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     switch (err) {
  27     case NBD_SUCCESS:
  28         return 0;
  29     case NBD_EPERM:
  30         return EPERM;
  31     case NBD_EIO:
  32         return EIO;
  33     case NBD_ENOMEM:
  34         return ENOMEM;
  35     case NBD_ENOSPC:
  36         return ENOSPC;
  37     default:
  38         TRACE("Squashing unexpected error %d to EINVAL", err);
  39         /* fallthrough */
  40     case NBD_EINVAL:
  41         return EINVAL;
  42     }
  43 }
  44
  45 /* Definitions for opaque data types */
  46
  47 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  48
  49 /* That's all folks */
  50
  51 /* Basic flow for negotiation
  52
  53    Server         Client
  54    Negotiate
  55
  56    or
  57
  58    Server         Client
  59    Negotiate #1
  60                   Option
  61    Negotiate #2
  62
  63    ----
  64
  65    followed by
  66
  67    Server         Client
  68                   Request
  69    Response
  70                   Request
  71    Response
  72                   ...
  73    ...
  74                   Request (type == 2)
  75
  76 */
  77
  78 /* Send an option request.
  79  *
  80  * The request is for option @opt, with @data containing @len bytes of
  81  * additional payload for the request (@len may be -1 to treat @data as
  82  * a C string; and @data may be NULL if @len is 0).
  83  * Return 0 if successful, -1 with errp set if it is impossible to
  84  * continue. */
  85 static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
  86                                    uint32_t len, const char *data,
  87                                    Error **errp)
  88 {
  89     nbd_option req;
  90     QEMU_BUILD_BUG_ON(sizeof(req) != 16);
  91
  92     if (len == -1) {
  93         req.length = len = strlen(data);
  94     }
  95     TRACE("Sending option request %" PRIu32", len %" PRIu32, opt, len);
  96
  97     stq_be_p(&req.magic, NBD_OPTS_MAGIC);
  98     stl_be_p(&req.option, opt);
  99     stl_be_p(&req.length, len);
 100
 101     if (write_sync(ioc, &req, sizeof(req)) != sizeof(req)) {
 102         error_setg(errp, "Failed to send option request header");
 103         return -1;
 104     }
 105
 106     if (len && write_sync(ioc, (char *) data, len) != len) {
 107         error_setg(errp, "Failed to send option request data");
 108         return -1;
 109     }
 110
 111     return 0;
 112 }
 113
 114 /* Send NBD_OPT_ABORT as a courtesy to let the server know that we are
 115  * not going to attempt further negotiation. */
 116 static void nbd_send_opt_abort(QIOChannel *ioc)
 117 {
 118     /* Technically, a compliant server is supposed to reply to us; but
 119      * older servers disconnected instead. At any rate, we're allowed
 120      * to disconnect without waiting for the server reply, so we don't
 121      * even care if the request makes it to the server, let alone
 122      * waiting around for whether the server replies. */
 123     nbd_send_option_request(ioc, NBD_OPT_ABORT, 0, NULL, NULL);
 124 }
 125
 126
 127 /* Receive the header of an option reply, which should match the given
 128  * opt.  Read through the length field, but NOT the length bytes of
 129  * payload. Return 0 if successful, -1 with errp set if it is
 130  * impossible to continue. */
 131 static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
 132                                     nbd_opt_reply *reply, Error **errp)
 133 {
 134     QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
 135     if (read_sync(ioc, reply, sizeof(*reply)) != sizeof(*reply)) {
 136         error_setg(errp, "failed to read option reply");
 137         nbd_send_opt_abort(ioc);
 138         return -1;
 139     }
 140     be64_to_cpus(&reply->magic);
 141     be32_to_cpus(&reply->option);
 142     be32_to_cpus(&reply->type);
 143     be32_to_cpus(&reply->length);
 144
 145     TRACE("Received option reply %" PRIx32", type %" PRIx32", len %" PRIu32,
 146           reply->option, reply->type, reply->length);
 147
 148     if (reply->magic != NBD_REP_MAGIC) {
 149         error_setg(errp, "Unexpected option reply magic");
 150         nbd_send_opt_abort(ioc);
 151         return -1;
 152     }
 153     if (reply->option != opt) {
 154         error_setg(errp, "Unexpected option type %x expected %x",
 155                    reply->option, opt);
 156         nbd_send_opt_abort(ioc);
 157         return -1;
 158     }
 159     return 0;
 160 }
 161
 162 /* If reply represents success, return 1 without further action.
