inetutils/libinetutils/if_index.c

/*
  Copyright (C) 2001-2025 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

#include <config.h>

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>

/* Solaris at least earlier 2.6 and before does not include
   the ioctl definitions if BSD_COMP is not set.  */
#if defined __svr4__
# define BSD_COMP 1
#endif

#include <sys/ioctl.h>
#include <net/if.h>

#ifndef HAVE_STRUCT_IF_NAMEINDEX
unsigned int
if_nametoindex (const char *ifname)
{
  int result = 0;
# ifdef SIOCGIFINDEX
  {
    int fd = socket (AF_INET, SOCK_DGRAM, 0);
    if (fd >= 0)
      {
	int rc;
	struct ifreq ifr;
	strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
	rc = ioctl (fd, SIOCGIFINDEX, &ifr);
	close (fd);
	if (rc == 0)
	  return ifr.ifr_index;
      }
  }
# endif
  {
    struct if_nameindex *idx;
    idx = if_nameindex ();
    if (idx != NULL)
      {
	struct if_nameindex *p;
	for (p = idx; p->if_index || p->if_name; ++p)
	  {
	    if (strncmp (p->if_name, ifname, IFNAMSIZ) == 0)
	      {
		result = p->if_index;
		break;
	      }
	  }
	if_freenameindex (idx);
      }
    return result;
  }
}

void
if_freenameindex (struct if_nameindex *ifn)
{
  struct if_nameindex *ptr = ifn;
  if (!ifn)
    return;
  while (ptr->if_name || ptr->if_index)
    {
      free (ptr->if_name);
      ++ptr;
    }
  free (ifn);
}

struct if_nameindex *
if_nameindex (void)
{
# if defined SIOCGIFCONF
  int fd = socket (AF_INET, SOCK_DGRAM, 0);
  struct ifconf ifc;
  unsigned int i = 0;
  int rq_len, last_len;
  struct if_nameindex *idx = NULL;
  struct ifreq *ifr, *end, *cur;

  if (fd < 0)
    return NULL;

  /* A first estimate.  */
  rq_len = 4 * sizeof (struct ifreq);

  ifc.ifc_buf = NULL;
  ifc.ifc_len = 0;
  /* Read all the interfaces out of the kernel.  */
  do
    {
      last_len = ifc.ifc_len;
      ifc.ifc_buf = alloca (ifc.ifc_len = rq_len);
      if (ifc.ifc_buf == NULL || ioctl (fd, SIOCGIFCONF, &ifc) < 0)
	{
	  close (fd);
	  return NULL;
	}
      rq_len *= 2;
    }
  while (ifc.ifc_len != last_len);

  i = 0;
  ifr = (struct ifreq *) ifc.ifc_req;
  end = (struct ifreq *) (ifr + ifc.ifc_len);
  while (ifr < end)
    {
      cur = ifr;

      ++ifr;

      /* We ignore the other families .. OK ?  */
      if (cur->ifr_addr.sa_family != AF_INET)
	continue;

      /* Make Room safely.  */
      {
	struct if_nameindex *tidx = NULL;
	tidx = realloc (idx, (i + 1) * sizeof (*idx));
	if (tidx == NULL)
	  {
	    if_freenameindex (idx);
	    close (fd);
	    errno = ENOBUFS;
	    return NULL;
	  }
	idx = tidx;
      }

      /* FIXME: We did not deal with duplicates or interface aliases.  */

      idx[i].if_name = strdup (cur->ifr_name);
      if (idx[i].if_name == NULL)
	{
	  if_freenameindex (idx);
	  close (fd);
	  errno = ENOBUFS;
	  return NULL;
	}

#  if defined SIOCGIFINDEX
      if (ioctl (fd, SIOCGIFINDEX, cur) >= 0)
	idx[i].if_index = cur->ifr_index;
      else
#  endif
	idx[i].if_index = i + 1;
      i++;
    }

  /* Terminate the array with an empty solt.  */
  {
    struct if_nameindex *tidx = NULL;
    tidx = realloc (idx, (i + 1) * sizeof (*idx));
    if (tidx == NULL)
      {
	if_freenameindex (idx);
	close (fd);
	errno = ENOBUFS;
	return NULL;
      }
    idx = tidx;
  }
  idx[i].if_index = 0;
  idx[i].if_name = NULL;

  close (fd);
  return idx;

# else
  errno = ENOSYS;
  return NULL;
# endif
}
#endif