nbd/server.c

   1 /*
   2  *  Copyright (C) 2016 Red Hat, Inc.
   3  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   4  *
   5  *  Network Block Device Server 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 system_errno_to_nbd_errno(int err)
  25 {
  26     switch (err) {
  27     case 0:
  28         return NBD_SUCCESS;
  29     case EPERM:
  30     case EROFS:
  31         return NBD_EPERM;
  32     case EIO:
  33         return NBD_EIO;
  34     case ENOMEM:
  35         return NBD_ENOMEM;
  36 #ifdef EDQUOT
  37     case EDQUOT:
  38 #endif
  39     case EFBIG:
  40     case ENOSPC:
  41         return NBD_ENOSPC;
  42     case ESHUTDOWN:
  43         return NBD_ESHUTDOWN;
  44     case EINVAL:
  45     default:
  46         return NBD_EINVAL;
  47     }
  48 }
  49
  50 /* Definitions for opaque data types */
  51
  52 typedef struct NBDRequestData NBDRequestData;
  53
  54 struct NBDRequestData {
  55     QSIMPLEQ_ENTRY(NBDRequestData) entry;
  56     NBDClient *client;
  57     uint8_t *data;
  58     bool complete;
  59 };
  60
  61 struct NBDExport {
  62     int refcount;
  63     void (*close)(NBDExport *exp);
  64
  65     BlockBackend *blk;
  66     char *name;
  67     char *description;
  68     off_t dev_offset;
  69     off_t size;
  70     uint16_t nbdflags;
  71     QTAILQ_HEAD(, NBDClient) clients;
  72     QTAILQ_ENTRY(NBDExport) next;
  73
  74     AioContext *ctx;
  75
  76     BlockBackend *eject_notifier_blk;
  77     Notifier eject_notifier;
  78 };
  79
  80 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  81
  82 struct NBDClient {
  83     int refcount;
  84     void (*close)(NBDClient *client);
  85
  86     bool no_zeroes;
  87     NBDExport *exp;
  88     QCryptoTLSCreds *tlscreds;
  89     char *tlsaclname;
  90     QIOChannelSocket *sioc; /* The underlying data channel */
  91     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
  92
  93     Coroutine *recv_coroutine;
  94
  95     CoMutex send_lock;
  96     Coroutine *send_coroutine;
  97
  98     QTAILQ_ENTRY(NBDClient) next;
  99     int nb_requests;
 100     bool closing;
 101 };
 102
 103 /* That's all folks */
 104
 105 static void nbd_client_receive_next_request(NBDClient *client);
 106
 107 static gboolean nbd_negotiate_continue(QIOChannel *ioc,
 108                                        GIOCondition condition,
 109                                        void *opaque)
 110 {
 111     qemu_coroutine_enter(opaque);
 112     return TRUE;
 113 }
 114
 115 static int nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
 116 {
 117     ssize_t ret;
 118     guint watch;
 119
 120     assert(qemu_in_coroutine());
 121     /* Negotiation are always in main loop. */
 122     watch = qio_channel_add_watch(ioc,
 123                                   G_IO_IN,
 124                                   nbd_negotiate_continue,
 125                                   qemu_coroutine_self(),
 126                                   NULL);
 127     ret = read_sync(ioc, buffer, size, NULL);
 128     g_source_remove(watch);
 129     return ret;
 130
 131 }
 132
 133 static int nbd_negotiate_write(QIOChannel *ioc, const void *buffer, size_t size)
 134 {
 135     ssize_t ret;
 136     guint watch;
 137
 138     assert(qemu_in_coroutine());
 139     /* Negotiation are always in main loop. */
 140     watch = qio_channel_add_watch(ioc,
 141                                   G_IO_OUT,
 142                                   nbd_negotiate_continue,
 143                                   qemu_coroutine_self(),
 144                                   NULL);
 145     ret = write_sync(ioc, buffer, size, NULL);
 146     g_source_remove(watch);
 147     return ret;
 148 }
 149
 150 static int nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)
 151 {
 152     ssize_t ret;
 153     uint8_t *buffer = g_malloc(MIN(65536, size));
 154
 155     while (size > 0) {
 156         size_t count = MIN(65536, size);
 157         ret = nbd_negotiate_read(ioc, buffer, count);
 158         if (ret < 0) {
 159             g_free(buffer);
 160             return ret;
 161         }
 162
 163         size -= count;
 164     }
 165
 166     g_free(buffer);
 167     return 0;
 168 }
 169
 170 /* Basic flow for negotiation
 171
 172    Server         Client
 173    Negotiate
 174
 175    or
 176
 177    Server         Client
 178    Negotiate #1
 179                   Option
 180    Negotiate #2
 181
 182    ----
 183
 184    followed by
 185
 186    Server         Client
 187                   Request
 188    Response
 189                   Request
 190    Response
 191                   ...
 192    ...
 193                   Request (type == 2)
 194
 195 */
 196
 197 /* Send a reply header, including length, but no payload.
 198  * Return -errno on error, 0 on success. */
 199 static int nbd_negotiate_send_rep_len(QIOChannel *ioc, uint32_t type,
 200                                       uint32_t opt, uint32_t len)
 201 {
 202     uint64_t magic;
 203
 204     TRACE("Reply opt=%" PRIx32 " type=%" PRIx32 " len=%" PRIu32,
 205           type, opt, len);
 206
 207     magic = cpu_to_be64(NBD_REP_MAGIC);
 208     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) < 0) {
 209         LOG("write failed (rep magic)");
 210         return -EINVAL;
 211     }
 212     opt = cpu_to_be32(opt);
 213     if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) < 0) {
 214         LOG("write failed (rep opt)");
 215         return -EINVAL;
 216     }
 217     type = cpu_to_be32(type);
 218     if (nbd_negotiate_write(ioc, &type, sizeof(type)) < 0) {
 219         LOG("write failed (rep type)");
 220         return -EINVAL;
 221     }
 222     len = cpu_to_be32(len);
 223     if (nbd_negotiate_write(ioc, &len, sizeof(len)) < 0) {
 224         LOG("write failed (rep data length)");
 225         return -EINVAL;
 226     }
 227     return 0;
 228 }
 229
 230 /* Send a reply header with default 0 length.