 163  * If reply represents an error, consume the optional payload of
 164  * the packet on ioc.  Then return 0 for unsupported (so the client
 165  * can fall back to other approaches), or -1 with errp set for other
 166  * errors.
 167  */
 168 static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply,
 169                                 Error **errp)
 170 {
 171     char *msg = NULL;
 172     int result = -1;
 173
 174     if (!(reply->type & (1 << 31))) {
 175         return 1;
 176     }
 177
 178     if (reply->length) {
 179         if (reply->length > NBD_MAX_BUFFER_SIZE) {
 180             error_setg(errp, "server's error message is too long");
 181             goto cleanup;
 182         }
 183         msg = g_malloc(reply->length + 1);
 184         if (read_sync(ioc, msg, reply->length) != reply->length) {
 185             error_setg(errp, "failed to read option error message");
 186             goto cleanup;
 187         }
 188         msg[reply->length] = '\0';
 189     }
 190
 191     switch (reply->type) {
 192     case NBD_REP_ERR_UNSUP:
 193         TRACE("server doesn't understand request %" PRIx32
 194               ", attempting fallback", reply->option);
 195         result = 0;
 196         goto cleanup;
 197
 198     case NBD_REP_ERR_POLICY:
 199         error_setg(errp, "Denied by server for option %" PRIx32,
 200                    reply->option);
 201         break;
 202
 203     case NBD_REP_ERR_INVALID:
 204         error_setg(errp, "Invalid data length for option %" PRIx32,
 205                    reply->option);
 206         break;
 207
 208     case NBD_REP_ERR_TLS_REQD:
 209         error_setg(errp, "TLS negotiation required before option %" PRIx32,
 210                    reply->option);
 211         break;
 212
 213     default:
 214         error_setg(errp, "Unknown error code when asking for option %" PRIx32,
 215                    reply->option);
 216         break;
 217     }
 218
 219     if (msg) {
 220         error_append_hint(errp, "%s\n", msg);
 221     }
 222
 223  cleanup:
 224     g_free(msg);
 225     if (result < 0) {
 226         nbd_send_opt_abort(ioc);
 227     }
 228     return result;
 229 }
 230
 231 static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
 232 {
 233     nbd_opt_reply reply;
 234     uint32_t len;
 235     uint32_t namelen;
 236     int error;
 237
 238     *name = NULL;
 239     if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
 240         return -1;
 241     }
 242     error = nbd_handle_reply_err(ioc, &reply, errp);
 243     if (error <= 0) {
 244         return error;
 245     }
 246     len = reply.length;
 247
 248     if (reply.type == NBD_REP_ACK) {
 249         if (len != 0) {
 250             error_setg(errp, "length too long for option end");
 251             nbd_send_opt_abort(ioc);
 252             return -1;
 253         }
 254     } else if (reply.type == NBD_REP_SERVER) {
 255         if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
 256             error_setg(errp, "incorrect option length %" PRIu32, len);
 257             nbd_send_opt_abort(ioc);
 258             return -1;
 259         }
 260         if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
 261             error_setg(errp, "failed to read option name length");
 262             nbd_send_opt_abort(ioc);
 263             return -1;
 264         }
 265         namelen = be32_to_cpu(namelen);
 266         len -= sizeof(namelen);
 267         if (len < namelen) {
 268             error_setg(errp, "incorrect option name length");
 269             nbd_send_opt_abort(ioc);
 270             return -1;
 271         }
 272         if (namelen > NBD_MAX_NAME_SIZE) {
 273             error_setg(errp, "export name length too long %" PRIu32, namelen);
 274             nbd_send_opt_abort(ioc);
 275             return -1;
 276         }
 277
 278         *name = g_new0(char, namelen + 1);
 279         if (read_sync(ioc, *name, namelen) != namelen) {
 280             error_setg(errp, "failed to read export name");
 281             g_free(*name);
 282             *name = NULL;
 283             nbd_send_opt_abort(ioc);
 284             return -1;
 285         }
 286         (*name)[namelen] = '\0';
 287         len -= namelen;
 288         if (len) {
