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     char *tlshostname;
  37     NBDExportInfo initial_info;
  38     bool do_negotiation;
  39     bool do_retry;
  40
  41     QemuMutex mutex;
  42
  43     NBDExportInfo updated_info;
  44     /*
  45      * @sioc represents a successful result. While thread is running, @sioc is
  46      * used only by thread and not protected by mutex. When thread is not
  47      * running, @sioc is stolen by nbd_co_establish_connection() under mutex.
  48      */
  49     QIOChannelSocket *sioc;
  50     QIOChannel *ioc;
  51     /*
  52      * @err represents previous attempt. It may be copied by
  53      * nbd_co_establish_connection() when it reports failure.
  54      */
  55     Error *err;
  56
  57     /* All further fields are accessed only under mutex */
  58     bool running; /* thread is running now */
  59     bool detached; /* thread is detached and should cleanup the state */
  60
  61     /*
  62      * wait_co: if non-NULL, which coroutine to wake in
  63      * nbd_co_establish_connection() after yield()
  64      */
  65     Coroutine *wait_co;
  66 };
  67
  68 /*
  69  * The function isn't protected by any mutex, only call it when the client
  70  * connection attempt has not yet started.
  71  */
  72 void nbd_client_connection_enable_retry(NBDClientConnection *conn)
  73 {
  74     conn->do_retry = true;
  75 }
  76
  77 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
  78                                                bool do_negotiation,
  79                                                const char *export_name,
  80                                                const char *x_dirty_bitmap,
  81                                                QCryptoTLSCreds *tlscreds,
  82                                                const char *tlshostname)
  83 {
  84     NBDClientConnection *conn = g_new(NBDClientConnection, 1);
  85
  86     object_ref(OBJECT(tlscreds));
  87     *conn = (NBDClientConnection) {
  88         .saddr = QAPI_CLONE(SocketAddress, saddr),
  89         .tlscreds = tlscreds,
  90         .tlshostname = g_strdup(tlshostname),
  91         .do_negotiation = do_negotiation,
  92
  93         .initial_info.request_sizes = true,
  94         .initial_info.structured_reply = true,
  95         .initial_info.base_allocation = true,
  96         .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
  97         .initial_info.name = g_strdup(export_name ?: "")
  98     };
  99
 100     qemu_mutex_init(&conn->mutex);
 101
 102     return conn;
 103 }
 104
 105 static void nbd_client_connection_do_free(NBDClientConnection *conn)
 106 {
 107     if (conn->sioc) {
 108         qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
 109         object_unref(OBJECT(conn->sioc));
 110     }
 111     error_free(conn->err);
 112     qapi_free_SocketAddress(conn->saddr);
 113     g_free(conn->tlshostname);
 114     object_unref(OBJECT(conn->tlscreds));
 115     g_free(conn->initial_info.x_dirty_bitmap);
 116     g_free(conn->initial_info.name);
 117     g_free(conn);
 118 }
 119
 120 /*
 121  * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
 122  * are given @outioc is returned. @outioc is provided only on success.  The call
 123  * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
 124  */
 125 static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
 126                        NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
 127                        const char *tlshostname,
 128                        QIOChannel **outioc, Error **errp)
 129 {
 130     int ret;
 131
 132     if (outioc) {
 133         *outioc = NULL;
 134     }
 135
 136     ret = qio_channel_socket_connect_sync(sioc, addr, errp);
 137     if (ret < 0) {
 138         return ret;
 139     }
 140
 141     qio_channel_set_delay(QIO_CHANNEL(sioc), false);
 142
 143     if (!info) {
 144         return 0;
 145     }
 146
 147     ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
 148                                 tlshostname,
 149                                 outioc, info, errp);
 150     if (ret < 0) {
 151         /*
 152          * nbd_receive_negotiate() may setup tls ioc and return it even on
 153          * failure path. In this case we should use it instead of original
 154          * channel.
