ares__get_hostent.c

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/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */
 
 
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
 
#ifndef WIN32
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
 
 
#include "ares.h"
#include "ares_private.h"
 
int ares__get_hostent(FILE *fp, struct hostent **host)
{
  char *line = NULL, *p, *q, *canonical, **alias;
  int status, linesize, end_at_hostname, naliases;
  struct in_addr addr;
  struct hostent *hostent = NULL;
 
  while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
    {
      /* Skip comment lines; terminate line at comment character. */
      if (*line == '#' || !*line)
    continue;
      p = strchr(line, '#');
      if (p)
    *p = 0;
 
      /* Get the address part. */
      p = line;
      while (*p && !isspace((unsigned char)*p))
    p++;
      if (!*p)
    continue;
      *p = 0;
      /* TODO - add suppport for V6 addresses in hosts file */
#if defined(_MSC_VER) && _MSC_VER >= 1800  /* removing compilation warning in VS2013+ */
      inet_pton(AF_INET, line, &addr.s_addr);
#else
      addr.s_addr = inet_addr(line);
#endif
      if (addr.s_addr == INADDR_NONE)
    continue;
 
      /* Get the canonical hostname. */
      p++;
      while (isspace((unsigned char)*p))
    p++;
      if (!*p)
    continue;
      q = p;
      while (*q && !isspace((unsigned char)*q))
    q++;
      end_at_hostname = (*q == 0);
      *q = 0;
      canonical = p;
 
      naliases = 0;
      if (!end_at_hostname)
    {
      /* Count the aliases. */
      p = q + 1;
      while (isspace((unsigned char)*p))
        p++;
      while (*p)
        {
          while (*p && !isspace((unsigned char)*p))
        p++;
          while (isspace((unsigned char)*p))
        p++;
          naliases++;
        }
    }
 
      /* Allocate memory for the host structure. */
      hostent = malloc(sizeof(struct hostent));
      if (!hostent)
    break;
      hostent->h_aliases = NULL;
      hostent->h_addr_list = NULL;
      hostent->h_name = strdup(canonical);
      if (!hostent->h_name)
    break;
      hostent->h_addr_list = malloc(2 * sizeof(char *));
      if (!hostent->h_addr_list)
    break;
      hostent->h_addr_list[0] = malloc(sizeof(struct in_addr));
      if (!hostent->h_addr_list[0])
    break;
      hostent->h_aliases = malloc((naliases + 1) * sizeof(char *));
      if (!hostent->h_aliases)
    break;
 
      /* Copy in aliases. */
      naliases = 0;
      if (!end_at_hostname)
    {
      p = canonical + strlen(canonical) + 1;
      while (isspace((unsigned char)*p))
        p++;
      while (*p)
        {
          q = p;
          while (*q && !isspace((unsigned char)*q))
        q++;
          hostent->h_aliases[naliases] = malloc(q - p + 1);
          if (hostent->h_aliases[naliases] == NULL)
        break;
          memcpy(hostent->h_aliases[naliases], p, q - p);
          hostent->h_aliases[naliases][q - p] = 0;
          p = q;
          while (isspace((unsigned char)*p))
        p++;
          naliases++;
        }
      if (*p)
        break;
    }
      hostent->h_aliases[naliases] = NULL;
 
      hostent->h_addrtype = AF_INET;
      hostent->h_length = sizeof(struct in_addr);
      memcpy(hostent->h_addr_list[0], &addr, sizeof(struct in_addr));
      hostent->h_addr_list[1] = NULL;
      *host = hostent;
      free(line);
      return ARES_SUCCESS;
    }
  free(line);
 
  if (status == ARES_SUCCESS)
    {
      /* Memory allocation failure; clean up. */
      if (hostent)
    {
      free((char *) hostent->h_name);
      if (hostent->h_aliases)
        {
          for (alias = hostent->h_aliases; *alias; alias++)
        free(*alias);
        }
      free(hostent->h_aliases);
      if (hostent->h_addr_list)
        free(hostent->h_addr_list[0]);
      free(hostent->h_addr_list);
    }
      free(hostent);
      return ARES_ENOMEM;
    }
 
  return status;
}