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 "nbd-internal.h"
  20
  21 static int system_errno_to_nbd_errno(int err)
  22 {
  23     switch (err) {
  24     case 0:
  25         return NBD_SUCCESS;
  26     case EPERM:
  27         return NBD_EPERM;
  28     case EIO:
  29         return NBD_EIO;
  30     case ENOMEM:
  31         return NBD_ENOMEM;
  32 #ifdef EDQUOT
  33     case EDQUOT:
  34 #endif
  35     case EFBIG:
  36     case ENOSPC:
  37         return NBD_ENOSPC;
  38     case EINVAL:
  39     default:
  40         return NBD_EINVAL;
  41     }
  42 }
  43
  44 /* Definitions for opaque data types */
  45
  46 typedef struct NBDRequest NBDRequest;
  47
  48 struct NBDRequest {
  49     QSIMPLEQ_ENTRY(NBDRequest) entry;
  50     NBDClient *client;
  51     uint8_t *data;
  52 };
  53
  54 struct NBDExport {
  55     int refcount;
  56     void (*close)(NBDExport *exp);
  57
  58     BlockBackend *blk;
  59     char *name;
  60     off_t dev_offset;
  61     off_t size;
  62     uint32_t nbdflags;
  63     QTAILQ_HEAD(, NBDClient) clients;
  64     QTAILQ_ENTRY(NBDExport) next;
  65
  66     AioContext *ctx;
  67 };
  68
  69 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  70
  71 struct NBDClient {
  72     int refcount;
  73     void (*close)(NBDClient *client);
  74
  75     NBDExport *exp;
  76     int sock;
  77
  78     Coroutine *recv_coroutine;
  79
  80     CoMutex send_lock;
  81     Coroutine *send_coroutine;
  82
  83     bool can_read;
  84
  85     QTAILQ_ENTRY(NBDClient) next;
  86     int nb_requests;
  87     bool closing;
  88 };
  89
  90 /* That's all folks */
  91
  92 static void nbd_set_handlers(NBDClient *client);
  93 static void nbd_unset_handlers(NBDClient *client);
  94 static void nbd_update_can_read(NBDClient *client);
  95
  96 static void nbd_negotiate_continue(void *opaque)
  97 {
  98     qemu_coroutine_enter(opaque, NULL);
  99 }
 100
 101 static ssize_t nbd_negotiate_read(int fd, void *buffer, size_t size)
 102 {
 103     ssize_t ret;
 104
 105     assert(qemu_in_coroutine());
 106     /* Negotiation are always in main loop. */
 107     qemu_set_fd_handler(fd, nbd_negotiate_continue, NULL,
 108                         qemu_coroutine_self());
 109     ret = read_sync(fd, buffer, size);
 110     qemu_set_fd_handler(fd, NULL, NULL, NULL);
 111     return ret;
 112
 113 }
 114
 115 static ssize_t nbd_negotiate_write(int fd, void *buffer, size_t size)
 116 {
 117     ssize_t ret;
 118
 119     assert(qemu_in_coroutine());
 120     /* Negotiation are always in main loop. */
 121     qemu_set_fd_handler(fd, NULL, nbd_negotiate_continue,
 122                         qemu_coroutine_self());
 123     ret = write_sync(fd, buffer, size);
 124     qemu_set_fd_handler(fd, NULL, NULL, NULL);
 125     return ret;
 126 }
 127
 128 static ssize_t nbd_negotiate_drop_sync(int fd, size_t size)
 129 {
 130     ssize_t ret, dropped = size;
 131     uint8_t *buffer = g_malloc(MIN(65536, size));
 132
 133     while (size > 0) {
 134         ret = nbd_negotiate_read(fd, buffer, MIN(65536, size));
 135         if (ret < 0) {
 136             g_free(buffer);
 137             return ret;
 138         }
 139
 140         assert(ret <= size);
 141         size -= ret;
 142     }
 143
 144     g_free(buffer);
 145     return dropped;
 146 }
 147
 148 /* Basic flow for negotiation
 149
 150    Server         Client
 151    Negotiate
 152
 153    or
 154
 155    Server         Client
 156    Negotiate #1
 157                   Option
 158    Negotiate #2
 159
 160    ----
 161
 162    followed by
 163
 164    Server         Client
 165                   Request
 166    Response
 167                   Request
 168    Response
 169                   ...
