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 "sysemu/block-backend.h"
  21 #include "block/block_int.h"
  22 #include "block/nbd.h"
  23 #include "qemu/main-loop.h"
  24 #include "qemu/sockets.h"
  25 #include "qemu/error-report.h"
  26 #include "block/snapshot.h"
  27 #include "qapi/util.h"
  28 #include "qapi/qmp/qstring.h"
  29
  30 #include <stdarg.h>
  31 #include <stdio.h>
  32 #include <getopt.h>
  33 #include <err.h>
  34 #include <sys/types.h>
  35 #include <sys/socket.h>
  36 #include <netinet/in.h>
  37 #include <netinet/tcp.h>
  38 #include <arpa/inet.h>
  39 #include <signal.h>
  40 #include <libgen.h>
  41 #include <pthread.h>
  42
  43 #define SOCKET_PATH                "/var/lock/qemu-nbd-%s"
  44 #define QEMU_NBD_OPT_CACHE         1
  45 #define QEMU_NBD_OPT_AIO           2
  46 #define QEMU_NBD_OPT_DISCARD       3
  47 #define QEMU_NBD_OPT_DETECT_ZEROES 4
  48
  49 static NBDExport *exp;
  50 static int verbose;
  51 static char *srcpath;
  52 static char *sockpath;
  53 static int persistent = 0;
  54 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
  55 static int shared = 1;
  56 static int nb_fds;
  57 static int server_fd;
  58
  59 static void usage(const char *name)
  60 {
  61     (printf) (
  62 "Usage: %s [OPTIONS] FILE\n"
  63 "QEMU Disk Network Block Device Server\n"
  64 "\n"
  65 "  -h, --help                display this help and exit\n"
  66 "  -V, --version             output version information and exit\n"
  67 "\n"
  68 "Connection properties:\n"
  69 "  -p, --port=PORT           port to listen on (default `%d')\n"
  70 "  -b, --bind=IFACE          interface to bind to (default `0.0.0.0')\n"
  71 "  -k, --socket=PATH         path to the unix socket\n"
  72 "                            (default '"SOCKET_PATH"')\n"
  73 "  -e, --shared=NUM          device can be shared by NUM clients (default '1')\n"
  74 "  -t, --persistent          don't exit on the last connection\n"
  75 "  -v, --verbose             display extra debugging information\n"
  76 "\n"
  77 "Exposing part of the image:\n"
  78 "  -o, --offset=OFFSET       offset into the image\n"
  79 "  -P, --partition=NUM       only expose partition NUM\n"
  80 "\n"
  81 #ifdef __linux__
  82 "Kernel NBD client support:\n"
  83 "  -c, --connect=DEV         connect FILE to the local NBD device DEV\n"
  84 "  -d, --disconnect          disconnect the specified device\n"
  85 "\n"
  86 #endif
  87 "\n"
  88 "Block device options:\n"
  89 "  -f, --format=FORMAT       set image format (raw, qcow2, ...)\n"
  90 "  -r, --read-only           export read-only\n"
  91 "  -s, --snapshot            use FILE as an external snapshot, create a temporary\n"
  92 "                            file with backing_file=FILE, redirect the write to\n"
  93 "                            the temporary one\n"
  94 "  -l, --load-snapshot=SNAPSHOT_PARAM\n"
  95 "                            load an internal snapshot inside FILE and export it\n"
  96 "                            as an read-only device, SNAPSHOT_PARAM format is\n"
  97 "                            'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
  98 "                            '[ID_OR_NAME]'\n"
  99 "  -n, --nocache             disable host cache\n"
 100 "      --cache=MODE          set cache mode (none, writeback, ...)\n"
 101 #ifdef CONFIG_LINUX_AIO
 102 "      --aio=MODE            set AIO mode (native or threads)\n"
 103 #endif
 104 "      --discard=MODE        set discard mode (ignore, unmap)\n"
 105 "      --detect-zeroes=MODE  set detect-zeroes mode (off, on, unmap)\n"
 106 "\n"
 107 "Report bugs to <qemu-devel@nongnu.org>\n"
 108     , name, NBD_DEFAULT_PORT, "DEVICE");
 109 }
 110
 111 static void version(const char *name)
 112 {
 113     printf(
 114 "%s version 0.0.1\n"
 115 "Written by Anthony Liguori.\n"
 116 "\n"
 117 "Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.\n"
 118 "This is free software; see the source for copying conditions.  There is NO\n"
 119 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
 120     , name);
 121 }
 122
 123 struct partition_record
 124 {
 125     uint8_t bootable;
 126     uint8_t start_head;
 127     uint32_t start_cylinder;
 128     uint8_t start_sector;
 129     uint8_t system;
 130     uint8_t end_head;
 131     uint8_t end_cylinder;
