xref: /openbmc/qemu/qemu-nbd.c (revision 36f96c4b)
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 <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 SocketAddress *saddr;
52 static int persistent = 0;
53 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
54 static int shared = 1;
55 static int nb_fds;
56 static int server_fd;
57 
58 static void usage(const char *name)
59 {
60     (printf) (
61 "Usage: %s [OPTIONS] FILE\n"
62 "QEMU Disk Network Block Device Server\n"
63 "\n"
64 "  -h, --help                display this help and exit\n"
65 "  -V, --version             output version information and exit\n"
66 "\n"
67 "Connection properties:\n"
68 "  -p, --port=PORT           port to listen on (default `%d')\n"
69 "  -b, --bind=IFACE          interface to bind to (default `0.0.0.0')\n"
70 "  -k, --socket=PATH         path to the unix socket\n"
71 "                            (default '"SOCKET_PATH"')\n"
72 "  -e, --shared=NUM          device can be shared by NUM clients (default '1')\n"
73 "  -t, --persistent          don't exit on the last connection\n"
74 "  -v, --verbose             display extra debugging information\n"
75 "\n"
76 "Exposing part of the image:\n"
77 "  -o, --offset=OFFSET       offset into the image\n"
78 "  -P, --partition=NUM       only expose partition NUM\n"
79 "\n"
80 #ifdef __linux__
81 "Kernel NBD client support:\n"
82 "  -c, --connect=DEV         connect FILE to the local NBD device DEV\n"
83 "  -d, --disconnect          disconnect the specified device\n"
84 "\n"
85 #endif
86 "\n"
87 "Block device options:\n"
88 "  -f, --format=FORMAT       set image format (raw, qcow2, ...)\n"
89 "  -r, --read-only           export read-only\n"
90 "  -s, --snapshot            use FILE as an external snapshot, create a temporary\n"
91 "                            file with backing_file=FILE, redirect the write to\n"
92 "                            the temporary one\n"
93 "  -l, --load-snapshot=SNAPSHOT_PARAM\n"
94 "                            load an internal snapshot inside FILE and export it\n"
95 "                            as an read-only device, SNAPSHOT_PARAM format is\n"
96 "                            'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
97 "                            '[ID_OR_NAME]'\n"
98 "  -n, --nocache             disable host cache\n"
99 "      --cache=MODE          set cache mode (none, writeback, ...)\n"
100 "      --aio=MODE            set AIO mode (native or threads)\n"
101 "      --discard=MODE        set discard mode (ignore, unmap)\n"
102 "      --detect-zeroes=MODE  set detect-zeroes mode (off, on, unmap)\n"
103 "\n"
104 "Report bugs to <qemu-devel@nongnu.org>\n"
105     , name, NBD_DEFAULT_PORT, "DEVICE");
106 }
107 
108 static void version(const char *name)
109 {
110     printf(
111 "%s version 0.0.1\n"
112 "Written by Anthony Liguori.\n"
113 "\n"
114 "Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.\n"
115 "This is free software; see the source for copying conditions.  There is NO\n"
116 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
117     , name);
118 }
119 
120 struct partition_record
121 {
122     uint8_t bootable;
123     uint8_t start_head;
124     uint32_t start_cylinder;
125     uint8_t start_sector;
126     uint8_t system;
127     uint8_t end_head;
128     uint8_t end_cylinder;
129     uint8_t end_sector;
130     uint32_t start_sector_abs;
131     uint32_t nb_sectors_abs;
132 };
133 
134 static void read_partition(uint8_t *p, struct partition_record *r)
135 {
136     r->bootable = p[0];
137     r->start_head = p[1];
138     r->start_cylinder = p[3] | ((p[2] << 2) & 0x0300);
139     r->start_sector = p[2] & 0x3f;
140     r->system = p[4];
141     r->end_head = p[5];
142     r->end_cylinder = p[7] | ((p[6] << 2) & 0x300);
143     r->end_sector = p[6] & 0x3f;
144 
145     r->start_sector_abs = le32_to_cpup((uint32_t *)(p +  8));
146     r->nb_sectors_abs   = le32_to_cpup((uint32_t *)(p + 12));
147 }
148 
149 static int find_partition(BlockBackend *blk, 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 = blk_read(blk, 0, data, 1)) < 0) {