 231  * Return -errno on error, 0 on success. */
 232 static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
 233 {
 234     return nbd_negotiate_send_rep_len(ioc, type, opt, 0);
 235 }
 236
 237 /* Send an error reply.
 238  * Return -errno on error, 0 on success. */
 239 static int GCC_FMT_ATTR(4, 5)
 240 nbd_negotiate_send_rep_err(QIOChannel *ioc, uint32_t type,
 241                            uint32_t opt, const char *fmt, ...)
 242 {
 243     va_list va;
 244     char *msg;
 245     int ret;
 246     size_t len;
 247
 248     va_start(va, fmt);
 249     msg = g_strdup_vprintf(fmt, va);
 250     va_end(va);
 251     len = strlen(msg);
 252     assert(len < 4096);
 253     TRACE("sending error message \"%s\"", msg);
 254     ret = nbd_negotiate_send_rep_len(ioc, type, opt, len);
 255     if (ret < 0) {
 256         goto out;
 257     }
 258     if (nbd_negotiate_write(ioc, msg, len) < 0) {
 259         LOG("write failed (error message)");
 260         ret = -EIO;
 261     } else {
 262         ret = 0;
 263     }
 264 out:
 265     g_free(msg);
 266     return ret;
 267 }
 268
 269 /* Send a single NBD_REP_SERVER reply to NBD_OPT_LIST, including payload.
 270  * Return -errno on error, 0 on success. */
 271 static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
 272 {
 273     size_t name_len, desc_len;
 274     uint32_t len;
 275     const char *name = exp->name ? exp->name : "";
 276     const char *desc = exp->description ? exp->description : "";
 277     int rc;
 278
 279     TRACE("Advertising export name '%s' description '%s'", name, desc);
 280     name_len = strlen(name);
 281     desc_len = strlen(desc);
 282     len = name_len + desc_len + sizeof(len);
 283     rc = nbd_negotiate_send_rep_len(ioc, NBD_REP_SERVER, NBD_OPT_LIST, len);
 284     if (rc < 0) {
 285         return rc;
 286     }
 287
 288     len = cpu_to_be32(name_len);
 289     if (nbd_negotiate_write(ioc, &len, sizeof(len)) < 0) {
 290         LOG("write failed (name length)");
 291         return -EINVAL;
 292     }
 293     if (nbd_negotiate_write(ioc, name, name_len) < 0) {
 294         LOG("write failed (name buffer)");
 295         return -EINVAL;
 296     }
 297     if (nbd_negotiate_write(ioc, desc, desc_len) < 0) {
 298         LOG("write failed (description buffer)");
 299         return -EINVAL;
 300     }
 301     return 0;
 302 }
 303
 304 /* Process the NBD_OPT_LIST command, with a potential series of replies.
 305  * Return -errno on error, 0 on success. */
 306 static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
 307 {
 308     NBDExport *exp;
 309
 310     if (length) {
 311         if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
 312             return -EIO;
 313         }
 314         return nbd_negotiate_send_rep_err(client->ioc,
 315                                           NBD_REP_ERR_INVALID, NBD_OPT_LIST,
 316                                           "OPT_LIST should not have length");
 317     }
 318
 319     /* For each export, send a NBD_REP_SERVER reply. */
 320     QTAILQ_FOREACH(exp, &exports, next) {
 321         if (nbd_negotiate_send_rep_list(client->ioc, exp)) {
 322             return -EINVAL;
 323         }
 324     }
 325     /* Finish with a NBD_REP_ACK. */
 326     return nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, NBD_OPT_LIST);
 327 }
 328
 329 static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
 330 {
 331     int rc = -EINVAL;
 332     char name[NBD_MAX_NAME_SIZE + 1];
 333
 334     /* Client sends:
 335         [20 ..  xx]   export name (length bytes)
 336      */
 337     TRACE("Checking length");
 338     if (length >= sizeof(name)) {
 339         LOG("Bad length received");
 340         goto fail;
 341     }
 342     if (nbd_negotiate_read(client->ioc, name, length) < 0) {
 343         LOG("read failed");
 344         goto fail;
 345     }
 346     name[length] = '\0';
 347
 348     TRACE("Client requested export '%s'", name);
 349
 350     client->exp = nbd_export_find(name);
 351     if (!client->exp) {
 352         LOG("export not found");
 353         goto fail;
 354     }
 355
 356     QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
 357     nbd_export_get(client->exp);
 358     rc = 0;
 359 fail:
 360     return rc;
 361 }
 362
 363 /* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the
 364  * new channel for all further (now-encrypted) communication. */
 365 static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
 366                                                  uint32_t length)
 367 {
 368     QIOChannel *ioc;
 369     QIOChannelTLS *tioc;
 370     struct NBDTLSHandshakeData data = { 0 };
 371
 372     TRACE("Setting up TLS");
 373     ioc = client->ioc;
 374     if (length) {
 375         if (nbd_negotiate_drop_sync(ioc, length) < 0) {
 376             return NULL;
 377         }
 378         nbd_negotiate_send_rep_err(ioc, NBD_REP_ERR_INVALID, NBD_OPT_STARTTLS,
 379                                    "OPT_STARTTLS should not have length");
 380         return NULL;
 381     }
 382
 383     if (nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK,
 384                                NBD_OPT_STARTTLS) < 0) {
 385         return NULL;
 386     }
 387
 388     tioc = qio_channel_tls_new_server(ioc,
 389                                       client->tlscreds,
 390                                       client->tlsaclname,
 391                                       NULL);
 392     if (!tioc) {
 393         return NULL;
 394     }
 395
 396     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-server-tls");
 397     TRACE("Starting TLS handshake");
 398     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 399     qio_channel_tls_handshake(tioc,
 400                               nbd_tls_handshake,
 401                               &data,
 402                               NULL);
 403
 404     if (!data.complete) {
 405         g_main_loop_run(data.loop);
 406     }
 407     g_main_loop_unref(data.loop);
 408     if (data.error) {
 409         object_unref(OBJECT(tioc));
 410         error_free(data.error);
 411         return NULL;
 412     }
 413
 414     return QIO_CHANNEL(tioc);
 415 }
 416
 417
 418 /* Process all NBD_OPT_* client option commands.
