X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fmq.c;h=14e0816e28b3f2aa6e989320ed1ff463321bbf79;hb=34f34474b6137233d6700d4599f42257e8208af2;hp=36cacd30b0e0499fc6e5db571d72d21fd9d4b611;hpb=4289fca5aeefd0652ae60bc16f90ed911c7e1c60;p=oweals%2Fgnunet.git

diff --git a/src/util/mq.c b/src/util/mq.c
index 36cacd30b..14e0816e2 100644
--- a/src/util/mq.c
+++ b/src/util/mq.c
@@ -1,10 +1,10 @@
 /*
      This file is part of GNUnet.
-     (C) 2012 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2012-2014 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 2, or (at your
+     by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
@@ -23,66 +23,240 @@
  * @file util/mq.c
  * @brief general purpose request queue
  */
-
 #include "platform.h"
-#include "gnunet_common.h"
 #include "gnunet_util_lib.h"
 
 #define LOG(kind,...) GNUNET_log_from (kind, "mq",__VA_ARGS__)
 
 
+struct GNUNET_MQ_Envelope
+{
+  /**
+   * Messages are stored in a linked list.
+   * Each queue has its own list of envelopes.
+   */
+  struct GNUNET_MQ_Envelope *next;
+
+  /**
+   * Messages are stored in a linked list
+   * Each queue has its own list of envelopes.
+   */
+  struct GNUNET_MQ_Envelope *prev;
+
+  /**
+   * Actual allocated message header,
+   * usually points to the end of the containing GNUNET_MQ_Envelope
+   */
+  struct GNUNET_MessageHeader *mh;
+
+  /**
+   * Queue the message is queued in, NULL if message is not queued.
+   */
+  struct GNUNET_MQ_Handle *parent_queue;
+
+  /**
+   * Called after the message was sent irrevocably.
+   */
+  GNUNET_MQ_NotifyCallback sent_cb;
+
+  /**
+   * Closure for @e send_cb
+   */
+  void *sent_cls;
+};
+
+
+/**
+ * Handle to a message queue.
+ */
+struct GNUNET_MQ_Handle
+{
+  /**
+   * Handlers array, or NULL if the queue should not receive messages
+   */
+  const struct GNUNET_MQ_MessageHandler *handlers;
+
+  /**
+   * Closure for the handler callbacks,
+   * as well as for the error handler.
+   */
+  void *handlers_cls;
+
+  /**
+   * Actual implementation of message sending,
+   * called when a message is added
+   */
+  GNUNET_MQ_SendImpl send_impl;
+
+  /**
+   * Implementation-dependent queue destruction function
+   */
+  GNUNET_MQ_DestroyImpl destroy_impl;
+
+  /**
+   * Implementation-dependent send cancel function
+   */
+  GNUNET_MQ_CancelImpl cancel_impl;
+
+  /**
+   * Implementation-specific state
+   */
+  void *impl_state;
 
+  /**
+   * Callback will be called when an error occurs.
+   */
+  GNUNET_MQ_ErrorHandler error_handler;
+
+  /**
+   * Linked list of messages pending to be sent
+   */
+  struct GNUNET_MQ_Envelope *envelope_head;
+
+  /**
+   * Linked list of messages pending to be sent
+   */
+  struct GNUNET_MQ_Envelope *envelope_tail;
+
+  /**
+   * Message that is currently scheduled to be
+   * sent. Not the head of the message queue, as the implementation
+   * needs to know if sending has been already scheduled or not.
+   */
+  struct GNUNET_MQ_Envelope *current_envelope;
+
+  /**
+   * Map of associations, lazily allocated
+   */
+  struct GNUNET_CONTAINER_MultiHashMap32 *assoc_map;
+
+  /**
+   * Task scheduled during #GNUNET_MQ_impl_send_continue.
+   */
+  struct GNUNET_SCHEDULER_Task * continue_task;
+
+  /**
+   * Next id that should be used for the @e assoc_map,
+   * initialized lazily to a random value together with
+   * @e assoc_map
+   */
+  uint32_t assoc_id;
+};
+
+
+/**
+ * Implementation-specific state for connection to
+ * client (MQ for server).
+ */
 struct ServerClientSocketState
 {
+  /**
+   * Handle of the client that connected to the server.
+   */
   struct GNUNET_SERVER_Client *client;
+
+  /**
+   * Active transmission request to the client.
+   */
   struct GNUNET_SERVER_TransmitHandle* th;
 };
 
