path: root/src/dht/dht_api.c

/*
     This file is part of GNUnet.
     (C) 2009, 2010, 2011, 2012 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 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file dht/dht_api.c
 * @brief library to access the DHT service
 * @author Christian Grothoff
 * @author Nathan Evans
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_constants.h"
#include "gnunet_arm_service.h"
#include "gnunet_hello_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_dht_service.h"
#include "dht.h"

#define LOG(kind,...) GNUNET_log_from (kind, "dht-api",__VA_ARGS__)

/**
 * Entry in our list of messages to be (re-)transmitted.
 */
struct PendingMessage
{
  /**
   * This is a doubly-linked list.
   */
  struct PendingMessage *prev;

  /**
   * This is a doubly-linked list.
   */
  struct PendingMessage *next;

  /**
   * Message that is pending, allocated at the end
   * of this struct.
   */
  const struct GNUNET_MessageHeader *msg;

  /**
   * Handle to the DHT API context.
   */
  struct GNUNET_DHT_Handle *handle;

  /**
   * Continuation to call when the request has been
   * transmitted (for the first time) to the service; can be NULL.
   */
  GNUNET_SCHEDULER_TaskCallback cont;

  /**
   * Closure for 'cont'.
   */
  void *cont_cls;

  /**
   * Unique ID for this request
   */
  uint64_t unique_id;

  /**
   * Free the saved message once sent, set to GNUNET_YES for messages
   * that do not receive responses; GNUNET_NO if this pending message
   * is aliased from a 'struct GNUNET_DHT_RouteHandle' and will be freed
   * from there.
   */
  int free_on_send;

  /**
   * GNUNET_YES if this message is in our pending queue right now.
   */
  int in_pending_queue;

};

#if ENABLE_MALICIOUS
/**
 * Handle to act malicious message
 */
struct GNUNET_DHT_ActMaliciousHandle
{
  /**
   * Continuation to call when done.
   */
  GNUNET_DHT_ActMaliciousContinuation cont;

  /**
   * Main handle to this DHT api
   */
  struct GNUNET_DHT_Handle *dht_handle;

  /**
   * Closure for 'cont'.
   */
  void *cont_cls;
};
#endif

/**
 * Handle to a PUT request.
 */
struct GNUNET_DHT_PutHandle
{
  /**
   * Kept in a DLL.
   */
  struct GNUNET_DHT_PutHandle *next;

  /**
   * Kept in a DLL.
   */
  struct GNUNET_DHT_PutHandle *prev;

  /**
   * Continuation to call when done.
   */
  GNUNET_DHT_PutContinuation cont;

  /**
   * Pending message associated with this PUT operation,
   * NULL after the message has been transmitted to the service.
   */
  struct PendingMessage *pending;

  /**
   * Main handle to this DHT api
   */
  struct GNUNET_DHT_Handle *dht_handle;

  /**
   * Closure for 'cont'.
   */
  void *cont_cls;

  /**
   * Timeout task for this operation.
   */
  struct GNUNET_SCHEDULER_Task * timeout_task;

  /**
   * Unique ID for the PUT operation.
   */
  uint64_t unique_id;

};

/**
 * Handle to a GET request
 */
struct GNUNET_DHT_GetHandle
{

  /**
   * Iterator to call on data receipt
   */
  GNUNET_DHT_GetIterator iter;

  /**
   * Closure for the iterator callback
   */
  void *iter_cls;

  /**
   * Main handle to this DHT api
   */
  struct GNUNET_DHT_Handle *dht_handle;

  /**
   * The actual message sent for this request,
   * used for retransmitting requests on service
   * failure/reconnect.  Freed on route_stop.
   */
  struct PendingMessage *message;

  /**
   * Array of hash codes over the results that we have already
   * seen.
   */
  struct GNUNET_HashCode *seen_results;

  /**
   * Key that this get request is for
   */
  struct GNUNET_HashCode key;

  /**
   * Unique identifier for this request (for key collisions).
   */
  uint64_t unique_id;

  /**
   * Size of the 'seen_results' array.  Note that not
   * all positions might be used (as we over-allocate).
   */
  unsigned int seen_results_size;

  /**
   * Offset into the 'seen_results' array marking the
   * end of the positions that are actually used.
   */
  unsigned int seen_results_end;

  /**
   * Offset into the 'seen_results' array marking the
   * position up to where we've send the hash codes to
   * the DHT for blocking (needed as we might not be
   * able to send all hash codes at once).
   */
  unsigned int seen_results_transmission_offset;


};


/**
 * Handle to a monitoring request.
 */
struct GNUNET_DHT_MonitorHandle
{
  /**
   * DLL.
   */
  struct GNUNET_DHT_MonitorHandle *next;

  /**
   * DLL.
   */
  struct GNUNET_DHT_MonitorHandle *prev;

  /**
   * Main handle to this DHT api.
   */
  struct GNUNET_DHT_Handle *dht_handle;

  /**
   * Type of block looked for.
   */
  enum GNUNET_BLOCK_Type type;

  /**
   * Key being looked for, NULL == all.
   */
  struct GNUNET_HashCode *key;

  /**
   * Callback for each received message of type get.
   */
  GNUNET_DHT_MonitorGetCB get_cb;

  /**
   * Callback for each received message of type get response.
   */
  GNUNET_DHT_MonitorGetRespCB get_resp_cb;

  /**
   * Callback for each received message of type put.
   */
  GNUNET_DHT_MonitorPutCB put_cb;

  /**
   * Closure for cb.
   */
  void *cb_cls;

};


/**
 * Connection to the DHT service.
 */
struct GNUNET_DHT_Handle
{

  /**
   * Configuration to use.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Socket (if available).
   */
  struct GNUNET_CLIENT_Connection *client;

  /**
   * Currently pending transmission request (or NULL).
   */
  struct GNUNET_CLIENT_TransmitHandle *th;

  /**
   * Head of linked list of messages we would like to transmit.
   */
  struct PendingMessage *pending_head;

  /**
   * Tail of linked list of messages we would like to transmit.
   */
  struct PendingMessage *pending_tail;

  /**
   * Head of linked list of messages we would like to monitor.
   */
  struct GNUNET_DHT_MonitorHandle *monitor_head;

  /**
   * Tail of linked list of messages we would like to monitor.
   */
  struct GNUNET_DHT_MonitorHandle *monitor_tail;