 419  * Return -errno on error, 0 on success. */
 420 static int nbd_negotiate_options(NBDClient *client)
 421 {
 422     uint32_t flags;
 423     bool fixedNewstyle = false;
 424
 425     /* Client sends:
 426         [ 0 ..   3]   client flags
 427
 428         [ 0 ..   7]   NBD_OPTS_MAGIC
 429         [ 8 ..  11]   NBD option
 430         [12 ..  15]   Data length
 431         ...           Rest of request
 432
 433         [ 0 ..   7]   NBD_OPTS_MAGIC
 434         [ 8 ..  11]   Second NBD option
 435         [12 ..  15]   Data length
 436         ...           Rest of request
 437     */
 438
 439     if (nbd_negotiate_read(client->ioc, &flags, sizeof(flags)) < 0) {
 440         LOG("read failed");
 441         return -EIO;
 442     }
 443     TRACE("Checking client flags");
 444     be32_to_cpus(&flags);
 445     if (flags & NBD_FLAG_C_FIXED_NEWSTYLE) {
 446         TRACE("Client supports fixed newstyle handshake");
 447         fixedNewstyle = true;
 448         flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE;
 449     }
 450     if (flags & NBD_FLAG_C_NO_ZEROES) {
 451         TRACE("Client supports no zeroes at handshake end");
 452         client->no_zeroes = true;
 453         flags &= ~NBD_FLAG_C_NO_ZEROES;
 454     }
 455     if (flags != 0) {
 456         TRACE("Unknown client flags 0x%" PRIx32 " received", flags);
 457         return -EIO;
 458     }
 459
 460     while (1) {
 461         int ret;
 462         uint32_t clientflags, length;
 463         uint64_t magic;
 464
 465         if (nbd_negotiate_read(client->ioc, &magic, sizeof(magic)) < 0) {
 466             LOG("read failed");
 467             return -EINVAL;
 468         }
 469         TRACE("Checking opts magic");
 470         if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
 471             LOG("Bad magic received");
 472             return -EINVAL;
 473         }
 474
 475         if (nbd_negotiate_read(client->ioc, &clientflags,
 476                                sizeof(clientflags)) < 0)
 477         {
 478             LOG("read failed");
 479             return -EINVAL;
 480         }
 481         clientflags = be32_to_cpu(clientflags);
 482
 483         if (nbd_negotiate_read(client->ioc, &length, sizeof(length)) < 0) {
 484             LOG("read failed");
 485             return -EINVAL;
 486         }
 487         length = be32_to_cpu(length);
 488
 489         TRACE("Checking option 0x%" PRIx32, clientflags);
 490         if (client->tlscreds &&
 491             client->ioc == (QIOChannel *)client->sioc) {
 492             QIOChannel *tioc;
 493             if (!fixedNewstyle) {
 494                 TRACE("Unsupported option 0x%" PRIx32, clientflags);
 495                 return -EINVAL;
 496             }
 497             switch (clientflags) {
 498             case NBD_OPT_STARTTLS:
 499                 tioc = nbd_negotiate_handle_starttls(client, length);
 500                 if (!tioc) {
 501                     return -EIO;
 502                 }
 503                 object_unref(OBJECT(client->ioc));
 504                 client->ioc = QIO_CHANNEL(tioc);
 505                 break;
 506
 507             case NBD_OPT_EXPORT_NAME:
 508                 /* No way to return an error to client, so drop connection */
 509                 TRACE("Option 0x%x not permitted before TLS", clientflags);
 510                 return -EINVAL;
 511
 512             default:
 513                 if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
 514                     return -EIO;
 515                 }
 516                 ret = nbd_negotiate_send_rep_err(client->ioc,
 517                                                  NBD_REP_ERR_TLS_REQD,
 518                                                  clientflags,
 519                                                  "Option 0x%" PRIx32
 520                                                  "not permitted before TLS",
 521                                                  clientflags);
 522                 if (ret < 0) {
 523                     return ret;
 524                 }
 525                 /* Let the client keep trying, unless they asked to quit */
 526                 if (clientflags == NBD_OPT_ABORT) {
 527                     return -EINVAL;
 528                 }
 529                 break;
 530             }
 531         } else if (fixedNewstyle) {
 532             switch (clientflags) {
 533             case NBD_OPT_LIST:
 534                 ret = nbd_negotiate_handle_list(client, length);
 535                 if (ret < 0) {
 536                     return ret;
 537                 }
 538                 break;
 539
 540             case NBD_OPT_ABORT:
 541                 /* NBD spec says we must try to reply before
 542                  * disconnecting, but that we must also tolerate
 543                  * guests that don't wait for our reply. */
 544                 nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, clientflags);
 545                 return -EINVAL;
 546
 547             case NBD_OPT_EXPORT_NAME:
 548                 return nbd_negotiate_handle_export_name(client, length);
 549
 550             case NBD_OPT_STARTTLS:
 551                 if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
 552                     return -EIO;
 553                 }
 554                 if (client->tlscreds) {
 555                     ret = nbd_negotiate_send_rep_err(client->ioc,
 556                                                      NBD_REP_ERR_INVALID,
 557                                                      clientflags,
