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/error.h"
  17 #include "qapi/clone-visitor.h"
  18 #include "qapi/qapi-visit-block-export.h"
  19 #include "qapi/qapi-commands-block-export.h"
  20 #include "block/nbd.h"
  21 #include "io/channel-socket.h"
  22 #include "io/net-listener.h"
  23
  24 typedef struct NBDConn {
  25     QIOChannelSocket *cioc;
  26     QLIST_ENTRY(NBDConn) next;
  27 } NBDConn;
  28
  29 typedef struct NBDServerData {
  30     QIONetListener *listener;
  31     QCryptoTLSCreds *tlscreds;
  32     char *tlsauthz;
  33     uint32_t max_connections;
  34     uint32_t connections;
  35     QLIST_HEAD(, NBDConn) conns;
  36 } NBDServerData;
  37
  38 static NBDServerData *nbd_server;
  39 static int qemu_nbd_connections = -1; /* Non-negative if this is qemu-nbd */
  40
  41 static void nbd_update_server_watch(NBDServerData *s);
  42
  43 void nbd_server_is_qemu_nbd(int max_connections)
  44 {
  45     qemu_nbd_connections = max_connections;
  46 }
  47
  48 bool nbd_server_is_running(void)
  49 {
  50     return nbd_server || qemu_nbd_connections >= 0;
  51 }
  52
  53 int nbd_server_max_connections(void)
  54 {
  55     return nbd_server ? nbd_server->max_connections : qemu_nbd_connections;
  56 }
  57
  58 static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
  59 {
  60     NBDConn *conn = nbd_client_owner(client);
  61
  62     assert(qemu_in_main_thread() && nbd_server);
  63
  64     object_unref(OBJECT(conn->cioc));
  65     QLIST_REMOVE(conn, next);
  66     g_free(conn);
  67
  68     nbd_client_put(client);
  69     assert(nbd_server->connections > 0);
  70     nbd_server->connections--;
  71     nbd_update_server_watch(nbd_server);
  72 }
  73
  74 static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
  75                        gpointer opaque)
  76 {
  77     NBDConn *conn = g_new0(NBDConn, 1);
  78
  79     assert(qemu_in_main_thread() && nbd_server);
  80     nbd_server->connections++;
  81     object_ref(OBJECT(cioc));
  82     conn->cioc = cioc;
  83     QLIST_INSERT_HEAD(&nbd_server->conns, conn, next);
  84     nbd_update_server_watch(nbd_server);
  85
  86     qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
  87     /* TODO - expose handshake timeout as QMP option */
  88     nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
  89                    nbd_server->tlscreds, nbd_server->tlsauthz,
  90                    nbd_blockdev_client_closed, conn);
  91 }
  92
  93 static void nbd_update_server_watch(NBDServerData *s)
  94 {
  95     if (s->listener) {
  96         if (!s->max_connections || s->connections < s->max_connections) {
  97             qio_net_listener_set_client_func(s->listener, nbd_accept, NULL,
  98                                              NULL);
  99         } else {
 100             qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL);
 101         }
 102     }
 103 }
 104
 105 static void nbd_server_free(NBDServerData *server)
 106 {
 107     NBDConn *conn, *tmp;
 108
 109     if (!server) {
 110         return;
 111     }
 112
 113     /*
 114      * Forcefully close the listener socket, and any clients that have
 115      * not yet disconnected on their own.
 116      */
 117     qio_net_listener_disconnect(server->listener);
 118     object_unref(OBJECT(server->listener));
 119     server->listener = NULL;
 120     QLIST_FOREACH_SAFE(conn, &server->conns, next, tmp) {
 121         qio_channel_shutdown(QIO_CHANNEL(conn->cioc), QIO_CHANNEL_SHUTDOWN_BOTH,
 122                              NULL);
 123     }
 124
 125     AIO_WAIT_WHILE_UNLOCKED(NULL, server->connections > 0);
 126
 127     if (server->tlscreds) {
 128         object_unref(OBJECT(server->tlscreds));
 129     }
 130     g_free(server->tlsauthz);
 131
 132     g_free(server);
 133 }
 134
 135 static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
 136 {
 137     Object *obj;
 138     QCryptoTLSCreds *creds;
 139
 140     obj = object_resolve_path_component(
 141         object_get_objects_root(), id);
 142     if (!obj) {
 143         error_setg(errp, "No TLS credentials with id '%s'",
 144                    id);
 145         return NULL;
 146     }
 147     creds = (QCryptoTLSCreds *)
 148         object_dynamic_cast(obj, TYPE_QCRYPTO_TLS_CREDS);
 149     if (!creds) {
 150         error_setg(errp, "Object with id '%s' is not TLS credentials",
 151                    id);
 152         return NULL;
 153     }
 154
 155     if (!qcrypto_tls_creds_check_endpoint(creds,
 156                                           QCRYPTO_TLS_CREDS_ENDPOINT_SERVER,
 157                                           errp)) {
 158         return NULL;
 159     }
 160     object_ref(obj);
 161     return creds;
 162 }
 163
 164
 165 void nbd_server_start(SocketAddress *addr, const char *tls_creds,
 166                       const char *tls_authz, uint32_t max_connections,
 167                       Error **errp)
 168 {
 169     if (nbd_server) {
 170         error_setg(errp, "NBD server already running");
 171         return;
 172     }
 173
 174     nbd_server = g_new0(NBDServerData, 1);
 175     nbd_server->max_connections = max_connections;
 176     nbd_server->listener = qio_net_listener_new();
 177
 178     qio_net_listener_set_name(nbd_server->listener,
 179                               "nbd-listener");
 180
 181     /*
 182      * Because this server is persistent, a backlog of SOMAXCONN is
 183      * better than trying to size it to max_connections.