 170    ...
 171                   Request (type == 2)
 172
 173 */
 174
 175 static int nbd_negotiate_send_rep(int csock, uint32_t type, uint32_t opt)
 176 {
 177     uint64_t magic;
 178     uint32_t len;
 179
 180     magic = cpu_to_be64(NBD_REP_MAGIC);
 181     if (nbd_negotiate_write(csock, &magic, sizeof(magic)) != sizeof(magic)) {
 182         LOG("write failed (rep magic)");
 183         return -EINVAL;
 184     }
 185     opt = cpu_to_be32(opt);
 186     if (nbd_negotiate_write(csock, &opt, sizeof(opt)) != sizeof(opt)) {
 187         LOG("write failed (rep opt)");
 188         return -EINVAL;
 189     }
 190     type = cpu_to_be32(type);
 191     if (nbd_negotiate_write(csock, &type, sizeof(type)) != sizeof(type)) {
 192         LOG("write failed (rep type)");
 193         return -EINVAL;
 194     }
 195     len = cpu_to_be32(0);
 196     if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
 197         LOG("write failed (rep data length)");
 198         return -EINVAL;
 199     }
 200     return 0;
 201 }
 202
 203 static int nbd_negotiate_send_rep_list(int csock, NBDExport *exp)
 204 {
 205     uint64_t magic, name_len;
 206     uint32_t opt, type, len;
 207
 208     name_len = strlen(exp->name);
 209     magic = cpu_to_be64(NBD_REP_MAGIC);
 210     if (nbd_negotiate_write(csock, &magic, sizeof(magic)) != sizeof(magic)) {
 211         LOG("write failed (magic)");
 212         return -EINVAL;
 213      }
 214     opt = cpu_to_be32(NBD_OPT_LIST);
 215     if (nbd_negotiate_write(csock, &opt, sizeof(opt)) != sizeof(opt)) {
 216         LOG("write failed (opt)");
 217         return -EINVAL;
 218     }
 219     type = cpu_to_be32(NBD_REP_SERVER);
 220     if (nbd_negotiate_write(csock, &type, sizeof(type)) != sizeof(type)) {
 221         LOG("write failed (reply type)");
 222         return -EINVAL;
 223     }
 224     len = cpu_to_be32(name_len + sizeof(len));
 225     if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
 226         LOG("write failed (length)");
 227         return -EINVAL;
 228     }
 229     len = cpu_to_be32(name_len);
 230     if (nbd_negotiate_write(csock, &len, sizeof(len)) != sizeof(len)) {
 231         LOG("write failed (length)");
 232         return -EINVAL;
 233     }
 234     if (nbd_negotiate_write(csock, exp->name, name_len) != name_len) {
 235         LOG("write failed (buffer)");
 236         return -EINVAL;
 237     }
 238     return 0;
 239 }
 240
 241 static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
 242 {
 243     int csock;
 244     NBDExport *exp;
 245
 246     csock = client->sock;
 247     if (length) {
 248         if (nbd_negotiate_drop_sync(csock, length) != length) {
 249             return -EIO;
 250         }
 251         return nbd_negotiate_send_rep(csock, NBD_REP_ERR_INVALID, NBD_OPT_LIST);
 252     }
 253
 254     /* For each export, send a NBD_REP_SERVER reply. */
 255     QTAILQ_FOREACH(exp, &exports, next) {
 256         if (nbd_negotiate_send_rep_list(csock, exp)) {
 257             return -EINVAL;
 258         }
 259     }
 260     /* Finish with a NBD_REP_ACK. */
 261     return nbd_negotiate_send_rep(csock, NBD_REP_ACK, NBD_OPT_LIST);
 262 }
 263
 264 static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
 265 {
 266     int rc = -EINVAL, csock = client->sock;
 267     char name[256];
 268
 269     /* Client sends:
 270         [20 ..  xx]   export name (length bytes)
 271      */
 272     TRACE("Checking length");
 273     if (length > 255) {
 274         LOG("Bad length received");
 275         goto fail;
 276     }
 277     if (nbd_negotiate_read(csock, name, length) != length) {
 278         LOG("read failed");
 279         goto fail;
 280     }
 281     name[length] = '\0';
 282
 283     client->exp = nbd_export_find(name);
 284     if (!client->exp) {
 285         LOG("export not found");
 286         goto fail;
 287     }
 288
 289     QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
 290     nbd_export_get(client->exp);
 291     rc = 0;
 292 fail:
 293     return rc;
 294 }
 295
 296 static int nbd_negotiate_options(NBDClient *client)
 297 {
