nbd.c

   1 /*
   2  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   3  *
   4  *  Network Block Device
   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.h"
  20 #include "block.h"
  21 #include "block_int.h"
  22
  23 #include <errno.h>
  24 #include <string.h>
  25 #ifndef _WIN32
  26 #include <sys/ioctl.h>
  27 #endif
  28 #if defined(__sun__) || defined(__HAIKU__)
  29 #include <sys/ioccom.h>
  30 #endif
  31 #include <ctype.h>
  32 #include <inttypes.h>
  33
  34 #ifdef __linux__
  35 #include <linux/fs.h>
  36 #endif
  37
  38 #include "qemu_socket.h"
  39
  40 //#define DEBUG_NBD
  41
  42 #ifdef DEBUG_NBD
  43 #define TRACE(msg, ...) do { \
  44     LOG(msg, ## __VA_ARGS__); \
  45 } while(0)
  46 #else
  47 #define TRACE(msg, ...) \
  48     do { } while (0)
  49 #endif
  50
  51 #define LOG(msg, ...) do { \
  52     fprintf(stderr, "%s:%s():L%d: " msg "\n", \
  53             __FILE__, __FUNCTION__, __LINE__, ## __VA_ARGS__); \
  54 } while(0)
  55
  56 /* This is all part of the "official" NBD API */
  57
  58 #define NBD_REPLY_SIZE          (4 + 4 + 8)
  59 #define NBD_REQUEST_MAGIC       0x25609513
  60 #define NBD_REPLY_MAGIC         0x67446698
  61
  62 #define NBD_SET_SOCK            _IO(0xab, 0)
  63 #define NBD_SET_BLKSIZE         _IO(0xab, 1)
  64 #define NBD_SET_SIZE            _IO(0xab, 2)
  65 #define NBD_DO_IT               _IO(0xab, 3)
  66 #define NBD_CLEAR_SOCK          _IO(0xab, 4)
  67 #define NBD_CLEAR_QUE           _IO(0xab, 5)
  68 #define NBD_PRINT_DEBUG         _IO(0xab, 6)
  69 #define NBD_SET_SIZE_BLOCKS     _IO(0xab, 7)
  70 #define NBD_DISCONNECT          _IO(0xab, 8)
  71 #define NBD_SET_TIMEOUT         _IO(0xab, 9)
  72 #define NBD_SET_FLAGS           _IO(0xab, 10)
  73
  74 #define NBD_OPT_EXPORT_NAME     (1 << 0)
  75
  76 /* That's all folks */
  77
  78 #define read_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, true)
  79 #define write_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, false)
  80
  81 size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
  82 {
  83     size_t offset = 0;
  84
  85     if (qemu_in_coroutine()) {
  86         if (do_read) {
  87             return qemu_co_recv(fd, buffer, size);
  88         } else {
  89             return qemu_co_send(fd, buffer, size);
  90         }
  91     }
  92
  93     while (offset < size) {
  94         ssize_t len;
  95
  96         if (do_read) {
  97             len = qemu_recv(fd, buffer + offset, size - offset, 0);
  98         } else {
  99             len = send(fd, buffer + offset, size - offset, 0);
 100         }
 101
 102         if (len == -1)
 103             errno = socket_error();
 104
 105         /* recoverable error */
 106         if (len == -1 && (errno == EAGAIN || errno == EINTR)) {
 107             continue;
 108         }
 109
 110         /* eof */
 111         if (len == 0) {
 112             break;
 113         }
 114
 115         /* unrecoverable error */
 116         if (len == -1) {
 117             return 0;
 118         }
 119
 120         offset += len;
 121     }
 122
 123     return offset;
 124 }
 125
 126 static void combine_addr(char *buf, size_t len, const char* address,
 127                          uint16_t port)
 128 {
 129     /* If the address-part contains a colon, it's an IPv6 IP so needs [] */
 130     if (strstr(address, ":")) {
 131         snprintf(buf, len, "[%s]:%u", address, port);
 132     } else {
 133         snprintf(buf, len, "%s:%u", address, port);
 134     }
 135 }
 136
 137 int tcp_socket_outgoing(const char *address, uint16_t port)
 138 {
 139     char address_and_port[128];
 140     combine_addr(address_and_port, 128, address, port);
 141     return tcp_socket_outgoing_spec(address_and_port);
 142 }
 143
 144 int tcp_socket_outgoing_spec(const char *address_and_port)
 145 {
 146     return inet_connect(address_and_port, SOCK_STREAM);
 147 }
 148
 149 int tcp_socket_incoming(const char *address, uint16_t port)
 150 {
 151     char address_and_port[128];
 152     combine_addr(address_and_port, 128, address, port);
 153     return tcp_socket_incoming_spec(address_and_port);
 154 }
 155
 156 int tcp_socket_incoming_spec(const char *address_and_port)
 157 {
 158     char *ostr  = NULL;
 159     int olen = 0;
 160     return inet_listen(address_and_port, ostr, olen, SOCK_STREAM, 0);
 161 }
 162
 163 int unix_socket_incoming(const char *path)
 164 {
 165     char *ostr = NULL;
 166     int olen = 0;
 167
 168     return unix_listen(path, ostr, olen);
 169 }
 170
 171 int unix_socket_outgoing(const char *path)
 172 {
 173     return unix_connect(path);
 174 }
 175
 176 /* Basic flow
 177
 178    Server         Client
 179
 180    Negotiate
 181                   Request
 182    Response
 183                   Request
 184    Response
 185                   ...