  /**
   * Head of active PUT requests.
   */
  struct GNUNET_DHT_PutHandle *put_head;

  /**
   * Tail of active PUT requests.
   */
  struct GNUNET_DHT_PutHandle *put_tail;

  /**
   * Hash map containing the current outstanding unique GET requests
   * (values are of type `struct GNUNET_DHT_GetHandle`).
   */
  struct GNUNET_CONTAINER_MultiHashMap *active_requests;

  /**
   * Task for trying to reconnect.
   */
  struct GNUNET_SCHEDULER_Task * reconnect_task;

  /**
   * How quickly should we retry?  Used for exponential back-off on
   * connect-errors.
   */
  struct GNUNET_TIME_Relative retry_time;

  /**
   * Generator for unique ids.
   */
  uint64_t uid_gen;

  /**
   * Did we start our receive loop yet?
   */
  int in_receive;
  
#if ENABLE_MALICIOUS
  /**
   * Handle of act malicious request.
   */
  struct GNUNET_DHT_ActMaliciousHandle *mh;
#endif
};


/**
 * Handler for messages received from the DHT service
 * a demultiplexer which handles numerous message types
 *
 * @param cls the `struct GNUNET_DHT_Handle`
 * @param msg the incoming message
 */
static void
service_message_handler (void *cls,
			 const struct GNUNET_MessageHeader *msg);


/**
 * Try to (re)connect to the DHT service.
 *
 * @param handle DHT handle to reconnect
 * @return #GNUNET_YES on success, #GNUNET_NO on failure.
 */
static int
try_connect (struct GNUNET_DHT_Handle *handle)
{
  if (NULL != handle->client)
    return GNUNET_OK;
  handle->in_receive = GNUNET_NO;
  handle->client = GNUNET_CLIENT_connect ("dht", handle->cfg);
  if (NULL == handle->client)
  {
    LOG (GNUNET_ERROR_TYPE_WARNING,
         _("Failed to connect to the DHT service!\n"));
    return GNUNET_NO;
  }
  return GNUNET_YES;
}


/**
 * Queue messages to DHT to block certain results from the result set.
 *
 * @param get_handle GET to generate messages for.
 */
static void
queue_filter_messages (struct GNUNET_DHT_GetHandle *get_handle)
{
  struct PendingMessage *pm;
  struct GNUNET_DHT_ClientGetResultSeenMessage *msg;
  uint16_t msize;
  unsigned int delta;
  unsigned int max;

  while (get_handle->seen_results_transmission_offset < get_handle->seen_results_end)
  {
    delta = get_handle->seen_results_end - get_handle->seen_results_transmission_offset;
    max = (GNUNET_SERVER_MAX_MESSAGE_SIZE - sizeof (struct GNUNET_DHT_ClientGetResultSeenMessage)) / sizeof (struct GNUNET_HashCode);
    if (delta > max)
      delta = max;
    msize = sizeof (struct GNUNET_DHT_ClientGetResultSeenMessage) + delta * sizeof (struct GNUNET_HashCode);

    pm = GNUNET_malloc (sizeof (struct PendingMessage) + msize);
    msg = (struct GNUNET_DHT_ClientGetResultSeenMessage *) &pm[1];
    pm->msg = &msg->header;
    pm->handle = get_handle->dht_handle;
    pm->unique_id = get_handle->unique_id;
    pm->free_on_send = GNUNET_YES;
    pm->in_pending_queue = GNUNET_YES;
    msg->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CLIENT_GET_RESULTS_KNOWN);
    msg->header.size = htons (msize);
    msg->key = get_handle->key;
    msg->unique_id = get_handle->unique_id;
    memcpy (&msg[1],
	    &get_handle->seen_results[get_handle->seen_results_transmission_offset],
	    sizeof (struct GNUNET_HashCode) * delta);
    get_handle->seen_results_transmission_offset += delta;
    GNUNET_CONTAINER_DLL_insert_tail (get_handle->dht_handle->pending_head,
				      get_handle->dht_handle->pending_tail,
				      pm);
  }
}


/**
 * Add the request corresponding to the given route handle
 * to the pending queue (if it is not already in there).
 *
 * @param cls the `struct GNUNET_DHT_Handle *`
 * @param key key for the request (not used)
 * @param value the `struct GNUNET_DHT_GetHandle *`
 * @return #GNUNET_YES (always)
 */
static int
add_request_to_pending (void *cls,
			const struct GNUNET_HashCode *key,
			void *value)
{
  struct GNUNET_DHT_Handle *handle = cls;
  struct GNUNET_DHT_GetHandle *get_handle = value;

  if (GNUNET_NO == get_handle->message->in_pending_queue)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Retransmitting request related to %s to DHT %p\n", GNUNET_h2s (key),
         handle);
    get_handle->seen_results_transmission_offset = 0;
    GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                                 get_handle->message);
    queue_filter_messages (get_handle);
    get_handle->message->in_pending_queue = GNUNET_YES;
  }
  return GNUNET_YES;
}


/**
 * Try to send messages from list of messages to send
 *
 * @param handle DHT_Handle
 */
static void
process_pending_messages (struct GNUNET_DHT_Handle *handle);


/**
 * Try reconnecting to the dht service.
 *
 * @param cls a `struct GNUNET_DHT_Handle`
 * @param tc scheduler context
 */
static void
try_reconnect (void *cls,
	       const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_DHT_Handle *handle = cls;

  LOG (GNUNET_ERROR_TYPE_DEBUG, "Reconnecting with DHT %p\n", handle);
  handle->retry_time = GNUNET_TIME_STD_BACKOFF (handle->retry_time);
  handle->reconnect_task = NULL;
  if (GNUNET_YES != try_connect (handle))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, "dht reconnect failed(!)\n");
    return;
  }
  GNUNET_CONTAINER_multihashmap_iterate (handle->active_requests,
                                         &add_request_to_pending, handle);
  process_pending_messages (handle);
}


