-fixing #2277

1 files changed, 328 insertions, 152 deletions

diff --git a/src/dht/dht_api.c b/src/dht/dht_api.c
index 9e95155a9..37b65b022 100644
--- a/src/dht/dht_api.c
+++ b/src/dht/dht_api.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2009, 2010 Christian Grothoff (and other contributing authors)
+     (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
@@ -74,11 +74,6 @@ struct PendingMessage
   void *cont_cls;
 
   /**
-   * Timeout task for this message
-   */
-  GNUNET_SCHEDULER_TaskIdentifier timeout_task;
-
-  /**
    * Unique ID for this request
    */
   uint64_t unique_id;
@@ -100,6 +95,56 @@ struct PendingMessage
 
 
 /**
+ * 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.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier timeout_task;
+
+  /**
+   * Unique ID for the PUT operation.
+   */
+  uint64_t unique_id;
+
+};
+
+
+
+/**
  * Handle to a GET request
  */
 struct GNUNET_DHT_GetHandle
@@ -235,8 +280,18 @@ struct GNUNET_DHT_Handle
   struct GNUNET_DHT_MonitorHandle *monitor_tail;
 
   /**
-   * Hash map containing the current outstanding unique requests
-   * (values are of type 'struct GNUNET_DHT_RouteHandle').
+   * 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;
 
@@ -267,6 +322,8 @@ struct GNUNET_DHT_Handle
  * 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);
@@ -275,16 +332,17 @@ 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 (handle->client != NULL)
+  if (NULL != handle->client)
     return GNUNET_OK;
   handle->in_receive = GNUNET_NO;
   handle->client = GNUNET_CLIENT_connect ("dht", handle->cfg);
-  if (handle->client == NULL)
+  if (NULL == handle->client)
   {
     LOG (GNUNET_ERROR_TYPE_WARNING,
          _("Failed to connect to the DHT service!\n"));
@@ -324,6 +382,7 @@ add_request_to_pending (void *cls, const GNUNET_HashCode * key, void *value)
 
 /**
  * Try to send messages from list of messages to send
+ *
  * @param handle DHT_Handle
  */
 static void
@@ -369,9 +428,12 @@ try_reconnect (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 static void
 do_disconnect (struct GNUNET_DHT_Handle *handle)
 {
-  if (handle->client == NULL)
+  struct GNUNET_DHT_PutHandle *ph;
+  struct GNUNET_DHT_PutHandle *next;
+
+  if (NULL == handle->client)
     return;
-  GNUNET_assert (handle->reconnect_task == GNUNET_SCHEDULER_NO_TASK);
+  GNUNET_assert (GNUNET_SCHEDULER_NO_TASK == handle->reconnect_task);
   if (NULL != handle->th)
     GNUNET_CLIENT_notify_transmit_ready_cancel (handle->th);
   handle->th = NULL;
@@ -380,6 +442,20 @@ do_disconnect (struct GNUNET_DHT_Handle *handle)
               (unsigned long long) handle->retry_time.rel_value);
   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);
 }
@@ -387,6 +463,11 @@ do_disconnect (struct GNUNET_DHT_Handle *handle)
 
 /**
  * Transmit the next pending message, called by notify_transmit_ready
+ *
+ * @param cls the DHT handle
+ * @param size number of bytes available in 'buf' for transmission
+ * @param buf where to copy messages for the service
+ * @return number of bytes written to 'buf'
  */
 static size_t
 transmit_pending (void *cls, size_t size, void *buf);
@@ -394,20 +475,22 @@ 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 (handle->client == NULL)
+  if (NULL == handle->client)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "process_pending_messages called, but client is null, reconnecting\n");
+                "process_pending_messages called, but client is NULL, reconnecting\n");
     do_disconnect (handle);
     return;
   }
-  if (handle->th != NULL)
+  if (NULL != handle->th)
     return;
   if (NULL == (head = handle->pending_head))
     return;
@@ -427,6 +510,11 @@ process_pending_messages (struct GNUNET_DHT_Handle *handle)
 