 289             char *buf = g_malloc(len + 1);
 290             if (read_sync(ioc, buf, len) != len) {
 291                 error_setg(errp, "failed to read export description");
 292                 g_free(*name);
 293                 g_free(buf);
 294                 *name = NULL;
 295                 nbd_send_opt_abort(ioc);
 296                 return -1;
 297             }
 298             buf[len] = '\0';
 299             TRACE("Ignoring export description: %s", buf);
 300             g_free(buf);
 301         }
 302     } else {
 303         error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
 304                    reply.type, NBD_REP_SERVER);
 305         nbd_send_opt_abort(ioc);
 306         return -1;
 307     }
 308     return 1;
 309 }
 310
 311
 312 static int nbd_receive_query_exports(QIOChannel *ioc,
 313                                      const char *wantname,
 314                                      Error **errp)
 315 {
 316     bool foundExport = false;
 317
 318     TRACE("Querying export list");
 319     if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
 320         return -1;
 321     }
 322
 323     TRACE("Reading available export names");
 324     while (1) {
 325         char *name = NULL;
 326         int ret = nbd_receive_list(ioc, &name, errp);
 327
 328         if (ret < 0) {
 329             g_free(name);
 330             name = NULL;
 331             return -1;
 332         }
 333         if (ret == 0) {
 334             /* Server doesn't support export listing, so
 335              * we will just assume an export with our
 336              * wanted name exists */
 337             foundExport = true;
 338             break;
 339         }
 340         if (name == NULL) {
 341             TRACE("End of export name list");
 342             break;
 343         }
 344         if (g_str_equal(name, wantname)) {
 345             foundExport = true;
 346             TRACE("Found desired export name '%s'", name);
 347         } else {
 348             TRACE("Ignored export name '%s'", name);
 349         }
 350         g_free(name);
 351     }
 352
 353     if (!foundExport) {
 354         error_setg(errp, "No export with name '%s' available", wantname);
 355         nbd_send_opt_abort(ioc);
 356         return -1;
 357     }
 358
 359     return 0;
 360 }
 361
 362 static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
 363                                         QCryptoTLSCreds *tlscreds,
 364                                         const char *hostname, Error **errp)
 365 {
 366     nbd_opt_reply reply;
 367     QIOChannelTLS *tioc;
 368     struct NBDTLSHandshakeData data = { 0 };
 369
 370     TRACE("Requesting TLS from server");
 371     if (nbd_send_option_request(ioc, NBD_OPT_STARTTLS, 0, NULL, errp) < 0) {
 372         return NULL;
 373     }
 374
 375     TRACE("Getting TLS reply from server");
 376     if (nbd_receive_option_reply(ioc, NBD_OPT_STARTTLS, &reply, errp) < 0) {
 377         return NULL;
 378     }
 379
 380     if (reply.type != NBD_REP_ACK) {
 381         error_setg(errp, "Server rejected request to start TLS %" PRIx32,
 382                    reply.type);
 383         nbd_send_opt_abort(ioc);
 384         return NULL;
 385     }
 386
 387     if (reply.length != 0) {
 388         error_setg(errp, "Start TLS response was not zero %" PRIu32,
 389                    reply.length);
 390         nbd_send_opt_abort(ioc);
 391         return NULL;
 392     }
 393
 394     TRACE("TLS request approved, setting up TLS");
 395     tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
 396     if (!tioc) {
 397         return NULL;
 398     }
 399     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
 400     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 401     TRACE("Starting TLS handshake");
 402     qio_channel_tls_handshake(tioc,
 403                               nbd_tls_handshake,
 404                               &data,
 405                               NULL);
 406
 407     if (!data.complete) {
 408         g_main_loop_run(data.loop);
 409     }
 410     g_main_loop_unref(data.loop);
 411     if (data.error) {
 412         error_propagate(errp, data.error);
 413         object_unref(OBJECT(tioc));
 414         return NULL;
