nbd/server.c

   1 /*
   2  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   3  *
   4  *  Network Block Device Server Side
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; under version 2 of the License.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "qemu/osdep.h"
  20 #include "nbd-internal.h"
  21
  22 static int system_errno_to_nbd_errno(int err)
  23 {
  24     switch (err) {
  25     case 0:
  26         return NBD_SUCCESS;
  27     case EPERM:
  28         return NBD_EPERM;
  29     case EIO:
  30         return NBD_EIO;
  31     case ENOMEM:
  32         return NBD_ENOMEM;
  33 #ifdef EDQUOT
  34     case EDQUOT:
  35 #endif
  36     case EFBIG:
  37     case ENOSPC:
  38         return NBD_ENOSPC;
  39     case EINVAL:
  40     default:
  41         return NBD_EINVAL;
  42     }
  43 }
  44
  45 /* Definitions for opaque data types */
  46
  47 typedef struct NBDRequest NBDRequest;
  48
  49 struct NBDRequest {
  50     QSIMPLEQ_ENTRY(NBDRequest) entry;
  51     NBDClient *client;
  52     uint8_t *data;
  53 };
  54
  55 struct NBDExport {
  56     int refcount;
  57     void (*close)(NBDExport *exp);
  58
  59     BlockBackend *blk;
  60     char *name;
  61     off_t dev_offset;
  62     off_t size;
  63     uint32_t nbdflags;
  64     QTAILQ_HEAD(, NBDClient) clients;
  65     QTAILQ_ENTRY(NBDExport) next;
  66
  67     AioContext *ctx;
  68
  69     Notifier eject_notifier;
  70 };
  71
  72 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  73
  74 struct NBDClient {
  75     int refcount;
  76     void (*close)(NBDClient *client);
  77
  78     NBDExport *exp;
  79     QIOChannelSocket *sioc; /* The underlying data channel */
  80     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
  81
  82     Coroutine *recv_coroutine;
  83
  84     CoMutex send_lock;
  85     Coroutine *send_coroutine;
  86
  87     bool can_read;
  88
  89     QTAILQ_ENTRY(NBDClient) next;
  90     int nb_requests;
  91     bool closing;
  92 };
  93
  94 /* That's all folks */
  95
  96 static void nbd_set_handlers(NBDClient *client);
  97 static void nbd_unset_handlers(NBDClient *client);
  98 static void nbd_update_can_read(NBDClient *client);
  99
 100 static gboolean nbd_negotiate_continue(QIOChannel *ioc,
 101                                        GIOCondition condition,
 102                                        void *opaque)
 103 {
 104     qemu_coroutine_enter(opaque, NULL);
 105     return TRUE;
 106 }
 107
 108 static ssize_t nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
 109 {
 110     ssize_t ret;
 111     guint watch;
 112
 113     assert(qemu_in_coroutine());
 114     /* Negotiation are always in main loop. */
 115     watch = qio_channel_add_watch(ioc,
 116                                   G_IO_IN,
 117                                   nbd_negotiate_continue,
 118                                   qemu_coroutine_self(),
 119                                   NULL);
 120     ret = read_sync(ioc, buffer, size);
 121     g_source_remove(watch);
 122     return ret;
 123
 124 }
 125
 126 static ssize_t nbd_negotiate_write(QIOChannel *ioc, void *buffer, size_t size)
 127 {
 128     ssize_t ret;
 129     guint watch;
 130
 131     assert(qemu_in_coroutine());
 132     /* Negotiation are always in main loop. */
 133     watch = qio_channel_add_watch(ioc,
 134                                   G_IO_OUT,
 135                                   nbd_negotiate_continue,
 136                                   qemu_coroutine_self(),
 137                                   NULL);
 138     ret = write_sync(ioc, buffer, size);
 139     g_source_remove(watch);
 140     return ret;
 141 }
 142
 143 static ssize_t nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)
 144 {
 145     ssize_t ret, dropped = size;
 146     uint8_t *buffer = g_malloc(MIN(65536, size));
 147
 148     while (size > 0) {
 149         ret = nbd_negotiate_read(ioc, buffer, MIN(65536, size));
 150         if (ret < 0) {
 151             g_free(buffer);
 152             return ret;
 153         }
 154
 155         assert(ret <= size);
 156         size -= ret;
 157     }
 158
 159     g_free(buffer);
 160     return dropped;
 161 }
 162
 163 /* Basic flow for negotiation
 164
 165    Server         Client
 166    Negotiate
 167
 168    or
 169
 170    Server         Client
 171    Negotiate #1
 172                   Option
 173    Negotiate #2
 174
 175    ----
 176
 177    followed by
 178
 179    Server         Client
 180                   Request
 181    Response
 182                   Request
 183    Response
 184                   ...