 132     uint8_t end_sector;
 133     uint32_t start_sector_abs;
 134     uint32_t nb_sectors_abs;
 135 };
 136
 137 static void read_partition(uint8_t *p, struct partition_record *r)
 138 {
 139     r->bootable = p[0];
 140     r->start_head = p[1];
 141     r->start_cylinder = p[3] | ((p[2] << 2) & 0x0300);
 142     r->start_sector = p[2] & 0x3f;
 143     r->system = p[4];
 144     r->end_head = p[5];
 145     r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
 146     r->end_sector = p[6] & 0x3f;
 147
 148     r->start_sector_abs = le32_to_cpup((uint32_t *)(p +  8));
 149     r->nb_sectors_abs   = le32_to_cpup((uint32_t *)(p + 12));
 150 }
 151
 152 static int find_partition(BlockBackend *blk, int partition,
 153                           off_t *offset, off_t *size)
 154 {
 155     struct partition_record mbr[4];
 156     uint8_t data[512];
 157     int i;
 158     int ext_partnum = 4;
 159     int ret;
 160
 161     if ((ret = blk_read(blk, 0, data, 1)) < 0) {
 162         errno = -ret;
 163         err(EXIT_FAILURE, "error while reading");
 164     }
 165
 166     if (data[510] != 0x55 || data[511] != 0xaa) {
 167         return -EINVAL;
 168     }
 169
 170     for (i = 0; i < 4; i++) {
 171         read_partition(&data[446 + 16 * i], &mbr[i]);
 172
 173         if (!mbr[i].system || !mbr[i].nb_sectors_abs) {
 174             continue;
 175         }
 176
 177         if (mbr[i].system == 0xF || mbr[i].system == 0x5) {
 178             struct partition_record ext[4];
 179             uint8_t data1[512];
 180             int j;
 181
 182             if ((ret = blk_read(blk, mbr[i].start_sector_abs, data1, 1)) < 0) {
 183                 errno = -ret;
 184                 err(EXIT_FAILURE, "error while reading");
 185             }
 186
 187             for (j = 0; j < 4; j++) {
 188                 read_partition(&data1[446 + 16 * j], &ext[j]);
 189                 if (!ext[j].system || !ext[j].nb_sectors_abs) {
 190                     continue;
 191                 }
 192
 193                 if ((ext_partnum + j + 1) == partition) {
 194                     *offset = (uint64_t)ext[j].start_sector_abs << 9;
 195                     *size = (uint64_t)ext[j].nb_sectors_abs << 9;
 196                     return 0;
 197                 }
 198             }
 199             ext_partnum += 4;
 200         } else if ((i + 1) == partition) {
 201             *offset = (uint64_t)mbr[i].start_sector_abs << 9;
 202             *size = (uint64_t)mbr[i].nb_sectors_abs << 9;
 203             return 0;
 204         }
 205     }
 206
 207     return -ENOENT;
 208 }
 209
 210 static void termsig_handler(int signum)
 211 {
 212     state = TERMINATE;
 213     qemu_notify_event();
 214 }
 215
 216 static void combine_addr(char *buf, size_t len, const char* address,
 217                          uint16_t port)
 218 {
 219     /* If the address-part contains a colon, it's an IPv6 IP so needs [] */
 220     if (strstr(address, ":")) {
 221         snprintf(buf, len, "[%s]:%u", address, port);
 222     } else {
 223         snprintf(buf, len, "%s:%u", address, port);
 224     }
 225 }
 226
 227 static int tcp_socket_incoming(const char *address, uint16_t port)
 228 {
 229     char address_and_port[128];
 230     Error *local_err = NULL;
 231
 232     combine_addr(address_and_port, 128, address, port);
 233     int fd = inet_listen(address_and_port, NULL, 0, SOCK_STREAM, 0, &local_err);
 234
 235     if (local_err != NULL) {
 236         error_report_err(local_err);
 237     }
 238     return fd;
 239 }
 240
 241 static int unix_socket_incoming(const char *path)
 242 {
 243     Error *local_err = NULL;
 244     int fd = unix_listen(path, NULL, 0, &local_err);
 245
 246     if (local_err != NULL) {
 247         error_report_err(local_err);
 248     }
 249     return fd;
 250 }
 251
 252 static int unix_socket_outgoing(const char *path)
 253 {
 254     Error *local_err = NULL;
 255     int fd = unix_connect(path, &local_err);
 256
 257     if (local_err != NULL) {
 258         error_report_err(local_err);
 259     }
 260     return fd;
 261 }
 262
 263 static void *show_parts(void *arg)
 264 {
 265     char *device = arg;
 266     int nbd;
 267
 268     /* linux just needs an open() to trigger
 269      * the partition table update