 /**
  * Transmit the next pending message, called by notify_transmit_ready
+ *
+ * @param cls the DHT handle
+ * @param size number of bytes available in 'buf' for transmission
+ * @param buf where to copy messages for the service
+ * @return number of bytes written to 'buf'
  */
 static size_t
 transmit_pending (void *cls, size_t size, void *buf)
@@ -436,7 +524,7 @@ transmit_pending (void *cls, size_t size, void *buf)
   size_t tsize;
 
   handle->th = NULL;
-  if (buf == NULL)
+  if (NULL == buf)
   {    
     LOG (GNUNET_ERROR_TYPE_DEBUG,
          "Transmission to DHT service failed!  Reconnecting!\n");
@@ -456,11 +544,6 @@ transmit_pending (void *cls, size_t size, void *buf)
   GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
                                head);
   head->in_pending_queue = GNUNET_NO;
-  if (head->timeout_task != GNUNET_SCHEDULER_NO_TASK)
-  {
-    GNUNET_SCHEDULER_cancel (head->timeout_task);
-    head->timeout_task = GNUNET_SCHEDULER_NO_TASK;
-  }
   if (NULL != head->cont)
   {
     head->cont (head->cont_cls, NULL);
@@ -557,33 +640,24 @@ process_monitor_get_message (struct GNUNET_DHT_Handle *handle,
                              const struct GNUNET_DHT_MonitorGetMessage *msg)
 {
   struct GNUNET_DHT_MonitorHandle *h;
-  size_t msize;
 
-  msize = ntohs (msg->header.size);
-  if (msize < sizeof (struct GNUNET_DHT_MonitorGetMessage))
-    return GNUNET_SYSERR;
-
-  h = handle->monitor_head;
-  while (NULL != 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 || memcmp (h->key, &msg->key,
-                                       sizeof (GNUNET_HashCode)) == 0;
-    if (type_ok && key_ok && NULL != h->get_cb)
-    {
+    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 (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);
-    }
-    h = h->next;
+                 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;
 }
@@ -593,8 +667,7 @@ process_monitor_get_message (struct GNUNET_DHT_Handle *handle,
  * Process a get response monitor message from the service.
  *
  * @param handle The DHT handle.
- * @param msg Monitor get response message from the service.
- * 
+ * @param msg monitor get response message from the service
  * @return GNUNET_OK if everything went fine,
  *         GNUNET_SYSERR if the message is malformed.
  */
@@ -604,30 +677,30 @@ process_monitor_get_resp_message (struct GNUNET_DHT_Handle *handle,
                                   *msg)
 {
   struct GNUNET_DHT_MonitorHandle *h;
+  struct GNUNET_PeerIdentity *path;
+  uint32_t getl;
+  uint32_t putl;
   size_t msize;
 
   msize = ntohs (msg->header.size);
-  if (msize < sizeof (struct GNUNET_DHT_MonitorGetRespMessage))
+  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;
-
-  h = handle->monitor_head;
-  while (NULL != 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 || memcmp (h->key, &msg->key,
-                                       sizeof (GNUNET_HashCode)) == 0;
-    if (type_ok && key_ok && NULL != h->get_resp_cb)
-    {
-      struct GNUNET_PeerIdentity *path;
-      uint32_t getl;
-      uint32_t putl;
-
-      path = (struct GNUNET_PeerIdentity *) &msg[1];
-      getl = ntohl (msg->get_path_length);
-      putl = ntohl (msg->put_path_length);
+    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 (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,
@@ -638,8 +711,6 @@ process_monitor_get_resp_message (struct GNUNET_DHT_Handle *handle,
                       msize -
                       sizeof (struct GNUNET_DHT_MonitorGetRespMessage) -
                       sizeof (struct GNUNET_PeerIdentity) * (putl + getl));
-    }
-    h = h->next;
   }
   return GNUNET_OK;
 }
@@ -660,27 +731,26 @@ process_monitor_put_message (struct GNUNET_DHT_Handle *handle,
 {
   struct GNUNET_DHT_MonitorHandle *h;
   size_t msize;
+  struct GNUNET_PeerIdentity *path;
+  uint32_t putl;
 
