inet/ether_ntoh.c

   1 /* Copyright (C) 1996, 1997 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 not,
  17    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 #include <string.h>
  23
  24 #include <nss/nsswitch.h>
  25
  26 /* Because the `ethers' lookup does not fit so well in the scheme so
  27    we define a dummy struct here which helps us to use the available
  28    functions.  */
  29 struct etherent
  30 {
  31   const char *e_name;
  32   struct ether_addr e_addr;
  33 };
  34
  35
  36 /* Type of the lookup function we need here.  */
  37 typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
  38                                 char *, int);
  39
  40 /* The lookup function for the first entry of this service.  */
  41 extern int __nss_ethers_lookup (service_user **nip, const char *name,
  42                                 void **fctp);
  43
  44
  45 int
  46 ether_ntohost (char *hostname, const struct ether_addr *addr)
  47 {
  48   static service_user *startp = NULL;
  49   static lookup_function start_fct;
  50   service_user *nip;
  51   lookup_function fct;
  52   int no_more;
  53   enum nss_status status = NSS_STATUS_UNAVAIL;
  54   struct etherent etherent;
  55
  56   if (startp == NULL)
  57     {
  58       no_more = __nss_ethers_lookup (&nip, "getntohost_r", (void **) &fct);
  59       if (no_more)
  60         startp = (service_user *) -1;
  61       else
  62         {
  63           startp = nip;
  64           start_fct = fct;
  65         }
  66     }
  67   else
  68     {
  69       fct = start_fct;
  70       no_more = (nip = startp) == (service_user *) -1;
  71     }
  72
  73   while (no_more == 0)
  74     {
  75       char buffer[1024];
  76
  77       status = (*fct) (addr, &etherent, buffer, sizeof buffer);
  78
  79       no_more = __nss_next (&nip, "getntohost_r", (void **) &fct, status, 0);
  80     }
  81
  82   if (status == NSS_STATUS_SUCCESS)
  83     /* XXX This is a potential cause of trouble because the size of
  84        the HOSTNAME buffer is not known but the interface does not
  85        provide this information.  */
  86     strcpy (hostname, etherent.e_name);
  87
  88   return status == NSS_STATUS_SUCCESS ? 0 : -1;
  89 }