/**
 * Try reconnecting to the DHT service.
 *
 * @param handle handle to dht to (possibly) disconnect and reconnect
 */
static void
do_disconnect (struct GNUNET_DHT_Handle *handle)
{
  struct GNUNET_DHT_PutHandle *ph;
  struct GNUNET_DHT_PutHandle *next;

  if (NULL == handle->client)
    return;
  GNUNET_assert (NULL == handle->reconnect_task);
  if (NULL != handle->th)
    GNUNET_CLIENT_notify_transmit_ready_cancel (handle->th);
  handle->th = NULL;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Disconnecting from DHT service, will try to reconnect in %s\n",
              GNUNET_STRINGS_relative_time_to_string (handle->retry_time,
						      GNUNET_YES));
  GNUNET_CLIENT_disconnect (handle->client);
  handle->client = NULL;

  /* signal disconnect to all PUT requests that were transmitted but waiting
     for the put confirmation */
  next = handle->put_head;
  while (NULL != (ph = next))
  {
    next = ph->next;
    if (NULL == ph->pending)
    {
      if (NULL != ph->cont)
	ph->cont (ph->cont_cls, GNUNET_SYSERR);
      GNUNET_DHT_put_cancel (ph);
    }
  }
  handle->reconnect_task =
      GNUNET_SCHEDULER_add_delayed (handle->retry_time, &try_reconnect, handle);
}


/**
 * Transmit the next pending message, called by notify_transmit_ready
 *
 * @param cls the DHT handle
 * @param size number of bytes available in @a buf for transmission
 * @param buf where to copy messages for the service
 * @return number of bytes written to @a buf
 */
static size_t
transmit_pending (void *cls,
		  size_t size,
		  void *buf);


/**
 * Try to send messages from list of messages to send
 *
 * @param handle handle to DHT
 */
static void
process_pending_messages (struct GNUNET_DHT_Handle *handle)
{
  struct PendingMessage *head;

  if (NULL == handle->client)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "process_pending_messages called, but client is NULL, reconnecting\n");
    do_disconnect (handle);
    return;
  }
  if (NULL != handle->th)
    return;
  if (NULL == (head = handle->pending_head))
    return;
  handle->th =
      GNUNET_CLIENT_notify_transmit_ready (handle->client,
                                           ntohs (head->msg->size),
                                           GNUNET_TIME_UNIT_FOREVER_REL,
                                           GNUNET_YES, &transmit_pending,
                                           handle);
  if (NULL != handle->th)
    return;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "notify_transmit_ready returned NULL, reconnecting\n");
  do_disconnect (handle);
}


/**
 * Transmit the next pending message, called by notify_transmit_ready
 *
 * @param cls the DHT handle
 * @param size number of bytes available in @a buf for transmission
 * @param buf where to copy messages for the service
 * @return number of bytes written to @a buf
 */
static size_t
transmit_pending (void *cls,
		  size_t size,
		  void *buf)
{
  struct GNUNET_DHT_Handle *handle = cls;
  struct PendingMessage *head;
  size_t tsize;


  handle->th = NULL;
  if (NULL == buf)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Transmission to DHT service failed!  Reconnecting!\n");
    do_disconnect (handle);
    return 0;
  }
  if (NULL == (head = handle->pending_head))
    return 0;

  tsize = ntohs (head->msg->size);
  if (size < tsize)
  {
    process_pending_messages (handle);
    return 0;
  }
  memcpy (buf, head->msg, tsize);
  GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
                               head);
  head->in_pending_queue = GNUNET_NO;
  if (NULL != head->cont)
  {
    head->cont (head->cont_cls, NULL);
    head->cont = NULL;
    head->cont_cls = NULL;
  }
  if (GNUNET_YES == head->free_on_send)
    GNUNET_free (head);
  process_pending_messages (handle);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Forwarded request of %u bytes to DHT service\n", (unsigned int) tsize);
  if (GNUNET_NO == handle->in_receive)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Starting to process replies from DHT\n");
    handle->in_receive = GNUNET_YES;
    
    GNUNET_CLIENT_receive (handle->client, &service_message_handler, handle,
                           GNUNET_TIME_UNIT_FOREVER_REL);
  }
  return tsize;
}


/**
 * Process a given reply that might match the given
 * request.
 *
 * @param cls the `struct GNUNET_DHT_ClientResultMessage`
 * @param key query of the request
 * @param value the `struct GNUNET_DHT_RouteHandle` of a request matching the same key
 * @return #GNUNET_YES to continue to iterate over all results,
 *         #GNUNET_NO if the reply is malformed or we found a matching request
 */
static int
process_reply (void *cls,
	       const struct GNUNET_HashCode *key,
	       void *value)
{
  const struct GNUNET_DHT_ClientResultMessage *dht_msg = cls;
  struct GNUNET_DHT_GetHandle *get_handle = value;
  const struct GNUNET_PeerIdentity *put_path;
  const struct GNUNET_PeerIdentity *get_path;
  struct GNUNET_HashCode hc;
  uint32_t put_path_length;
  uint32_t get_path_length;
  size_t data_length;
  size_t msize;
  size_t meta_length;
  const void *data;

  if (dht_msg->unique_id != get_handle->unique_id)
  {
    /* UID mismatch */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Ignoring reply for %s: UID mismatch: %llu/%llu\n", GNUNET_h2s (key),
         dht_msg->unique_id, get_handle->unique_id);
    return GNUNET_YES;
  }
  msize = ntohs (dht_msg->header.size);
  put_path_length = ntohl (dht_msg->put_path_length);
  get_path_length = ntohl (dht_msg->get_path_length);
  meta_length =
      sizeof (struct GNUNET_DHT_ClientResultMessage) +
      sizeof (struct GNUNET_PeerIdentity) * (get_path_length + put_path_length);
  if ((msize < meta_length) ||
      (get_path_length >
       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)) ||
      (put_path_length >
       GNUNET_SERVER_MAX_MESSAGE_SIZE / sizeof (struct GNUNET_PeerIdentity)))
  {
    GNUNET_break (0);
    return GNUNET_NO;
  }
  data_length = msize - meta_length;
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Giving %u byte reply for %s to application\n",
       (unsigned int) data_length, GNUNET_h2s (key));
  put_path = (const struct GNUNET_PeerIdentity *) &dht_msg[1];
  get_path = &put_path[put_path_length];
  data = &get_path[get_path_length];
  /* remember that we've seen this result */
  GNUNET_CRYPTO_hash (data, data_length, &hc);
  if (get_handle->seen_results_size == get_handle->seen_results_end)
    GNUNET_array_grow (get_handle->seen_results,
		       get_handle->seen_results_size,
		       get_handle->seen_results_size * 2 + 1);
  GNUNET_assert (get_handle->seen_results_end == get_handle->seen_results_transmission_offset);
  get_handle->seen_results[get_handle->seen_results_end++] = hc;
  /* no need to block it explicitly, service already knows about it! */
  get_handle->seen_results_transmission_offset++;
  get_handle->iter (get_handle->iter_cls,
                    GNUNET_TIME_absolute_ntoh (dht_msg->expiration), key,
                    get_path, get_path_length, put_path, put_path_length,
                    ntohl (dht_msg->type), data_length, data);
  return GNUNET_NO;
}