 298     int csock = client->sock;
 299     uint32_t flags;
 300
 301     /* Client sends:
 302         [ 0 ..   3]   client flags
 303
 304         [ 0 ..   7]   NBD_OPTS_MAGIC
 305         [ 8 ..  11]   NBD option
 306         [12 ..  15]   Data length
 307         ...           Rest of request
 308
 309         [ 0 ..   7]   NBD_OPTS_MAGIC
 310         [ 8 ..  11]   Second NBD option
 311         [12 ..  15]   Data length
 312         ...           Rest of request
 313     */
 314
 315     if (nbd_negotiate_read(csock, &flags, sizeof(flags)) != sizeof(flags)) {
 316         LOG("read failed");
 317         return -EIO;
 318     }
 319     TRACE("Checking client flags");
 320     be32_to_cpus(&flags);
 321     if (flags != 0 && flags != NBD_FLAG_C_FIXED_NEWSTYLE) {
 322         LOG("Bad client flags received");
 323         return -EIO;
 324     }
 325
 326     while (1) {
 327         int ret;
 328         uint32_t tmp, length;
 329         uint64_t magic;
 330
 331         if (nbd_negotiate_read(csock, &magic, sizeof(magic)) != sizeof(magic)) {
 332             LOG("read failed");
 333             return -EINVAL;
 334         }
 335         TRACE("Checking opts magic");
 336         if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
 337             LOG("Bad magic received");
 338             return -EINVAL;
 339         }
 340
 341         if (nbd_negotiate_read(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
 342             LOG("read failed");
 343             return -EINVAL;
 344         }
 345
 346         if (nbd_negotiate_read(csock, &length,
 347                                sizeof(length)) != sizeof(length)) {
 348             LOG("read failed");
 349             return -EINVAL;
 350         }
 351         length = be32_to_cpu(length);
 352
 353         TRACE("Checking option");
 354         switch (be32_to_cpu(tmp)) {
 355         case NBD_OPT_LIST:
 356             ret = nbd_negotiate_handle_list(client, length);
 357             if (ret < 0) {
 358                 return ret;
 359             }
 360             break;
 361
 362         case NBD_OPT_ABORT:
 363             return -EINVAL;
 364
 365         case NBD_OPT_EXPORT_NAME:
 366             return nbd_negotiate_handle_export_name(client, length);
 367
 368         default:
 369             tmp = be32_to_cpu(tmp);
 370             LOG("Unsupported option 0x%x", tmp);
 371             nbd_negotiate_send_rep(client->sock, NBD_REP_ERR_UNSUP, tmp);
 372             return -EINVAL;
 373         }
 374     }
 375 }
 376
 377 typedef struct {
 378     NBDClient *client;
 379     Coroutine *co;
 380 } NBDClientNewData;
 381
 382 static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
 383 {
 384     NBDClient *client = data->client;
 385     int csock = client->sock;
 386     char buf[8 + 8 + 8 + 128];
 387     int rc;
 388     const int myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
 389                          NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
 390
 391     /* Negotiation header without options:
 392         [ 0 ..   7]   passwd       ("NBDMAGIC")
 393         [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
 394         [16 ..  23]   size
 395         [24 ..  25]   server flags (0)
 396         [26 ..  27]   export flags
 397         [28 .. 151]   reserved     (0)
 398
 399        Negotiation header with options, part 1:
 400         [ 0 ..   7]   passwd       ("NBDMAGIC")
 401         [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
 402         [16 ..  17]   server flags (0)
 403
 404        part 2 (after options are sent):
 405         [18 ..  25]   size
 406         [26 ..  27]   export flags
 407         [28 .. 151]   reserved     (0)
 408      */
 409
 410     rc = -EINVAL;
 411
 412     TRACE("Beginning negotiation.");
 413     memset(buf, 0, sizeof(buf));
 414     memcpy(buf, "NBDMAGIC", 8);
 415     if (client->exp) {
 416         assert ((client->exp->nbdflags & ~65535) == 0);
 417         cpu_to_be64w((uint64_t*)(buf + 8), NBD_CLIENT_MAGIC);
 418         cpu_to_be64w((uint64_t*)(buf + 16), client->exp->size);
