block/curl.c

   1 /*
   2  * QEMU Block driver for CURL images
   3  *
   4  * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 #include "qemu-common.h"
  25 #include "block/block_int.h"
  26 #include <curl/curl.h>
  27
  28 // #define DEBUG
  29 // #define DEBUG_VERBOSE
  30
  31 #ifdef DEBUG_CURL
  32 #define DPRINTF(fmt, ...) do { printf(fmt, ## __VA_ARGS__); } while (0)
  33 #else
  34 #define DPRINTF(fmt, ...) do { } while (0)
  35 #endif
  36
  37 #define PROTOCOLS (CURLPROTO_HTTP | CURLPROTO_HTTPS | \
  38                    CURLPROTO_FTP | CURLPROTO_FTPS | \
  39                    CURLPROTO_TFTP)
  40
  41 #define CURL_NUM_STATES 8
  42 #define CURL_NUM_ACB    8
  43 #define SECTOR_SIZE     512
  44 #define READ_AHEAD_SIZE (256 * 1024)
  45
  46 #define FIND_RET_NONE   0
  47 #define FIND_RET_OK     1
  48 #define FIND_RET_WAIT   2
  49
  50 struct BDRVCURLState;
  51
  52 typedef struct CURLAIOCB {
  53     BlockDriverAIOCB common;
  54     QEMUBH *bh;
  55     QEMUIOVector *qiov;
  56
  57     int64_t sector_num;
  58     int nb_sectors;
  59
  60     size_t start;
  61     size_t end;
  62 } CURLAIOCB;
  63
  64 typedef struct CURLState
  65 {
  66     struct BDRVCURLState *s;
  67     CURLAIOCB *acb[CURL_NUM_ACB];
  68     CURL *curl;
  69     char *orig_buf;
  70     size_t buf_start;
  71     size_t buf_off;
  72     size_t buf_len;
  73     char range[128];
  74     char errmsg[CURL_ERROR_SIZE];
  75     char in_use;
  76 } CURLState;
  77
  78 typedef struct BDRVCURLState {
  79     CURLM *multi;
  80     size_t len;
  81     CURLState states[CURL_NUM_STATES];
  82     char *url;
  83     size_t readahead_size;
  84     bool accept_range;
  85 } BDRVCURLState;
  86
  87 static void curl_clean_state(CURLState *s);
  88 static void curl_multi_do(void *arg);
  89
  90 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
  91                         void *s, void *sp)
  92 {
  93     DPRINTF("CURL (AIO): Sock action %d on fd %d\n", action, fd);
  94     switch (action) {
  95         case CURL_POLL_IN:
  96             qemu_aio_set_fd_handler(fd, curl_multi_do, NULL, s);
  97             break;
  98         case CURL_POLL_OUT:
  99             qemu_aio_set_fd_handler(fd, NULL, curl_multi_do, s);
 100             break;
 101         case CURL_POLL_INOUT:
 102             qemu_aio_set_fd_handler(fd, curl_multi_do, curl_multi_do, s);
 103             break;
 104         case CURL_POLL_REMOVE:
 105             qemu_aio_set_fd_handler(fd, NULL, NULL, NULL);
 106             break;
 107     }
 108
 109     return 0;
 110 }
 111
 112 static size_t curl_header_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 113 {
 114     BDRVCURLState *s = opaque;
 115     size_t realsize = size * nmemb;
 116     const char *accept_line = "Accept-Ranges: bytes";
 117
 118     if (realsize >= strlen(accept_line)
 119         && strncmp((char *)ptr, accept_line, strlen(accept_line)) == 0) {
 120         s->accept_range = true;
 121     }
 122
 123     return realsize;
 124 }
 125
 126 static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 127 {
 128     CURLState *s = ((CURLState*)opaque);
 129     size_t realsize = size * nmemb;
 130     int i;
 131
 132     DPRINTF("CURL: Just reading %zd bytes\n", realsize);
 133
 134     if (!s || !s->orig_buf)
 135         goto read_end;
 136
 137     memcpy(s->orig_buf + s->buf_off, ptr, realsize);
 138     s->buf_off += realsize;
 139
 140     for(i=0; i<CURL_NUM_ACB; i++) {
 141         CURLAIOCB *acb = s->acb[i];
 142
 143         if (!acb)
 144             continue;
 145
 146         if ((s->buf_off >= acb->end)) {
