nbd/client.c

   1 /*
   2  *  Copyright (C) 2016 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 "nbd-internal.h"
  23
  24 static int nbd_errno_to_system_errno(int err)
  25 {
  26     int ret;
  27     switch (err) {
  28     case NBD_SUCCESS:
  29         ret = 0;
  30         break;
  31     case NBD_EPERM:
  32         ret = EPERM;
  33         break;
  34     case NBD_EIO:
  35         ret = EIO;
  36         break;
  37     case NBD_ENOMEM:
  38         ret = ENOMEM;
  39         break;
  40     case NBD_ENOSPC:
  41         ret = ENOSPC;
  42         break;
  43     case NBD_ESHUTDOWN:
  44         ret = ESHUTDOWN;
  45         break;
  46     default:
  47         TRACE("Squashing unexpected error %d to EINVAL", err);
  48         /* fallthrough */
  49     case NBD_EINVAL:
  50         ret = EINVAL;
  51         break;
  52     }
  53     return ret;
  54 }
  55
  56 /* Definitions for opaque data types */
  57
  58 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  59
  60 /* That's all folks */
  61
  62 /* Basic flow for negotiation
  63
  64    Server         Client
  65    Negotiate
  66
  67    or
  68
  69    Server         Client
  70    Negotiate #1
  71                   Option
  72    Negotiate #2
  73
  74    ----
  75
  76    followed by
  77
  78    Server         Client
  79                   Request
  80    Response
  81                   Request
  82    Response
  83                   ...
  84    ...
  85                   Request (type == 2)
  86
  87 */
  88
  89 /* Send an option request.
  90  *
  91  * The request is for option @opt, with @data containing @len bytes of
  92  * additional payload for the request (@len may be -1 to treat @data as
  93  * a C string; and @data may be NULL if @len is 0).
  94  * Return 0 if successful, -1 with errp set if it is impossible to
  95  * continue. */
  96 static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
  97                                    uint32_t len, const char *data,
  98                                    Error **errp)
  99 {
 100     nbd_option req;
 101     QEMU_BUILD_BUG_ON(sizeof(req) != 16);
 102
 103     if (len == -1) {
 104         req.length = len = strlen(data);
 105     }
 106     TRACE("Sending option request %" PRIu32", len %" PRIu32, opt, len);
 107
 108     stq_be_p(&req.magic, NBD_OPTS_MAGIC);
 109     stl_be_p(&req.option, opt);
 110     stl_be_p(&req.length, len);
 111
 112     if (nbd_write(ioc, &req, sizeof(req), errp) < 0) {
 113         error_prepend(errp, "Failed to send option request header");
 114         return -1;
 115     }
 116
 117     if (len && nbd_write(ioc, (char *) data, len, errp) < 0) {
 118         error_prepend(errp, "Failed to send option request data");
 119         return -1;
 120     }
 121
 122     return 0;
 123 }
 124
 125 /* Send NBD_OPT_ABORT as a courtesy to let the server know that we are
 126  * not going to attempt further negotiation. */
 127 static void nbd_send_opt_abort(QIOChannel *ioc)
 128 {
 129     /* Technically, a compliant server is supposed to reply to us; but
 130      * older servers disconnected instead. At any rate, we're allowed
 131      * to disconnect without waiting for the server reply, so we don't
 132      * even care if the request makes it to the server, let alone
 133      * waiting around for whether the server replies. */
 134     nbd_send_option_request(ioc, NBD_OPT_ABORT, 0, NULL, NULL);
 135 }
 136
 137
 138 /* Receive the header of an option reply, which should match the given
 139  * opt.  Read through the length field, but NOT the length bytes of
 140  * payload. Return 0 if successful, -1 with errp set if it is
 141  * impossible to continue. */
 142 static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
 143                                     nbd_opt_reply *reply, Error **errp)
 144 {
 145     QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
 146     if (nbd_read(ioc, reply, sizeof(*reply), errp) < 0) {
 147         error_prepend(errp, "failed to read option reply");
 148         nbd_send_opt_abort(ioc);
 149         return -1;
 150     }
 151     be64_to_cpus(&reply->magic);
 152     be32_to_cpus(&reply->option);
 153     be32_to_cpus(&reply->type);
 154     be32_to_cpus(&reply->length);
 155
 156     TRACE("Received option reply %" PRIx32", type %" PRIx32", len %" PRIu32,
 157           reply->option, reply->type, reply->length);
 158
 159     if (reply->magic != NBD_REP_MAGIC) {
 160         error_setg(errp, "Unexpected option reply magic");
 161         nbd_send_opt_abort(ioc);
 162         return -1;
 163     }
 164     if (reply->option != opt) {
 165         error_setg(errp, "Unexpected option type %x expected %x",
 166                    reply->option, opt);
 167         nbd_send_opt_abort(ioc);
 168         return -1;
 169     }
 170     return 0;
 171 }
 172
 173 /* If reply represents success, return 1 without further action.
