aboutsummaryrefslogtreecommitdiff
path: root/src/curl/curl.c
blob: ac9eeb4fc9c2fd824c3d0dac1c2b8c597142884c (plain) (blame)
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
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
/*
  This file is part of GNUnet
  Copyright (C) 2014, 2015, 2016 GNUnet e.V.

  GNUnet is free software; you can redistribute it and/or modify it under the
  terms of the GNU General Public License as published by the Free Software
  Foundation; either version 3, or (at your option) any later version.

  GNUnet is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  GNUnet; see the file COPYING.  If not, If not, see
  <http://www.gnu.org/licenses/>
*/
/**
 * @file curl/curl.c
 * @brief API for downloading JSON via CURL
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 * @author Christian Grothoff
 */
#include "platform.h"
#if HAVE_CURL_CURL_H
#include <curl/curl.h>
#elif HAVE_GNURL_CURL_H
#include <gnurl/curl.h>
#endif
#include <jansson.h>
#include "gnunet_curl_lib.h"


/**
 * Log error related to CURL operations.
 *
 * @param type log level
 * @param function which function failed to run
 * @param code what was the curl error code
 */
#define CURL_STRERROR(type, function, code)      \
 GNUNET_log (type,                               \
             "Curl function `%s' has failed at `%s:%d' with error: %s\n", \
             function, __FILE__, __LINE__, curl_easy_strerror (code));

/**
 * Print JSON parsing related error information
 */
#define JSON_WARN(error)                                                \
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,                              \
                "JSON parsing failed at %s:%u: %s (%s)\n",              \
                __FILE__, __LINE__, error.text, error.source)


/**
 * Failsafe flag. Raised if our constructor fails to initialize
 * the Curl library.
 */
static int curl_fail;


/**
 * @brief Buffer data structure we use to buffer the HTTP download
 * before giving it to the JSON parser.
 */
struct DownloadBuffer
{

  /**
   * Download buffer
   */
  void *buf;

  /**
   * The size of the download buffer
   */
  size_t buf_size;

  /**
   * Error code (based on libc errno) if we failed to download
   * (i.e. response too large).
   */
  int eno;

};


/**
 * Jobs are CURL requests running within a `struct GNUNET_CURL_Context`.
 */
struct GNUNET_CURL_Job
{

  /**
   * We keep jobs in a DLL.
   */
  struct GNUNET_CURL_Job *next;

  /**
   * We keep jobs in a DLL.
   */
  struct GNUNET_CURL_Job *prev;

  /**
   * Easy handle of the job.
   */
  CURL *easy_handle;

  /**
   * Context this job runs in.
   */
  struct GNUNET_CURL_Context *ctx;

  /**
   * Function to call upon completion.
   */
  GNUNET_CURL_JobCompletionCallback jcc;

  /**
   * Closure for @e jcc.
   */
  void *jcc_cls;

  /**
   * Buffer for response received from CURL.
   */
  struct DownloadBuffer db;

};


/**
 * Context
 */
struct GNUNET_CURL_Context
{
  /**
   * Curl multi handle
   */
  CURLM *multi;

  /**
   * Curl share handle
   */
  CURLSH *share;

  /**
   * We keep jobs in a DLL.
   */
  struct GNUNET_CURL_Job *jobs_head;

  /**
   * We keep jobs in a DLL.
   */
  struct GNUNET_CURL_Job *jobs_tail;

  /**
   * HTTP header "application/json", created once and used
   * for all requests that need it.
   */
  struct curl_slist *json_header;

  /**
   * Function we need to call whenever the event loop's
   * socket set changed.
   */
  GNUNET_CURL_RescheduleCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;
};


