qemu/nbd/client-connection.c
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   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
  32struct 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 */
  69void nbd_client_connection_enable_retry(NBDClientConnection *conn)
  70{
  71    conn->do_retry = true;
  72}
  73
  74NBDClientConnection *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
 100static 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 */
 119static 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
 163static 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
 235void 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 */
 277QIOChannel *coroutine_fn
 278nbd_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            return NULL;
 322        }
 323
 324        conn->wait_co = qemu_coroutine_self();
 325    }
 326
 327    /*
 328     * We are going to wait for connect-thread finish, but
 329     * nbd_co_establish_connection_cancel() can interrupt.
 330     */
 331    qemu_coroutine_yield();
 332
 333    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 334        if (conn->running) {
 335            /*
 336             * The connection attempt was canceled and the coroutine resumed
 337             * before the connection thread finished its job.  Report the
 338             * attempt as failed, but leave the connection thread running,
 339             * to reuse it for the next connection attempt.
 340             */
 341            error_setg(errp, "Connection attempt cancelled by other operation");
 342            return NULL;
 343        } else {
 344            error_propagate(errp, conn->err);
 345            conn->err = NULL;
 346            if (!conn->sioc) {
 347                return NULL;
 348            }
 349            if (conn->do_negotiation) {
 350                memcpy(info, &conn->updated_info, sizeof(*info));
 351                if (conn->ioc) {
 352                    /* TLS channel now has own reference to parent */
 353                    object_unref(OBJECT(conn->sioc));
 354                    conn->sioc = NULL;
 355
 356                    return g_steal_pointer(&conn->ioc);
 357                }
 358            }
 359
 360            assert(!conn->ioc);
 361
 362            return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
 363        }
 364    }
 365
 366    abort(); /* unreachable */
 367}
 368
 369/*
 370 * nbd_co_establish_connection_cancel
 371 * Cancel nbd_co_establish_connection() asynchronously.
 372 *
 373 * Note that this function neither directly stops the thread nor closes the
 374 * socket, but rather safely wakes nbd_co_establish_connection() which is
 375 * sleeping in yield()
 376 */
 377void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 378{
 379    Coroutine *wait_co;
 380
 381    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
 382        wait_co = g_steal_pointer(&conn->wait_co);
 383    }
 384
 385    if (wait_co) {
 386        aio_co_wake(wait_co);
 387    }
 388}
 389