 558                                                      "TLS already enabled");
 559                 } else {
 560                     ret = nbd_negotiate_send_rep_err(client->ioc,
 561                                                      NBD_REP_ERR_POLICY,
 562                                                      clientflags,
 563                                                      "TLS not configured");
 564                 }
 565                 if (ret < 0) {
 566                     return ret;
 567                 }
 568                 break;
 569             default:
 570                 if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
 571                     return -EIO;
 572                 }
 573                 ret = nbd_negotiate_send_rep_err(client->ioc,
 574                                                  NBD_REP_ERR_UNSUP,
 575                                                  clientflags,
 576                                                  "Unsupported option 0x%"
 577                                                  PRIx32,
 578                                                  clientflags);
 579                 if (ret < 0) {
 580                     return ret;
 581                 }
 582                 break;
 583             }
 584         } else {
 585             /*
 586              * If broken new-style we should drop the connection
 587              * for anything except NBD_OPT_EXPORT_NAME
 588              */
 589             switch (clientflags) {
 590             case NBD_OPT_EXPORT_NAME:
 591                 return nbd_negotiate_handle_export_name(client, length);
 592
 593             default:
 594                 TRACE("Unsupported option 0x%" PRIx32, clientflags);
 595                 return -EINVAL;
 596             }
 597         }
 598     }
 599 }
 600
 601 typedef struct {
 602     NBDClient *client;
 603     Coroutine *co;
 604 } NBDClientNewData;
 605
 606 static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
 607 {
 608     NBDClient *client = data->client;
 609     char buf[8 + 8 + 8 + 128];
 610     int rc;
 611     const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
 612                               NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA |
 613                               NBD_FLAG_SEND_WRITE_ZEROES);
 614     bool oldStyle;
 615     size_t len;
 616
 617     /* Old style negotiation header without options
 618         [ 0 ..   7]   passwd       ("NBDMAGIC")
 619         [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
 620         [16 ..  23]   size
 621         [24 ..  25]   server flags (0)
 622         [26 ..  27]   export flags
 623         [28 .. 151]   reserved     (0)
 624
 625        New style negotiation header with options
 626         [ 0 ..   7]   passwd       ("NBDMAGIC")
 627         [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
 628         [16 ..  17]   server flags (0)
 629         ....options sent....
 630         [18 ..  25]   size
 631         [26 ..  27]   export flags
 632         [28 .. 151]   reserved     (0, omit if no_zeroes)
 633      */
 634
 635     qio_channel_set_blocking(client->ioc, false, NULL);
 636     rc = -EINVAL;
 637
 638     TRACE("Beginning negotiation.");
 639     memset(buf, 0, sizeof(buf));
 640     memcpy(buf, "NBDMAGIC", 8);
 641
 642     oldStyle = client->exp != NULL && !client->tlscreds;
 643     if (oldStyle) {
 644         TRACE("advertising size %" PRIu64 " and flags %x",
 645               client->exp->size, client->exp->nbdflags | myflags);
 646         stq_be_p(buf + 8, NBD_CLIENT_MAGIC);
 647         stq_be_p(buf + 16, client->exp->size);
 648         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 649     } else {
 650         stq_be_p(buf + 8, NBD_OPTS_MAGIC);
 651         stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES);
 652     }
 653
 654     if (oldStyle) {
 655         if (client->tlscreds) {
 656             TRACE("TLS cannot be enabled with oldstyle protocol");
 657             goto fail;
 658         }
 659         if (nbd_negotiate_write(client->ioc, buf, sizeof(buf)) < 0) {
 660             LOG("write failed");
 661             goto fail;
 662         }
 663     } else {
 664         if (nbd_negotiate_write(client->ioc, buf, 18) < 0) {
 665             LOG("write failed");
 666             goto fail;
 667         }
 668         rc = nbd_negotiate_options(client);
 669         if (rc != 0) {
 670             LOG("option negotiation failed");
 671             goto fail;
 672         }
 673
 674         TRACE("advertising size %" PRIu64 " and flags %x",
 675               client->exp->size, client->exp->nbdflags | myflags);
 676         stq_be_p(buf + 18, client->exp->size);
 677         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 678         len = client->no_zeroes ? 10 : sizeof(buf) - 18;
 679         if (nbd_negotiate_write(client->ioc, buf + 18, len) < 0) {
 680             LOG("write failed");
 681             goto fail;
 682         }
 683     }
 684
 685     TRACE("Negotiation succeeded.");
 686     rc = 0;
 687 fail:
 688     return rc;
 689 }
 690
 691 static ssize_t nbd_receive_request(QIOChannel *ioc, NBDRequest *request)
 692 {
 693     uint8_t buf[NBD_REQUEST_SIZE];
 694     uint32_t magic;
 695     ssize_t ret;
 696
 697     ret = read_sync(ioc, buf, sizeof(buf), NULL);
 698     if (ret < 0) {
 699         return ret;
 700     }
 701
 702     /* Request
 703        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
 704        [ 4 ..  5]   flags   (NBD_CMD_FLAG_FUA, ...)
 705        [ 6 ..  7]   type    (NBD_CMD_READ, ...)
