lib/libc/net/if_indextoname.c

   1 /*      $NetBSD: if_indextoname.c,v 1.7 2010/12/13 23:10:12 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 1.7 2010/12/13 23:10:12 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 #ifndef RUMP_ACTION
  47 #ifdef __weak_alias
  48 __weak_alias(if_indextoname,_if_indextoname)
  49 #endif
  50 #endif
  51
  52 /*
  53  * From RFC 2533:
  54  *
  55  * The second function maps an interface index into its corresponding
  56  * name.
  57  *
  58  *    #include <net/if.h>
  59  *
  60  *    char  *if_indextoname(unsigned int ifindex, char *ifname);
  61  *
  62  * The ifname argument must point to a buffer of at least IF_NAMESIZE
  63  * bytes into which the interface name corresponding to the specified
  64  * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
  65  * its value includes a terminating null byte at the end of the
  66  * interface name.) This pointer is also the return value of the
  67  * function.  If there is no interface corresponding to the specified
  68  * index, NULL is returned, and errno is set to ENXIO, if there was a
  69  * system error (such as running out of memory), if_indextoname returns
  70  * NULL and errno would be set to the proper value (e.g., ENOMEM).
  71  */
  72
  73 char *
  74 if_indextoname(unsigned int ifindex, char *ifname)
  75 {
  76         struct ifaddrs *ifaddrs, *ifa;
  77         int error = 0;
  78
  79         if (getifaddrs(&ifaddrs) < 0)
  80                 return(NULL);   /* getifaddrs properly set errno */
  81
  82         for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
  83                 if (ifa->ifa_addr &&
  84                     ifa->ifa_addr->sa_family == AF_LINK &&
  85                     ifindex == ((struct sockaddr_dl*)
  86                         (void *)ifa->ifa_addr)->sdl_index)
  87                         break;
  88         }
  89
  90         if (ifa == NULL) {
  91                 error = ENXIO;
  92                 ifname = NULL;
  93         }
  94         else
  95                 strlcpy(ifname, ifa->ifa_name, IFNAMSIZ);
  96
  97         freeifaddrs(ifaddrs);
  98
  99         errno = error;
 100         return(ifname);
 101 }