 
+/**
+ * Implementation-specific state for connection to
+ * service (MQ for clients).
+ */
 struct ClientConnectionState
 {
   /**
-   * Did we call receive?
+   * Did we call receive alread alreadyy?
    */
   int receive_active;
+
+  /**
+   * Do we also want to receive?
+   */
+  int receive_requested;
+
+  /**
+   * Connection to the service.
+   */
   struct GNUNET_CLIENT_Connection *connection;
+
+  /**
+   * Active transmission request (or NULL).
+   */
   struct GNUNET_CLIENT_TransmitHandle *th;
 };
 
 
-
-
 /**
- * Call the right callback for a message.
+ * Call the message message handler that was registered
+ * for the type of the given message in the given message queue.
+ *
+ * This function is indended to be used for the implementation
+ * of message queues.
  *
  * @param mq message queue with the handlers
  * @param mh message to dispatch
  */
 void
-GNUNET_MQ_dispatch (struct GNUNET_MQ_MessageQueue *mq, const struct GNUNET_MessageHeader *mh)
+GNUNET_MQ_inject_message (struct GNUNET_MQ_Handle *mq,
+                          const struct GNUNET_MessageHeader *mh)
 {
-  const struct GNUNET_MQ_Handler *handler;
+  const struct GNUNET_MQ_MessageHandler *handler;
   int handled = GNUNET_NO;
 
-  handler = mq->handlers;
-  if (NULL == handler)
+  if (NULL == mq->handlers)
+  {
+    LOG (GNUNET_ERROR_TYPE_WARNING,
+         "No handler for message of type %d\n",
+         ntohs (mh->type));
     return;
-  for (; NULL != handler->cb; handler++)
+  }
+  for (handler = mq->handlers; NULL != handler->cb; handler++)
   {
     if (handler->type == ntohs (mh->type))
     {
       handler->cb (mq->handlers_cls, mh);
       handled = GNUNET_YES;
+      break;
     }
   }
-  
   if (GNUNET_NO == handled)
-    LOG (GNUNET_ERROR_TYPE_WARNING, "no handler for message of type %d\n", ntohs (mh->type));
+    LOG (GNUNET_ERROR_TYPE_WARNING,
+         "No handler for message of type %d\n",
+         ntohs (mh->type));
 }
 
 
+/**
+ * Call the error handler of a message queue with the given
+ * error code.  If there is no error handler, log a warning.
+ *
+ * This function is intended to be used by the implementation
+ * of message queues.
+ *
+ * @param mq message queue
+ * @param error the error type
+ */
 void
-GNUNET_MQ_discard (struct GNUNET_MQ_Message *mqm)
+GNUNET_MQ_inject_error (struct GNUNET_MQ_Handle *mq,
+                        enum GNUNET_MQ_Error error)
+{
+  if (NULL == mq->error_handler)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "mq: got error %d, but no handler installed\n",
+                (int) error);
+    return;
+  }
+  mq->error_handler (mq->handlers_cls, error);
+}
+
+
+void
+GNUNET_MQ_discard (struct GNUNET_MQ_Envelope *mqm)
 {
   GNUNET_assert (NULL == mqm->parent_queue);
   GNUNET_free (mqm);
@@ -92,22 +266,172 @@ GNUNET_MQ_discard (struct GNUNET_MQ_Message *mqm)
 /**
  * Send a message with the give message queue.
  * May only be called once per message.
- * 
+ *
  * @param mq message queue
- * @param mqm the message to send.
+ * @param ev the envelope with the message to send.
  */
 void
-GNUNET_MQ_send (struct GNUNET_MQ_MessageQueue *mq, struct GNUNET_MQ_Message *mqm)
+GNUNET_MQ_send (struct GNUNET_MQ_Handle *mq,
+                struct GNUNET_MQ_Envelope *ev)
 {
   GNUNET_assert (NULL != mq);
-  mq->send_impl (mq, mqm);
+  GNUNET_assert (NULL == ev->parent_queue);
+
+  ev->parent_queue = mq;
+  /* is the implementation busy? queue it! */
+  if (NULL != mq->current_envelope)
+  {
+    GNUNET_CONTAINER_DLL_insert_tail (mq->envelope_head,
+                                      mq->envelope_tail,
+                                      ev);
+    return;
+  }
+  mq->current_envelope = ev;
+  mq->send_impl (mq, ev->mh, mq->impl_state);
+}
+
+
+/**
+ * Task run to call the send implementation for the next queued
+ * message, if any.  Only useful for implementing message queues,
+ * results in undefined behavior if not used carefully.
+ *
+ * @param cls message queue to send the next message with
+ * @param tc scheduler context
+ */
+static void
+impl_send_continue (void *cls,
+                    const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_MQ_Handle *mq = cls;
+  struct GNUNET_MQ_Envelope *current_envelope;
+
+  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;
+
+  mq->continue_task = NULL;
+  /* call is only valid if we're actually currently sending
+   * a message */
+  current_envelope = mq->current_envelope;
+  GNUNET_assert (NULL != current_envelope);
+  current_envelope->parent_queue = NULL;
+  if (NULL == mq->envelope_head)
+  {
+    mq->current_envelope = NULL;
+  }
+  else
+  {
+    mq->current_envelope = mq->envelope_head;
+    GNUNET_CONTAINER_DLL_remove (mq->envelope_head,
+                                 mq->envelope_tail,
+                                 mq->current_envelope);
+    mq->send_impl (mq, mq->current_envelope->mh, mq->impl_state);
+  }
+  if (NULL != current_envelope->sent_cb)
+    current_envelope->sent_cb (current_envelope->sent_cls);
+  GNUNET_free (current_envelope);
 }
 