 174  * If reply represents an error, consume the optional payload of
 175  * the packet on ioc.  Then return 0 for unsupported (so the client
 176  * can fall back to other approaches), or -1 with errp set for other
 177  * errors.
 178  */
 179 static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply,
 180                                 Error **errp)
 181 {
 182     char *msg = NULL;
 183     int result = -1;
 184
 185     if (!(reply->type & (1 << 31))) {
 186         return 1;
 187     }
 188
 189     if (reply->length) {
 190         if (reply->length > NBD_MAX_BUFFER_SIZE) {
 191             error_setg(errp, "server's error message is too long");
 192             goto cleanup;
 193         }
 194         msg = g_malloc(reply->length + 1);
 195         if (nbd_read(ioc, msg, reply->length, errp) < 0) {
 196             error_prepend(errp, "failed to read option error message");
 197             goto cleanup;
 198         }
 199         msg[reply->length] = '\0';
 200     }
 201
 202     switch (reply->type) {
 203     case NBD_REP_ERR_UNSUP:
 204         TRACE("server doesn't understand request %" PRIx32
 205               ", attempting fallback", reply->option);
 206         result = 0;
 207         goto cleanup;
 208
 209     case NBD_REP_ERR_POLICY:
 210         error_setg(errp, "Denied by server for option %" PRIx32,
 211                    reply->option);
 212         break;
 213
 214     case NBD_REP_ERR_INVALID:
 215         error_setg(errp, "Invalid data length for option %" PRIx32,
 216                    reply->option);
 217         break;
 218
 219     case NBD_REP_ERR_PLATFORM:
 220         error_setg(errp, "Server lacks support for option %" PRIx32,
 221                    reply->option);
 222         break;
 223
 224     case NBD_REP_ERR_TLS_REQD:
 225         error_setg(errp, "TLS negotiation required before option %" PRIx32,
 226                    reply->option);
 227         break;
 228
 229     case NBD_REP_ERR_SHUTDOWN:
 230         error_setg(errp, "Server shutting down before option %" PRIx32,
 231                    reply->option);
 232         break;
 233
 234     default:
 235         error_setg(errp, "Unknown error code when asking for option %" PRIx32,
 236                    reply->option);
 237         break;
 238     }
 239
 240     if (msg) {
 241         error_append_hint(errp, "%s\n", msg);
 242     }
 243
 244  cleanup:
 245     g_free(msg);
 246     if (result < 0) {
 247         nbd_send_opt_abort(ioc);
 248     }
 249     return result;
 250 }
 251
 252 /* Process another portion of the NBD_OPT_LIST reply.  Set *@match if
 253  * the current reply matches @want or if the server does not support
 254  * NBD_OPT_LIST, otherwise leave @match alone.  Return 0 if iteration
 255  * is complete, positive if more replies are expected, or negative
 256  * with @errp set if an unrecoverable error occurred. */
 257 static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
 258                             Error **errp)
 259 {
 260     nbd_opt_reply reply;
 261     uint32_t len;
 262     uint32_t namelen;
 263     char name[NBD_MAX_NAME_SIZE + 1];
 264     int error;
 265
 266     if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
 267         return -1;
 268     }
 269     error = nbd_handle_reply_err(ioc, &reply, errp);
 270     if (error <= 0) {
 271         /* The server did not support NBD_OPT_LIST, so set *match on
 272          * the assumption that any name will be accepted.  */
 273         *match = true;
 274         return error;
 275     }
 276     len = reply.length;
 277
 278     if (reply.type == NBD_REP_ACK) {
 279         if (len != 0) {
 280             error_setg(errp, "length too long for option end");
 281             nbd_send_opt_abort(ioc);
 282             return -1;
 283         }
 284         return 0;
 285     } else if (reply.type != NBD_REP_SERVER) {
 286         error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
 287                    reply.type, NBD_REP_SERVER);
 288         nbd_send_opt_abort(ioc);
 289         return -1;
 290     }
 291
 292     if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
 293         error_setg(errp, "incorrect option length %" PRIu32, len);
 294         nbd_send_opt_abort(ioc);
 295         return -1;
 296     }
 297     if (nbd_read(ioc, &namelen, sizeof(namelen), errp) < 0) {
 298         error_prepend(errp, "failed to read option name length");
