stuff
[oweals/gnunet.git] / src / util / client.c
index 664b06271091b10feb7b56441a0762deb4fcfdc7..55eb68d13ca2f58cdc2a584c1b7a810f56517b85 100644 (file)
 
 #define DEBUG_CLIENT GNUNET_NO
 
-
 /**
  * How often do we re-try tranmsitting requests before giving up?
  * Note that if we succeeded transmitting a request but failed to read
  * a response, we do NOT re-try.
  */
-#define MAX_ATTEMPTS 10
+#define MAX_ATTEMPTS 50
 
 
 /**
@@ -72,15 +71,15 @@ struct GNUNET_CLIENT_TransmitHandle
   struct GNUNET_CONNECTION_TransmitHandle *th;
 
   /**
-   * Timeout.
+   * If we are re-trying and are delaying to do so,
+   * handle to the scheduled task managing the delay.
    */
-  struct GNUNET_TIME_Absolute timeout;
+  GNUNET_SCHEDULER_TaskIdentifier reconnect_task;
 
   /**
-   * If we are re-trying and are delaying to do so,
-   * handle to the scheduled task managing the delay.
+   * Timeout for the operation overall.
    */
-  GNUNET_SCHEDULER_TaskIdentifier task;
+  struct GNUNET_TIME_Absolute timeout;
 
   /**
    * Number of bytes requested.
@@ -104,6 +103,79 @@ struct GNUNET_CLIENT_TransmitHandle
 };
 
 
+/**
+ * Context for processing 
+ * "GNUNET_CLIENT_transmit_and_get_response" requests.
+ */
+struct TransmitGetResponseContext
+{
+  /**
+   * Client handle.
+   */
+  struct GNUNET_CLIENT_Connection *sock;
+
+  /**
+   * Message to transmit; do not free, allocated
+   * right after this struct.
+   */
+  const struct GNUNET_MessageHeader *hdr;
+
+  /**
+   * Timeout to use.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * Function to call when done.
+   */
+  GNUNET_CLIENT_MessageHandler rn;
+
+  /**
+   * Closure for "rn".
+   */
+  void *rn_cls;
+};
+
+/**
+ * Context for handling the shutdown of a service.
+ */
+struct ShutdownContext
+{
+  /**
+   * Scheduler to be used to call continuation
+   */
+  struct GNUNET_SCHEDULER_Handle *sched;
+  /**
+   * Connection to the service that is being shutdown.
+   */
+  struct GNUNET_CLIENT_Connection *sock;
+
+  /**
+   * Time allowed for shutdown to happen.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * Task set up to cancel the shutdown request on timeout.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier cancel_task;
+
+  /**
+   * Task to call once shutdown complete
+   */
+  GNUNET_CLIENT_ShutdownTask cont;
+
+  /**
+   * Closure for shutdown continuation
+   */
+  void *cont_cls;
+
+  /**
+   * We received a confirmation that the service will shut down.
+   */
+  int confirmed;
+
+};
 
 /**
  * Struct to refer to a GNUnet TCP connection.
@@ -134,6 +206,12 @@ struct GNUNET_CLIENT_Connection
    */
   char *service_name;
 
+  /**
+   * Context of a transmit_and_get_response operation, NULL
+   * if no such operation is pending.
+   */
+  struct TransmitGetResponseContext *tag;
+
   /**
    * Handler for current receiver task.
    */
@@ -155,6 +233,17 @@ struct GNUNET_CLIENT_Connection
    */
   GNUNET_SCHEDULER_Task test_cb;
 
+  /**
+   * Deadline for calling 'test_cb'.
+   */
+  struct GNUNET_TIME_Absolute test_deadline;
+
+  /**
+   * If we are re-trying and are delaying to do so,
+   * handle to the scheduled task managing the delay.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier receive_task;
+
   /**
    * Closure for test_cb (NULL unless in service_test)
    */
@@ -170,6 +259,12 @@ struct GNUNET_CLIENT_Connection
    */
   struct GNUNET_TIME_Absolute receive_timeout;
 
+  /**
+   * Current value for our incremental back-off (for
+   * connect re-tries).
+   */
+  struct GNUNET_TIME_Relative back_off;
+
   /**
    * Number of bytes in received_buf that are valid.
    */
@@ -187,12 +282,15 @@ struct GNUNET_CLIENT_Connection
 