 
-struct GNUNET_MQ_Message *
-GNUNET_MQ_msg_ (struct GNUNET_MessageHeader **mhp, uint16_t size, uint16_t type)
+/**
+ * Call the send implementation for the next queued message,
+ * if any.
+ * Only useful for implementing message queues,
+ * results in undefined behavior if not used carefully.
+ *
+ * @param mq message queue to send the next message with
+ */
+void
+GNUNET_MQ_impl_send_continue (struct GNUNET_MQ_Handle *mq)
 {
-  struct GNUNET_MQ_Message *mqm;
+  GNUNET_assert (NULL == mq->continue_task);
+  mq->continue_task = GNUNET_SCHEDULER_add_now (&impl_send_continue,
+                                                mq);
+}
+
+
+/**
+ * Create a message queue for the specified handlers.
+ *
+ * @param send function the implements sending messages
+ * @param destroy function that implements destroying the queue
+ * @param cancel function that implements canceling a message
+ * @param impl_state for the queue, passed to 'send' and 'destroy'
+ * @param handlers array of message handlers
+ * @param error_handler handler for read and write errors
+ * @param cls closure for message handlers and error handler
+ * @return a new message queue
+ */
+struct GNUNET_MQ_Handle *
+GNUNET_MQ_queue_for_callbacks (GNUNET_MQ_SendImpl send,
+                               GNUNET_MQ_DestroyImpl destroy,
+                               GNUNET_MQ_CancelImpl cancel,
+                               void *impl_state,
+                               const struct GNUNET_MQ_MessageHandler *handlers,
+                               GNUNET_MQ_ErrorHandler error_handler,
+                               void *cls)
+{
+  struct GNUNET_MQ_Handle *mq;
+
+  mq = GNUNET_new (struct GNUNET_MQ_Handle);
+  mq->send_impl = send;
+  mq->destroy_impl = destroy;
+  mq->cancel_impl = cancel;
+  mq->handlers = handlers;
+  mq->handlers_cls = cls;
+  mq->impl_state = impl_state;
+
+  return mq;
+}
+
+
+/**
+ * Get the message that should currently be sent.
+ * Fails if there is no current message.
+ * Only useful for implementing message queues,
+ * results in undefined behavior if not used carefully.
+ *
+ * @param mq message queue with the current message
+ * @return message to send, never NULL
+ */
+const struct GNUNET_MessageHeader *
+GNUNET_MQ_impl_current (struct GNUNET_MQ_Handle *mq)
+{
+  if (NULL == mq->current_envelope)
+    GNUNET_assert (0);
+  if (NULL == mq->current_envelope->mh)
+    GNUNET_assert (0);
+  return mq->current_envelope->mh;
+}
+
+
+/**
+ * Get the implementation state associated with the
+ * message queue.
+ *
+ * While the GNUNET_MQ_Impl* callbacks receive the
+ * implementation state, continuations that are scheduled
+ * by the implementation function often only have one closure
+ * argument, with this function it is possible to get at the
+ * implementation state when only passing the GNUNET_MQ_Handle
+ * as closure.
+ *
+ * @param mq message queue with the current message
+ * @return message to send, never NULL
+ */
+void *
+GNUNET_MQ_impl_state (struct GNUNET_MQ_Handle *mq)
+{
+  return mq->impl_state;
+}
+
+
+struct GNUNET_MQ_Envelope *
+GNUNET_MQ_msg_ (struct GNUNET_MessageHeader **mhp,
+                uint16_t size,
+                uint16_t type)
+{
+  struct GNUNET_MQ_Envelope *mqm;
 
