xref: /openbmc/qemu/qemu-nbd.c (revision 953ea14d)
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 
29 #include <stdarg.h>
30 #include <stdio.h>
31 #include <getopt.h>
32 #include <err.h>
33 #include <sys/types.h>
34 #include <sys/socket.h>
35 #include <netinet/in.h>
36 #include <netinet/tcp.h>
37 #include <arpa/inet.h>
38 #include <signal.h>
39 #include <libgen.h>
40 #include <pthread.h>
41 
42 #define SOCKET_PATH                "/var/lock/qemu-nbd-%s"
43 #define QEMU_NBD_OPT_CACHE         1
44 #define QEMU_NBD_OPT_AIO           2
45 #define QEMU_NBD_OPT_DISCARD       3
46 #define QEMU_NBD_OPT_DETECT_ZEROES 4
47 
48 static NBDExport *exp;
49 static int verbose;
50 static char *srcpath;
51 static char *sockpath;
52 static int persistent = 0;
53 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
54 static int shared = 1;
55 static int nb_fds;
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 #ifdef __linux__
80 "Kernel NBD client support:\n"
81 "  -c, --connect=DEV         connect FILE to the local NBD device DEV\n"
82 "  -d, --disconnect          disconnect the specified device\n"
83 "\n"
84 #endif
85 "\n"
86 "Block device options:\n"
87 "  -f, --format=FORMAT       set image format (raw, qcow2, ...)\n"
88 "  -r, --read-only           export read-only\n"
89 "  -s, --snapshot            use FILE as an external snapshot, create a temporary\n"
90 "                            file with backing_file=FILE, redirect the write to\n"
91 "                            the temporary one\n"
92 "  -l, --load-snapshot=SNAPSHOT_PARAM\n"
93 "                            load an internal snapshot inside FILE and export it\n"
94 "                            as an read-only device, SNAPSHOT_PARAM format is\n"
95 "                            'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
96 "                            '[ID_OR_NAME]'\n"
97 "  -n, --nocache             disable host cache\n"
98 "      --cache=MODE          set cache mode (none, writeback, ...)\n"
99 #ifdef CONFIG_LINUX_AIO
100 "      --aio=MODE            set AIO mode (native or threads)\n"
101 #endif
102 "      --discard=MODE        set discard mode (ignore, unmap)\n"
103 "      --detect-zeroes=MODE  set detect-zeroes mode (off, on, discard)\n"
104 "\n"
105 "Report bugs to <qemu-devel@nongnu.org>\n"
106     , name, NBD_DEFAULT_PORT, "DEVICE");
107 }
108 
109 static void version(const char *name)
110 {
111     printf(
112 "%s version 0.0.1\n"
113 "Written by Anthony Liguori.\n"
114 "\n"
115 "Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.\n"
116 "This is free software; see the source for copying conditions.  There is NO\n"
117 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
118     , name);
119 }
120 
121 struct partition_record
122 {
123     uint8_t bootable;
124     uint8_t start_head;
125     uint32_t start_cylinder;
126     uint8_t start_sector;
127     uint8_t system;
128     uint8_t end_head;
129     uint8_t end_cylinder;
130     uint8_t end_sector;
131     uint32_t start_sector_abs;
132     uint32_t nb_sectors_abs;
133 };
134 
135 static void read_partition(uint8_t *p, struct partition_record *r)
136 {
137     r->bootable = p[0];
138     r->start_head = p[1];
139     r->start_cylinder = p[3] | ((p[2] << 2) & 0x0300);
140     r->start_sector = p[2] & 0x3f;
141     r->system = p[4];
142     r->end_head = p[5];
143     r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
144     r->end_sector = p[6] & 0x3f;
145     r->start_sector_abs = p[8] | p[9] << 8 | p[10] << 16 | p[11] << 24;
146     r->nb_sectors_abs = p[12] | p[13] << 8 | p[14] << 16 | p[15] << 24;
147 }
148 
149 static int find_partition(BlockDriverState *bs, int partition,
150                           off_t *offset, off_t *size)
151 {
152     struct partition_record mbr[4];
153     uint8_t data[512];
154     int i;
155     int ext_partnum = 4;
156     int ret;
157 
158     if ((ret = bdrv_read(bs, 0, data, 1)) < 0) {
159         errno = -ret;
