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if_indextoname.c revision 1.1 
      1 /*	$NetBSD: if_indextoname.c,v 1.1 2000/04/24 10:24:47 itojun 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 "namespace.h"
     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 
     38 #ifdef __weak_alias
     39 __weak_alias(if_indextoname,_if_indextoname)
     40 #endif
     41 
     42 /*
     43  * From RFC 2133:
     44  *
     45  * 4.2.  Index-to-Name
     46  *
     47  *    The second function maps an interface index into its corresponding
     48  *    name.
     49  *
     50  *        #include <net/if.h>
     51  *
     52  *        char  *if_indextoname(unsigned int ifindex, char *ifname);
     53  *
     54  *    The ifname argument must point to a buffer of at least IFNAMSIZ bytes
     55  *    into which the interface name corresponding to the specified index is
     56  *    returned.  (IFNAMSIZ is also defined in <net/if.h> and its value
     57  *    includes a terminating null byte at the end of the interface name.)
     58  *    This pointer is also the return value of the function.  If there is
     59  *    no interface corresponding to the specified index, NULL is returned.
     60  */
     61 
     62 char *
     63 if_indextoname(unsigned int ifindex, char *ifname)
     64 {
     65 	struct ifaddrs *ifaddrs, *ifa;
     66 
     67 	if (getifaddrs(&ifaddrs) < 0)
     68 		return(NULL);
     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 == ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index)
     74 			break;
     75 	}
     76 
     77 	if (ifa == NULL)
     78 		ifname = NULL;
     79 	else
     80 		strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
     81 
     82 	freeifaddrs(ifaddrs);
     83 
     84 	return(ifname);
     85 }
     86