/**
 * Process a get monitor message from the service.
 *
 * @param handle The DHT handle.
 * @param msg Monitor get message from the service.
 * @return #GNUNET_OK if everything went fine,
 *         #GNUNET_SYSERR if the message is malformed.
 */
static int
process_monitor_get_message (struct GNUNET_DHT_Handle *handle,
                             const struct GNUNET_DHT_MonitorGetMessage *msg)
{
  struct GNUNET_DHT_MonitorHandle *h;

  for (h = handle->monitor_head; NULL != h; h = h->next)
  {
    int type_ok;
    int key_ok;

    type_ok = (GNUNET_BLOCK_TYPE_ANY == h->type) || (h->type == ntohl(msg->type));
    key_ok = (NULL == h->key) || (0 == memcmp (h->key, &msg->key,
					       sizeof (struct GNUNET_HashCode)));
    if (type_ok && key_ok && (NULL != h->get_cb))
      h->get_cb (h->cb_cls,
		 ntohl (msg->options),
		 (enum GNUNET_BLOCK_Type) ntohl(msg->type),
		 ntohl (msg->hop_count),
		 ntohl (msg->desired_replication_level),
		 ntohl (msg->get_path_length),
		 (struct GNUNET_PeerIdentity *) &msg[1],
		 &msg->key);
  }
  return GNUNET_OK;
}


/**
 * Process a get response monitor message from the service.
 *
 * @param handle The DHT handle.
 * @param msg monitor get response message from the service
 * @return #GNUNET_OK if everything went fine,
 *         #GNUNET_SYSERR if the message is malformed.
 */
static int
process_monitor_get_resp_message (struct GNUNET_DHT_Handle *handle,
                                  const struct GNUNET_DHT_MonitorGetRespMessage *msg)
{
  struct GNUNET_DHT_MonitorHandle *h;
  struct GNUNET_PeerIdentity *path;
  uint32_t getl;
  uint32_t putl;
  size_t msize;

  msize = ntohs (msg->header.size);
  path = (struct GNUNET_PeerIdentity *) &msg[1];
  getl = ntohl (msg->get_path_length);
  putl = ntohl (msg->put_path_length);
  if ( (getl + putl < getl) ||
       ( ((msize - sizeof (struct GNUNET_DHT_MonitorGetRespMessage)) / sizeof (struct GNUNET_PeerIdentity)) < getl + putl) )
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  for (h = handle->monitor_head; NULL != h; h = h->next)
  {
    int type_ok;
    int key_ok;

    type_ok = (GNUNET_BLOCK_TYPE_ANY == h->type) || (h->type == ntohl(msg->type));
    key_ok = (NULL == h->key) || (0 == memcmp (h->key, &msg->key,
					       sizeof (struct GNUNET_HashCode)));
    if (type_ok && key_ok && (NULL != h->get_resp_cb))
      h->get_resp_cb (h->cb_cls,
                      (enum GNUNET_BLOCK_Type) ntohl(msg->type),
                      path, getl,
                      &path[getl], putl,
                      GNUNET_TIME_absolute_ntoh(msg->expiration_time),
                      &msg->key,
                      (void *) &path[getl + putl],
                      msize -
                      sizeof (struct GNUNET_DHT_MonitorGetRespMessage) -
                      sizeof (struct GNUNET_PeerIdentity) * (putl + getl));
  }
  return GNUNET_OK;
}


/**
 * Process a put monitor message from the service.
 *
 * @param handle The DHT handle.
 * @param msg Monitor put message from the service.
 * @return #GNUNET_OK if everything went fine,
 *         #GNUNET_SYSERR if the message is malformed.
 */
static int
process_monitor_put_message (struct GNUNET_DHT_Handle *handle,
                             const struct GNUNET_DHT_MonitorPutMessage *msg)
{
  struct GNUNET_DHT_MonitorHandle *h;
  size_t msize;
  struct GNUNET_PeerIdentity *path;
  uint32_t putl;

  msize = ntohs (msg->header.size);
  path = (struct GNUNET_PeerIdentity *) &msg[1];
  putl = ntohl (msg->put_path_length);
  if (((msize - sizeof (struct GNUNET_DHT_MonitorGetRespMessage)) / sizeof (struct GNUNET_PeerIdentity)) < putl)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  for (h = handle->monitor_head; NULL != h; h = h->next)
  {
    int type_ok;
    int key_ok;

    type_ok = (GNUNET_BLOCK_TYPE_ANY == h->type) || (h->type == ntohl(msg->type));
    key_ok = (NULL == h->key) || (0 == memcmp (h->key, &msg->key,
					       sizeof (struct GNUNET_HashCode)));
    if (type_ok && key_ok && (NULL != h->put_cb))
      h->put_cb (h->cb_cls,
                 ntohl (msg->options),
                 (enum GNUNET_BLOCK_Type) ntohl(msg->type),
                 ntohl (msg->hop_count),
                 ntohl (msg->desired_replication_level),
                 putl, path,
                 GNUNET_TIME_absolute_ntoh(msg->expiration_time),
                 &msg->key,
                 (void *) &path[putl],
                 msize -
                 sizeof (struct GNUNET_DHT_MonitorPutMessage) -
                 sizeof (struct GNUNET_PeerIdentity) * putl);
  }
  return GNUNET_OK;
}


