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-common.h"
  20 #include "block/block.h"
  21 #include "block/nbd.h"
  22 #include "qemu/main-loop.h"
  23 #include "qemu/sockets.h"
  24 #include "qemu/error-report.h"
  25 #include "block/snapshot.h"
  26
  27 #include <stdarg.h>
  28 #include <stdio.h>
  29 #include <getopt.h>
  30 #include <err.h>
  31 #include <sys/types.h>
  32 #include <sys/socket.h>
  33 #include <netinet/in.h>
  34 #include <netinet/tcp.h>
  35 #include <arpa/inet.h>
  36 #include <signal.h>
  37 #include <libgen.h>
  38 #include <pthread.h>
  39
  40 #define SOCKET_PATH          "/var/lock/qemu-nbd-%s"
  41 #define QEMU_NBD_OPT_CACHE   1
  42 #define QEMU_NBD_OPT_AIO     2
  43 #define QEMU_NBD_OPT_DISCARD 3
  44
  45 static NBDExport *exp;
  46 static int verbose;
  47 static char *srcpath;
  48 static char *sockpath;
  49 static int persistent = 0;
  50 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
  51 static int shared = 1;
  52 static int nb_fds;
  53
  54 static void usage(const char *name)
  55 {
  56     (printf) (
  57 "Usage: %s [OPTIONS] FILE\n"
  58 "QEMU Disk Network Block Device Server\n"
  59 "\n"
  60 "  -h, --help           display this help and exit\n"
  61 "  -V, --version        output version information and exit\n"
  62 "\n"
  63 "Connection properties:\n"
  64 "  -p, --port=PORT      port to listen on (default `%d')\n"
  65 "  -b, --bind=IFACE     interface to bind to (default `0.0.0.0')\n"
  66 "  -k, --socket=PATH    path to the unix socket\n"
  67 "                       (default '"SOCKET_PATH"')\n"
  68 "  -e, --shared=NUM     device can be shared by NUM clients (default '1')\n"
  69 "  -t, --persistent     don't exit on the last connection\n"
  70 "  -v, --verbose        display extra debugging information\n"
  71 "\n"
  72 "Exposing part of the image:\n"
  73 "  -o, --offset=OFFSET  offset into the image\n"
  74 "  -P, --partition=NUM  only expose partition NUM\n"
  75 "\n"
  76 #ifdef __linux__
  77 "Kernel NBD client support:\n"
  78 "  -c, --connect=DEV    connect FILE to the local NBD device DEV\n"
  79 "  -d, --disconnect     disconnect the specified device\n"
  80 "\n"
  81 #endif
  82 "\n"
  83 "Block device options:\n"
  84 "  -f, --format=FORMAT  set image format (raw, qcow2, ...)\n"
  85 "  -r, --read-only      export read-only\n"
  86 "  -s, --snapshot       use FILE as an external snapshot, create a temporary\n"
  87 "                       file with backing_file=FILE, redirect the write to\n"
  88 "                       the temporary one\n"
  89 "  -l, --load-snapshot=SNAPSHOT_PARAM\n"
  90 "                       load an internal snapshot inside FILE and export it\n"
  91 "                       as an read-only device, SNAPSHOT_PARAM format is\n"
  92 "                       'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
  93 "                       '[ID_OR_NAME]'\n"
  94 "  -n, --nocache        disable host cache\n"
  95 "      --cache=MODE     set cache mode (none, writeback, ...)\n"
  96 #ifdef CONFIG_LINUX_AIO
  97 "      --aio=MODE       set AIO mode (native or threads)\n"
  98 #endif
  99 "\n"
 100 "Report bugs to <qemu-devel@nongnu.org>\n"
 101     , name, NBD_DEFAULT_PORT, "DEVICE");
 102 }
 103
 104 static void version(const char *name)
 105 {
 106     printf(
 107 "%s version 0.0.1\n"
 108 "Written by Anthony Liguori.\n"
 109 "\n"
 110 "Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.\n"
 111 "This is free software; see the source for copying conditions.  There is NO\n"
 112 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
 113     , name);
 114 }
 115
 116 struct partition_record
 117 {
 118     uint8_t bootable;
 119     uint8_t start_head;
 120     uint32_t start_cylinder;
 121     uint8_t start_sector;
 122     uint8_t system;
 123     uint8_t end_head;
 124     uint8_t end_cylinder;
 125     uint8_t end_sector;
 126     uint32_t start_sector_abs;
 127     uint32_t nb_sectors_abs;
 128 };
 129
 130 static void read_partition(uint8_t *p, struct partition_record *r)