 186    ...
 187                   Request (type == 2)
 188 */
 189
 190 static int nbd_send_negotiate(int csock, off_t size, uint32_t flags)
 191 {
 192     char buf[8 + 8 + 8 + 128];
 193
 194     /* Negotiate
 195         [ 0 ..   7]   passwd   ("NBDMAGIC")
 196         [ 8 ..  15]   magic    (0x00420281861253)
 197         [16 ..  23]   size
 198         [24 ..  27]   flags
 199         [28 .. 151]   reserved (0)
 200      */
 201
 202     TRACE("Beginning negotiation.");
 203     memcpy(buf, "NBDMAGIC", 8);
 204     cpu_to_be64w((uint64_t*)(buf + 8), 0x00420281861253LL);
 205     cpu_to_be64w((uint64_t*)(buf + 16), size);
 206     cpu_to_be32w((uint32_t*)(buf + 24),
 207                  flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
 208                  NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
 209     memset(buf + 28, 0, 124);
 210
 211     if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
 212         LOG("write failed");
 213         errno = EINVAL;
 214         return -1;
 215     }
 216
 217     TRACE("Negotiation succeeded.");
 218
 219     return 0;
 220 }
 221
 222 int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
 223                           off_t *size, size_t *blocksize)
 224 {
 225     char buf[256];
 226     uint64_t magic, s;
 227     uint16_t tmp;
 228
 229     TRACE("Receiving negotiation.");
 230
 231     if (read_sync(csock, buf, 8) != 8) {
 232         LOG("read failed");
 233         errno = EINVAL;
 234         return -1;
 235     }
 236
 237     buf[8] = '\0';
 238     if (strlen(buf) == 0) {
 239         LOG("server connection closed");
 240         errno = EINVAL;
 241         return -1;
 242     }
 243
 244     TRACE("Magic is %c%c%c%c%c%c%c%c",
 245           qemu_isprint(buf[0]) ? buf[0] : '.',
 246           qemu_isprint(buf[1]) ? buf[1] : '.',
 247           qemu_isprint(buf[2]) ? buf[2] : '.',
 248           qemu_isprint(buf[3]) ? buf[3] : '.',
 249           qemu_isprint(buf[4]) ? buf[4] : '.',
 250           qemu_isprint(buf[5]) ? buf[5] : '.',
 251           qemu_isprint(buf[6]) ? buf[6] : '.',
 252           qemu_isprint(buf[7]) ? buf[7] : '.');
 253
 254     if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 255         LOG("Invalid magic received");
 256         errno = EINVAL;
 257         return -1;
 258     }
 259
 260     if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
 261         LOG("read failed");
 262         errno = EINVAL;
 263         return -1;
 264     }
 265     magic = be64_to_cpu(magic);
 266     TRACE("Magic is 0x%" PRIx64, magic);
 267
 268     if (name) {
 269         uint32_t reserved = 0;
 270         uint32_t opt;
 271         uint32_t namesize;
 272
 273         TRACE("Checking magic (opts_magic)");
 274         if (magic != 0x49484156454F5054LL) {
 275             LOG("Bad magic received");
 276             errno = EINVAL;
 277             return -1;
 278         }
 279         if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
 280             LOG("flags read failed");
 281             errno = EINVAL;
 282             return -1;
 283         }
 284         *flags = be16_to_cpu(tmp) << 16;
 285         /* reserved for future use */
 286         if (write_sync(csock, &reserved, sizeof(reserved)) !=
 287             sizeof(reserved)) {
 288             LOG("write failed (reserved)");
 289             errno = EINVAL;
 290             return -1;
 291         }
 292         /* write the export name */
 293         magic = cpu_to_be64(magic);
 294         if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
 295             LOG("write failed (magic)");
 296             errno = EINVAL;
 297             return -1;
 298         }
 299         opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
 300         if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
 301             LOG("write failed (opt)");
 302             errno = EINVAL;