#if ENABLE_MALICIOUS
/**
 * Process a act malicious confirmation from service.
 * @param handle The DHT handle.
 * @param msg confirmation message from the service.
 * @return #GNUNET_OK if everything went fine,
 *         #GNUNET_SYSERR if the message is malformed.
 */
static int
process_act_malicious_confirmation_message (struct GNUNET_DHT_Handle *handle,
           const struct GNUNET_DHT_ClientActMaliciousConfirmationMessage *msg)
{
   struct GNUNET_DHT_ActMaliciousHandle *mh;
   GNUNET_DHT_PutContinuation cont;
   void *cont_cls;
   
   mh = handle->mh;
   if (NULL == mh)
    return GNUNET_OK;
  cont = mh->cont;
  cont_cls = mh->cont_cls;
  if (NULL != cont)
    cont (cont_cls, GNUNET_OK);
  
  return GNUNET_OK;
}
#endif


/**
 * Process a put confirmation message from the service.
 *
 * @param handle The DHT handle.
 * @param msg confirmation message from the service.
 * @return #GNUNET_OK if everything went fine,
 *         #GNUNET_SYSERR if the message is malformed.
 */
static int
process_put_confirmation_message (struct GNUNET_DHT_Handle *handle,
				  const struct GNUNET_DHT_ClientPutConfirmationMessage *msg)
{
  struct GNUNET_DHT_PutHandle *ph;
  GNUNET_DHT_PutContinuation cont;
  void *cont_cls;

  for (ph = handle->put_head; NULL != ph; ph = ph->next)
    if (ph->unique_id == msg->unique_id)
      break;
  if (NULL == ph)
    return GNUNET_OK;
  cont = ph->cont;
  cont_cls = ph->cont_cls;
  GNUNET_DHT_put_cancel (ph);
  if (NULL != cont)
    cont (cont_cls, GNUNET_OK);
  return GNUNET_OK;
}


/**
 * Handler for messages received from the DHT service
 * a demultiplexer which handles numerous message types
 *
 * @param cls the `struct GNUNET_DHT_Handle`
 * @param msg the incoming message
 */
static void
service_message_handler (void *cls, const struct GNUNET_MessageHeader *msg)
{
  struct GNUNET_DHT_Handle *handle = cls;
  const struct GNUNET_DHT_ClientResultMessage *dht_msg;
  uint16_t msize;
  int ret;


  if (NULL == msg)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Error receiving data from DHT service, reconnecting\n");
    do_disconnect (handle);
    return;
  }
  GNUNET_CLIENT_receive (handle->client, &service_message_handler, handle,
                         GNUNET_TIME_UNIT_FOREVER_REL);
  ret = GNUNET_SYSERR;
  msize = ntohs (msg->size);
  switch (ntohs (msg->type))
  {
  case GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET:
    if (msize < sizeof (struct GNUNET_DHT_MonitorGetMessage))
    {
      GNUNET_break (0);
      break;
    }
    ret = process_monitor_get_message(handle,
				      (const struct GNUNET_DHT_MonitorGetMessage *) msg);
    break;
  case GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET_RESP:
    if (msize < sizeof (struct GNUNET_DHT_MonitorGetRespMessage))
    {
      GNUNET_break (0);
      break;
    }
    ret = process_monitor_get_resp_message(handle,
					   (const struct GNUNET_DHT_MonitorGetRespMessage *) msg);
    break;
  case GNUNET_MESSAGE_TYPE_DHT_MONITOR_PUT:
    if (msize < sizeof (struct GNUNET_DHT_MonitorPutMessage))
    {
      GNUNET_break (0);
      break;
    }
    ret = process_monitor_put_message(handle,
				      (const struct GNUNET_DHT_MonitorPutMessage *) msg);
    break;
  case GNUNET_MESSAGE_TYPE_DHT_MONITOR_PUT_RESP:
    /* Not implemented yet */
    GNUNET_break(0);
    break;
  case GNUNET_MESSAGE_TYPE_DHT_CLIENT_RESULT:
    if (ntohs (msg->size) < sizeof (struct GNUNET_DHT_ClientResultMessage))
    {
      GNUNET_break (0);
      break;
    }
    dht_msg = (const struct GNUNET_DHT_ClientResultMessage *) msg;
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Received reply for `%s' from DHT service %p\n",
         GNUNET_h2s (&dht_msg->key), handle);
    GNUNET_CONTAINER_multihashmap_get_multiple (handle->active_requests,
						&dht_msg->key,
						&process_reply,
						(void *) dht_msg);
    ret = GNUNET_OK;
    break;
  case GNUNET_MESSAGE_TYPE_DHT_CLIENT_PUT_OK:
    if (ntohs (msg->size) != sizeof (struct GNUNET_DHT_ClientPutConfirmationMessage))
    {
      GNUNET_break (0);
      break;
    }
    ret = process_put_confirmation_message (handle,
					    (const struct GNUNET_DHT_ClientPutConfirmationMessage*) msg);
    break;
#if ENABLE_MALICIOUS
    case GNUNET_MESSAGE_TYPE_DHT_CLIENT_ACT_MALICIOUS_OK:
       if(msize != sizeof (struct GNUNET_DHT_ClientActMaliciousConfirmationMessage))
       {
         GNUNET_break (0);
         break;
       }
       ret = process_act_malicious_confirmation_message (handle,
					    (const struct GNUNET_DHT_ClientActMaliciousConfirmationMessage*) msg);
      break;
#endif
  default:
    GNUNET_break(0);
    LOG (GNUNET_ERROR_TYPE_WARNING,
         "Unknown DHT message type: %hu (%hu) size: %hu\n",
         ntohs (msg->type), msg->type, msize);
    break;
  }
  if (GNUNET_OK != ret)
  {
    GNUNET_break (0);
    do_disconnect (handle);
    return;
  }
}


/**
 * Initialize the connection with the DHT service.
 *
 * @param cfg configuration to use
 * @param ht_len size of the internal hash table to use for
 *               processing multiple GET/FIND requests in parallel
 * @return handle to the DHT service, or NULL on error
 */
struct GNUNET_DHT_Handle *
GNUNET_DHT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
                    unsigned int ht_len)
{
  struct GNUNET_DHT_Handle *handle;

  handle = GNUNET_new (struct GNUNET_DHT_Handle);
  handle->cfg = cfg;
  handle->uid_gen =
      GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK, UINT64_MAX);
  handle->active_requests = GNUNET_CONTAINER_multihashmap_create (ht_len, GNUNET_YES);
  if (GNUNET_NO == try_connect (handle))
  {
    GNUNET_DHT_disconnect (handle);
    return NULL;
  }
  return handle;
}


