qemu

client-connection.c (13168B)

---

 /*
  * QEMU Block driver for  NBD
  *
  * Copyright (c) 2021 Virtuozzo International GmbH.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 
 #include "qemu/osdep.h"
 #include "trace.h"
 
 #include "block/nbd.h"
 
 #include "qapi/qapi-visit-sockets.h"
 #include "qapi/clone-visitor.h"
 
 struct NBDClientConnection {
     /* Initialization constants, never change */
     SocketAddress *saddr; /* address to connect to */
     QCryptoTLSCreds *tlscreds;
     char *tlshostname;
     NBDExportInfo initial_info;
     bool do_negotiation;
     bool do_retry;
 
     QemuMutex mutex;
 
     NBDExportInfo updated_info;
     /*
      * @sioc represents a successful result. While thread is running, @sioc is
      * used only by thread and not protected by mutex. When thread is not
      * running, @sioc is stolen by nbd_co_establish_connection() under mutex.
      */
     QIOChannelSocket *sioc;
     QIOChannel *ioc;
     /*
      * @err represents previous attempt. It may be copied by
      * nbd_co_establish_connection() when it reports failure.
      */
     Error *err;
 
     /* All further fields are accessed only under mutex */
     bool running; /* thread is running now */
     bool detached; /* thread is detached and should cleanup the state */
 
     /*
      * wait_co: if non-NULL, which coroutine to wake in
      * nbd_co_establish_connection() after yield()
      */
     Coroutine *wait_co;
 };
 
 /*
  * The function isn't protected by any mutex, only call it when the client
  * connection attempt has not yet started.
  */
 void nbd_client_connection_enable_retry(NBDClientConnection *conn)
 {
     conn->do_retry = true;
 }
 
 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
                                                bool do_negotiation,
                                                const char *export_name,
                                                const char *x_dirty_bitmap,
                                                QCryptoTLSCreds *tlscreds,
                                                const char *tlshostname)
 {
     NBDClientConnection *conn = g_new(NBDClientConnection, 1);
 
     object_ref(OBJECT(tlscreds));
     *conn = (NBDClientConnection) {
         .saddr = QAPI_CLONE(SocketAddress, saddr),
         .tlscreds = tlscreds,
         .tlshostname = g_strdup(tlshostname),
         .do_negotiation = do_negotiation,
 
         .initial_info.request_sizes = true,
         .initial_info.structured_reply = true,
         .initial_info.base_allocation = true,
         .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
         .initial_info.name = g_strdup(export_name ?: "")
     };
 
     qemu_mutex_init(&conn->mutex);
 
     return conn;
 }
 
 static void nbd_client_connection_do_free(NBDClientConnection *conn)
 {
     if (conn->sioc) {
         qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
         object_unref(OBJECT(conn->sioc));
     }
     error_free(conn->err);
     qapi_free_SocketAddress(conn->saddr);
     g_free(conn->tlshostname);
     object_unref(OBJECT(conn->tlscreds));
     g_free(conn->initial_info.x_dirty_bitmap);
     g_free(conn->initial_info.name);
     g_free(conn);
 }
 
 /*
  * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
  * are given @outioc is returned. @outioc is provided only on success.  The call
  * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
  */
 static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
                        NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
                        const char *tlshostname,
                        QIOChannel **outioc, Error **errp)
 {
     int ret;
 
     if (outioc) {
         *outioc = NULL;
     }
 
     ret = qio_channel_socket_connect_sync(sioc, addr, errp);
     if (ret < 0) {
         return ret;
     }
 
     qio_channel_set_delay(QIO_CHANNEL(sioc), false);
 
     if (!info) {
         return 0;
     }
 
     ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
                                 tlshostname,
                                 outioc, info, errp);
     if (ret < 0) {
         /*
          * nbd_receive_negotiate() may setup tls ioc and return it even on
          * failure path. In this case we should use it instead of original
          * channel.
          */
         if (outioc && *outioc) {
             qio_channel_close(QIO_CHANNEL(*outioc), NULL);
             object_unref(OBJECT(*outioc));
             *outioc = NULL;
         } else {
             qio_channel_close(QIO_CHANNEL(sioc), NULL);
         }
 
         return ret;
     }
 
     return 0;
 }
 
 static void *connect_thread_func(void *opaque)
 {
     NBDClientConnection *conn = opaque;
     int ret;
     bool do_free;
     uint64_t timeout = 1;
     uint64_t max_timeout = 16;
 
     qemu_mutex_lock(&conn->mutex);
     while (!conn->detached) {
         Error *local_err = NULL;
 
         assert(!conn->sioc);
         conn->sioc = qio_channel_socket_new();
 
         qemu_mutex_unlock(&conn->mutex);
 
         conn->updated_info = conn->initial_info;
 
         ret = nbd_connect(conn->sioc, conn->saddr,
                           conn->do_negotiation ? &conn->updated_info : NULL,
                           conn->tlscreds, conn->tlshostname,
                           &conn->ioc, &local_err);
 