 185    ...
 186                   Request (type == 2)
 187
 188 */
 189
 190 static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
 191 {
 192     uint64_t magic;
 193     uint32_t len;
 194
 195     magic = cpu_to_be64(NBD_REP_MAGIC);
 196     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 197         LOG("write failed (rep magic)");
 198         return -EINVAL;
 199     }
 200     opt = cpu_to_be32(opt);
 201     if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 202         LOG("write failed (rep opt)");
 203         return -EINVAL;
 204     }
 205     type = cpu_to_be32(type);
 206     if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
 207         LOG("write failed (rep type)");
 208         return -EINVAL;
 209     }
 210     len = cpu_to_be32(0);
 211     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 212         LOG("write failed (rep data length)");
 213         return -EINVAL;
 214     }
 215     return 0;
 216 }
 217
 218 static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
 219 {
 220     uint64_t magic, name_len;
 221     uint32_t opt, type, len;
 222
 223     TRACE("Advertizing export name '%s'", exp->name ? exp->name : "");
 224     name_len = strlen(exp->name);
 225     magic = cpu_to_be64(NBD_REP_MAGIC);
 226     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 227         LOG("write failed (magic)");
 228         return -EINVAL;
 229      }
 230     opt = cpu_to_be32(NBD_OPT_LIST);
 231     if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 232         LOG("write failed (opt)");
 233         return -EINVAL;
 234     }
 235     type = cpu_to_be32(NBD_REP_SERVER);
 236     if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
 237         LOG("write failed (reply type)");
 238         return -EINVAL;
 239     }
 240     len = cpu_to_be32(name_len + sizeof(len));
 241     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 242         LOG("write failed (length)");
 243         return -EINVAL;
 244     }
 245     len = cpu_to_be32(name_len);
 246     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 247         LOG("write failed (length)");
 248         return -EINVAL;
 249     }
 250     if (nbd_negotiate_write(ioc, exp->name, name_len) != name_len) {
 251         LOG("write failed (buffer)");
 252         return -EINVAL;
 253     }
 254     return 0;
 255 }
 256
 257 static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
 258 {
 259     NBDExport *exp;
 260
 261     if (length) {
 262         if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
 263             return -EIO;
 264         }
 265         return nbd_negotiate_send_rep(client->ioc,
 266                                       NBD_REP_ERR_INVALID, NBD_OPT_LIST);
 267     }
 268
 269     /* For each export, send a NBD_REP_SERVER reply. */
 270     QTAILQ_FOREACH(exp, &exports, next) {
 271         if (nbd_negotiate_send_rep_list(client->ioc, exp)) {
 272             return -EINVAL;
 273         }
 274     }
 275     /* Finish with a NBD_REP_ACK. */
 276     return nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, NBD_OPT_LIST);
 277 }
 278
 279 static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
 280 {
 281     int rc = -EINVAL;
 282     char name[256];
 283
 284     /* Client sends:
 285         [20 ..  xx]   export name (length bytes)
 286      */
 287     TRACE("Checking length");
 288     if (length > 255) {
 289         LOG("Bad length received");
 290         goto fail;
 291     }
 292     if (nbd_negotiate_read(client->ioc, name, length) != length) {
 293         LOG("read failed");
 294         goto fail;
 295     }
 296     name[length] = '\0';
 297
 298     TRACE("Client requested export '%s'", name);
 299
 300     client->exp = nbd_export_find(name);
 301     if (!client->exp) {
 302         LOG("export not found");
 303         goto fail;
 304     }
 305
 306     QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
 307     nbd_export_get(client->exp);
 308     rc = 0;
 309 fail:
 310     return rc;
 311 }
 312
 313 static int nbd_negotiate_options(NBDClient *client)
 314 {
 315     uint32_t flags;
 316     bool fixedNewstyle = false;
 317
 318     /* Client sends:
 319         [ 0 ..   3]   client flags
 320
 321         [ 0 ..   7]   NBD_OPTS_MAGIC
 322         [ 8 ..  11]   NBD option
 323         [12 ..  15]   Data length
 324         ...           Rest of request
 325