   mqm = GNUNET_malloc (sizeof *mqm + size);
   mqm->mh = (struct GNUNET_MessageHeader *) &mqm[1];
@@ -119,33 +443,42 @@ GNUNET_MQ_msg_ (struct GNUNET_MessageHeader **mhp, uint16_t size, uint16_t type)
 }
 
 
-int
-GNUNET_MQ_nest_ (struct GNUNET_MQ_Message **mqmp,
-                 const void *data, uint16_t len)
-{
-  size_t new_size;
-  size_t old_size;
-
-  GNUNET_assert (NULL != mqmp);
-  /* there's no data to append => do nothing */
-  if (NULL == data)
-    return GNUNET_OK;
-  old_size = ntohs ((*mqmp)->mh->size);
-  /* message too large to concatenate? */
-  if (((uint16_t) (old_size + len)) < len)
-    return GNUNET_SYSERR;
-  new_size = old_size + len;
-  *mqmp = GNUNET_realloc (*mqmp, sizeof (struct GNUNET_MQ_Message) + new_size);
-  (*mqmp)->mh = (struct GNUNET_MessageHeader *) &(*mqmp)[1];
-  memcpy (((void *) (*mqmp)->mh) + old_size, data, new_size - old_size);
-  (*mqmp)->mh->size = htons (new_size);
-  return GNUNET_OK;
-}
+/**
+ * Implementation of the GNUNET_MQ_msg_nested_mh macro.
+ *
+ * @param mhp pointer to the message header pointer that will be changed to allocate at
+ *        the newly allocated space for the message.
+ * @param base_size size of the data before the nested message
+ * @param type type of the message in the envelope
+ * @param nested_mh the message to append to the message after base_size
+ */
+struct GNUNET_MQ_Envelope *
+GNUNET_MQ_msg_nested_mh_ (struct GNUNET_MessageHeader **mhp,
+                          uint16_t base_size,
+                          uint16_t type,
+                          const struct GNUNET_MessageHeader *nested_mh)
+{
+  struct GNUNET_MQ_Envelope *mqm;
+  uint16_t size;
 
+  if (NULL == nested_mh)
+    return GNUNET_MQ_msg_ (mhp, base_size, type);
 
+  size = base_size + ntohs (nested_mh->size);
+
+  /* check for uint16_t overflow */
+  if (size < base_size)
+    return NULL;
 
+  mqm = GNUNET_MQ_msg_ (mhp, size, type);
+  memcpy ((char *) mqm->mh + base_size, nested_mh, ntohs (nested_mh->size));
 
-/*** Transmit a queued message to the session's client.
+  return mqm;
+}
+
+
+/**
+ * Transmit a queued message to the session's client.
  *
  * @param cls consensus session
  * @param size number of bytes available in buf
@@ -156,85 +489,66 @@ static size_t
 transmit_queued (void *cls, size_t size,
                  void *buf)
 {
-  struct GNUNET_MQ_MessageQueue *mq = cls;
-  struct GNUNET_MQ_Message *mqm = mq->current_msg;
-  struct ServerClientSocketState *state = mq->impl_state;
+  struct GNUNET_MQ_Handle *mq = cls;
+  struct ServerClientSocketState *state = GNUNET_MQ_impl_state (mq);
+  const struct GNUNET_MessageHeader *msg = GNUNET_MQ_impl_current (mq);
   size_t msg_size;
 
   GNUNET_assert (NULL != buf);
 
-  if (NULL != mqm->sent_cb)
-  {
-    mqm->sent_cb (mqm->sent_cls);
-  }
-
-  mq->current_msg = NULL;
-  GNUNET_assert (NULL != mqm);
-  msg_size = ntohs (mqm->mh->size);
+  msg_size = ntohs (msg->size);
   GNUNET_assert (size >= msg_size);
-  memcpy (buf, mqm->mh, msg_size);
-  GNUNET_free (mqm);
+  memcpy (buf, msg, msg_size);
   state->th = NULL;
 
