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     blk_invalidate_cache(blk, NULL);
 675     return exp;
 676
 677 fail:
 678     g_free(exp);
 679     return NULL;
 680 }
 681
 682 NBDExport *nbd_export_find(const char *name)
 683 {
 684     NBDExport *exp;
 685     QTAILQ_FOREACH(exp, &exports, next) {
 686         if (strcmp(name, exp->name) == 0) {
 687             return exp;
 688         }
 689     }
 690
 691     return NULL;
 692 }
 693
 694 void nbd_export_set_name(NBDExport *exp, const char *name)
 695 {
 696     if (exp->name == name) {
 697         return;
 698     }
 699
 700     nbd_export_get(exp);
 701     if (exp->name != NULL) {
 702         g_free(exp->name);
 703         exp->name = NULL;
 704         QTAILQ_REMOVE(&exports, exp, next);
 705         nbd_export_put(exp);
 706     }
 707     if (name != NULL) {
 708         nbd_export_get(exp);
 709         exp->name = g_strdup(name);
 710         QTAILQ_INSERT_TAIL(&exports, exp, next);
 711     }
 712     nbd_export_put(exp);
 713 }
 714
 715 void nbd_export_close(NBDExport *exp)
 716 {
 717     NBDClient *client, *next;
 718
 719     nbd_export_get(exp);
 720     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
 721         client_close(client);
 722     }
 723     nbd_export_set_name(exp, NULL);
 724     nbd_export_put(exp);
 725 }
 726
 727 void nbd_export_get(NBDExport *exp)
 728 {
 729     assert(exp->refcount > 0);
 730     exp->refcount++;
 731 }
 732
 733 void nbd_export_put(NBDExport *exp)
 734 {
 735     assert(exp->refcount > 0);
 736     if (exp->refcount == 1) {
 737         nbd_export_close(exp);
 738     }
 739
 740     if (--exp->refcount == 0) {
 741         assert(exp->name == NULL);
 742
 743         if (exp->close) {
 744             exp->close(exp);
 745         }
 746
 747         if (exp->blk) {
 748             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
 749                                             blk_aio_detach, exp);
 750             blk_unref(exp->blk);
 751             exp->blk = NULL;
 752         }
 753
 754         g_free(exp);
 755     }
 756 }
 757
 758 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 759 {
 760     return exp->blk;
 761 }
 762
 763 void nbd_export_close_all(void)
 764 {
 765     NBDExport *exp, *next;
 766
 767     QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
 768         nbd_export_close(exp);
 769     }
 770 }
 771
 772 static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
 773                                  int len)
 774 {
 775     NBDClient *client = req->client;
 776     int csock = client->sock;
 777     ssize_t rc, ret;
 778
 779     qemu_co_mutex_lock(&client->send_lock);
 780     client->send_coroutine = qemu_coroutine_self();
 781     nbd_set_handlers(client);
 782
 783     if (!len) {
 784         rc = nbd_send_reply(csock, reply);
 785     } else {
 786         socket_set_cork(csock, 1);
 787         rc = nbd_send_reply(csock, reply);
 788         if (rc >= 0) {
 789             ret = qemu_co_send(csock, req->data, len);
 790             if (ret != len) {
 791                 rc = -EIO;
 792             }
 793         }
 794         socket_set_cork(csock, 0);
 795     }
 796
 797     client->send_coroutine = NULL;
 798     nbd_set_handlers(client);
 799     qemu_co_mutex_unlock(&client->send_lock);
 800     return rc;
 801 }
 802
 803 static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *request)
 804 {
 805     NBDClient *client = req->client;
 806     int csock = client->sock;
 807     uint32_t command;
 808     ssize_t rc;
 809
 810     client->recv_coroutine = qemu_coroutine_self();
 811     nbd_update_can_read(client);
 812
 813     rc = nbd_receive_request(csock, request);
 814     if (rc < 0) {
 815         if (rc != -EAGAIN) {
 816             rc = -EIO;
 817         }
 818         goto out;
 819     }
 820
 821     if ((request->from + request->len) < request->from) {
 822         LOG("integer overflow detected! "
 823             "you're probably being attacked");
 824         rc = -EINVAL;
 825         goto out;
 826     }
 827
 828     TRACE("Decoding type");
 829
 830     command = request->type & NBD_CMD_MASK_COMMAND;
 831     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
 832         if (request->len > NBD_MAX_BUFFER_SIZE) {
 833             LOG("len (%u) is larger than max len (%u)",
