nbd/client.c

   1 /*
   2  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   3  *
   4  *  Network Block Device Client Side
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; under version 2 of the License.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "qemu/osdep.h"
  20 #include "qapi/error.h"
  21 #include "nbd-internal.h"
  22
  23 static int nbd_errno_to_system_errno(int err)
  24 {
  25     switch (err) {
  26     case NBD_SUCCESS:
  27         return 0;
  28     case NBD_EPERM:
  29         return EPERM;
  30     case NBD_EIO:
  31         return EIO;
  32     case NBD_ENOMEM:
  33         return ENOMEM;
  34     case NBD_ENOSPC:
  35         return ENOSPC;
  36     default:
  37         TRACE("Squashing unexpected error %d to EINVAL", err);
  38         /* fallthrough */
  39     case NBD_EINVAL:
  40         return EINVAL;
  41     }
  42 }
  43
  44 /* Definitions for opaque data types */
  45
  46 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  47
  48 /* That's all folks */
  49
  50 /* Basic flow for negotiation
  51
  52    Server         Client
  53    Negotiate
  54
  55    or
  56
  57    Server         Client
  58    Negotiate #1
  59                   Option
  60    Negotiate #2
  61
  62    ----
  63
  64    followed by
  65
  66    Server         Client
  67                   Request
  68    Response
  69                   Request
  70    Response
  71                   ...
  72    ...
  73                   Request (type == 2)
  74
  75 */
  76
  77
  78 /* If type represents success, return 1 without further action.
  79  * If type represents an error reply, consume the rest of the packet on ioc.
  80  * Then return 0 for unsupported (so the client can fall back to
  81  * other approaches), or -1 with errp set for other errors.
  82  */
  83 static int nbd_handle_reply_err(QIOChannel *ioc, uint32_t opt, uint32_t type,
  84                                 Error **errp)
  85 {
  86     uint32_t len;
  87     char *msg = NULL;
  88     int result = -1;
  89
  90     if (!(type & (1 << 31))) {
  91         return 1;
  92     }
  93
  94     if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
  95         error_setg(errp, "failed to read option length");
  96         return -1;
  97     }
  98     len = be32_to_cpu(len);
  99     if (len) {
 100         if (len > NBD_MAX_BUFFER_SIZE) {
 101             error_setg(errp, "server's error message is too long");
 102             goto cleanup;
 103         }
 104         msg = g_malloc(len + 1);
 105         if (read_sync(ioc, msg, len) != len) {
 106             error_setg(errp, "failed to read option error message");
 107             goto cleanup;
 108         }
 109         msg[len] = '\0';
 110     }
 111
 112     switch (type) {
 113     case NBD_REP_ERR_UNSUP:
 114         TRACE("server doesn't understand request %" PRIx32
 115               ", attempting fallback", opt);
 116         result = 0;
 117         goto cleanup;
 118
 119     case NBD_REP_ERR_POLICY:
 120         error_setg(errp, "Denied by server for option %" PRIx32, opt);
 121         break;
 122
 123     case NBD_REP_ERR_INVALID:
 124         error_setg(errp, "Invalid data length for option %" PRIx32, opt);
 125         break;
 126
 127     case NBD_REP_ERR_TLS_REQD:
 128         error_setg(errp, "TLS negotiation required before option %" PRIx32,
 129                    opt);
 130         break;
 131
 132     default:
 133         error_setg(errp, "Unknown error code when asking for option %" PRIx32,
 134                    opt);
 135         break;
 136     }
 137
 138     if (msg) {
 139         error_append_hint(errp, "%s\n", msg);
 140     }
 141
 142  cleanup:
 143     g_free(msg);
 144     return result;
 145 }
 146
 147 static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
 148 {
 149     uint64_t magic;
 150     uint32_t opt;
 151     uint32_t type;
 152     uint32_t len;
 153     uint32_t namelen;
 154     int error;
 155
 156     *name = NULL;
 157     if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 158         error_setg(errp, "failed to read list option magic");
 159         return -1;
 160     }
 161     magic = be64_to_cpu(magic);
 162     if (magic != NBD_REP_MAGIC) {
 163         error_setg(errp, "Unexpected option list magic");
 164         return -1;
 165     }
 166     if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 167         error_setg(errp, "failed to read list option");
 168         return -1;
 169     }
 170     opt = be32_to_cpu(opt);
 171     if (opt != NBD_OPT_LIST) {
 172         error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
 173                    opt, NBD_OPT_LIST);
 174         return -1;
 175     }
 176
 177     if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
 178         error_setg(errp, "failed to read list option type");
 179         return -1;
 180     }
 181     type = be32_to_cpu(type);
 182     error = nbd_handle_reply_err(ioc, opt, type, errp);
 183     if (error <= 0) {
 184         return error;
 185     }
 186
 187     if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
 188         error_setg(errp, "failed to read option length");
 189         return -1;
 190     }
 191     len = be32_to_cpu(len);
 192
 193     if (type == NBD_REP_ACK) {
 194         if (len != 0) {
 195             error_setg(errp, "length too long for option end");
 196             return -1;
 197         }
 198     } else if (type == NBD_REP_SERVER) {
 199         if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