 419         cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
 420     } else {
 421         cpu_to_be64w((uint64_t*)(buf + 8), NBD_OPTS_MAGIC);
 422         cpu_to_be16w((uint16_t *)(buf + 16), NBD_FLAG_FIXED_NEWSTYLE);
 423     }
 424
 425     if (client->exp) {
 426         if (nbd_negotiate_write(csock, buf, sizeof(buf)) != sizeof(buf)) {
 427             LOG("write failed");
 428             goto fail;
 429         }
 430     } else {
 431         if (nbd_negotiate_write(csock, buf, 18) != 18) {
 432             LOG("write failed");
 433             goto fail;
 434         }
 435         rc = nbd_negotiate_options(client);
 436         if (rc != 0) {
 437             LOG("option negotiation failed");
 438             goto fail;
 439         }
 440
 441         assert ((client->exp->nbdflags & ~65535) == 0);
 442         cpu_to_be64w((uint64_t*)(buf + 18), client->exp->size);
 443         cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
 444         if (nbd_negotiate_write(csock, buf + 18,
 445                                 sizeof(buf) - 18) != sizeof(buf) - 18) {
 446             LOG("write failed");
 447             goto fail;
 448         }
 449     }
 450
 451     TRACE("Negotiation succeeded.");
 452     rc = 0;
 453 fail:
 454     return rc;
 455 }
 456
 457 #ifdef __linux__
 458
 459 int nbd_disconnect(int fd)
 460 {
 461     ioctl(fd, NBD_CLEAR_QUE);
 462     ioctl(fd, NBD_DISCONNECT);
 463     ioctl(fd, NBD_CLEAR_SOCK);
 464     return 0;
 465 }
 466
 467 #else
 468
 469 int nbd_disconnect(int fd)
 470 {
 471     return -ENOTSUP;
 472 }
 473 #endif
 474
 475 static ssize_t nbd_receive_request(int csock, struct nbd_request *request)
 476 {
 477     uint8_t buf[NBD_REQUEST_SIZE];
 478     uint32_t magic;
 479     ssize_t ret;
 480
 481     ret = read_sync(csock, buf, sizeof(buf));
 482     if (ret < 0) {
 483         return ret;
 484     }
 485
 486     if (ret != sizeof(buf)) {
 487         LOG("read failed");
 488         return -EINVAL;
 489     }
 490
 491     /* Request
 492        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
 493        [ 4 ..  7]   type    (0 == READ, 1 == WRITE)
 494        [ 8 .. 15]   handle
 495        [16 .. 23]   from
 496        [24 .. 27]   len
 497      */
 498
 499     magic = be32_to_cpup((uint32_t*)buf);
 500     request->type  = be32_to_cpup((uint32_t*)(buf + 4));
 501     request->handle = be64_to_cpup((uint64_t*)(buf + 8));
 502     request->from  = be64_to_cpup((uint64_t*)(buf + 16));
 503     request->len   = be32_to_cpup((uint32_t*)(buf + 24));
 504
 505     TRACE("Got request: "
 506           "{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }",
 507           magic, request->type, request->from, request->len);
 508
 509     if (magic != NBD_REQUEST_MAGIC) {
 510         LOG("invalid magic (got 0x%x)", magic);
 511         return -EINVAL;
 512     }
 513     return 0;
 514 }
 515
 516 static ssize_t nbd_send_reply(int csock, struct nbd_reply *reply)
 517 {
 518     uint8_t buf[NBD_REPLY_SIZE];
 519     ssize_t ret;
 520
 521     reply->error = system_errno_to_nbd_errno(reply->error);
 522
 523     /* Reply
 524        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 525        [ 4 ..  7]    error   (0 == no error)
 526        [ 7 .. 15]    handle
 527      */
 528     cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC);
 529     cpu_to_be32w((uint32_t*)(buf + 4), reply->error);
 530     cpu_to_be64w((uint64_t*)(buf + 8), reply->handle);
 531
 532     TRACE("Sending response to client");
 533
 534     ret = write_sync(csock, buf, sizeof(buf));
 535     if (ret < 0) {
 536         return ret;
 537     }
 538
 539     if (ret != sizeof(buf)) {
 540         LOG("writing to socket failed");
 541         return -EINVAL;
 542     }
 543     return 0;
 544 }
 545
 546 #define MAX_NBD_REQUESTS 16
 547
 548 void nbd_client_get(NBDClient *client)
 549 {
 550     client->refcount++;
 551 }
 552
 553 void nbd_client_put(NBDClient *client)
 554 {
 555     if (--client->refcount == 0) {
 556         /* The last reference should be dropped by client->close,
 557          * which is called by client_close.