 147             qemu_iovec_from_buf(acb->qiov, 0, s->orig_buf + acb->start,
 148                                 acb->end - acb->start);
 149             acb->common.cb(acb->common.opaque, 0);
 150             qemu_aio_release(acb);
 151             s->acb[i] = NULL;
 152         }
 153     }
 154
 155 read_end:
 156     return realsize;
 157 }
 158
 159 static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
 160                          CURLAIOCB *acb)
 161 {
 162     int i;
 163     size_t end = start + len;
 164
 165     for (i=0; i<CURL_NUM_STATES; i++) {
 166         CURLState *state = &s->states[i];
 167         size_t buf_end = (state->buf_start + state->buf_off);
 168         size_t buf_fend = (state->buf_start + state->buf_len);
 169
 170         if (!state->orig_buf)
 171             continue;
 172         if (!state->buf_off)
 173             continue;
 174
 175         // Does the existing buffer cover our section?
 176         if ((start >= state->buf_start) &&
 177             (start <= buf_end) &&
 178             (end >= state->buf_start) &&
 179             (end <= buf_end))
 180         {
 181             char *buf = state->orig_buf + (start - state->buf_start);
 182
 183             qemu_iovec_from_buf(acb->qiov, 0, buf, len);
 184             acb->common.cb(acb->common.opaque, 0);
 185
 186             return FIND_RET_OK;
 187         }
 188
 189         // Wait for unfinished chunks
 190         if ((start >= state->buf_start) &&
 191             (start <= buf_fend) &&
 192             (end >= state->buf_start) &&
 193             (end <= buf_fend))
 194         {
 195             int j;
 196
 197             acb->start = start - state->buf_start;
 198             acb->end = acb->start + len;
 199
 200             for (j=0; j<CURL_NUM_ACB; j++) {
 201                 if (!state->acb[j]) {
 202                     state->acb[j] = acb;
 203                     return FIND_RET_WAIT;
 204                 }
 205             }
 206         }
 207     }
 208
 209     return FIND_RET_NONE;
 210 }
 211
 212 static void curl_multi_do(void *arg)
 213 {
 214     BDRVCURLState *s = (BDRVCURLState *)arg;
 215     int running;
 216     int r;
 217     int msgs_in_queue;
 218
 219     if (!s->multi)
 220         return;
 221
 222     do {
 223         r = curl_multi_socket_all(s->multi, &running);
 224     } while(r == CURLM_CALL_MULTI_PERFORM);
 225
 226     /* Try to find done transfers, so we can free the easy
 227      * handle again. */
 228     do {
 229         CURLMsg *msg;
 230         msg = curl_multi_info_read(s->multi, &msgs_in_queue);
 231
 232         if (!msg)
 233             break;
 234         if (msg->msg == CURLMSG_NONE)
 235             break;
 236
 237         switch (msg->msg) {
 238             case CURLMSG_DONE:
 239             {
 240                 CURLState *state = NULL;
 241                 curl_easy_getinfo(msg->easy_handle, CURLINFO_PRIVATE, (char**)&state);
 242
 243                 /* ACBs for successful messages get completed in curl_read_cb */
 244                 if (msg->data.result != CURLE_OK) {
 245                     int i;
 246                     for (i = 0; i < CURL_NUM_ACB; i++) {
 247                         CURLAIOCB *acb = state->acb[i];
 248
 249                         if (acb == NULL) {
 250                             continue;
 251                         }
 252
 253                         acb->common.cb(acb->common.opaque, -EIO);
 254                         qemu_aio_release(acb);
 255                         state->acb[i] = NULL;
 256                     }
 257                 }
 258