 303             return -1;
 304         }
 305         namesize = cpu_to_be32(strlen(name));
 306         if (write_sync(csock, &namesize, sizeof(namesize)) !=
 307             sizeof(namesize)) {
 308             LOG("write failed (namesize)");
 309             errno = EINVAL;
 310             return -1;
 311         }
 312         if (write_sync(csock, (char*)name, strlen(name)) != strlen(name)) {
 313             LOG("write failed (name)");
 314             errno = EINVAL;
 315             return -1;
 316         }
 317     } else {
 318         TRACE("Checking magic (cli_magic)");
 319
 320         if (magic != 0x00420281861253LL) {
 321             LOG("Bad magic received");
 322             errno = EINVAL;
 323             return -1;
 324         }
 325     }
 326
 327     if (read_sync(csock, &s, sizeof(s)) != sizeof(s)) {
 328         LOG("read failed");
 329         errno = EINVAL;
 330         return -1;
 331     }
 332     *size = be64_to_cpu(s);
 333     *blocksize = 1024;
 334     TRACE("Size is %" PRIu64, *size);
 335
 336     if (!name) {
 337         if (read_sync(csock, flags, sizeof(*flags)) != sizeof(*flags)) {
 338             LOG("read failed (flags)");
 339             errno = EINVAL;
 340             return -1;
 341         }
 342         *flags = be32_to_cpup(flags);
 343     } else {
 344         if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
 345             LOG("read failed (tmp)");
 346             errno = EINVAL;
 347             return -1;
 348         }
 349         *flags |= be32_to_cpu(tmp);
 350     }
 351     if (read_sync(csock, &buf, 124) != 124) {
 352         LOG("read failed (buf)");
 353         errno = EINVAL;
 354         return -1;
 355     }
 356         return 0;
 357 }
 358
 359 #ifdef __linux__
 360 int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
 361 {
 362     TRACE("Setting NBD socket");
 363
 364     if (ioctl(fd, NBD_SET_SOCK, csock) == -1) {
 365         int serrno = errno;
 366         LOG("Failed to set NBD socket");
 367         errno = serrno;
 368         return -1;
 369     }
 370
 371     TRACE("Setting block size to %lu", (unsigned long)blocksize);
 372
 373     if (ioctl(fd, NBD_SET_BLKSIZE, blocksize) == -1) {
 374         int serrno = errno;
 375         LOG("Failed setting NBD block size");
 376         errno = serrno;
 377         return -1;
 378     }
 379
 380         TRACE("Setting size to %zd block(s)", (size_t)(size / blocksize));
 381
 382     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / blocksize) == -1) {
 383         int serrno = errno;
 384         LOG("Failed setting size (in blocks)");
 385         errno = serrno;
 386         return -1;
 387     }
 388
 389     if (flags & NBD_FLAG_READ_ONLY) {
 390         int read_only = 1;
 391         TRACE("Setting readonly attribute");
 392
 393         if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
 394             int serrno = errno;
 395             LOG("Failed setting read-only attribute");
 396             errno = serrno;
 397             return -1;
 398         }
 399     }
 400
 401     if (ioctl(fd, NBD_SET_FLAGS, flags) < 0
 402         && errno != ENOTTY) {
 403         int serrno = errno;
 404         LOG("Failed setting flags");
 405         errno = serrno;
 406         return -1;
 407     }
 408
 409     TRACE("Negotiation ended");
 410
 411     return 0;
 412 }
 413
 414 int nbd_disconnect(int fd)
 415 {
 416     ioctl(fd, NBD_CLEAR_QUE);
 417     ioctl(fd, NBD_DISCONNECT);
 418     ioctl(fd, NBD_CLEAR_SOCK);
 419     return 0;
 420 }
 421
 422 int nbd_client(int fd)
 423 {
 424     int ret;
 425     int serrno;
 426
 427     TRACE("Doing NBD loop");
 428
 429     ret = ioctl(fd, NBD_DO_IT);
 430     if (ret == -1 && errno == EPIPE) {
 431         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
 432          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
 433          * that case.