         /*
          * conn->updated_info will finally be returned to the user. Clear the
          * pointers to our internally allocated strings, which are IN parameters
          * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
          * shoudn't be interested in these fields.
          */
         conn->updated_info.x_dirty_bitmap = NULL;
         conn->updated_info.name = NULL;
 
         qemu_mutex_lock(&conn->mutex);
 
         error_free(conn->err);
         conn->err = NULL;
         error_propagate(&conn->err, local_err);
 
         if (ret < 0) {
             object_unref(OBJECT(conn->sioc));
             conn->sioc = NULL;
             if (conn->do_retry && !conn->detached) {
                 trace_nbd_connect_thread_sleep(timeout);
                 qemu_mutex_unlock(&conn->mutex);
 
                 sleep(timeout);
                 if (timeout < max_timeout) {
                     timeout *= 2;
                 }
 
                 qemu_mutex_lock(&conn->mutex);
                 continue;
             }
         }
 
         break;
     }
 
     /* mutex is locked */
 
     assert(conn->running);
     conn->running = false;
     if (conn->wait_co) {
         aio_co_wake(conn->wait_co);
         conn->wait_co = NULL;
     }
     do_free = conn->detached;
 
     qemu_mutex_unlock(&conn->mutex);
 
     if (do_free) {
         nbd_client_connection_do_free(conn);
     }
 
     return NULL;
 }
 
 void nbd_client_connection_release(NBDClientConnection *conn)
 {
     bool do_free = false;
 
     if (!conn) {
         return;
     }
 
     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
         assert(!conn->detached);
         if (conn->running) {
             conn->detached = true;
         } else {
             do_free = true;
         }
         if (conn->sioc) {
             qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
                                  QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
         }
     }
 
     if (do_free) {
         nbd_client_connection_do_free(conn);
     }
 }
 
 /*
  * Get a new connection in context of @conn:
  *   if the thread is running, wait for completion
  *   if the thread already succeeded in the background, and user didn't get the
  *     result, just return it now
  *   otherwise the thread is not running, so start a thread and wait for
  *     completion
  *
  * If @blocking is false, don't wait for the thread, return immediately.
  *
  * If @info is not NULL, also do nbd-negotiation after successful connection.
  * In this case info is used only as out parameter, and is fully initialized by
  * nbd_co_establish_connection(). "IN" fields of info as well as related only to
  * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
  * include/block/nbd.h).
  */
 QIOChannel *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
                             bool blocking, Error **errp)
 {
     QemuThread thread;
 
     if (conn->do_negotiation) {
         assert(info);
     }
 
     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
         /*
          * Don't call nbd_co_establish_connection() in several coroutines in
          * parallel. Only one call at once is supported.
          */
         assert(!conn->wait_co);
 
         if (!conn->running) {
             if (conn->sioc) {
                 /* Previous attempt finally succeeded in background */
                 if (conn->do_negotiation) {
                     memcpy(info, &conn->updated_info, sizeof(*info));
                     if (conn->ioc) {
                         /* TLS channel now has own reference to parent */
                         object_unref(OBJECT(conn->sioc));
                         conn->sioc = NULL;
 
                         return g_steal_pointer(&conn->ioc);
                     }
                 }
 
                 assert(!conn->ioc);
 
                 return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
             }
 
             conn->running = true;
             qemu_thread_create(&thread, "nbd-connect",
                                connect_thread_func, conn, QEMU_THREAD_DETACHED);
         }
 
         if (!blocking) {
             if (conn->err) {
                 error_propagate(errp, error_copy(conn->err));
             } else {
                 error_setg(errp, "No connection at the moment");
             }
 
             return NULL;
         }
 
         conn->wait_co = qemu_coroutine_self();
     }
 
     /*
      * We are going to wait for connect-thread finish, but
      * nbd_co_establish_connection_cancel() can interrupt.
      */
     qemu_coroutine_yield();
 
     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
         if (conn->running) {
             /*
              * The connection attempt was canceled and the coroutine resumed
              * before the connection thread finished its job.  Report the
              * attempt as failed, but leave the connection thread running,
              * to reuse it for the next connection attempt.
              */
             if (conn->err) {
                 error_propagate(errp, error_copy(conn->err));
             } else {
                 /*
                  * The only possible case here is cancelling by open_timer
                  * during nbd_open(). So, the error message is for that case.
                  * If we have more use cases, we can refactor
                  * nbd_co_establish_connection_cancel() to take an additional
                  * parameter cancel_reason, that would be passed than to the
                  * caller of cancelled nbd_co_establish_connection().
                  */
                 error_setg(errp, "Connection attempt cancelled by timeout");
             }
 
             return NULL;
         } else {
             /* Thread finished. There must be either error or sioc */
             assert(!conn->err != !conn->sioc);
 
             if (conn->err) {
                 error_propagate(errp, error_copy(conn->err));
                 return NULL;
             }
 
             if (conn->do_negotiation) {
                 memcpy(info, &conn->updated_info, sizeof(*info));
                 if (conn->ioc) {
                     /* TLS channel now has own reference to parent */
                     object_unref(OBJECT(conn->sioc));
                     conn->sioc = NULL;
 
                     return g_steal_pointer(&conn->ioc);
                 }
             }
 
             assert(!conn->ioc);
 
             return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
         }
     }
 
     abort(); /* unreachable */
 }
 
 /*
  * nbd_co_establish_connection_cancel
  * Cancel nbd_co_establish_connection() asynchronously.
  *
  * Note that this function neither directly stops the thread nor closes the
  * socket, but rather safely wakes nbd_co_establish_connection() which is
  * sleeping in yield()
  */
 void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 {
     Coroutine *wait_co;
 
     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
         wait_co = g_steal_pointer(&conn->wait_co);
     }
 
     if (wait_co) {
         aio_co_wake(wait_co);
     }
 }