qemu-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 "qemu/osdep.h"
  20 #include "qemu-common.h"
  21 #include "sysemu/block-backend.h"
  22 #include "block/block_int.h"
  23 #include "block/nbd.h"
  24 #include "qemu/main-loop.h"
  25 #include "qemu/error-report.h"
  26 #include "qemu/config-file.h"
  27 #include "block/snapshot.h"
  28 #include "qapi/util.h"
  29 #include "qapi/qmp/qstring.h"
  30 #include "qom/object_interfaces.h"
  31 #include "io/channel-socket.h"
  32
  33 #include <getopt.h>
  34 #include <sys/types.h>
  35 #include <signal.h>
  36 #include <libgen.h>
  37 #include <pthread.h>
  38
  39 #define SOCKET_PATH                "/var/lock/qemu-nbd-%s"
  40 #define QEMU_NBD_OPT_CACHE         1
  41 #define QEMU_NBD_OPT_AIO           2
  42 #define QEMU_NBD_OPT_DISCARD       3
  43 #define QEMU_NBD_OPT_DETECT_ZEROES 4
  44 #define QEMU_NBD_OPT_OBJECT        5
  45
  46 static NBDExport *exp;
  47 static int verbose;
  48 static char *srcpath;
  49 static SocketAddress *saddr;
  50 static int persistent = 0;
  51 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
  52 static int shared = 1;
  53 static int nb_fds;
  54 static QIOChannelSocket *server_ioc;
  55 static int server_watch = -1;
  56
  57 static void usage(const char *name)
  58 {
  59     (printf) (
  60 "Usage: %s [OPTIONS] FILE\n"
  61 "QEMU Disk Network Block Device Server\n"
  62 "\n"
  63 "  -h, --help                display this help and exit\n"
  64 "  -V, --version             output version information and exit\n"
  65 "\n"
  66 "Connection properties:\n"
  67 "  -p, --port=PORT           port to listen on (default `%d')\n"
  68 "  -b, --bind=IFACE          interface to bind to (default `0.0.0.0')\n"
  69 "  -k, --socket=PATH         path to the unix socket\n"
  70 "                            (default '"SOCKET_PATH"')\n"
  71 "  -e, --shared=NUM          device can be shared by NUM clients (default '1')\n"
  72 "  -t, --persistent          don't exit on the last connection\n"
  73 "  -v, --verbose             display extra debugging information\n"
  74 "\n"
  75 "Exposing part of the image:\n"
  76 "  -o, --offset=OFFSET       offset into the image\n"
  77 "  -P, --partition=NUM       only expose partition NUM\n"
  78 "\n"
  79 "General purpose options:\n"
  80 "  --object type,id=ID,...   define an object such as 'secret' for providing\n"
  81 "                            passwords and/or encryption keys\n"
  82 #ifdef __linux__
  83 "Kernel NBD client support:\n"
  84 "  -c, --connect=DEV         connect FILE to the local NBD device DEV\n"
  85 "  -d, --disconnect          disconnect the specified device\n"
  86 "\n"
  87 #endif
  88 "\n"
  89 "Block device options:\n"
  90 "  -f, --format=FORMAT       set image format (raw, qcow2, ...)\n"
  91 "  -r, --read-only           export read-only\n"
  92 "  -s, --snapshot            use FILE as an external snapshot, create a temporary\n"
  93 "                            file with backing_file=FILE, redirect the write to\n"
  94 "                            the temporary one\n"
  95 "  -l, --load-snapshot=SNAPSHOT_PARAM\n"
  96 "                            load an internal snapshot inside FILE and export it\n"
  97 "                            as an read-only device, SNAPSHOT_PARAM format is\n"
  98 "                            'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
  99 "                            '[ID_OR_NAME]'\n"
 100 "  -n, --nocache             disable host cache\n"
 101 "      --cache=MODE          set cache mode (none, writeback, ...)\n"
 102 "      --aio=MODE            set AIO mode (native or threads)\n"
 103 "      --discard=MODE        set discard mode (ignore, unmap)\n"
 104 "      --detect-zeroes=MODE  set detect-zeroes mode (off, on, unmap)\n"
 105 "\n"
 106 "Report bugs to <qemu-devel@nongnu.org>\n"
 107     , name, NBD_DEFAULT_PORT, "DEVICE");
 108 }
 109
 110 static void version(const char *name)
 111 {
 112     printf(
 113 "%s version 0.0.1\n"
 114 "Written by Anthony Liguori.\n"
 115 "\n"
 116 "Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.\n"