-  if (NULL != mq->msg_head)
-  {
-    mq->current_msg = mq->msg_head;
-    GNUNET_CONTAINER_DLL_remove (mq->msg_head, mq->msg_tail, mq->current_msg);
-    state->th = 
-        GNUNET_SERVER_notify_transmit_ready (state->client, msg_size, 
-                                             GNUNET_TIME_UNIT_FOREVER_REL,
-                                             &transmit_queued, mq);
-  }
+  GNUNET_MQ_impl_send_continue (mq);
+
   return msg_size;
 }
 
 
-
 static void
-server_client_destroy_impl (struct GNUNET_MQ_MessageQueue *mq)
+server_client_destroy_impl (struct GNUNET_MQ_Handle *mq,
+                            void *impl_state)
 {
-  struct ServerClientSocketState *state;
-  
+  struct ServerClientSocketState *state = impl_state;
+
+  if (NULL != state->th)
+  {
+    GNUNET_SERVER_notify_transmit_ready_cancel (state->th);
+    state->th = NULL;
+  }
+
   GNUNET_assert (NULL != mq);
-  state = mq->impl_state;
   GNUNET_assert (NULL != state);
   GNUNET_SERVER_client_drop (state->client);
   GNUNET_free (state);
 }
 
+
 static void
-server_client_send_impl (struct GNUNET_MQ_MessageQueue *mq, struct GNUNET_MQ_Message *mqm)
+server_client_send_impl (struct GNUNET_MQ_Handle *mq,
+                         const struct GNUNET_MessageHeader *msg,
+                         void *impl_state)
 {
-  struct ServerClientSocketState *state;
-  int msize;
+  struct ServerClientSocketState *state = impl_state;
 
   GNUNET_assert (NULL != mq);
-  state = mq->impl_state;
   GNUNET_assert (NULL != state);
-
-  if (NULL != state->th)
-  {
-    GNUNET_CONTAINER_DLL_insert_tail (mq->msg_head, mq->msg_tail, mqm);
-    return;
-  }
-  GNUNET_assert (NULL == mq->msg_head);
-  GNUNET_assert (NULL == mq->current_msg);
-  msize = ntohs (mqm->mh->size);
-  mq->current_msg = mqm;
-  state->th = 
-      GNUNET_SERVER_notify_transmit_ready (state->client, msize, 
+  state->th =
+      GNUNET_SERVER_notify_transmit_ready (state->client, ntohs (msg->size),
                                            GNUNET_TIME_UNIT_FOREVER_REL,
                                            &transmit_queued, mq);
 }
 
 
-struct GNUNET_MQ_MessageQueue *
+struct GNUNET_MQ_Handle *
 GNUNET_MQ_queue_for_server_client (struct GNUNET_SERVER_Client *client)
 {
-  struct GNUNET_MQ_MessageQueue *mq;
+  struct GNUNET_MQ_Handle *mq;
   struct ServerClientSocketState *scss;
 
-  mq = GNUNET_new (struct GNUNET_MQ_MessageQueue);
+  mq = GNUNET_new (struct GNUNET_MQ_Handle);
   scss = GNUNET_new (struct ServerClientSocketState);
   mq->impl_state = scss;
   scss->client = client;
@@ -256,23 +570,21 @@ static void
 handle_client_message (void *cls,
                        const struct GNUNET_MessageHeader *msg)
 {
-  struct GNUNET_MQ_MessageQueue *mq = cls;
+  struct GNUNET_MQ_Handle *mq = cls;
   struct ClientConnectionState *state;
 
   state = mq->impl_state;
-  
+
   if (NULL == msg)
   {
-    if (NULL == mq->error_handler)
-      LOG (GNUNET_ERROR_TYPE_WARNING, "ignoring read error (no handler installed)\n");
-    mq->error_handler (mq->handlers_cls, GNUNET_MQ_ERROR_READ);
+    GNUNET_MQ_inject_error (mq, GNUNET_MQ_ERROR_READ);
     return;
   }
 
   GNUNET_CLIENT_receive (state->connection, handle_client_message, mq,
                          GNUNET_TIME_UNIT_FOREVER_REL);
 