 259                 curl_clean_state(state);
 260                 break;
 261             }
 262             default:
 263                 msgs_in_queue = 0;
 264                 break;
 265         }
 266     } while(msgs_in_queue);
 267 }
 268
 269 static CURLState *curl_init_state(BDRVCURLState *s)
 270 {
 271     CURLState *state = NULL;
 272     int i, j;
 273
 274     do {
 275         for (i=0; i<CURL_NUM_STATES; i++) {
 276             for (j=0; j<CURL_NUM_ACB; j++)
 277                 if (s->states[i].acb[j])
 278                     continue;
 279             if (s->states[i].in_use)
 280                 continue;
 281
 282             state = &s->states[i];
 283             state->in_use = 1;
 284             break;
 285         }
 286         if (!state) {
 287             g_usleep(100);
 288             curl_multi_do(s);
 289         }
 290     } while(!state);
 291
 292     if (state->curl)
 293         goto has_curl;
 294
 295     state->curl = curl_easy_init();
 296     if (!state->curl)
 297         return NULL;
 298     curl_easy_setopt(state->curl, CURLOPT_URL, s->url);
 299     curl_easy_setopt(state->curl, CURLOPT_TIMEOUT, 5);
 300     curl_easy_setopt(state->curl, CURLOPT_WRITEFUNCTION, (void *)curl_read_cb);
 301     curl_easy_setopt(state->curl, CURLOPT_WRITEDATA, (void *)state);
 302     curl_easy_setopt(state->curl, CURLOPT_PRIVATE, (void *)state);
 303     curl_easy_setopt(state->curl, CURLOPT_AUTOREFERER, 1);
 304     curl_easy_setopt(state->curl, CURLOPT_FOLLOWLOCATION, 1);
 305     curl_easy_setopt(state->curl, CURLOPT_NOSIGNAL, 1);
 306     curl_easy_setopt(state->curl, CURLOPT_ERRORBUFFER, state->errmsg);
 307     curl_easy_setopt(state->curl, CURLOPT_FAILONERROR, 1);
 308
 309     /* Restrict supported protocols to avoid security issues in the more
 310      * obscure protocols.  For example, do not allow POP3/SMTP/IMAP see
 311      * CVE-2013-0249.
 312      *
 313      * Restricting protocols is only supported from 7.19.4 upwards.
 314      */
 315 #if LIBCURL_VERSION_NUM >= 0x071304
 316     curl_easy_setopt(state->curl, CURLOPT_PROTOCOLS, PROTOCOLS);
 317     curl_easy_setopt(state->curl, CURLOPT_REDIR_PROTOCOLS, PROTOCOLS);
 318 #endif
 319
 320 #ifdef DEBUG_VERBOSE
 321     curl_easy_setopt(state->curl, CURLOPT_VERBOSE, 1);
 322 #endif
 323
 324 has_curl:
 325
 326     state->s = s;
 327
 328     return state;
 329 }
 330
 331 static void curl_clean_state(CURLState *s)
 332 {
 333     if (s->s->multi)
 334         curl_multi_remove_handle(s->s->multi, s->curl);
 335     s->in_use = 0;
 336 }
 337
 338 static void curl_parse_filename(const char *filename, QDict *options,
 339                                 Error **errp)
 340 {
 341
 342     #define RA_OPTSTR ":readahead="
 343     char *file;
 344     char *ra;
 345     const char *ra_val;
 346     int parse_state = 0;
 347
 348     file = g_strdup(filename);
 349
 350     /* Parse a trailing ":readahead=#:" param, if present. */
 351     ra = file + strlen(file) - 1;
 352     while (ra >= file) {
 353         if (parse_state == 0) {
 354             if (*ra == ':') {
 355                 parse_state++;
 356             } else {
 357                 break;
 358             }
 359         } else if (parse_state == 1) {
 360             if (*ra > '9' || *ra < '0') {
 361                 char *opt_start = ra - strlen(RA_OPTSTR) + 1;
 362                 if (opt_start > file &&
 363                     strncmp(opt_start, RA_OPTSTR, strlen(RA_OPTSTR)) == 0) {
 364                     ra_val = ra + 1;
 365                     ra -= strlen(RA_OPTSTR) - 1;
 366                     *ra = '\0';