   /**
    * Are we currently busy doing receive-processing?
-   * GNUNET_YES if so, GNUNET_NO if not, GNUNET_SYSERR
-   * if the handle should be destroyed as soon as the
-   * receive processing is done.
+   * GNUNET_YES if so, GNUNET_NO if not.
    */
   int in_receive;
 
+  /**
+   * Are we ignoring shutdown signals?
+   */
+  int ignore_shutdown;
+
 };
 
 
@@ -264,25 +362,25 @@ GNUNET_CLIENT_connect (struct GNUNET_SCHEDULER_Handle *sched,
   ret->sched = sched;
   ret->service_name = GNUNET_strdup (service_name);
   ret->cfg = GNUNET_CONFIGURATION_dup (cfg);
+  ret->back_off = GNUNET_TIME_UNIT_MILLISECONDS;
   return ret;
 }
 
 
 /**
- * Receiver task has completed, free rest of client
- * data structures.
+ * Configure this connection to ignore shutdown signals.
+ *
+ * @param h client handle
+ * @param do_ignore GNUNET_YES to ignore, GNUNET_NO to restore default
  */
-static void
-finish_cleanup (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+void
+GNUNET_CLIENT_ignore_shutdown (struct GNUNET_CLIENT_Connection *h,
+                              int do_ignore)
 {
-  struct GNUNET_CLIENT_Connection *sock = cls;
-
-  if (sock->th != NULL)
-    GNUNET_CLIENT_notify_transmit_ready_cancel (sock->th);
-  GNUNET_array_grow (sock->received_buf, sock->received_size, 0);
-  GNUNET_free (sock->service_name);
-  GNUNET_CONFIGURATION_destroy (sock->cfg);
-  GNUNET_free (sock);
+  h->ignore_shutdown = do_ignore;
+  if (h->sock != NULL)
+    GNUNET_CONNECTION_ignore_shutdown (h->sock,
+                                      do_ignore);
 }
 
 
@@ -292,24 +390,44 @@ finish_cleanup (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
  * *NOT* be called, not even with a NULL message).  Any pending
  * transmission request will also be cancelled UNLESS the callback for
  * the transmission request has already been called, in which case the
- * transmission is guaranteed to complete before the socket is fully
- * destroyed.
+ * transmission 'finish_pending_write' argument determines whether or
+ * not the write is guaranteed to complete before the socket is fully
+ * destroyed (unless, of course, there is an error with the server in
+ * which case the message may still be lost).
  *
+ * @param finish_pending_write should a transmission already passed to the
+ *          handle be completed?
  * @param sock handle to the service connection
  */
 void
-GNUNET_CLIENT_disconnect (struct GNUNET_CLIENT_Connection *sock)
+GNUNET_CLIENT_disconnect (struct GNUNET_CLIENT_Connection *sock,
+                         int finish_pending_write)
 {
   GNUNET_assert (sock->sock != NULL);
-  GNUNET_CONNECTION_destroy (sock->sock);
+  if (sock->in_receive == GNUNET_YES)
+    {
+      GNUNET_CONNECTION_receive_cancel (sock->sock);
+      sock->in_receive = GNUNET_NO;
+    }
+  GNUNET_CONNECTION_destroy (sock->sock, finish_pending_write);
   sock->sock = NULL;
+  if (sock->tag != NULL)
+    {
+      GNUNET_free (sock->tag);
+      sock->tag = NULL;
+    }
   sock->receiver_handler = NULL;
-  if (sock->in_receive == GNUNET_YES)
-    sock->in_receive = GNUNET_SYSERR;
-  else
-    GNUNET_SCHEDULER_add_after (sock->sched,
-                                GNUNET_SCHEDULER_NO_TASK,
-                                &finish_cleanup, sock);
+  if (sock->th != NULL)
+    GNUNET_CLIENT_notify_transmit_ready_cancel (sock->th);
+  if (sock->receive_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (sock->sched, sock->receive_task);
+      sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  GNUNET_array_grow (sock->received_buf, sock->received_size, 0);
+  GNUNET_free (sock->service_name);
+  GNUNET_CONFIGURATION_destroy (sock->cfg);
+  GNUNET_free (sock);
 }
 
 
@@ -347,20 +465,19 @@ receive_helper (void *cls,
 {
   struct GNUNET_CLIENT_Connection *conn = cls;
   struct GNUNET_TIME_Relative remaining;
+  GNUNET_CLIENT_MessageHandler receive_handler;
+  void *receive_handler_cls;
 