 270      * but remember to load the module with max_part != 0 :
 271      *     modprobe nbd max_part=63
 272      */
 273     nbd = open(device, O_RDWR);
 274     if (nbd >= 0) {
 275         close(nbd);
 276     }
 277     return NULL;
 278 }
 279
 280 static void *nbd_client_thread(void *arg)
 281 {
 282     char *device = arg;
 283     off_t size;
 284     uint32_t nbdflags;
 285     int fd, sock;
 286     int ret;
 287     pthread_t show_parts_thread;
 288     Error *local_error = NULL;
 289
 290     sock = unix_socket_outgoing(sockpath);
 291     if (sock < 0) {
 292         goto out;
 293     }
 294
 295     ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
 296                                 &size, &local_error);
 297     if (ret < 0) {
 298         if (local_error) {
 299             fprintf(stderr, "%s\n", error_get_pretty(local_error));
 300             error_free(local_error);
 301         }
 302         goto out_socket;
 303     }
 304
 305     fd = open(device, O_RDWR);
 306     if (fd < 0) {
 307         /* Linux-only, we can use %m in printf.  */
 308         fprintf(stderr, "Failed to open %s: %m\n", device);
 309         goto out_socket;
 310     }
 311
 312     ret = nbd_init(fd, sock, nbdflags, size);
 313     if (ret < 0) {
 314         goto out_fd;
 315     }
 316
 317     /* update partition table */
 318     pthread_create(&show_parts_thread, NULL, show_parts, device);
 319
 320     if (verbose) {
 321         fprintf(stderr, "NBD device %s is now connected to %s\n",
 322                 device, srcpath);
 323     } else {
 324         /* Close stderr so that the qemu-nbd process exits.  */
 325         dup2(STDOUT_FILENO, STDERR_FILENO);
 326     }
 327
 328     ret = nbd_client(fd);
 329     if (ret) {
 330         goto out_fd;
 331     }
 332     close(fd);
 333     kill(getpid(), SIGTERM);
 334     return (void *) EXIT_SUCCESS;
 335
 336 out_fd:
 337     close(fd);
 338 out_socket:
 339     closesocket(sock);
 340 out:
 341     kill(getpid(), SIGTERM);
 342     return (void *) EXIT_FAILURE;
 343 }
 344
 345 static int nbd_can_accept(void)
 346 {
 347     return nb_fds < shared;
 348 }
 349
 350 static void nbd_export_closed(NBDExport *exp)
 351 {
 352     assert(state == TERMINATING);
 353     state = TERMINATED;
 354 }
 355
 356 static void nbd_update_server_fd_handler(int fd);
 357
 358 static void nbd_client_closed(NBDClient *client)
 359 {
 360     nb_fds--;
 361     if (nb_fds == 0 && !persistent && state == RUNNING) {
 362         state = TERMINATE;
 363     }
 364     nbd_update_server_fd_handler(server_fd);
 365     nbd_client_put(client);
 366 }
 367
 368 static void nbd_accept(void *opaque)
 369 {
 370     struct sockaddr_in addr;
 371     socklen_t addr_len = sizeof(addr);
 372
 373     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
 374     if (fd < 0) {
 375         perror("accept");
 376         return;
 377     }
 378
 379     if (state >= TERMINATE) {
 380         close(fd);
 381         return;
 382     }
 383
 384     if (nbd_client_new(exp, fd, nbd_client_closed)) {
 385         nb_fds++;
 386         nbd_update_server_fd_handler(server_fd);
 387     } else {
 388         shutdown(fd, 2);
 389         close(fd);
 390     }
 391 }
 392
 393 static void nbd_update_server_fd_handler(int fd)
 394 {
 395     if (nbd_can_accept()) {
 396         qemu_set_fd_handler(fd, nbd_accept, NULL, (void *)(uintptr_t)fd);
 397     } else {
 398         qemu_set_fd_handler(fd, NULL, NULL, NULL);
 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     char *device = NULL;
 411     int port = NBD_DEFAULT_PORT;
 412     off_t fd_size;
 413     QemuOpts *sn_opts = NULL;
 414     const char *sn_id_or_name = NULL;
 415     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
 416     struct option lopt[] = {
 417         { "help", 0, NULL, 'h' },
 418         { "version", 0, NULL, 'V' },
 419         { "bind", 1, NULL, 'b' },
 420         { "port", 1, NULL, 'p' },
 421         { "socket", 1, NULL, 'k' },
 422         { "offset", 1, NULL, 'o' },
 423         { "read-only", 0, NULL, 'r' },
 424         { "partition", 1, NULL, 'P' },
 425         { "connect", 1, NULL, 'c' },
 426         { "disconnect", 0, NULL, 'd' },
 427         { "snapshot", 0, NULL, 's' },