 326         [ 0 ..   7]   NBD_OPTS_MAGIC
 327         [ 8 ..  11]   Second NBD option
 328         [12 ..  15]   Data length
 329         ...           Rest of request
 330     */
 331
 332     if (nbd_negotiate_read(client->ioc, &flags, sizeof(flags)) !=
 333         sizeof(flags)) {
 334         LOG("read failed");
 335         return -EIO;
 336     }
 337     TRACE("Checking client flags");
 338     be32_to_cpus(&flags);
 339     if (flags & NBD_FLAG_C_FIXED_NEWSTYLE) {
 340         TRACE("Support supports fixed newstyle handshake");
 341         fixedNewstyle = true;
 342         flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE;
 343     }
 344     if (flags != 0) {
 345         TRACE("Unknown client flags 0x%x received", flags);
 346         return -EIO;
 347     }
 348
 349     while (1) {
 350         int ret;
 351         uint32_t clientflags, length;
 352         uint64_t magic;
 353
 354         if (nbd_negotiate_read(client->ioc, &magic, sizeof(magic)) !=
 355             sizeof(magic)) {
 356             LOG("read failed");
 357             return -EINVAL;
 358         }
 359         TRACE("Checking opts magic");
 360         if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
 361             LOG("Bad magic received");
 362             return -EINVAL;
 363         }
 364
 365         if (nbd_negotiate_read(client->ioc, &clientflags,
 366                                sizeof(clientflags)) != sizeof(clientflags)) {
 367             LOG("read failed");
 368             return -EINVAL;
 369         }
 370         clientflags = be32_to_cpu(clientflags);
 371
 372         if (nbd_negotiate_read(client->ioc, &length, sizeof(length)) !=
 373             sizeof(length)) {
 374             LOG("read failed");
 375             return -EINVAL;
 376         }
 377         length = be32_to_cpu(length);
 378
 379         TRACE("Checking option 0x%x", clientflags);
 380         if (fixedNewstyle) {
 381             switch (clientflags) {
 382             case NBD_OPT_LIST:
 383                 ret = nbd_negotiate_handle_list(client, length);
 384                 if (ret < 0) {
 385                     return ret;
 386                 }
 387                 break;
 388
 389             case NBD_OPT_ABORT:
 390                 return -EINVAL;
 391
 392             case NBD_OPT_EXPORT_NAME:
 393                 return nbd_negotiate_handle_export_name(client, length);
 394
 395             default:
 396                 TRACE("Unsupported option 0x%x", clientflags);
 397                 nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_UNSUP,
 398                                        clientflags);
 399                 return -EINVAL;
 400             }
 401         } else {
 402             /*
 403              * If broken new-style we should drop the connection
 404              * for anything except NBD_OPT_EXPORT_NAME
 405              */
 406             switch (clientflags) {
 407             case NBD_OPT_EXPORT_NAME:
 408                 return nbd_negotiate_handle_export_name(client, length);
 409
 410             default:
 411                 TRACE("Unsupported option 0x%x", clientflags);
 412                 return -EINVAL;
 413             }
 414         }
 415     }
 416 }
 417
 418 typedef struct {
 419     NBDClient *client;
 420     Coroutine *co;
 421 } NBDClientNewData;
 422
 423 static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
 424 {
 425     NBDClient *client = data->client;
 426     char buf[8 + 8 + 8 + 128];
 427     int rc;
 428     const int myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
 429                          NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
 430
 431     /* Negotiation header without options:
 432         [ 0 ..   7]   passwd       ("NBDMAGIC")
 433         [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
 434         [16 ..  23]   size
 435         [24 ..  25]   server flags (0)
 436         [26 ..  27]   export flags
 437         [28 .. 151]   reserved     (0)
 438
 439        Negotiation header with options, part 1:
 440         [ 0 ..   7]   passwd       ("NBDMAGIC")
 441         [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
 442         [16 ..  17]   server flags (0)
 443
 444        part 2 (after options are sent):
 445         [18 ..  25]   size
 446         [26 ..  27]   export flags
 447         [28 .. 151]   reserved     (0)
 448      */
 449
