lib/libc/net/if_indextoname.c

   1 /*      $KAME: if_indextoname.c,v 1.7 2000/11/08 03:09:30 itojun Exp $  */
   2
   3 /*-
   4  * Copyright (c) 1997, 2000
   5  *      Berkeley Software Design, Inc.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
  14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  16  * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
  17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  23  * SUCH DAMAGE.
  24  *
  25  *      BSDI Id: if_indextoname.c,v 2.3 2000/04/17 22:38:05 dab Exp
  26  *
  27  * $FreeBSD: src/lib/libc/net/if_indextoname.c,v 1.1.2.1 2002/07/29 18:33:18 ume Exp $
  28  * $DragonFly: src/lib/libc/net/if_indextoname.c,v 1.2 2003/06/17 04:26:44 dillon Exp $
  29  */
  30
  31 #include <sys/types.h>
  32 #include <sys/socket.h>
  33 #include <net/if_dl.h>
  34 #include <net/if.h>
  35 #include <ifaddrs.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <errno.h>
  39
  40 /*
  41  * From RFC 2533:
  42  *
  43  * The second function maps an interface index into its corresponding
  44  * name.
  45  *
  46  *    #include <net/if.h>
  47  *
  48  *    char  *if_indextoname(unsigned int ifindex, char *ifname);
  49  *
  50  * The ifname argument must point to a buffer of at least IF_NAMESIZE
  51  * bytes into which the interface name corresponding to the specified
  52  * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
  53  * its value includes a terminating null byte at the end of the
  54  * interface name.) This pointer is also the return value of the
  55  * function.  If there is no interface corresponding to the specified
  56  * index, NULL is returned, and errno is set to ENXIO, if there was a
  57  * system error (such as running out of memory), if_indextoname returns
  58  * NULL and errno would be set to the proper value (e.g., ENOMEM).
  59  */
  60
  61 char *
  62 if_indextoname(unsigned int ifindex, char *ifname)
  63 {
  64         struct ifaddrs *ifaddrs, *ifa;
  65         int error = 0;
  66
  67         if (getifaddrs(&ifaddrs) < 0)
  68                 return(NULL);   /* getifaddrs properly set errno */
  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                 error = ENXIO;
  79                 ifname = NULL;
  80         }
  81         else
  82                 strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
  83
  84         freeifaddrs(ifaddrs);
  85
  86         errno = error;
  87         return(ifname);
  88 }