 131 {
 132     r->bootable = p[0];
 133     r->start_head = p[1];
 134     r->start_cylinder = p[3] | ((p[2] << 2) & 0x0300);
 135     r->start_sector = p[2] & 0x3f;
 136     r->system = p[4];
 137     r->end_head = p[5];
 138     r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
 139     r->end_sector = p[6] & 0x3f;
 140     r->start_sector_abs = p[8] | p[9] << 8 | p[10] << 16 | p[11] << 24;
 141     r->nb_sectors_abs = p[12] | p[13] << 8 | p[14] << 16 | p[15] << 24;
 142 }
 143
 144 static int find_partition(BlockDriverState *bs, int partition,
 145                           off_t *offset, off_t *size)
 146 {
 147     struct partition_record mbr[4];
 148     uint8_t data[512];
 149     int i;
 150     int ext_partnum = 4;
 151     int ret;
 152
 153     if ((ret = bdrv_read(bs, 0, data, 1)) < 0) {
 154         errno = -ret;
 155         err(EXIT_FAILURE, "error while reading");
 156     }
 157
 158     if (data[510] != 0x55 || data[511] != 0xaa) {
 159         return -EINVAL;
 160     }
 161
 162     for (i = 0; i < 4; i++) {
 163         read_partition(&data[446 + 16 * i], &mbr[i]);
 164
 165         if (!mbr[i].nb_sectors_abs)
 166             continue;
 167
 168         if (mbr[i].system == 0xF || mbr[i].system == 0x5) {
 169             struct partition_record ext[4];
 170             uint8_t data1[512];
 171             int j;
 172
 173             if ((ret = bdrv_read(bs, mbr[i].start_sector_abs, data1, 1)) < 0) {
 174                 errno = -ret;
 175                 err(EXIT_FAILURE, "error while reading");
 176             }
 177
 178             for (j = 0; j < 4; j++) {
 179                 read_partition(&data1[446 + 16 * j], &ext[j]);
 180                 if (!ext[j].nb_sectors_abs)
 181                     continue;
 182
 183                 if ((ext_partnum + j + 1) == partition) {
 184                     *offset = (uint64_t)ext[j].start_sector_abs << 9;
 185                     *size = (uint64_t)ext[j].nb_sectors_abs << 9;
 186                     return 0;
 187                 }
 188             }
 189             ext_partnum += 4;
 190         } else if ((i + 1) == partition) {
 191             *offset = (uint64_t)mbr[i].start_sector_abs << 9;
 192             *size = (uint64_t)mbr[i].nb_sectors_abs << 9;
 193             return 0;
 194         }
 195     }
 196
 197     return -ENOENT;
 198 }
 199
 200 static void termsig_handler(int signum)
 201 {
 202     state = TERMINATE;
 203     qemu_notify_event();
 204 }
 205
 206 static void combine_addr(char *buf, size_t len, const char* address,
 207                          uint16_t port)
 208 {
 209     /* If the address-part contains a colon, it's an IPv6 IP so needs [] */
 210     if (strstr(address, ":")) {
 211         snprintf(buf, len, "[%s]:%u", address, port);
 212     } else {
 213         snprintf(buf, len, "%s:%u", address, port);
 214     }
 215 }
 216
 217 static int tcp_socket_incoming(const char *address, uint16_t port)
 218 {
 219     char address_and_port[128];
 220     Error *local_err = NULL;
 221
 222     combine_addr(address_and_port, 128, address, port);
 223     int fd = inet_listen(address_and_port, NULL, 0, SOCK_STREAM, 0, &local_err);
 224
 225     if (local_err != NULL) {
 226         error_report("%s", error_get_pretty(local_err));
 227         error_free(local_err);
 228     }
 229     return fd;
 230 }
 231
 232 static int unix_socket_incoming(const char *path)
 233 {
 234     Error *local_err = NULL;
 235     int fd = unix_listen(path, NULL, 0, &local_err);
 236
 237     if (local_err != NULL) {
 238         error_report("%s", error_get_pretty(local_err));
 239         error_free(local_err);
 240     }
 241     return fd;
 242 }
 243
 244 static int unix_socket_outgoing(const char *path)
 245 {
 246     Error *local_err = NULL;
 247     int fd = unix_connect(path, &local_err);
 248
 249     if (local_err != NULL) {
 250         error_report("%s", error_get_pretty(local_err));
 251         error_free(local_err);