   GNUNET_assert (conn->msg_complete == GNUNET_NO);
-  if (GNUNET_SYSERR == conn->in_receive)
-    GNUNET_SCHEDULER_add_after (conn->sched,
-                                GNUNET_SCHEDULER_NO_TASK,
-                                &finish_cleanup, conn);
   conn->in_receive = GNUNET_NO;
   if ((available == 0) || (conn->sock == NULL) || (errCode != 0))
     {
       /* signal timeout! */
-      if (conn->receiver_handler != NULL)
+      if (NULL != (receive_handler = conn->receiver_handler))
         {
-          conn->receiver_handler (conn->receiver_handler_cls, NULL);
+          receive_handler_cls = conn->receiver_handler_cls;
           conn->receiver_handler = NULL;
+          receive_handler (receive_handler_cls, NULL);
         }
       return;
     }
@@ -393,24 +510,23 @@ receive_helper (void *cls,
 
 /**
  * Continuation to call the receive callback.
+ *
+ * @param cls  our handle to the client connection
+ * @param tc scheduler context
  */
 static void
-receive_task (void *scls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+receive_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  struct GNUNET_CLIENT_Connection *sock = scls;
+  struct GNUNET_CLIENT_Connection *sock = cls;
   GNUNET_CLIENT_MessageHandler handler = sock->receiver_handler;
   const struct GNUNET_MessageHeader *cmsg =
     (const struct GNUNET_MessageHeader *) sock->received_buf;
-  void *cls = sock->receiver_handler_cls;
+  void *handler_cls = sock->receiver_handler_cls;
   uint16_t msize = ntohs (cmsg->size);
   char mbuf[msize];
   struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) mbuf;
 
-  if (GNUNET_SYSERR == sock->in_receive)
-    GNUNET_SCHEDULER_add_after (sock->sched,
-                                GNUNET_SCHEDULER_NO_TASK,
-                                &finish_cleanup, sock);
-  sock->in_receive = GNUNET_NO;
+  sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
   GNUNET_assert (GNUNET_YES == sock->msg_complete);
   GNUNET_assert (sock->received_pos >= msize);
   memcpy (msg, cmsg, msize);
@@ -421,7 +537,7 @@ receive_task (void *scls, const struct GNUNET_SCHEDULER_TaskContext *tc)
   sock->receiver_handler = NULL;
   check_complete (sock);
   if (handler != NULL)
-    handler (cls, msg);
+    handler (handler_cls, msg);
 }
 