159         error_report("error while reading: %s", strerror(-ret));
160         exit(EXIT_FAILURE);
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].system || !mbr[i].nb_sectors_abs) {
171             continue;
172         }
173 
174         if (mbr[i].system == 0xF || mbr[i].system == 0x5) {
175             struct partition_record ext[4];
176             uint8_t data1[512];
177             int j;
178 
179             if ((ret = blk_read(blk, mbr[i].start_sector_abs, data1, 1)) < 0) {
180                 error_report("error while reading: %s", strerror(-ret));
181                 exit(EXIT_FAILURE);
182             }
183 
184             for (j = 0; j < 4; j++) {
185                 read_partition(&data1[446 + 16 * j], &ext[j]);
186                 if (!ext[j].system || !ext[j].nb_sectors_abs) {
187                     continue;
188                 }
189 
190                 if ((ext_partnum + j + 1) == partition) {
191                     *offset = (uint64_t)ext[j].start_sector_abs << 9;
192                     *size = (uint64_t)ext[j].nb_sectors_abs << 9;
193                     return 0;
194                 }
195             }
196             ext_partnum += 4;
197         } else if ((i + 1) == partition) {
198             *offset = (uint64_t)mbr[i].start_sector_abs << 9;
199             *size = (uint64_t)mbr[i].nb_sectors_abs << 9;
200             return 0;
201         }
202     }
203 
204     return -ENOENT;
205 }
206 
207 static void termsig_handler(int signum)
208 {
209     state = TERMINATE;
210     qemu_notify_event();
211 }
212 
213 
214 static void *show_parts(void *arg)
215 {
216     char *device = arg;
217     int nbd;
218 
219     /* linux just needs an open() to trigger
220      * the partition table update
221      * but remember to load the module with max_part != 0 :
222      *     modprobe nbd max_part=63
223      */
224     nbd = open(device, O_RDWR);
225     if (nbd >= 0) {
226         close(nbd);
227     }
228     return NULL;
229 }
230 
231 static void *nbd_client_thread(void *arg)
232 {
233     char *device = arg;
234     off_t size;
235     uint32_t nbdflags;
236     int fd, sock;
237     int ret;
238     pthread_t show_parts_thread;
239     Error *local_error = NULL;
240 
241 
242     sock = socket_connect(saddr, &local_error, NULL, NULL);
243     if (sock < 0) {
244         error_report_err(local_error);
245         goto out;
246     }
247 
248     ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
249                                 &size, &local_error);
250     if (ret < 0) {
251         if (local_error) {
252             error_report_err(local_error);
253         }
254         goto out_socket;
255     }
256 
257     fd = open(device, O_RDWR);
258     if (fd < 0) {
259         /* Linux-only, we can use %m in printf.  */
260         error_report("Failed to open %s: %m", device);
261         goto out_socket;
262     }
263 
264     ret = nbd_init(fd, sock, nbdflags, size);
265     if (ret < 0) {
266         goto out_fd;
267     }
268 
269     /* update partition table */
270     pthread_create(&show_parts_thread, NULL, show_parts, device);
271 
272     if (verbose) {
273         fprintf(stderr, "NBD device %s is now connected to %s\n",
274                 device, srcpath);
275     } else {
276         /* Close stderr so that the qemu-nbd process exits.  */
277         dup2(STDOUT_FILENO, STDERR_FILENO);
278     }
279 
280     ret = nbd_client(fd);
281     if (ret) {
282         goto out_fd;
283     }
284     close(fd);
285     kill(getpid(), SIGTERM);
286     return (void *) EXIT_SUCCESS;
287 
288 out_fd:
289     close(fd);
290 out_socket:
291     closesocket(sock);
292 out:
293     kill(getpid(), SIGTERM);
294     return (void *) EXIT_FAILURE;
295 }
296 
297 static int nbd_can_accept(void)
298 {
299     return nb_fds < shared;
300 }
301 
302 static void nbd_export_closed(NBDExport *exp)
303 {
304     assert(state == TERMINATING);
305     state = TERMINATED;
306 }
307 