 155          */
 156         if (outioc && *outioc) {
 157             qio_channel_close(QIO_CHANNEL(*outioc), NULL);
 158             object_unref(OBJECT(*outioc));
 159             *outioc = NULL;
 160         } else {
 161             qio_channel_close(QIO_CHANNEL(sioc), NULL);
 162         }
 163
 164         return ret;
 165     }
 166
 167     return 0;
 168 }
 169
 170 static void *connect_thread_func(void *opaque)
 171 {
 172     NBDClientConnection *conn = opaque;
 173     int ret;
 174     bool do_free;
 175     uint64_t timeout = 1;
 176     uint64_t max_timeout = 16;
 177
 178     qemu_mutex_lock(&conn->mutex);
 179     while (!conn->detached) {
 180         Error *local_err = NULL;
 181
 182         assert(!conn->sioc);
 183         conn->sioc = qio_channel_socket_new();
 184
 185         qemu_mutex_unlock(&conn->mutex);
 186
 187         conn->updated_info = conn->initial_info;
 188
 189         ret = nbd_connect(conn->sioc, conn->saddr,
 190                           conn->do_negotiation ? &conn->updated_info : NULL,
 191                           conn->tlscreds, conn->tlshostname,
 192                           &conn->ioc, &local_err);
 193
 194         /*
 195          * conn->updated_info will finally be returned to the user. Clear the
 196          * pointers to our internally allocated strings, which are IN parameters
 197          * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
 198          * shoudn't be interested in these fields.
 199          */
 200         conn->updated_info.x_dirty_bitmap = NULL;
 201         conn->updated_info.name = NULL;
 202
 203         qemu_mutex_lock(&conn->mutex);
 204
 205         error_free(conn->err);
 206         conn->err = NULL;
 207         error_propagate(&conn->err, local_err);
 208
 209         if (ret < 0) {
 210             object_unref(OBJECT(conn->sioc));
 211             conn->sioc = NULL;
 212             if (conn->do_retry && !conn->detached) {
 213                 qemu_mutex_unlock(&conn->mutex);
 214
 215                 sleep(timeout);
 216                 if (timeout < max_timeout) {
 217                     timeout *= 2;
 218                 }
 219
 220                 qemu_mutex_lock(&conn->mutex);
 221                 continue;
 222             }
 223         }
 224
 225         break;
 226     }
 227
 228     /* mutex is locked */
 229
 230     assert(conn->running);
 231     conn->running = false;
 232     if (conn->wait_co) {
 233         aio_co_wake(conn->wait_co);
 234         conn->wait_co = NULL;
 235     }
 236     do_free = conn->detached;
 237
 238     qemu_mutex_unlock(&conn->mutex);
 239
 240     if (do_free) {
 241         nbd_client_connection_do_free(conn);
 242     }
 243
 244     return NULL;
 245 }
 246
 247 void nbd_client_connection_release(NBDClientConnection *conn)
 248 {
 249     bool do_free = false;
 250
 251     if (!conn) {
 252         return;
 253     }
 254
 255     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 256         assert(!conn->detached);
 257         if (conn->running) {
 258             conn->detached = true;
 259         } else {
 260             do_free = true;
 261         }
 262         if (conn->sioc) {
 263             qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
 264                                  QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
 265         }
 266     }
 267
 268     if (do_free) {
 269         nbd_client_connection_do_free(conn);
 270     }
 271 }
 272
 273 /*
 274  * Get a new connection in context of @conn:
 275  *   if the thread is running, wait for completion
 276  *   if the thread already succeeded in the background, and user didn't get the
 277  *     result, just return it now
 278  *   otherwise the thread is not running, so start a thread and wait for
 279  *     completion
 280  *
 281  * If @blocking is false, don't wait for the thread, return immediately.
 282  *
 283  * If @info is not NULL, also do nbd-negotiation after successful connection.
 284  * In this case info is used only as out parameter, and is fully initialized by
 285  * nbd_co_establish_connection(). "IN" fields of info as well as related only to
 286  * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
 287  * include/block/nbd.h).
