nbd/client.c

   1 /*
   2  *  Copyright (C) 2016-2017 Red Hat, Inc.
   3  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   4  *
   5  *  Network Block Device Client Side
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; under version 2 of the License.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "qemu/osdep.h"
  21 #include "qapi/error.h"
  22 #include "trace.h"
  23 #include "nbd-internal.h"
  24
  25 /* Definitions for opaque data types */
  26
  27 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  28
  29 /* That's all folks */
  30
  31 /* Basic flow for negotiation
  32
  33    Server         Client
  34    Negotiate
  35
  36    or
  37
  38    Server         Client
  39    Negotiate #1
  40                   Option
  41    Negotiate #2
  42
  43    ----
  44
  45    followed by
  46
  47    Server         Client
  48                   Request
  49    Response
  50                   Request
  51    Response
  52                   ...
  53    ...
  54                   Request (type == 2)
  55
  56 */
  57
  58 /* Send an option request.
  59  *
  60  * The request is for option @opt, with @data containing @len bytes of
  61  * additional payload for the request (@len may be -1 to treat @data as
  62  * a C string; and @data may be NULL if @len is 0).
  63  * Return 0 if successful, -1 with errp set if it is impossible to
  64  * continue. */
  65 static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
  66                                    uint32_t len, const char *data,
  67                                    Error **errp)
  68 {
  69     NBDOption req;
  70     QEMU_BUILD_BUG_ON(sizeof(req) != 16);
  71
  72     if (len == -1) {
  73         req.length = len = strlen(data);
  74     }
  75     trace_nbd_send_option_request(opt, nbd_opt_lookup(opt), len);
  76
  77     stq_be_p(&req.magic, NBD_OPTS_MAGIC);
  78     stl_be_p(&req.option, opt);
  79     stl_be_p(&req.length, len);
  80
  81     if (nbd_write(ioc, &req, sizeof(req), errp) < 0) {
  82         error_prepend(errp, "Failed to send option request header: ");
  83         return -1;
  84     }
  85
  86     if (len && nbd_write(ioc, (char *) data, len, errp) < 0) {
  87         error_prepend(errp, "Failed to send option request data: ");
  88         return -1;
  89     }
  90
  91     return 0;
  92 }
  93
  94 /* Send NBD_OPT_ABORT as a courtesy to let the server know that we are
  95  * not going to attempt further negotiation. */
  96 static void nbd_send_opt_abort(QIOChannel *ioc)
  97 {
  98     /* Technically, a compliant server is supposed to reply to us; but
  99      * older servers disconnected instead. At any rate, we're allowed
 100      * to disconnect without waiting for the server reply, so we don't
 101      * even care if the request makes it to the server, let alone
 102      * waiting around for whether the server replies. */
 103     nbd_send_option_request(ioc, NBD_OPT_ABORT, 0, NULL, NULL);
 104 }
 105
 106
 107 /* Receive the header of an option reply, which should match the given
 108  * opt.  Read through the length field, but NOT the length bytes of
 109  * payload. Return 0 if successful, -1 with errp set if it is
 110  * impossible to continue. */
 111 static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
 112                                     NBDOptionReply *reply, Error **errp)
 113 {
 114     QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
 115     if (nbd_read(ioc, reply, sizeof(*reply), errp) < 0) {
 116         error_prepend(errp, "failed to read option reply: ");
 117         nbd_send_opt_abort(ioc);
 118         return -1;
 119     }
 120     be64_to_cpus(&reply->magic);
 121     be32_to_cpus(&reply->option);
 122     be32_to_cpus(&reply->type);
 123     be32_to_cpus(&reply->length);
 124
 125     trace_nbd_receive_option_reply(reply->option, nbd_opt_lookup(reply->option),
 126                                    reply->type, nbd_rep_lookup(reply->type),
 127                                    reply->length);
 128
 129     if (reply->magic != NBD_REP_MAGIC) {
 130         error_setg(errp, "Unexpected option reply magic");
 131         nbd_send_opt_abort(ioc);
 132         return -1;
 133     }
 134     if (reply->option != opt) {
 135         error_setg(errp, "Unexpected option type %x expected %x",
 136                    reply->option, opt);
 137         nbd_send_opt_abort(ioc);
 138         return -1;
 139     }
 140     return 0;
 141 }
 142
 143 /* If reply represents success, return 1 without further action.
 144  * If reply represents an error, consume the optional payload of
 145  * the packet on ioc.  Then return 0 for unsupported (so the client
 146  * can fall back to other approaches), or -1 with errp set for other
 147  * errors.