 200             error_setg(errp, "incorrect option length");
 201             return -1;
 202         }
 203         if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
 204             error_setg(errp, "failed to read option name length");
 205             return -1;
 206         }
 207         namelen = be32_to_cpu(namelen);
 208         len -= sizeof(namelen);
 209         if (len < namelen) {
 210             error_setg(errp, "incorrect option name length");
 211             return -1;
 212         }
 213         if (namelen > NBD_MAX_NAME_SIZE) {
 214             error_setg(errp, "export name length too long %" PRIu32, namelen);
 215             return -1;
 216         }
 217
 218         *name = g_new0(char, namelen + 1);
 219         if (read_sync(ioc, *name, namelen) != namelen) {
 220             error_setg(errp, "failed to read export name");
 221             g_free(*name);
 222             *name = NULL;
 223             return -1;
 224         }
 225         (*name)[namelen] = '\0';
 226         len -= namelen;
 227         if (len) {
 228             char *buf = g_malloc(len + 1);
 229             if (read_sync(ioc, buf, len) != len) {
 230                 error_setg(errp, "failed to read export description");
 231                 g_free(*name);
 232                 g_free(buf);
 233                 *name = NULL;
 234                 return -1;
 235             }
 236             buf[len] = '\0';
 237             TRACE("Ignoring export description: %s", buf);
 238             g_free(buf);
 239         }
 240     } else {
 241         error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
 242                    type, NBD_REP_SERVER);
 243         return -1;
 244     }
 245     return 1;
 246 }
 247
 248
 249 static int nbd_receive_query_exports(QIOChannel *ioc,
 250                                      const char *wantname,
 251                                      Error **errp)
 252 {
 253     uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
 254     uint32_t opt = cpu_to_be32(NBD_OPT_LIST);
 255     uint32_t length = 0;
 256     bool foundExport = false;
 257
 258     TRACE("Querying export list");
 259     if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 260         error_setg(errp, "Failed to send list option magic");
 261         return -1;
 262     }
 263
 264     if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 265         error_setg(errp, "Failed to send list option number");
 266         return -1;
 267     }
 268
 269     if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
 270         error_setg(errp, "Failed to send list option length");
 271         return -1;
 272     }
 273
 274     TRACE("Reading available export names");
 275     while (1) {
 276         char *name = NULL;
 277         int ret = nbd_receive_list(ioc, &name, errp);
 278
 279         if (ret < 0) {
 280             g_free(name);
 281             name = NULL;
 282             return -1;
 283         }
 284         if (ret == 0) {
 285             /* Server doesn't support export listing, so
 286              * we will just assume an export with our
 287              * wanted name exists */
 288             foundExport = true;
 289             break;
 290         }
 291         if (name == NULL) {
 292             TRACE("End of export name list");
 293             break;
 294         }
 295         if (g_str_equal(name, wantname)) {
 296             foundExport = true;
 297             TRACE("Found desired export name '%s'", name);
 298         } else {
 299             TRACE("Ignored export name '%s'", name);
 300         }
 301         g_free(name);
 302     }
 303
 304     if (!foundExport) {
 305         error_setg(errp, "No export with name '%s' available", wantname);
 306         return -1;
 307     }
 308
 309     return 0;
 310 }
 311
 312 static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
 313                                         QCryptoTLSCreds *tlscreds,
 314                                         const char *hostname, Error **errp)
 315 {
 316     uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
 317     uint32_t opt = cpu_to_be32(NBD_OPT_STARTTLS);
 318     uint32_t length = 0;
 319     uint32_t type;
 320     QIOChannelTLS *tioc;
 321     struct NBDTLSHandshakeData data = { 0 };
 322
 323     TRACE("Requesting TLS from server");
 324     if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 325         error_setg(errp, "Failed to send option magic");
 326         return NULL;
 327     }
 328
 329     if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 330         error_setg(errp, "Failed to send option number");
 331         return NULL;
 332     }
 333
 334     if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
 335         error_setg(errp, "Failed to send option length");
 336         return NULL;
 337     }
 338
 339     TRACE("Getting TLS reply from server1");
 340     if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 341         error_setg(errp, "failed to read option magic");
 342         return NULL;
 343     }
 344     magic = be64_to_cpu(magic);
 345     if (magic != NBD_REP_MAGIC) {
 346         error_setg(errp, "Unexpected option magic");
 347         return NULL;
 348     }
 349     TRACE("Getting TLS reply from server2");
 350     if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 351         error_setg(errp, "failed to read option");
 352         return NULL;
 353     }
 354     opt = be32_to_cpu(opt);
 355     if (opt != NBD_OPT_STARTTLS) {
 356         error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