 252     }
 253     return fd;
 254 }
 255
 256 static void *show_parts(void *arg)
 257 {
 258     char *device = arg;
 259     int nbd;
 260
 261     /* linux just needs an open() to trigger
 262      * the partition table update
 263      * but remember to load the module with max_part != 0 :
 264      *     modprobe nbd max_part=63
 265      */
 266     nbd = open(device, O_RDWR);
 267     if (nbd >= 0) {
 268         close(nbd);
 269     }
 270     return NULL;
 271 }
 272
 273 static void *nbd_client_thread(void *arg)
 274 {
 275     char *device = arg;
 276     off_t size;
 277     size_t blocksize;
 278     uint32_t nbdflags;
 279     int fd, sock;
 280     int ret;
 281     pthread_t show_parts_thread;
 282
 283     sock = unix_socket_outgoing(sockpath);
 284     if (sock < 0) {
 285         goto out;
 286     }
 287
 288     ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
 289                                 &size, &blocksize);
 290     if (ret < 0) {
 291         goto out_socket;
 292     }
 293
 294     fd = open(device, O_RDWR);
 295     if (fd < 0) {
 296         /* Linux-only, we can use %m in printf.  */
 297         fprintf(stderr, "Failed to open %s: %m\n", device);
 298         goto out_socket;
 299     }
 300
 301     ret = nbd_init(fd, sock, nbdflags, size, blocksize);
 302     if (ret < 0) {
 303         goto out_fd;
 304     }
 305
 306     /* update partition table */
 307     pthread_create(&show_parts_thread, NULL, show_parts, device);
 308
 309     if (verbose) {
 310         fprintf(stderr, "NBD device %s is now connected to %s\n",
 311                 device, srcpath);
 312     } else {
 313         /* Close stderr so that the qemu-nbd process exits.  */
 314         dup2(STDOUT_FILENO, STDERR_FILENO);
 315     }
 316
 317     ret = nbd_client(fd);
 318     if (ret) {
 319         goto out_fd;
 320     }
 321     close(fd);
 322     kill(getpid(), SIGTERM);
 323     return (void *) EXIT_SUCCESS;
 324
 325 out_fd:
 326     close(fd);
 327 out_socket:
 328     closesocket(sock);
 329 out:
 330     kill(getpid(), SIGTERM);
 331     return (void *) EXIT_FAILURE;
 332 }
 333
 334 static int nbd_can_accept(void *opaque)
 335 {
 336     return nb_fds < shared;
 337 }
 338
 339 static void nbd_export_closed(NBDExport *exp)
 340 {
 341     assert(state == TERMINATING);
 342     state = TERMINATED;
 343 }
 344
 345 static void nbd_client_closed(NBDClient *client)
 346 {
 347     nb_fds--;
 348     if (nb_fds == 0 && !persistent && state == RUNNING) {
 349         state = TERMINATE;
 350     }
 351     qemu_notify_event();
 352     nbd_client_put(client);
 353 }
 354
 355 static void nbd_accept(void *opaque)
 356 {
 357     int server_fd = (uintptr_t) opaque;
 358     struct sockaddr_in addr;
 359     socklen_t addr_len = sizeof(addr);
 360
 361     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
 362     if (fd < 0) {
 363         perror("accept");
 364         return;
 365     }
 366
 367     if (state >= TERMINATE) {
 368         close(fd);
 369         return;
 370     }
 371
 372     if (nbd_client_new(exp, fd, nbd_client_closed)) {
 373         nb_fds++;
 374     } else {
 375         shutdown(fd, 2);
 376         close(fd);
 377     }
 378 }
 379
 380 int main(int argc, char **argv)
 381 {
 382     BlockDriverState *bs;
 383     BlockDriver *drv;
 384     off_t dev_offset = 0;
 385     uint32_t nbdflags = 0;
 386     bool disconnect = false;
 387     const char *bindto = "0.0.0.0";
 388     char *device = NULL;
 389     int port = NBD_DEFAULT_PORT;
 390     off_t fd_size;
 391     QemuOpts *sn_opts = NULL;
 392     const char *sn_id_or_name = NULL;
 393     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
 394     struct option lopt[] = {
 395         { "help", 0, NULL, 'h' },
 396         { "version", 0, NULL, 'V' },
 397         { "bind", 1, NULL, 'b' },
 398         { "port", 1, NULL, 'p' },
 399         { "socket", 1, NULL, 'k' },
 400         { "offset", 1, NULL, 'o' },
 401         { "read-only", 0, NULL, 'r' },