 184      */
 185     if (qio_net_listener_open_sync(nbd_server->listener, addr, SOMAXCONN,
 186                                    errp) < 0) {
 187         goto error;
 188     }
 189
 190     if (tls_creds) {
 191         nbd_server->tlscreds = nbd_get_tls_creds(tls_creds, errp);
 192         if (!nbd_server->tlscreds) {
 193             goto error;
 194         }
 195     }
 196
 197     nbd_server->tlsauthz = g_strdup(tls_authz);
 198
 199     nbd_update_server_watch(nbd_server);
 200
 201     return;
 202
 203  error:
 204     nbd_server_free(nbd_server);
 205     nbd_server = NULL;
 206 }
 207
 208 void nbd_server_start_options(NbdServerOptions *arg, Error **errp)
 209 {
 210     if (!arg->has_max_connections) {
 211         arg->max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
 212     }
 213
 214     nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz,
 215                      arg->max_connections, errp);
 216 }
 217
 218 void qmp_nbd_server_start(SocketAddressLegacy *addr,
 219                           const char *tls_creds,
 220                           const char *tls_authz,
 221                           bool has_max_connections, uint32_t max_connections,
 222                           Error **errp)
 223 {
 224     SocketAddress *addr_flat = socket_address_flatten(addr);
 225
 226     if (!has_max_connections) {
 227         max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
 228     }
 229
 230     nbd_server_start(addr_flat, tls_creds, tls_authz, max_connections, errp);
 231     qapi_free_SocketAddress(addr_flat);
 232 }
 233
 234 void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
 235 {
 236     BlockExport *export;
 237     BlockDriverState *bs;
 238     BlockBackend *on_eject_blk;
 239     BlockExportOptions *export_opts;
 240
 241     bs = bdrv_lookup_bs(arg->device, arg->device, errp);
 242     if (!bs) {
 243         return;
 244     }
 245
 246     /*
 247      * block-export-add would default to the node-name, but we may have to use
 248      * the device name as a default here for compatibility.
 249      */
 250     if (!arg->name) {
 251         arg->name = g_strdup(arg->device);
 252     }
 253
 254     export_opts = g_new(BlockExportOptions, 1);
 255     *export_opts = (BlockExportOptions) {
 256         .type                   = BLOCK_EXPORT_TYPE_NBD,
 257         .id                     = g_strdup(arg->name),
 258         .node_name              = g_strdup(bdrv_get_node_name(bs)),
 259         .has_writable           = arg->has_writable,
 260         .writable               = arg->writable,
 261     };
 262     QAPI_CLONE_MEMBERS(BlockExportOptionsNbdBase, &export_opts->u.nbd,
 263                        qapi_NbdServerAddOptions_base(arg));
 264     if (arg->bitmap) {
 265         BlockDirtyBitmapOrStr *el = g_new(BlockDirtyBitmapOrStr, 1);
 266
 267         *el = (BlockDirtyBitmapOrStr) {
 268             .type = QTYPE_QSTRING,
 269             .u.local = g_strdup(arg->bitmap),
 270         };
 271         export_opts->u.nbd.has_bitmaps = true;
 272         QAPI_LIST_PREPEND(export_opts->u.nbd.bitmaps, el);
 273     }
 274
 275     /*
 276      * nbd-server-add doesn't complain when a read-only device should be
 277      * exported as writable, but simply downgrades it. This is an error with
 278      * block-export-add.
 279      */
 280     if (bdrv_is_read_only(bs)) {
 281         export_opts->has_writable = true;
 282         export_opts->writable = false;
 283     }
 284
 285     export = blk_exp_add(export_opts, errp);
 286     if (!export) {
 287         goto fail;
 288     }
 289
 290     /*
 291      * nbd-server-add removes the export when the named BlockBackend used for
 292      * @device goes away.
 293      */
 294     on_eject_blk = blk_by_name(arg->device);
 295     if (on_eject_blk) {
 296         nbd_export_set_on_eject_blk(export, on_eject_blk);
 297     }
 298
 299 fail:
 300     qapi_free_BlockExportOptions(export_opts);
 301 }
 302
 303 void qmp_nbd_server_remove(const char *name,
 304                            bool has_mode, BlockExportRemoveMode mode,
 305                            Error **errp)
 306 {
 307     BlockExport *exp;
 308
 309     exp = blk_exp_find(name);
 310     if (exp && exp->drv->type != BLOCK_EXPORT_TYPE_NBD) {
 311         error_setg(errp, "Block export '%s' is not an NBD export", name);
 312         return;
 313     }
 314
 315     qmp_block_export_del(name, has_mode, mode, errp);
 316 }
 317
 318 void qmp_nbd_server_stop(Error **errp)
 319 {
 320     if (!nbd_server) {
 321         error_setg(errp, "NBD server not running");
 322         return;
 323     }
 324
 325     blk_exp_close_all_type(BLOCK_EXPORT_TYPE_NBD);
 326
 327     nbd_server_free(nbd_server);
 328     nbd_server = NULL;
 329 }