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 #include "trace.h"
  27
  28 #include "block/nbd.h"
  29
  30 #include "qapi/qapi-visit-sockets.h"
  31 #include "qapi/clone-visitor.h"
  32 #include "qemu/coroutine.h"
  33
  34 struct NBDClientConnection {
  35     /* Initialization constants, never change */
  36     SocketAddress *saddr; /* address to connect to */
  37     QCryptoTLSCreds *tlscreds;
  38     char *tlshostname;
  39     NBDExportInfo initial_info;
  40     bool do_negotiation;
  41     bool do_retry;
  42
  43     QemuMutex mutex;
  44
  45     NBDExportInfo updated_info;
  46     /*
  47      * @sioc represents a successful result. While thread is running, @sioc is
  48      * used only by thread and not protected by mutex. When thread is not
  49      * running, @sioc is stolen by nbd_co_establish_connection() under mutex.
  50      */
  51     QIOChannelSocket *sioc;
  52     QIOChannel *ioc;
  53     /*
  54      * @err represents previous attempt. It may be copied by
  55      * nbd_co_establish_connection() when it reports failure.
  56      */
  57     Error *err;
  58
  59     /* All further fields are accessed only under mutex */
  60     bool running; /* thread is running now */
  61     bool detached; /* thread is detached and should cleanup the state */
  62
  63     /*
  64      * wait_co: if non-NULL, which coroutine to wake in
  65      * nbd_co_establish_connection() after yield()
  66      */
  67     Coroutine *wait_co;
  68 };
  69
  70 /*
  71  * The function isn't protected by any mutex, only call it when the client
  72  * connection attempt has not yet started.
  73  */
  74 void nbd_client_connection_enable_retry(NBDClientConnection *conn)
  75 {
  76     conn->do_retry = true;
  77 }
  78
  79 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
  80                                                bool do_negotiation,
  81                                                const char *export_name,
  82                                                const char *x_dirty_bitmap,
  83                                                QCryptoTLSCreds *tlscreds,
  84                                                const char *tlshostname)
  85 {
  86     NBDClientConnection *conn = g_new(NBDClientConnection, 1);
  87
  88     object_ref(OBJECT(tlscreds));
  89     *conn = (NBDClientConnection) {
  90         .saddr = QAPI_CLONE(SocketAddress, saddr),
  91         .tlscreds = tlscreds,
  92         .tlshostname = g_strdup(tlshostname),
  93         .do_negotiation = do_negotiation,
  94
  95         .initial_info.request_sizes = true,
  96         .initial_info.mode = NBD_MODE_EXTENDED,
  97         .initial_info.base_allocation = true,
  98         .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
  99         .initial_info.name = g_strdup(export_name ?: "")
 100     };
 101
 102     qemu_mutex_init(&conn->mutex);
 103
 104     return conn;
 105 }
 106
 107 static void nbd_client_connection_do_free(NBDClientConnection *conn)
 108 {
 109     if (conn->sioc) {
 110         qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
 111         object_unref(OBJECT(conn->sioc));
 112     }
 113     error_free(conn->err);
 114     qapi_free_SocketAddress(conn->saddr);
 115     g_free(conn->tlshostname);
 116     object_unref(OBJECT(conn->tlscreds));
 117     g_free(conn->initial_info.x_dirty_bitmap);
 118     g_free(conn->initial_info.name);
 119     g_free(conn);
 120 }
 121
 122 /*
 123  * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
 124  * are given @outioc is returned. @outioc is provided only on success.  The call
 125  * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
 126  */
 127 static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
 128                        NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
 129                        const char *tlshostname,
 130                        QIOChannel **outioc, Error **errp)
 131 {
 132     int ret;
 133
 134     if (outioc) {
 135         *outioc = NULL;
 136     }
 137
 138     ret = qio_channel_socket_connect_sync(sioc, addr, errp);
 139     if (ret < 0) {
 140         return ret;
 141     }
 142
 143     qio_channel_set_delay(QIO_CHANNEL(sioc), false);
 144
 145     if (!info) {
 146         return 0;
 147     }
 148
 149     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), tlscreds, tlshostname,
 150                                 outioc, info, errp);
 151     if (ret < 0) {
 152         /*
 153          * nbd_receive_negotiate() may setup tls ioc and return it even on
 154          * failure path. In this case we should use it instead of original
 155          * channel.