 428         { "load-snapshot", 1, NULL, 'l' },
 429         { "nocache", 0, NULL, 'n' },
 430         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
 431 #ifdef CONFIG_LINUX_AIO
 432         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
 433 #endif
 434         { "discard", 1, NULL, QEMU_NBD_OPT_DISCARD },
 435         { "detect-zeroes", 1, NULL, QEMU_NBD_OPT_DETECT_ZEROES },
 436         { "shared", 1, NULL, 'e' },
 437         { "format", 1, NULL, 'f' },
 438         { "persistent", 0, NULL, 't' },
 439         { "verbose", 0, NULL, 'v' },
 440         { NULL, 0, NULL, 0 }
 441     };
 442     int ch;
 443     int opt_ind = 0;
 444     int li;
 445     char *end;
 446     int flags = BDRV_O_RDWR;
 447     int partition = -1;
 448     int ret = 0;
 449     int fd;
 450     bool seen_cache = false;
 451     bool seen_discard = false;
 452 #ifdef CONFIG_LINUX_AIO
 453     bool seen_aio = false;
 454 #endif
 455     pthread_t client_thread;
 456     const char *fmt = NULL;
 457     Error *local_err = NULL;
 458     BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
 459     QDict *options = NULL;
 460
 461     /* The client thread uses SIGTERM to interrupt the server.  A signal
 462      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
 463      */
 464     struct sigaction sa_sigterm;
 465     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
 466     sa_sigterm.sa_handler = termsig_handler;
 467     sigaction(SIGTERM, &sa_sigterm, NULL);
 468     qemu_init_exec_dir(argv[0]);
 469
 470     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
 471         switch (ch) {
 472         case 's':
 473             flags |= BDRV_O_SNAPSHOT;
 474             break;
 475         case 'n':
 476             optarg = (char *) "none";
 477             /* fallthrough */
 478         case QEMU_NBD_OPT_CACHE:
 479             if (seen_cache) {
 480                 errx(EXIT_FAILURE, "-n and --cache can only be specified once");
 481             }
 482             seen_cache = true;
 483             if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
 484                 errx(EXIT_FAILURE, "Invalid cache mode `%s'", optarg);
 485             }
 486             break;
 487 #ifdef CONFIG_LINUX_AIO
 488         case QEMU_NBD_OPT_AIO:
 489             if (seen_aio) {
 490                 errx(EXIT_FAILURE, "--aio can only be specified once");
 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                errx(EXIT_FAILURE, "invalid aio mode `%s'", optarg);
 499             }
 500             break;
 501 #endif
 502         case QEMU_NBD_OPT_DISCARD:
 503             if (seen_discard) {
 504                 errx(EXIT_FAILURE, "--discard can only be specified once");
 505             }
 506             seen_discard = true;
 507             if (bdrv_parse_discard_flags(optarg, &flags) == -1) {
 508                 errx(EXIT_FAILURE, "Invalid discard mode `%s'", optarg);
 509             }
 510             break;
 511         case QEMU_NBD_OPT_DETECT_ZEROES:
 512             detect_zeroes =
 513                 qapi_enum_parse(BlockdevDetectZeroesOptions_lookup,
 514                                 optarg,
 515                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_MAX,
 516                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
 517                                 &local_err);
 518             if (local_err) {
 519                 errx(EXIT_FAILURE, "Failed to parse detect_zeroes mode: %s",
 520                      error_get_pretty(local_err));
 521             }
 522             if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
 523                 !(flags & BDRV_O_UNMAP)) {
 524                 errx(EXIT_FAILURE, "setting detect-zeroes to unmap is not allowed "
 525                                    "without setting discard operation to unmap");
 526             }
 527             break;
 528         case 'b':
 529             bindto = optarg;
 530             break;
 531         case 'p':
 532             li = strtol(optarg, &end, 0);
 533             if (*end) {
 534                 errx(EXIT_FAILURE, "Invalid port `%s'", optarg);
 535             }
 536             if (li < 1 || li > 65535) {
 537                 errx(EXIT_FAILURE, "Port out of range `%s'", optarg);
 538             }