/**
 * Initialise this library.  This function should be called before using any of
 * the following functions.
 *
 * @param cb function to call when rescheduling is required
 * @param cb_cls closure for @a cb
 * @return library context
 */
struct GNUNET_CURL_Context *
GNUNET_CURL_init (GNUNET_CURL_RescheduleCallback cb,
                  void *cb_cls)
{
  struct GNUNET_CURL_Context *ctx;
  CURLM *multi;
  CURLSH *share;

  if (curl_fail)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Curl was not initialised properly\n");
    return NULL;
  }
  if (NULL == (multi = curl_multi_init ()))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to create a Curl multi handle\n");
    return NULL;
  }
  if (NULL == (share = curl_share_init ()))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to create a Curl share handle\n");
    return NULL;
  }
  ctx = GNUNET_new (struct GNUNET_CURL_Context);
  ctx->cb = cb;
  ctx->cb_cls = cb_cls;
  ctx->multi = multi;
  ctx->share = share;
  GNUNET_assert (NULL != (ctx->json_header =
                          curl_slist_append (NULL,
                                             "Content-Type: application/json")));
  return ctx;
}


/**
 * Callback used when downloading the reply to an HTTP request.
 * Just appends all of the data to the `buf` in the
 * `struct DownloadBuffer` for further processing. The size of
 * the download is limited to #GNUNET_MAX_MALLOC_CHECKED, if
 * the download exceeds this size, we abort with an error.
 *
 * @param bufptr data downloaded via HTTP
 * @param size size of an item in @a bufptr
 * @param nitems number of items in @a bufptr
 * @param cls the `struct DownloadBuffer`
 * @return number of bytes processed from @a bufptr
 */
static size_t
download_cb (char *bufptr,
             size_t size,
             size_t nitems,
             void *cls)
{
  struct DownloadBuffer *db = cls;
  size_t msize;
  void *buf;

  if (0 == size * nitems)
  {
    /* Nothing (left) to do */
    return 0;
  }
  msize = size * nitems;
  if ( (msize + db->buf_size) >= GNUNET_MAX_MALLOC_CHECKED)
  {
    db->eno = ENOMEM;
    return 0; /* signals an error to curl */
  }
  db->buf = GNUNET_realloc (db->buf,
                            db->buf_size + msize);
  buf = db->buf + db->buf_size;
  memcpy (buf, bufptr, msize);
  db->buf_size += msize;
  return msize;
}


/**
 * Schedule a CURL request to be executed and call the given @a jcc
 * upon its completion.  Note that the context will make use of the
 * CURLOPT_PRIVATE facility of the CURL @a eh.
 *
 * This function modifies the CURL handle to add the
 * "Content-Type: application/json" header if @a add_json is set.
 *
 * @param ctx context to execute the job in
 * @param eh curl easy handle for the request, will
 *           be executed AND cleaned up
 * @param add_json add "application/json" content type header
 * @param jcc callback to invoke upon completion
 * @param jcc_cls closure for @a jcc
 * @return NULL on error (in this case, @eh is still released!)
 */
struct GNUNET_CURL_Job *
GNUNET_CURL_job_add (struct GNUNET_CURL_Context *ctx,
                     CURL *eh,
                     int add_json,
                     GNUNET_CURL_JobCompletionCallback jcc,
                     void *jcc_cls)
{
  struct GNUNET_CURL_Job *job;

  if (GNUNET_YES == add_json)
    if (CURLE_OK !=
        curl_easy_setopt (eh,
                          CURLOPT_HTTPHEADER,
                          ctx->json_header))
    {
      GNUNET_break (0);
      curl_easy_cleanup (eh);
      return NULL;
    }

  job = GNUNET_new (struct GNUNET_CURL_Job);
  if ( (CURLE_OK !=
        curl_easy_setopt (eh,
                          CURLOPT_PRIVATE,
                          job)) ||
       (CURLE_OK !=
        curl_easy_setopt (eh,
                          CURLOPT_WRITEFUNCTION,
                          &download_cb)) ||
       (CURLE_OK !=
        curl_easy_setopt (eh,
                          CURLOPT_WRITEDATA,
                          &job->db)) ||
       (CURLE_OK !=
        curl_easy_setopt (eh,
                          CURLOPT_SHARE,
                          ctx->share)) ||
       (CURLM_OK !=
        curl_multi_add_handle (ctx->multi,
                               eh)) )
  {
    GNUNET_break (0);
    GNUNET_free (job);
    curl_easy_cleanup (eh);
    return NULL;
  }

  job->easy_handle = eh;
  job->ctx = ctx;
  job->jcc = jcc;
  job->jcc_cls = jcc_cls;
  GNUNET_CONTAINER_DLL_insert (ctx->jobs_head,
                               ctx->jobs_tail,
                               job);
  ctx->cb (ctx->cb_cls);
  return job;
}