 299         nbd_send_opt_abort(ioc);
 300         return -1;
 301     }
 302     namelen = be32_to_cpu(namelen);
 303     len -= sizeof(namelen);
 304     if (len < namelen) {
 305         error_setg(errp, "incorrect option name length");
 306         nbd_send_opt_abort(ioc);
 307         return -1;
 308     }
 309     if (namelen != strlen(want)) {
 310         if (nbd_drop(ioc, len, errp) < 0) {
 311             error_prepend(errp, "failed to skip export name with wrong length");
 312             nbd_send_opt_abort(ioc);
 313             return -1;
 314         }
 315         return 1;
 316     }
 317
 318     assert(namelen < sizeof(name));
 319     if (nbd_read(ioc, name, namelen, errp) < 0) {
 320         error_prepend(errp, "failed to read export name");
 321         nbd_send_opt_abort(ioc);
 322         return -1;
 323     }
 324     name[namelen] = '\0';
 325     len -= namelen;
 326     if (nbd_drop(ioc, len, errp) < 0) {
 327         error_prepend(errp, "failed to read export description");
 328         nbd_send_opt_abort(ioc);
 329         return -1;
 330     }
 331     if (!strcmp(name, want)) {
 332         *match = true;
 333     }
 334     return 1;
 335 }
 336
 337
 338 /* Return -1 on failure, 0 if wantname is an available export. */
 339 static int nbd_receive_query_exports(QIOChannel *ioc,
 340                                      const char *wantname,
 341                                      Error **errp)
 342 {
 343     bool foundExport = false;
 344
 345     TRACE("Querying export list for '%s'", wantname);
 346     if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
 347         return -1;
 348     }
 349
 350     TRACE("Reading available export names");
 351     while (1) {
 352         int ret = nbd_receive_list(ioc, wantname, &foundExport, errp);
 353
 354         if (ret < 0) {
 355             /* Server gave unexpected reply */
 356             return -1;
 357         } else if (ret == 0) {
 358             /* Done iterating. */
 359             if (!foundExport) {
 360                 error_setg(errp, "No export with name '%s' available",
 361                            wantname);
 362                 nbd_send_opt_abort(ioc);
 363                 return -1;
 364             }
 365             TRACE("Found desired export name '%s'", wantname);
 366             return 0;
 367         }
 368     }
 369 }
 370
 371 static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
 372                                         QCryptoTLSCreds *tlscreds,
 373                                         const char *hostname, Error **errp)
 374 {
 375     nbd_opt_reply reply;
 376     QIOChannelTLS *tioc;
 377     struct NBDTLSHandshakeData data = { 0 };
 378
 379     TRACE("Requesting TLS from server");
 380     if (nbd_send_option_request(ioc, NBD_OPT_STARTTLS, 0, NULL, errp) < 0) {
 381         return NULL;
 382     }
 383
 384     TRACE("Getting TLS reply from server");
 385     if (nbd_receive_option_reply(ioc, NBD_OPT_STARTTLS, &reply, errp) < 0) {
 386         return NULL;
 387     }
 388
 389     if (reply.type != NBD_REP_ACK) {
 390         error_setg(errp, "Server rejected request to start TLS %" PRIx32,
 391                    reply.type);
 392         nbd_send_opt_abort(ioc);
 393         return NULL;
 394     }
 395
 396     if (reply.length != 0) {
 397         error_setg(errp, "Start TLS response was not zero %" PRIu32,
 398                    reply.length);
 399         nbd_send_opt_abort(ioc);
 400         return NULL;
 401     }
 402
 403     TRACE("TLS request approved, setting up TLS");
 404     tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
 405     if (!tioc) {
 406         return NULL;
 407     }
 408     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
 409     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 410     TRACE("Starting TLS handshake");
 411     qio_channel_tls_handshake(tioc,
 412                               nbd_tls_handshake,
 413                               &data,
 414                               NULL);
 415
 416     if (!data.complete) {
 417         g_main_loop_run(data.loop);
 418     }
 419     g_main_loop_unref(data.loop);
 420     if (data.error) {
 421         error_propagate(errp, data.error);
 422         object_unref(OBJECT(tioc));
 423         return NULL;
 424     }
 425
 426     return QIO_CHANNEL(tioc);
 427 }
 428