308 static void nbd_update_server_fd_handler(int fd);
309 
310 static void nbd_client_closed(NBDClient *client)
311 {
312     nb_fds--;
313     if (nb_fds == 0 && !persistent && state == RUNNING) {
314         state = TERMINATE;
315     }
316     nbd_update_server_fd_handler(server_fd);
317     nbd_client_put(client);
318 }
319 
320 static void nbd_accept(void *opaque)
321 {
322     struct sockaddr_in addr;
323     socklen_t addr_len = sizeof(addr);
324 
325     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
326     if (fd < 0) {
327         perror("accept");
328         return;
329     }
330 
331     if (state >= TERMINATE) {
332         close(fd);
333         return;
334     }
335 
336     nb_fds++;
337     nbd_update_server_fd_handler(server_fd);
338     nbd_client_new(exp, fd, nbd_client_closed);
339 }
340 
341 static void nbd_update_server_fd_handler(int fd)
342 {
343     if (nbd_can_accept()) {
344         qemu_set_fd_handler(fd, nbd_accept, NULL, (void *)(uintptr_t)fd);
345     } else {
346         qemu_set_fd_handler(fd, NULL, NULL, NULL);
347     }
348 }
349 
350 
351 static SocketAddress *nbd_build_socket_address(const char *sockpath,
352                                                const char *bindto,
353                                                const char *port)
354 {
355     SocketAddress *saddr;
356 
357     saddr = g_new0(SocketAddress, 1);
358     if (sockpath) {
359         saddr->type = SOCKET_ADDRESS_KIND_UNIX;
360         saddr->u.q_unix = g_new0(UnixSocketAddress, 1);
361         saddr->u.q_unix->path = g_strdup(sockpath);
362     } else {
363         saddr->type = SOCKET_ADDRESS_KIND_INET;
364         saddr->u.inet = g_new0(InetSocketAddress, 1);
365         saddr->u.inet->host = g_strdup(bindto);
366         if (port) {
367             saddr->u.inet->port = g_strdup(port);
368         } else  {
369             saddr->u.inet->port = g_strdup_printf("%d", NBD_DEFAULT_PORT);
370         }
371     }
372 
373     return saddr;
374 }
375 
376 
377 int main(int argc, char **argv)
378 {
379     BlockBackend *blk;
380     BlockDriverState *bs;
381     off_t dev_offset = 0;
382     uint32_t nbdflags = 0;
383     bool disconnect = false;
384     const char *bindto = "0.0.0.0";
385     const char *port = NULL;
386     char *sockpath = NULL;
387     char *device = NULL;
388     off_t fd_size;
389     QemuOpts *sn_opts = NULL;
390     const char *sn_id_or_name = NULL;
391     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
392     struct option lopt[] = {
393         { "help", 0, NULL, 'h' },
394         { "version", 0, NULL, 'V' },
395         { "bind", 1, NULL, 'b' },
396         { "port", 1, NULL, 'p' },
397         { "socket", 1, NULL, 'k' },
398         { "offset", 1, NULL, 'o' },
399         { "read-only", 0, NULL, 'r' },
400         { "partition", 1, NULL, 'P' },
401         { "connect", 1, NULL, 'c' },
402         { "disconnect", 0, NULL, 'd' },
403         { "snapshot", 0, NULL, 's' },
404         { "load-snapshot", 1, NULL, 'l' },
405         { "nocache", 0, NULL, 'n' },
406         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
407         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
408         { "discard", 1, NULL, QEMU_NBD_OPT_DISCARD },
409         { "detect-zeroes", 1, NULL, QEMU_NBD_OPT_DETECT_ZEROES },
410         { "shared", 1, NULL, 'e' },
411         { "format", 1, NULL, 'f' },
412         { "persistent", 0, NULL, 't' },
413         { "verbose", 0, NULL, 'v' },
414         { NULL, 0, NULL, 0 }
415     };
416     int ch;
417     int opt_ind = 0;
418     char *end;
419     int flags = BDRV_O_RDWR;
420     int partition = -1;
421     int ret = 0;
422     int fd;
423     bool seen_cache = false;
424     bool seen_discard = false;
425     bool seen_aio = false;
426     pthread_t client_thread;
427     const char *fmt = NULL;
428     Error *local_err = NULL;
429     BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
430     QDict *options = NULL;
431 
432     /* The client thread uses SIGTERM to interrupt the server.  A signal
