1/*	$KAME: if_indextoname.c,v 1.7 2000/11/08 03:09:30 itojun Exp $	*/
2
3/*-
4 * Copyright (c) 1997, 2000
5 *	Berkeley Software Design, Inc.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 *
25 *	BSDI Id: if_indextoname.c,v 2.3 2000/04/17 22:38:05 dab Exp
26 */
27
28#include <sys/cdefs.h>
29__FBSDID("$FreeBSD$");
30
31#include <sys/types.h>
32#include <sys/socket.h>
33#include <net/if_dl.h>
34#include <net/if.h>
35#include <ifaddrs.h>
36#include <stdlib.h>
37#include <string.h>
38#include <errno.h>
39
40/*
41 * From RFC 2533:
42 *
43 * The second function maps an interface index into its corresponding
44 * name.
45 *
46 *    #include <net/if.h>
47 *
48 *    char  *if_indextoname(unsigned int ifindex, char *ifname);
49 *
50 * The ifname argument must point to a buffer of at least IF_NAMESIZE
51 * bytes into which the interface name corresponding to the specified
52 * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
53 * its value includes a terminating null byte at the end of the
54 * interface name.) This pointer is also the return value of the
55 * function.  If there is no interface corresponding to the specified
56 * index, NULL is returned, and errno is set to ENXIO, if there was a
57 * system error (such as running out of memory), if_indextoname returns
58 * NULL and errno would be set to the proper value (e.g., ENOMEM).
59 */
60
61char *
62if_indextoname(unsigned int ifindex, char *ifname)
63{
64	struct ifaddrs *ifaddrs, *ifa;
65	int error = 0;
66
67	if (getifaddrs(&ifaddrs) < 0)
68		return(NULL);	/* getifaddrs properly set errno */
69
70	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
71		if (ifa->ifa_addr &&
72		    ifa->ifa_addr->sa_family == AF_LINK &&
73		    ifindex == LLINDEX((struct sockaddr_dl*)ifa->ifa_addr))
74			break;
75	}
76
77	if (ifa == NULL) {
78		error = ENXIO;
79		ifname = NULL;
80	}
81	else
82		strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
83
84	freeifaddrs(ifaddrs);
85
86	errno = error;
87	return(ifname);
88}
89