 357                    opt, NBD_OPT_STARTTLS);
 358         return NULL;
 359     }
 360
 361     TRACE("Getting TLS reply from server");
 362     if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
 363         error_setg(errp, "failed to read option type");
 364         return NULL;
 365     }
 366     type = be32_to_cpu(type);
 367     if (type != NBD_REP_ACK) {
 368         error_setg(errp, "Server rejected request to start TLS %" PRIx32,
 369                    type);
 370         return NULL;
 371     }
 372
 373     TRACE("Getting TLS reply from server");
 374     if (read_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
 375         error_setg(errp, "failed to read option length");
 376         return NULL;
 377     }
 378     length = be32_to_cpu(length);
 379     if (length != 0) {
 380         error_setg(errp, "Start TLS response was not zero %" PRIu32,
 381                    length);
 382         return NULL;
 383     }
 384
 385     TRACE("TLS request approved, setting up TLS");
 386     tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
 387     if (!tioc) {
 388         return NULL;
 389     }
 390     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
 391     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 392     TRACE("Starting TLS handshake");
 393     qio_channel_tls_handshake(tioc,
 394                               nbd_tls_handshake,
 395                               &data,
 396                               NULL);
 397
 398     if (!data.complete) {
 399         g_main_loop_run(data.loop);
 400     }
 401     g_main_loop_unref(data.loop);
 402     if (data.error) {
 403         error_propagate(errp, data.error);
 404         object_unref(OBJECT(tioc));
 405         return NULL;
 406     }
 407
 408     return QIO_CHANNEL(tioc);
 409 }
 410
 411
 412 int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
 413                           QCryptoTLSCreds *tlscreds, const char *hostname,
 414                           QIOChannel **outioc,
 415                           off_t *size, Error **errp)
 416 {
 417     char buf[256];
 418     uint64_t magic, s;
 419     int rc;
 420
 421     TRACE("Receiving negotiation tlscreds=%p hostname=%s.",
 422           tlscreds, hostname ? hostname : "<null>");
 423
 424     rc = -EINVAL;
 425
 426     if (outioc) {
 427         *outioc = NULL;
 428     }
 429     if (tlscreds && !outioc) {
 430         error_setg(errp, "Output I/O channel required for TLS");
 431         goto fail;
 432     }
 433
 434     if (read_sync(ioc, buf, 8) != 8) {
 435         error_setg(errp, "Failed to read data");
 436         goto fail;
 437     }
 438
 439     buf[8] = '\0';
 440     if (strlen(buf) == 0) {
 441         error_setg(errp, "Server connection closed unexpectedly");
 442         goto fail;
 443     }
 444
 445     TRACE("Magic is %c%c%c%c%c%c%c%c",
 446           qemu_isprint(buf[0]) ? buf[0] : '.',
 447           qemu_isprint(buf[1]) ? buf[1] : '.',
 448           qemu_isprint(buf[2]) ? buf[2] : '.',
 449           qemu_isprint(buf[3]) ? buf[3] : '.',
 450           qemu_isprint(buf[4]) ? buf[4] : '.',
 451           qemu_isprint(buf[5]) ? buf[5] : '.',
 452           qemu_isprint(buf[6]) ? buf[6] : '.',
 453           qemu_isprint(buf[7]) ? buf[7] : '.');
 454
 455     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 456         error_setg(errp, "Invalid magic received");
 457         goto fail;
 458     }
 459
 460     if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 461         error_setg(errp, "Failed to read magic");
 462         goto fail;
 463     }
 464     magic = be64_to_cpu(magic);
 465     TRACE("Magic is 0x%" PRIx64, magic);
 466
 467     if (magic == NBD_OPTS_MAGIC) {
 468         uint32_t clientflags = 0;
 469         uint32_t opt;
 470         uint32_t namesize;
 471         uint16_t globalflags;
 472         bool fixedNewStyle = false;
 473
 474         if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
 475             sizeof(globalflags)) {
 476             error_setg(errp, "Failed to read server flags");
 477             goto fail;
 478         }
 479         globalflags = be16_to_cpu(globalflags);
 480         TRACE("Global flags are %" PRIx32, globalflags);
 481         if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
 482             fixedNewStyle = true;
 483             TRACE("Server supports fixed new style");
 484             clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
 485         }
 486         /* client requested flags */
 487         clientflags = cpu_to_be32(clientflags);
 488         if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
 489             sizeof(clientflags)) {
 490             error_setg(errp, "Failed to send clientflags field");
 491             goto fail;
 492         }
 493         if (tlscreds) {
 494             if (fixedNewStyle) {
 495                 *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
 496                 if (!*outioc) {
 497                     goto fail;
 498                 }
 499                 ioc = *outioc;
 500             } else {
 501                 error_setg(errp, "Server does not support STARTTLS");
 502                 goto fail;
 503             }
 504         }
 505         if (!name) {
 506             TRACE("Using default NBD export name \"\"");
 507             name = "";
 508         }
 509         if (fixedNewStyle) {
 510             /* Check our desired export is present in the
 511              * server export list. Since NBD_OPT_EXPORT_NAME