 450     qio_channel_set_blocking(client->ioc, false, NULL);
 451     rc = -EINVAL;
 452
 453     TRACE("Beginning negotiation.");
 454     memset(buf, 0, sizeof(buf));
 455     memcpy(buf, "NBDMAGIC", 8);
 456     if (client->exp) {
 457         assert ((client->exp->nbdflags & ~65535) == 0);
 458         stq_be_p(buf + 8, NBD_CLIENT_MAGIC);
 459         stq_be_p(buf + 16, client->exp->size);
 460         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 461     } else {
 462         stq_be_p(buf + 8, NBD_OPTS_MAGIC);
 463         stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE);
 464     }
 465
 466     if (client->exp) {
 467         if (nbd_negotiate_write(client->ioc, buf, sizeof(buf)) != sizeof(buf)) {
 468             LOG("write failed");
 469             goto fail;
 470         }
 471     } else {
 472         if (nbd_negotiate_write(client->ioc, buf, 18) != 18) {
 473             LOG("write failed");
 474             goto fail;
 475         }
 476         rc = nbd_negotiate_options(client);
 477         if (rc != 0) {
 478             LOG("option negotiation failed");
 479             goto fail;
 480         }
 481
 482         assert ((client->exp->nbdflags & ~65535) == 0);
 483         stq_be_p(buf + 18, client->exp->size);
 484         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 485         if (nbd_negotiate_write(client->ioc, buf + 18, sizeof(buf) - 18) !=
 486             sizeof(buf) - 18) {
 487             LOG("write failed");
 488             goto fail;
 489         }
 490     }
 491
 492     TRACE("Negotiation succeeded.");
 493     rc = 0;
 494 fail:
 495     return rc;
 496 }
 497
 498 #ifdef __linux__
 499
 500 int nbd_disconnect(int fd)
 501 {
 502     ioctl(fd, NBD_CLEAR_QUE);
 503     ioctl(fd, NBD_DISCONNECT);
 504     ioctl(fd, NBD_CLEAR_SOCK);
 505     return 0;
 506 }
 507
 508 #else
 509
 510 int nbd_disconnect(int fd)
 511 {
 512     return -ENOTSUP;
 513 }
 514 #endif
 515
 516 static ssize_t nbd_receive_request(QIOChannel *ioc, struct nbd_request *request)
 517 {
 518     uint8_t buf[NBD_REQUEST_SIZE];
 519     uint32_t magic;
 520     ssize_t ret;
 521
 522     ret = read_sync(ioc, buf, sizeof(buf));
 523     if (ret < 0) {
 524         return ret;
 525     }
 526
 527     if (ret != sizeof(buf)) {
 528         LOG("read failed");
 529         return -EINVAL;
 530     }
 531
 532     /* Request
 533        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
 534        [ 4 ..  7]   type    (0 == READ, 1 == WRITE)
 535        [ 8 .. 15]   handle
 536        [16 .. 23]   from
 537        [24 .. 27]   len
 538      */
 539
 540     magic = be32_to_cpup((uint32_t*)buf);
 541     request->type  = be32_to_cpup((uint32_t*)(buf + 4));
 542     request->handle = be64_to_cpup((uint64_t*)(buf + 8));
 543     request->from  = be64_to_cpup((uint64_t*)(buf + 16));
 544     request->len   = be32_to_cpup((uint32_t*)(buf + 24));
 545
 546     TRACE("Got request: "
 547           "{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }",
 548           magic, request->type, request->from, request->len);
 549
 550     if (magic != NBD_REQUEST_MAGIC) {
 551         LOG("invalid magic (got 0x%x)", magic);
 552         return -EINVAL;
 553     }
 554     return 0;
 555 }
 556
 557 static ssize_t nbd_send_reply(QIOChannel *ioc, struct nbd_reply *reply)
 558 {
 559     uint8_t buf[NBD_REPLY_SIZE];
 560     ssize_t ret;
 561
 562     reply->error = system_errno_to_nbd_errno(reply->error);
 563
 564     /* Reply
 565        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 566        [ 4 ..  7]    error   (0 == no error)
 567        [ 7 .. 15]    handle
 568      */
 569     stl_be_p(buf, NBD_REPLY_MAGIC);
 570     stl_be_p(buf + 4, reply->error);
 571     stq_be_p(buf + 8, reply->handle);
 572
 573     TRACE("Sending response to client");
 574
 575     ret = write_sync(ioc, buf, sizeof(buf));
 576     if (ret < 0) {
 577         return ret;
 578     }
 579
 580     if (ret != sizeof(buf)) {
 581         LOG("writing to socket failed");
 582         return -EINVAL;
 583     }
 584     return 0;
 585 }
 586
 587 #define MAX_NBD_REQUESTS 16
 588
 589 void nbd_client_get(NBDClient *client)
 590 {
 591     client->refcount++;
 592 }
 593
 594 void nbd_client_put(NBDClient *client)
 595 {
 596     if (--client->refcount == 0) {
 597         /* The last reference should be dropped by client->close,
 598          * which is called by client_close.