 148  */
 149 static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply,
 150                                 Error **errp)
 151 {
 152     char *msg = NULL;
 153     int result = -1;
 154
 155     if (!(reply->type & (1 << 31))) {
 156         return 1;
 157     }
 158
 159     if (reply->length) {
 160         if (reply->length > NBD_MAX_BUFFER_SIZE) {
 161             error_setg(errp, "server error %" PRIu32
 162                        " (%s) message is too long",
 163                        reply->type, nbd_rep_lookup(reply->type));
 164             goto cleanup;
 165         }
 166         msg = g_malloc(reply->length + 1);
 167         if (nbd_read(ioc, msg, reply->length, errp) < 0) {
 168             error_prepend(errp, "failed to read option error %" PRIu32
 169                           " (%s) message: ",
 170                           reply->type, nbd_rep_lookup(reply->type));
 171             goto cleanup;
 172         }
 173         msg[reply->length] = '\0';
 174     }
 175
 176     switch (reply->type) {
 177     case NBD_REP_ERR_UNSUP:
 178         trace_nbd_reply_err_unsup(reply->option, nbd_opt_lookup(reply->option));
 179         result = 0;
 180         goto cleanup;
 181
 182     case NBD_REP_ERR_POLICY:
 183         error_setg(errp, "Denied by server for option %" PRIu32 " (%s)",
 184                    reply->option, nbd_opt_lookup(reply->option));
 185         break;
 186
 187     case NBD_REP_ERR_INVALID:
 188         error_setg(errp, "Invalid parameters for option %" PRIu32 " (%s)",
 189                    reply->option, nbd_opt_lookup(reply->option));
 190         break;
 191
 192     case NBD_REP_ERR_PLATFORM:
 193         error_setg(errp, "Server lacks support for option %" PRIu32 " (%s)",
 194                    reply->option, nbd_opt_lookup(reply->option));
 195         break;
 196
 197     case NBD_REP_ERR_TLS_REQD:
 198         error_setg(errp, "TLS negotiation required before option %" PRIu32
 199                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
 200         break;
 201
 202     case NBD_REP_ERR_UNKNOWN:
 203         error_setg(errp, "Requested export not available");
 204         break;
 205
 206     case NBD_REP_ERR_SHUTDOWN:
 207         error_setg(errp, "Server shutting down before option %" PRIu32 " (%s)",
 208                    reply->option, nbd_opt_lookup(reply->option));
 209         break;
 210
 211     case NBD_REP_ERR_BLOCK_SIZE_REQD:
 212         error_setg(errp, "Server requires INFO_BLOCK_SIZE for option %" PRIu32
 213                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
 214         break;
 215
 216     default:
 217         error_setg(errp, "Unknown error code when asking for option %" PRIu32
 218                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
 219         break;
 220     }
 221
 222     if (msg) {
 223         error_append_hint(errp, "server reported: %s\n", msg);
 224     }
 225
 226  cleanup:
 227     g_free(msg);
 228     if (result < 0) {
 229         nbd_send_opt_abort(ioc);
 230     }
 231     return result;
 232 }
 233
 234 /* Process another portion of the NBD_OPT_LIST reply.  Set *@match if
 235  * the current reply matches @want or if the server does not support
 236  * NBD_OPT_LIST, otherwise leave @match alone.  Return 0 if iteration
 237  * is complete, positive if more replies are expected, or negative
 238  * with @errp set if an unrecoverable error occurred. */
 239 static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
 240                             Error **errp)
 241 {
 242     NBDOptionReply reply;
 243     uint32_t len;
 244     uint32_t namelen;
 245     char name[NBD_MAX_NAME_SIZE + 1];
 246     int error;
 247
 248     if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
 249         return -1;
 250     }
 251     error = nbd_handle_reply_err(ioc, &reply, errp);
 252     if (error <= 0) {
 253         /* The server did not support NBD_OPT_LIST, so set *match on
 254          * the assumption that any name will be accepted.  */
 255         *match = true;
 256         return error;
 257     }
 258     len = reply.length;
 259
 260     if (reply.type == NBD_REP_ACK) {
 261         if (len != 0) {
 262             error_setg(errp, "length too long for option end");
 263             nbd_send_opt_abort(ioc);
 264             return -1;
 265         }
 266         return 0;
 267     } else if (reply.type != NBD_REP_SERVER) {
 268         error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
 269                    reply.type, NBD_REP_SERVER);
 270         nbd_send_opt_abort(ioc);
 271         return -1;
 272     }
 273
 274     if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
 275         error_setg(errp, "incorrect option length %" PRIu32, len);
 276         nbd_send_opt_abort(ioc);
 277         return -1;
 278     }
 279     if (nbd_read(ioc, &namelen, sizeof(namelen), errp) < 0) {
 280         error_prepend(errp, "failed to read option name length: ");
 281         nbd_send_opt_abort(ioc);
 282         return -1;
 283     }
 284     namelen = be32_to_cpu(namelen);
 285     len -= sizeof(namelen);
 286     if (len < namelen) {
 287         error_setg(errp, "incorrect option name length");
 288         nbd_send_opt_abort(ioc);
 289         return -1;
 290     }
 291     if (namelen != strlen(want)) {
 292         if (nbd_drop(ioc, len, errp) < 0) {
 293             error_prepend(errp,
 294                           "failed to skip export name with wrong length: ");
 295             nbd_send_opt_abort(ioc);
 296             return -1;
 297         }
 298         return 1;
 299     }
 300
 301     assert(namelen < sizeof(name));
 302     if (nbd_read(ioc, name, namelen, errp) < 0) {
 303         error_prepend(errp, "failed to read export name: ");
 304         nbd_send_opt_abort(ioc);
 305         return -1;
 306     }