/**
 * Cancel a job.  Must only be called before the job completion
 * callback is called for the respective job.
 *
 * @param job job to cancel
 */
void
GNUNET_CURL_job_cancel (struct GNUNET_CURL_Job *job)
{
  struct GNUNET_CURL_Context *ctx = job->ctx;

  GNUNET_CONTAINER_DLL_remove (ctx->jobs_head,
                               ctx->jobs_tail,
                               job);
  GNUNET_break (CURLM_OK ==
                curl_multi_remove_handle (ctx->multi,
                                          job->easy_handle));
  curl_easy_cleanup (job->easy_handle);
  GNUNET_free_non_null (job->db.buf);
  GNUNET_free (job);
}


/**
 * Obtain information about the final result about the
 * HTTP download. If the download was successful, parses
 * the JSON in the @a db and returns it. Also returns
 * the HTTP @a response_code.  If the download failed,
 * the return value is NULL.  The response code is set
 * in any case, on download errors to zero.
 *
 * Calling this function also cleans up @a db.
 *
 * @param db download buffer
 * @param eh CURL handle (to get the response code)
 * @param[out] response_code set to the HTTP response code
 *             (or zero if we aborted the download, i.e.
 *              because the response was too big, or if
 *              the JSON we received was malformed).
 * @return NULL if downloading a JSON reply failed
 */
static json_t *
download_get_result (struct DownloadBuffer *db,
                     CURL *eh,
                     long *response_code)
{
  json_t *json;
  json_error_t error;
  char *ct;

  if ( (CURLE_OK !=
        curl_easy_getinfo (eh,
                           CURLINFO_CONTENT_TYPE,
                           &ct)) ||
       (NULL == ct) ||
       (0 != strcasecmp (ct,
                         "application/json")) )
  {
    /* No content type or explicitly not JSON, refuse to parse
       (but keep response code) */
    if (CURLE_OK !=
        curl_easy_getinfo (eh,
                           CURLINFO_RESPONSE_CODE,
                           response_code))
    {
      /* unexpected error... */
      GNUNET_break (0);
      *response_code = 0;
    }
    return NULL;
  }

  json = NULL;
  if (0 == db->eno)
  {
    json = json_loadb (db->buf,
                       db->buf_size,
                       JSON_REJECT_DUPLICATES | JSON_DISABLE_EOF_CHECK,
                       &error);
    if (NULL == json)
    {
      JSON_WARN (error);
      *response_code = 0;
    }
  }
  GNUNET_free_non_null (db->buf);
  db->buf = NULL;
  db->buf_size = 0;
  if (NULL != json)
  {
    if (CURLE_OK !=
        curl_easy_getinfo (eh,
                           CURLINFO_RESPONSE_CODE,
                           response_code))
    {
      /* unexpected error... */
      GNUNET_break (0);
      *response_code = 0;
    }
  }
  return json;
}


/**
 * Run the main event loop for the Taler interaction.
 *
 * @param ctx the library context
 */
void
GNUNET_CURL_perform (struct GNUNET_CURL_Context *ctx)
{
  CURLMsg *cmsg;
  struct GNUNET_CURL_Job *job;
  int n_running;
  int n_completed;
  long response_code;
  json_t *j;

  (void) curl_multi_perform (ctx->multi,
                             &n_running);
  while (NULL != (cmsg = curl_multi_info_read (ctx->multi,
                                               &n_completed)))
  {
    /* Only documented return value is CURLMSG_DONE */
    GNUNET_break (CURLMSG_DONE == cmsg->msg);
    GNUNET_assert (CURLE_OK ==
                   curl_easy_getinfo (cmsg->easy_handle,
                                      CURLINFO_PRIVATE,
                                      (char **) &job));
    GNUNET_assert (job->ctx == ctx);
    j = download_get_result (&job->db,
                             job->easy_handle,
                             &response_code);
    job->jcc (job->jcc_cls,
              response_code,
              j);
    json_decref (j);
    GNUNET_CURL_job_cancel (job);
  }
}