 512              * cannot return an error message, running this
 513              * query gives us good error reporting if the
 514              * server required TLS
 515              */
 516             if (nbd_receive_query_exports(ioc, name, errp) < 0) {
 517                 goto fail;
 518             }
 519         }
 520         /* write the export name */
 521         magic = cpu_to_be64(magic);
 522         if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 523             error_setg(errp, "Failed to send export name magic");
 524             goto fail;
 525         }
 526         opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
 527         if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 528             error_setg(errp, "Failed to send export name option number");
 529             goto fail;
 530         }
 531         namesize = cpu_to_be32(strlen(name));
 532         if (write_sync(ioc, &namesize, sizeof(namesize)) !=
 533             sizeof(namesize)) {
 534             error_setg(errp, "Failed to send export name length");
 535             goto fail;
 536         }
 537         if (write_sync(ioc, (char *)name, strlen(name)) != strlen(name)) {
 538             error_setg(errp, "Failed to send export name");
 539             goto fail;
 540         }
 541
 542         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 543             error_setg(errp, "Failed to read export length");
 544             goto fail;
 545         }
 546         *size = be64_to_cpu(s);
 547
 548         if (read_sync(ioc, flags, sizeof(*flags)) != sizeof(*flags)) {
 549             error_setg(errp, "Failed to read export flags");
 550             goto fail;
 551         }
 552         be16_to_cpus(flags);
 553     } else if (magic == NBD_CLIENT_MAGIC) {
 554         uint32_t oldflags;
 555
 556         if (name) {
 557             error_setg(errp, "Server does not support export names");
 558             goto fail;
 559         }
 560         if (tlscreds) {
 561             error_setg(errp, "Server does not support STARTTLS");
 562             goto fail;
 563         }
 564
 565         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 566             error_setg(errp, "Failed to read export length");
 567             goto fail;
 568         }
 569         *size = be64_to_cpu(s);
 570         TRACE("Size is %" PRIu64, *size);
 571
 572         if (read_sync(ioc, &oldflags, sizeof(oldflags)) != sizeof(oldflags)) {
 573             error_setg(errp, "Failed to read export flags");
 574             goto fail;
 575         }
 576         be32_to_cpus(&oldflags);
 577         if (oldflags & ~0xffff) {
 578             error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
 579             goto fail;
 580         }
 581         *flags = oldflags;
 582     } else {
 583         error_setg(errp, "Bad magic received");
 584         goto fail;
 585     }
 586
 587     TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
 588     if (read_sync(ioc, &buf, 124) != 124) {
 589         error_setg(errp, "Failed to read reserved block");
 590         goto fail;
 591     }
 592     rc = 0;
 593
 594 fail:
 595     return rc;
 596 }
 597
 598 #ifdef __linux__
 599 int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 600 {
 601     unsigned long sectors = size / BDRV_SECTOR_SIZE;
 602     if (size / BDRV_SECTOR_SIZE != sectors) {
 603         LOG("Export size %lld too large for 32-bit kernel", (long long) size);
 604         return -E2BIG;
 605     }
 606
 607     TRACE("Setting NBD socket");
 608
 609     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
 610         int serrno = errno;
 611         LOG("Failed to set NBD socket");
 612         return -serrno;
 613     }
 614
 615     TRACE("Setting block size to %lu", (unsigned long)BDRV_SECTOR_SIZE);
 616
 617     if (ioctl(fd, NBD_SET_BLKSIZE, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
 618         int serrno = errno;
 619         LOG("Failed setting NBD block size");
 620         return -serrno;
 621     }
 622
 623     TRACE("Setting size to %lu block(s)", sectors);
 624     if (size % BDRV_SECTOR_SIZE) {
 625         TRACE("Ignoring trailing %d bytes of export",
 626               (int) (size % BDRV_SECTOR_SIZE));
 627     }
 628
 629     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
 630         int serrno = errno;
 631         LOG("Failed setting size (in blocks)");
 632         return -serrno;
 633     }
 634
 635     if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) flags) < 0) {
 636         if (errno == ENOTTY) {
 637             int read_only = (flags & NBD_FLAG_READ_ONLY) != 0;
 638             TRACE("Setting readonly attribute");
 639
 640             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 641                 int serrno = errno;
 642                 LOG("Failed setting read-only attribute");
 643                 return -serrno;
 644             }
 645         } else {
 646             int serrno = errno;
 647             LOG("Failed setting flags");
 648             return -serrno;
 649         }
 650     }
 651
 652     TRACE("Negotiation ended");
 653
 654     return 0;
 655 }
 656
 657 int nbd_client(int fd)
 658 {
 659     int ret;
 660     int serrno;
 661
 662     TRACE("Doing NBD loop");
 663
 664     ret = ioctl(fd, NBD_DO_IT);
 665     if (ret < 0 && errno == EPIPE) {
 666         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 667          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 668          * that case.