 429
 430 int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
 431                           QCryptoTLSCreds *tlscreds, const char *hostname,
 432                           QIOChannel **outioc,
 433                           off_t *size, Error **errp)
 434 {
 435     char buf[256];
 436     uint64_t magic, s;
 437     int rc;
 438     bool zeroes = true;
 439
 440     TRACE("Receiving negotiation tlscreds=%p hostname=%s.",
 441           tlscreds, hostname ? hostname : "<null>");
 442
 443     rc = -EINVAL;
 444
 445     if (outioc) {
 446         *outioc = NULL;
 447     }
 448     if (tlscreds && !outioc) {
 449         error_setg(errp, "Output I/O channel required for TLS");
 450         goto fail;
 451     }
 452
 453     if (nbd_read(ioc, buf, 8, errp) < 0) {
 454         error_prepend(errp, "Failed to read data");
 455         goto fail;
 456     }
 457
 458     buf[8] = '\0';
 459     if (strlen(buf) == 0) {
 460         error_setg(errp, "Server connection closed unexpectedly");
 461         goto fail;
 462     }
 463
 464     TRACE("Magic is %c%c%c%c%c%c%c%c",
 465           qemu_isprint(buf[0]) ? buf[0] : '.',
 466           qemu_isprint(buf[1]) ? buf[1] : '.',
 467           qemu_isprint(buf[2]) ? buf[2] : '.',
 468           qemu_isprint(buf[3]) ? buf[3] : '.',
 469           qemu_isprint(buf[4]) ? buf[4] : '.',
 470           qemu_isprint(buf[5]) ? buf[5] : '.',
 471           qemu_isprint(buf[6]) ? buf[6] : '.',
 472           qemu_isprint(buf[7]) ? buf[7] : '.');
 473
 474     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 475         error_setg(errp, "Invalid magic received");
 476         goto fail;
 477     }
 478
 479     if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
 480         error_prepend(errp, "Failed to read magic");
 481         goto fail;
 482     }
 483     magic = be64_to_cpu(magic);
 484     TRACE("Magic is 0x%" PRIx64, magic);
 485
 486     if (magic == NBD_OPTS_MAGIC) {
 487         uint32_t clientflags = 0;
 488         uint16_t globalflags;
 489         bool fixedNewStyle = false;
 490
 491         if (nbd_read(ioc, &globalflags, sizeof(globalflags), errp) < 0) {
 492             error_prepend(errp, "Failed to read server flags");
 493             goto fail;
 494         }
 495         globalflags = be16_to_cpu(globalflags);
 496         TRACE("Global flags are %" PRIx32, globalflags);
 497         if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
 498             fixedNewStyle = true;
 499             TRACE("Server supports fixed new style");
 500             clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
 501         }
 502         if (globalflags & NBD_FLAG_NO_ZEROES) {
 503             zeroes = false;
 504             TRACE("Server supports no zeroes");
 505             clientflags |= NBD_FLAG_C_NO_ZEROES;
 506         }
 507         /* client requested flags */
 508         clientflags = cpu_to_be32(clientflags);
 509         if (nbd_write(ioc, &clientflags, sizeof(clientflags), errp) < 0) {
 510             error_prepend(errp, "Failed to send clientflags field");
 511             goto fail;
 512         }
 513         if (tlscreds) {
 514             if (fixedNewStyle) {
 515                 *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
 516                 if (!*outioc) {
 517                     goto fail;
 518                 }
 519                 ioc = *outioc;
 520             } else {
 521                 error_setg(errp, "Server does not support STARTTLS");
 522                 goto fail;
 523             }
 524         }
 525         if (!name) {
 526             TRACE("Using default NBD export name \"\"");
 527             name = "";
 528         }
 529         if (fixedNewStyle) {
 530             /* Check our desired export is present in the
 531              * server export list. Since NBD_OPT_EXPORT_NAME
 532              * cannot return an error message, running this
 533              * query gives us good error reporting if the
 534              * server required TLS
 535              */
 536             if (nbd_receive_query_exports(ioc, name, errp) < 0) {
 537                 goto fail;
 538             }
 539         }
 540         /* write the export name request */
 541         if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, name,
 542                                     errp) < 0) {
 543             goto fail;