 434          */
 435         ret = 0;
 436     }
 437     serrno = errno;
 438
 439     TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
 440
 441     TRACE("Clearing NBD queue");
 442     ioctl(fd, NBD_CLEAR_QUE);
 443
 444     TRACE("Clearing NBD socket");
 445     ioctl(fd, NBD_CLEAR_SOCK);
 446
 447     errno = serrno;
 448     return ret;
 449 }
 450 #else
 451 int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
 452 {
 453     errno = ENOTSUP;
 454     return -1;
 455 }
 456
 457 int nbd_disconnect(int fd)
 458 {
 459     errno = ENOTSUP;
 460     return -1;
 461 }
 462
 463 int nbd_client(int fd)
 464 {
 465     errno = ENOTSUP;
 466     return -1;
 467 }
 468 #endif
 469
 470 int nbd_send_request(int csock, struct nbd_request *request)
 471 {
 472     uint8_t buf[4 + 4 + 8 + 8 + 4];
 473
 474     cpu_to_be32w((uint32_t*)buf, NBD_REQUEST_MAGIC);
 475     cpu_to_be32w((uint32_t*)(buf + 4), request->type);
 476     cpu_to_be64w((uint64_t*)(buf + 8), request->handle);
 477     cpu_to_be64w((uint64_t*)(buf + 16), request->from);
 478     cpu_to_be32w((uint32_t*)(buf + 24), request->len);
 479
 480     TRACE("Sending request to client: "
 481           "{ .from = %" PRIu64", .len = %u, .handle = %" PRIu64", .type=%i}",
 482           request->from, request->len, request->handle, request->type);
 483
 484     if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
 485         LOG("writing to socket failed");
 486         errno = EINVAL;
 487         return -1;
 488     }
 489     return 0;
 490 }
 491
 492 static int nbd_receive_request(int csock, struct nbd_request *request)
 493 {
 494     uint8_t buf[4 + 4 + 8 + 8 + 4];
 495     uint32_t magic;
 496
 497     if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
 498         LOG("read failed");
 499         errno = EINVAL;
 500         return -1;
 501     }
 502
 503     /* Request
 504        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
 505        [ 4 ..  7]   type    (0 == READ, 1 == WRITE)
 506        [ 8 .. 15]   handle
 507        [16 .. 23]   from
 508        [24 .. 27]   len
 509      */
 510
 511     magic = be32_to_cpup((uint32_t*)buf);
 512     request->type  = be32_to_cpup((uint32_t*)(buf + 4));
 513     request->handle = be64_to_cpup((uint64_t*)(buf + 8));
 514     request->from  = be64_to_cpup((uint64_t*)(buf + 16));
 515     request->len   = be32_to_cpup((uint32_t*)(buf + 24));
 516
 517     TRACE("Got request: "
 518           "{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }",
 519           magic, request->type, request->from, request->len);
 520
 521     if (magic != NBD_REQUEST_MAGIC) {
 522         LOG("invalid magic (got 0x%x)", magic);
 523         errno = EINVAL;
 524         return -1;
 525     }
 526     return 0;
 527 }
 528
 529 int nbd_receive_reply(int csock, struct nbd_reply *reply)
 530 {
 531     uint8_t buf[NBD_REPLY_SIZE];
 532     uint32_t magic;
 533
 534     memset(buf, 0xAA, sizeof(buf));
 535
 536     if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
 537         LOG("read failed");
 538         errno = EINVAL;
 539         return -1;
 540     }
 541
 542     /* Reply
 543        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 544        [ 4 ..  7]    error   (0 == no error)
 545        [ 7 .. 15]    handle
 546      */
 547
 548     magic = be32_to_cpup((uint32_t*)buf);
 549     reply->error  = be32_to_cpup((uint32_t*)(buf + 4));
 550     reply->handle = be64_to_cpup((uint64_t*)(buf + 8));
 551
 552     TRACE("Got reply: "
 553           "{ magic = 0x%x, .error = %d, handle = %" PRIu64" }",
 554           magic, reply->error, reply->handle);
 555
 556     if (magic != NBD_REPLY_MAGIC) {
 557         LOG("invalid magic (got 0x%x)", magic);
 558         errno = EINVAL;