 834                 request->len, NBD_MAX_BUFFER_SIZE);
 835             rc = -EINVAL;
 836             goto out;
 837         }
 838
 839         req->data = blk_try_blockalign(client->exp->blk, request->len);
 840         if (req->data == NULL) {
 841             rc = -ENOMEM;
 842             goto out;
 843         }
 844     }
 845     if (command == NBD_CMD_WRITE) {
 846         TRACE("Reading %u byte(s)", request->len);
 847
 848         if (qemu_co_recv(csock, req->data, request->len) != request->len) {
 849             LOG("reading from socket failed");
 850             rc = -EIO;
 851             goto out;
 852         }
 853     }
 854     rc = 0;
 855
 856 out:
 857     client->recv_coroutine = NULL;
 858     nbd_update_can_read(client);
 859
 860     return rc;
 861 }
 862
 863 static void nbd_trip(void *opaque)
 864 {
 865     NBDClient *client = opaque;
 866     NBDExport *exp = client->exp;
 867     NBDRequest *req;
 868     struct nbd_request request;
 869     struct nbd_reply reply;
 870     ssize_t ret;
 871     uint32_t command;
 872
 873     TRACE("Reading request.");
 874     if (client->closing) {
 875         return;
 876     }
 877
 878     req = nbd_request_get(client);
 879     ret = nbd_co_receive_request(req, &request);
 880     if (ret == -EAGAIN) {
 881         goto done;
 882     }
 883     if (ret == -EIO) {
 884         goto out;
 885     }
 886
 887     reply.handle = request.handle;
 888     reply.error = 0;
 889
 890     if (ret < 0) {
 891         reply.error = -ret;
 892         goto error_reply;
 893     }
 894     command = request.type & NBD_CMD_MASK_COMMAND;
 895     if (command != NBD_CMD_DISC && (request.from + request.len) > exp->size) {
 896             LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
 897             ", Offset: %" PRIu64 "\n",
 898                     request.from, request.len,
 899                     (uint64_t)exp->size, (uint64_t)exp->dev_offset);
 900         LOG("requested operation past EOF--bad client?");
 901         goto invalid_request;
 902     }
 903
 904     if (client->closing) {
 905         /*
 906          * The client may be closed when we are blocked in
 907          * nbd_co_receive_request()
 908          */
 909         goto done;
 910     }
 911
 912     switch (command) {
 913     case NBD_CMD_READ:
 914         TRACE("Request type is READ");
 915
 916         if (request.type & NBD_CMD_FLAG_FUA) {
 917             ret = blk_co_flush(exp->blk);
 918             if (ret < 0) {
 919                 LOG("flush failed");
 920                 reply.error = -ret;
 921                 goto error_reply;
 922             }
 923         }
 924
 925         ret = blk_read(exp->blk,
 926                        (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
 927                        req->data, request.len / BDRV_SECTOR_SIZE);
 928         if (ret < 0) {
 929             LOG("reading from file failed");
 930             reply.error = -ret;
 931             goto error_reply;
 932         }
 933
 934         TRACE("Read %u byte(s)", request.len);
 935         if (nbd_co_send_reply(req, &reply, request.len) < 0)
 936             goto out;
 937         break;
 938     case NBD_CMD_WRITE:
 939         TRACE("Request type is WRITE");
 940
 941         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
 942             TRACE("Server is read-only, return error");
 943             reply.error = EROFS;
 944             goto error_reply;
 945         }
 946
 947         TRACE("Writing to device");
 948
 949         ret = blk_write(exp->blk,
 950                         (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
 951                         req->data, request.len / BDRV_SECTOR_SIZE);
 952         if (ret < 0) {
 953             LOG("writing to file failed");
 954             reply.error = -ret;
 955             goto error_reply;
 956         }
 957
 958         if (request.type & NBD_CMD_FLAG_FUA) {
 959             ret = blk_co_flush(exp->blk);
 960             if (ret < 0) {
 961                 LOG("flush failed");
 962                 reply.error = -ret;
 963                 goto error_reply;
 964             }
 965         }
 966
 967         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 968             goto out;
 969         }
 970         break;