 415     }
 416
 417     return QIO_CHANNEL(tioc);
 418 }
 419
 420
 421 int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
 422                           QCryptoTLSCreds *tlscreds, const char *hostname,
 423                           QIOChannel **outioc,
 424                           off_t *size, Error **errp)
 425 {
 426     char buf[256];
 427     uint64_t magic, s;
 428     int rc;
 429
 430     TRACE("Receiving negotiation tlscreds=%p hostname=%s.",
 431           tlscreds, hostname ? hostname : "<null>");
 432
 433     rc = -EINVAL;
 434
 435     if (outioc) {
 436         *outioc = NULL;
 437     }
 438     if (tlscreds && !outioc) {
 439         error_setg(errp, "Output I/O channel required for TLS");
 440         goto fail;
 441     }
 442
 443     if (read_sync(ioc, buf, 8) != 8) {
 444         error_setg(errp, "Failed to read data");
 445         goto fail;
 446     }
 447
 448     buf[8] = '\0';
 449     if (strlen(buf) == 0) {
 450         error_setg(errp, "Server connection closed unexpectedly");
 451         goto fail;
 452     }
 453
 454     TRACE("Magic is %c%c%c%c%c%c%c%c",
 455           qemu_isprint(buf[0]) ? buf[0] : '.',
 456           qemu_isprint(buf[1]) ? buf[1] : '.',
 457           qemu_isprint(buf[2]) ? buf[2] : '.',
 458           qemu_isprint(buf[3]) ? buf[3] : '.',
 459           qemu_isprint(buf[4]) ? buf[4] : '.',
 460           qemu_isprint(buf[5]) ? buf[5] : '.',
 461           qemu_isprint(buf[6]) ? buf[6] : '.',
 462           qemu_isprint(buf[7]) ? buf[7] : '.');
 463
 464     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 465         error_setg(errp, "Invalid magic received");
 466         goto fail;
 467     }
 468
 469     if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 470         error_setg(errp, "Failed to read magic");
 471         goto fail;
 472     }
 473     magic = be64_to_cpu(magic);
 474     TRACE("Magic is 0x%" PRIx64, magic);
 475
 476     if (magic == NBD_OPTS_MAGIC) {
 477         uint32_t clientflags = 0;
 478         uint16_t globalflags;
 479         bool fixedNewStyle = false;
 480
 481         if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
 482             sizeof(globalflags)) {
 483             error_setg(errp, "Failed to read server flags");
 484             goto fail;
 485         }
 486         globalflags = be16_to_cpu(globalflags);
 487         TRACE("Global flags are %" PRIx32, globalflags);
 488         if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
 489             fixedNewStyle = true;
 490             TRACE("Server supports fixed new style");
 491             clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
 492         }
 493         /* client requested flags */
 494         clientflags = cpu_to_be32(clientflags);
 495         if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
 496             sizeof(clientflags)) {
 497             error_setg(errp, "Failed to send clientflags field");
 498             goto fail;
 499         }
 500         if (tlscreds) {
 501             if (fixedNewStyle) {
 502                 *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
 503                 if (!*outioc) {
 504                     goto fail;
 505                 }
 506                 ioc = *outioc;
 507             } else {
 508                 error_setg(errp, "Server does not support STARTTLS");
 509                 goto fail;
 510             }
 511         }
 512         if (!name) {
 513             TRACE("Using default NBD export name \"\"");
 514             name = "";
 515         }
 516         if (fixedNewStyle) {
 517             /* Check our desired export is present in the
 518              * server export list. Since NBD_OPT_EXPORT_NAME
 519              * cannot return an error message, running this
 520              * query gives us good error reporting if the
 521              * server required TLS
 522              */
 523             if (nbd_receive_query_exports(ioc, name, errp) < 0) {
 524                 goto fail;
 525             }
 526         }
 527         /* write the export name request */
 528         if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, name,
 529                                     errp) < 0) {
 530             goto fail;
 531         }