 117 "This is free software; see the source for copying conditions.  There is NO\n"
 118 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
 119     , name);
 120 }
 121
 122 struct partition_record
 123 {
 124     uint8_t bootable;
 125     uint8_t start_head;
 126     uint32_t start_cylinder;
 127     uint8_t start_sector;
 128     uint8_t system;
 129     uint8_t end_head;
 130     uint8_t end_cylinder;
 131     uint8_t end_sector;
 132     uint32_t start_sector_abs;
 133     uint32_t nb_sectors_abs;
 134 };
 135
 136 static void read_partition(uint8_t *p, struct partition_record *r)
 137 {
 138     r->bootable = p[0];
 139     r->start_head = p[1];
 140     r->start_cylinder = p[3] | ((p[2] << 2) & 0x0300);
 141     r->start_sector = p[2] & 0x3f;
 142     r->system = p[4];
 143     r->end_head = p[5];
 144     r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
 145     r->end_sector = p[6] & 0x3f;
 146
 147     r->start_sector_abs = le32_to_cpup((uint32_t *)(p +  8));
 148     r->nb_sectors_abs   = le32_to_cpup((uint32_t *)(p + 12));
 149 }
 150
 151 static int find_partition(BlockBackend *blk, int partition,
 152                           off_t *offset, off_t *size)
 153 {
 154     struct partition_record mbr[4];
 155     uint8_t data[512];
 156     int i;
 157     int ext_partnum = 4;
 158     int ret;
 159
 160     if ((ret = blk_read(blk, 0, data, 1)) < 0) {
 161         error_report("error while reading: %s", strerror(-ret));
 162         exit(EXIT_FAILURE);
 163     }
 164
 165     if (data[510] != 0x55 || data[511] != 0xaa) {
 166         return -EINVAL;
 167     }
 168
 169     for (i = 0; i < 4; i++) {
 170         read_partition(&data[446 + 16 * i], &mbr[i]);
 171
 172         if (!mbr[i].system || !mbr[i].nb_sectors_abs) {
 173             continue;
 174         }
 175
 176         if (mbr[i].system == 0xF || mbr[i].system == 0x5) {
 177             struct partition_record ext[4];
 178             uint8_t data1[512];
 179             int j;
 180
 181             if ((ret = blk_read(blk, mbr[i].start_sector_abs, data1, 1)) < 0) {
 182                 error_report("error while reading: %s", strerror(-ret));
 183                 exit(EXIT_FAILURE);
 184             }
 185
 186             for (j = 0; j < 4; j++) {
 187                 read_partition(&data1[446 + 16 * j], &ext[j]);
 188                 if (!ext[j].system || !ext[j].nb_sectors_abs) {
 189                     continue;
 190                 }
 191
 192                 if ((ext_partnum + j + 1) == partition) {
 193                     *offset = (uint64_t)ext[j].start_sector_abs << 9;
 194                     *size = (uint64_t)ext[j].nb_sectors_abs << 9;
 195                     return 0;
 196                 }
 197             }
 198             ext_partnum += 4;
 199         } else if ((i + 1) == partition) {
 200             *offset = (uint64_t)mbr[i].start_sector_abs << 9;
 201             *size = (uint64_t)mbr[i].nb_sectors_abs << 9;
 202             return 0;
 203         }
 204     }
 205
 206     return -ENOENT;
 207 }
 208
 209 static void termsig_handler(int signum)
 210 {
 211     state = TERMINATE;
 212     qemu_notify_event();
 213 }
 214
 215
 216 static void *show_parts(void *arg)
 217 {
 218     char *device = arg;
 219     int nbd;
 220
 221     /* linux just needs an open() to trigger
 222      * the partition table update
 223      * but remember to load the module with max_part != 0 :
 224      *     modprobe nbd max_part=63
 225      */
 226     nbd = open(device, O_RDWR);
 227     if (nbd >= 0) {
 228         close(nbd);
 229     }
 230     return NULL;
 231 }
 232
 233 static void *nbd_client_thread(void *arg)
 234 {
 235     char *device = arg;
 236     off_t size;
 237     uint32_t nbdflags;
 238     QIOChannelSocket *sioc;
 239     int fd;
 240     int ret;
 241     pthread_t show_parts_thread;
 242     Error *local_error = NULL;
 243
 244     sioc = qio_channel_socket_new();
 245     if (qio_channel_socket_connect_sync(sioc,
 246                                         saddr,
 247                                         &local_error) < 0) {