/**
 * Obtain the information for a select() call to wait until
 * #GNUNET_CURL_perform() is ready again.  Note that calling
 * any other GNUNET_CURL-API may also imply that the library
 * is again ready for #GNUNET_CURL_perform().
 *
 * Basically, a client should use this API to prepare for select(),
 * then block on select(), then call #GNUNET_CURL_perform() and then
 * start again until the work with the context is done.
 *
 * This function will NOT zero out the sets and assumes that @a max_fd
 * and @a timeout are already set to minimal applicable values.  It is
 * safe to give this API FD-sets and @a max_fd and @a timeout that are
 * already initialized to some other descriptors that need to go into
 * the select() call.
 *
 * @param ctx context to get the event loop information for
 * @param read_fd_set will be set for any pending read operations
 * @param write_fd_set will be set for any pending write operations
 * @param except_fd_set is here because curl_multi_fdset() has this argument
 * @param max_fd set to the highest FD included in any set;
 *        if the existing sets have no FDs in it, the initial
 *        value should be "-1". (Note that `max_fd + 1` will need
 *        to be passed to select().)
 * @param timeout set to the timeout in milliseconds (!); -1 means
 *        no timeout (NULL, blocking forever is OK), 0 means to
 *        proceed immediately with #GNUNET_CURL_perform().
 */
void
GNUNET_CURL_get_select_info (struct GNUNET_CURL_Context *ctx,
                             fd_set *read_fd_set,
                             fd_set *write_fd_set,
                             fd_set *except_fd_set,
                             int *max_fd,
                             long *timeout)
{
  long to;
  int m;

  m = -1;
  GNUNET_assert (CURLM_OK ==
                 curl_multi_fdset (ctx->multi,
                                   read_fd_set,
                                   write_fd_set,
                                   except_fd_set,
                                   &m));
  to = *timeout;
  *max_fd = GNUNET_MAX (m, *max_fd);
  GNUNET_assert (CURLM_OK ==
                 curl_multi_timeout (ctx->multi,
                                     &to));

  /* Only if what we got back from curl is smaller than what we
     already had (-1 == infinity!), then update timeout */
  if ( (to < *timeout) &&
       (-1 != to) )
    *timeout = to;
  if ( (-1 == (*timeout)) &&
       (NULL != ctx->jobs_head) )
    *timeout = to;
}


/**
 * Cleanup library initialisation resources.  This function should be called
 * after using this library to cleanup the resources occupied during library's
 * initialisation.
 *
 * @param ctx the library context
 */
void
GNUNET_CURL_fini (struct GNUNET_CURL_Context *ctx)
{
  /* all jobs must have been cancelled at this time, assert this */
  GNUNET_assert (NULL == ctx->jobs_head);
  curl_share_cleanup (ctx->share);
  curl_multi_cleanup (ctx->multi);
  curl_slist_free_all (ctx->json_header);
  GNUNET_free (ctx);
}


/**
 * Initial global setup logic, specifically runs the Curl setup.
 */
__attribute__ ((constructor))
void
GNUNET_CURL_constructor__ (void)
{
  CURLcode ret;

  if (CURLE_OK != (ret = curl_global_init (CURL_GLOBAL_DEFAULT)))
  {
    CURL_STRERROR (GNUNET_ERROR_TYPE_ERROR,
                   "curl_global_init",
                   ret);
    curl_fail = 1;
  }
}


/**
 * Cleans up after us, specifically runs the Curl cleanup.
 */
__attribute__ ((destructor))
void
GNUNET_CURL_destructor__ (void)
{
  if (curl_fail)
    return;
  curl_global_cleanup ();
}

/* end of curl.c */