inet/ether_ntoh.c

   1 /* Copyright (C) 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 Boston, MA 02111-1307, USA.  */
  19
  20 #include <netinet/ether.h>
  21 #include <netinet/if_ether.h>
  22
  23 #include "../nss/nsswitch.h"
  24
  25 /* Because the `ethers' lookup does not fit so well in the scheme so
  26    we define a dummy struct here which helps us to use the available
  27    functions.  */
  28 struct etherent
  29 {
  30   const char *e_name;
  31   struct ether_addr e_addr;
  32 };
  33
  34
  35 /* Type of the lookup function we need here.  */
  36 typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
  37                                 char *, int);
  38
  39
  40 int
  41 ether_ntohost (char *hostname, const struct ether_addr *addr)
  42 {
  43   static service_user *startp = NULL;
  44   static lookup_function start_fct;
  45   service_user *nip;
  46   lookup_function fct;
  47   int no_more;
  48   int result;
  49   enum nss_status status = NSS_STATUS_UNAVAIL;
  50   struct etherent etherent;
  51
  52   if (startp == NULL)
  53     {
  54       no_more = __nss_ethers_lookup (&nip, "getntohost_r", (void **) &fct);
  55       if (no_more)
  56         startp = (service_user *) -1;
  57       else
  58         {
  59           startp = nip;
  60           start_fct = fct;
  61         }
  62     }
  63   else
  64     {
  65       fct = start_fct;
  66       no_more = (nip = startp) == (service_user *) -1;
  67     }
  68
  69   while (no_more == 0)
  70     {
  71       char buffer[1024];
  72
  73       status = (*fct) (addr, &etherent, buffer, sizeof buffer);
  74
  75       no_more = __nss_next (&nip, "getntohost_r", (void **) &fct, status, 0);
  76     }
  77
  78   if (status == NSS_STATUS_SUCCESS)
  79     /* XXX This is a potential cause of trouble because the size of
  80        the HOSTNAME buffer is not known but the interface does not
  81        provide this information.  */
  82     strcpy (hostname, etherent.e_name);
  83
  84   return status == NSS_STATUS_SUCCESS ? 0 : -1;
  85 }