160         err(EXIT_FAILURE, "error while reading");
161     }
162 
163     if (data[510] != 0x55 || data[511] != 0xaa) {
164         return -EINVAL;
165     }
166 
167     for (i = 0; i < 4; i++) {
168         read_partition(&data[446 + 16 * i], &mbr[i]);
169 
170         if (!mbr[i].nb_sectors_abs)
171             continue;
172 
173         if (mbr[i].system == 0xF || mbr[i].system == 0x5) {
174             struct partition_record ext[4];
175             uint8_t data1[512];
176             int j;
177 
178             if ((ret = bdrv_read(bs, mbr[i].start_sector_abs, data1, 1)) < 0) {
179                 errno = -ret;
180                 err(EXIT_FAILURE, "error while reading");
181             }
182 
183             for (j = 0; j < 4; j++) {
184                 read_partition(&data1[446 + 16 * j], &ext[j]);
185                 if (!ext[j].nb_sectors_abs)
186                     continue;
187 
188                 if ((ext_partnum + j + 1) == partition) {
189                     *offset = (uint64_t)ext[j].start_sector_abs << 9;
190                     *size = (uint64_t)ext[j].nb_sectors_abs << 9;
191                     return 0;
192                 }
193             }
194             ext_partnum += 4;
195         } else if ((i + 1) == partition) {
196             *offset = (uint64_t)mbr[i].start_sector_abs << 9;
197             *size = (uint64_t)mbr[i].nb_sectors_abs << 9;
198             return 0;
199         }
200     }
201 
202     return -ENOENT;
203 }
204 
205 static void termsig_handler(int signum)
206 {
207     state = TERMINATE;
208     qemu_notify_event();
209 }
210 
211 static void combine_addr(char *buf, size_t len, const char* address,
212                          uint16_t port)
213 {
214     /* If the address-part contains a colon, it's an IPv6 IP so needs [] */
215     if (strstr(address, ":")) {
216         snprintf(buf, len, "[%s]:%u", address, port);
217     } else {
218         snprintf(buf, len, "%s:%u", address, port);
219     }
220 }
221 
222 static int tcp_socket_incoming(const char *address, uint16_t port)
223 {
224     char address_and_port[128];
225     Error *local_err = NULL;
226 
227     combine_addr(address_and_port, 128, address, port);
228     int fd = inet_listen(address_and_port, NULL, 0, SOCK_STREAM, 0, &local_err);
229 
230     if (local_err != NULL) {
231         error_report("%s", error_get_pretty(local_err));
232         error_free(local_err);
233     }
234     return fd;
235 }
236 
237 static int unix_socket_incoming(const char *path)
238 {
239     Error *local_err = NULL;
240     int fd = unix_listen(path, NULL, 0, &local_err);
241 
242     if (local_err != NULL) {
243         error_report("%s", error_get_pretty(local_err));
244         error_free(local_err);
245     }
246     return fd;
247 }
248 
249 static int unix_socket_outgoing(const char *path)
250 {
251     Error *local_err = NULL;
252     int fd = unix_connect(path, &local_err);
253 
254     if (local_err != NULL) {
255         error_report("%s", error_get_pretty(local_err));
256         error_free(local_err);
257     }
258     return fd;
259 }
260 
261 static void *show_parts(void *arg)
262 {
263     char *device = arg;
264     int nbd;
265 
266     /* linux just needs an open() to trigger
267      * the partition table update
268      * but remember to load the module with max_part != 0 :
269      *     modprobe nbd max_part=63
270      */
271     nbd = open(device, O_RDWR);
272     if (nbd >= 0) {
273         close(nbd);
274     }
275     return NULL;
276 }
277 
278 static void *nbd_client_thread(void *arg)
279 {
280     char *device = arg;
281     off_t size;
282     size_t blocksize;
283     uint32_t nbdflags;
284     int fd, sock;
285     int ret;
286     pthread_t show_parts_thread;
287 
288     sock = unix_socket_outgoing(sockpath);
289     if (sock < 0) {
290         goto out;
291     }
292 
293     ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
294                                 &size, &blocksize);
