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     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 391     TRACE("Starting TLS handshake");
 392     qio_channel_tls_handshake(tioc,
 393                               nbd_tls_handshake,
 394                               &data,
 395                               NULL);
 396
 397     if (!data.complete) {
 398         g_main_loop_run(data.loop);
 399     }
 400     g_main_loop_unref(data.loop);
 401     if (data.error) {
 402         error_propagate(errp, data.error);
 403         object_unref(OBJECT(tioc));
 404         return NULL;
 405     }
 406
 407     return QIO_CHANNEL(tioc);
 408 }
 409
 410
 411 int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
 412                           QCryptoTLSCreds *tlscreds, const char *hostname,
 413                           QIOChannel **outioc,
 414                           off_t *size, Error **errp)
 415 {
 416     char buf[256];
 417     uint64_t magic, s;
 418     int rc;
 419
 420     TRACE("Receiving negotiation tlscreds=%p hostname=%s.",
 421           tlscreds, hostname ? hostname : "<null>");
 422
 423     rc = -EINVAL;
 424
 425     if (outioc) {
 426         *outioc = NULL;
 427     }
 428     if (tlscreds && !outioc) {
 429         error_setg(errp, "Output I/O channel required for TLS");
 430         goto fail;
 431     }
 432
 433     if (read_sync(ioc, buf, 8) != 8) {
 434         error_setg(errp, "Failed to read data");
 435         goto fail;
 436     }
 437
 438     buf[8] = '\0';
 439     if (strlen(buf) == 0) {
 440         error_setg(errp, "Server connection closed unexpectedly");
 441         goto fail;
 442     }
 443
 444     TRACE("Magic is %c%c%c%c%c%c%c%c",
 445           qemu_isprint(buf[0]) ? buf[0] : '.',
 446           qemu_isprint(buf[1]) ? buf[1] : '.',
 447           qemu_isprint(buf[2]) ? buf[2] : '.',
 448           qemu_isprint(buf[3]) ? buf[3] : '.',
 449           qemu_isprint(buf[4]) ? buf[4] : '.',
 450           qemu_isprint(buf[5]) ? buf[5] : '.',
 451           qemu_isprint(buf[6]) ? buf[6] : '.',
 452           qemu_isprint(buf[7]) ? buf[7] : '.');
 453
 454     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 455         error_setg(errp, "Invalid magic received");
 456         goto fail;
 457     }
 458
 459     if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 460         error_setg(errp, "Failed to read magic");
 461         goto fail;
 462     }
 463     magic = be64_to_cpu(magic);
 464     TRACE("Magic is 0x%" PRIx64, magic);
 465
 466     if (magic == NBD_OPTS_MAGIC) {
 467         uint32_t clientflags = 0;
 468         uint32_t opt;
 469         uint32_t namesize;
 470         uint16_t globalflags;
 471         bool fixedNewStyle = false;
 472
 473         if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
 474             sizeof(globalflags)) {
 475             error_setg(errp, "Failed to read server flags");
 476             goto fail;
 477         }
 478         globalflags = be16_to_cpu(globalflags);
 479         TRACE("Global flags are %" PRIx32, globalflags);
 480         if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
 481             fixedNewStyle = true;
 482             TRACE("Server supports fixed new style");
 483             clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
 484         }
 485         /* client requested flags */
 486         clientflags = cpu_to_be32(clientflags);
 487         if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
 488             sizeof(clientflags)) {
 489             error_setg(errp, "Failed to send clientflags field");
 490             goto fail;
 491         }
 492         if (tlscreds) {
 493             if (fixedNewStyle) {
 494                 *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
 495                 if (!*outioc) {
 496                     goto fail;
 497                 }
 498                 ioc = *outioc;
 499             } else {
 500                 error_setg(errp, "Server does not support STARTTLS");
 501                 goto fail;
 502             }
 503         }
 504         if (!name) {
 505             TRACE("Using default NBD export name \"\"");
 506             name = "";
 507         }
 508         if (fixedNewStyle) {
 509             /* Check our desired export is present in the
 510              * server export list. Since NBD_OPT_EXPORT_NAME
 511              * cannot return an error message, running this
 512              * query gives us good error reporting if the
 513              * server required TLS
 514              */
 515             if (nbd_receive_query_exports(ioc, name, errp) < 0) {
 516                 goto fail;
 517             }
 518         }
 519         /* write the export name */
 520         magic = cpu_to_be64(magic);
 521         if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 522             error_setg(errp, "Failed to send export name magic");
 523             goto fail;