 559         return -1;
 560     }
 561     return 0;
 562 }
 563
 564 static int nbd_send_reply(int csock, struct nbd_reply *reply)
 565 {
 566     uint8_t buf[4 + 4 + 8];
 567
 568     /* Reply
 569        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 570        [ 4 ..  7]    error   (0 == no error)
 571        [ 7 .. 15]    handle
 572      */
 573     cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC);
 574     cpu_to_be32w((uint32_t*)(buf + 4), reply->error);
 575     cpu_to_be64w((uint64_t*)(buf + 8), reply->handle);
 576
 577     TRACE("Sending response to client");
 578
 579     if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
 580         LOG("writing to socket failed");
 581         errno = EINVAL;
 582         return -1;
 583     }
 584     return 0;
 585 }
 586
 587 struct NBDExport {
 588     BlockDriverState *bs;
 589     off_t dev_offset;
 590     off_t size;
 591     uint8_t *data;
 592     uint32_t nbdflags;
 593 };
 594
 595 NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
 596                           off_t size, uint32_t nbdflags)
 597 {
 598     NBDExport *exp = g_malloc0(sizeof(NBDExport));
 599     exp->bs = bs;
 600     exp->dev_offset = dev_offset;
 601     exp->nbdflags = nbdflags;
 602     exp->size = size == -1 ? exp->bs->total_sectors * 512 : size;
 603     exp->data = qemu_blockalign(exp->bs, NBD_BUFFER_SIZE);
 604     return exp;
 605 }
 606
 607 void nbd_export_close(NBDExport *exp)
 608 {
 609     qemu_vfree(exp->data);
 610     bdrv_close(exp->bs);
 611     g_free(exp);
 612 }
 613
 614 static int nbd_do_send_reply(int csock, struct nbd_reply *reply,
 615                              uint8_t *data, int len)
 616 {
 617     int rc, ret;
 618
 619     if (!len) {
 620         rc = nbd_send_reply(csock, reply);
 621         if (rc == -1) {
 622             rc = -errno;
 623         }
 624     } else {
 625         socket_set_cork(csock, 1);
 626         rc = nbd_send_reply(csock, reply);
 627         if (rc != -1) {
 628             ret = write_sync(csock, data, len);
 629             if (ret != len) {
 630                 errno = EIO;
 631                 rc = -1;
 632             }
 633         }
 634         if (rc == -1) {
 635             rc = -errno;
 636         }
 637         socket_set_cork(csock, 0);
 638     }
 639     return rc;
 640 }
 641
 642 static int nbd_do_receive_request(int csock, struct nbd_request *request,
 643                                   uint8_t *data)
 644 {
 645     int rc;
 646
 647     if (nbd_receive_request(csock, request) == -1) {
 648         rc = -EIO;
 649         goto out;
 650     }
 651
 652     if (request->len > NBD_BUFFER_SIZE) {
 653         LOG("len (%u) is larger than max len (%u)",
 654             request->len, NBD_BUFFER_SIZE);
 655         rc = -EINVAL;
 656         goto out;
 657     }
 658
 659     if ((request->from + request->len) < request->from) {
 660         LOG("integer overflow detected! "
 661             "you're probably being attacked");
 662         rc = -EINVAL;
 663         goto out;
 664     }
 665
 666     TRACE("Decoding type");
 667
 668     if ((request->type & NBD_CMD_MASK_COMMAND) == NBD_CMD_WRITE) {
 669         TRACE("Reading %u byte(s)", request->len);
 670
 671         if (read_sync(csock, data, request->len) != request->len) {
 672             LOG("reading from socket failed");
 673             rc = -EIO;
 674             goto out;
 675         }
 676     }
 677     rc = 0;
 678
 679 out:
 680     return rc;
 681 }
 682
 683 int nbd_trip(NBDExport *exp, int csock)
 684 {
 685     struct nbd_request request;
 686     struct nbd_reply reply;
 687     int ret;
 688
 689     TRACE("Reading request.");
 690
 691     ret = nbd_do_receive_request(csock, &request, exp->data);