/**
 * Shutdown connection with the DHT service.
 *
 * @param handle handle of the DHT connection to stop
 */
void
GNUNET_DHT_disconnect (struct GNUNET_DHT_Handle *handle)
{
  struct PendingMessage *pm;
  struct GNUNET_DHT_PutHandle *ph;

  GNUNET_assert (NULL != handle);
  GNUNET_assert (0 ==
                 GNUNET_CONTAINER_multihashmap_size (handle->active_requests));
  if (NULL != handle->th)
  {
    GNUNET_CLIENT_notify_transmit_ready_cancel (handle->th);
    handle->th = NULL;
  }
  while (NULL != (pm = handle->pending_head))
  {
    GNUNET_assert (GNUNET_YES == pm->in_pending_queue);
    GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
                                 pm);
    pm->in_pending_queue = GNUNET_NO;
    GNUNET_assert (GNUNET_YES == pm->free_on_send);
    if (NULL != pm->cont)
      pm->cont (pm->cont_cls, NULL);
    GNUNET_free (pm);
  }
  while (NULL != (ph = handle->put_head))
  {
    GNUNET_break (NULL == ph->pending);
    if (NULL != ph->cont)
      ph->cont (ph->cont_cls, GNUNET_SYSERR);
    GNUNET_DHT_put_cancel (ph);
  }

  if (NULL != handle->client)
  {
    GNUNET_CLIENT_disconnect (handle->client);
    handle->client = NULL;
  }
  if (NULL != handle->reconnect_task)
    GNUNET_SCHEDULER_cancel (handle->reconnect_task);
  GNUNET_CONTAINER_multihashmap_destroy (handle->active_requests);
  GNUNET_free (handle);
}


/**
 * Timeout for the transmission of a fire&forget-request.  Clean it up.
 *
 * @param cls the `struct GNUNET_DHT_PutHandle *`
 * @param tc scheduler context
 */
static void
timeout_put_request (void *cls,
		     const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_DHT_PutHandle *ph = cls;
  struct GNUNET_DHT_Handle *handle = ph->dht_handle;

  ph->timeout_task = NULL;
  if (NULL != ph->pending)
  {
    GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
				 ph->pending);
    ph->pending->in_pending_queue = GNUNET_NO;
    GNUNET_free (ph->pending);
  }
  if (NULL != ph->cont)
    ph->cont (ph->cont_cls, GNUNET_NO);
  GNUNET_CONTAINER_DLL_remove (handle->put_head,
			       handle->put_tail,
			       ph);
  GNUNET_free (ph);
}


/**
 * Function called whenever the PUT message leaves the queue.  Sets
 * the message pointer in the put handle to NULL.
 *
 * @param cls the `struct GNUNET_DHT_PutHandle`
 * @param tc unused
 */
static void
mark_put_message_gone (void *cls,
		       const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_DHT_PutHandle *ph = cls;

  ph->pending = NULL;
}


/**
 * Perform a PUT operation storing data in the DHT.  FIXME: we should
 * change the protocol to get a confirmation for the PUT from the DHT
 * and call 'cont' only after getting the confirmation; otherwise, the
 * client has no good way of telling if the 'PUT' message actually got
 * to the DHT service!
 *
 * @param handle handle to DHT service
 * @param key the key to store under
 * @param desired_replication_level estimate of how many
 *                nearest peers this request should reach
 * @param options routing options for this message
 * @param type type of the value
 * @param size number of bytes in data; must be less than 64k
 * @param data the data to store
 * @param exp desired expiration time for the value
 * @param timeout how long to wait for transmission of this request
 * @param cont continuation to call when done (transmitting request to service)
 *        You must not call #GNUNET_DHT_disconnect in this continuation
 * @param cont_cls closure for @a cont
 */
struct GNUNET_DHT_PutHandle *
GNUNET_DHT_put (struct GNUNET_DHT_Handle *handle,
	            	const struct GNUNET_HashCode * key,
                uint32_t desired_replication_level,
                enum GNUNET_DHT_RouteOption options,
                enum GNUNET_BLOCK_Type type, size_t size,
		            const void *data,
                struct GNUNET_TIME_Absolute exp,
                struct GNUNET_TIME_Relative timeout,
		            GNUNET_DHT_PutContinuation cont,
                void *cont_cls)
{
  struct GNUNET_DHT_ClientPutMessage *put_msg;
  size_t msize;
  struct PendingMessage *pending;
  struct GNUNET_DHT_PutHandle *ph;

  msize = sizeof (struct GNUNET_DHT_ClientPutMessage) + size;
  if ((msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE) ||
      (size >= GNUNET_SERVER_MAX_MESSAGE_SIZE))
  {
    GNUNET_break (0);
    return NULL;
  }
  ph = GNUNET_new (struct GNUNET_DHT_PutHandle);
  ph->dht_handle = handle;
  ph->timeout_task = GNUNET_SCHEDULER_add_delayed (timeout, &timeout_put_request, ph);
  ph->cont = cont;
  ph->cont_cls = cont_cls;
  ph->unique_id = ++handle->uid_gen;
  pending = GNUNET_malloc (sizeof (struct PendingMessage) + msize);
  ph->pending = pending;
  put_msg = (struct GNUNET_DHT_ClientPutMessage *) &pending[1];
  pending->msg = &put_msg->header;
  pending->handle = handle;
  pending->cont = &mark_put_message_gone;
  pending->cont_cls = ph;
  pending->free_on_send = GNUNET_YES;
  put_msg->header.size = htons (msize);
  put_msg->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CLIENT_PUT);
  put_msg->type = htonl (type);
  put_msg->options = htonl ((uint32_t) options);
  put_msg->desired_replication_level = htonl (desired_replication_level);
  put_msg->unique_id = ph->unique_id;
  put_msg->expiration = GNUNET_TIME_absolute_hton (exp);
  put_msg->key = *key;
  memcpy (&put_msg[1], data, size);
  GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;
  GNUNET_CONTAINER_DLL_insert_tail (handle->put_head,
				    handle->put_tail,
				    ph);
  process_pending_messages (handle);
  return ph;
}