 599          */
 600         assert(client->closing);
 601
 602         nbd_unset_handlers(client);
 603         object_unref(OBJECT(client->sioc));
 604         object_unref(OBJECT(client->ioc));
 605         if (client->exp) {
 606             QTAILQ_REMOVE(&client->exp->clients, client, next);
 607             nbd_export_put(client->exp);
 608         }
 609         g_free(client);
 610     }
 611 }
 612
 613 static void client_close(NBDClient *client)
 614 {
 615     if (client->closing) {
 616         return;
 617     }
 618
 619     client->closing = true;
 620
 621     /* Force requests to finish.  They will drop their own references,
 622      * then we'll close the socket and free the NBDClient.
 623      */
 624     qio_channel_shutdown(client->ioc, QIO_CHANNEL_SHUTDOWN_BOTH,
 625                          NULL);
 626
 627     /* Also tell the client, so that they release their reference.  */
 628     if (client->close) {
 629         client->close(client);
 630     }
 631 }
 632
 633 static NBDRequest *nbd_request_get(NBDClient *client)
 634 {
 635     NBDRequest *req;
 636
 637     assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
 638     client->nb_requests++;
 639     nbd_update_can_read(client);
 640
 641     req = g_new0(NBDRequest, 1);
 642     nbd_client_get(client);
 643     req->client = client;
 644     return req;
 645 }
 646
 647 static void nbd_request_put(NBDRequest *req)
 648 {
 649     NBDClient *client = req->client;
 650
 651     if (req->data) {
 652         qemu_vfree(req->data);
 653     }
 654     g_free(req);
 655
 656     client->nb_requests--;
 657     nbd_update_can_read(client);
 658     nbd_client_put(client);
 659 }
 660
 661 static void blk_aio_attached(AioContext *ctx, void *opaque)
 662 {
 663     NBDExport *exp = opaque;
 664     NBDClient *client;
 665
 666     TRACE("Export %s: Attaching clients to AIO context %p\n", exp->name, ctx);
 667
 668     exp->ctx = ctx;
 669
 670     QTAILQ_FOREACH(client, &exp->clients, next) {
 671         nbd_set_handlers(client);
 672     }
 673 }
 674
 675 static void blk_aio_detach(void *opaque)
 676 {
 677     NBDExport *exp = opaque;
 678     NBDClient *client;
 679
 680     TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
 681
 682     QTAILQ_FOREACH(client, &exp->clients, next) {
 683         nbd_unset_handlers(client);
 684     }
 685
 686     exp->ctx = NULL;
 687 }
 688
 689 static void nbd_eject_notifier(Notifier *n, void *data)
 690 {
 691     NBDExport *exp = container_of(n, NBDExport, eject_notifier);
 692     nbd_export_close(exp);
 693 }
 694
 695 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
 696                           uint32_t nbdflags, void (*close)(NBDExport *),
 697                           Error **errp)
 698 {
 699     NBDExport *exp = g_malloc0(sizeof(NBDExport));
 700     exp->refcount = 1;
 701     QTAILQ_INIT(&exp->clients);
 702     exp->blk = blk;
 703     exp->dev_offset = dev_offset;
 704     exp->nbdflags = nbdflags;
 705     exp->size = size < 0 ? blk_getlength(blk) : size;
 706     if (exp->size < 0) {
 707         error_setg_errno(errp, -exp->size,
 708                          "Failed to determine the NBD export's length");
 709         goto fail;
 710     }
 711     exp->size -= exp->size % BDRV_SECTOR_SIZE;
 712
 713     exp->close = close;
 714     exp->ctx = blk_get_aio_context(blk);
 715     blk_ref(blk);
 716     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 717
 718     exp->eject_notifier.notify = nbd_eject_notifier;
 719     blk_add_remove_bs_notifier(blk, &exp->eject_notifier);
 720
 721     /*
 722      * NBD exports are used for non-shared storage migration.  Make sure
 723      * that BDRV_O_INACTIVE is cleared and the image is ready for write
 724      * access since the export could be available before migration handover.