 558          */
 559         assert(client->closing);
 560
 561         nbd_unset_handlers(client);
 562         close(client->sock);
 563         client->sock = -1;
 564         if (client->exp) {
 565             QTAILQ_REMOVE(&client->exp->clients, client, next);
 566             nbd_export_put(client->exp);
 567         }
 568         g_free(client);
 569     }
 570 }
 571
 572 static void client_close(NBDClient *client)
 573 {
 574     if (client->closing) {
 575         return;
 576     }
 577
 578     client->closing = true;
 579
 580     /* Force requests to finish.  They will drop their own references,
 581      * then we'll close the socket and free the NBDClient.
 582      */
 583     shutdown(client->sock, 2);
 584
 585     /* Also tell the client, so that they release their reference.  */
 586     if (client->close) {
 587         client->close(client);
 588     }
 589 }
 590
 591 static NBDRequest *nbd_request_get(NBDClient *client)
 592 {
 593     NBDRequest *req;
 594
 595     assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
 596     client->nb_requests++;
 597     nbd_update_can_read(client);
 598
 599     req = g_new0(NBDRequest, 1);
 600     nbd_client_get(client);
 601     req->client = client;
 602     return req;
 603 }
 604
 605 static void nbd_request_put(NBDRequest *req)
 606 {
 607     NBDClient *client = req->client;
 608
 609     if (req->data) {
 610         qemu_vfree(req->data);
 611     }
 612     g_free(req);
 613
 614     client->nb_requests--;
 615     nbd_update_can_read(client);
 616     nbd_client_put(client);
 617 }
 618
 619 static void blk_aio_attached(AioContext *ctx, void *opaque)
 620 {
 621     NBDExport *exp = opaque;
 622     NBDClient *client;
 623
 624     TRACE("Export %s: Attaching clients to AIO context %p\n", exp->name, ctx);
 625
 626     exp->ctx = ctx;
 627
 628     QTAILQ_FOREACH(client, &exp->clients, next) {
 629         nbd_set_handlers(client);
 630     }
 631 }
 632
 633 static void blk_aio_detach(void *opaque)
 634 {
 635     NBDExport *exp = opaque;
 636     NBDClient *client;
 637
 638     TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
 639
 640     QTAILQ_FOREACH(client, &exp->clients, next) {
 641         nbd_unset_handlers(client);
 642     }
 643
 644     exp->ctx = NULL;
 645 }
 646
 647 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
 648                           uint32_t nbdflags, void (*close)(NBDExport *),
 649                           Error **errp)
 650 {
 651     NBDExport *exp = g_malloc0(sizeof(NBDExport));
 652     exp->refcount = 1;
 653     QTAILQ_INIT(&exp->clients);
 654     exp->blk = blk;
 655     exp->dev_offset = dev_offset;
 656     exp->nbdflags = nbdflags;
 657     exp->size = size < 0 ? blk_getlength(blk) : size;
 658     if (exp->size < 0) {
 659         error_setg_errno(errp, -exp->size,
 660                          "Failed to determine the NBD export's length");
 661         goto fail;
 662     }
 663     exp->size -= exp->size % BDRV_SECTOR_SIZE;
 664
 665     exp->close = close;
 666     exp->ctx = blk_get_aio_context(blk);
 667     blk_ref(blk);
 668     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 669     /*
 670      * NBD exports are used for non-shared storage migration.  Make sure
 671      * that BDRV_O_INCOMING is cleared and the image is ready for write
 672      * access since the export could be available before migration handover.