 156          */
 157         if (outioc && *outioc) {
 158             qio_channel_close(*outioc, NULL);
 159             object_unref(OBJECT(*outioc));
 160             *outioc = NULL;
 161         } else {
 162             qio_channel_close(QIO_CHANNEL(sioc), NULL);
 163         }
 164
 165         return ret;
 166     }
 167
 168     return 0;
 169 }
 170
 171 static void *connect_thread_func(void *opaque)
 172 {
 173     NBDClientConnection *conn = opaque;
 174     int ret;
 175     bool do_free;
 176     uint64_t timeout = 1;
 177     uint64_t max_timeout = 16;
 178
 179     qemu_mutex_lock(&conn->mutex);
 180     while (!conn->detached) {
 181         Error *local_err = NULL;
 182
 183         assert(!conn->sioc);
 184         conn->sioc = qio_channel_socket_new();
 185
 186         qemu_mutex_unlock(&conn->mutex);
 187
 188         conn->updated_info = conn->initial_info;
 189
 190         ret = nbd_connect(conn->sioc, conn->saddr,
 191                           conn->do_negotiation ? &conn->updated_info : NULL,
 192                           conn->tlscreds, conn->tlshostname,
 193                           &conn->ioc, &local_err);
 194
 195         /*
 196          * conn->updated_info will finally be returned to the user. Clear the
 197          * pointers to our internally allocated strings, which are IN parameters
 198          * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
 199          * shouldn't be interested in these fields.
 200          */
 201         conn->updated_info.x_dirty_bitmap = NULL;
 202         conn->updated_info.name = NULL;
 203
 204         qemu_mutex_lock(&conn->mutex);
 205
 206         error_free(conn->err);
 207         conn->err = NULL;
 208         error_propagate(&conn->err, local_err);
 209
 210         if (ret < 0) {
 211             object_unref(OBJECT(conn->sioc));
 212             conn->sioc = NULL;
 213             if (conn->do_retry && !conn->detached) {
 214                 trace_nbd_connect_thread_sleep(timeout);
 215                 qemu_mutex_unlock(&conn->mutex);
 216
 217                 sleep(timeout);
 218                 if (timeout < max_timeout) {
 219                     timeout *= 2;
 220                 }
 221
 222                 qemu_mutex_lock(&conn->mutex);
 223                 continue;
 224             }
 225         }
 226
 227         break;
 228     }
 229
 230     /* mutex is locked */
 231
 232     assert(conn->running);
 233     conn->running = false;
 234     if (conn->wait_co) {
 235         aio_co_wake(conn->wait_co);
 236         conn->wait_co = NULL;
 237     }
 238     do_free = conn->detached;
 239
 240     qemu_mutex_unlock(&conn->mutex);
 241
 242     if (do_free) {
 243         nbd_client_connection_do_free(conn);
 244     }
 245
 246     return NULL;
 247 }
 248
 249 void nbd_client_connection_release(NBDClientConnection *conn)
 250 {
 251     bool do_free = false;
 252
 253     if (!conn) {
 254         return;
 255     }
 256
 257     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 258         assert(!conn->detached);
 259         if (conn->running) {
 260             conn->detached = true;
 261         } else {
 262             do_free = true;
 263         }
 264         if (conn->sioc) {
 265             qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
 266                                  QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
 267         }
 268     }
 269
 270     if (do_free) {
 271         nbd_client_connection_do_free(conn);
 272     }
 273 }
 274
 275 /*
 276  * Get a new connection in context of @conn:
 277  *   if the thread is running, wait for completion
 278  *   if the thread already succeeded in the background, and user didn't get the
 279  *     result, just return it now
 280  *   otherwise the thread is not running, so start a thread and wait for
 281  *     completion
 282  *
 283  * If @blocking is false, don't wait for the thread, return immediately.
 284  *
 285  * If @info is not NULL, also do nbd-negotiation after successful connection.
 286  * In this case info is used only as out parameter, and is fully initialized by
 287  * nbd_co_establish_connection(). "IN" fields of info as well as related only to
 288  * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
 289  * include/block/nbd.h).