 669          */
 670         ret = 0;
 671     }
 672     serrno = errno;
 673
 674     TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
 675
 676     TRACE("Clearing NBD queue");
 677     ioctl(fd, NBD_CLEAR_QUE);
 678
 679     TRACE("Clearing NBD socket");
 680     ioctl(fd, NBD_CLEAR_SOCK);
 681
 682     errno = serrno;
 683     return ret;
 684 }
 685
 686 int nbd_disconnect(int fd)
 687 {
 688     ioctl(fd, NBD_CLEAR_QUE);
 689     ioctl(fd, NBD_DISCONNECT);
 690     ioctl(fd, NBD_CLEAR_SOCK);
 691     return 0;
 692 }
 693
 694 #else
 695 int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size)
 696 {
 697     return -ENOTSUP;
 698 }
 699
 700 int nbd_client(int fd)
 701 {
 702     return -ENOTSUP;
 703 }
 704 int nbd_disconnect(int fd)
 705 {
 706     return -ENOTSUP;
 707 }
 708 #endif
 709
 710 ssize_t nbd_send_request(QIOChannel *ioc, struct nbd_request *request)
 711 {
 712     uint8_t buf[NBD_REQUEST_SIZE];
 713     ssize_t ret;
 714
 715     TRACE("Sending request to server: "
 716           "{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
 717           ", .type=%" PRIu32 " }",
 718           request->from, request->len, request->handle, request->type);
 719
 720     stl_be_p(buf, NBD_REQUEST_MAGIC);
 721     stl_be_p(buf + 4, request->type);
 722     stq_be_p(buf + 8, request->handle);
 723     stq_be_p(buf + 16, request->from);
 724     stl_be_p(buf + 24, request->len);
 725
 726     ret = write_sync(ioc, buf, sizeof(buf));
 727     if (ret < 0) {
 728         return ret;
 729     }
 730
 731     if (ret != sizeof(buf)) {
 732         LOG("writing to socket failed");
 733         return -EINVAL;
 734     }
 735     return 0;
 736 }
 737
 738 ssize_t nbd_receive_reply(QIOChannel *ioc, struct nbd_reply *reply)
 739 {
 740     uint8_t buf[NBD_REPLY_SIZE];
 741     uint32_t magic;
 742     ssize_t ret;
 743
 744     ret = read_sync(ioc, buf, sizeof(buf));
 745     if (ret < 0) {
 746         return ret;
 747     }
 748
 749     if (ret != sizeof(buf)) {
 750         LOG("read failed");
 751         return -EINVAL;
 752     }
 753
 754     /* Reply
 755        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 756        [ 4 ..  7]    error   (0 == no error)
 757        [ 7 .. 15]    handle
 758      */
 759
 760     magic = ldl_be_p(buf);
 761     reply->error  = ldl_be_p(buf + 4);
 762     reply->handle = ldq_be_p(buf + 8);
 763
 764     reply->error = nbd_errno_to_system_errno(reply->error);
 765
 766     TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
 767           ", handle = %" PRIu64" }",
 768           magic, reply->error, reply->handle);
 769
 770     if (magic != NBD_REPLY_MAGIC) {
 771         LOG("invalid magic (got 0x%" PRIx32 ")", magic);
 772         return -EINVAL;
 773     }
 774     return 0;
 775 }
 776