 248         error_report_err(local_error);
 249         goto out;
 250     }
 251
 252     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), NULL, &nbdflags,
 253                                 &size, &local_error);
 254     if (ret < 0) {
 255         if (local_error) {
 256             error_report_err(local_error);
 257         }
 258         goto out_socket;
 259     }
 260
 261     fd = open(device, O_RDWR);
 262     if (fd < 0) {
 263         /* Linux-only, we can use %m in printf.  */
 264         error_report("Failed to open %s: %m", device);
 265         goto out_socket;
 266     }
 267
 268     ret = nbd_init(fd, sioc, nbdflags, size);
 269     if (ret < 0) {
 270         goto out_fd;
 271     }
 272
 273     /* update partition table */
 274     pthread_create(&show_parts_thread, NULL, show_parts, device);
 275
 276     if (verbose) {
 277         fprintf(stderr, "NBD device %s is now connected to %s\n",
 278                 device, srcpath);
 279     } else {
 280         /* Close stderr so that the qemu-nbd process exits.  */
 281         dup2(STDOUT_FILENO, STDERR_FILENO);
 282     }
 283
 284     ret = nbd_client(fd);
 285     if (ret) {
 286         goto out_fd;
 287     }
 288     close(fd);
 289     object_unref(OBJECT(sioc));
 290     kill(getpid(), SIGTERM);
 291     return (void *) EXIT_SUCCESS;
 292
 293 out_fd:
 294     close(fd);
 295 out_socket:
 296     object_unref(OBJECT(sioc));
 297 out:
 298     kill(getpid(), SIGTERM);
 299     return (void *) EXIT_FAILURE;
 300 }
 301
 302 static int nbd_can_accept(void)
 303 {
 304     return nb_fds < shared;
 305 }
 306
 307 static void nbd_export_closed(NBDExport *exp)
 308 {
 309     assert(state == TERMINATING);
 310     state = TERMINATED;
 311 }
 312
 313 static void nbd_update_server_watch(void);
 314
 315 static void nbd_client_closed(NBDClient *client)
 316 {
 317     nb_fds--;
 318     if (nb_fds == 0 && !persistent && state == RUNNING) {
 319         state = TERMINATE;
 320     }
 321     nbd_update_server_watch();
 322     nbd_client_put(client);
 323 }
 324
 325 static gboolean nbd_accept(QIOChannel *ioc, GIOCondition cond, gpointer opaque)
 326 {
 327     QIOChannelSocket *cioc;
 328
 329     cioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc),
 330                                      NULL);
 331     if (!cioc) {
 332         return TRUE;
 333     }
 334
 335     if (state >= TERMINATE) {
 336         object_unref(OBJECT(cioc));
 337         return TRUE;
 338     }
 339
 340     nb_fds++;
 341     nbd_update_server_watch();
 342     nbd_client_new(exp, cioc, nbd_client_closed);
 343     object_unref(OBJECT(cioc));
 344
 345     return TRUE;
 346 }
 347
 348 static void nbd_update_server_watch(void)
 349 {
 350     if (nbd_can_accept()) {
 351         if (server_watch == -1) {
 352             server_watch = qio_channel_add_watch(QIO_CHANNEL(server_ioc),
 353                                                  G_IO_IN,
 354                                                  nbd_accept,
 355                                                  NULL, NULL);
 356         }
 357     } else {
 358         if (server_watch != -1) {
 359             g_source_remove(server_watch);
 360             server_watch = -1;
 361         }
 362     }
 363 }
 364
 365
 366 static SocketAddress *nbd_build_socket_address(const char *sockpath,
 367                                                const char *bindto,
 368                                                const char *port)
 369 {
 370     SocketAddress *saddr;
 371
 372     saddr = g_new0(SocketAddress, 1);
 373     if (sockpath) {
 374         saddr->type = SOCKET_ADDRESS_KIND_UNIX;
 375         saddr->u.q_unix = g_new0(UnixSocketAddress, 1);
 376         saddr->u.q_unix->path = g_strdup(sockpath);
 377     } else {
 378         saddr->type = SOCKET_ADDRESS_KIND_INET;
 379         saddr->u.inet = g_new0(InetSocketAddress, 1);
 380         saddr->u.inet->host = g_strdup(bindto);
 381         if (port) {
 382             saddr->u.inet->port = g_strdup(port);
 383         } else  {
 384             saddr->u.inet->port = g_strdup_printf("%d", NBD_DEFAULT_PORT);
