aboutsummaryrefslogtreecommitdiff
path: root/ares/ares_gethostbyname.c
blob: 0d06dfe939709b430afd6e165e899bb9279eac20 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
/* 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>

#ifdef WIN32
#include "nameser.h"
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <arpa/nameser.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "ares.h"
#include "ares_private.h"

struct host_query {
  /* Arguments passed to ares_gethostbyname() */
  ares_channel channel;
  char *name;
  ares_host_callback callback;
  void *arg;

  const char *remaining_lookups;
};

static void next_lookup(struct host_query *hquery);
static void host_callback(void *arg, int status, unsigned char *abuf,
			  int alen);
static void end_hquery(struct host_query *hquery, int status,
		       struct hostent *host);
static int fake_hostent(const char *name, ares_host_callback callback,
			void *arg);
static int file_lookup(const char *name, struct hostent **host);
static void sort_addresses(struct hostent *host, struct apattern *sortlist,
			   int nsort);
static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
			     int nsort);

void ares_gethostbyname(ares_channel channel, const char *name, int family,
			ares_host_callback callback, void *arg)
{
  struct host_query *hquery;

  /* Right now we only know how to look up Internet addresses. */
  if (family != AF_INET)
    {
      callback(arg, ARES_ENOTIMP, NULL);
      return;
    }

  if (fake_hostent(name, callback, arg))
    return;

  /* Allocate and fill in the host query structure. */
  hquery = malloc(sizeof(struct host_query));
  if (!hquery)
    {
      callback(arg, ARES_ENOMEM, NULL);
      return;
    }
  hquery->channel = channel;
  hquery->name = strdup(name);
  if (!hquery->name)
    {
      free(hquery);
      callback(arg, ARES_ENOMEM, NULL);
      return;
    }
  hquery->callback = callback;
  hquery->arg = arg;
  hquery->remaining_lookups = channel->lookups;

  /* Start performing lookups according to channel->lookups. */
  next_lookup(hquery);
}

static void next_lookup(struct host_query *hquery)
{
  int status;
  const char *p;
  struct hostent *host;

  for (p = hquery->remaining_lookups; *p; p++)
    { 
      switch (*p)
	{
	case 'b':
	  /* DNS lookup */
	  hquery->remaining_lookups = p + 1;
	  ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
		      hquery);
	  return;

	case 'f':
	  /* Host file lookup */
	  status = file_lookup(hquery->name, &host);
	  if (status != ARES_ENOTFOUND)
	    {
	      end_hquery(hquery, status, host);
	      return;
	    }
	  break;
	}
    }
  end_hquery(hquery, ARES_ENOTFOUND, NULL);
}

static void host_callback(void *arg, int status, unsigned char *abuf, int alen)
{
  struct host_query *hquery = (struct host_query *) arg;
  ares_channel channel = hquery->channel;
  struct hostent *host;

  if (status == ARES_SUCCESS)
    {
      status = ares_parse_a_reply(abuf, alen, &host);
      if (host && channel->nsort)
	sort_addresses(host, channel->sortlist, channel->nsort);
      end_hquery(hquery, status, host);
    }
  else if (status == ARES_EDESTRUCTION)
    end_hquery(hquery, status, NULL);
  else
    next_lookup(hquery);
}

static void end_hquery(struct host_query *hquery, int status,
		       struct hostent *host)
{
  hquery->callback(hquery->arg, status, host);
  if (host)
    ares_free_hostent(host);
  free(hquery->name);
  free(hquery);
}

/* If the name looks like an IP address, fake up a host entry, end the
 * query immediately, and return true.  Otherwise return false.
 */
static int fake_hostent(const char *name, ares_host_callback callback,
			void *arg)
{
  struct in_addr addr;
  struct hostent hostent;
  const char *p;
  char *aliases[1] = { NULL };
  char *addrs[2];

  /* It only looks like an IP address if it's all numbers and dots. */
  for (p = name; *p; p++)
    {
      if (!isdigit((unsigned char)*p) && *p != '.')
	return 0;
    }

  /* It also only looks like an IP address if it's non-zero-length and
   * doesn't end with a dot.
   */
  if (p == name || *(p - 1) == '.')
    return 0;

  /* It looks like an IP address.  Figure out what IP address it is. */
  addr.s_addr = inet_addr(name);
  if (addr.s_addr == INADDR_NONE)
    {
      callback(arg, ARES_EBADNAME, NULL);
      return 1;
    }

  /* Duplicate the name, to avoid a constness violation. */
  hostent.h_name = strdup(name);
  if (!hostent.h_name)
    {
      callback(arg, ARES_ENOMEM, NULL);
      return 1;
    }

  /* Fill in the rest of the host structure and terminate the query. */
  addrs[0] = (char *) &addr;
  addrs[1] = NULL;
  hostent.h_aliases = aliases;
  hostent.h_addrtype = AF_INET;
  hostent.h_length = sizeof(struct in_addr);
  hostent.h_addr_list = addrs;
  callback(arg, ARES_SUCCESS, &hostent);

  free(hostent.h_name);
  return 1;
}

static int file_lookup(const char *name, struct hostent **host)
{
  FILE *fp;
  char **alias;
  int status;

#ifdef WIN32

  char PATH_HOSTS[MAX_PATH];
  if (IsNT) {
    GetSystemDirectory(PATH_HOSTS, MAX_PATH);
    strcat(PATH_HOSTS, PATH_HOSTS_NT);
  } else {
    GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
    strcat(PATH_HOSTS, PATH_HOSTS_9X);
  }

#elif defined(WATT32)
  extern const char *_w32_GetHostsFile (void);
  const char *PATH_HOSTS = _w32_GetHostsFile();

  if (!PATH_HOSTS)
    return ARES_ENOTFOUND;
#endif

  fp = fopen(PATH_HOSTS, "r");
  if (!fp)
    return ARES_ENOTFOUND;

  while ((status = ares__get_hostent(fp, host)) == ARES_SUCCESS)
    {
      if (strcasecmp((*host)->h_name, name) == 0)
	break;
      for (alias = (*host)->h_aliases; *alias; alias++)
	{
	  if (strcasecmp(*alias, name) == 0)
	    break;
	}
      if (*alias)
	break;
      ares_free_hostent(*host);
    }
  fclose(fp);
  if (status == ARES_EOF)
    status = ARES_ENOTFOUND;
  if (status != ARES_SUCCESS)
    *host = NULL;
  return status;
}

static void sort_addresses(struct hostent *host, struct apattern *sortlist,
			   int nsort)
{
  struct in_addr a1, a2;
  int i1, i2, ind1, ind2;

  /* This is a simple insertion sort, not optimized at all.  i1 walks
   * through the address list, with the loop invariant that everything
   * to the left of i1 is sorted.  In the loop body, the value at i1 is moved
   * back through the list (via i2) until it is in sorted order.
   */
  for (i1 = 0; host->h_addr_list[i1]; i1++)
    {
      memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr));
      ind1 = get_address_index(&a1, sortlist, nsort);
      for (i2 = i1 - 1; i2 >= 0; i2--)
	{
	  memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr));
	  ind2 = get_address_index(&a2, sortlist, nsort);
	  if (ind2 <= ind1)
	    break;
	  memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr));
	}
      memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr));
    }
}

/* Find the first entry in sortlist which matches addr.  Return nsort
 * if none of them match.
 */
static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
			     int nsort)
{
  int i;

  for (i = 0; i < nsort; i++)
    {
      if ((addr->s_addr & sortlist[i].mask.s_addr) == sortlist[i].addr.s_addr)
	break;
    }
  return i;
}