1  /* Convert a struct hostent object to a string.
       2     Copyright (C) 2016-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       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 <support/format_nss.h>
      20  
      21  #include <arpa/inet.h>
      22  #include <errno.h>
      23  #include <stdio.h>
      24  #include <stdlib.h>
      25  #include <support/support.h>
      26  #include <support/xmemstream.h>
      27  
      28  static int
      29  address_length (int family)
      30  {
      31    switch (family)
      32      {
      33      case AF_INET:
      34        return 4;
      35      case AF_INET6:
      36        return 16;
      37      }
      38    return -1;
      39  }
      40  
      41  char *
      42  support_format_hostent (struct hostent *h)
      43  {
      44    if (h == NULL)
      45      {
      46        if (h_errno == NETDB_INTERNAL)
      47          return xasprintf ("error: NETDB_INTERNAL (errno %d, %m)\n", errno);
      48        else
      49          {
      50            char *value = support_format_herrno (h_errno);
      51            char *result = xasprintf ("error: %s\n", value);
      52            free (value);
      53            return result;
      54          }
      55      }
      56  
      57    struct xmemstream mem;
      58    xopen_memstream (&mem);
      59  
      60    fprintf (mem.out, "name: %s\n", h->h_name);
      61    for (char **alias = h->h_aliases; *alias != NULL; ++alias)
      62      fprintf (mem.out, "alias: %s\n", *alias);
      63    for (unsigned i = 0; h->h_addr_list[i] != NULL; ++i)
      64      {
      65        char buf[128];
      66        if (inet_ntop (h->h_addrtype, h->h_addr_list[i],
      67                       buf, sizeof (buf)) == NULL)
      68          fprintf (mem.out, "error: inet_ntop failed: %m\n");
      69        else
      70          fprintf (mem.out, "address: %s\n", buf);
      71      }
      72    if (h->h_length != address_length (h->h_addrtype))
      73      {
      74        char *family = support_format_address_family (h->h_addrtype);
      75        fprintf (mem.out, "error: invalid address length %d for %s\n",
      76                 h->h_length, family);
      77        free (family);
      78      }
      79  
      80    xfclose_memstream (&mem);
      81    return mem.buffer;
      82  }