 539             port = (uint16_t)li;
 540             break;
 541         case 'o':
 542                 dev_offset = strtoll (optarg, &end, 0);
 543             if (*end) {
 544                 errx(EXIT_FAILURE, "Invalid offset `%s'", optarg);
 545             }
 546             if (dev_offset < 0) {
 547                 errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
 548             }
 549             break;
 550         case 'l':
 551             if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
 552                 sn_opts = qemu_opts_parse_noisily(&internal_snapshot_opts,
 553                                                   optarg, false);
 554                 if (!sn_opts) {
 555                     errx(EXIT_FAILURE, "Failed in parsing snapshot param `%s'",
 556                          optarg);
 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                 errx(EXIT_FAILURE, "Invalid partition `%s'", optarg);
 570             }
 571             if (partition < 1 || partition > 8) {
 572                 errx(EXIT_FAILURE, "Invalid partition %d", partition);
 573             }
 574             break;
 575         case 'k':
 576             sockpath = optarg;
 577             if (sockpath[0] != '/') {
 578                 errx(EXIT_FAILURE, "socket path must be absolute\n");
 579             }
 580             break;
 581         case 'd':
 582             disconnect = true;
 583             break;
 584         case 'c':
 585             device = optarg;
 586             break;
 587         case 'e':
 588             shared = strtol(optarg, &end, 0);
 589             if (*end) {
 590                 errx(EXIT_FAILURE, "Invalid shared device number '%s'", optarg);
 591             }
 592             if (shared < 1) {
 593                 errx(EXIT_FAILURE, "Shared device number must be greater than 0\n");
 594             }
 595             break;
 596         case 'f':
 597             fmt = optarg;
 598             break;
 599         case 't':
 600             persistent = 1;
 601             break;
 602         case 'v':
 603             verbose = 1;
 604             break;
 605         case 'V':
 606             version(argv[0]);
 607             exit(0);
 608             break;
 609         case 'h':
 610             usage(argv[0]);
 611             exit(0);
 612             break;
 613         case '?':
 614             errx(EXIT_FAILURE, "Try `%s --help' for more information.",
 615                  argv[0]);
 616         }
 617     }
 618
 619     if ((argc - optind) != 1) {
 620         errx(EXIT_FAILURE, "Invalid number of argument.\n"
 621              "Try `%s --help' for more information.",
 622              argv[0]);
 623     }
 624
 625     if (disconnect) {
 626         fd = open(argv[optind], O_RDWR);
 627         if (fd < 0) {
 628             err(EXIT_FAILURE, "Cannot open %s", argv[optind]);
 629         }
 630         nbd_disconnect(fd);
 631
 632         close(fd);
 633
 634         printf("%s disconnected\n", argv[optind]);
 635
 636         return 0;
 637     }
 638
 639     if (device && !verbose) {
 640         int stderr_fd[2];
 641         pid_t pid;
 642         int ret;
 643
 644         if (qemu_pipe(stderr_fd) < 0) {
 645             err(EXIT_FAILURE, "Error setting up communication pipe");
 646         }
 647
 648         /* Now daemonize, but keep a communication channel open to
 649          * print errors and exit with the proper status code.
 650          */
 651         pid = fork();
 652         if (pid < 0) {
 653             err(EXIT_FAILURE, "Failed to fork");
 654         } else if (pid == 0) {
 655             close(stderr_fd[0]);
 656             ret = qemu_daemon(1, 0);
 657
 658             /* Temporarily redirect stderr to the parent's pipe...  */
 659             dup2(stderr_fd[1], STDERR_FILENO);
 660             if (ret < 0) {
 661                 err(EXIT_FAILURE, "Failed to daemonize");
 662             }
 663
 664             /* ... close the descriptor we inherited and go on.  */
 665             close(stderr_fd[1]);
 666         } else {
 667             bool errors = false;
 668             char *buf;
 669
 670             /* In the parent.  Print error messages from the child until
 671              * it closes the pipe.