 
@@ -448,15 +564,107 @@ GNUNET_CLIENT_receive (struct GNUNET_CLIENT_Connection *sock,
   sock->receiver_handler = handler;
   sock->receiver_handler_cls = handler_cls;
   sock->receive_timeout = GNUNET_TIME_relative_to_absolute (timeout);
-  sock->in_receive = GNUNET_YES;
   if (GNUNET_YES == sock->msg_complete)
-    GNUNET_SCHEDULER_add_after (sock->sched,
-                                GNUNET_SCHEDULER_NO_TASK,
-                                &receive_task, sock);
+    {
+      sock->receive_task = GNUNET_SCHEDULER_add_after (sock->sched,
+                                                       GNUNET_SCHEDULER_NO_TASK,
+                                                       &receive_task, sock);
+    }
   else
-    GNUNET_CONNECTION_receive (sock->sock,
-                               GNUNET_SERVER_MAX_MESSAGE_SIZE,
-                               timeout, &receive_helper, sock);
+    {
+      sock->in_receive = GNUNET_YES;
+      GNUNET_CONNECTION_receive (sock->sock,
+                                 GNUNET_SERVER_MAX_MESSAGE_SIZE,
+                                 timeout, &receive_helper, sock);
+    }
+}
+
+
+/**
+ * Handler receiving response to service shutdown requests.
+ * First call with NULL: service misbehaving, or something.
+ * First call with GNUNET_MESSAGE_TYPE_SHUTDOWN_ACK:
+ *   - service will shutdown
+ * First call with GNUNET_MESSAGE_TYPE_SHUTDOWN_REFUSE:
+ *   - service will not be stopped!
+ *
+ * Second call with NULL:
+ *   - service has now really shut down.
+ *
+ * @param cls closure
+ * @param msg NULL, indicating socket closure.
+ */
+static void
+service_shutdown_handler (void *cls, const struct GNUNET_MessageHeader *msg)
+{
+  struct ShutdownContext *shutdown_ctx = cls;
+
+  if ((msg == NULL) && (shutdown_ctx->confirmed != GNUNET_YES))   
+    {
+      /* Means the other side closed the connection and never confirmed a shutdown */
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, 
+                 "Service handle shutdown before ACK!\n");
+      if (shutdown_ctx->cont != NULL)
+        shutdown_ctx->cont(shutdown_ctx->cont_cls, GNUNET_SYSERR);      
+      GNUNET_SCHEDULER_cancel(shutdown_ctx->sched, shutdown_ctx->cancel_task);
+      GNUNET_CLIENT_disconnect (shutdown_ctx->sock, GNUNET_NO);
+      GNUNET_free(shutdown_ctx);
+    }
+  else if ((msg == NULL) && (shutdown_ctx->confirmed == GNUNET_YES))
+    {
+      GNUNET_log(GNUNET_ERROR_TYPE_WARNING, 
+                "Service shutdown complete.\n");
+      if (shutdown_ctx->cont != NULL)
+        shutdown_ctx->cont(shutdown_ctx->cont_cls, GNUNET_NO);
+
+      GNUNET_SCHEDULER_cancel(shutdown_ctx->sched, shutdown_ctx->cancel_task);
+      GNUNET_CLIENT_disconnect (shutdown_ctx->sock, GNUNET_NO);
+      GNUNET_free(shutdown_ctx);
+    }
+  else
+    {
+      GNUNET_assert(ntohs(msg->size) == sizeof(struct GNUNET_MessageHeader));
+
+      switch (ntohs(msg->type))
+      {
+      case GNUNET_MESSAGE_TYPE_SHUTDOWN_ACK:
+        GNUNET_log(GNUNET_ERROR_TYPE_WARNING,
+                  "Received confirmation for service shutdown.\n");
+        shutdown_ctx->confirmed = GNUNET_YES;
+        GNUNET_CLIENT_receive (shutdown_ctx->sock, 
+                              &service_shutdown_handler, 
+                              shutdown_ctx, 
+                              GNUNET_TIME_UNIT_FOREVER_REL);
+        break;
+      case GNUNET_MESSAGE_TYPE_SHUTDOWN_REFUSE:
+      default: /* Fall through */
+        GNUNET_log(GNUNET_ERROR_TYPE_WARNING, 
+                  "Service shutdown refused!\n");
+        if (shutdown_ctx->cont != NULL)
+          shutdown_ctx->cont(shutdown_ctx->cont_cls, GNUNET_YES);
+
+        GNUNET_SCHEDULER_cancel(shutdown_ctx->sched, shutdown_ctx->cancel_task);
+        GNUNET_CLIENT_disconnect (shutdown_ctx->sock, GNUNET_NO);
+        GNUNET_free(shutdown_ctx);
+        break;
+      }
+    }
+}
+
+/**
+ * Shutting down took too long, cancel receive and return error.
+ *
+ * @param cls closure
+ * @param tc context information (why was this task triggered now)
+ */
+void service_shutdown_cancel (void *cls,
+                              const struct GNUNET_SCHEDULER_TaskContext * tc)
+{
+  struct ShutdownContext *shutdown_ctx = cls;
+  GNUNET_log(GNUNET_ERROR_TYPE_WARNING, "service_shutdown_cancel called!\n");
+  shutdown_ctx->cont(shutdown_ctx->cont_cls, GNUNET_SYSERR);
+  GNUNET_CLIENT_disconnect (shutdown_ctx->sock, GNUNET_NO);
+  GNUNET_free(shutdown_ctx);
 }
 
 
@@ -473,15 +681,25 @@ static size_t
 write_shutdown (void *cls, size_t size, void *buf)
 {
   struct GNUNET_MessageHeader *msg;
-  struct GNUNET_CLIENT_Connection *sock = cls;
+  struct ShutdownContext *shutdown_ctx = cls;
 
