blockdev-nbd.c

   1 /*
   2  * Serving QEMU block devices via NBD
   3  *
   4  * Copyright (c) 2012 Red Hat, Inc.
   5  *
   6  * Author: Paolo Bonzini <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU GPL, version 2 or
   9  * later.  See the COPYING file in the top-level directory.
  10  */
  11
  12 #include "sysemu/blockdev.h"
  13 #include "sysemu/block-backend.h"
  14 #include "hw/block/block.h"
  15 #include "qapi/qmp/qerror.h"
  16 #include "sysemu/sysemu.h"
  17 #include "qmp-commands.h"
  18 #include "trace.h"
  19 #include "block/nbd.h"
  20 #include "qemu/sockets.h"
  21
  22 static int server_fd = -1;
  23
  24 static void nbd_accept(void *opaque)
  25 {
  26     struct sockaddr_in addr;
  27     socklen_t addr_len = sizeof(addr);
  28
  29     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
  30     if (fd >= 0 && !nbd_client_new(NULL, fd, nbd_client_put)) {
  31         shutdown(fd, 2);
  32         close(fd);
  33     }
  34 }
  35
  36 void qmp_nbd_server_start(SocketAddress *addr, Error **errp)
  37 {
  38     if (server_fd != -1) {
  39         error_setg(errp, "NBD server already running");
  40         return;
  41     }
  42
  43     server_fd = socket_listen(addr, errp);
  44     if (server_fd != -1) {
  45         qemu_set_fd_handler(server_fd, nbd_accept, NULL, NULL);
  46     }
  47 }
  48
  49 /*
  50  * Hook into the BlockBackend notifiers to close the export when the
  51  * backend is closed.
  52  */
  53 typedef struct NBDCloseNotifier {
  54     Notifier n;
  55     NBDExport *exp;
  56     QTAILQ_ENTRY(NBDCloseNotifier) next;
  57 } NBDCloseNotifier;
  58
  59 static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
  60     QTAILQ_HEAD_INITIALIZER(close_notifiers);
  61
  62 static void nbd_close_notifier(Notifier *n, void *data)
  63 {
  64     NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
  65
  66     notifier_remove(&cn->n);
  67     QTAILQ_REMOVE(&close_notifiers, cn, next);
  68
  69     nbd_export_close(cn->exp);
  70     nbd_export_put(cn->exp);
  71     g_free(cn);
  72 }
  73
  74 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
  75                         Error **errp)
  76 {
  77     BlockBackend *blk;
  78     NBDExport *exp;
  79     NBDCloseNotifier *n;
  80
  81     if (server_fd == -1) {
  82         error_setg(errp, "NBD server not running");
  83         return;
  84     }
  85
  86     if (nbd_export_find(device)) {
  87         error_setg(errp, "NBD server already exporting device '%s'", device);
  88         return;
  89     }
  90
  91     blk = blk_by_name(device);
  92     if (!blk) {
  93         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
  94                   "Device '%s' not found", device);
  95         return;
  96     }
  97     if (!blk_is_inserted(blk)) {
  98         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
  99         return;
 100     }
 101
 102     if (!has_writable) {
 103         writable = false;
 104     }
 105     if (blk_is_read_only(blk)) {
 106         writable = false;
 107     }
 108
 109     exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
 110                          errp);
 111     if (!exp) {
 112         return;
 113     }
 114
 115     nbd_export_set_name(exp, device);
 116
 117     n = g_new0(NBDCloseNotifier, 1);
 118     n->n.notify = nbd_close_notifier;
 119     n->exp = exp;
 120     blk_add_close_notifier(blk, &n->n);
 121     QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
 122 }
 123
 124 void qmp_nbd_server_stop(Error **errp)
 125 {
 126     while (!QTAILQ_EMPTY(&close_notifiers)) {
 127         NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers);
 128         nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp));
 129     }
 130
 131     if (server_fd != -1) {
 132         qemu_set_fd_handler(server_fd, NULL, NULL, NULL);
 133         close(server_fd);
 134         server_fd = -1;
 135     }
 136 }