 307     name[namelen] = '\0';
 308     len -= namelen;
 309     if (nbd_drop(ioc, len, errp) < 0) {
 310         error_prepend(errp, "failed to read export description: ");
 311         nbd_send_opt_abort(ioc);
 312         return -1;
 313     }
 314     if (!strcmp(name, want)) {
 315         *match = true;
 316     }
 317     return 1;
 318 }
 319
 320
 321 /* Returns -1 if NBD_OPT_GO proves the export @wantname cannot be
 322  * used, 0 if NBD_OPT_GO is unsupported (fall back to NBD_OPT_LIST and
 323  * NBD_OPT_EXPORT_NAME in that case), and > 0 if the export is good to
 324  * go (with @info populated). */
 325 static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
 326                       NBDExportInfo *info, Error **errp)
 327 {
 328     NBDOptionReply reply;
 329     uint32_t len = strlen(wantname);
 330     uint16_t type;
 331     int error;
 332     char *buf;
 333
 334     /* The protocol requires that the server send NBD_INFO_EXPORT with
 335      * a non-zero flags (at least NBD_FLAG_HAS_FLAGS must be set); so
 336      * flags still 0 is a witness of a broken server. */
 337     info->flags = 0;
 338
 339     trace_nbd_opt_go_start(wantname);
 340     buf = g_malloc(4 + len + 2 + 2 * info->request_sizes + 1);
 341     stl_be_p(buf, len);
 342     memcpy(buf + 4, wantname, len);
 343     /* At most one request, everything else up to server */
 344     stw_be_p(buf + 4 + len, info->request_sizes);
 345     if (info->request_sizes) {
 346         stw_be_p(buf + 4 + len + 2, NBD_INFO_BLOCK_SIZE);
 347     }
 348     error = nbd_send_option_request(ioc, NBD_OPT_GO,
 349                                     4 + len + 2 + 2 * info->request_sizes,
 350                                     buf, errp);
 351     g_free(buf);
 352     if (error < 0) {
 353         return -1;
 354     }
 355
 356     while (1) {
 357         if (nbd_receive_option_reply(ioc, NBD_OPT_GO, &reply, errp) < 0) {
 358             return -1;
 359         }
 360         error = nbd_handle_reply_err(ioc, &reply, errp);
 361         if (error <= 0) {
 362             return error;
 363         }
 364         len = reply.length;
 365
 366         if (reply.type == NBD_REP_ACK) {
 367             /* Server is done sending info and moved into transmission
 368                phase, but make sure it sent flags */
 369             if (len) {
 370                 error_setg(errp, "server sent invalid NBD_REP_ACK");
 371                 return -1;
 372             }
 373             if (!info->flags) {
 374                 error_setg(errp, "broken server omitted NBD_INFO_EXPORT");
 375                 return -1;
 376             }
 377             trace_nbd_opt_go_success();
 378             return 1;
 379         }
 380         if (reply.type != NBD_REP_INFO) {
 381             error_setg(errp, "unexpected reply type %" PRIu32
 382                        " (%s), expected %u",
 383                        reply.type, nbd_rep_lookup(reply.type), NBD_REP_INFO);
 384             nbd_send_opt_abort(ioc);
 385             return -1;
 386         }
 387         if (len < sizeof(type)) {
 388             error_setg(errp, "NBD_REP_INFO length %" PRIu32 " is too short",
 389                        len);
 390             nbd_send_opt_abort(ioc);
 391             return -1;
 392         }
 393         if (nbd_read(ioc, &type, sizeof(type), errp) < 0) {
 394             error_prepend(errp, "failed to read info type: ");
 395             nbd_send_opt_abort(ioc);
 396             return -1;
 397         }
 398         len -= sizeof(type);
 399         be16_to_cpus(&type);
 400         switch (type) {
 401         case NBD_INFO_EXPORT:
 402             if (len != sizeof(info->size) + sizeof(info->flags)) {
 403                 error_setg(errp, "remaining export info len %" PRIu32
 404                            " is unexpected size", len);
 405                 nbd_send_opt_abort(ioc);
 406                 return -1;
 407             }
 408             if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
 409                 error_prepend(errp, "failed to read info size: ");
 410                 nbd_send_opt_abort(ioc);
 411                 return -1;
 412             }
 413             be64_to_cpus(&info->size);
 414             if (nbd_read(ioc, &info->flags, sizeof(info->flags), errp) < 0) {
 415                 error_prepend(errp, "failed to read info flags: ");
 416                 nbd_send_opt_abort(ioc);
 417                 return -1;
 418             }
 419             be16_to_cpus(&info->flags);
 420             trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
 421             break;
 422
 423         case NBD_INFO_BLOCK_SIZE:
 424             if (len != sizeof(info->min_block) * 3) {
 425                 error_setg(errp, "remaining export info len %" PRIu32
 426                            " is unexpected size", len);
 427                 nbd_send_opt_abort(ioc);
 428                 return -1;
 429             }
 430             if (nbd_read(ioc, &info->min_block, sizeof(info->min_block),
 431                          errp) < 0) {
 432                 error_prepend(errp, "failed to read info minimum block size: ");
 433                 nbd_send_opt_abort(ioc);
 434                 return -1;
 435             }
 436             be32_to_cpus(&info->min_block);
 437             if (!is_power_of_2(info->min_block)) {
 438                 error_setg(errp, "server minimum block size %" PRId32
 439                            "is not a power of two", info->min_block);
 440                 nbd_send_opt_abort(ioc);
 441                 return -1;
 442             }
 443             if (nbd_read(ioc, &info->opt_block, sizeof(info->opt_block),
 444                          errp) < 0) {
 445                 error_prepend(errp,
 446                               "failed to read info preferred block size: ");