/**
 * Cancels a DHT PUT operation.  Note that the PUT request may still
 * go out over the network (we can't stop that); However, if the PUT
 * has not yet been sent to the service, cancelling the PUT will stop
 * this from happening (but there is no way for the user of this API
 * to tell if that is the case).  The only use for this API is to
 * prevent a later call to 'cont' from #GNUNET_DHT_put (i.e. because
 * the system is shutting down).
 *
 * @param ph put operation to cancel ('cont' will no longer be called)
 */
void
GNUNET_DHT_put_cancel (struct GNUNET_DHT_PutHandle *ph)
{
  struct GNUNET_DHT_Handle *handle = ph->dht_handle;

  if (NULL != ph->pending)
  {
    GNUNET_CONTAINER_DLL_remove (handle->pending_head,
				 handle->pending_tail,
				 ph->pending);
    GNUNET_free (ph->pending);
    ph->pending = NULL;
  }
  if (ph->timeout_task != NULL)
  {
    GNUNET_SCHEDULER_cancel (ph->timeout_task);
    ph->timeout_task = NULL;
  }
  GNUNET_CONTAINER_DLL_remove (handle->put_head,
			       handle->put_tail,
			       ph);
  GNUNET_free (ph);
}


/**
 * Perform an asynchronous GET operation on the DHT identified. See
 * also #GNUNET_BLOCK_evaluate.
 *
 * @param handle handle to the DHT service
 * @param type expected type of the response object
 * @param key the key to look up
 * @param desired_replication_level estimate of how many
                  nearest peers this request should reach
 * @param options routing options for this message
 * @param xquery extended query data (can be NULL, depending on type)
 * @param xquery_size number of bytes in @a xquery
 * @param iter function to call on each result
 * @param iter_cls closure for iter
 * @return handle to stop the async get
 */
struct GNUNET_DHT_GetHandle *
GNUNET_DHT_get_start (struct GNUNET_DHT_Handle *handle,
                      enum GNUNET_BLOCK_Type type, const struct GNUNET_HashCode * key,
                      uint32_t desired_replication_level,
                      enum GNUNET_DHT_RouteOption options, const void *xquery,
                      size_t xquery_size, GNUNET_DHT_GetIterator iter,
                      void *iter_cls)
{
  struct GNUNET_DHT_ClientGetMessage *get_msg;
  struct GNUNET_DHT_GetHandle *get_handle;
  size_t msize;
  struct PendingMessage *pending;

  msize = sizeof (struct GNUNET_DHT_ClientGetMessage) + xquery_size;
  if ((msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE) ||
      (xquery_size >= GNUNET_SERVER_MAX_MESSAGE_SIZE))
  {
    GNUNET_break (0);
    return NULL;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Sending query for %s to DHT %p\n",
       GNUNET_h2s (key), handle);
  pending = GNUNET_malloc (sizeof (struct PendingMessage) + msize);
  get_msg = (struct GNUNET_DHT_ClientGetMessage *) &pending[1];
  pending->msg = &get_msg->header;
  pending->handle = handle;
  pending->free_on_send = GNUNET_NO;
  get_msg->header.size = htons (msize);
  get_msg->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CLIENT_GET);
  get_msg->options = htonl ((uint32_t) options);
  get_msg->desired_replication_level = htonl (desired_replication_level);
  get_msg->type = htonl (type);
  get_msg->key = *key;
  get_msg->unique_id = ++handle->uid_gen;
  memcpy (&get_msg[1], xquery, xquery_size);
  GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;
  get_handle = GNUNET_new (struct GNUNET_DHT_GetHandle);
  get_handle->key = *key;
  get_handle->dht_handle = handle;
  get_handle->iter = iter;
  get_handle->iter_cls = iter_cls;
  get_handle->message = pending;
  get_handle->unique_id = get_msg->unique_id;
  GNUNET_CONTAINER_multihashmap_put (handle->active_requests,
                                     &get_handle->key,
                                     get_handle,
                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
  process_pending_messages (handle);
  return get_handle;
}


/**
 * Tell the DHT not to return any of the following known results
 * to this client.
 *
 * @param get_handle get operation for which results should be filtered
 * @param num_results number of results to be blocked that are
 *        provided in this call (size of the @a results array)
 * @param results array of hash codes over the 'data' of the results
 *        to be blocked
 */
void
GNUNET_DHT_get_filter_known_results (struct GNUNET_DHT_GetHandle *get_handle,
				     unsigned int num_results,
				     const struct GNUNET_HashCode *results)
{
  unsigned int needed;

  needed = get_handle->seen_results_end + num_results;
  if (needed > get_handle->seen_results_size)
    GNUNET_array_grow (get_handle->seen_results,
		       get_handle->seen_results_size,
		       needed);
  memcpy (&get_handle->seen_results[get_handle->seen_results_end],
	  results,
	  num_results * sizeof (struct GNUNET_HashCode));
  get_handle->seen_results_end += num_results;
  queue_filter_messages (get_handle);
  process_pending_messages (get_handle->dht_handle);
}


/**
 * Stop async DHT-get.
 *
 * @param get_handle handle to the GET operation to stop
 */
void
GNUNET_DHT_get_stop (struct GNUNET_DHT_GetHandle *get_handle)
{
  struct GNUNET_DHT_Handle *handle;
  const struct GNUNET_DHT_ClientGetMessage *get_msg;
  struct GNUNET_DHT_ClientGetStopMessage *stop_msg;
  struct PendingMessage *pending;

  handle = get_handle->message->handle;
  get_msg =
      (const struct GNUNET_DHT_ClientGetMessage *) get_handle->message->msg;
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Sending STOP for %s to DHT via %p\n",
       GNUNET_h2s (&get_msg->key), handle);
  /* generate STOP */
  pending =
      GNUNET_malloc (sizeof (struct PendingMessage) +
                     sizeof (struct GNUNET_DHT_ClientGetStopMessage));
  stop_msg = (struct GNUNET_DHT_ClientGetStopMessage *) &pending[1];
  pending->msg = &stop_msg->header;
  pending->handle = handle;
  pending->free_on_send = GNUNET_YES;
  stop_msg->header.size =
      htons (sizeof (struct GNUNET_DHT_ClientGetStopMessage));
  stop_msg->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CLIENT_GET_STOP);
  stop_msg->reserved = htonl (0);
  stop_msg->unique_id = get_msg->unique_id;
  stop_msg->key = get_msg->key;
  GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;

