1  /* Copyright (C) 1996-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <errno.h>
      19  #include <netinet/ether.h>
      20  #include <netinet/if_ether.h>
      21  #include <string.h>
      22  
      23  #include <nss/nsswitch.h>
      24  
      25  
      26  /* Type of the lookup function we need here.  */
      27  typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
      28  				char *, size_t, int *);
      29  
      30  int
      31  ether_ntohost (char *hostname, const struct ether_addr *addr)
      32  {
      33    nss_action_list nip;
      34    union
      35    {
      36      lookup_function f;
      37      void *ptr;
      38    } fct;
      39    int no_more;
      40    enum nss_status status = NSS_STATUS_UNAVAIL;
      41    struct etherent etherent;
      42  
      43    no_more = __nss_ethers_lookup2 (&nip, "getntohost_r", NULL, &fct.ptr);
      44  
      45    while (no_more == 0)
      46      {
      47        char buffer[1024];
      48  
      49        status = (*fct.f) (addr, &etherent, buffer, sizeof buffer, &errno);
      50  
      51        no_more = __nss_next2 (&nip, "getntohost_r", NULL, &fct.ptr, status, 0);
      52      }
      53  
      54    if (status == NSS_STATUS_SUCCESS)
      55      /* XXX This is a potential cause of trouble because the size of
      56         the HOSTNAME buffer is not known but the interface does not
      57         provide this information.  */
      58      strcpy (hostname, etherent.e_name);
      59  
      60    return status == NSS_STATUS_SUCCESS ? 0 : -1;
      61  }