nbd/client-connection.c

   1 /*
   2  * QEMU Block driver for  NBD
   3  *
   4  * Copyright (c) 2021 Virtuozzo International GmbH.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu/osdep.h"
  26
  27 #include "block/nbd.h"
  28
  29 #include "qapi/qapi-visit-sockets.h"
  30 #include "qapi/clone-visitor.h"
  31
  32 struct NBDClientConnection {
  33     /* Initialization constants, never change */
  34     SocketAddress *saddr; /* address to connect to */
  35     QCryptoTLSCreds *tlscreds;
  36     NBDExportInfo initial_info;
  37     bool do_negotiation;
  38     bool do_retry;
  39
  40     QemuMutex mutex;
  41
  42     /*
  43      * @sioc and @err represent a connection attempt.  While running
  44      * is true, they are only used by the connection thread, and mutex
  45      * locking is not needed.  Once the thread finishes,
  46      * nbd_co_establish_connection then steals these pointers while
  47      * under the mutex.
  48      */
  49     NBDExportInfo updated_info;
  50     QIOChannelSocket *sioc;
  51     QIOChannel *ioc;
  52     Error *err;
  53
  54     /* All further fields are accessed only under mutex */
  55     bool running; /* thread is running now */
  56     bool detached; /* thread is detached and should cleanup the state */
  57
  58     /*
  59      * wait_co: if non-NULL, which coroutine to wake in
  60      * nbd_co_establish_connection() after yield()
  61      */
  62     Coroutine *wait_co;
  63 };
  64
  65 /*
  66  * The function isn't protected by any mutex, only call it when the client
  67  * connection attempt has not yet started.
  68  */
  69 void nbd_client_connection_enable_retry(NBDClientConnection *conn)
  70 {
  71     conn->do_retry = true;
  72 }
  73
  74 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
  75                                                bool do_negotiation,
  76                                                const char *export_name,
  77                                                const char *x_dirty_bitmap,
  78                                                QCryptoTLSCreds *tlscreds)
  79 {
  80     NBDClientConnection *conn = g_new(NBDClientConnection, 1);
  81
  82     object_ref(OBJECT(tlscreds));
  83     *conn = (NBDClientConnection) {
  84         .saddr = QAPI_CLONE(SocketAddress, saddr),
  85         .tlscreds = tlscreds,
  86         .do_negotiation = do_negotiation,
  87
  88         .initial_info.request_sizes = true,
  89         .initial_info.structured_reply = true,
  90         .initial_info.base_allocation = true,
  91         .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
  92         .initial_info.name = g_strdup(export_name ?: "")
  93     };
  94
  95     qemu_mutex_init(&conn->mutex);
  96
  97     return conn;
  98 }
  99
 100 static void nbd_client_connection_do_free(NBDClientConnection *conn)
 101 {
 102     if (conn->sioc) {
 103         qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
 104         object_unref(OBJECT(conn->sioc));
 105     }
 106     error_free(conn->err);
 107     qapi_free_SocketAddress(conn->saddr);
 108     object_unref(OBJECT(conn->tlscreds));
 109     g_free(conn->initial_info.x_dirty_bitmap);
 110     g_free(conn->initial_info.name);
 111     g_free(conn);
 112 }
 113
 114 /*
 115  * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
 116  * are given @outioc is returned. @outioc is provided only on success.  The call
 117  * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
 118  */
 119 static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
 120                        NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
 121                        QIOChannel **outioc, Error **errp)
 122 {
 123     int ret;
 124
 125     if (outioc) {
 126         *outioc = NULL;
 127     }
 128
 129     ret = qio_channel_socket_connect_sync(sioc, addr, errp);
 130     if (ret < 0) {
 131         return ret;
 132     }
 133
 134     qio_channel_set_delay(QIO_CHANNEL(sioc), false);
 135
 136     if (!info) {
 137         return 0;
 138     }
 139
 140     ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
 141                                 tlscreds ? addr->u.inet.host : NULL,
 142                                 outioc, info, errp);
 143     if (ret < 0) {
 144         /*
 145          * nbd_receive_negotiate() may setup tls ioc and return it even on
 146          * failure path. In this case we should use it instead of original
 147          * channel.
 148          */
 149         if (outioc && *outioc) {
 150             qio_channel_close(QIO_CHANNEL(*outioc), NULL);
 151             object_unref(OBJECT(*outioc));
 152             *outioc = NULL;
 153         } else {
 154             qio_channel_close(QIO_CHANNEL(sioc), NULL);
 155         }
 156
 157         return ret;
 158     }
 159
 160     return 0;
 161 }
 162
 163 static void *connect_thread_func(void *opaque)
 164 {
 165     NBDClientConnection *conn = opaque;
 166     int ret;
 167     bool do_free;
 168     uint64_t timeout = 1;
 169     uint64_t max_timeout = 16;
 170
 171     qemu_mutex_lock(&conn->mutex);
 172     while (!conn->detached) {
 173         assert(!conn->sioc);
 174         conn->sioc = qio_channel_socket_new();
 175
 176         qemu_mutex_unlock(&conn->mutex);
 177
 178         error_free(conn->err);
 179         conn->err = NULL;
 180         conn->updated_info = conn->initial_info;
 181
 182         ret = nbd_connect(conn->sioc, conn->saddr,
 183                           conn->do_negotiation ? &conn->updated_info : NULL,
 184                           conn->tlscreds, &conn->ioc, &conn->err);
 185
 186         /*
 187          * conn->updated_info will finally be returned to the user. Clear the
 188          * pointers to our internally allocated strings, which are IN parameters
 189          * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
 190          * shoudn't be interested in these fields.