 532
 533         /* Read the response */
 534         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 535             error_setg(errp, "Failed to read export length");
 536             goto fail;
 537         }
 538         *size = be64_to_cpu(s);
 539
 540         if (read_sync(ioc, flags, sizeof(*flags)) != sizeof(*flags)) {
 541             error_setg(errp, "Failed to read export flags");
 542             goto fail;
 543         }
 544         be16_to_cpus(flags);
 545     } else if (magic == NBD_CLIENT_MAGIC) {
 546         uint32_t oldflags;
 547
 548         if (name) {
 549             error_setg(errp, "Server does not support export names");
 550             goto fail;
 551         }
 552         if (tlscreds) {
 553             error_setg(errp, "Server does not support STARTTLS");
 554             goto fail;
 555         }
 556
 557         if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
 558             error_setg(errp, "Failed to read export length");
 559             goto fail;
 560         }
 561         *size = be64_to_cpu(s);
 562         TRACE("Size is %" PRIu64, *size);
 563
 564         if (read_sync(ioc, &oldflags, sizeof(oldflags)) != sizeof(oldflags)) {
 565             error_setg(errp, "Failed to read export flags");
 566             goto fail;
 567         }
 568         be32_to_cpus(&oldflags);
 569         if (oldflags & ~0xffff) {
 570             error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
 571             goto fail;
 572         }
 573         *flags = oldflags;
 574     } else {
 575         error_setg(errp, "Bad magic received");
 576         goto fail;
 577     }
 578
 579     TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
 580     if (read_sync(ioc, &buf, 124) != 124) {
 581         error_setg(errp, "Failed to read reserved block");
 582         goto fail;
 583     }
 584     rc = 0;
 585
 586 fail:
 587     return rc;
 588 }
 589
 590 #ifdef __linux__
 591 int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 592 {
 593     unsigned long sectors = size / BDRV_SECTOR_SIZE;
 594     if (size / BDRV_SECTOR_SIZE != sectors) {
 595         LOG("Export size %lld too large for 32-bit kernel", (long long) size);
 596         return -E2BIG;
 597     }
 598
 599     TRACE("Setting NBD socket");
 600
 601     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
 602         int serrno = errno;
 603         LOG("Failed to set NBD socket");
 604         return -serrno;
 605     }
 606
 607     TRACE("Setting block size to %lu", (unsigned long)BDRV_SECTOR_SIZE);
 608
 609     if (ioctl(fd, NBD_SET_BLKSIZE, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
 610         int serrno = errno;
 611         LOG("Failed setting NBD block size");
 612         return -serrno;
 613     }
 614
 615     TRACE("Setting size to %lu block(s)", sectors);
 616     if (size % BDRV_SECTOR_SIZE) {
 617         TRACE("Ignoring trailing %d bytes of export",
 618               (int) (size % BDRV_SECTOR_SIZE));
 619     }
 620
 621     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
 622         int serrno = errno;
 623         LOG("Failed setting size (in blocks)");
 624         return -serrno;
 625     }
 626
 627     if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) flags) < 0) {
 628         if (errno == ENOTTY) {
 629             int read_only = (flags & NBD_FLAG_READ_ONLY) != 0;
 630             TRACE("Setting readonly attribute");
 631
 632             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 633                 int serrno = errno;
 634                 LOG("Failed setting read-only attribute");
 635                 return -serrno;
 636             }
 637         } else {
 638             int serrno = errno;
 639             LOG("Failed setting flags");
 640             return -serrno;
 641         }
 642     }
 643
 644     TRACE("Negotiation ended");
 645
 646     return 0;
 647 }
 648
 649 int nbd_client(int fd)
 650 {
 651     int ret;
 652     int serrno;
 653
 654     TRACE("Doing NBD loop");
 655
 656     ret = ioctl(fd, NBD_DO_IT);
 657     if (ret < 0 && errno == EPIPE) {
 658         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 659          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 660          * that case.