 447                 nbd_send_opt_abort(ioc);
 448                 return -1;
 449             }
 450             be32_to_cpus(&info->opt_block);
 451             if (!is_power_of_2(info->opt_block) ||
 452                 info->opt_block < info->min_block) {
 453                 error_setg(errp, "server preferred block size %" PRId32
 454                            "is not valid", info->opt_block);
 455                 nbd_send_opt_abort(ioc);
 456                 return -1;
 457             }
 458             if (nbd_read(ioc, &info->max_block, sizeof(info->max_block),
 459                          errp) < 0) {
 460                 error_prepend(errp, "failed to read info maximum block size: ");
 461                 nbd_send_opt_abort(ioc);
 462                 return -1;
 463             }
 464             be32_to_cpus(&info->max_block);
 465             trace_nbd_opt_go_info_block_size(info->min_block, info->opt_block,
 466                                              info->max_block);
 467             break;
 468
 469         default:
 470             trace_nbd_opt_go_info_unknown(type, nbd_info_lookup(type));
 471             if (nbd_drop(ioc, len, errp) < 0) {
 472                 error_prepend(errp, "Failed to read info payload: ");
 473                 nbd_send_opt_abort(ioc);
 474                 return -1;
 475             }
 476             break;
 477         }
 478     }
 479 }
 480
 481 /* Return -1 on failure, 0 if wantname is an available export. */
 482 static int nbd_receive_query_exports(QIOChannel *ioc,
 483                                      const char *wantname,
 484                                      Error **errp)
 485 {
 486     bool foundExport = false;
 487
 488     trace_nbd_receive_query_exports_start(wantname);
 489     if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
 490         return -1;
 491     }
 492
 493     while (1) {
 494         int ret = nbd_receive_list(ioc, wantname, &foundExport, errp);
 495
 496         if (ret < 0) {
 497             /* Server gave unexpected reply */
 498             return -1;
 499         } else if (ret == 0) {
 500             /* Done iterating. */
 501             if (!foundExport) {
 502                 error_setg(errp, "No export with name '%s' available",
 503                            wantname);
 504                 nbd_send_opt_abort(ioc);
 505                 return -1;
 506             }
 507             trace_nbd_receive_query_exports_success(wantname);
 508             return 0;
 509         }
 510     }
 511 }
 512
 513 /* nbd_request_simple_option: Send an option request, and parse the reply
 514  * return 1 for successful negotiation,
 515  *        0 if operation is unsupported,
 516  *        -1 with errp set for any other error
 517  */
 518 static int nbd_request_simple_option(QIOChannel *ioc, int opt, Error **errp)
 519 {
 520     NBDOptionReply reply;
 521     int error;
 522
 523     if (nbd_send_option_request(ioc, opt, 0, NULL, errp) < 0) {
 524         return -1;
 525     }
 526
 527     if (nbd_receive_option_reply(ioc, opt, &reply, errp) < 0) {
 528         return -1;
 529     }
 530     error = nbd_handle_reply_err(ioc, &reply, errp);
 531     if (error <= 0) {
 532         return error;
 533     }
 534
 535     if (reply.type != NBD_REP_ACK) {
 536         error_setg(errp, "Server answered option %d (%s) with unexpected "
 537                    "reply %" PRIu32 " (%s)", opt, nbd_opt_lookup(opt),
 538                    reply.type, nbd_rep_lookup(reply.type));
 539         nbd_send_opt_abort(ioc);
 540         return -1;
 541     }
 542
 543     if (reply.length != 0) {
 544         error_setg(errp, "Option %d ('%s') response length is %" PRIu32
 545                    " (it should be zero)", opt, nbd_opt_lookup(opt),
 546                    reply.length);
 547         nbd_send_opt_abort(ioc);
 548         return -1;
 549     }
 550
 551     return 1;
 552 }
 553
 554 static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
 555                                         QCryptoTLSCreds *tlscreds,
 556                                         const char *hostname, Error **errp)
 557 {
 558     int ret;
 559     QIOChannelTLS *tioc;
 560     struct NBDTLSHandshakeData data = { 0 };
 561
 562     ret = nbd_request_simple_option(ioc, NBD_OPT_STARTTLS, errp);
 563     if (ret <= 0) {
 564         if (ret == 0) {
 565             error_setg(errp, "Server don't support STARTTLS option");
 566             nbd_send_opt_abort(ioc);
 567         }
 568         return NULL;
 569     }
 570
 571     trace_nbd_receive_starttls_new_client();
 572     tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
 573     if (!tioc) {
 574         return NULL;
 575     }
 576     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
 577     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 578     trace_nbd_receive_starttls_tls_handshake();
 579     qio_channel_tls_handshake(tioc,
 580                               nbd_tls_handshake,
 581                               &data,
 582                               NULL,
 583                               NULL);
 584
 585     if (!data.complete) {
 586         g_main_loop_run(data.loop);
 587     }
 588     g_main_loop_unref(data.loop);
 589     if (data.error) {
 590         error_propagate(errp, data.error);
 591         object_unref(OBJECT(tioc));
 592         return NULL;
 593     }
 594
 595     return QIO_CHANNEL(tioc);
 596 }
 597
 598 /* nbd_negotiate_simple_meta_context:
 599  * Set one meta context. Simple means that reply must contain zero (not
 600  * negotiated) or one (negotiated) contexts. More contexts would be considered
 601  * as a protocol error. It's also implied that meta-data query equals queried
 602  * context name, so, if server replies with something different than @context,
 603  * it is considered an error too.
