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