 725      */
 726     aio_context_acquire(exp->ctx);
 727     blk_invalidate_cache(blk, NULL);
 728     aio_context_release(exp->ctx);
 729     return exp;
 730
 731 fail:
 732     g_free(exp);
 733     return NULL;
 734 }
 735
 736 NBDExport *nbd_export_find(const char *name)
 737 {
 738     NBDExport *exp;
 739     QTAILQ_FOREACH(exp, &exports, next) {
 740         if (strcmp(name, exp->name) == 0) {
 741             return exp;
 742         }
 743     }
 744
 745     return NULL;
 746 }
 747
 748 void nbd_export_set_name(NBDExport *exp, const char *name)
 749 {
 750     if (exp->name == name) {
 751         return;
 752     }
 753
 754     nbd_export_get(exp);
 755     if (exp->name != NULL) {
 756         g_free(exp->name);
 757         exp->name = NULL;
 758         QTAILQ_REMOVE(&exports, exp, next);
 759         nbd_export_put(exp);
 760     }
 761     if (name != NULL) {
 762         nbd_export_get(exp);
 763         exp->name = g_strdup(name);
 764         QTAILQ_INSERT_TAIL(&exports, exp, next);
 765     }
 766     nbd_export_put(exp);
 767 }
 768
 769 void nbd_export_close(NBDExport *exp)
 770 {
 771     NBDClient *client, *next;
 772
 773     nbd_export_get(exp);
 774     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
 775         client_close(client);
 776     }
 777     nbd_export_set_name(exp, NULL);
 778     nbd_export_put(exp);
 779 }
 780
 781 void nbd_export_get(NBDExport *exp)
 782 {
 783     assert(exp->refcount > 0);
 784     exp->refcount++;
 785 }
 786
 787 void nbd_export_put(NBDExport *exp)
 788 {
 789     assert(exp->refcount > 0);
 790     if (exp->refcount == 1) {
 791         nbd_export_close(exp);
 792     }
 793
 794     if (--exp->refcount == 0) {
 795         assert(exp->name == NULL);
 796
 797         if (exp->close) {
 798             exp->close(exp);
 799         }
 800
 801         if (exp->blk) {
 802             notifier_remove(&exp->eject_notifier);
 803             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
 804                                             blk_aio_detach, exp);
 805             blk_unref(exp->blk);
 806             exp->blk = NULL;
 807         }
 808
 809         g_free(exp);
 810     }
 811 }
 812
 813 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 814 {
 815     return exp->blk;
 816 }
 817
 818 void nbd_export_close_all(void)
 819 {
 820     NBDExport *exp, *next;
 821
 822     QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
 823         nbd_export_close(exp);
 824     }
 825 }
 826
 827 static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
 828                                  int len)
 829 {
 830     NBDClient *client = req->client;
 831     ssize_t rc, ret;
 832
 833     g_assert(qemu_in_coroutine());
 834     qemu_co_mutex_lock(&client->send_lock);
 835     client->send_coroutine = qemu_coroutine_self();
 836     nbd_set_handlers(client);
 837
 838     if (!len) {
 839         rc = nbd_send_reply(client->ioc, reply);
 840     } else {
 841         qio_channel_set_cork(client->ioc, true);
 842         rc = nbd_send_reply(client->ioc, reply);
 843         if (rc >= 0) {
 844             ret = write_sync(client->ioc, req->data, len);
 845             if (ret != len) {
 846                 rc = -EIO;
 847             }
 848         }
 849         qio_channel_set_cork(client->ioc, false);
 850     }
 851
 852     client->send_coroutine = NULL;
 853     nbd_set_handlers(client);
 854     qemu_co_mutex_unlock(&client->send_lock);
 855     return rc;
 856 }
 857
 858 static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *request)
 859 {
 860     NBDClient *client = req->client;
 861     uint32_t command;
 862     ssize_t rc;
 863
 864     g_assert(qemu_in_coroutine());
 865     client->recv_coroutine = qemu_coroutine_self();
 866     nbd_update_can_read(client);
 867
 868     rc = nbd_receive_request(client->ioc, request);
 869     if (rc < 0) {
 870         if (rc != -EAGAIN) {
 871             rc = -EIO;
 872         }
 873         goto out;
 874     }
 875
 876     if ((request->from + request->len) < request->from) {
 877         LOG("integer overflow detected! "
 878             "you're probably being attacked");
 879         rc = -EINVAL;
 880         goto out;
 881     }
 882
 883     TRACE("Decoding type");
 884
 885     command = request->type & NBD_CMD_MASK_COMMAND;
 886     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
 887         if (request->len > NBD_MAX_BUFFER_SIZE) {