 402         { "partition", 1, NULL, 'P' },
 403         { "connect", 1, NULL, 'c' },
 404         { "disconnect", 0, NULL, 'd' },
 405         { "snapshot", 0, NULL, 's' },
 406         { "load-snapshot", 1, NULL, 'l' },
 407         { "nocache", 0, NULL, 'n' },
 408         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
 409 #ifdef CONFIG_LINUX_AIO
 410         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
 411 #endif
 412         { "discard", 1, NULL, QEMU_NBD_OPT_DISCARD },
 413         { "shared", 1, NULL, 'e' },
 414         { "format", 1, NULL, 'f' },
 415         { "persistent", 0, NULL, 't' },
 416         { "verbose", 0, NULL, 'v' },
 417         { NULL, 0, NULL, 0 }
 418     };
 419     int ch;
 420     int opt_ind = 0;
 421     int li;
 422     char *end;
 423     int flags = BDRV_O_RDWR;
 424     int partition = -1;
 425     int ret;
 426     int fd;
 427     bool seen_cache = false;
 428     bool seen_discard = false;
 429 #ifdef CONFIG_LINUX_AIO
 430     bool seen_aio = false;
 431 #endif
 432     pthread_t client_thread;
 433     const char *fmt = NULL;
 434     Error *local_err = NULL;
 435
 436     /* The client thread uses SIGTERM to interrupt the server.  A signal
 437      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
 438      */
 439     struct sigaction sa_sigterm;
 440     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
 441     sa_sigterm.sa_handler = termsig_handler;
 442     sigaction(SIGTERM, &sa_sigterm, NULL);
 443     qemu_init_exec_dir(argv[0]);
 444
 445     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
 446         switch (ch) {
 447         case 's':
 448             flags |= BDRV_O_SNAPSHOT;
 449             break;
 450         case 'n':
 451             optarg = (char *) "none";
 452             /* fallthrough */
 453         case QEMU_NBD_OPT_CACHE:
 454             if (seen_cache) {
 455                 errx(EXIT_FAILURE, "-n and --cache can only be specified once");
 456             }
 457             seen_cache = true;
 458             if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
 459                 errx(EXIT_FAILURE, "Invalid cache mode `%s'", optarg);
 460             }
 461             break;
 462 #ifdef CONFIG_LINUX_AIO
 463         case QEMU_NBD_OPT_AIO:
 464             if (seen_aio) {
 465                 errx(EXIT_FAILURE, "--aio can only be specified once");
 466             }
 467             seen_aio = true;
 468             if (!strcmp(optarg, "native")) {
 469                 flags |= BDRV_O_NATIVE_AIO;
 470             } else if (!strcmp(optarg, "threads")) {
 471                 /* this is the default */
 472             } else {
 473                errx(EXIT_FAILURE, "invalid aio mode `%s'", optarg);
 474             }
 475             break;
 476 #endif
 477         case QEMU_NBD_OPT_DISCARD:
 478             if (seen_discard) {
 479                 errx(EXIT_FAILURE, "--discard can only be specified once");
 480             }
 481             seen_discard = true;
 482             if (bdrv_parse_discard_flags(optarg, &flags) == -1) {
 483                 errx(EXIT_FAILURE, "Invalid discard mode `%s'", optarg);
 484             }
 485             break;
 486         case 'b':
 487             bindto = optarg;
 488             break;
 489         case 'p':
 490             li = strtol(optarg, &end, 0);
 491             if (*end) {
 492                 errx(EXIT_FAILURE, "Invalid port `%s'", optarg);
 493             }
 494             if (li < 1 || li > 65535) {
 495                 errx(EXIT_FAILURE, "Port out of range `%s'", optarg);
 496             }
 497             port = (uint16_t)li;
 498             break;
 499         case 'o':
 500                 dev_offset = strtoll (optarg, &end, 0);
 501             if (*end) {
 502                 errx(EXIT_FAILURE, "Invalid offset `%s'", optarg);
 503             }
 504             if (dev_offset < 0) {
 505                 errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