 524         }
 525         opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
 526         if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 527             error_setg(errp, "Failed to send export name option number");
 528             goto fail;
 529         }
 530         namesize = cpu_to_be32(strlen(name));
 531         if (write_sync(ioc, &namesize, sizeof(namesize)) !=
 532             sizeof(namesize)) {
 533             error_setg(errp, "Failed to send export name length");
 534             goto fail;
 535         }
 536         if (write_sync(ioc, (char *)name, strlen(name)) != strlen(name)) {
 537             error_setg(errp, "Failed to send export name");
 538             goto fail;
 539         }
 540
 541         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 542             error_setg(errp, "Failed to read export length");
 543             goto fail;
 544         }
 545         *size = be64_to_cpu(s);
 546
 547         if (read_sync(ioc, flags, sizeof(*flags)) != sizeof(*flags)) {
 548             error_setg(errp, "Failed to read export flags");
 549             goto fail;
 550         }
 551         be16_to_cpus(flags);
 552     } else if (magic == NBD_CLIENT_MAGIC) {
 553         uint32_t oldflags;
 554
 555         if (name) {
 556             error_setg(errp, "Server does not support export names");
 557             goto fail;
 558         }
 559         if (tlscreds) {
 560             error_setg(errp, "Server does not support STARTTLS");
 561             goto fail;
 562         }
 563
 564         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 565             error_setg(errp, "Failed to read export length");
 566             goto fail;
 567         }
 568         *size = be64_to_cpu(s);
 569         TRACE("Size is %" PRIu64, *size);
 570
 571         if (read_sync(ioc, &oldflags, sizeof(oldflags)) != sizeof(oldflags)) {
 572             error_setg(errp, "Failed to read export flags");
 573             goto fail;
 574         }
 575         be32_to_cpus(&oldflags);
 576         if (oldflags & ~0xffff) {
 577             error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
 578             goto fail;
 579         }
 580         *flags = oldflags;
 581     } else {
 582         error_setg(errp, "Bad magic received");
 583         goto fail;
 584     }
 585
 586     TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
 587     if (read_sync(ioc, &buf, 124) != 124) {
 588         error_setg(errp, "Failed to read reserved block");
 589         goto fail;
 590     }
 591     rc = 0;
 592
 593 fail:
 594     return rc;
 595 }
 596
 597 #ifdef __linux__
 598 int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 599 {
 600     unsigned long sectors = size / BDRV_SECTOR_SIZE;
 601     if (size / BDRV_SECTOR_SIZE != sectors) {
 602         LOG("Export size %lld too large for 32-bit kernel", (long long) size);
 603         return -E2BIG;
 604     }
 605
 606     TRACE("Setting NBD socket");
 607
 608     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
 609         int serrno = errno;
 610         LOG("Failed to set NBD socket");
 611         return -serrno;
 612     }
 613
 614     TRACE("Setting block size to %lu", (unsigned long)BDRV_SECTOR_SIZE);
 615
 616     if (ioctl(fd, NBD_SET_BLKSIZE, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
 617         int serrno = errno;
 618         LOG("Failed setting NBD block size");
 619         return -serrno;
 620     }
 621
 622     TRACE("Setting size to %lu block(s)", sectors);
 623     if (size % BDRV_SECTOR_SIZE) {
 624         TRACE("Ignoring trailing %d bytes of export",
 625               (int) (size % BDRV_SECTOR_SIZE));
 626     }
 627
 628     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
 629         int serrno = errno;
 630         LOG("Failed setting size (in blocks)");
 631         return -serrno;
 632     }
 633
 634     if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) flags) < 0) {
 635         if (errno == ENOTTY) {
 636             int read_only = (flags & NBD_FLAG_READ_ONLY) != 0;
 637             TRACE("Setting readonly attribute");
 638
 639             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 640                 int serrno = errno;
 641                 LOG("Failed setting read-only attribute");
 642                 return -serrno;
 643             }
 644         } else {
 645             int serrno = errno;
 646             LOG("Failed setting flags");
 647             return -serrno;
 648         }
 649     }
 650
 651     TRACE("Negotiation ended");
 652
 653     return 0;
 654 }
 655
 656 int nbd_client(int fd)
 657 {
 658     int ret;
 659     int serrno;
 660
 661     TRACE("Doing NBD loop");
 662
 663     ret = ioctl(fd, NBD_DO_IT);
 664     if (ret < 0 && errno == EPIPE) {
 665         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 666          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 667          * that case.