 290  */
 291 QIOChannel *coroutine_fn
 292 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
 293                             bool blocking, Error **errp)
 294 {
 295     QemuThread thread;
 296
 297     if (conn->do_negotiation) {
 298         assert(info);
 299     }
 300
 301     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 302         /*
 303          * Don't call nbd_co_establish_connection() in several coroutines in
 304          * parallel. Only one call at once is supported.
 305          */
 306         assert(!conn->wait_co);
 307
 308         if (!conn->running) {
 309             if (conn->sioc) {
 310                 /* Previous attempt finally succeeded in background */
 311                 if (conn->do_negotiation) {
 312                     memcpy(info, &conn->updated_info, sizeof(*info));
 313                     if (conn->ioc) {
 314                         /* TLS channel now has own reference to parent */
 315                         object_unref(OBJECT(conn->sioc));
 316                         conn->sioc = NULL;
 317
 318                         return g_steal_pointer(&conn->ioc);
 319                     }
 320                 }
 321
 322                 assert(!conn->ioc);
 323
 324                 return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 325             }
 326
 327             conn->running = true;
 328             qemu_thread_create(&thread, "nbd-connect",
 329                                connect_thread_func, conn, QEMU_THREAD_DETACHED);
 330         }
 331
 332         if (!blocking) {
 333             if (conn->err) {
 334                 error_propagate(errp, error_copy(conn->err));
 335             } else {
 336                 error_setg(errp, "No connection at the moment");
 337             }
 338
 339             return NULL;
 340         }
 341
 342         conn->wait_co = qemu_coroutine_self();
 343     }
 344
 345     /*
 346      * We are going to wait for connect-thread finish, but
 347      * nbd_co_establish_connection_cancel() can interrupt.
 348      */
 349     qemu_coroutine_yield();
 350
 351     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 352         if (conn->running) {
 353             /*
 354              * The connection attempt was canceled and the coroutine resumed
 355              * before the connection thread finished its job.  Report the
 356              * attempt as failed, but leave the connection thread running,
 357              * to reuse it for the next connection attempt.
 358              */
 359             if (conn->err) {
 360                 error_propagate(errp, error_copy(conn->err));
 361             } else {
 362                 /*
 363                  * The only possible case here is cancelling by open_timer
 364                  * during nbd_open(). So, the error message is for that case.
 365                  * If we have more use cases, we can refactor
 366                  * nbd_co_establish_connection_cancel() to take an additional
 367                  * parameter cancel_reason, that would be passed than to the
 368                  * caller of cancelled nbd_co_establish_connection().
 369                  */
 370                 error_setg(errp, "Connection attempt cancelled by timeout");
 371             }
 372
 373             return NULL;
 374         } else {
 375             /* Thread finished. There must be either error or sioc */
 376             assert(!conn->err != !conn->sioc);
 377
 378             if (conn->err) {
 379                 error_propagate(errp, error_copy(conn->err));
 380                 return NULL;
 381             }
 382
 383             if (conn->do_negotiation) {
 384                 memcpy(info, &conn->updated_info, sizeof(*info));
 385                 if (conn->ioc) {
 386                     /* TLS channel now has own reference to parent */
 387                     object_unref(OBJECT(conn->sioc));
 388                     conn->sioc = NULL;
 389
 390                     return g_steal_pointer(&conn->ioc);
 391                 }
 392             }
 393
 394             assert(!conn->ioc);
 395
 396             return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 397         }
 398     }
 399
 400     abort(); /* unreachable */
 401 }
 402
 403 /*
 404  * nbd_co_establish_connection_cancel
 405  * Cancel nbd_co_establish_connection() asynchronously.
 406  *
 407  * Note that this function neither directly stops the thread nor closes the
 408  * socket, but rather safely wakes nbd_co_establish_connection() which is
 409  * sleeping in yield()
 410  */
 411 void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 412 {
 413     Coroutine *wait_co;
 414
 415     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 416         wait_co = g_steal_pointer(&conn->wait_co);
 417     }
 418
 419     if (wait_co) {
 420         aio_co_wake(wait_co);
 421     }
 422 }