 506             }
 507             break;
 508         case 'l':
 509             if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
 510                 sn_opts = qemu_opts_parse(&internal_snapshot_opts, optarg, 0);
 511                 if (!sn_opts) {
 512                     errx(EXIT_FAILURE, "Failed in parsing snapshot param `%s'",
 513                          optarg);
 514                 }
 515             } else {
 516                 sn_id_or_name = optarg;
 517             }
 518             /* fall through */
 519         case 'r':
 520             nbdflags |= NBD_FLAG_READ_ONLY;
 521             flags &= ~BDRV_O_RDWR;
 522             break;
 523         case 'P':
 524             partition = strtol(optarg, &end, 0);
 525             if (*end)
 526                 errx(EXIT_FAILURE, "Invalid partition `%s'", optarg);
 527             if (partition < 1 || partition > 8)
 528                 errx(EXIT_FAILURE, "Invalid partition %d", partition);
 529             break;
 530         case 'k':
 531             sockpath = optarg;
 532             if (sockpath[0] != '/')
 533                 errx(EXIT_FAILURE, "socket path must be absolute\n");
 534             break;
 535         case 'd':
 536             disconnect = true;
 537             break;
 538         case 'c':
 539             device = optarg;
 540             break;
 541         case 'e':
 542             shared = strtol(optarg, &end, 0);
 543             if (*end) {
 544                 errx(EXIT_FAILURE, "Invalid shared device number '%s'", optarg);
 545             }
 546             if (shared < 1) {
 547                 errx(EXIT_FAILURE, "Shared device number must be greater than 0\n");
 548             }
 549             break;
 550         case 'f':
 551             fmt = optarg;
 552             break;
 553         case 't':
 554             persistent = 1;
 555             break;
 556         case 'v':
 557             verbose = 1;
 558             break;
 559         case 'V':
 560             version(argv[0]);
 561             exit(0);
 562             break;
 563         case 'h':
 564             usage(argv[0]);
 565             exit(0);
 566             break;
 567         case '?':
 568             errx(EXIT_FAILURE, "Try `%s --help' for more information.",
 569                  argv[0]);
 570         }
 571     }
 572
 573     if ((argc - optind) != 1) {
 574         errx(EXIT_FAILURE, "Invalid number of argument.\n"
 575              "Try `%s --help' for more information.",
 576              argv[0]);
 577     }
 578
 579     if (disconnect) {
 580         fd = open(argv[optind], O_RDWR);
 581         if (fd < 0) {
 582             err(EXIT_FAILURE, "Cannot open %s", argv[optind]);
 583         }
 584         nbd_disconnect(fd);
 585
 586         close(fd);
 587
 588         printf("%s disconnected\n", argv[optind]);
 589
 590         return 0;
 591     }
 592
 593     if (device && !verbose) {
 594         int stderr_fd[2];
 595         pid_t pid;
 596         int ret;
 597
 598         if (qemu_pipe(stderr_fd) < 0) {
 599             err(EXIT_FAILURE, "Error setting up communication pipe");
 600         }
 601
 602         /* Now daemonize, but keep a communication channel open to
 603          * print errors and exit with the proper status code.
 604          */
 605         pid = fork();
 606         if (pid == 0) {
 607             close(stderr_fd[0]);
 608             ret = qemu_daemon(1, 0);
 609
 610             /* Temporarily redirect stderr to the parent's pipe...  */
 611             dup2(stderr_fd[1], STDERR_FILENO);
 612             if (ret < 0) {
 613                 err(EXIT_FAILURE, "Failed to daemonize");
 614             }
 615
 616             /* ... close the descriptor we inherited and go on.  */
 617             close(stderr_fd[1]);
 618         } else {
 619             bool errors = false;
 620             char *buf;
 621
 622             /* In the parent.  Print error messages from the child until
 623              * it closes the pipe.