 385         }
 386     }
 387
 388     return saddr;
 389 }
 390
 391
 392 static QemuOptsList qemu_object_opts = {
 393     .name = "object",
 394     .implied_opt_name = "qom-type",
 395     .head = QTAILQ_HEAD_INITIALIZER(qemu_object_opts.head),
 396     .desc = {
 397         { }
 398     },
 399 };
 400
 401
 402 int main(int argc, char **argv)
 403 {
 404     BlockBackend *blk;
 405     BlockDriverState *bs;
 406     off_t dev_offset = 0;
 407     uint32_t nbdflags = 0;
 408     bool disconnect = false;
 409     const char *bindto = "0.0.0.0";
 410     const char *port = NULL;
 411     char *sockpath = NULL;
 412     char *device = NULL;
 413     off_t fd_size;
 414     QemuOpts *sn_opts = NULL;
 415     const char *sn_id_or_name = NULL;
 416     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
 417     struct option lopt[] = {
 418         { "help", 0, NULL, 'h' },
 419         { "version", 0, NULL, 'V' },
 420         { "bind", 1, NULL, 'b' },
 421         { "port", 1, NULL, 'p' },
 422         { "socket", 1, NULL, 'k' },
 423         { "offset", 1, NULL, 'o' },
 424         { "read-only", 0, NULL, 'r' },
 425         { "partition", 1, NULL, 'P' },
 426         { "connect", 1, NULL, 'c' },
 427         { "disconnect", 0, NULL, 'd' },
 428         { "snapshot", 0, NULL, 's' },
 429         { "load-snapshot", 1, NULL, 'l' },
 430         { "nocache", 0, NULL, 'n' },
 431         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
 432         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
 433         { "discard", 1, NULL, QEMU_NBD_OPT_DISCARD },
 434         { "detect-zeroes", 1, NULL, QEMU_NBD_OPT_DETECT_ZEROES },
 435         { "shared", 1, NULL, 'e' },
 436         { "format", 1, NULL, 'f' },
 437         { "persistent", 0, NULL, 't' },
 438         { "verbose", 0, NULL, 'v' },
 439         { "object", 1, NULL, QEMU_NBD_OPT_OBJECT },
 440         { NULL, 0, NULL, 0 }
 441     };
 442     int ch;
 443     int opt_ind = 0;
 444     char *end;
 445     int flags = BDRV_O_RDWR;
 446     int partition = -1;
 447     int ret = 0;
 448     bool seen_cache = false;
 449     bool seen_discard = false;
 450     bool seen_aio = false;
 451     pthread_t client_thread;
 452     const char *fmt = NULL;
 453     Error *local_err = NULL;
 454     BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
 455     QDict *options = NULL;
 456
 457     /* The client thread uses SIGTERM to interrupt the server.  A signal
 458      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
 459      */
 460     struct sigaction sa_sigterm;
 461     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
 462     sa_sigterm.sa_handler = termsig_handler;
 463     sigaction(SIGTERM, &sa_sigterm, NULL);
 464     module_call_init(MODULE_INIT_QOM);
 465     qemu_add_opts(&qemu_object_opts);
 466     qemu_init_exec_dir(argv[0]);
 467
 468     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
 469         switch (ch) {
 470         case 's':
 471             flags |= BDRV_O_SNAPSHOT;
 472             break;
 473         case 'n':
 474             optarg = (char *) "none";
 475             /* fallthrough */
 476         case QEMU_NBD_OPT_CACHE:
 477             if (seen_cache) {
 478                 error_report("-n and --cache can only be specified once");
 479                 exit(EXIT_FAILURE);
 480             }
 481             seen_cache = true;
 482             if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
 483                 error_report("Invalid cache mode `%s'", optarg);
 484                 exit(EXIT_FAILURE);
 485             }
 486             break;
 487         case QEMU_NBD_OPT_AIO:
 488             if (seen_aio) {
 489                 error_report("--aio can only be specified once");
 490                 exit(EXIT_FAILURE);
 491             }
 492             seen_aio = true;
 493             if (!strcmp(optarg, "native")) {
 494                 flags |= BDRV_O_NATIVE_AIO;
 495             } else if (!strcmp(optarg, "threads")) {
 496                 /* this is the default */