 544         }
 545
 546         /* Read the response */
 547         if (nbd_read(ioc, &s, sizeof(s), errp) < 0) {
 548             error_prepend(errp, "Failed to read export length");
 549             goto fail;
 550         }
 551         *size = be64_to_cpu(s);
 552
 553         if (nbd_read(ioc, flags, sizeof(*flags), errp) < 0) {
 554             error_prepend(errp, "Failed to read export flags");
 555             goto fail;
 556         }
 557         be16_to_cpus(flags);
 558     } else if (magic == NBD_CLIENT_MAGIC) {
 559         uint32_t oldflags;
 560
 561         if (name) {
 562             error_setg(errp, "Server does not support export names");
 563             goto fail;
 564         }
 565         if (tlscreds) {
 566             error_setg(errp, "Server does not support STARTTLS");
 567             goto fail;
 568         }
 569
 570         if (nbd_read(ioc, &s, sizeof(s), errp) < 0) {
 571             error_prepend(errp, "Failed to read export length");
 572             goto fail;
 573         }
 574         *size = be64_to_cpu(s);
 575         TRACE("Size is %" PRIu64, *size);
 576
 577         if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
 578             error_prepend(errp, "Failed to read export flags");
 579             goto fail;
 580         }
 581         be32_to_cpus(&oldflags);
 582         if (oldflags & ~0xffff) {
 583             error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
 584             goto fail;
 585         }
 586         *flags = oldflags;
 587     } else {
 588         error_setg(errp, "Bad magic received");
 589         goto fail;
 590     }
 591
 592     TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
 593     if (zeroes && nbd_drop(ioc, 124, errp) < 0) {
 594         error_prepend(errp, "Failed to read reserved block");
 595         goto fail;
 596     }
 597     rc = 0;
 598
 599 fail:
 600     return rc;
 601 }
 602
 603 #ifdef __linux__
 604 int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size,
 605              Error **errp)
 606 {
 607     unsigned long sectors = size / BDRV_SECTOR_SIZE;
 608     if (size / BDRV_SECTOR_SIZE != sectors) {
 609         error_setg(errp, "Export size %lld too large for 32-bit kernel",
 610                    (long long) size);
 611         return -E2BIG;
 612     }
 613
 614     TRACE("Setting NBD socket");
 615
 616     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
 617         int serrno = errno;
 618         error_setg(errp, "Failed to set NBD socket");
 619         return -serrno;
 620     }
 621
 622     TRACE("Setting block size to %lu", (unsigned long)BDRV_SECTOR_SIZE);
 623
 624     if (ioctl(fd, NBD_SET_BLKSIZE, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
 625         int serrno = errno;
 626         error_setg(errp, "Failed setting NBD block size");
 627         return -serrno;
 628     }
 629
 630     TRACE("Setting size to %lu block(s)", sectors);
 631     if (size % BDRV_SECTOR_SIZE) {
 632         TRACE("Ignoring trailing %d bytes of export",
 633               (int) (size % BDRV_SECTOR_SIZE));
 634     }
 635
 636     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
 637         int serrno = errno;
 638         error_setg(errp, "Failed setting size (in blocks)");
 639         return -serrno;
 640     }
 641
 642     if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) flags) < 0) {
 643         if (errno == ENOTTY) {
 644             int read_only = (flags & NBD_FLAG_READ_ONLY) != 0;
 645             TRACE("Setting readonly attribute");
 646
 647             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 648                 int serrno = errno;
 649                 error_setg(errp, "Failed setting read-only attribute");
 650                 return -serrno;
 651             }
 652         } else {
 653             int serrno = errno;
 654             error_setg(errp, "Failed setting flags");
 655             return -serrno;
 656         }
 657     }
 658
 659     TRACE("Negotiation ended");
 660
 661     return 0;
 662 }
 663
 664 int nbd_client(int fd)
 665 {
 666     int ret;
 667     int serrno;
 668
 669     TRACE("Doing NBD loop");
 670
 671     ret = ioctl(fd, NBD_DO_IT);
 672     if (ret < 0 && errno == EPIPE) {
 673         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 674          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 675          * that case.
