inet/ether_ntoh.c

   1 /* Copyright (C) 1996-2021 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <netinet/ether.h>
  21 #include <netinet/if_ether.h>
  22 #include <string.h>
  23
  24 #include <nss/nsswitch.h>
  25
  26
  27 /* Type of the lookup function we need here.  */
  28 typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
  29                                 char *, size_t, int *);
  30
  31 int
  32 ether_ntohost (char *hostname, const struct ether_addr *addr)
  33 {
  34   nss_action_list nip;
  35   union
  36   {
  37     lookup_function f;
  38     void *ptr;
  39   } fct;
  40   int no_more;
  41   enum nss_status status = NSS_STATUS_UNAVAIL;
  42   struct etherent etherent;
  43
  44   no_more = __nss_ethers_lookup2 (&nip, "getntohost_r", NULL, &fct.ptr);
  45
  46   while (no_more == 0)
  47     {
  48       char buffer[1024];
  49
  50       status = (*fct.f) (addr, &etherent, buffer, sizeof buffer, &errno);
  51
  52       no_more = __nss_next2 (&nip, "getntohost_r", NULL, &fct.ptr, status, 0);
  53     }
  54
  55   if (status == NSS_STATUS_SUCCESS)
  56     /* XXX This is a potential cause of trouble because the size of
  57        the HOSTNAME buffer is not known but the interface does not
  58        provide this information.  */
  59     strcpy (hostname, etherent.e_name);
  60
  61   return status == NSS_STATUS_SUCCESS ? 0 : -1;
  62 }