-  GNUNET_CLIENT_disconnect (sock);
   if (size < sizeof (struct GNUNET_MessageHeader))
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                   _("Failed to transmit shutdown request to client.\n"));
+      shutdown_ctx->cont(shutdown_ctx->cont_cls, GNUNET_SYSERR);
+      GNUNET_CLIENT_disconnect (shutdown_ctx->sock, GNUNET_NO);
+      GNUNET_free(shutdown_ctx);
       return 0;                 /* client disconnected */
     }
+
+  GNUNET_CLIENT_receive (shutdown_ctx->sock,
+                        &service_shutdown_handler, shutdown_ctx, 
+                        GNUNET_TIME_UNIT_FOREVER_REL);
+  shutdown_ctx->cancel_task = GNUNET_SCHEDULER_add_delayed (shutdown_ctx->sched, 
+                                                           GNUNET_TIME_absolute_get_remaining(shutdown_ctx->timeout), 
+                                                           &service_shutdown_cancel, 
+                                                           shutdown_ctx);
   msg = (struct GNUNET_MessageHeader *) buf;
   msg->type = htons (GNUNET_MESSAGE_TYPE_SHUTDOWN);
   msg->size = htons (sizeof (struct GNUNET_MessageHeader));
@@ -491,18 +709,37 @@ write_shutdown (void *cls, size_t size, void *buf)
 
 /**
  * Request that the service should shutdown.
- * Afterwards, the connection should be disconnected.
+ * Afterwards, the connection will automatically be
+ * disconnected.  Hence the "sock" should not
+ * be used by the caller after this call
+ * (calling this function frees "sock" after a while).
  *
+ * @param sched the scheduler to use for calling shutdown continuation
  * @param sock the socket connected to the service
+ * @param timeout how long to wait before giving up on transmission
+ * @param cont continuation to call once the service is really down
+ * @param cont_cls closure for continuation
+ *
  */
 void
-GNUNET_CLIENT_service_shutdown (struct GNUNET_CLIENT_Connection *sock)
+GNUNET_CLIENT_service_shutdown (struct GNUNET_SCHEDULER_Handle *sched,
+                                struct GNUNET_CLIENT_Connection *sock,
+                                struct GNUNET_TIME_Relative timeout,
+                                GNUNET_CLIENT_ShutdownTask cont,
+                                void *cont_cls)
 {
+  struct ShutdownContext *shutdown_ctx;
+  shutdown_ctx = GNUNET_malloc(sizeof(struct ShutdownContext));
+  shutdown_ctx->sched = sched;
+  shutdown_ctx->cont = cont;
+  shutdown_ctx->cont_cls = cont_cls;
+  shutdown_ctx->sock = sock;
+  shutdown_ctx->timeout = GNUNET_TIME_relative_to_absolute(timeout);
   GNUNET_CONNECTION_notify_transmit_ready (sock->sock,
                                            sizeof (struct
                                                    GNUNET_MessageHeader),
-                                           GNUNET_TIME_UNIT_FOREVER_REL,
-                                           &write_shutdown, sock);
+                                           timeout,
+                                           &write_shutdown, shutdown_ctx);
 }
 
 
@@ -548,13 +785,14 @@ confirm_handler (void *cls, const struct GNUNET_MessageHeader *msg)
     {
       service_test_error (conn->sched, conn->test_cb, conn->test_cb_cls);
     }
-  GNUNET_CLIENT_disconnect (conn);
+  GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
 }
 
 
 static size_t
 write_test (void *cls, size_t size, void *buf)
 {
+  struct GNUNET_CLIENT_Connection *conn = cls;
   struct GNUNET_MessageHeader *msg;
 
   if (size < sizeof (struct GNUNET_MessageHeader))
@@ -563,16 +801,21 @@ write_test (void *cls, size_t size, void *buf)
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   _("Failure to transmit TEST request.\n"));
 #endif
+      service_test_error (conn->sched, conn->test_cb, conn->test_cb_cls);
+      GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
       return 0;                 /* client disconnected */
     }
 #if DEBUG_CLIENT
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Transmitting `%s' request.\n",
-             "TEST");
+              "Transmitting `%s' request.\n", "TEST");
 #endif
   msg = (struct GNUNET_MessageHeader *) buf;
   msg->type = htons (GNUNET_MESSAGE_TYPE_TEST);
   msg->size = htons (sizeof (struct GNUNET_MessageHeader));
+  GNUNET_CLIENT_receive (conn, 
+                        &confirm_handler, 
+                        conn, 
+                        GNUNET_TIME_absolute_get_remaining (conn->test_deadline));
   return sizeof (struct GNUNET_MessageHeader);
 }
 