295     if (ret < 0) {
296         goto out_socket;
297     }
298 
299     fd = open(device, O_RDWR);
300     if (fd < 0) {
301         /* Linux-only, we can use %m in printf.  */
302         fprintf(stderr, "Failed to open %s: %m\n", device);
303         goto out_socket;
304     }
305 
306     ret = nbd_init(fd, sock, nbdflags, size, blocksize);
307     if (ret < 0) {
308         goto out_fd;
309     }
310 
311     /* update partition table */
312     pthread_create(&show_parts_thread, NULL, show_parts, device);
313 
314     if (verbose) {
315         fprintf(stderr, "NBD device %s is now connected to %s\n",
316                 device, srcpath);
317     } else {
318         /* Close stderr so that the qemu-nbd process exits.  */
319         dup2(STDOUT_FILENO, STDERR_FILENO);
320     }
321 
322     ret = nbd_client(fd);
323     if (ret) {
324         goto out_fd;
325     }
326     close(fd);
327     kill(getpid(), SIGTERM);
328     return (void *) EXIT_SUCCESS;
329 
330 out_fd:
331     close(fd);
332 out_socket:
333     closesocket(sock);
334 out:
335     kill(getpid(), SIGTERM);
336     return (void *) EXIT_FAILURE;
337 }
338 
339 static int nbd_can_accept(void *opaque)
340 {
341     return nb_fds < shared;
342 }
343 
344 static void nbd_export_closed(NBDExport *exp)
345 {
346     assert(state == TERMINATING);
347     state = TERMINATED;
348 }
349 
350 static void nbd_client_closed(NBDClient *client)
351 {
352     nb_fds--;
353     if (nb_fds == 0 && !persistent && state == RUNNING) {
354         state = TERMINATE;
355     }
356     qemu_notify_event();
357     nbd_client_put(client);
358 }
359 
360 static void nbd_accept(void *opaque)
361 {
362     int server_fd = (uintptr_t) opaque;
363     struct sockaddr_in addr;
364     socklen_t addr_len = sizeof(addr);
365 
366     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
367     if (fd < 0) {
368         perror("accept");
369         return;
370     }
371 
372     if (state >= TERMINATE) {
373         close(fd);
374         return;
375     }
376 
377     if (nbd_client_new(exp, fd, nbd_client_closed)) {
378         nb_fds++;
379     } else {
380         shutdown(fd, 2);
381         close(fd);
382     }
383 }
384 
385 int main(int argc, char **argv)
386 {
387     BlockBackend *blk;
388     BlockDriverState *bs;
389     BlockDriver *drv;
390     off_t dev_offset = 0;
391     uint32_t nbdflags = 0;
392     bool disconnect = false;
393     const char *bindto = "0.0.0.0";
394     char *device = NULL;
395     int port = NBD_DEFAULT_PORT;
396     off_t fd_size;
397     QemuOpts *sn_opts = NULL;
398     const char *sn_id_or_name = NULL;
399     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
400     struct option lopt[] = {
401         { "help", 0, NULL, 'h' },
402         { "version", 0, NULL, 'V' },
403         { "bind", 1, NULL, 'b' },
404         { "port", 1, NULL, 'p' },
405         { "socket", 1, NULL, 'k' },
406         { "offset", 1, NULL, 'o' },
407         { "read-only", 0, NULL, 'r' },
408         { "partition", 1, NULL, 'P' },
409         { "connect", 1, NULL, 'c' },
410         { "disconnect", 0, NULL, 'd' },
411         { "snapshot", 0, NULL, 's' },
412         { "load-snapshot", 1, NULL, 'l' },
413         { "nocache", 0, NULL, 'n' },
414         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
415 #ifdef CONFIG_LINUX_AIO
416         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
417 #endif
418         { "discard", 1, NULL, QEMU_NBD_OPT_DISCARD },
419         { "detect-zeroes", 1, NULL, QEMU_NBD_OPT_DETECT_ZEROES },
420         { "shared", 1, NULL, 'e' },
421         { "format", 1, NULL, 'f' },
422         { "persistent", 0, NULL, 't' },
423         { "verbose", 0, NULL, 'v' },
424         { NULL, 0, NULL, 0 }
425     };
426     int ch;
427     int opt_ind = 0;
428     int li;
429     char *end;
430     int flags = BDRV_O_RDWR;
431     int partition = -1;
432     int ret;
433     int fd;
434     bool seen_cache = false;
