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) {
  31         nbd_client_new(NULL, fd, nbd_client_put);
  32     }
  33 }
  34
  35 void qmp_nbd_server_start(SocketAddress *addr, Error **errp)
  36 {
  37     if (server_fd != -1) {
  38         error_setg(errp, "NBD server already running");
  39         return;
  40     }
  41
  42     server_fd = socket_listen(addr, errp);
  43     if (server_fd != -1) {
  44         qemu_set_fd_handler(server_fd, nbd_accept, NULL, NULL);
  45     }
  46 }
  47
  48 /*
  49  * Hook into the BlockBackend notifiers to close the export when the
  50  * backend is closed.
  51  */
  52 typedef struct NBDCloseNotifier {
  53     Notifier n;
  54     NBDExport *exp;
  55     QTAILQ_ENTRY(NBDCloseNotifier) next;
  56 } NBDCloseNotifier;
  57
  58 static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
  59     QTAILQ_HEAD_INITIALIZER(close_notifiers);
  60
  61 static void nbd_close_notifier(Notifier *n, void *data)
  62 {
  63     NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
  64
  65     notifier_remove(&cn->n);
  66     QTAILQ_REMOVE(&close_notifiers, cn, next);
  67
  68     nbd_export_close(cn->exp);
  69     nbd_export_put(cn->exp);
  70     g_free(cn);
  71 }
  72
  73 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
  74                         Error **errp)
  75 {
  76     BlockBackend *blk;
  77     NBDExport *exp;
  78     NBDCloseNotifier *n;
  79
  80     if (server_fd == -1) {
  81         error_setg(errp, "NBD server not running");
  82         return;
  83     }
  84
  85     if (nbd_export_find(device)) {
  86         error_setg(errp, "NBD server already exporting device '%s'", device);
  87         return;
  88     }
  89
  90     blk = blk_by_name(device);
  91     if (!blk) {
  92         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
  93                   "Device '%s' not found", device);
  94         return;
  95     }
  96     if (!blk_is_inserted(blk)) {
  97         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
  98         return;
  99     }
 100
 101     if (!has_writable) {
 102         writable = false;
 103     }
 104     if (blk_is_read_only(blk)) {
 105         writable = false;
 106     }
 107
 108     exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
 109                          errp);
 110     if (!exp) {
 111         return;
 112     }
 113
 114     nbd_export_set_name(exp, device);
 115
 116     n = g_new0(NBDCloseNotifier, 1);
 117     n->n.notify = nbd_close_notifier;
 118     n->exp = exp;
 119     blk_add_close_notifier(blk, &n->n);
 120     QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
 121 }
 122
 123 void qmp_nbd_server_stop(Error **errp)
 124 {
 125     while (!QTAILQ_EMPTY(&close_notifiers)) {
 126         NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers);
 127         nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp));
 128     }
 129
 130     if (server_fd != -1) {
 131         qemu_set_fd_handler(server_fd, NULL, NULL, NULL);
 132         close(server_fd);
 133         server_fd = -1;
 134     }
 135 }