1/*	$KAME: if_indextoname.c,v 1.7 2000/11/08 03:09:30 itojun Exp $	*/
2
3/*-
4 * SPDX-License-Identifier: BSD-1-Clause
5 *
6 * Copyright (c) 1997, 2000
7 *	Berkeley Software Design, Inc.  All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 *	BSDI Id: if_indextoname.c,v 2.3 2000/04/17 22:38:05 dab Exp
28 */
29
30#include <sys/types.h>
31#include <sys/socket.h>
32#include <net/if_dl.h>
33#include <net/if.h>
34#include <ifaddrs.h>
35#include <stdlib.h>
36#include <string.h>
37#include <errno.h>
38
39/*
40 * From RFC 2553:
41 *
42 * The second function maps an interface index into its corresponding
43 * name.
44 *
45 *    #include <net/if.h>
46 *
47 *    char  *if_indextoname(unsigned int ifindex, char *ifname);
48 *
49 * The ifname argument must point to a buffer of at least IF_NAMESIZE
50 * bytes into which the interface name corresponding to the specified
51 * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
52 * its value includes a terminating null byte at the end of the
53 * interface name.) This pointer is also the return value of the
54 * function.  If there is no interface corresponding to the specified
55 * index, NULL is returned, and errno is set to ENXIO, if there was a
56 * system error (such as running out of memory), if_indextoname returns
57 * NULL and errno would be set to the proper value (e.g., ENOMEM).
58 */
59
60char *
61if_indextoname(unsigned int ifindex, char *ifname)
62{
63	struct ifaddrs *ifaddrs, *ifa;
64	int error = 0;
65
66	if (ifindex == 0) {
67		errno = ENXIO;
68		return(NULL);
69	}
70
71	if (getifaddrs(&ifaddrs) < 0)
72		return(NULL);	/* getifaddrs properly set errno */
73
74	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
75		if (ifa->ifa_addr &&
76		    ifa->ifa_addr->sa_family == AF_LINK &&
77		    ifindex == LLINDEX((struct sockaddr_dl*)ifa->ifa_addr))
78			break;
79	}
80
81	if (ifa == NULL) {
82		error = ENXIO;
83		ifname = NULL;
84	}
85	else
86		strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
87
88	freeifaddrs(ifaddrs);
89
90	errno = error;
91	return(ifname);
92}
93