 673      */
 674     aio_context_acquire(exp->ctx);
 675     blk_invalidate_cache(blk, NULL);
 676     aio_context_release(exp->ctx);
 677     return exp;
 678
 679 fail:
 680     g_free(exp);
 681     return NULL;
 682 }
 683
 684 NBDExport *nbd_export_find(const char *name)
 685 {
 686     NBDExport *exp;
 687     QTAILQ_FOREACH(exp, &exports, next) {
 688         if (strcmp(name, exp->name) == 0) {
 689             return exp;
 690         }
 691     }
 692
 693     return NULL;
 694 }
 695
 696 void nbd_export_set_name(NBDExport *exp, const char *name)
 697 {
 698     if (exp->name == name) {
 699         return;
 700     }
 701
 702     nbd_export_get(exp);
 703     if (exp->name != NULL) {
 704         g_free(exp->name);
 705         exp->name = NULL;
 706         QTAILQ_REMOVE(&exports, exp, next);
 707         nbd_export_put(exp);
 708     }
 709     if (name != NULL) {
 710         nbd_export_get(exp);
 711         exp->name = g_strdup(name);
 712         QTAILQ_INSERT_TAIL(&exports, exp, next);
 713     }
 714     nbd_export_put(exp);
 715 }
 716
 717 void nbd_export_close(NBDExport *exp)
 718 {
 719     NBDClient *client, *next;
 720
 721     nbd_export_get(exp);
 722     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
 723         client_close(client);
 724     }
 725     nbd_export_set_name(exp, NULL);
 726     nbd_export_put(exp);
 727 }
 728
 729 void nbd_export_get(NBDExport *exp)
 730 {
 731     assert(exp->refcount > 0);
 732     exp->refcount++;
 733 }
 734
 735 void nbd_export_put(NBDExport *exp)
 736 {
 737     assert(exp->refcount > 0);
 738     if (exp->refcount == 1) {
 739         nbd_export_close(exp);
 740     }
 741
 742     if (--exp->refcount == 0) {
 743         assert(exp->name == NULL);
 744
 745         if (exp->close) {
 746             exp->close(exp);
 747         }
 748
 749         if (exp->blk) {
 750             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
 751                                             blk_aio_detach, exp);
 752             blk_unref(exp->blk);
 753             exp->blk = NULL;
 754         }
 755
 756         g_free(exp);
 757     }
 758 }
 759
 760 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 761 {
 762     return exp->blk;
 763 }
 764
 765 void nbd_export_close_all(void)
 766 {
 767     NBDExport *exp, *next;
 768
 769     QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
 770         nbd_export_close(exp);
 771     }
 772 }
 773
 774 static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
 775                                  int len)
 776 {
 777     NBDClient *client = req->client;
 778     int csock = client->sock;
 779     ssize_t rc, ret;
 780
 781     qemu_co_mutex_lock(&client->send_lock);
 782     client->send_coroutine = qemu_coroutine_self();
 783     nbd_set_handlers(client);
 784
 785     if (!len) {
 786         rc = nbd_send_reply(csock, reply);
 787     } else {
 788         socket_set_cork(csock, 1);
 789         rc = nbd_send_reply(csock, reply);
 790         if (rc >= 0) {
 791             ret = qemu_co_send(csock, req->data, len);
 792             if (ret != len) {
 793                 rc = -EIO;
 794             }
 795         }
 796         socket_set_cork(csock, 0);
 797     }
 798
 799     client->send_coroutine = NULL;
 800     nbd_set_handlers(client);
 801     qemu_co_mutex_unlock(&client->send_lock);
 802     return rc;
 803 }
 804
 805 static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *request)
 806 {
 807     NBDClient *client = req->client;
 808     int csock = client->sock;
 809     uint32_t command;
 810     ssize_t rc;
 811
 812     client->recv_coroutine = qemu_coroutine_self();
 813     nbd_update_can_read(client);
 814
 815     rc = nbd_receive_request(csock, request);
 816     if (rc < 0) {
 817         if (rc != -EAGAIN) {
 818             rc = -EIO;
 819         }
 820         goto out;
 821     }
 822
 823     if ((request->from + request->len) < request->from) {
 824         LOG("integer overflow detected! "
 825             "you're probably being attacked");
 826         rc = -EINVAL;
 827         goto out;
 828     }
 829
 830     TRACE("Decoding type");
 831
 832     command = request->type & NBD_CMD_MASK_COMMAND;
 833     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
 834         if (request->len > NBD_MAX_BUFFER_SIZE) {