435     bool seen_discard = false;
436 #ifdef CONFIG_LINUX_AIO
437     bool seen_aio = false;
438 #endif
439     pthread_t client_thread;
440     const char *fmt = NULL;
441     Error *local_err = NULL;
442     BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
443 
444     /* The client thread uses SIGTERM to interrupt the server.  A signal
445      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
446      */
447     struct sigaction sa_sigterm;
448     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
449     sa_sigterm.sa_handler = termsig_handler;
450     sigaction(SIGTERM, &sa_sigterm, NULL);
451     qemu_init_exec_dir(argv[0]);
452 
453     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
454         switch (ch) {
455         case 's':
456             flags |= BDRV_O_SNAPSHOT;
457             break;
458         case 'n':
459             optarg = (char *) "none";
460             /* fallthrough */
461         case QEMU_NBD_OPT_CACHE:
462             if (seen_cache) {
463                 errx(EXIT_FAILURE, "-n and --cache can only be specified once");
464             }
465             seen_cache = true;
466             if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
467                 errx(EXIT_FAILURE, "Invalid cache mode `%s'", optarg);
468             }
469             break;
470 #ifdef CONFIG_LINUX_AIO
471         case QEMU_NBD_OPT_AIO:
472             if (seen_aio) {
473                 errx(EXIT_FAILURE, "--aio can only be specified once");
474             }
475             seen_aio = true;
476             if (!strcmp(optarg, "native")) {
477                 flags |= BDRV_O_NATIVE_AIO;
478             } else if (!strcmp(optarg, "threads")) {
479                 /* this is the default */
480             } else {
481                errx(EXIT_FAILURE, "invalid aio mode `%s'", optarg);
482             }
483             break;
484 #endif
485         case QEMU_NBD_OPT_DISCARD:
486             if (seen_discard) {
487                 errx(EXIT_FAILURE, "--discard can only be specified once");
488             }
489             seen_discard = true;
490             if (bdrv_parse_discard_flags(optarg, &flags) == -1) {
491                 errx(EXIT_FAILURE, "Invalid discard mode `%s'", optarg);
492             }
493             break;
494         case QEMU_NBD_OPT_DETECT_ZEROES:
495             detect_zeroes =
496                 qapi_enum_parse(BlockdevDetectZeroesOptions_lookup,
497                                 optarg,
498                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_MAX,
499                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
500                                 &local_err);
501             if (local_err) {
502                 errx(EXIT_FAILURE, "Failed to parse detect_zeroes mode: %s",
503                      error_get_pretty(local_err));
504             }
505             if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
506                 !(flags & BDRV_O_UNMAP)) {
507                 errx(EXIT_FAILURE, "setting detect-zeroes to unmap is not allowed "
508                                    "without setting discard operation to unmap");
509             }
510             break;
511         case 'b':
512             bindto = optarg;
513             break;
514         case 'p':
515             li = strtol(optarg, &end, 0);
516             if (*end) {
517                 errx(EXIT_FAILURE, "Invalid port `%s'", optarg);
518             }
519             if (li < 1 || li > 65535) {
520                 errx(EXIT_FAILURE, "Port out of range `%s'", optarg);
521             }
522             port = (uint16_t)li;
523             break;
524         case 'o':
525                 dev_offset = strtoll (optarg, &end, 0);
526             if (*end) {
527                 errx(EXIT_FAILURE, "Invalid offset `%s'", optarg);
528             }
529             if (dev_offset < 0) {
530                 errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