 367                     qdict_put(options, "readahead", qstring_from_str(ra_val));
 368                 }
 369                 break;
 370             }
 371         }
 372         ra--;
 373     }
 374
 375     qdict_put(options, "url", qstring_from_str(file));
 376
 377     g_free(file);
 378 }
 379
 380 static QemuOptsList runtime_opts = {
 381     .name = "curl",
 382     .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
 383     .desc = {
 384         {
 385             .name = "url",
 386             .type = QEMU_OPT_STRING,
 387             .help = "URL to open",
 388         },
 389         {
 390             .name = "readahead",
 391             .type = QEMU_OPT_SIZE,
 392             .help = "Readahead size",
 393         },
 394         { /* end of list */ }
 395     },
 396 };
 397
 398 static int curl_open(BlockDriverState *bs, QDict *options, int flags,
 399                      Error **errp)
 400 {
 401     BDRVCURLState *s = bs->opaque;
 402     CURLState *state = NULL;
 403     QemuOpts *opts;
 404     Error *local_err = NULL;
 405     const char *file;
 406     double d;
 407
 408     static int inited = 0;
 409
 410     if (flags & BDRV_O_RDWR) {
 411         qerror_report(ERROR_CLASS_GENERIC_ERROR,
 412                       "curl block device does not support writes");
 413         return -EROFS;
 414     }
 415
 416     opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
 417     qemu_opts_absorb_qdict(opts, options, &local_err);
 418     if (error_is_set(&local_err)) {
 419         qerror_report_err(local_err);
 420         error_free(local_err);
 421         goto out_noclean;
 422     }
 423
 424     s->readahead_size = qemu_opt_get_size(opts, "readahead", READ_AHEAD_SIZE);
 425     if ((s->readahead_size & 0x1ff) != 0) {
 426         fprintf(stderr, "HTTP_READAHEAD_SIZE %zd is not a multiple of 512\n",
 427                 s->readahead_size);
 428         goto out_noclean;
 429     }
 430
 431     file = qemu_opt_get(opts, "url");
 432     if (file == NULL) {
 433         qerror_report(ERROR_CLASS_GENERIC_ERROR, "curl block driver requires "
 434                       "an 'url' option");
 435         goto out_noclean;
 436     }
 437
 438     if (!inited) {
 439         curl_global_init(CURL_GLOBAL_ALL);
 440         inited = 1;
 441     }
 442
 443     DPRINTF("CURL: Opening %s\n", file);
 444     s->url = g_strdup(file);
 445     state = curl_init_state(s);
 446     if (!state)
 447         goto out_noclean;
 448
 449     // Get file size
 450
 451     s->accept_range = false;
 452     curl_easy_setopt(state->curl, CURLOPT_NOBODY, 1);
 453     curl_easy_setopt(state->curl, CURLOPT_HEADERFUNCTION,
 454                      curl_header_cb);
 455     curl_easy_setopt(state->curl, CURLOPT_HEADERDATA, s);
 456     if (curl_easy_perform(state->curl))
 457         goto out;
 458     curl_easy_getinfo(state->curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &d);
 459     if (d)
 460         s->len = (size_t)d;
 461     else if(!s->len)
 462         goto out;
 463     if ((!strncasecmp(s->url, "http://", strlen("http://"))
 464         || !strncasecmp(s->url, "https://", strlen("https://")))
 465         && !s->accept_range) {
 466         pstrcpy(state->errmsg, CURL_ERROR_SIZE,
 467                 "Server does not support 'range' (byte ranges).");
 468         goto out;
 469     }
 470     DPRINTF("CURL: Size = %zd\n", s->len);
 471
 472     curl_clean_state(state);
 473     curl_easy_cleanup(state->curl);
 474     state->curl = NULL;
 475
 476     // Now we know the file exists and its size, so let's
 477     // initialize the multi interface!