 668          */
 669         ret = 0;
 670     }
 671     serrno = errno;
 672
 673     TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
 674
 675     TRACE("Clearing NBD queue");
 676     ioctl(fd, NBD_CLEAR_QUE);
 677
 678     TRACE("Clearing NBD socket");
 679     ioctl(fd, NBD_CLEAR_SOCK);
 680
 681     errno = serrno;
 682     return ret;
 683 }
 684
 685 int nbd_disconnect(int fd)
 686 {
 687     ioctl(fd, NBD_CLEAR_QUE);
 688     ioctl(fd, NBD_DISCONNECT);
 689     ioctl(fd, NBD_CLEAR_SOCK);
 690     return 0;
 691 }
 692
 693 #else
 694 int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size)
 695 {
 696     return -ENOTSUP;
 697 }
 698
 699 int nbd_client(int fd)
 700 {
 701     return -ENOTSUP;
 702 }
 703 int nbd_disconnect(int fd)
 704 {
 705     return -ENOTSUP;
 706 }
 707 #endif
 708
 709 ssize_t nbd_send_request(QIOChannel *ioc, struct nbd_request *request)
 710 {
 711     uint8_t buf[NBD_REQUEST_SIZE];
 712     ssize_t ret;
 713
 714     TRACE("Sending request to server: "
 715           "{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
 716           ", .type=%" PRIu32 " }",
 717           request->from, request->len, request->handle, request->type);
 718
 719     stl_be_p(buf, NBD_REQUEST_MAGIC);
 720     stl_be_p(buf + 4, request->type);
 721     stq_be_p(buf + 8, request->handle);
 722     stq_be_p(buf + 16, request->from);
 723     stl_be_p(buf + 24, request->len);
 724
 725     ret = write_sync(ioc, buf, sizeof(buf));
 726     if (ret < 0) {
 727         return ret;
 728     }
 729
 730     if (ret != sizeof(buf)) {
 731         LOG("writing to socket failed");
 732         return -EINVAL;
 733     }
 734     return 0;
 735 }
 736
 737 ssize_t nbd_receive_reply(QIOChannel *ioc, struct nbd_reply *reply)
 738 {
 739     uint8_t buf[NBD_REPLY_SIZE];
 740     uint32_t magic;
 741     ssize_t ret;
 742
 743     ret = read_sync(ioc, buf, sizeof(buf));
 744     if (ret < 0) {
 745         return ret;
 746     }
 747
 748     if (ret != sizeof(buf)) {
 749         LOG("read failed");
 750         return -EINVAL;
 751     }
 752
 753     /* Reply
 754        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 755        [ 4 ..  7]    error   (0 == no error)
 756        [ 7 .. 15]    handle
 757      */
 758
 759     magic = ldl_be_p(buf);
 760     reply->error  = ldl_be_p(buf + 4);
 761     reply->handle = ldq_be_p(buf + 8);
 762
 763     reply->error = nbd_errno_to_system_errno(reply->error);
 764
 765     TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
 766           ", handle = %" PRIu64" }",
 767           magic, reply->error, reply->handle);
 768
 769     if (magic != NBD_REPLY_MAGIC) {
 770         LOG("invalid magic (got 0x%" PRIx32 ")", magic);
 771         return -EINVAL;
 772     }
 773     return 0;
 774 }
 775