@@ -614,20 +857,21 @@ GNUNET_CLIENT_service_test (struct GNUNET_SCHEDULER_Handle *sched,
     }
   conn->test_cb = task;
   conn->test_cb_cls = task_cls;
-  if (NULL ==
-      GNUNET_CONNECTION_notify_transmit_ready (conn->sock,
-                                               sizeof (struct
-                                                       GNUNET_MessageHeader),
-                                               timeout, &write_test, NULL))
+  conn->test_deadline = GNUNET_TIME_relative_to_absolute (timeout);
+
+  if (NULL == GNUNET_CLIENT_notify_transmit_ready (conn,
+                                                  sizeof (struct GNUNET_MessageHeader),
+                                                  timeout,
+                                                  GNUNET_YES,
+                                                  &write_test, conn))  
     {
       GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                   _("Failure to transmit request to service `%s'\n"),
                   service);
       service_test_error (sched, task, task_cls);
-      GNUNET_CLIENT_disconnect (conn);
+      GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
       return;
     }
-  GNUNET_CLIENT_receive (conn, &confirm_handler, conn, timeout);
 }
 
 
@@ -657,13 +901,14 @@ client_delayed_retry (void *cls,
 {
   struct GNUNET_CLIENT_TransmitHandle *th = cls;
 
-  th->task = GNUNET_SCHEDULER_NO_TASK;
+  th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
   if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
     {
 #if DEBUG_CLIENT
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Transmission failed due to shutdown.\n");
+                  "Transmission failed due to shutdown.\n");
 #endif
+      th->sock->th = NULL;
       th->notify (th->notify_cls, 0, NULL);
       GNUNET_free (th);
       return;
@@ -684,9 +929,8 @@ client_delayed_retry (void *cls,
 
 
 /**
- * Connection notifies us about failure or success of
- * a transmission request.  Either pass it on to our
- * user or, if possible, retry.
+ * Connection notifies us about failure or success of a transmission
+ * request.  Either pass it on to our user or, if possible, retry.
  *
  * @param cls our "struct GNUNET_CLIENT_TransmissionHandle"
  * @param size number of bytes available for transmission
@@ -704,38 +948,43 @@ client_notify (void *cls, size_t size, void *buf)
   th->sock->th = NULL;
   if (buf == NULL)
     {
-      // FIXME: need a way to check if the
-      // reason is SHUTDOWN (not timeout) and
-      // if so NOT retry!
       delay = GNUNET_TIME_absolute_get_remaining (th->timeout);
       delay.value /= 2;
-      if ((GNUNET_YES != th->auto_retry) ||
-          (0 == --th->attempts_left) || (delay.value < 1))
+      if ( (0 != (GNUNET_SCHEDULER_REASON_SHUTDOWN & GNUNET_SCHEDULER_get_reason (th->sock->sched))) ||
+          (GNUNET_YES != th->auto_retry) ||
+          (0 == --th->attempts_left) || 
+          (delay.value < 1) )
         {
 #if DEBUG_CLIENT
-         GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                     "Transmission failed %u times, giving up.\n",
-                     MAX_ATTEMPTS - th->attempts_left);
+          GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                      "Transmission failed %u times, giving up.\n",
+                      MAX_ATTEMPTS - th->attempts_left);
 #endif
           GNUNET_break (0 == th->notify (th->notify_cls, 0, NULL));
           GNUNET_free (th);
           return 0;
         }
       /* auto-retry */
-      GNUNET_CONNECTION_destroy (th->sock->sock);
+      GNUNET_CONNECTION_destroy (th->sock->sock, GNUNET_NO);
       th->sock->sock = do_connect (th->sock->sched,
                                    th->sock->service_name, th->sock->cfg);
       GNUNET_assert (NULL != th->sock->sock);
-      delay = GNUNET_TIME_relative_min (delay, GNUNET_TIME_UNIT_SECONDS);
+      GNUNET_CONNECTION_ignore_shutdown (th->sock->sock,
+                                        th->sock->ignore_shutdown);
+      delay = GNUNET_TIME_relative_min (delay, th->sock->back_off);
+      th->sock->back_off 
+         = GNUNET_TIME_relative_min (GNUNET_TIME_relative_multiply (th->sock->back_off, 2),
+                                   GNUNET_TIME_UNIT_SECONDS);
 #if DEBUG_CLIENT
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Transmission failed %u times, trying again in %llums.\n",
-                 MAX_ATTEMPTS - th->attempts_left,
-                 (unsigned long long) delay.value);
+                  "Transmission failed %u times, trying again in %llums.\n",
+                  MAX_ATTEMPTS - th->attempts_left,
+                  (unsigned long long) delay.value);
 #endif
-      th->task = GNUNET_SCHEDULER_add_delayed (th->sock->sched,
-                                               delay,
-                                               &client_delayed_retry, th);
+      th->reconnect_task = GNUNET_SCHEDULER_add_delayed (th->sock->sched,
+                                                         delay,
+                                                         &client_delayed_retry,
+                                                         th);
       th->sock->th = th;
       return 0;
     }
@@ -809,10 +1058,11 @@ void
 GNUNET_CLIENT_notify_transmit_ready_cancel (struct
                                             GNUNET_CLIENT_TransmitHandle *th)
 {
-  if (th->task != GNUNET_SCHEDULER_NO_TASK)
+  if (th->reconnect_task != GNUNET_SCHEDULER_NO_TASK)
     {
       GNUNET_break (NULL == th->th);
-      GNUNET_SCHEDULER_cancel (th->sock->sched, th->task);
+      GNUNET_SCHEDULER_cancel (th->sock->sched, th->reconnect_task);
+      th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
     }
   else
     {
@@ -824,47 +1074,13 @@ GNUNET_CLIENT_notify_transmit_ready_cancel (struct
 }
 