 604  * return 1 for successful negotiation, context_id is set
 605  *        0 if operation is unsupported,
 606  *        -1 with errp set for any other error
 607  */
 608 static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
 609                                              const char *export,
 610                                              const char *context,
 611                                              uint32_t *context_id,
 612                                              Error **errp)
 613 {
 614     int ret;
 615     NBDOptionReply reply;
 616     uint32_t received_id;
 617     bool received;
 618     uint32_t export_len = strlen(export);
 619     uint32_t context_len = strlen(context);
 620     uint32_t data_len = sizeof(export_len) + export_len +
 621                         sizeof(uint32_t) + /* number of queries */
 622                         sizeof(context_len) + context_len;
 623     char *data = g_malloc(data_len);
 624     char *p = data;
 625
 626     trace_nbd_opt_meta_request(context, export);
 627     stl_be_p(p, export_len);
 628     memcpy(p += sizeof(export_len), export, export_len);
 629     stl_be_p(p += export_len, 1);
 630     stl_be_p(p += sizeof(uint32_t), context_len);
 631     memcpy(p += sizeof(context_len), context, context_len);
 632
 633     ret = nbd_send_option_request(ioc, NBD_OPT_SET_META_CONTEXT, data_len, data,
 634                                   errp);
 635     g_free(data);
 636     if (ret < 0) {
 637         return ret;
 638     }
 639
 640     if (nbd_receive_option_reply(ioc, NBD_OPT_SET_META_CONTEXT, &reply,
 641                                  errp) < 0)
 642     {
 643         return -1;
 644     }
 645
 646     ret = nbd_handle_reply_err(ioc, &reply, errp);
 647     if (ret <= 0) {
 648         return ret;
 649     }
 650
 651     if (reply.type == NBD_REP_META_CONTEXT) {
 652         char *name;
 653
 654         if (reply.length != sizeof(received_id) + context_len) {
 655             error_setg(errp, "Failed to negotiate meta context '%s', server "
 656                        "answered with unexpected length %" PRIu32, context,
 657                        reply.length);
 658             nbd_send_opt_abort(ioc);
 659             return -1;
 660         }
 661
 662         if (nbd_read(ioc, &received_id, sizeof(received_id), errp) < 0) {
 663             return -1;
 664         }
 665         be32_to_cpus(&received_id);
 666
 667         reply.length -= sizeof(received_id);
 668         name = g_malloc(reply.length + 1);
 669         if (nbd_read(ioc, name, reply.length, errp) < 0) {
 670             g_free(name);
 671             return -1;
 672         }
 673         name[reply.length] = '\0';
 674         if (strcmp(context, name)) {
 675             error_setg(errp, "Failed to negotiate meta context '%s', server "
 676                        "answered with different context '%s'", context,
 677                        name);
 678             g_free(name);
 679             nbd_send_opt_abort(ioc);
 680             return -1;
 681         }
 682         g_free(name);
 683
 684         trace_nbd_opt_meta_reply(context, received_id);
 685         received = true;
 686
 687         /* receive NBD_REP_ACK */
 688         if (nbd_receive_option_reply(ioc, NBD_OPT_SET_META_CONTEXT, &reply,
 689                                      errp) < 0)
 690         {
 691             return -1;
 692         }
 693
 694         ret = nbd_handle_reply_err(ioc, &reply, errp);
 695         if (ret <= 0) {
 696             return ret;
 697         }
 698     }
 699
 700     if (reply.type != NBD_REP_ACK) {
 701         error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
 702                    reply.type, NBD_REP_ACK);
 703         nbd_send_opt_abort(ioc);
 704         return -1;
 705     }
 706     if (reply.length) {
 707         error_setg(errp, "Unexpected length to ACK response");
 708         nbd_send_opt_abort(ioc);
 709         return -1;
 710     }
 711
 712     if (received) {
 713         *context_id = received_id;
 714         return 1;
 715     }
 716
 717     return 0;
 718 }
 719
 720 int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
 721                           QCryptoTLSCreds *tlscreds, const char *hostname,
 722                           QIOChannel **outioc, NBDExportInfo *info,
 723                           Error **errp)
 724 {
 725     char buf[256];
 726     uint64_t magic;
 727     int rc;
 728     bool zeroes = true;
 729     bool structured_reply = info->structured_reply;
 730     bool base_allocation = info->base_allocation;
 731
 732     trace_nbd_receive_negotiate(tlscreds, hostname ? hostname : "<null>");