 624              */
 625             close(stderr_fd[1]);
 626             buf = g_malloc(1024);
 627             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
 628                 errors = true;
 629                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
 630                 if (ret < 0) {
 631                     exit(EXIT_FAILURE);
 632                 }
 633             }
 634             if (ret < 0) {
 635                 err(EXIT_FAILURE, "Cannot read from daemon");
 636             }
 637
 638             /* Usually the daemon should not print any message.
 639              * Exit with zero status in that case.
 640              */
 641             exit(errors);
 642         }
 643     }
 644
 645     if (device != NULL && sockpath == NULL) {
 646         sockpath = g_malloc(128);
 647         snprintf(sockpath, 128, SOCKET_PATH, basename(device));
 648     }
 649
 650     qemu_init_main_loop();
 651     bdrv_init();
 652     atexit(bdrv_close_all);
 653
 654     if (fmt) {
 655         drv = bdrv_find_format(fmt);
 656         if (!drv) {
 657             errx(EXIT_FAILURE, "Unknown file format '%s'", fmt);
 658         }
 659     } else {
 660         drv = NULL;
 661     }
 662
 663     bs = bdrv_new("hda", &error_abort);
 664
 665     srcpath = argv[optind];
 666     ret = bdrv_open(&bs, srcpath, NULL, NULL, flags, drv, &local_err);
 667     if (ret < 0) {
 668         errno = -ret;
 669         err(EXIT_FAILURE, "Failed to bdrv_open '%s': %s", argv[optind],
 670             error_get_pretty(local_err));
 671     }
 672
 673     if (sn_opts) {
 674         ret = bdrv_snapshot_load_tmp(bs,
 675                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
 676                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
 677                                      &local_err);
 678     } else if (sn_id_or_name) {
 679         ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
 680                                                    &local_err);
 681     }
 682     if (ret < 0) {
 683         errno = -ret;
 684         err(EXIT_FAILURE,
 685             "Failed to load snapshot: %s",
 686             error_get_pretty(local_err));
 687     }
 688
 689     fd_size = bdrv_getlength(bs);
 690
 691     if (partition != -1) {
 692         ret = find_partition(bs, partition, &dev_offset, &fd_size);
 693         if (ret < 0) {
 694             errno = -ret;
 695             err(EXIT_FAILURE, "Could not find partition %d", partition);
 696         }
 697     }
 698
 699     exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed);
 700
 701     if (sockpath) {
 702         fd = unix_socket_incoming(sockpath);
 703     } else {
 704         fd = tcp_socket_incoming(bindto, port);
 705     }
 706
 707     if (fd < 0) {
 708         return 1;
 709     }
 710
 711     if (device) {
 712         int ret;
 713
 714         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
 715         if (ret != 0) {
 716             errx(EXIT_FAILURE, "Failed to create client thread: %s",
 717                  strerror(ret));
 718         }
 719     } else {
 720         /* Shut up GCC warnings.  */
 721         memset(&client_thread, 0, sizeof(client_thread));
 722     }
 723
 724     qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
 725                          (void *)(uintptr_t)fd);
 726
 727     /* now when the initialization is (almost) complete, chdir("/")
 728      * to free any busy filesystems */
 729     if (chdir("/") < 0) {
 730         err(EXIT_FAILURE, "Could not chdir to root directory");
 731     }
 732
 733     state = RUNNING;
 734     do {
 735         main_loop_wait(false);
 736         if (state == TERMINATE) {
 737             state = TERMINATING;
 738             nbd_export_close(exp);
 739             nbd_export_put(exp);
 740             exp = NULL;
 741         }
 742     } while (state != TERMINATED);
 743
 744     bdrv_close(bs);
 745     if (sockpath) {
 746         unlink(sockpath);
 747     }
 748
 749     if (sn_opts) {
 750         qemu_opts_del(sn_opts);
 751     }
 752
 753     if (device) {
 754         void *ret;
 755         pthread_join(client_thread, &ret);
 756         exit(ret != NULL);
 757     } else {
 758         exit(EXIT_SUCCESS);
 759     }
 760 }