 888             LOG("len (%u) is larger than max len (%u)",
 889                 request->len, NBD_MAX_BUFFER_SIZE);
 890             rc = -EINVAL;
 891             goto out;
 892         }
 893
 894         req->data = blk_try_blockalign(client->exp->blk, request->len);
 895         if (req->data == NULL) {
 896             rc = -ENOMEM;
 897             goto out;
 898         }
 899     }
 900     if (command == NBD_CMD_WRITE) {
 901         TRACE("Reading %u byte(s)", request->len);
 902
 903         if (read_sync(client->ioc, req->data, request->len) != request->len) {
 904             LOG("reading from socket failed");
 905             rc = -EIO;
 906             goto out;
 907         }
 908     }
 909     rc = 0;
 910
 911 out:
 912     client->recv_coroutine = NULL;
 913     nbd_update_can_read(client);
 914
 915     return rc;
 916 }
 917
 918 static void nbd_trip(void *opaque)
 919 {
 920     NBDClient *client = opaque;
 921     NBDExport *exp = client->exp;
 922     NBDRequest *req;
 923     struct nbd_request request;
 924     struct nbd_reply reply;
 925     ssize_t ret;
 926     uint32_t command;
 927
 928     TRACE("Reading request.");
 929     if (client->closing) {
 930         return;
 931     }
 932
 933     req = nbd_request_get(client);
 934     ret = nbd_co_receive_request(req, &request);
 935     if (ret == -EAGAIN) {
 936         goto done;
 937     }
 938     if (ret == -EIO) {
 939         goto out;
 940     }
 941
 942     reply.handle = request.handle;
 943     reply.error = 0;
 944
 945     if (ret < 0) {
 946         reply.error = -ret;
 947         goto error_reply;
 948     }
 949     command = request.type & NBD_CMD_MASK_COMMAND;
 950     if (command != NBD_CMD_DISC && (request.from + request.len) > exp->size) {
 951             LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
 952             ", Offset: %" PRIu64 "\n",
 953                     request.from, request.len,
 954                     (uint64_t)exp->size, (uint64_t)exp->dev_offset);
 955         LOG("requested operation past EOF--bad client?");
 956         goto invalid_request;
 957     }
 958
 959     if (client->closing) {
 960         /*
 961          * The client may be closed when we are blocked in
 962          * nbd_co_receive_request()
 963          */
 964         goto done;
 965     }
 966
 967     switch (command) {
 968     case NBD_CMD_READ:
 969         TRACE("Request type is READ");
 970
 971         if (request.type & NBD_CMD_FLAG_FUA) {
 972             ret = blk_co_flush(exp->blk);
 973             if (ret < 0) {
 974                 LOG("flush failed");
 975                 reply.error = -ret;
 976                 goto error_reply;
 977             }
 978         }
 979
 980         ret = blk_read(exp->blk,
 981                        (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
 982                        req->data, request.len / BDRV_SECTOR_SIZE);
 983         if (ret < 0) {
 984             LOG("reading from file failed");
 985             reply.error = -ret;
 986             goto error_reply;
 987         }
 988
 989         TRACE("Read %u byte(s)", request.len);
 990         if (nbd_co_send_reply(req, &reply, request.len) < 0)
 991             goto out;
 992         break;
 993     case NBD_CMD_WRITE:
 994         TRACE("Request type is WRITE");
 995
 996         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
 997             TRACE("Server is read-only, return error");
 998             reply.error = EROFS;
 999             goto error_reply;
1000         }
1001
1002         TRACE("Writing to device");
1003
1004         ret = blk_write(exp->blk,
1005                         (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
1006                         req->data, request.len / BDRV_SECTOR_SIZE);
1007         if (ret < 0) {
1008             LOG("writing to file failed");
1009             reply.error = -ret;
1010             goto error_reply;
1011         }
1012
1013         if (request.type & NBD_CMD_FLAG_FUA) {
1014             ret = blk_co_flush(exp->blk);
1015             if (ret < 0) {
1016                 LOG("flush failed");
1017                 reply.error = -ret;
1018                 goto error_reply;
1019             }
1020         }
1021
1022         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1023             goto out;
1024         }
1025         break;
1026     case NBD_CMD_DISC:
1027         TRACE("Request type is DISCONNECT");