 835             LOG("len (%u) is larger than max len (%u)",
 836                 request->len, NBD_MAX_BUFFER_SIZE);
 837             rc = -EINVAL;
 838             goto out;
 839         }
 840
 841         req->data = blk_try_blockalign(client->exp->blk, request->len);
 842         if (req->data == NULL) {
 843             rc = -ENOMEM;
 844             goto out;
 845         }
 846     }
 847     if (command == NBD_CMD_WRITE) {
 848         TRACE("Reading %u byte(s)", request->len);
 849
 850         if (qemu_co_recv(csock, req->data, request->len) != request->len) {
 851             LOG("reading from socket failed");
 852             rc = -EIO;
 853             goto out;
 854         }
 855     }
 856     rc = 0;
 857
 858 out:
 859     client->recv_coroutine = NULL;
 860     nbd_update_can_read(client);
 861
 862     return rc;
 863 }
 864
 865 static void nbd_trip(void *opaque)
 866 {
 867     NBDClient *client = opaque;
 868     NBDExport *exp = client->exp;
 869     NBDRequest *req;
 870     struct nbd_request request;
 871     struct nbd_reply reply;
 872     ssize_t ret;
 873     uint32_t command;
 874
 875     TRACE("Reading request.");
 876     if (client->closing) {
 877         return;
 878     }
 879
 880     req = nbd_request_get(client);
 881     ret = nbd_co_receive_request(req, &request);
 882     if (ret == -EAGAIN) {
 883         goto done;
 884     }
 885     if (ret == -EIO) {
 886         goto out;
 887     }
 888
 889     reply.handle = request.handle;
 890     reply.error = 0;
 891
 892     if (ret < 0) {
 893         reply.error = -ret;
 894         goto error_reply;
 895     }
 896     command = request.type & NBD_CMD_MASK_COMMAND;
 897     if (command != NBD_CMD_DISC && (request.from + request.len) > exp->size) {
 898             LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
 899             ", Offset: %" PRIu64 "\n",
 900                     request.from, request.len,
 901                     (uint64_t)exp->size, (uint64_t)exp->dev_offset);
 902         LOG("requested operation past EOF--bad client?");
 903         goto invalid_request;
 904     }
 905
 906     if (client->closing) {
 907         /*
 908          * The client may be closed when we are blocked in
 909          * nbd_co_receive_request()
 910          */
 911         goto done;
 912     }
 913
 914     switch (command) {
 915     case NBD_CMD_READ:
 916         TRACE("Request type is READ");
 917
 918         if (request.type & NBD_CMD_FLAG_FUA) {
 919             ret = blk_co_flush(exp->blk);
 920             if (ret < 0) {
 921                 LOG("flush failed");
 922                 reply.error = -ret;
 923                 goto error_reply;
 924             }
 925         }
 926
 927         ret = blk_read(exp->blk,
 928                        (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
 929                        req->data, request.len / BDRV_SECTOR_SIZE);
 930         if (ret < 0) {
 931             LOG("reading from file failed");
 932             reply.error = -ret;
 933             goto error_reply;
 934         }
 935
 936         TRACE("Read %u byte(s)", request.len);
 937         if (nbd_co_send_reply(req, &reply, request.len) < 0)
 938             goto out;
 939         break;
 940     case NBD_CMD_WRITE:
 941         TRACE("Request type is WRITE");
 942
 943         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
 944             TRACE("Server is read-only, return error");
 945             reply.error = EROFS;
 946             goto error_reply;
 947         }
 948
 949         TRACE("Writing to device");
 950
 951         ret = blk_write(exp->blk,
 952                         (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
 953                         req->data, request.len / BDRV_SECTOR_SIZE);
 954         if (ret < 0) {
 955             LOG("writing to file failed");
 956             reply.error = -ret;
 957             goto error_reply;
 958         }
 959
 960         if (request.type & NBD_CMD_FLAG_FUA) {
 961             ret = blk_co_flush(exp->blk);
 962             if (ret < 0) {
 963                 LOG("flush failed");
 964                 reply.error = -ret;
 965                 goto error_reply;
 966             }
 967         }
 968
 969         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 970             goto out;
 971         }
