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if_indextoname.c revision 1.6 
      1 /*	$NetBSD: if_indextoname.c,v 1.6 2010/12/13 21:07:54 pooka Exp $	*/
      2 /*	$KAME: if_indextoname.c,v 1.7 2000/11/08 03:09:30 itojun Exp $	*/
      3 
      4 /*-
      5  * Copyright (c) 1997, 2000
      6  *	Berkeley Software Design, Inc.  All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  *
     14  * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
     15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     17  * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
     18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     24  * SUCH DAMAGE.
     25  *
     26  *	BSDI Id: if_indextoname.c,v 2.3 2000/04/17 22:38:05 dab Exp
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 #if defined(LIBC_SCCS) && !defined(lint)
     31 __RCSID("$NetBSD: if_indextoname.c,v 1.6 2010/12/13 21:07:54 pooka Exp $");
     32 #endif /* LIBC_SCCS and not lint */
     33 
     34 #ifndef RUMP_ACTION
     35 #include "namespace.h"
     36 #endif
     37 #include <sys/types.h>
     38 #include <sys/socket.h>
     39 #include <net/if_dl.h>
     40 #include <net/if.h>
     41 #include <ifaddrs.h>
     42 #include <stdlib.h>
     43 #include <string.h>
     44 #include <errno.h>
     45 
     46 #ifdef __weak_alias
     47 __weak_alias(if_indextoname,_if_indextoname)
     48 #endif
     49 
     50 /*
     51  * From RFC 2533:
     52  *
     53  * The second function maps an interface index into its corresponding
     54  * name.
     55  *
     56  *    #include <net/if.h>
     57  *
     58  *    char  *if_indextoname(unsigned int ifindex, char *ifname);
     59  *
     60  * The ifname argument must point to a buffer of at least IF_NAMESIZE
     61  * bytes into which the interface name corresponding to the specified
     62  * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
     63  * its value includes a terminating null byte at the end of the
     64  * interface name.) This pointer is also the return value of the
     65  * function.  If there is no interface corresponding to the specified
     66  * index, NULL is returned, and errno is set to ENXIO, if there was a
     67  * system error (such as running out of memory), if_indextoname returns
     68  * NULL and errno would be set to the proper value (e.g., ENOMEM).
     69  */
     70 
     71 char *
     72 if_indextoname(unsigned int ifindex, char *ifname)
     73 {
     74 	struct ifaddrs *ifaddrs, *ifa;
     75 	int error = 0;
     76 
     77 	if (getifaddrs(&ifaddrs) < 0)
     78 		return(NULL);	/* getifaddrs properly set errno */
     79 
     80 	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
     81 		if (ifa->ifa_addr &&
     82 		    ifa->ifa_addr->sa_family == AF_LINK &&
     83 		    ifindex == ((struct sockaddr_dl*)
     84 			(void *)ifa->ifa_addr)->sdl_index)
     85 			break;
     86 	}
     87 
     88 	if (ifa == NULL) {
     89 		error = ENXIO;
     90 		ifname = NULL;
     91 	}
     92 	else
     93 		strlcpy(ifname, ifa->ifa_name, IFNAMSIZ);
     94 
     95 	freeifaddrs(ifaddrs);
     96 
     97 	errno = error;
     98 	return(ifname);
     99 }
    100