 706        [ 8 .. 15]   handle
 707        [16 .. 23]   from
 708        [24 .. 27]   len
 709      */
 710
 711     magic = ldl_be_p(buf);
 712     request->flags  = lduw_be_p(buf + 4);
 713     request->type   = lduw_be_p(buf + 6);
 714     request->handle = ldq_be_p(buf + 8);
 715     request->from   = ldq_be_p(buf + 16);
 716     request->len    = ldl_be_p(buf + 24);
 717
 718     TRACE("Got request: { magic = 0x%" PRIx32 ", .flags = %" PRIx16
 719           ", .type = %" PRIx16 ", from = %" PRIu64 ", len = %" PRIu32 " }",
 720           magic, request->flags, request->type, request->from, request->len);
 721
 722     if (magic != NBD_REQUEST_MAGIC) {
 723         LOG("invalid magic (got 0x%" PRIx32 ")", magic);
 724         return -EINVAL;
 725     }
 726     return 0;
 727 }
 728
 729 static ssize_t nbd_send_reply(QIOChannel *ioc, NBDReply *reply)
 730 {
 731     uint8_t buf[NBD_REPLY_SIZE];
 732
 733     reply->error = system_errno_to_nbd_errno(reply->error);
 734
 735     TRACE("Sending response to client: { .error = %" PRId32
 736           ", handle = %" PRIu64 " }",
 737           reply->error, reply->handle);
 738
 739     /* Reply
 740        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 741        [ 4 ..  7]    error   (0 == no error)
 742        [ 7 .. 15]    handle
 743      */
 744     stl_be_p(buf, NBD_REPLY_MAGIC);
 745     stl_be_p(buf + 4, reply->error);
 746     stq_be_p(buf + 8, reply->handle);
 747
 748     return write_sync(ioc, buf, sizeof(buf), NULL);
 749 }
 750
 751 #define MAX_NBD_REQUESTS 16
 752
 753 void nbd_client_get(NBDClient *client)
 754 {
 755     client->refcount++;
 756 }
 757
 758 void nbd_client_put(NBDClient *client)
 759 {
 760     if (--client->refcount == 0) {
 761         /* The last reference should be dropped by client->close,
 762          * which is called by client_close.
 763          */
 764         assert(client->closing);
 765
 766         qio_channel_detach_aio_context(client->ioc);
 767         object_unref(OBJECT(client->sioc));
 768         object_unref(OBJECT(client->ioc));
 769         if (client->tlscreds) {
 770             object_unref(OBJECT(client->tlscreds));
 771         }
 772         g_free(client->tlsaclname);
 773         if (client->exp) {
 774             QTAILQ_REMOVE(&client->exp->clients, client, next);
 775             nbd_export_put(client->exp);
 776         }
 777         g_free(client);
 778     }
 779 }
 780
 781 static void client_close(NBDClient *client)
 782 {
 783     if (client->closing) {
 784         return;
 785     }
 786
 787     client->closing = true;
 788
 789     /* Force requests to finish.  They will drop their own references,
 790      * then we'll close the socket and free the NBDClient.
 791      */
 792     qio_channel_shutdown(client->ioc, QIO_CHANNEL_SHUTDOWN_BOTH,
 793                          NULL);
 794
 795     /* Also tell the client, so that they release their reference.  */
 796     if (client->close) {
 797         client->close(client);
 798     }
 799 }
 800
 801 static NBDRequestData *nbd_request_get(NBDClient *client)
 802 {
 803     NBDRequestData *req;
 804
 805     assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
 806     client->nb_requests++;
 807
 808     req = g_new0(NBDRequestData, 1);
 809     nbd_client_get(client);
 810     req->client = client;
 811     return req;
 812 }
 813
 814 static void nbd_request_put(NBDRequestData *req)
 815 {
 816     NBDClient *client = req->client;
 817
 818     if (req->data) {
 819         qemu_vfree(req->data);
 820     }
 821     g_free(req);
 822
 823     client->nb_requests--;
 824     nbd_client_receive_next_request(client);
 825
 826     nbd_client_put(client);
 827 }
 828
 829 static void blk_aio_attached(AioContext *ctx, void *opaque)
 830 {
 831     NBDExport *exp = opaque;
 832     NBDClient *client;
 833
 834     TRACE("Export %s: Attaching clients to AIO context %p\n", exp->name, ctx);
 835
 836     exp->ctx = ctx;
 837
 838     QTAILQ_FOREACH(client, &exp->clients, next) {
 839         qio_channel_attach_aio_context(client->ioc, ctx);
 840         if (client->recv_coroutine) {
 841             aio_co_schedule(ctx, client->recv_coroutine);
 842         }
 843         if (client->send_coroutine) {
 844             aio_co_schedule(ctx, client->send_coroutine);
 845         }
 846     }
 847 }
 848
 849 static void blk_aio_detach(void *opaque)
 850 {
 851     NBDExport *exp = opaque;
 852     NBDClient *client;
 853
 854     TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
 855
 856     QTAILQ_FOREACH(client, &exp->clients, next) {
 857         qio_channel_detach_aio_context(client->ioc);
 858     }
 859
 860     exp->ctx = NULL;
 861 }
 862
 863 static void nbd_eject_notifier(Notifier *n, void *data)
 864 {
 865     NBDExport *exp = container_of(n, NBDExport, eject_notifier);
 866     nbd_export_close(exp);
 867 }
 868
 869 NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
 870                           uint16_t nbdflags, void (*close)(NBDExport *),
 871                           bool writethrough, BlockBackend *on_eject_blk,
 872                           Error **errp)
 873 {
 874     BlockBackend *blk;
 875     NBDExport *exp = g_malloc0(sizeof(NBDExport));
 876     uint64_t perm;
 877     int ret;
 878
 879     /* Don't allow resize while the NBD server is running, otherwise we don't
 880      * care what happens with the node. */
 881     perm = BLK_PERM_CONSISTENT_READ;
 882     if ((nbdflags & NBD_FLAG_READ_ONLY) == 0) {
 883         perm |= BLK_PERM_WRITE;
 884     }
 885     blk = blk_new(perm, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
 886                         BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD);
 887     ret = blk_insert_bs(blk, bs, errp);
 888     if (ret < 0) {
 889         goto fail;
 890     }
 891     blk_set_enable_write_cache(blk, !writethrough);
 892
 893     exp->refcount = 1;
 894     QTAILQ_INIT(&exp->clients);
 895     exp->blk = blk;
 896     exp->dev_offset = dev_offset;
 897     exp->nbdflags = nbdflags;
 898     exp->size = size < 0 ? blk_getlength(blk) : size;
 899     if (exp->size < 0) {
 900         error_setg_errno(errp, -exp->size,
 901                          "Failed to determine the NBD export's length");
 902         goto fail;
 903     }
 904     exp->size -= exp->size % BDRV_SECTOR_SIZE;
 905
 906     exp->close = close;
 907     exp->ctx = blk_get_aio_context(blk);
 908     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 909
 910     if (on_eject_blk) {
 911         blk_ref(on_eject_blk);
 912         exp->eject_notifier_blk = on_eject_blk;
 913         exp->eject_notifier.notify = nbd_eject_notifier;
 914         blk_add_remove_bs_notifier(on_eject_blk, &exp->eject_notifier);
 915     }
 916
 917     /*
 918      * NBD exports are used for non-shared storage migration.  Make sure
 919      * that BDRV_O_INACTIVE is cleared and the image is ready for write
 920      * access since the export could be available before migration handover.