-  GNUNET_MQ_dispatch (mq, msg);
+  GNUNET_MQ_inject_message (mq, msg);
 }
 
 
@@ -280,127 +592,119 @@ handle_client_message (void *cls,
  * Transmit a queued message to the session's client.
  *
  * @param cls consensus session
- * @param size number of bytes available in buf
+ * @param size number of bytes available in @a buf
  * @param buf where the callee should write the message
  * @return number of bytes written to buf
  */
 static size_t
-connection_client_transmit_queued (void *cls, size_t size,
-                 void *buf)
+connection_client_transmit_queued (void *cls,
+                                   size_t size,
+                                   void *buf)
 {
-  struct GNUNET_MQ_MessageQueue *mq = cls;
-  struct GNUNET_MQ_Message *mqm = mq->current_msg;
+  struct GNUNET_MQ_Handle *mq = cls;
+  const struct GNUNET_MessageHeader *msg;
   struct ClientConnectionState *state = mq->impl_state;
   size_t msg_size;
 
+  GNUNET_assert (NULL != mq);
+  msg = GNUNET_MQ_impl_current (mq);
+
   if (NULL == buf)
   {
-    if (NULL == mq->error_handler)
-    {
-      LOG (GNUNET_ERROR_TYPE_WARNING, "read error, but no error handler installed\n");
-      return 0;
-    }
-    mq->error_handler (mq->handlers_cls, GNUNET_MQ_ERROR_READ);
+    GNUNET_MQ_inject_error (mq, GNUNET_MQ_ERROR_READ);
     return 0;
   }
 
-  if ((NULL != mq->handlers) && (GNUNET_NO == state->receive_active))
+  if ( (GNUNET_YES == state->receive_requested) &&
+       (GNUNET_NO == state->receive_active) )
   {
     state->receive_active = GNUNET_YES;
     GNUNET_CLIENT_receive (state->connection, handle_client_message, mq,
                            GNUNET_TIME_UNIT_FOREVER_REL);
   }
 
-
-  GNUNET_assert (NULL != mqm);
-
-  if (NULL != mqm->sent_cb)
-  {
-    mqm->sent_cb (mqm->sent_cls);
-  }
-
-  mq->current_msg = NULL;
-  GNUNET_assert (NULL != buf);
-  msg_size = ntohs (mqm->mh->size);
+  msg_size = ntohs (msg->size);
   GNUNET_assert (size >= msg_size);
-  memcpy (buf, mqm->mh, msg_size);
-  GNUNET_free (mqm);
+  memcpy (buf, msg, msg_size);
   state->th = NULL;
-  if (NULL != mq->msg_head)
-  {
-    mq->current_msg = mq->msg_head;
-    GNUNET_CONTAINER_DLL_remove (mq->msg_head, mq->msg_tail, mq->current_msg);
-    state->th = 
-      GNUNET_CLIENT_notify_transmit_ready (state->connection, ntohs (mq->current_msg->mh->size), 
-                                             GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_NO,
-                                             &connection_client_transmit_queued, mq);
-  }
+
+  GNUNET_MQ_impl_send_continue (mq);
+
   return msg_size;
 }
 
 
-
 static void
-connection_client_destroy_impl (struct GNUNET_MQ_MessageQueue *mq)
+connection_client_destroy_impl (struct GNUNET_MQ_Handle *mq,
+                                void *impl_state)
 {
-  GNUNET_free (mq->impl_state);
+  GNUNET_free (impl_state);
 }
 
+
 static void
-connection_client_send_impl (struct GNUNET_MQ_MessageQueue *mq,
-                             struct GNUNET_MQ_Message *mqm)
+connection_client_send_impl (struct GNUNET_MQ_Handle *mq,
+                             const struct GNUNET_MessageHeader *msg,
+                             void *impl_state)
 {
-  struct ClientConnectionState *state = mq->impl_state;
-  int msize;
+  struct ClientConnectionState *state = impl_state;
 
   GNUNET_assert (NULL != state);
-
-  if (NULL != state->th)
-  {
-    GNUNET_CONTAINER_DLL_insert_tail (mq->msg_head, mq->msg_tail, mqm);
-    return;
-  }
-  GNUNET_assert (NULL == mq->current_msg);
-  mq->current_msg = mqm;
-  msize = ntohs (mqm->mh->size);
-  state->th = 
-      GNUNET_CLIENT_notify_transmit_ready (state->connection, msize, 
+  GNUNET_assert (NULL == state->th);
+  state->th =
+      GNUNET_CLIENT_notify_transmit_ready (state->connection, ntohs (msg->size),
                                            GNUNET_TIME_UNIT_FOREVER_REL, GNUNET_NO,
                                            &connection_client_transmit_queued, mq);
+  GNUNET_assert (NULL != state->th);
 }
 