 478
 479     s->multi = curl_multi_init();
 480     curl_multi_setopt(s->multi, CURLMOPT_SOCKETDATA, s);
 481     curl_multi_setopt(s->multi, CURLMOPT_SOCKETFUNCTION, curl_sock_cb);
 482     curl_multi_do(s);
 483
 484     qemu_opts_del(opts);
 485     return 0;
 486
 487 out:
 488     fprintf(stderr, "CURL: Error opening file: %s\n", state->errmsg);
 489     curl_easy_cleanup(state->curl);
 490     state->curl = NULL;
 491 out_noclean:
 492     g_free(s->url);
 493     qemu_opts_del(opts);
 494     return -EINVAL;
 495 }
 496
 497 static void curl_aio_cancel(BlockDriverAIOCB *blockacb)
 498 {
 499     // Do we have to implement canceling? Seems to work without...
 500 }
 501
 502 static const AIOCBInfo curl_aiocb_info = {
 503     .aiocb_size         = sizeof(CURLAIOCB),
 504     .cancel             = curl_aio_cancel,
 505 };
 506
 507
 508 static void curl_readv_bh_cb(void *p)
 509 {
 510     CURLState *state;
 511
 512     CURLAIOCB *acb = p;
 513     BDRVCURLState *s = acb->common.bs->opaque;
 514
 515     qemu_bh_delete(acb->bh);
 516     acb->bh = NULL;
 517
 518     size_t start = acb->sector_num * SECTOR_SIZE;
 519     size_t end;
 520
 521     // In case we have the requested data already (e.g. read-ahead),
 522     // we can just call the callback and be done.
 523     switch (curl_find_buf(s, start, acb->nb_sectors * SECTOR_SIZE, acb)) {
 524         case FIND_RET_OK:
 525             qemu_aio_release(acb);
 526             // fall through
 527         case FIND_RET_WAIT:
 528             return;
 529         default:
 530             break;
 531     }
 532
 533     // No cache found, so let's start a new request
 534     state = curl_init_state(s);
 535     if (!state) {
 536         acb->common.cb(acb->common.opaque, -EIO);
 537         qemu_aio_release(acb);
 538         return;
 539     }
 540
 541     acb->start = 0;
 542     acb->end = (acb->nb_sectors * SECTOR_SIZE);
 543
 544     state->buf_off = 0;
 545     if (state->orig_buf)
 546         g_free(state->orig_buf);
 547     state->buf_start = start;
 548     state->buf_len = acb->end + s->readahead_size;
 549     end = MIN(start + state->buf_len, s->len) - 1;
 550     state->orig_buf = g_malloc(state->buf_len);
 551     state->acb[0] = acb;
 552
 553     snprintf(state->range, 127, "%zd-%zd", start, end);
 554     DPRINTF("CURL (AIO): Reading %d at %zd (%s)\n",
 555             (acb->nb_sectors * SECTOR_SIZE), start, state->range);
 556     curl_easy_setopt(state->curl, CURLOPT_RANGE, state->range);
 557
 558     curl_multi_add_handle(s->multi, state->curl);
 559     curl_multi_do(s);
 560
 561 }
 562
 563 static BlockDriverAIOCB *curl_aio_readv(BlockDriverState *bs,
 564         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
 565         BlockDriverCompletionFunc *cb, void *opaque)
 566 {
 567     CURLAIOCB *acb;
 568
 569     acb = qemu_aio_get(&curl_aiocb_info, bs, cb, opaque);
 570
 571     acb->qiov = qiov;
 572     acb->sector_num = sector_num;
 573     acb->nb_sectors = nb_sectors;
 574
 575     acb->bh = qemu_bh_new(curl_readv_bh_cb, acb);
 576     qemu_bh_schedule(acb->bh);
 577     return &acb->common;
 578 }
 579
 580 static void curl_close(BlockDriverState *bs)
 581 {
 582     BDRVCURLState *s = bs->opaque;
 583     int i;
 584