 921      */
 922     aio_context_acquire(exp->ctx);
 923     blk_invalidate_cache(blk, NULL);
 924     aio_context_release(exp->ctx);
 925     return exp;
 926
 927 fail:
 928     blk_unref(blk);
 929     g_free(exp);
 930     return NULL;
 931 }
 932
 933 NBDExport *nbd_export_find(const char *name)
 934 {
 935     NBDExport *exp;
 936     QTAILQ_FOREACH(exp, &exports, next) {
 937         if (strcmp(name, exp->name) == 0) {
 938             return exp;
 939         }
 940     }
 941
 942     return NULL;
 943 }
 944
 945 void nbd_export_set_name(NBDExport *exp, const char *name)
 946 {
 947     if (exp->name == name) {
 948         return;
 949     }
 950
 951     nbd_export_get(exp);
 952     if (exp->name != NULL) {
 953         g_free(exp->name);
 954         exp->name = NULL;
 955         QTAILQ_REMOVE(&exports, exp, next);
 956         nbd_export_put(exp);
 957     }
 958     if (name != NULL) {
 959         nbd_export_get(exp);
 960         exp->name = g_strdup(name);
 961         QTAILQ_INSERT_TAIL(&exports, exp, next);
 962     }
 963     nbd_export_put(exp);
 964 }
 965
 966 void nbd_export_set_description(NBDExport *exp, const char *description)
 967 {
 968     g_free(exp->description);
 969     exp->description = g_strdup(description);
 970 }
 971
 972 void nbd_export_close(NBDExport *exp)
 973 {
 974     NBDClient *client, *next;
 975
 976     nbd_export_get(exp);
 977     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
 978         client_close(client);
 979     }
 980     nbd_export_set_name(exp, NULL);
 981     nbd_export_set_description(exp, NULL);
 982     nbd_export_put(exp);
 983 }
 984
 985 void nbd_export_get(NBDExport *exp)
 986 {
 987     assert(exp->refcount > 0);
 988     exp->refcount++;
 989 }
 990
 991 void nbd_export_put(NBDExport *exp)
 992 {
 993     assert(exp->refcount > 0);
 994     if (exp->refcount == 1) {
 995         nbd_export_close(exp);
 996     }
 997
 998     if (--exp->refcount == 0) {
 999         assert(exp->name == NULL);
1000         assert(exp->description == NULL);
1001
1002         if (exp->close) {
1003             exp->close(exp);
1004         }
1005
1006         if (exp->blk) {
1007             if (exp->eject_notifier_blk) {
1008                 notifier_remove(&exp->eject_notifier);
1009                 blk_unref(exp->eject_notifier_blk);
1010             }
1011             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
1012                                             blk_aio_detach, exp);
1013             blk_unref(exp->blk);
1014             exp->blk = NULL;
1015         }
1016
1017         g_free(exp);
1018     }
1019 }
1020
1021 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
1022 {
1023     return exp->blk;
1024 }
1025
1026 void nbd_export_close_all(void)
1027 {
1028     NBDExport *exp, *next;
1029
1030     QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
1031         nbd_export_close(exp);
1032     }
1033 }
1034
1035 static ssize_t nbd_co_send_reply(NBDRequestData *req, NBDReply *reply,
1036                                  int len)
1037 {
1038     NBDClient *client = req->client;
1039     ssize_t rc, ret;
1040
1041     g_assert(qemu_in_coroutine());
1042     qemu_co_mutex_lock(&client->send_lock);
1043     client->send_coroutine = qemu_coroutine_self();
1044
1045     if (!len) {
1046         rc = nbd_send_reply(client->ioc, reply);
1047     } else {
1048         qio_channel_set_cork(client->ioc, true);
1049         rc = nbd_send_reply(client->ioc, reply);
1050         if (rc >= 0) {
1051             ret = write_sync(client->ioc, req->data, len, NULL);
1052             if (ret < 0) {
1053                 rc = -EIO;
1054             }
1055         }
1056         qio_channel_set_cork(client->ioc, false);
1057     }
1058
1059     client->send_coroutine = NULL;
1060     qemu_co_mutex_unlock(&client->send_lock);
1061     return rc;
1062 }
1063
1064 /* Collect a client request.  Return 0 if request looks valid, -EAGAIN
1065  * to keep trying the collection, -EIO to drop connection right away,
1066  * and any other negative value to report an error to the client
1067  * (although the caller may still need to disconnect after reporting
1068  * the error).  */
1069 static ssize_t nbd_co_receive_request(NBDRequestData *req,
1070                                       NBDRequest *request)
1071 {
1072     NBDClient *client = req->client;
1073     ssize_t rc;
1074
1075     g_assert(qemu_in_coroutine());
1076     assert(client->recv_coroutine == qemu_coroutine_self());
1077     rc = nbd_receive_request(client->ioc, request);
1078     if (rc < 0) {
1079         if (rc != -EAGAIN) {
1080             rc = -EIO;
1081         }
1082         goto out;
1083     }
1084
1085     TRACE("Decoding type");
1086
1087     if (request->type != NBD_CMD_WRITE) {
1088         /* No payload, we are ready to read the next request.  */
1089         req->complete = true;
1090     }
1091
1092     if (request->type == NBD_CMD_DISC) {
1093         /* Special case: we're going to disconnect without a reply,