 
+static void
+connection_client_cancel_impl (struct GNUNET_MQ_Handle *mq,
+                               void *impl_state)
+{
+  struct ClientConnectionState *state = impl_state;
+  GNUNET_assert (NULL != state->th);
+  GNUNET_CLIENT_notify_transmit_ready_cancel (state->th);
+  state->th = NULL;
+}
 
 
-
-struct GNUNET_MQ_MessageQueue *
+struct GNUNET_MQ_Handle *
 GNUNET_MQ_queue_for_connection_client (struct GNUNET_CLIENT_Connection *connection,
-                                       const struct GNUNET_MQ_Handler *handlers,
+                                       const struct GNUNET_MQ_MessageHandler *handlers,
+                                       GNUNET_MQ_ErrorHandler error_handler,
                                        void *cls)
 {
-  struct GNUNET_MQ_MessageQueue *mq;
+  struct GNUNET_MQ_Handle *mq;
   struct ClientConnectionState *state;
 
   GNUNET_assert (NULL != connection);
 
-  mq = GNUNET_new (struct GNUNET_MQ_MessageQueue);
+  mq = GNUNET_new (struct GNUNET_MQ_Handle);
   mq->handlers = handlers;
+  mq->error_handler = error_handler;
   mq->handlers_cls = cls;
   state = GNUNET_new (struct ClientConnectionState);
   state->connection = connection;
   mq->impl_state = state;
   mq->send_impl = connection_client_send_impl;
   mq->destroy_impl = connection_client_destroy_impl;
+  mq->cancel_impl = connection_client_cancel_impl;
+  if (NULL != handlers)
+    state->receive_requested = GNUNET_YES;
 
   return mq;
 }
 
 
 void
-GNUNET_MQ_replace_handlers (struct GNUNET_MQ_MessageQueue *mq,
-                            const struct GNUNET_MQ_Handler *new_handlers,
+GNUNET_MQ_replace_handlers (struct GNUNET_MQ_Handle *mq,
+                            const struct GNUNET_MQ_MessageHandler *new_handlers,
                             void *cls)
 {
+  /* FIXME: notify implementation? */
+  /* FIXME: what about NULL handlers? abort receive? */
   mq->handlers = new_handlers;
   mq->handlers_cls = cls;
 }
@@ -410,12 +714,10 @@ GNUNET_MQ_replace_handlers (struct GNUNET_MQ_MessageQueue *mq,
  * Associate the assoc_data in mq with a unique request id.
  *
  * @param mq message queue, id will be unique for the queue
- * @param mqm message to associate
  * @param assoc_data to associate
  */
 uint32_t
-GNUNET_MQ_assoc_add (struct GNUNET_MQ_MessageQueue *mq,
-                     struct GNUNET_MQ_Message *mqm,
+GNUNET_MQ_assoc_add (struct GNUNET_MQ_Handle *mq,
                      void *assoc_data)
 {
   uint32_t id;
@@ -432,9 +734,9 @@ GNUNET_MQ_assoc_add (struct GNUNET_MQ_MessageQueue *mq,
 }
 
 
-
 void *
-GNUNET_MQ_assoc_get (struct GNUNET_MQ_MessageQueue *mq, uint32_t request_id)
+GNUNET_MQ_assoc_get (struct GNUNET_MQ_Handle *mq,
+                     uint32_t request_id)
 {
   if (NULL == mq->assoc_map)
     return NULL;
@@ -443,21 +745,21 @@ GNUNET_MQ_assoc_get (struct GNUNET_MQ_MessageQueue *mq, uint32_t request_id)
 
 
 void *
-GNUNET_MQ_assoc_remove (struct GNUNET_MQ_MessageQueue *mq, uint32_t request_id)
+GNUNET_MQ_assoc_remove (struct GNUNET_MQ_Handle *mq,
+                        uint32_t request_id)
 {
   void *val;
 
   if (NULL == mq->assoc_map)
     return NULL;
   val = GNUNET_CONTAINER_multihashmap32_get (mq->assoc_map, request_id);
-  GNUNET_assert (NULL != val);
-  GNUNET_CONTAINER_multihashmap32_remove (mq->assoc_map, request_id, val);
+  GNUNET_CONTAINER_multihashmap32_remove_all (mq->assoc_map, request_id);
   return val;
 }
 