  /* remove 'GET' from active status */
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multihashmap_remove (handle->active_requests,
                                                       &get_handle->key,
                                                       get_handle));
  if (GNUNET_YES == get_handle->message->in_pending_queue)
  {
    GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
                                 get_handle->message);
    get_handle->message->in_pending_queue = GNUNET_NO;
  }
  GNUNET_free (get_handle->message);
  GNUNET_array_grow (get_handle->seen_results,
		     get_handle->seen_results_end,
		     0);
  GNUNET_free (get_handle);
  process_pending_messages (handle);
}


/**
 * Start monitoring the local DHT service.
 *
 * @param handle Handle to the DHT service.
 * @param type Type of blocks that are of interest.
 * @param key Key of data of interest, NULL for all.
 * @param get_cb Callback to process monitored get messages.
 * @param get_resp_cb Callback to process monitored get response messages.
 * @param put_cb Callback to process monitored put messages.
 * @param cb_cls Closure for callbacks.
 * @return Handle to stop monitoring.
 */
struct GNUNET_DHT_MonitorHandle *
GNUNET_DHT_monitor_start (struct GNUNET_DHT_Handle *handle,
                          enum GNUNET_BLOCK_Type type,
                          const struct GNUNET_HashCode *key,
                          GNUNET_DHT_MonitorGetCB get_cb,
                          GNUNET_DHT_MonitorGetRespCB get_resp_cb,
                          GNUNET_DHT_MonitorPutCB put_cb,
                          void *cb_cls)
{
  struct GNUNET_DHT_MonitorHandle *h;
  struct GNUNET_DHT_MonitorStartStopMessage *m;
  struct PendingMessage *pending;

  h = GNUNET_new (struct GNUNET_DHT_MonitorHandle);
  GNUNET_CONTAINER_DLL_insert(handle->monitor_head, handle->monitor_tail, h);

  h->get_cb = get_cb;
  h->get_resp_cb = get_resp_cb;
  h->put_cb = put_cb;
  h->cb_cls = cb_cls;
  h->type = type;
  h->dht_handle = handle;
  if (NULL != key)
  {
    h->key = GNUNET_new (struct GNUNET_HashCode);
    *h->key = *key;
  }

  pending = GNUNET_malloc (sizeof (struct GNUNET_DHT_MonitorStartStopMessage) +
                           sizeof (struct PendingMessage));
  m = (struct GNUNET_DHT_MonitorStartStopMessage *) &pending[1];
  pending->msg = &m->header;
  pending->handle = handle;
  pending->free_on_send = GNUNET_YES;
  m->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_MONITOR_START);
  m->header.size = htons (sizeof (struct GNUNET_DHT_MonitorStartStopMessage));
  m->type = htonl(type);
  m->get = htons(NULL != get_cb);
  m->get_resp = htons(NULL != get_resp_cb);
  m->put = htons(NULL != put_cb);
  if (NULL != key) {
    m->filter_key = htons(1);
    memcpy (&m->key, key, sizeof(struct GNUNET_HashCode));
  }
  GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;
  process_pending_messages (handle);

  return h;
}


/**
 * Stop monitoring.
 *
 * @param handle The handle to the monitor request returned by monitor_start.
 *
 * On return get_handle will no longer be valid, caller must not use again!!!
 */
void
GNUNET_DHT_monitor_stop (struct GNUNET_DHT_MonitorHandle *handle)
{
  struct GNUNET_DHT_MonitorStartStopMessage *m;
  struct PendingMessage *pending;

  GNUNET_CONTAINER_DLL_remove (handle->dht_handle->monitor_head,
                               handle->dht_handle->monitor_tail,
                               handle);

  pending = GNUNET_malloc (sizeof (struct GNUNET_DHT_MonitorStartStopMessage) +
                           sizeof (struct PendingMessage));
  m = (struct GNUNET_DHT_MonitorStartStopMessage *) &pending[1];
  pending->msg = &m->header;
  pending->handle = handle->dht_handle;
  pending->free_on_send = GNUNET_YES;
  m->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_MONITOR_STOP);
  m->header.size = htons (sizeof (struct GNUNET_DHT_MonitorStartStopMessage));
  m->type = htonl(handle->type);
  m->get = htons (NULL != handle->get_cb);
  m->get_resp = htons(NULL != handle->get_resp_cb);
  m->put = htons (NULL != handle->put_cb);
  if (NULL != handle->key)
  {
    m->filter_key = htons (1);
    m->key = *handle->key;
  }
  GNUNET_CONTAINER_DLL_insert (handle->dht_handle->pending_head,
                               handle->dht_handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;
  process_pending_messages (handle->dht_handle);

  GNUNET_free_non_null (handle->key);
  GNUNET_free (handle);
}


#if ENABLE_MALICIOUS
/**
 * Turn the DHT service to act malicious.
 *
 * @param handle the DHT handle
 * @param action 1 to make the service malicious; 0 to make it benign
 * @param cont continuation to call when done (transmitting request to service)
 * @param cont_cls closure for @a cont        
 */
struct GNUNET_DHT_ActMaliciousHandle *
GNUNET_DHT_act_malicious (struct GNUNET_DHT_Handle *handle, 
                          unsigned int action,
                          GNUNET_DHT_PutContinuation cont,
                          void *cont_cls)
{
  struct GNUNET_DHT_ActMaliciousMessage *amm;
  struct GNUNET_DHT_ActMaliciousHandle *mh;
  struct PendingMessage *pending;
  size_t msize;
  
  msize = sizeof(struct GNUNET_DHT_ActMaliciousMessage);
  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
  {
    GNUNET_break(0);
    return NULL;
  }
  mh = GNUNET_new (struct GNUNET_DHT_ActMaliciousHandle);
  mh->dht_handle = handle;
  mh->cont = cont;
  mh->cont_cls = cont_cls;
  pending = GNUNET_malloc (sizeof (struct PendingMessage) + msize);
  amm = (struct GNUNET_DHT_ActMaliciousMessage *)&pending[1];
  pending->msg = &amm->header;
  pending->handle = handle;
  pending->free_on_send = GNUNET_YES;
  amm->header.size = htons (msize);
  amm->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_ACT_MALICIOUS);
  amm->action = action;
  handle->mh = mh;
  GNUNET_CONTAINER_DLL_insert (handle->pending_head, handle->pending_tail,
                               pending);
  pending->in_pending_queue = GNUNET_YES;
  process_pending_messages (handle);
  return mh;
}
#endif


/* end of dht_api.c */