 497             } else {
 498                error_report("invalid aio mode `%s'", optarg);
 499                exit(EXIT_FAILURE);
 500             }
 501             break;
 502         case QEMU_NBD_OPT_DISCARD:
 503             if (seen_discard) {
 504                 error_report("--discard can only be specified once");
 505                 exit(EXIT_FAILURE);
 506             }
 507             seen_discard = true;
 508             if (bdrv_parse_discard_flags(optarg, &flags) == -1) {
 509                 error_report("Invalid discard mode `%s'", optarg);
 510                 exit(EXIT_FAILURE);
 511             }
 512             break;
 513         case QEMU_NBD_OPT_DETECT_ZEROES:
 514             detect_zeroes =
 515                 qapi_enum_parse(BlockdevDetectZeroesOptions_lookup,
 516                                 optarg,
 517                                 BLOCKDEV_DETECT_ZEROES_OPTIONS__MAX,
 518                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
 519                                 &local_err);
 520             if (local_err) {
 521                 error_reportf_err(local_err,
 522                                   "Failed to parse detect_zeroes mode: ");
 523                 exit(EXIT_FAILURE);
 524             }
 525             if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
 526                 !(flags & BDRV_O_UNMAP)) {
 527                 error_report("setting detect-zeroes to unmap is not allowed "
 528                              "without setting discard operation to unmap");
 529                 exit(EXIT_FAILURE);
 530             }
 531             break;
 532         case 'b':
 533             bindto = optarg;
 534             break;
 535         case 'p':
 536             port = optarg;
 537             break;
 538         case 'o':
 539                 dev_offset = strtoll (optarg, &end, 0);
 540             if (*end) {
 541                 error_report("Invalid offset `%s'", optarg);
 542                 exit(EXIT_FAILURE);
 543             }
 544             if (dev_offset < 0) {
 545                 error_report("Offset must be positive `%s'", optarg);
 546                 exit(EXIT_FAILURE);
 547             }
 548             break;
 549         case 'l':
 550             if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
 551                 sn_opts = qemu_opts_parse_noisily(&internal_snapshot_opts,
 552                                                   optarg, false);
 553                 if (!sn_opts) {
 554                     error_report("Failed in parsing snapshot param `%s'",
 555                                  optarg);
 556                     exit(EXIT_FAILURE);
 557                 }
 558             } else {
 559                 sn_id_or_name = optarg;
 560             }
 561             /* fall through */
 562         case 'r':
 563             nbdflags |= NBD_FLAG_READ_ONLY;
 564             flags &= ~BDRV_O_RDWR;
 565             break;
 566         case 'P':
 567             partition = strtol(optarg, &end, 0);
 568             if (*end) {
 569                 error_report("Invalid partition `%s'", optarg);
 570                 exit(EXIT_FAILURE);
 571             }
 572             if (partition < 1 || partition > 8) {
 573                 error_report("Invalid partition %d", partition);
 574                 exit(EXIT_FAILURE);
 575             }
 576             break;
 577         case 'k':
 578             sockpath = optarg;
 579             if (sockpath[0] != '/') {
 580                 error_report("socket path must be absolute");
 581                 exit(EXIT_FAILURE);
 582             }
 583             break;
 584         case 'd':
 585             disconnect = true;
 586             break;
 587         case 'c':
 588             device = optarg;
 589             break;
 590         case 'e':
 591             shared = strtol(optarg, &end, 0);
 592             if (*end) {
 593                 error_report("Invalid shared device number '%s'", optarg);
 594                 exit(EXIT_FAILURE);
 595             }
 596             if (shared < 1) {