 971     case NBD_CMD_DISC:
 972         TRACE("Request type is DISCONNECT");
 973         errno = 0;
 974         goto out;
 975     case NBD_CMD_FLUSH:
 976         TRACE("Request type is FLUSH");
 977
 978         ret = blk_co_flush(exp->blk);
 979         if (ret < 0) {
 980             LOG("flush failed");
 981             reply.error = -ret;
 982         }
 983         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 984             goto out;
 985         }
 986         break;
 987     case NBD_CMD_TRIM:
 988         TRACE("Request type is TRIM");
 989         ret = blk_co_discard(exp->blk, (request.from + exp->dev_offset)
 990                                        / BDRV_SECTOR_SIZE,
 991                              request.len / BDRV_SECTOR_SIZE);
 992         if (ret < 0) {
 993             LOG("discard failed");
 994             reply.error = -ret;
 995         }
 996         if (nbd_co_send_reply(req, &reply, 0) < 0) {
 997             goto out;
 998         }
 999         break;
1000     default:
1001         LOG("invalid request type (%u) received", request.type);
1002     invalid_request:
1003         reply.error = EINVAL;
1004     error_reply:
1005         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1006             goto out;
1007         }
1008         break;
1009     }
1010
1011     TRACE("Request/Reply complete");
1012
1013 done:
1014     nbd_request_put(req);
1015     return;
1016
1017 out:
1018     nbd_request_put(req);
1019     client_close(client);
1020 }
1021
1022 static void nbd_read(void *opaque)
1023 {
1024     NBDClient *client = opaque;
1025
1026     if (client->recv_coroutine) {
1027         qemu_coroutine_enter(client->recv_coroutine, NULL);
1028     } else {
1029         qemu_coroutine_enter(qemu_coroutine_create(nbd_trip), client);
1030     }
1031 }
1032
1033 static void nbd_restart_write(void *opaque)
1034 {
1035     NBDClient *client = opaque;
1036
1037     qemu_coroutine_enter(client->send_coroutine, NULL);
1038 }
1039
1040 static void nbd_set_handlers(NBDClient *client)
1041 {
1042     if (client->exp && client->exp->ctx) {
1043         aio_set_fd_handler(client->exp->ctx, client->sock,
1044                            true,
1045                            client->can_read ? nbd_read : NULL,
1046                            client->send_coroutine ? nbd_restart_write : NULL,
1047                            client);
1048     }
1049 }
1050
1051 static void nbd_unset_handlers(NBDClient *client)
1052 {
1053     if (client->exp && client->exp->ctx) {
1054         aio_set_fd_handler(client->exp->ctx, client->sock,
1055                            true, NULL, NULL, NULL);
1056     }
1057 }
1058
1059 static void nbd_update_can_read(NBDClient *client)
1060 {
1061     bool can_read = client->recv_coroutine ||
1062                     client->nb_requests < MAX_NBD_REQUESTS;
1063
1064     if (can_read != client->can_read) {
1065         client->can_read = can_read;
1066         nbd_set_handlers(client);
1067
1068         /* There is no need to invoke aio_notify(), since aio_set_fd_handler()
1069          * in nbd_set_handlers() will have taken care of that */
1070     }
1071 }
1072
1073 static coroutine_fn void nbd_co_client_start(void *opaque)
1074 {
1075     NBDClientNewData *data = opaque;
1076     NBDClient *client = data->client;
1077     NBDExport *exp = client->exp;
1078
1079     if (exp) {
1080         nbd_export_get(exp);
1081     }
1082     if (nbd_negotiate(data)) {
1083         shutdown(client->sock, 2);
1084         client->close(client);
1085         goto out;
1086     }
1087     qemu_co_mutex_init(&client->send_lock);
1088     nbd_set_handlers(client);
1089
1090     if (exp) {
1091         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
1092     }
1093 out:
1094     g_free(data);
1095 }
1096
1097 void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *))
1098 {
1099     NBDClient *client;
1100     NBDClientNewData *data = g_new(NBDClientNewData, 1);
1101
1102     client = g_malloc0(sizeof(NBDClient));
1103     client->refcount = 1;
1104     client->exp = exp;
1105     client->sock = csock;
1106     client->can_read = true;
1107     client->close = close_fn;
1108
1109     data->client = client;
1110     data->co = qemu_coroutine_create(nbd_co_client_start);
1111     qemu_coroutine_enter(data->co, data);
1112 }