 733
 734     info->structured_reply = false;
 735     info->base_allocation = false;
 736     rc = -EINVAL;
 737
 738     if (outioc) {
 739         *outioc = NULL;
 740     }
 741     if (tlscreds && !outioc) {
 742         error_setg(errp, "Output I/O channel required for TLS");
 743         goto fail;
 744     }
 745
 746     if (nbd_read(ioc, buf, 8, errp) < 0) {
 747         error_prepend(errp, "Failed to read data: ");
 748         goto fail;
 749     }
 750
 751     buf[8] = '\0';
 752     if (strlen(buf) == 0) {
 753         error_setg(errp, "Server connection closed unexpectedly");
 754         goto fail;
 755     }
 756
 757     magic = ldq_be_p(buf);
 758     trace_nbd_receive_negotiate_magic(magic);
 759
 760     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 761         error_setg(errp, "Invalid magic received");
 762         goto fail;
 763     }
 764
 765     if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
 766         error_prepend(errp, "Failed to read magic: ");
 767         goto fail;
 768     }
 769     magic = be64_to_cpu(magic);
 770     trace_nbd_receive_negotiate_magic(magic);
 771
 772     if (magic == NBD_OPTS_MAGIC) {
 773         uint32_t clientflags = 0;
 774         uint16_t globalflags;
 775         bool fixedNewStyle = false;
 776
 777         if (nbd_read(ioc, &globalflags, sizeof(globalflags), errp) < 0) {
 778             error_prepend(errp, "Failed to read server flags: ");
 779             goto fail;
 780         }
 781         globalflags = be16_to_cpu(globalflags);
 782         trace_nbd_receive_negotiate_server_flags(globalflags);
 783         if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
 784             fixedNewStyle = true;
 785             clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
 786         }
 787         if (globalflags & NBD_FLAG_NO_ZEROES) {
 788             zeroes = false;
 789             clientflags |= NBD_FLAG_C_NO_ZEROES;
 790         }
 791         /* client requested flags */
 792         clientflags = cpu_to_be32(clientflags);
 793         if (nbd_write(ioc, &clientflags, sizeof(clientflags), errp) < 0) {
 794             error_prepend(errp, "Failed to send clientflags field: ");
 795             goto fail;
 796         }
 797         if (tlscreds) {
 798             if (fixedNewStyle) {
 799                 *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
 800                 if (!*outioc) {
 801                     goto fail;
 802                 }
 803                 ioc = *outioc;
 804             } else {
 805                 error_setg(errp, "Server does not support STARTTLS");
 806                 goto fail;
 807             }
 808         }
 809         if (!name) {
 810             trace_nbd_receive_negotiate_default_name();
 811             name = "";
 812         }
 813         if (fixedNewStyle) {
 814             int result;
 815
 816             if (structured_reply) {
 817                 result = nbd_request_simple_option(ioc,
 818                                                    NBD_OPT_STRUCTURED_REPLY,
 819                                                    errp);
 820                 if (result < 0) {
 821                     goto fail;
 822                 }
 823                 info->structured_reply = result == 1;
 824             }
 825
 826             if (info->structured_reply && base_allocation) {
 827                 result = nbd_negotiate_simple_meta_context(
 828                         ioc, name, "base:allocation",
 829                         &info->meta_base_allocation_id, errp);
 830                 if (result < 0) {
 831                     goto fail;
 832                 }
 833                 info->base_allocation = result == 1;
 834             }
 835
 836             /* Try NBD_OPT_GO first - if it works, we are done (it
 837              * also gives us a good message if the server requires
 838              * TLS).  If it is not available, fall back to
 839              * NBD_OPT_LIST for nicer error messages about a missing
 840              * export, then use NBD_OPT_EXPORT_NAME.  */
 841             result = nbd_opt_go(ioc, name, info, errp);
 842             if (result < 0) {
 843                 goto fail;
 844             }
 845             if (result > 0) {
 846                 return 0;
 847             }
 848             /* Check our desired export is present in the
 849              * server export list. Since NBD_OPT_EXPORT_NAME
 850              * cannot return an error message, running this
 851              * query gives us better error reporting if the
 852              * export name is not available.
