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