433      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
434      */
435     struct sigaction sa_sigterm;
436     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
437     sa_sigterm.sa_handler = termsig_handler;
438     sigaction(SIGTERM, &sa_sigterm, NULL);
439     qemu_init_exec_dir(argv[0]);
440 
441     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
442         switch (ch) {
443         case 's':
444             flags |= BDRV_O_SNAPSHOT;
445             break;
446         case 'n':
447             optarg = (char *) "none";
448             /* fallthrough */
449         case QEMU_NBD_OPT_CACHE:
450             if (seen_cache) {
451                 error_report("-n and --cache can only be specified once");
452                 exit(EXIT_FAILURE);
453             }
454             seen_cache = true;
455             if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
456                 error_report("Invalid cache mode `%s'", optarg);
457                 exit(EXIT_FAILURE);
458             }
459             break;
460         case QEMU_NBD_OPT_AIO:
461             if (seen_aio) {
462                 error_report("--aio can only be specified once");
463                 exit(EXIT_FAILURE);
464             }
465             seen_aio = true;
466             if (!strcmp(optarg, "native")) {
467                 flags |= BDRV_O_NATIVE_AIO;
468             } else if (!strcmp(optarg, "threads")) {
469                 /* this is the default */
470             } else {
471                error_report("invalid aio mode `%s'", optarg);
472                exit(EXIT_FAILURE);
473             }
474             break;
475         case QEMU_NBD_OPT_DISCARD:
476             if (seen_discard) {
477                 error_report("--discard can only be specified once");
478                 exit(EXIT_FAILURE);
479             }
480             seen_discard = true;
481             if (bdrv_parse_discard_flags(optarg, &flags) == -1) {
482                 error_report("Invalid discard mode `%s'", optarg);
483                 exit(EXIT_FAILURE);
484             }
485             break;
486         case QEMU_NBD_OPT_DETECT_ZEROES:
487             detect_zeroes =
488                 qapi_enum_parse(BlockdevDetectZeroesOptions_lookup,
489                                 optarg,
490                                 BLOCKDEV_DETECT_ZEROES_OPTIONS__MAX,
491                                 BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
492                                 &local_err);
493             if (local_err) {
494                 error_reportf_err(local_err,
495                                   "Failed to parse detect_zeroes mode: ");
496                 exit(EXIT_FAILURE);
497             }
498             if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
499                 !(flags & BDRV_O_UNMAP)) {
500                 error_report("setting detect-zeroes to unmap is not allowed "
501                              "without setting discard operation to unmap");
502                 exit(EXIT_FAILURE);
503             }
504             break;
505         case 'b':
506             bindto = optarg;
507             break;
508         case 'p':
509             port = optarg;
510             break;
511         case 'o':
512                 dev_offset = strtoll (optarg, &end, 0);
513             if (*end) {
514                 error_report("Invalid offset `%s'", optarg);
515                 exit(EXIT_FAILURE);
516             }
517             if (dev_offset < 0) {
518                 error_report("Offset must be positive `%s'", optarg);
519                 exit(EXIT_FAILURE);
520             }
521             break;
522         case 'l':
523             if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
524                 sn_opts = qemu_opts_parse_noisily(&internal_snapshot_opts,
525                                                   optarg, false);
526                 if (!sn_opts) {
527                     error_report("Failed in parsing snapshot param `%s'",