 191          */
 192         conn->updated_info.x_dirty_bitmap = NULL;
 193         conn->updated_info.name = NULL;
 194
 195         qemu_mutex_lock(&conn->mutex);
 196
 197         if (ret < 0) {
 198             object_unref(OBJECT(conn->sioc));
 199             conn->sioc = NULL;
 200             if (conn->do_retry && !conn->detached) {
 201                 qemu_mutex_unlock(&conn->mutex);
 202
 203                 sleep(timeout);
 204                 if (timeout < max_timeout) {
 205                     timeout *= 2;
 206                 }
 207
 208                 qemu_mutex_lock(&conn->mutex);
 209                 continue;
 210             }
 211         }
 212
 213         break;
 214     }
 215
 216     /* mutex is locked */
 217
 218     assert(conn->running);
 219     conn->running = false;
 220     if (conn->wait_co) {
 221         aio_co_wake(conn->wait_co);
 222         conn->wait_co = NULL;
 223     }
 224     do_free = conn->detached;
 225
 226     qemu_mutex_unlock(&conn->mutex);
 227
 228     if (do_free) {
 229         nbd_client_connection_do_free(conn);
 230     }
 231
 232     return NULL;
 233 }
 234
 235 void nbd_client_connection_release(NBDClientConnection *conn)
 236 {
 237     bool do_free = false;
 238
 239     if (!conn) {
 240         return;
 241     }
 242
 243     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 244         assert(!conn->detached);
 245         if (conn->running) {
 246             conn->detached = true;
 247         } else {
 248             do_free = true;
 249         }
 250         if (conn->sioc) {
 251             qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
 252                                  QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
 253         }
 254     }
 255
 256     if (do_free) {
 257         nbd_client_connection_do_free(conn);
 258     }
 259 }
 260
 261 /*
 262  * Get a new connection in context of @conn:
 263  *   if the thread is running, wait for completion
 264  *   if the thread already succeeded in the background, and user didn't get the
 265  *     result, just return it now
 266  *   otherwise the thread is not running, so start a thread and wait for
 267  *     completion
 268  *
 269  * If @blocking is false, don't wait for the thread, return immediately.
 270  *
 271  * If @info is not NULL, also do nbd-negotiation after successful connection.
 272  * In this case info is used only as out parameter, and is fully initialized by
 273  * nbd_co_establish_connection(). "IN" fields of info as well as related only to
 274  * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
 275  * include/block/nbd.h).
 276  */
 277 QIOChannel *coroutine_fn
 278 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
 279                             bool blocking, Error **errp)
 280 {
 281     QemuThread thread;
 282
 283     if (conn->do_negotiation) {
 284         assert(info);
 285     }
 286
 287     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 288         /*
 289          * Don't call nbd_co_establish_connection() in several coroutines in
 290          * parallel. Only one call at once is supported.
 291          */
 292         assert(!conn->wait_co);
 293
 294         if (!conn->running) {
 295             if (conn->sioc) {
 296                 /* Previous attempt finally succeeded in background */
 297                 if (conn->do_negotiation) {
 298                     memcpy(info, &conn->updated_info, sizeof(*info));
 299                     if (conn->ioc) {
 300                         /* TLS channel now has own reference to parent */
 301                         object_unref(OBJECT(conn->sioc));
 302                         conn->sioc = NULL;
 303
 304                         return g_steal_pointer(&conn->ioc);
 305                     }
 306                 }
 307
 308                 assert(!conn->ioc);
 309
 310                 return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 311             }
 312
 313             conn->running = true;
 314             error_free(conn->err);
 315             conn->err = NULL;
 316             qemu_thread_create(&thread, "nbd-connect",
 317                                connect_thread_func, conn, QEMU_THREAD_DETACHED);
 318         }
 319
 320         if (!blocking) {
 321             error_setg(errp, "No connection at the moment");
 322             return NULL;
 323         }
 324
 325         conn->wait_co = qemu_coroutine_self();
 326     }
 327
 328     /*
 329      * We are going to wait for connect-thread finish, but
 330      * nbd_co_establish_connection_cancel() can interrupt.
 331      */
 332     qemu_coroutine_yield();
 333
 334     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 335         if (conn->running) {
 336             /*
 337              * The connection attempt was canceled and the coroutine resumed
 338              * before the connection thread finished its job.  Report the
 339              * attempt as failed, but leave the connection thread running,
 340              * to reuse it for the next connection attempt.
 341              */
 342             error_setg(errp, "Connection attempt cancelled by other operation");
 343             return NULL;
 344         } else {
 345             error_propagate(errp, conn->err);
 346             conn->err = NULL;
 347             if (!conn->sioc) {
 348                 return NULL;
 349             }
 350             if (conn->do_negotiation) {
 351                 memcpy(info, &conn->updated_info, sizeof(*info));
 352                 if (conn->ioc) {
 353                     /* TLS channel now has own reference to parent */
 354                     object_unref(OBJECT(conn->sioc));
 355                     conn->sioc = NULL;
 356
 357                     return g_steal_pointer(&conn->ioc);
 358                 }
 359             }
 360
 361             assert(!conn->ioc);
 362
 363             return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 364         }
 365     }
 366
 367     abort(); /* unreachable */
 368 }
 369
 370 /*
 371  * nbd_co_establish_connection_cancel
 372  * Cancel nbd_co_establish_connection() asynchronously.
 373  *
 374  * Note that this function neither directly stops the thread nor closes the
 375  * socket, but rather safely wakes nbd_co_establish_connection() which is
 376  * sleeping in yield()
 377  */
 378 void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 379 {
 380     Coroutine *wait_co;
 381
 382     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 383         wait_co = g_steal_pointer(&conn->wait_co);
 384     }
 385
 386     if (wait_co) {
 387         aio_co_wake(wait_co);
 388     }
 389 }