summaryrefslogtreecommitdiff
path: root/sysdeps/unix/sysv/linux/if_index.c
blob: 615a81d14aa8a9a8adb004cf6f6256049e4bf0e0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
/* Copyright (C) 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <net/if.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <bits/libc-lock.h>

/* Try to get a socket to talk to the kernel.  */
static int
opensock (void)
{
  /* Cache the last AF that worked, to avoid many redundant calls to
     socket().  */
  static int sock_af = -1;
  int fd = -1;
  __libc_lock_define_initialized (static, lock);

  if (sock_af != -1)
    {
      fd = socket (sock_af, SOCK_DGRAM, 0);
      if (fd != -1)
        return fd;
    }

  __libc_lock_lock (lock);

  if (sock_af != -1)
    fd = socket (sock_af, SOCK_DGRAM, 0);

  if (fd == -1)
    {
      fd = socket (sock_af = AF_INET6, SOCK_DGRAM, 0);
      if (fd < 0)
	fd = socket (sock_af = AF_INET, SOCK_DGRAM, 0);
      if (fd < 0)
	fd = socket (sock_af = AF_IPX, SOCK_DGRAM, 0);
      if (fd < 0)
	fd = socket (sock_af = AF_AX25, SOCK_DGRAM, 0);
      if (fd < 0)
	fd = socket (sock_af = AF_APPLETALK, SOCK_DGRAM, 0);
    }

  __libc_lock_unlock (lock);
  return fd;
}

unsigned int
if_nametoindex (const char *ifname)
{
#ifndef SIOGIFINDEX
  __set_errno (ENOSYS);
  return 0;
#else
  struct ifreq ifr;
  int fd = opensock ();

  if (fd < 0)
    return 0;

  strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
  if (ioctl (fd, SIOGIFINDEX, &ifr) < 0)
    {
      int saved_errno = errno;
      close (fd);
      if (saved_errno == EINVAL)
	__set_errno (ENOSYS);
      return 0;
    }
  close (fd);
  return ifr.ifr_ifindex;
#endif
}

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

struct if_nameindex *
if_nameindex (void)
{
#ifndef SIOGIFINDEX
  __set_errno (ENOSYS);
  return NULL;
#else
  int fd = opensock ();
  struct ifconf ifc;
  unsigned int rq_ifs = 4, nifs, i;
  struct if_nameindex *idx = NULL;

  if (fd < 0)
    return NULL;

  ifc.ifc_buf = NULL;

  /* Read all the interfaces out of the kernel.  */
  do
    {
      rq_ifs *= 2;
      ifc.ifc_len = rq_ifs * sizeof (struct ifreq);
      ifc.ifc_buf = realloc (ifc.ifc_buf, ifc.ifc_len);
      if (ifc.ifc_buf == NULL)
	{
	  close(fd);
	  return NULL;
	}
      if (ioctl (fd, SIOCGIFCONF, &ifc) < 0)
	goto jump;
    }
  while ((unsigned int) ifc.ifc_len == (rq_ifs * sizeof (struct ifreq)));

  nifs = ifc.ifc_len / sizeof (struct ifreq);
  ifc.ifc_buf = realloc (ifc.ifc_buf, ifc.ifc_len);

  idx = malloc ((nifs+1) * sizeof (struct if_nameindex));
  if (idx == NULL)
    goto jump;

  for (i = 0; i < nifs; ++i)
    {
      struct ifreq *ifr = &ifc.ifc_req[i];
      if ((idx[i].if_name = malloc (strlen (ifr->ifr_name)+1)) == NULL)
	{
	  free (idx);
	  idx = NULL;
	  goto jump;
	}
      strcpy (idx[i].if_name, ifr->ifr_name);
      if (ioctl (fd, SIOGIFINDEX, ifr) < 0)
	{
	  int saved_errno = errno;
	  free (idx);
	  idx = NULL;
	  if (saved_errno == EINVAL)
	    __set_errno (ENOSYS);
	  goto jump;
	}
      idx[i].if_index = ifr->ifr_ifindex;
    }
  idx[i].if_index = 0;
  idx[i].if_name = NULL;

jump:
  free (ifc.ifc_buf);
  close (fd);
  return idx;
#endif
}

char *
if_indextoname (unsigned int ifindex, char *ifname)
{
#ifndef SIOGIFINDEX
  __set_errno (ENOSYS);
  return NULL;
#else
  struct if_nameindex *idx = if_nameindex ();
  struct if_nameindex *p;
  char *result = NULL;

  if (idx != NULL)
    {
      for (p = idx; p->if_index || p->if_name; ++p)
	if (p->if_index == ifindex)
	  {
	    result = strncpy (ifname, p->if_name, IFNAMSIZ);
	    break;
	  }

      if_freenameindex (idx);
    }
  return result;
#endif
}