1094          * whether or not flags, from, or len are bogus */
1095         TRACE("Request type is DISCONNECT");
1096         rc = -EIO;
1097         goto out;
1098     }
1099
1100     /* Check for sanity in the parameters, part 1.  Defer as many
1101      * checks as possible until after reading any NBD_CMD_WRITE
1102      * payload, so we can try and keep the connection alive.  */
1103     if ((request->from + request->len) < request->from) {
1104         LOG("integer overflow detected, you're probably being attacked");
1105         rc = -EINVAL;
1106         goto out;
1107     }
1108
1109     if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE) {
1110         if (request->len > NBD_MAX_BUFFER_SIZE) {
1111             LOG("len (%" PRIu32" ) is larger than max len (%u)",
1112                 request->len, NBD_MAX_BUFFER_SIZE);
1113             rc = -EINVAL;
1114             goto out;
1115         }
1116
1117         req->data = blk_try_blockalign(client->exp->blk, request->len);
1118         if (req->data == NULL) {
1119             rc = -ENOMEM;
1120             goto out;
1121         }
1122     }
1123     if (request->type == NBD_CMD_WRITE) {
1124         TRACE("Reading %" PRIu32 " byte(s)", request->len);
1125
1126         if (read_sync(client->ioc, req->data, request->len, NULL) < 0) {
1127             LOG("reading from socket failed");
1128             rc = -EIO;
1129             goto out;
1130         }
1131         req->complete = true;
1132     }
1133
1134     /* Sanity checks, part 2. */
1135     if (request->from + request->len > client->exp->size) {
1136         LOG("operation past EOF; From: %" PRIu64 ", Len: %" PRIu32
1137             ", Size: %" PRIu64, request->from, request->len,
1138             (uint64_t)client->exp->size);
1139         rc = request->type == NBD_CMD_WRITE ? -ENOSPC : -EINVAL;
1140         goto out;
1141     }
1142     if (request->flags & ~(NBD_CMD_FLAG_FUA | NBD_CMD_FLAG_NO_HOLE)) {
1143         LOG("unsupported flags (got 0x%x)", request->flags);
1144         rc = -EINVAL;
1145         goto out;
1146     }
1147     if (request->type != NBD_CMD_WRITE_ZEROES &&
1148         (request->flags & NBD_CMD_FLAG_NO_HOLE)) {
1149         LOG("unexpected flags (got 0x%x)", request->flags);
1150         rc = -EINVAL;
1151         goto out;
1152     }
1153
1154     rc = 0;
1155
1156 out:
1157     client->recv_coroutine = NULL;
1158     nbd_client_receive_next_request(client);
1159
1160     return rc;
1161 }
1162
1163 /* Owns a reference to the NBDClient passed as opaque.  */
1164 static coroutine_fn void nbd_trip(void *opaque)
1165 {
1166     NBDClient *client = opaque;
1167     NBDExport *exp = client->exp;
1168     NBDRequestData *req;
1169     NBDRequest request = { 0 };    /* GCC thinks it can be used uninitialized */
1170     NBDReply reply;
1171     ssize_t ret;
1172     int flags;
1173
1174     TRACE("Reading request.");
1175     if (client->closing) {
1176         nbd_client_put(client);
1177         return;
1178     }
1179
1180     req = nbd_request_get(client);
1181     ret = nbd_co_receive_request(req, &request);
1182     if (ret == -EAGAIN) {
1183         goto done;
1184     }
1185     if (ret == -EIO) {
1186         goto out;
1187     }
1188
1189     reply.handle = request.handle;
1190     reply.error = 0;
1191
1192     if (ret < 0) {
1193         reply.error = -ret;
1194         goto error_reply;
1195     }
1196
1197     if (client->closing) {
1198         /*
1199          * The client may be closed when we are blocked in
1200          * nbd_co_receive_request()
1201          */
1202         goto done;
1203     }
1204
1205     switch (request.type) {
1206     case NBD_CMD_READ:
1207         TRACE("Request type is READ");
1208
1209         /* XXX: NBD Protocol only documents use of FUA with WRITE */
1210         if (request.flags & NBD_CMD_FLAG_FUA) {
1211             ret = blk_co_flush(exp->blk);
1212             if (ret < 0) {
1213                 LOG("flush failed");
1214                 reply.error = -ret;
1215                 goto error_reply;
1216             }
1217         }
1218
1219         ret = blk_pread(exp->blk, request.from + exp->dev_offset,
1220                         req->data, request.len);
1221         if (ret < 0) {
1222             LOG("reading from file failed");
1223             reply.error = -ret;
1224             goto error_reply;
1225         }
1226
1227         TRACE("Read %" PRIu32" byte(s)", request.len);
1228         if (nbd_co_send_reply(req, &reply, request.len) < 0)
1229             goto out;
1230         break;
1231     case NBD_CMD_WRITE:
1232         TRACE("Request type is WRITE");
1233
1234         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
1235             TRACE("Server is read-only, return error");
1236             reply.error = EROFS;
1237             goto error_reply;
1238         }
1239
1240         TRACE("Writing to device");
1241
1242         flags = 0;
1243         if (request.flags & NBD_CMD_FLAG_FUA) {
1244             flags |= BDRV_REQ_FUA;
1245         }
