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 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
  49                         Error **errp)
  50 {
  51     BlockBackend *blk;
  52     NBDExport *exp;
  53
  54     if (server_fd == -1) {
  55         error_setg(errp, "NBD server not running");
  56         return;
  57     }
  58
  59     if (nbd_export_find(device)) {
  60         error_setg(errp, "NBD server already exporting device '%s'", device);
  61         return;
  62     }
  63
  64     blk = blk_by_name(device);
  65     if (!blk) {
  66         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
  67                   "Device '%s' not found", device);
  68         return;
  69     }
  70     if (!blk_is_inserted(blk)) {
  71         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
  72         return;
  73     }
  74
  75     if (!has_writable) {
  76         writable = false;
  77     }
  78     if (blk_is_read_only(blk)) {
  79         writable = false;
  80     }
  81
  82     exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
  83                          errp);
  84     if (!exp) {
  85         return;
  86     }
  87
  88     nbd_export_set_name(exp, device);
  89
  90     /* The list of named exports has a strong reference to this export now and
  91      * our only way of accessing it is through nbd_export_find(), so we can drop
  92      * the strong reference that is @exp. */
  93     nbd_export_put(exp);
  94 }
  95
  96 void qmp_nbd_server_stop(Error **errp)
  97 {
  98     nbd_export_close_all();
  99
 100     if (server_fd != -1) {
 101         qemu_set_fd_handler(server_fd, NULL, NULL, NULL);
 102         close(server_fd);
 103         server_fd = -1;
 104     }
 105 }