528                                  optarg);
529                     exit(EXIT_FAILURE);
530                 }
531             } else {
532                 sn_id_or_name = optarg;
533             }
534             /* fall through */
535         case 'r':
536             nbdflags |= NBD_FLAG_READ_ONLY;
537             flags &= ~BDRV_O_RDWR;
538             break;
539         case 'P':
540             partition = strtol(optarg, &end, 0);
541             if (*end) {
542                 error_report("Invalid partition `%s'", optarg);
543                 exit(EXIT_FAILURE);
544             }
545             if (partition < 1 || partition > 8) {
546                 error_report("Invalid partition %d", partition);
547                 exit(EXIT_FAILURE);
548             }
549             break;
550         case 'k':
551             sockpath = optarg;
552             if (sockpath[0] != '/') {
553                 error_report("socket path must be absolute");
554                 exit(EXIT_FAILURE);
555             }
556             break;
557         case 'd':
558             disconnect = true;
559             break;
560         case 'c':
561             device = optarg;
562             break;
563         case 'e':
564             shared = strtol(optarg, &end, 0);
565             if (*end) {
566                 error_report("Invalid shared device number '%s'", optarg);
567                 exit(EXIT_FAILURE);
568             }
569             if (shared < 1) {
570                 error_report("Shared device number must be greater than 0");
571                 exit(EXIT_FAILURE);
572             }
573             break;
574         case 'f':
575             fmt = optarg;
576             break;
577         case 't':
578             persistent = 1;
579             break;
580         case 'v':
581             verbose = 1;
582             break;
583         case 'V':
584             version(argv[0]);
585             exit(0);
586             break;
587         case 'h':
588             usage(argv[0]);
589             exit(0);
590             break;
591         case '?':
592             error_report("Try `%s --help' for more information.", argv[0]);
593             exit(EXIT_FAILURE);
594         }
595     }
596 
597     if ((argc - optind) != 1) {
598         error_report("Invalid number of arguments");
599         error_printf("Try `%s --help' for more information.\n", argv[0]);
600         exit(EXIT_FAILURE);
601     }
602 
603     if (disconnect) {
604         fd = open(argv[optind], O_RDWR);
605         if (fd < 0) {
606             error_report("Cannot open %s: %s", argv[optind],
607                          strerror(errno));
608             exit(EXIT_FAILURE);
609         }
610         nbd_disconnect(fd);
611 
612         close(fd);
613 
614         printf("%s disconnected\n", argv[optind]);
615 
616         return 0;
617     }
618 
619     if (device && !verbose) {
620         int stderr_fd[2];
621         pid_t pid;
622         int ret;
623 
624         if (qemu_pipe(stderr_fd) < 0) {
625             error_report("Error setting up communication pipe: %s",
626                          strerror(errno));
627             exit(EXIT_FAILURE);
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             error_report("Failed to fork: %s", strerror(errno));
636             exit(EXIT_FAILURE);
637         } else if (pid == 0) {
638             close(stderr_fd[0]);
639             ret = qemu_daemon(1, 0);
640 
641             /* Temporarily redirect stderr to the parent's pipe...  */
642             dup2(stderr_fd[1], STDERR_FILENO);
643             if (ret < 0) {
644                 error_report("Failed to daemonize: %s", strerror(errno));
645                 exit(EXIT_FAILURE);
646             }
647 
648             /* ... close the descriptor we inherited and go on.  */
649             close(stderr_fd[1]);
650         } else {
651             bool errors = false;
652             char *buf;
653 
654             /* In the parent.  Print error messages from the child until
655              * it closes the pipe.