 
-/**
- * Context for processing 
- * "GNUNET_CLIENT_transmit_and_get_response" requests.
- */
-struct TARCtx
-{
-  /**
-   * Client handle.
-   */
-  struct GNUNET_CLIENT_Connection *sock;
-
-  /**
-   * Message to transmit; do not free, allocated
-   * right after this struct.
-   */
-  const struct GNUNET_MessageHeader *hdr;
-
-  /**
-   * Timeout to use.
-   */
-  struct GNUNET_TIME_Absolute timeout;
-
-  /**
-   * Function to call when done.
-   */
-  GNUNET_CLIENT_MessageHandler rn;
-
-  /**
-   * Closure for "rn".
-   */
-  void *rn_cls;
-};
-
-
 /**
  * Function called to notify a client about the socket
  * begin ready to queue the message.  "buf" will be
  * NULL and "size" zero if the socket was closed for
  * writing in the meantime.
  *
- * @param cls closure of type "struct TARCtx*"
+ * @param cls closure of type "struct TransmitGetResponseContext*"
  * @param size number of bytes available in buf
  * @param buf where the callee should write the message
  * @return number of bytes written to buf
@@ -872,12 +1088,17 @@ struct TARCtx
 static size_t
 transmit_for_response (void *cls, size_t size, void *buf)
 {
-  struct TARCtx *tc = cls;
+  struct TransmitGetResponseContext *tc = cls;
   uint16_t msize;
 
+  tc->sock->tag = NULL;
   msize = ntohs (tc->hdr->size);
   if (NULL == buf)
     {
+#if DEBUG_CLIENT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 _("Could not submit request, not expecting to receive a response.\n"));
+#endif
       tc->rn (tc->rn_cls, NULL);
       GNUNET_free (tc);
       return 0;
@@ -924,13 +1145,14 @@ GNUNET_CLIENT_transmit_and_get_response (struct GNUNET_CLIENT_Connection
                                          GNUNET_CLIENT_MessageHandler rn,
                                          void *rn_cls)
 {
-  struct TARCtx *tc;
+  struct TransmitGetResponseContext *tc;
   uint16_t msize;
 
   if (NULL != sock->th)
     return GNUNET_SYSERR;
+  GNUNET_assert (sock->tag == NULL);
   msize = ntohs (hdr->size);
-  tc = GNUNET_malloc (sizeof (struct TARCtx) + msize);
+  tc = GNUNET_malloc (sizeof (struct TransmitGetResponseContext) + msize);
   tc->sock = sock;
   tc->hdr = (const struct GNUNET_MessageHeader *) &tc[1];
   memcpy (&tc[1], hdr, msize);
@@ -948,6 +1170,7 @@ GNUNET_CLIENT_transmit_and_get_response (struct GNUNET_CLIENT_Connection
       GNUNET_free (tc);
       return GNUNET_SYSERR;
     }
+  sock->tag = tc;
   return GNUNET_OK;
 }