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if_indextoname.c revision 1.3 
      1 /*	$NetBSD: if_indextoname.c,v 1.3 2000/07/06 02:54:55 christos Exp $	*/
      2 /*	$KAME: if_indextoname.c,v 1.4 2000/04/24 10:08:41 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 1.3 2000/07/06 02:54:55 christos Exp $");
     32 #endif /* LIBC_SCCS and not lint */
     33 
     34 #include "namespace.h"
     35 #include <sys/types.h>
     36 #include <sys/socket.h>
     37 #include <net/if_dl.h>
     38 #include <net/if.h>
     39 #include <ifaddrs.h>
     40 #include <stdlib.h>
     41 #include <string.h>
     42 
     43 #ifdef __weak_alias
     44 __weak_alias(if_indextoname,_if_indextoname)
     45 #endif
     46 
     47 /*
     48  * From RFC 2133:
     49  *
     50  * 4.2.  Index-to-Name
     51  *
     52  *    The second function maps an interface index into its corresponding
     53  *    name.
     54  *
     55  *        #include <net/if.h>
     56  *
     57  *        char  *if_indextoname(unsigned int ifindex, char *ifname);
     58  *
     59  *    The ifname argument must point to a buffer of at least IFNAMSIZ bytes
     60  *    into which the interface name corresponding to the specified index is
     61  *    returned.  (IFNAMSIZ is also defined in <net/if.h> and its value
     62  *    includes a terminating null byte at the end of the interface name.)
     63  *    This pointer is also the return value of the function.  If there is
     64  *    no interface corresponding to the specified index, NULL is returned.
     65  */
     66 
     67 char *
     68 if_indextoname(unsigned int ifindex, char *ifname)
     69 {
     70 	struct ifaddrs *ifaddrs, *ifa;
     71 
     72 	if (getifaddrs(&ifaddrs) < 0)
     73 		return(NULL);
     74 
     75 	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
     76 		if (ifa->ifa_addr &&
     77 		    ifa->ifa_addr->sa_family == AF_LINK &&
     78 		    ifindex == ((struct sockaddr_dl*)
     79 			(void *)ifa->ifa_addr)->sdl_index)
     80 			break;
     81 	}
     82 
     83 	if (ifa == NULL)
     84 		ifname = NULL;
     85 	else
     86 		strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
     87 
     88 	freeifaddrs(ifaddrs);
     89 
     90 	return(ifname);
     91 }
     92