 
 void
-GNUNET_MQ_notify_sent (struct GNUNET_MQ_Message *mqm,
+GNUNET_MQ_notify_sent (struct GNUNET_MQ_Envelope *mqm,
                        GNUNET_MQ_NotifyCallback cb,
                        void *cls)
 {
@@ -467,15 +769,113 @@ GNUNET_MQ_notify_sent (struct GNUNET_MQ_Message *mqm,
 
 
 void
-GNUNET_MQ_destroy (struct GNUNET_MQ_MessageQueue *mq)
+GNUNET_MQ_destroy (struct GNUNET_MQ_Handle *mq)
 {
-  /* FIXME: destroy all pending messages in the queue */
-
   if (NULL != mq->destroy_impl)
   {
-    mq->destroy_impl (mq);
+    mq->destroy_impl (mq, mq->impl_state);
+  }
+  if (NULL != mq->continue_task)
+  {
+    GNUNET_SCHEDULER_cancel (mq->continue_task);
+    mq->continue_task = NULL;
+  }
+  while (NULL != mq->envelope_head)
+  {
+    struct GNUNET_MQ_Envelope *ev;
+    ev = mq->envelope_head;
+    ev->parent_queue = NULL;
+    GNUNET_CONTAINER_DLL_remove (mq->envelope_head, mq->envelope_tail, ev);
+    GNUNET_MQ_discard (ev);
+  }
+
+  if (NULL != mq->current_envelope)
+  {
+    /* we can only discard envelopes that
+     * are not queued! */
+    mq->current_envelope->parent_queue = NULL;
+    GNUNET_MQ_discard (mq->current_envelope);
+    mq->current_envelope = NULL;
+  }
+
+  if (NULL != mq->assoc_map)
+  {
+    GNUNET_CONTAINER_multihashmap32_destroy (mq->assoc_map);
+    mq->assoc_map = NULL;
   }
 
   GNUNET_free (mq);
 }
 
+
+const struct GNUNET_MessageHeader *
+GNUNET_MQ_extract_nested_mh_ (const struct GNUNET_MessageHeader *mh,
+                              uint16_t base_size)
+{
+  uint16_t whole_size;
+  uint16_t nested_size;
+  const struct GNUNET_MessageHeader *nested_msg;
+
+  whole_size = ntohs (mh->size);
+  GNUNET_assert (whole_size >= base_size);
+  nested_size = whole_size - base_size;
+  if (0 == nested_size)
+    return NULL;
+  if (nested_size < sizeof (struct GNUNET_MessageHeader))
+  {
+    GNUNET_break_op (0);
+    return NULL;
+  }
+  nested_msg = (const struct GNUNET_MessageHeader *) ((char *) mh + base_size);
+  if (ntohs (nested_msg->size) != nested_size)
+  {
+    GNUNET_break_op (0);
+    return NULL;
+  }
+  return nested_msg;
+}
+
+
+/**
+ * Cancel sending the message. Message must have been sent with
+ * #GNUNET_MQ_send before.  May not be called after the notify sent
+ * callback has been called
+ *
+ * @param ev queued envelope to cancel
+ */
+void
+GNUNET_MQ_send_cancel (struct GNUNET_MQ_Envelope *ev)
+{
+  struct GNUNET_MQ_Handle *mq = ev->parent_queue;
+
+  GNUNET_assert (NULL != mq);
+  GNUNET_assert (NULL != mq->cancel_impl);
+
+  if (mq->current_envelope == ev) {
+    // complex case, we already started with transmitting
+    // the message
+    mq->cancel_impl (mq, mq->impl_state);
+    // continue sending the next message, if any
+    if (NULL == mq->envelope_head)
+    {
+      mq->current_envelope = NULL;
+    }
+    else
+    {
+      mq->current_envelope = mq->envelope_head;
+      GNUNET_CONTAINER_DLL_remove (mq->envelope_head,
+                                   mq->envelope_tail,
+                                   mq->current_envelope);
+      mq->send_impl (mq, mq->current_envelope->mh, mq->impl_state);
+    }
+  } else {
+    // simple case, message is still waiting in the queue
+    GNUNET_CONTAINER_DLL_remove (mq->envelope_head, mq->envelope_tail, ev);
+  }
+
+  ev->parent_queue = NULL;
+  ev->mh = NULL;
+  GNUNET_free (ev);
+}
+
+/* end of mq.c */