 661          */
 662         ret = 0;
 663     }
 664     serrno = errno;
 665
 666     TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
 667
 668     TRACE("Clearing NBD queue");
 669     ioctl(fd, NBD_CLEAR_QUE);
 670
 671     TRACE("Clearing NBD socket");
 672     ioctl(fd, NBD_CLEAR_SOCK);
 673
 674     errno = serrno;
 675     return ret;
 676 }
 677
 678 int nbd_disconnect(int fd)
 679 {
 680     ioctl(fd, NBD_CLEAR_QUE);
 681     ioctl(fd, NBD_DISCONNECT);
 682     ioctl(fd, NBD_CLEAR_SOCK);
 683     return 0;
 684 }
 685
 686 #else
 687 int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size)
 688 {
 689     return -ENOTSUP;
 690 }
 691
 692 int nbd_client(int fd)
 693 {
 694     return -ENOTSUP;
 695 }
 696 int nbd_disconnect(int fd)
 697 {
 698     return -ENOTSUP;
 699 }
 700 #endif
 701
 702 ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request)
 703 {
 704     uint8_t buf[NBD_REQUEST_SIZE];
 705     ssize_t ret;
 706
 707     TRACE("Sending request to server: "
 708           "{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
 709           ", .flags = %" PRIx16 ", .type = %" PRIu16 " }",
 710           request->from, request->len, request->handle,
 711           request->flags, request->type);
 712
 713     stl_be_p(buf, NBD_REQUEST_MAGIC);
 714     stw_be_p(buf + 4, request->flags);
 715     stw_be_p(buf + 6, request->type);
 716     stq_be_p(buf + 8, request->handle);
 717     stq_be_p(buf + 16, request->from);
 718     stl_be_p(buf + 24, request->len);
 719
 720     ret = write_sync(ioc, buf, sizeof(buf));
 721     if (ret < 0) {
 722         return ret;
 723     }
 724
 725     if (ret != sizeof(buf)) {
 726         LOG("writing to socket failed");
 727         return -EINVAL;
 728     }
 729     return 0;
 730 }
 731
 732 ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply)
 733 {
 734     uint8_t buf[NBD_REPLY_SIZE];
 735     uint32_t magic;
 736     ssize_t ret;
 737
 738     ret = read_sync(ioc, buf, sizeof(buf));
 739     if (ret < 0) {
 740         return ret;
 741     }
 742
 743     if (ret != sizeof(buf)) {
 744         LOG("read failed");
 745         return -EINVAL;
 746     }
 747
 748     /* Reply
 749        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 750        [ 4 ..  7]    error   (0 == no error)
 751        [ 7 .. 15]    handle
 752      */
 753
 754     magic = ldl_be_p(buf);
 755     reply->error  = ldl_be_p(buf + 4);
 756     reply->handle = ldq_be_p(buf + 8);
 757
 758     reply->error = nbd_errno_to_system_errno(reply->error);
 759
 760     TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
 761           ", handle = %" PRIu64" }",
 762           magic, reply->error, reply->handle);
 763
 764     if (magic != NBD_REPLY_MAGIC) {
 765         LOG("invalid magic (got 0x%" PRIx32 ")", magic);
 766         return -EINVAL;
 767     }
 768     return 0;
 769 }
 770