   msize = ntohs (msg->header.size);
-  if (msize < sizeof (struct GNUNET_DHT_MonitorPutMessage))
+  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;
-
-  h = handle->monitor_head;
-  while (NULL != 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 || memcmp (h->key, &msg->key,
-                                       sizeof (GNUNET_HashCode)) == 0;
-    if (type_ok && key_ok && NULL != h->put_cb)
-    {
-      struct GNUNET_PeerIdentity *path;
-      uint32_t putl;
-
-      path = (struct GNUNET_PeerIdentity *) &msg[1];
-      putl = ntohl (msg->put_path_length);
+    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 (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),
@@ -693,55 +763,41 @@ process_monitor_put_message (struct GNUNET_DHT_Handle *handle,
                  msize -
                  sizeof (struct GNUNET_DHT_MonitorPutMessage) -
                  sizeof (struct GNUNET_PeerIdentity) * putl);
-    }
-    h = h->next;
   }
   return GNUNET_OK;
 }
 
 
 /**
- * Process a monitoring message from the service: demultiplex for proper type.
+ * Process a put confirmation message from the service.
  *
  * @param handle The DHT handle.
- * @param msg Message from the service.
- * 
+ * @param msg confirmation message from the service.
  * @return GNUNET_OK if everything went fine,
  *         GNUNET_SYSERR if the message is malformed.
  */
 static int
-process_monitor_message (struct GNUNET_DHT_Handle *handle,
-                         const struct GNUNET_MessageHeader *msg)
+process_put_confirmation_message (struct GNUNET_DHT_Handle *handle,
+                                  const struct GNUNET_DHT_ClientPutConfirmationMessage *msg)
 {
-  switch (ntohs (msg->type))
-  {
-    case GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET:
-      return process_monitor_get_message(handle,
-                                         (struct GNUNET_DHT_MonitorGetMessage *)
-                                         msg);
+  struct GNUNET_DHT_PutHandle *ph;
+  GNUNET_DHT_PutContinuation cont;
+  void *cont_cls;
 
-    case GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET_RESP:
-    {
-      return process_monitor_get_resp_message(
-        handle,
-        (struct GNUNET_DHT_MonitorGetRespMessage *) msg);
-    }
-    case GNUNET_MESSAGE_TYPE_DHT_MONITOR_PUT:
-    {
-      return process_monitor_put_message(handle,
-                                         (struct GNUNET_DHT_MonitorPutMessage *)
-                                         msg);
-    }
-    case GNUNET_MESSAGE_TYPE_DHT_MONITOR_PUT_RESP:
-      /* Not implemented yet */
-      GNUNET_break(0);
-      /* Fall through */
-    default:
-      GNUNET_break(0);
-      return GNUNET_SYSERR;
-  }
+  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
@@ -754,38 +810,84 @@ 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 (msg == NULL)
+  if (NULL == msg)
   {
     LOG (GNUNET_ERROR_TYPE_DEBUG,
          "Error receiving data from DHT service, reconnecting\n");
     do_disconnect (handle);
     return;
   }
-  if (ntohs (msg->type) != GNUNET_MESSAGE_TYPE_DHT_CLIENT_RESULT)
+  ret = GNUNET_SYSERR;
+  msize = ntohs (msg->size);
+  switch (ntohs (msg->type))
   {
-    if (process_monitor_message (handle, msg) == GNUNET_OK)
+  case GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET:
+    if (msize < sizeof (struct GNUNET_DHT_MonitorGetMessage))
     {
-      GNUNET_CLIENT_receive (handle->client, &service_message_handler, handle,
-                             GNUNET_TIME_UNIT_FOREVER_REL);
-      return;
+      GNUNET_break (0);
+      break;
     }
-    GNUNET_break (0);
-    do_disconnect (handle);
-    return;
+    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;
+    }
+    ret = GNUNET_OK;
+    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);
+    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;
+  default:
+    GNUNET_break(0);
+    break;
   }
-  if (ntohs (msg->size) < sizeof (struct GNUNET_DHT_ClientResultMessage))
+  if (GNUNET_OK != ret)
   {
     GNUNET_break (0);
     do_disconnect (handle);
     return;
   }
-  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);
   GNUNET_CLIENT_receive (handle->client, &service_message_handler, handle,
                          GNUNET_TIME_UNIT_FOREVER_REL);
 }
@@ -829,11 +931,12 @@ void
 GNUNET_DHT_disconnect (struct GNUNET_DHT_Handle *handle)
 {
   struct PendingMessage *pm;
+  struct GNUNET_DHT_PutHandle *ph;
 