 288  */
 289 QIOChannel *coroutine_fn
 290 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
 291                             bool blocking, Error **errp)
 292 {
 293     QemuThread thread;
 294
 295     if (conn->do_negotiation) {
 296         assert(info);
 297     }
 298
 299     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 300         /*
 301          * Don't call nbd_co_establish_connection() in several coroutines in
 302          * parallel. Only one call at once is supported.
 303          */
 304         assert(!conn->wait_co);
 305
 306         if (!conn->running) {
 307             if (conn->sioc) {
 308                 /* Previous attempt finally succeeded in background */
 309                 if (conn->do_negotiation) {
 310                     memcpy(info, &conn->updated_info, sizeof(*info));
 311                     if (conn->ioc) {
 312                         /* TLS channel now has own reference to parent */
 313                         object_unref(OBJECT(conn->sioc));
 314                         conn->sioc = NULL;
 315
 316                         return g_steal_pointer(&conn->ioc);
 317                     }
 318                 }
 319
 320                 assert(!conn->ioc);
 321
 322                 return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 323             }
 324
 325             conn->running = true;
 326             qemu_thread_create(&thread, "nbd-connect",
 327                                connect_thread_func, conn, QEMU_THREAD_DETACHED);
 328         }
 329
 330         if (!blocking) {
 331             if (conn->err) {
 332                 error_propagate(errp, error_copy(conn->err));
 333             } else {
 334                 error_setg(errp, "No connection at the moment");
 335             }
 336
 337             return NULL;
 338         }
 339
 340         conn->wait_co = qemu_coroutine_self();
 341     }
 342
 343     /*
 344      * We are going to wait for connect-thread finish, but
 345      * nbd_co_establish_connection_cancel() can interrupt.
 346      */
 347     qemu_coroutine_yield();
 348
 349     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 350         if (conn->running) {
 351             /*
 352              * The connection attempt was canceled and the coroutine resumed
 353              * before the connection thread finished its job.  Report the
 354              * attempt as failed, but leave the connection thread running,
 355              * to reuse it for the next connection attempt.
 356              */
 357             if (conn->err) {
 358                 error_propagate(errp, error_copy(conn->err));
 359             } else {
 360                 /*
 361                  * The only possible case here is cancelling by open_timer
 362                  * during nbd_open(). So, the error message is for that case.
 363                  * If we have more use cases, we can refactor
 364                  * nbd_co_establish_connection_cancel() to take an additional
 365                  * parameter cancel_reason, that would be passed than to the
 366                  * caller of cancelled nbd_co_establish_connection().
 367                  */
 368                 error_setg(errp, "Connection attempt cancelled by timeout");
 369             }
 370
 371             return NULL;
 372         } else {
 373             /* Thread finished. There must be either error or sioc */
 374             assert(!conn->err != !conn->sioc);
 375
 376             if (conn->err) {
 377                 error_propagate(errp, error_copy(conn->err));
 378                 return NULL;
 379             }
 380
 381             if (conn->do_negotiation) {
 382                 memcpy(info, &conn->updated_info, sizeof(*info));
 383                 if (conn->ioc) {
 384                     /* TLS channel now has own reference to parent */
 385                     object_unref(OBJECT(conn->sioc));
 386                     conn->sioc = NULL;
 387
 388                     return g_steal_pointer(&conn->ioc);
 389                 }
 390             }
 391
 392             assert(!conn->ioc);
 393
 394             return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 395         }
 396     }
 397
 398     abort(); /* unreachable */
 399 }
 400
 401 /*
 402  * nbd_co_establish_connection_cancel
 403  * Cancel nbd_co_establish_connection() asynchronously.
 404  *
 405  * Note that this function neither directly stops the thread nor closes the
 406  * socket, but rather safely wakes nbd_co_establish_connection() which is
 407  * sleeping in yield()
 408  */
 409 void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 410 {
 411     Coroutine *wait_co;
 412
 413     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 414         wait_co = g_steal_pointer(&conn->wait_co);
 415     }
 416
 417     if (wait_co) {
 418         aio_co_wake(wait_co);
 419     }
 420 }