 692     if (ret == -EIO) {
 693         return -1;
 694     }
 695
 696     reply.handle = request.handle;
 697     reply.error = 0;
 698
 699     if (ret < 0) {
 700         reply.error = -ret;
 701         goto error_reply;
 702     }
 703
 704     if ((request.from + request.len) > exp->size) {
 705             LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
 706             ", Offset: %" PRIu64 "\n",
 707                     request.from, request.len,
 708                     (uint64_t)exp->size, exp->dev_offset);
 709         LOG("requested operation past EOF--bad client?");
 710         goto invalid_request;
 711     }
 712
 713     switch (request.type & NBD_CMD_MASK_COMMAND) {
 714     case NBD_CMD_READ:
 715         TRACE("Request type is READ");
 716
 717         ret = bdrv_read(exp->bs, (request.from + exp->dev_offset) / 512,
 718                         exp->data, request.len / 512);
 719         if (ret < 0) {
 720             LOG("reading from file failed");
 721             reply.error = -ret;
 722             goto error_reply;
 723         }
 724
 725         TRACE("Read %u byte(s)", request.len);
 726         if (nbd_do_send_reply(csock, &reply, exp->data, request.len) < 0)
 727             return -1;
 728         break;
 729     case NBD_CMD_WRITE:
 730         TRACE("Request type is WRITE");
 731
 732         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
 733             TRACE("Server is read-only, return error");
 734             reply.error = EROFS;
 735             goto error_reply;
 736         }
 737
 738         TRACE("Writing to device");
 739
 740         ret = bdrv_write(exp->bs, (request.from + exp->dev_offset) / 512,
 741                          exp->data, request.len / 512);
 742         if (ret < 0) {
 743             LOG("writing to file failed");
 744             reply.error = -ret;
 745             goto error_reply;
 746         }
 747
 748         if (request.type & NBD_CMD_FLAG_FUA) {
 749             ret = bdrv_flush(exp->bs);
 750             if (ret < 0) {
 751                 LOG("flush failed");
 752                 reply.error = -ret;
 753                 goto error_reply;
 754             }
 755         }
 756
 757         if (nbd_do_send_reply(csock, &reply, NULL, 0) < 0)
 758             return -1;
 759         break;
 760     case NBD_CMD_DISC:
 761         TRACE("Request type is DISCONNECT");
 762         errno = 0;
 763         return 1;
 764     case NBD_CMD_FLUSH:
 765         TRACE("Request type is FLUSH");
 766
 767         ret = bdrv_flush(exp->bs);
 768         if (ret < 0) {
 769             LOG("flush failed");
 770             reply.error = -ret;
 771         }
 772
 773         if (nbd_do_send_reply(csock, &reply, NULL, 0) < 0)
 774             return -1;
 775         break;
 776     case NBD_CMD_TRIM:
 777         TRACE("Request type is TRIM");
 778         ret = bdrv_discard(exp->bs, (request.from + exp->dev_offset) / 512,
 779                            request.len / 512);
 780         if (ret < 0) {
 781             LOG("discard failed");
 782             reply.error = -ret;
 783         }
 784         if (nbd_do_send_reply(csock, &reply, NULL, 0) < 0)
 785             return -1;
 786         break;
 787     default:
 788         LOG("invalid request type (%u) received", request.type);
 789     invalid_request:
 790         reply.error = -EINVAL;
 791     error_reply:
 792         if (nbd_do_send_reply(csock, &reply, NULL, 0) == -1)
 793             return -1;
 794         break;
 795     }
 796
 797     TRACE("Request/Reply complete");
 798
 799     return 0;
 800 }
 801
 802 int nbd_negotiate(NBDExport *exp, int csock)
 803 {
 804     return nbd_send_negotiate(csock, exp->size, exp->nbdflags);
 805 }