656              */
657             close(stderr_fd[1]);
658             buf = g_malloc(1024);
659             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
660                 errors = true;
661                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
662                 if (ret < 0) {
663                     exit(EXIT_FAILURE);
664                 }
665             }
666             if (ret < 0) {
667                 error_report("Cannot read from daemon: %s",
668                              strerror(errno));
669                 exit(EXIT_FAILURE);
670             }
671 
672             /* Usually the daemon should not print any message.
673              * Exit with zero status in that case.
674              */
675             exit(errors);
676         }
677     }
678 
679     if (device != NULL && sockpath == NULL) {
680         sockpath = g_malloc(128);
681         snprintf(sockpath, 128, SOCKET_PATH, basename(device));
682     }
683 
684     saddr = nbd_build_socket_address(sockpath, bindto, port);
685 
686     if (qemu_init_main_loop(&local_err)) {
687         error_report_err(local_err);
688         exit(EXIT_FAILURE);
689     }
690     bdrv_init();
691     atexit(bdrv_close_all);
692 
693     if (fmt) {
694         options = qdict_new();
695         qdict_put(options, "driver", qstring_from_str(fmt));
696     }
697 
698     srcpath = argv[optind];
699     blk = blk_new_open("hda", srcpath, NULL, options, flags, &local_err);
700     if (!blk) {
701         error_reportf_err(local_err, "Failed to blk_new_open '%s': ",
702                           argv[optind]);
703         exit(EXIT_FAILURE);
704     }
705     bs = blk_bs(blk);
706 
707     if (sn_opts) {
708         ret = bdrv_snapshot_load_tmp(bs,
709                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
710                                      qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
711                                      &local_err);
712     } else if (sn_id_or_name) {
713         ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
714                                                    &local_err);
715     }
716     if (ret < 0) {
717         error_reportf_err(local_err, "Failed to load snapshot: ");
718         exit(EXIT_FAILURE);
719     }
720 
721     bs->detect_zeroes = detect_zeroes;
722     fd_size = blk_getlength(blk);
723     if (fd_size < 0) {
724         error_report("Failed to determine the image length: %s",
725                      strerror(-fd_size));
726         exit(EXIT_FAILURE);
727     }
728 
729     if (partition != -1) {
730         ret = find_partition(blk, partition, &dev_offset, &fd_size);
731         if (ret < 0) {
732             error_report("Could not find partition %d: %s", partition,
733                          strerror(-ret));
734             exit(EXIT_FAILURE);
735         }
736     }
737 
738     exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed,
739                          &local_err);
740     if (!exp) {
741         error_report_err(local_err);
742         exit(EXIT_FAILURE);
743     }
744 
745     fd = socket_listen(saddr, &local_err);
746     if (fd < 0) {
747         error_report_err(local_err);
748         return 1;
749     }
750 
751     if (device) {
752         int ret;
753 
754         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
755         if (ret != 0) {
756             error_report("Failed to create client thread: %s", strerror(ret));
757             exit(EXIT_FAILURE);
758         }
759     } else {
760         /* Shut up GCC warnings.  */
761         memset(&client_thread, 0, sizeof(client_thread));
762     }
763 
764     server_fd = fd;
765     nbd_update_server_fd_handler(fd);
766 
767     /* now when the initialization is (almost) complete, chdir("/")
768      * to free any busy filesystems */
769     if (chdir("/") < 0) {
770         error_report("Could not chdir to root directory: %s",
771                      strerror(errno));
772         exit(EXIT_FAILURE);
773     }
774 
775     state = RUNNING;
776     do {
777         main_loop_wait(false);
778         if (state == TERMINATE) {
779             state = TERMINATING;
780             nbd_export_close(exp);
781             nbd_export_put(exp);
782             exp = NULL;
783         }
784     } while (state != TERMINATED);
785 
786     blk_unref(blk);
787     if (sockpath) {
788         unlink(sockpath);
789     }
790 
791     qemu_opts_del(sn_opts);
792 
793     if (device) {
794         void *ret;
795         pthread_join(client_thread, &ret);
796         exit(ret != NULL);
797     } else {
798         exit(EXIT_SUCCESS);
799     }
800 }
801