-  GNUNET_assert (handle != NULL);
+  GNUNET_assert (NULL != handle);
   GNUNET_assert (0 ==
                  GNUNET_CONTAINER_multihashmap_size (handle->active_requests));
-  if (handle->th != NULL)
+  if (NULL != handle->th)
   {
     GNUNET_CLIENT_notify_transmit_ready_cancel (handle->th);
     handle->th = NULL;
@@ -845,18 +948,24 @@ GNUNET_DHT_disconnect (struct GNUNET_DHT_Handle *handle)
                                  pm);
     pm->in_pending_queue = GNUNET_NO;
     GNUNET_assert (GNUNET_YES == pm->free_on_send);
-    if (GNUNET_SCHEDULER_NO_TASK != pm->timeout_task)
-      GNUNET_SCHEDULER_cancel (pm->timeout_task);
     if (NULL != pm->cont)
       pm->cont (pm->cont_cls, NULL);
     GNUNET_free (pm);
   }
-  if (handle->client != NULL)
+  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 (handle->reconnect_task != GNUNET_SCHEDULER_NO_TASK)
+  if (GNUNET_SCHEDULER_NO_TASK != handle->reconnect_task)
     GNUNET_SCHEDULER_cancel (handle->reconnect_task);
   GNUNET_CONTAINER_multihashmap_destroy (handle->active_requests);
   GNUNET_free (handle);
@@ -872,17 +981,40 @@ GNUNET_DHT_disconnect (struct GNUNET_DHT_Handle *handle)
 static void
 timeout_put_request (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  struct PendingMessage *pending = cls;
-  struct GNUNET_DHT_Handle *handle;
+  struct GNUNET_DHT_PutHandle *ph = cls;
+  struct GNUNET_DHT_Handle *handle = ph->dht_handle;
 
-  handle = pending->handle;
-  GNUNET_assert (GNUNET_YES == pending->in_pending_queue);
-  GNUNET_CONTAINER_DLL_remove (handle->pending_head, handle->pending_tail,
-                               pending);
-  pending->in_pending_queue = GNUNET_NO;
-  if (pending->cont != NULL)
-    pending->cont (pending->cont_cls, tc);
-  GNUNET_free (pending);
+  ph->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  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;
 }
 
 
@@ -907,49 +1039,94 @@ timeout_put_request (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
  *        You must not call GNUNET_DHT_DISCONNECT in this continuation
  * @param cont_cls closure for cont
  */
-void
+struct GNUNET_DHT_PutHandle *
 GNUNET_DHT_put (struct GNUNET_DHT_Handle *handle, const GNUNET_HashCode * key,
                 uint32_t desired_replication_level,
                 enum GNUNET_DHT_RouteOption options,
                 enum GNUNET_BLOCK_Type type, size_t size, const char *data,
                 struct GNUNET_TIME_Absolute exp,
-                struct GNUNET_TIME_Relative timeout, GNUNET_SCHEDULER_Task cont,
+                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);
-    if (NULL != cont)
-      cont (cont_cls, NULL);
-    return;
+    return NULL;
   }
+  ph = GNUNET_malloc (sizeof (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 = cont;
-  pending->cont_cls = cont_cls;
+  pending->cont = &mark_put_message_gone;
+  pending->cont_cls = ph;
   pending->free_on_send = GNUNET_YES;
-  pending->timeout_task =
-      GNUNET_SCHEDULER_add_delayed (timeout, &timeout_put_request, pending);
   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 != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (ph->timeout_task);
+    ph->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  GNUNET_CONTAINER_DLL_remove (handle->put_head,
+                               handle->put_tail,
+                               ph);
+  GNUNET_free (ph);
 }
 
 
@@ -1004,8 +1181,7 @@ GNUNET_DHT_get_start (struct GNUNET_DHT_Handle *handle,
   get_msg->desired_replication_level = htonl (desired_replication_level);
   get_msg->type = htonl (type);
   get_msg->key = *key;
-  handle->uid_gen++;
-  get_msg->unique_id = handle->uid_gen;
+  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);