 672              */
 673             close(stderr_fd[1]);
 674             buf = g_malloc(1024);
 675             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
 676                 errors = true;
 677                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
 678                 if (ret < 0) {
 679                     exit(EXIT_FAILURE);
 680                 }
 681             }
 682             if (ret < 0) {
 683                 err(EXIT_FAILURE, "Cannot read from daemon");
 684             }
 685
 686             /* Usually the daemon should not print any message.
 687              * Exit with zero status in that case.
 688              */
 689             exit(errors);
 690         }
 691     }
 692
 693     if (device != NULL && sockpath == NULL) {
 694         sockpath = g_malloc(128);
 695         snprintf(sockpath, 128, SOCKET_PATH, basename(device));
 696     }
 697
 698     if (qemu_init_main_loop(&local_err)) {
 699         error_report_err(local_err);
 700         exit(EXIT_FAILURE);
 701     }
 702     bdrv_init();
 703     atexit(bdrv_close_all);
 704
 705     if (fmt) {
 706         options = qdict_new();
 707         qdict_put(options, "driver", qstring_from_str(fmt));
 708     }
 709
 710     srcpath = argv[optind];
 711     blk = blk_new_open("hda", srcpath, NULL, options, flags, &local_err);
 712     if (!blk) {
 713         errx(EXIT_FAILURE, "Failed to blk_new_open '%s': %s", argv[optind],
 714              error_get_pretty(local_err));
 715     }
 716     bs = blk_bs(blk);
 717
 718     if (sn_opts) {
 719         ret = bdrv_snapshot_load_tmp(bs,
 720                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
 721                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
 722                                      &local_err);
 723     } else if (sn_id_or_name) {
 724         ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
 725                                                    &local_err);
 726     }
 727     if (ret < 0) {
 728         errno = -ret;
 729         err(EXIT_FAILURE,
 730             "Failed to load snapshot: %s",
 731             error_get_pretty(local_err));
 732     }
 733
 734     bs->detect_zeroes = detect_zeroes;
 735     fd_size = blk_getlength(blk);
 736     if (fd_size < 0) {
 737         errx(EXIT_FAILURE, "Failed to determine the image length: %s",
 738              strerror(-fd_size));
 739     }
 740
 741     if (partition != -1) {
 742         ret = find_partition(blk, partition, &dev_offset, &fd_size);
 743         if (ret < 0) {
 744             errno = -ret;
 745             err(EXIT_FAILURE, "Could not find partition %d", partition);
 746         }
 747     }
 748
 749     exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed,
 750                          &local_err);
 751     if (!exp) {
 752         errx(EXIT_FAILURE, "%s", error_get_pretty(local_err));
 753     }
 754
 755     if (sockpath) {
 756         fd = unix_socket_incoming(sockpath);
 757     } else {
 758         fd = tcp_socket_incoming(bindto, port);
 759     }
 760
 761     if (fd < 0) {
 762         return 1;
 763     }
 764
 765     if (device) {
 766         int ret;
 767
 768         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
 769         if (ret != 0) {
 770             errx(EXIT_FAILURE, "Failed to create client thread: %s",
 771                  strerror(ret));
 772         }
 773     } else {
 774         /* Shut up GCC warnings.  */
 775         memset(&client_thread, 0, sizeof(client_thread));
 776     }
 777
 778     server_fd = fd;
 779     nbd_update_server_fd_handler(fd);
 780
 781     /* now when the initialization is (almost) complete, chdir("/")
 782      * to free any busy filesystems */
 783     if (chdir("/") < 0) {
 784         err(EXIT_FAILURE, "Could not chdir to root directory");
 785     }
 786
 787     state = RUNNING;
 788     do {
 789         main_loop_wait(false);
 790         if (state == TERMINATE) {
 791             state = TERMINATING;
 792             nbd_export_close(exp);
 793             nbd_export_put(exp);
 794             exp = NULL;
 795         }
 796     } while (state != TERMINATED);
 797
 798     blk_unref(blk);
 799     if (sockpath) {
 800         unlink(sockpath);
 801     }
 802
 803     qemu_opts_del(sn_opts);
 804
 805     if (device) {
 806         void *ret;
 807         pthread_join(client_thread, &ret);
 808         exit(ret != NULL);
 809     } else {
 810         exit(EXIT_SUCCESS);
 811     }
 812 }