531             }
532             break;
533         case 'l':
534             if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
535                 sn_opts = qemu_opts_parse(&internal_snapshot_opts, optarg, 0);
536                 if (!sn_opts) {
537                     errx(EXIT_FAILURE, "Failed in parsing snapshot param `%s'",
538                          optarg);
539                 }
540             } else {
541                 sn_id_or_name = optarg;
542             }
543             /* fall through */
544         case 'r':
545             nbdflags |= NBD_FLAG_READ_ONLY;
546             flags &= ~BDRV_O_RDWR;
547             break;
548         case 'P':
549             partition = strtol(optarg, &end, 0);
550             if (*end) {
551                 errx(EXIT_FAILURE, "Invalid partition `%s'", optarg);
552             }
553             if (partition < 1 || partition > 8) {
554                 errx(EXIT_FAILURE, "Invalid partition %d", partition);
555             }
556             break;
557         case 'k':
558             sockpath = optarg;
559             if (sockpath[0] != '/') {
560                 errx(EXIT_FAILURE, "socket path must be absolute\n");
561             }
562             break;
563         case 'd':
564             disconnect = true;
565             break;
566         case 'c':
567             device = optarg;
568             break;
569         case 'e':
570             shared = strtol(optarg, &end, 0);
571             if (*end) {
572                 errx(EXIT_FAILURE, "Invalid shared device number '%s'", optarg);
573             }
574             if (shared < 1) {
575                 errx(EXIT_FAILURE, "Shared device number must be greater than 0\n");
576             }
577             break;
578         case 'f':
579             fmt = optarg;
580             break;
581         case 't':
582             persistent = 1;
583             break;
584         case 'v':
585             verbose = 1;
586             break;
587         case 'V':
588             version(argv[0]);
589             exit(0);
590             break;
591         case 'h':
592             usage(argv[0]);
593             exit(0);
594             break;
595         case '?':
596             errx(EXIT_FAILURE, "Try `%s --help' for more information.",
597                  argv[0]);
598         }
599     }
600 
601     if ((argc - optind) != 1) {
602         errx(EXIT_FAILURE, "Invalid number of argument.\n"
603              "Try `%s --help' for more information.",
604              argv[0]);
605     }
606 
607     if (disconnect) {
608         fd = open(argv[optind], O_RDWR);
609         if (fd < 0) {
610             err(EXIT_FAILURE, "Cannot open %s", argv[optind]);
611         }
612         nbd_disconnect(fd);
613 
614         close(fd);
615 
616         printf("%s disconnected\n", argv[optind]);
617 
618         return 0;
619     }
620 
621     if (device && !verbose) {
622         int stderr_fd[2];
623         pid_t pid;
624         int ret;
625 
626         if (qemu_pipe(stderr_fd) < 0) {
627             err(EXIT_FAILURE, "Error setting up communication pipe");
628         }
629 
630         /* Now daemonize, but keep a communication channel open to
631          * print errors and exit with the proper status code.
632          */
633         pid = fork();
634         if (pid == 0) {
635             close(stderr_fd[0]);
636             ret = qemu_daemon(1, 0);
637 
638             /* Temporarily redirect stderr to the parent's pipe...  */
639             dup2(stderr_fd[1], STDERR_FILENO);
640             if (ret < 0) {
641                 err(EXIT_FAILURE, "Failed to daemonize");
642             }
643 
644             /* ... close the descriptor we inherited and go on.  */
645             close(stderr_fd[1]);
646         } else {
647             bool errors = false;
648             char *buf;
649 
650             /* In the parent.  Print error messages from the child until
651              * it closes the pipe.