 597                 error_report("Shared device number must be greater than 0");
 598                 exit(EXIT_FAILURE);
 599             }
 600             break;
 601         case 'f':
 602             fmt = optarg;
 603             break;
 604         case 't':
 605             persistent = 1;
 606             break;
 607         case 'v':
 608             verbose = 1;
 609             break;
 610         case 'V':
 611             version(argv[0]);
 612             exit(0);
 613             break;
 614         case 'h':
 615             usage(argv[0]);
 616             exit(0);
 617             break;
 618         case '?':
 619             error_report("Try `%s --help' for more information.", argv[0]);
 620             exit(EXIT_FAILURE);
 621         case QEMU_NBD_OPT_OBJECT: {
 622             QemuOpts *opts;
 623             opts = qemu_opts_parse_noisily(&qemu_object_opts,
 624                                            optarg, true);
 625             if (!opts) {
 626                 exit(EXIT_FAILURE);
 627             }
 628         }   break;
 629         }
 630     }
 631
 632     if ((argc - optind) != 1) {
 633         error_report("Invalid number of arguments");
 634         error_printf("Try `%s --help' for more information.\n", argv[0]);
 635         exit(EXIT_FAILURE);
 636     }
 637
 638     if (qemu_opts_foreach(&qemu_object_opts,
 639                           user_creatable_add_opts_foreach,
 640                           NULL, &local_err)) {
 641         error_report_err(local_err);
 642         exit(EXIT_FAILURE);
 643     }
 644
 645     if (disconnect) {
 646         int nbdfd = open(argv[optind], O_RDWR);
 647         if (nbdfd < 0) {
 648             error_report("Cannot open %s: %s", argv[optind],
 649                          strerror(errno));
 650             exit(EXIT_FAILURE);
 651         }
 652         nbd_disconnect(nbdfd);
 653
 654         close(nbdfd);
 655
 656         printf("%s disconnected\n", argv[optind]);
 657
 658         return 0;
 659     }
 660
 661     if (device && !verbose) {
 662         int stderr_fd[2];
 663         pid_t pid;
 664         int ret;
 665
 666         if (qemu_pipe(stderr_fd) < 0) {
 667             error_report("Error setting up communication pipe: %s",
 668                          strerror(errno));
 669             exit(EXIT_FAILURE);
 670         }
 671
 672         /* Now daemonize, but keep a communication channel open to
 673          * print errors and exit with the proper status code.
 674          */
 675         pid = fork();
 676         if (pid < 0) {
 677             error_report("Failed to fork: %s", strerror(errno));
 678             exit(EXIT_FAILURE);
 679         } else if (pid == 0) {
 680             close(stderr_fd[0]);
 681             ret = qemu_daemon(1, 0);
 682
 683             /* Temporarily redirect stderr to the parent's pipe...  */
 684             dup2(stderr_fd[1], STDERR_FILENO);
 685             if (ret < 0) {
 686                 error_report("Failed to daemonize: %s", strerror(errno));
 687                 exit(EXIT_FAILURE);
 688             }
 689
 690             /* ... close the descriptor we inherited and go on.  */
 691             close(stderr_fd[1]);
 692         } else {
 693             bool errors = false;
 694             char *buf;
 695
 696             /* In the parent.  Print error messages from the child until
 697              * it closes the pipe.
 698              */
 699             close(stderr_fd[1]);
 700             buf = g_malloc(1024);
 701             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
 702                 errors = true;
 703                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
 704                 if (ret < 0) {
 705                     exit(EXIT_FAILURE);
 706                 }
 707             }
 708             if (ret < 0) {
 709                 error_report("Cannot read from daemon: %s",
 710                              strerror(errno));
 711                 exit(EXIT_FAILURE);
 712             }
 713
 714             /* Usually the daemon should not print any message.