1246         ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
1247                          req->data, request.len, flags);
1248         if (ret < 0) {
1249             LOG("writing to file failed");
1250             reply.error = -ret;
1251             goto error_reply;
1252         }
1253
1254         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1255             goto out;
1256         }
1257         break;
1258
1259     case NBD_CMD_WRITE_ZEROES:
1260         TRACE("Request type is WRITE_ZEROES");
1261
1262         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
1263             TRACE("Server is read-only, return error");
1264             reply.error = EROFS;
1265             goto error_reply;
1266         }
1267
1268         TRACE("Writing to device");
1269
1270         flags = 0;
1271         if (request.flags & NBD_CMD_FLAG_FUA) {
1272             flags |= BDRV_REQ_FUA;
1273         }
1274         if (!(request.flags & NBD_CMD_FLAG_NO_HOLE)) {
1275             flags |= BDRV_REQ_MAY_UNMAP;
1276         }
1277         ret = blk_pwrite_zeroes(exp->blk, request.from + exp->dev_offset,
1278                                 request.len, flags);
1279         if (ret < 0) {
1280             LOG("writing to file failed");
1281             reply.error = -ret;
1282             goto error_reply;
1283         }
1284
1285         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1286             goto out;
1287         }
1288         break;
1289
1290     case NBD_CMD_DISC:
1291         /* unreachable, thanks to special case in nbd_co_receive_request() */
1292         abort();
1293
1294     case NBD_CMD_FLUSH:
1295         TRACE("Request type is FLUSH");
1296
1297         ret = blk_co_flush(exp->blk);
1298         if (ret < 0) {
1299             LOG("flush failed");
1300             reply.error = -ret;
1301         }
1302         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1303             goto out;
1304         }
1305         break;
1306     case NBD_CMD_TRIM:
1307         TRACE("Request type is TRIM");
1308         ret = blk_co_pdiscard(exp->blk, request.from + exp->dev_offset,
1309                               request.len);
1310         if (ret < 0) {
1311             LOG("discard failed");
1312             reply.error = -ret;
1313         }
1314         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1315             goto out;
1316         }
1317         break;
1318     default:
1319         LOG("invalid request type (%" PRIu32 ") received", request.type);
1320         reply.error = EINVAL;
1321     error_reply:
1322         /* We must disconnect after NBD_CMD_WRITE if we did not
1323          * read the payload.
1324          */
1325         if (nbd_co_send_reply(req, &reply, 0) < 0 || !req->complete) {
1326             goto out;
1327         }
1328         break;
1329     }
1330
1331     TRACE("Request/Reply complete");
1332
1333 done:
1334     nbd_request_put(req);
1335     nbd_client_put(client);
1336     return;
1337
1338 out:
1339     nbd_request_put(req);
1340     client_close(client);
1341     nbd_client_put(client);
1342 }
1343
1344 static void nbd_client_receive_next_request(NBDClient *client)
1345 {
1346     if (!client->recv_coroutine && client->nb_requests < MAX_NBD_REQUESTS) {
1347         nbd_client_get(client);
1348         client->recv_coroutine = qemu_coroutine_create(nbd_trip, client);
1349         aio_co_schedule(client->exp->ctx, client->recv_coroutine);
1350     }
1351 }
1352
1353 static coroutine_fn void nbd_co_client_start(void *opaque)
1354 {
1355     NBDClientNewData *data = opaque;
1356     NBDClient *client = data->client;
1357     NBDExport *exp = client->exp;
1358
1359     if (exp) {
1360         nbd_export_get(exp);
1361         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
1362     }
1363     qemu_co_mutex_init(&client->send_lock);
1364
1365     if (nbd_negotiate(data)) {
1366         client_close(client);
1367         goto out;
1368     }
1369
1370     nbd_client_receive_next_request(client);
1371
1372 out:
1373     g_free(data);
1374 }
1375
1376 void nbd_client_new(NBDExport *exp,
1377                     QIOChannelSocket *sioc,
1378                     QCryptoTLSCreds *tlscreds,
1379                     const char *tlsaclname,
1380                     void (*close_fn)(NBDClient *))
1381 {
1382     NBDClient *client;
1383     NBDClientNewData *data = g_new(NBDClientNewData, 1);
1384
1385     client = g_malloc0(sizeof(NBDClient));
1386     client->refcount = 1;
1387     client->exp = exp;
1388     client->tlscreds = tlscreds;
1389     if (tlscreds) {
1390         object_ref(OBJECT(client->tlscreds));
1391     }
1392     client->tlsaclname = g_strdup(tlsaclname);
1393     client->sioc = sioc;
1394     object_ref(OBJECT(client->sioc));
1395     client->ioc = QIO_CHANNEL(sioc);
1396     object_ref(OBJECT(client->ioc));
1397     client->close = close_fn;
1398
1399     data->client = client;
1400     data->co = qemu_coroutine_create(nbd_co_client_start, data);
1401     qemu_coroutine_enter(data->co);
1402 }