about summary refs log tree commit diff
path: root/sysdeps/unix/sysv/linux/if_index.c
blob: 9b3db6abfb4cbe243539e575bde5fe69feec770e (plain) (blame)
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
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
/* Copyright (C) 1997, 1998, 1999 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 <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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.  */
#if defined SIOGIFINDEX || defined SIOGIFNAME
static int
internal_function
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;
}
#endif

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 nifs, i;
  int rq_len;
  struct if_nameindex *idx = NULL;
  static int old_siocgifconf;
#define RQ_IFS	4

  if (fd < 0)
    return NULL;

  ifc.ifc_buf = NULL;

  /* We may be able to get the needed buffer size directly, rather than
     guessing.  */
  if (! old_siocgifconf)
    {
      ifc.ifc_buf = NULL;
      ifc.ifc_len = 0;
      if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
	{
	  old_siocgifconf = 1;
	  rq_len = RQ_IFS * sizeof (struct ifreq);
	}
      else
	rq_len = ifc.ifc_len;
    }
  else
    rq_len = RQ_IFS * sizeof (struct ifreq);

  /* Read all the interfaces out of the kernel.  */
  do
    {
      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 == rq_len && old_siocgifconf);

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

  idx = malloc ((nifs + 1) * sizeof (struct if_nameindex));
  if (idx == NULL)
    {
      __close (fd);
      return NULL;
    }

  for (i = 0; i < nifs; ++i)
    {
      struct ifreq *ifr = &ifc.ifc_req[i];
      idx[i].if_name = __strdup (ifr->ifr_name);
      if (idx[i].if_name == NULL
	  || __ioctl (fd, SIOGIFINDEX, ifr) < 0)
	{
	  int saved_errno = errno;
	  unsigned int j;

	  for (j =  0; j < i; ++j)
	    free (idx[j].if_name);
	  free (idx);
	  __close (fd);
	  if (saved_errno == EINVAL)
	    __set_errno (ENOSYS);
	  return NULL;
	}
      idx[i].if_index = ifr->ifr_ifindex;
    }

  idx[i].if_index = 0;
  idx[i].if_name = NULL;

  __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;
  struct if_nameindex *p;
  char *result = NULL;

#ifdef SIOGIFNAME
  /* We may be able to do the conversion directly, rather than searching a
     list.  This ioctl is not present in kernels before version 2.1.50.  */
  struct ifreq ifr;
  int fd;
  static int siogifname_works_not;

  if (!siogifname_works_not)
    {
      int serrno = errno;

      fd = opensock ();

      if (fd < 0)
	return NULL;

      ifr.ifr_ifindex = ifindex;
      if (__ioctl (fd, SIOGIFNAME, &ifr) < 0)
	{
	  if (errno == EINVAL)
	    siogifname_works_not = 1; /* Don't make the same mistake twice. */
	}
      else
	{
	  __close (fd);
	  return strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
	}

      __close (fd);

      __set_errno (serrno);
    }
#endif

  idx = if_nameindex ();

  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
}