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/types.h>
29#include <sys/socket.h>
30#include <net/if_dl.h>
31#include <net/if.h>
32#include <ifaddrs.h>
33#include <stdlib.h>
34#include <string.h>
35#include <errno.h>
36
37/*
38 * From RFC 2533:
39 *
40 * The second function maps an interface index into its corresponding
41 * name.
42 *
43 *    #include <net/if.h>
44 *
45 *    char  *if_indextoname(unsigned int ifindex, char *ifname);
46 *
47 * The ifname argument must point to a buffer of at least IF_NAMESIZE
48 * bytes into which the interface name corresponding to the specified
49 * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
50 * its value includes a terminating null byte at the end of the
51 * interface name.) This pointer is also the return value of the
52 * function.  If there is no interface corresponding to the specified
53 * index, NULL is returned, and errno is set to ENXIO, if there was a
54 * system error (such as running out of memory), if_indextoname returns
55 * NULL and errno would be set to the proper value (e.g., ENOMEM).
56 */
57
58char *
59if_indextoname(unsigned int ifindex, char *ifname)
60{
61	struct ifaddrs *ifaddrs, *ifa;
62	int error = 0;
63
64	if (getifaddrs(&ifaddrs) < 0)
65		return(NULL);	/* getifaddrs properly set errno */
66
67	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
68		if (ifa->ifa_addr &&
69		    ifa->ifa_addr->sa_family == AF_LINK &&
70		    ifindex == ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index)
71			break;
72	}
73
74	if (ifa == NULL) {
75		error = ENXIO;
76		ifname = NULL;
77	}
78	else
79		strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
80
81	freeifaddrs(ifaddrs);
82
83	errno = error;
84	return(ifname);
85}
86