1028         errno = 0;
1029         goto out;
1030     case NBD_CMD_FLUSH:
1031         TRACE("Request type is FLUSH");
1032
1033         ret = blk_co_flush(exp->blk);
1034         if (ret < 0) {
1035             LOG("flush failed");
1036             reply.error = -ret;
1037         }
1038         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1039             goto out;
1040         }
1041         break;
1042     case NBD_CMD_TRIM:
1043         TRACE("Request type is TRIM");
1044         ret = blk_co_discard(exp->blk, (request.from + exp->dev_offset)
1045                                        / BDRV_SECTOR_SIZE,
1046                              request.len / BDRV_SECTOR_SIZE);
1047         if (ret < 0) {
1048             LOG("discard failed");
1049             reply.error = -ret;
1050         }
1051         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1052             goto out;
1053         }
1054         break;
1055     default:
1056         LOG("invalid request type (%u) received", request.type);
1057     invalid_request:
1058         reply.error = EINVAL;
1059     error_reply:
1060         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1061             goto out;
1062         }
1063         break;
1064     }
1065
1066     TRACE("Request/Reply complete");
1067
1068 done:
1069     nbd_request_put(req);
1070     return;
1071
1072 out:
1073     nbd_request_put(req);
1074     client_close(client);
1075 }
1076
1077 static void nbd_read(void *opaque)
1078 {
1079     NBDClient *client = opaque;
1080
1081     if (client->recv_coroutine) {
1082         qemu_coroutine_enter(client->recv_coroutine, NULL);
1083     } else {
1084         qemu_coroutine_enter(qemu_coroutine_create(nbd_trip), client);
1085     }
1086 }
1087
1088 static void nbd_restart_write(void *opaque)
1089 {
1090     NBDClient *client = opaque;
1091
1092     qemu_coroutine_enter(client->send_coroutine, NULL);
1093 }
1094
1095 static void nbd_set_handlers(NBDClient *client)
1096 {
1097     if (client->exp && client->exp->ctx) {
1098         aio_set_fd_handler(client->exp->ctx, client->sioc->fd,
1099                            true,
1100                            client->can_read ? nbd_read : NULL,
1101                            client->send_coroutine ? nbd_restart_write : NULL,
1102                            client);
1103     }
1104 }
1105
1106 static void nbd_unset_handlers(NBDClient *client)
1107 {
1108     if (client->exp && client->exp->ctx) {
1109         aio_set_fd_handler(client->exp->ctx, client->sioc->fd,
1110                            true, NULL, NULL, NULL);
1111     }
1112 }
1113
1114 static void nbd_update_can_read(NBDClient *client)
1115 {
1116     bool can_read = client->recv_coroutine ||
1117                     client->nb_requests < MAX_NBD_REQUESTS;
1118
1119     if (can_read != client->can_read) {
1120         client->can_read = can_read;
1121         nbd_set_handlers(client);
1122
1123         /* There is no need to invoke aio_notify(), since aio_set_fd_handler()
1124          * in nbd_set_handlers() will have taken care of that */
1125     }
1126 }
1127
1128 static coroutine_fn void nbd_co_client_start(void *opaque)
1129 {
1130     NBDClientNewData *data = opaque;
1131     NBDClient *client = data->client;
1132     NBDExport *exp = client->exp;
1133
1134     if (exp) {
1135         nbd_export_get(exp);
1136     }
1137     if (nbd_negotiate(data)) {
1138         client_close(client);
1139         goto out;
1140     }
1141     qemu_co_mutex_init(&client->send_lock);
1142     nbd_set_handlers(client);
1143
1144     if (exp) {
1145         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
1146     }
1147 out:
1148     g_free(data);
1149 }
1150
1151 void nbd_client_new(NBDExport *exp,
1152                     QIOChannelSocket *sioc,
1153                     void (*close_fn)(NBDClient *))
1154 {
1155     NBDClient *client;
1156     NBDClientNewData *data = g_new(NBDClientNewData, 1);
1157
1158     client = g_malloc0(sizeof(NBDClient));
1159     client->refcount = 1;
1160     client->exp = exp;
1161     client->sioc = sioc;
1162     object_ref(OBJECT(client->sioc));
1163     client->ioc = QIO_CHANNEL(sioc);
1164     object_ref(OBJECT(client->ioc));
1165     client->can_read = true;
1166     client->close = close_fn;
1167
1168     data->client = client;
1169     data->co = qemu_coroutine_create(nbd_co_client_start);
1170     qemu_coroutine_enter(data->co, data);
1171 }