652              */
653             close(stderr_fd[1]);
654             buf = g_malloc(1024);
655             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
656                 errors = true;
657                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
658                 if (ret < 0) {
659                     exit(EXIT_FAILURE);
660                 }
661             }
662             if (ret < 0) {
663                 err(EXIT_FAILURE, "Cannot read from daemon");
664             }
665 
666             /* Usually the daemon should not print any message.
667              * Exit with zero status in that case.
668              */
669             exit(errors);
670         }
671     }
672 
673     if (device != NULL && sockpath == NULL) {
674         sockpath = g_malloc(128);
675         snprintf(sockpath, 128, SOCKET_PATH, basename(device));
676     }
677 
678     if (qemu_init_main_loop(&local_err)) {
679         error_report("%s", error_get_pretty(local_err));
680         error_free(local_err);
681         exit(EXIT_FAILURE);
682     }
683     bdrv_init();
684     atexit(bdrv_close_all);
685 
686     if (fmt) {
687         drv = bdrv_find_format(fmt);
688         if (!drv) {
689             errx(EXIT_FAILURE, "Unknown file format '%s'", fmt);
690         }
691     } else {
692         drv = NULL;
693     }
694 
695     blk = blk_new_with_bs("hda", &error_abort);
696     bs = blk_bs(blk);
697 
698     srcpath = argv[optind];
699     ret = bdrv_open(&bs, srcpath, NULL, NULL, flags, drv, &local_err);
700     if (ret < 0) {
701         errno = -ret;
702         err(EXIT_FAILURE, "Failed to bdrv_open '%s': %s", argv[optind],
703             error_get_pretty(local_err));
704     }
705 
706     if (sn_opts) {
707         ret = bdrv_snapshot_load_tmp(bs,
708                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
709                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
710                                      &local_err);
711     } else if (sn_id_or_name) {
712         ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
713                                                    &local_err);
714     }
715     if (ret < 0) {
716         errno = -ret;
717         err(EXIT_FAILURE,
718             "Failed to load snapshot: %s",
719             error_get_pretty(local_err));
720     }
721 
722     bs->detect_zeroes = detect_zeroes;
723     fd_size = bdrv_getlength(bs);
724 
725     if (partition != -1) {
726         ret = find_partition(bs, partition, &dev_offset, &fd_size);
727         if (ret < 0) {
728             errno = -ret;
729             err(EXIT_FAILURE, "Could not find partition %d", partition);
730         }
731     }
732 
733     exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed);
734 
735     if (sockpath) {
736         fd = unix_socket_incoming(sockpath);
737     } else {
738         fd = tcp_socket_incoming(bindto, port);
739     }
740 
741     if (fd < 0) {
742         return 1;
743     }
744 
745     if (device) {
746         int ret;
747 
748         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
749         if (ret != 0) {
750             errx(EXIT_FAILURE, "Failed to create client thread: %s",
751                  strerror(ret));
752         }
753     } else {
754         /* Shut up GCC warnings.  */
755         memset(&client_thread, 0, sizeof(client_thread));
756     }
757 
758     qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
759                          (void *)(uintptr_t)fd);
760 
761     /* now when the initialization is (almost) complete, chdir("/")
762      * to free any busy filesystems */
763     if (chdir("/") < 0) {
764         err(EXIT_FAILURE, "Could not chdir to root directory");
765     }
766 
767     state = RUNNING;
768     do {
769         main_loop_wait(false);
770         if (state == TERMINATE) {
771             state = TERMINATING;
772             nbd_export_close(exp);
773             nbd_export_put(exp);
774             exp = NULL;
775         }
776     } while (state != TERMINATED);
777 
778     blk_unref(blk);
779     if (sockpath) {
780         unlink(sockpath);
781     }
782 
783     qemu_opts_del(sn_opts);
784 
785     if (device) {
786         void *ret;
787         pthread_join(client_thread, &ret);
788         exit(ret != NULL);
789     } else {
790         exit(EXIT_SUCCESS);
791     }
792 }
793