if_indextoname.c revision 49eb7613068297a1f2181ad39a24f27cd87d89b1 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <string.h>
30#include <unistd.h>
31#include <linux/sockios.h>
32#include <net/if.h>
33#include <sys/socket.h>
34#include <sys/ioctl.h>
35#include <errno.h>
36
37/*
38 * Map an interface index into its name.
39 * Returns NULL on error.
40 */
41char*
42if_indextoname(unsigned ifindex, char *ifname)
43{
44    int ctl_sock;
45    struct ifreq ifr;
46    char*  ret = NULL;
47
48    memset(&ifr, 0, sizeof(struct ifreq));
49    ifr.ifr_ifindex = ifindex;
50
51    if ((ctl_sock = socket(AF_INET, SOCK_DGRAM, 0)) >= 0) {
52        if (ioctl(ctl_sock, SIOCGIFNAME, &ifr) >= 0) {
53            ret = strncpy (ifname, ifr.ifr_name, IFNAMSIZ);
54        } else {
55            /* Posix requires ENXIO */
56            if (errno == ENODEV)
57                errno = ENXIO;
58        }
59        close(ctl_sock);
60    }
61    return ret;
62}
63