inet/ether_ntoh.c

   1 /* Copyright (C) 1996, 1997, 1999, 2001, 2002 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <netinet/ether.h>
  22 #include <netinet/if_ether.h>
  23 #include <string.h>
  24
  25 #include <nss/nsswitch.h>
  26
  27
  28 /* Type of the lookup function we need here.  */
  29 typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
  30                                 char *, size_t, int *);
  31
  32 /* The lookup function for the first entry of this service.  */
  33 extern int __nss_ethers_lookup (service_user **nip, const char *name,
  34                                 void **fctp) internal_function;
  35
  36
  37 int
  38 ether_ntohost (char *hostname, const struct ether_addr *addr)
  39 {
  40   static service_user *startp;
  41   static lookup_function start_fct;
  42   service_user *nip;
  43   union
  44   {
  45     lookup_function f;
  46     void *ptr;
  47   } fct;
  48   int no_more;
  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", &fct.ptr);
  55       if (no_more)
  56         startp = (service_user *) -1;
  57       else
  58         {
  59           startp = nip;
  60           start_fct = fct.f;
  61         }
  62     }
  63   else
  64     {
  65       fct.f = 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.f) (addr, &etherent, buffer, sizeof buffer, &errno);
  74
  75       no_more = __nss_next (&nip, "getntohost_r", &fct.ptr, 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 }