 676          */
 677         ret = 0;
 678     }
 679     serrno = errno;
 680
 681     TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
 682
 683     TRACE("Clearing NBD queue");
 684     ioctl(fd, NBD_CLEAR_QUE);
 685
 686     TRACE("Clearing NBD socket");
 687     ioctl(fd, NBD_CLEAR_SOCK);
 688
 689     errno = serrno;
 690     return ret;
 691 }
 692
 693 int nbd_disconnect(int fd)
 694 {
 695     ioctl(fd, NBD_CLEAR_QUE);
 696     ioctl(fd, NBD_DISCONNECT);
 697     ioctl(fd, NBD_CLEAR_SOCK);
 698     return 0;
 699 }
 700
 701 #else
 702 int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size,
 703              Error **errp)
 704 {
 705     error_setg(errp, "nbd_init is only supported on Linux");
 706     return -ENOTSUP;
 707 }
 708
 709 int nbd_client(int fd)
 710 {
 711     return -ENOTSUP;
 712 }
 713 int nbd_disconnect(int fd)
 714 {
 715     return -ENOTSUP;
 716 }
 717 #endif
 718
 719 ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request)
 720 {
 721     uint8_t buf[NBD_REQUEST_SIZE];
 722
 723     TRACE("Sending request to server: "
 724           "{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
 725           ", .flags = %" PRIx16 ", .type = %" PRIu16 " }",
 726           request->from, request->len, request->handle,
 727           request->flags, request->type);
 728
 729     stl_be_p(buf, NBD_REQUEST_MAGIC);
 730     stw_be_p(buf + 4, request->flags);
 731     stw_be_p(buf + 6, request->type);
 732     stq_be_p(buf + 8, request->handle);
 733     stq_be_p(buf + 16, request->from);
 734     stl_be_p(buf + 24, request->len);
 735
 736     return nbd_write(ioc, buf, sizeof(buf), NULL);
 737 }
 738
 739 ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
 740 {
 741     uint8_t buf[NBD_REPLY_SIZE];
 742     uint32_t magic;
 743     ssize_t ret;
 744
 745     ret = nbd_read_eof(ioc, buf, sizeof(buf), errp);
 746     if (ret <= 0) {
 747         return ret;
 748     }
 749
 750     if (ret != sizeof(buf)) {
 751         error_setg(errp, "read failed");
 752         return -EINVAL;
 753     }
 754
 755     /* Reply
 756        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 757        [ 4 ..  7]    error   (0 == no error)
 758        [ 7 .. 15]    handle
 759      */
 760
 761     magic = ldl_be_p(buf);
 762     reply->error  = ldl_be_p(buf + 4);
 763     reply->handle = ldq_be_p(buf + 8);
 764
 765     reply->error = nbd_errno_to_system_errno(reply->error);
 766
 767     if (reply->error == ESHUTDOWN) {
 768         /* This works even on mingw which lacks a native ESHUTDOWN */
 769         error_setg(errp, "server shutting down");
 770         return -EINVAL;
 771     }
 772     TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
 773           ", handle = %" PRIu64" }",
 774           magic, reply->error, reply->handle);
 775
 776     if (magic != NBD_REPLY_MAGIC) {
 777         error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
 778         return -EINVAL;
 779     }
 780     return sizeof(buf);
 781 }
 782