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 "qemu/osdep.h"
  13 #include "sysemu/blockdev.h"
  14 #include "sysemu/block-backend.h"
  15 #include "hw/block/block.h"
  16 #include "qapi/qmp/qerror.h"
  17 #include "sysemu/sysemu.h"
  18 #include "qmp-commands.h"
  19 #include "trace.h"
  20 #include "block/nbd.h"
  21 #include "qemu/sockets.h"
  22
  23 static int server_fd = -1;
  24
  25 static void nbd_accept(void *opaque)
  26 {
  27     struct sockaddr_in addr;
  28     socklen_t addr_len = sizeof(addr);
  29
  30     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
  31     if (fd >= 0) {
  32         nbd_client_new(NULL, fd, nbd_client_put);
  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 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
  50                         Error **errp)
  51 {
  52     BlockBackend *blk;
  53     NBDExport *exp;
  54
  55     if (server_fd == -1) {
  56         error_setg(errp, "NBD server not running");
  57         return;
  58     }
  59
  60     if (nbd_export_find(device)) {
  61         error_setg(errp, "NBD server already exporting device '%s'", device);
  62         return;
  63     }
  64
  65     blk = blk_by_name(device);
  66     if (!blk) {
  67         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
  68                   "Device '%s' not found", device);
  69         return;
  70     }
  71     if (!blk_is_inserted(blk)) {
  72         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
  73         return;
  74     }
  75
  76     if (!has_writable) {
  77         writable = false;
  78     }
  79     if (blk_is_read_only(blk)) {
  80         writable = false;
  81     }
  82
  83     exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
  84                          errp);
  85     if (!exp) {
  86         return;
  87     }
  88
  89     nbd_export_set_name(exp, device);
  90
  91     /* The list of named exports has a strong reference to this export now and
  92      * our only way of accessing it is through nbd_export_find(), so we can drop
  93      * the strong reference that is @exp. */
  94     nbd_export_put(exp);
  95 }
  96
  97 void qmp_nbd_server_stop(Error **errp)
  98 {
  99     nbd_export_close_all();
 100
 101     if (server_fd != -1) {
 102         qemu_set_fd_handler(server_fd, NULL, NULL, NULL);
 103         close(server_fd);
 104         server_fd = -1;
 105     }
 106 }