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