 972         break;
 973     case NBD_CMD_DISC:
 974         TRACE("Request type is DISCONNECT");
 975         errno = 0;
 976         goto out;
 977     case NBD_CMD_FLUSH:
 978         TRACE("Request type is FLUSH");
 979
 980         ret = blk_co_flush(exp->blk);
 981         if (ret < 0) {
 982             LOG("flush failed");
 983             reply.error = -ret;
 984         }
 985         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 986             goto out;
 987         }
 988         break;
 989     case NBD_CMD_TRIM:
 990         TRACE("Request type is TRIM");
 991         ret = blk_co_discard(exp->blk, (request.from + exp->dev_offset)
 992                                        / BDRV_SECTOR_SIZE,
 993                              request.len / BDRV_SECTOR_SIZE);
 994         if (ret < 0) {
 995             LOG("discard failed");
 996             reply.error = -ret;
 997         }
 998         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 999             goto out;
1000         }
1001         break;
1002     default:
1003         LOG("invalid request type (%u) received", request.type);
1004     invalid_request:
1005         reply.error = EINVAL;
1006     error_reply:
1007         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1008             goto out;
1009         }
1010         break;
1011     }
1012
1013     TRACE("Request/Reply complete");
1014
1015 done:
1016     nbd_request_put(req);
1017     return;
1018
1019 out:
1020     nbd_request_put(req);
1021     client_close(client);
1022 }
1023
1024 static void nbd_read(void *opaque)
1025 {
1026     NBDClient *client = opaque;
1027
1028     if (client->recv_coroutine) {
1029         qemu_coroutine_enter(client->recv_coroutine, NULL);
1030     } else {
1031         qemu_coroutine_enter(qemu_coroutine_create(nbd_trip), client);
1032     }
1033 }
1034
1035 static void nbd_restart_write(void *opaque)
1036 {
1037     NBDClient *client = opaque;
1038
1039     qemu_coroutine_enter(client->send_coroutine, NULL);
1040 }
1041
1042 static void nbd_set_handlers(NBDClient *client)
1043 {
1044     if (client->exp && client->exp->ctx) {
1045         aio_set_fd_handler(client->exp->ctx, client->sock,
1046                            true,
1047                            client->can_read ? nbd_read : NULL,
1048                            client->send_coroutine ? nbd_restart_write : NULL,
1049                            client);
1050     }
1051 }
1052
1053 static void nbd_unset_handlers(NBDClient *client)
1054 {
1055     if (client->exp && client->exp->ctx) {
1056         aio_set_fd_handler(client->exp->ctx, client->sock,
1057                            true, NULL, NULL, NULL);
1058     }
1059 }
1060
1061 static void nbd_update_can_read(NBDClient *client)
1062 {
1063     bool can_read = client->recv_coroutine ||
1064                     client->nb_requests < MAX_NBD_REQUESTS;
1065
1066     if (can_read != client->can_read) {
1067         client->can_read = can_read;
1068         nbd_set_handlers(client);
1069
1070         /* There is no need to invoke aio_notify(), since aio_set_fd_handler()
1071          * in nbd_set_handlers() will have taken care of that */
1072     }
1073 }
1074
1075 static coroutine_fn void nbd_co_client_start(void *opaque)
1076 {
1077     NBDClientNewData *data = opaque;
1078     NBDClient *client = data->client;
1079     NBDExport *exp = client->exp;
1080
1081     if (exp) {
1082         nbd_export_get(exp);
1083     }
1084     if (nbd_negotiate(data)) {
1085         shutdown(client->sock, 2);
1086         client->close(client);
1087         goto out;
1088     }
1089     qemu_co_mutex_init(&client->send_lock);
1090     nbd_set_handlers(client);
1091
1092     if (exp) {
1093         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
1094     }
1095 out:
1096     g_free(data);
1097 }
1098
1099 void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *))
1100 {
1101     NBDClient *client;
1102     NBDClientNewData *data = g_new(NBDClientNewData, 1);
1103
1104     client = g_malloc0(sizeof(NBDClient));
1105     client->refcount = 1;
1106     client->exp = exp;
1107     client->sock = csock;
1108     client->can_read = true;
1109     client->close = close_fn;
1110
1111     data->client = client;
1112     data->co = qemu_coroutine_create(nbd_co_client_start);
1113     qemu_coroutine_enter(data->co, data);
1114 }