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