 715              * Exit with zero status in that case.
 716              */
 717             exit(errors);
 718         }
 719     }
 720
 721     if (device != NULL && sockpath == NULL) {
 722         sockpath = g_malloc(128);
 723         snprintf(sockpath, 128, SOCKET_PATH, basename(device));
 724     }
 725
 726     saddr = nbd_build_socket_address(sockpath, bindto, port);
 727
 728     if (qemu_init_main_loop(&local_err)) {
 729         error_report_err(local_err);
 730         exit(EXIT_FAILURE);
 731     }
 732     bdrv_init();
 733     atexit(bdrv_close_all);
 734
 735     if (fmt) {
 736         options = qdict_new();
 737         qdict_put(options, "driver", qstring_from_str(fmt));
 738     }
 739
 740     srcpath = argv[optind];
 741     blk = blk_new_open("hda", srcpath, NULL, options, flags, &local_err);
 742     if (!blk) {
 743         error_reportf_err(local_err, "Failed to blk_new_open '%s': ",
 744                           argv[optind]);
 745         exit(EXIT_FAILURE);
 746     }
 747     bs = blk_bs(blk);
 748
 749     if (sn_opts) {
 750         ret = bdrv_snapshot_load_tmp(bs,
 751                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
 752                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
 753                                      &local_err);
 754     } else if (sn_id_or_name) {
 755         ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
 756                                                    &local_err);
 757     }
 758     if (ret < 0) {
 759         error_reportf_err(local_err, "Failed to load snapshot: ");
 760         exit(EXIT_FAILURE);
 761     }
 762
 763     bs->detect_zeroes = detect_zeroes;
 764     fd_size = blk_getlength(blk);
 765     if (fd_size < 0) {
 766         error_report("Failed to determine the image length: %s",
 767                      strerror(-fd_size));
 768         exit(EXIT_FAILURE);
 769     }
 770
 771     if (partition != -1) {
 772         ret = find_partition(blk, partition, &dev_offset, &fd_size);
 773         if (ret < 0) {
 774             error_report("Could not find partition %d: %s", partition,
 775                          strerror(-ret));
 776             exit(EXIT_FAILURE);
 777         }
 778     }
 779
 780     exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed,
 781                          &local_err);
 782     if (!exp) {
 783         error_report_err(local_err);
 784         exit(EXIT_FAILURE);
 785     }
 786
 787     server_ioc = qio_channel_socket_new();
 788     if (qio_channel_socket_listen_sync(server_ioc, saddr, &local_err) < 0) {
 789         object_unref(OBJECT(server_ioc));
 790         error_report_err(local_err);
 791         return 1;
 792     }
 793
 794     if (device) {
 795         int ret;
 796
 797         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
 798         if (ret != 0) {
 799             error_report("Failed to create client thread: %s", strerror(ret));
 800             exit(EXIT_FAILURE);
 801         }
 802     } else {
 803         /* Shut up GCC warnings.  */
 804         memset(&client_thread, 0, sizeof(client_thread));
 805     }
 806
 807     nbd_update_server_watch();
 808
 809     /* now when the initialization is (almost) complete, chdir("/")
 810      * to free any busy filesystems */
 811     if (chdir("/") < 0) {
 812         error_report("Could not chdir to root directory: %s",
 813                      strerror(errno));
 814         exit(EXIT_FAILURE);
 815     }
 816
 817     state = RUNNING;
 818     do {
 819         main_loop_wait(false);
 820         if (state == TERMINATE) {
 821             state = TERMINATING;
 822             nbd_export_close(exp);
 823             nbd_export_put(exp);
 824             exp = NULL;
 825         }
 826     } while (state != TERMINATED);
 827
 828     blk_unref(blk);
 829     if (sockpath) {
 830         unlink(sockpath);
 831     }
 832
 833     qemu_opts_del(sn_opts);
 834
 835     if (device) {
 836         void *ret;
 837         pthread_join(client_thread, &ret);
 838         exit(ret != NULL);
 839     } else {
 840         exit(EXIT_SUCCESS);
 841     }
 842 }