 585     DPRINTF("CURL: Close\n");
 586     for (i=0; i<CURL_NUM_STATES; i++) {
 587         if (s->states[i].in_use)
 588             curl_clean_state(&s->states[i]);
 589         if (s->states[i].curl) {
 590             curl_easy_cleanup(s->states[i].curl);
 591             s->states[i].curl = NULL;
 592         }
 593         if (s->states[i].orig_buf) {
 594             g_free(s->states[i].orig_buf);
 595             s->states[i].orig_buf = NULL;
 596         }
 597     }
 598     if (s->multi)
 599         curl_multi_cleanup(s->multi);
 600     g_free(s->url);
 601 }
 602
 603 static int64_t curl_getlength(BlockDriverState *bs)
 604 {
 605     BDRVCURLState *s = bs->opaque;
 606     return s->len;
 607 }
 608
 609 static BlockDriver bdrv_http = {
 610     .format_name            = "http",
 611     .protocol_name          = "http",
 612
 613     .instance_size          = sizeof(BDRVCURLState),
 614     .bdrv_parse_filename    = curl_parse_filename,
 615     .bdrv_file_open         = curl_open,
 616     .bdrv_close             = curl_close,
 617     .bdrv_getlength         = curl_getlength,
 618
 619     .bdrv_aio_readv         = curl_aio_readv,
 620 };
 621
 622 static BlockDriver bdrv_https = {
 623     .format_name            = "https",
 624     .protocol_name          = "https",
 625
 626     .instance_size          = sizeof(BDRVCURLState),
 627     .bdrv_parse_filename    = curl_parse_filename,
 628     .bdrv_file_open         = curl_open,
 629     .bdrv_close             = curl_close,
 630     .bdrv_getlength         = curl_getlength,
 631
 632     .bdrv_aio_readv         = curl_aio_readv,
 633 };
 634
 635 static BlockDriver bdrv_ftp = {
 636     .format_name            = "ftp",
 637     .protocol_name          = "ftp",
 638
 639     .instance_size          = sizeof(BDRVCURLState),
 640     .bdrv_parse_filename    = curl_parse_filename,
 641     .bdrv_file_open         = curl_open,
 642     .bdrv_close             = curl_close,
 643     .bdrv_getlength         = curl_getlength,
 644
 645     .bdrv_aio_readv         = curl_aio_readv,
 646 };
 647
 648 static BlockDriver bdrv_ftps = {
 649     .format_name            = "ftps",
 650     .protocol_name          = "ftps",
 651
 652     .instance_size          = sizeof(BDRVCURLState),
 653     .bdrv_parse_filename    = curl_parse_filename,
 654     .bdrv_file_open         = curl_open,
 655     .bdrv_close             = curl_close,
 656     .bdrv_getlength         = curl_getlength,
 657
 658     .bdrv_aio_readv         = curl_aio_readv,
 659 };
 660
 661 static BlockDriver bdrv_tftp = {
 662     .format_name            = "tftp",
 663     .protocol_name          = "tftp",
 664
 665     .instance_size          = sizeof(BDRVCURLState),
 666     .bdrv_parse_filename    = curl_parse_filename,
 667     .bdrv_file_open         = curl_open,
 668     .bdrv_close             = curl_close,
 669     .bdrv_getlength         = curl_getlength,
 670
 671     .bdrv_aio_readv         = curl_aio_readv,
 672 };
 673
 674 static void curl_block_init(void)
 675 {
 676     bdrv_register(&bdrv_http);
 677     bdrv_register(&bdrv_https);
 678     bdrv_register(&bdrv_ftp);
 679     bdrv_register(&bdrv_ftps);
 680     bdrv_register(&bdrv_tftp);
 681 }
 682
 683 block_init(curl_block_init);