Tell the kernel that we wish to get a list of all
  85      active interfaces.  Collect all data for every interface.  */
  86   if (__netlink_request (&nh, RTM_GETLINK) < 0)
  87     goto exit_free;
  88
  89   /* Count the interfaces.  */
  90   unsigned int nifs = 0;
  91   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
  92     {
  93       struct nlmsghdr *nlh;
  94       size_t size = nlp->size;
  95
  96       if (nlp->nlh == NULL)
  97         continue;
  98
  99       /* Walk through all entries we got from the kernel and look, which
 100          message type they contain.  */
 101       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 102         {
 103           /* Check if the message is what we want.  */
 104           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 105             continue;
 106
 107           if (nlh->nlmsg_type == NLMSG_DONE)
 108             break;              /* ok */
 109
 110           if (nlh->nlmsg_type == RTM_NEWLINK)
 111             ++nifs;
 112         }
 113     }
 114
 115   idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
 116   if (idx == NULL)
 117     {
 118     nomem:
 119       __set_errno (ENOBUFS);
 120       goto exit_free;
 121     }
 122
 123   /* Add the interfaces.  */
 124   nifs = 0;
 125   for (struct netlink_res *nlp = nh.nlm_list; nlp; nlp = nlp->next)
 126     {
 127       struct nlmsghdr *nlh;
 128       size_t size = nlp->size;
 129
 130       if (nlp->nlh == NULL)
 131         continue;
 132
 133       /* Walk through all entries we got from the kernel and look, which
 134          message type they contain.  */
 135       for (nlh = nlp->nlh; NLMSG_OK (nlh, size); nlh = NLMSG_NEXT (nlh, size))
 136         {
 137           /* Check if the message is what we want.  */
 138           if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 139             continue;
 140
 141           if (nlh->nlmsg_type == NLMSG_DONE)
 142             break;              /* ok */
 143
 144           if (nlh->nlmsg_type == RTM_NEWLINK)
 145             {
 146               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlh);
 147               struct rtattr *rta = IFLA_RTA (ifim);
 148               size_t rtasize = IFLA_PAYLOAD (nlh);
 149
 150               idx[nifs].if_index = ifim->ifi_index;
 151
 152               while (RTA_OK (rta, rtasize))
 153                 {
 154                   char *rta_data = RTA_DATA (rta);
 155                   size_t rta_payload = RTA_PAYLOAD (rta);
 156
 157                   if (rta->rta_type == IFLA_IFNAME)
 158                     {
 159                       idx[nifs].if_name = __strndup (rta_data, rta_payload);
 160                       if (idx[nifs].if_name == NULL)
 161                         {
 162                           idx[nifs].if_index = 0;
 163                           __if_freenameindex (idx);
 164                           idx = NULL;
 165                           goto nomem;
 166                         }
 167                       break;
 168                     }
 169
 170                   rta = RTA_NEXT (rta, rtasize);
 171                 }
 172
 173               ++nifs;
 174             }
 175         }
 176     }
 177
 178   idx[nifs].if_index = 0;
 179   idx[nifs].if_name = NULL;
 180
 181  exit_free:
 182   __netlink_free_handle (&nh);
 183   __netlink_close (&nh);
 184
 185   return idx;
 186 }
 187 weak_alias (__if_nameindex, if_nameindex)
 188 libc_hidden_weak (if_nameindex)
 189
 190
 191 char *
 192 __if_indextoname (unsigned int ifindex, char ifname[IF_NAMESIZE])
 193 {
 194   /* We may be able to do the conversion directly, rather than searching a
 195      list.  This ioctl is not present in kernels before version 2.1.50.  */
 196   struct ifreq ifr;
 197   int fd;
 198   int status;
 199
 200   fd = __opensock ();
 201
 202   if (fd < 0)
 203     return NULL;
 204
 205   ifr.ifr_ifindex = ifindex;
 206   status = __ioctl (fd, SIOCGIFNAME, &ifr);
 207
 208   __close_nocancel_nostatus (fd);
 209
 210   if (status  < 0)
 211     {
 212       if (errno == ENODEV)
 213         /* POSIX requires ENXIO.  */
 214         __set_errno (ENXIO);
 215
 216       return NULL;
 217     }
 218   else
 219     return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
 220 }
 221 weak_alias (__if_indextoname, if_indextoname)
 222 libc_hidden_weak (if_indextoname)