gen.subproj/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
  28 #include <sys/types.h>
  29 #include <sys/socket.h>
  30 #include <net/if_dl.h>
  31 #include <net/if.h>
  32 #include <ifaddrs.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <errno.h>
  36
  37 /*
  38  * From RFC 2533:
  39  *
  40  * The second function maps an interface index into its corresponding
  41  * name.
  42  *
  43  *    #include <net/if.h>
  44  *
  45  *    char  *if_indextoname(unsigned int ifindex, char *ifname);
  46  *
  47  * The ifname argument must point to a buffer of at least IF_NAMESIZE
  48  * bytes into which the interface name corresponding to the specified
  49  * index is returned.  (IF_NAMESIZE is also defined in <net/if.h> and
  50  * its value includes a terminating null byte at the end of the
  51  * interface name.) This pointer is also the return value of the
  52  * function.  If there is no interface corresponding to the specified
  53  * index, NULL is returned, and errno is set to ENXIO, if there was a
  54  * system error (such as running out of memory), if_indextoname returns
  55  * NULL and errno would be set to the proper value (e.g., ENOMEM).
  56  */
  57
  58 char *
  59 if_indextoname(unsigned int ifindex, char *ifname)
  60 {
  61         struct ifaddrs *ifaddrs, *ifa;
  62         int error = 0;
  63
  64         if (getifaddrs(&ifaddrs) < 0)
  65                 return(NULL);   /* getifaddrs properly set errno */
  66
  67         for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
  68                 if (ifa->ifa_addr &&
  69                     ifa->ifa_addr->sa_family == AF_LINK &&
  70                     ifindex == ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index)
  71                         break;
  72         }
  73
  74         if (ifa == NULL) {
  75                 error = ENXIO;
  76                 ifname = NULL;
  77         }
  78         else
  79                 strncpy(ifname, ifa->ifa_name, IFNAMSIZ);
  80
  81         freeifaddrs(ifaddrs);
  82
  83         errno = error;
  84         return(ifname);
  85 }