 853              */
 854             if (nbd_receive_query_exports(ioc, name, errp) < 0) {
 855                 goto fail;
 856             }
 857         }
 858         /* write the export name request */
 859         if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, name,
 860                                     errp) < 0) {
 861             goto fail;
 862         }
 863
 864         /* Read the response */
 865         if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
 866             error_prepend(errp, "Failed to read export length: ");
 867             goto fail;
 868         }
 869         be64_to_cpus(&info->size);
 870
 871         if (nbd_read(ioc, &info->flags, sizeof(info->flags), errp) < 0) {
 872             error_prepend(errp, "Failed to read export flags: ");
 873             goto fail;
 874         }
 875         be16_to_cpus(&info->flags);
 876     } else if (magic == NBD_CLIENT_MAGIC) {
 877         uint32_t oldflags;
 878
 879         if (name) {
 880             error_setg(errp, "Server does not support export names");
 881             goto fail;
 882         }
 883         if (tlscreds) {
 884             error_setg(errp, "Server does not support STARTTLS");
 885             goto fail;
 886         }
 887
 888         if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
 889             error_prepend(errp, "Failed to read export length: ");
 890             goto fail;
 891         }
 892         be64_to_cpus(&info->size);
 893
 894         if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
 895             error_prepend(errp, "Failed to read export flags: ");
 896             goto fail;
 897         }
 898         be32_to_cpus(&oldflags);
 899         if (oldflags & ~0xffff) {
 900             error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
 901             goto fail;
 902         }
 903         info->flags = oldflags;
 904     } else {
 905         error_setg(errp, "Bad magic received");
 906         goto fail;
 907     }
 908
 909     trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
 910     if (zeroes && nbd_drop(ioc, 124, errp) < 0) {
 911         error_prepend(errp, "Failed to read reserved block: ");
 912         goto fail;
 913     }
 914     rc = 0;
 915
 916 fail:
 917     return rc;
 918 }
 919
 920 #ifdef __linux__
 921 int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
 922              Error **errp)
 923 {
 924     unsigned long sector_size = MAX(BDRV_SECTOR_SIZE, info->min_block);
 925     unsigned long sectors = info->size / sector_size;
 926
 927     /* FIXME: Once the kernel module is patched to honor block sizes,
 928      * and to advertise that fact to user space, we should update the
 929      * hand-off to the kernel to use any block sizes we learned. */
 930     assert(!info->request_sizes);
 931     if (info->size / sector_size != sectors) {
 932         error_setg(errp, "Export size %" PRIu64 " too large for 32-bit kernel",
 933                    info->size);
 934         return -E2BIG;
 935     }
 936
 937     trace_nbd_init_set_socket();
 938
 939     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
 940         int serrno = errno;
 941         error_setg(errp, "Failed to set NBD socket");
 942         return -serrno;
 943     }
 944
 945     trace_nbd_init_set_block_size(sector_size);
 946
 947     if (ioctl(fd, NBD_SET_BLKSIZE, sector_size) < 0) {
 948         int serrno = errno;
 949         error_setg(errp, "Failed setting NBD block size");
 950         return -serrno;
 951     }
 952
 953     trace_nbd_init_set_size(sectors);
 954     if (info->size % sector_size) {
 955         trace_nbd_init_trailing_bytes(info->size % sector_size);
 956     }
 957
 958     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
 959         int serrno = errno;
 960         error_setg(errp, "Failed setting size (in blocks)");
 961         return -serrno;
 962     }
 963
 964     if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) info->flags) < 0) {
 965         if (errno == ENOTTY) {
 966             int read_only = (info->flags & NBD_FLAG_READ_ONLY) != 0;
 967             trace_nbd_init_set_readonly();
 968
 969             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 970                 int serrno = errno;
 971                 error_setg(errp, "Failed setting read-only attribute");
 972                 return -serrno;
 973             }
 974         } else {
 975             int serrno = errno;
 976             error_setg(errp, "Failed setting flags");
 977             return -serrno;
 978         }
 979     }
 980
 981     trace_nbd_init_finish();
 982
 983     return 0;
 984 }
 985
 986 int nbd_client(int fd)
 987 {
 988     int ret;
 989     int serrno;
 990
 991     trace_nbd_client_loop();
 992
 993     ret = ioctl(fd, NBD_DO_IT);
 994     if (ret < 0 && errno == EPIPE) {
 995         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 996          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 997          * that case.
 998          */
 999         ret = 0;
1000     }
1001     serrno = errno;
1002
1003     trace_nbd_client_loop_ret(ret, strerror(serrno));
1004
1005     trace_nbd_client_clear_queue();
1006     ioctl(fd, NBD_CLEAR_QUE);
1007
1008     trace_nbd_client_clear_socket();
1009     ioctl(fd, NBD_CLEAR_SOCK);
1010
1011     errno = serrno;
1012     return ret;
1013 }
1014
1015 int nbd_disconnect(int fd)
1016 {
1017     ioctl(fd, NBD_CLEAR_QUE);
1018     ioctl(fd, NBD_DISCONNECT);
1019     ioctl(fd, NBD_CLEAR_SOCK);
1020     return 0;
1021 }
1022
1023 #else
1024 int nbd_init(int fd, QIOChannelSocket *ioc, NBDExportInfo *info,
1025              Error **errp)
1026 {
1027     error_setg(errp, "nbd_init is only supported on Linux");
1028     return -ENOTSUP;
1029 }
1030
1031 int nbd_client(int fd)
1032 {
1033     return -ENOTSUP;
1034 }
1035 int nbd_disconnect(int fd)
1036 {
1037     return -ENOTSUP;
1038 }
1039 #endif
1040
1041 int nbd_send_request(QIOChannel *ioc, NBDRequest *request)
1042 {
1043     uint8_t buf[NBD_REQUEST_SIZE];
1044
1045     trace_nbd_send_request(request->from, request->len, request->handle,
1046                            request->flags, request->type,
1047                            nbd_cmd_lookup(request->type));
1048
1049     stl_be_p(buf, NBD_REQUEST_MAGIC);
1050     stw_be_p(buf + 4, request->flags);
1051     stw_be_p(buf + 6, request->type);
1052     stq_be_p(buf + 8, request->handle);
1053     stq_be_p(buf + 16, request->from);
1054     stl_be_p(buf + 24, request->len);
1055
1056     return nbd_write(ioc, buf, sizeof(buf), NULL);
1057 }
1058
1059 /* nbd_receive_simple_reply
1060  * Read simple reply except magic field (which should be already read).
1061  * Payload is not read (payload is possible for CMD_READ, but here we even
1062  * don't know whether it take place or not).
1063  */
1064 static int nbd_receive_simple_reply(QIOChannel *ioc, NBDSimpleReply *reply,
1065                                     Error **errp)
1066 {
1067     int ret;
1068
1069     assert(reply->magic == NBD_SIMPLE_REPLY_MAGIC);
1070
1071     ret = nbd_read(ioc, (uint8_t *)reply + sizeof(reply->magic),
1072                    sizeof(*reply) - sizeof(reply->magic), errp);
1073     if (ret < 0) {
1074         return ret;
1075     }
1076
1077     be32_to_cpus(&reply->error);
1078     be64_to_cpus(&reply->handle);
1079
1080     return 0;
1081 }
1082
1083 /* nbd_receive_structured_reply_chunk
1084  * Read structured reply chunk except magic field (which should be already
1085  * read).
1086  * Payload is not read.
1087  */
1088 static int nbd_receive_structured_reply_chunk(QIOChannel *ioc,
1089                                               NBDStructuredReplyChunk *chunk,
1090                                               Error **errp)
1091 {
1092     int ret;
1093
1094     assert(chunk->magic == NBD_STRUCTURED_REPLY_MAGIC);
1095
1096     ret = nbd_read(ioc, (uint8_t *)chunk + sizeof(chunk->magic),
1097                    sizeof(*chunk) - sizeof(chunk->magic), errp);
1098     if (ret < 0) {
1099         return ret;
1100     }
1101
1102     be16_to_cpus(&chunk->flags);
1103     be16_to_cpus(&chunk->type);
1104     be64_to_cpus(&chunk->handle);
1105     be32_to_cpus(&chunk->length);
1106
1107     return 0;
1108 }
1109
1110 /* nbd_receive_reply
1111  * Returns 1 on success
1112  *         0 on eof, when no data was read (errp is not set)
1113  *         negative errno on failure (errp is set)
1114  */
1115 int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
1116 {
1117     int ret;
1118     const char *type;
1119
1120     ret = nbd_read_eof(ioc, &reply->magic, sizeof(reply->magic), errp);
1121     if (ret <= 0) {
1122         return ret;
1123     }
1124
1125     be32_to_cpus(&reply->magic);
1126
1127     switch (reply->magic) {
1128     case NBD_SIMPLE_REPLY_MAGIC:
1129         ret = nbd_receive_simple_reply(ioc, &reply->simple, errp);
1130         if (ret < 0) {
1131             break;
1132         }
1133         trace_nbd_receive_simple_reply(reply->simple.error,
1134                                        nbd_err_lookup(reply->simple.error),
1135                                        reply->handle);
1136         break;
1137     case NBD_STRUCTURED_REPLY_MAGIC:
1138         ret = nbd_receive_structured_reply_chunk(ioc, &reply->structured, errp);
1139         if (ret < 0) {
1140             break;
1141         }
1142         type = nbd_reply_type_lookup(reply->structured.type);
1143         trace_nbd_receive_structured_reply_chunk(reply->structured.flags,
1144                                                  reply->structured.type, type,
1145                                                  reply->structured.handle,
1146                                                  reply->structured.length);
1147         break;
1148     default:
1149         error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", reply->magic);
1150         return -EINVAL;
1151     }
1152     if (ret < 0) {
1153         return ret;
1154     }
1155
1156     return 1;
1157 }
1158