Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1164 insertions, 0 deletions

diff --git a/src/dht/gnunet-service-dht_clients.c b/src/dht/gnunet-service-dht_clients.c
new file mode 100644
index 0000000..96fcd34
--- /dev/null
+++ b/src/dht/gnunet-service-dht_clients.c
@@ -0,0 +1,1164 @@
+/*
+     This file is part of GNUnet.
+     (C) 2009, 2010, 2011 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/gnunet-service-dht_clients.c
+ * @brief GNUnet DHT service's client management code
+ * @author Christian Grothoff
+ * @author Nathan Evans
+ */
+
+#include "platform.h"
+#include "gnunet_constants.h"
+#include "gnunet_protocols.h"
+#include "gnunet_statistics_service.h"
+#include "gnunet-service-dht.h"
+#include "gnunet-service-dht_clients.h"
+#include "gnunet-service-dht_datacache.h"
+#include "gnunet-service-dht_neighbours.h"
+#include "dht.h"
+
+
+/**
+ * Linked list of messages to send to clients.
+ */
+struct PendingMessage
+{
+  /**
+   * Pointer to next item in the list
+   */
+  struct PendingMessage *next;
+
+  /**
+   * Pointer to previous item in the list
+   */
+  struct PendingMessage *prev;
+
+  /**
+   * Actual message to be sent, allocated at the end of the struct:
+   * // msg = (cast) &pm[1];
+   * // memcpy (&pm[1], data, len);
+   */
+  const struct GNUNET_MessageHeader *msg;
+
+};
+
+
+/**
+ * Struct containing information about a client,
+ * handle to connect to it, and any pending messages
+ * that need to be sent to it.
+ */
+struct ClientList
+{
+  /**
+   * Linked list of active clients
+   */
+  struct ClientList *next;
+
+  /**
+   * Linked list of active clients
+   */
+  struct ClientList *prev;
+
+  /**
+   * The handle to this client
+   */
+  struct GNUNET_SERVER_Client *client_handle;
+
+  /**
+   * Handle to the current transmission request, NULL
+   * if none pending.
+   */
+  struct GNUNET_CONNECTION_TransmitHandle *transmit_handle;
+
+  /**
+   * Linked list of pending messages for this client
+   */
+  struct PendingMessage *pending_head;
+
+  /**
+   * Tail of linked list of pending messages for this client
+   */
+  struct PendingMessage *pending_tail;
+
+};
+
+
+/**
+ * Entry in the DHT routing table for a client's GET request.
+ */
+struct ClientQueryRecord
+{
+
+  /**
+   * The key this request was about
+   */
+  GNUNET_HashCode key;
+
+  /**
+   * Client responsible for the request.
+   */
+  struct ClientList *client;
+
+  /**
+   * Extended query (see gnunet_block_lib.h), allocated at the end of this struct.
+   */
+  const void *xquery;
+
+  /**
+   * Replies we have already seen for this request.
+   */
+  GNUNET_HashCode *seen_replies;
+
+  /**
+   * Pointer to this nodes heap location in the retry-heap (for fast removal)
+   */
+  struct GNUNET_CONTAINER_HeapNode *hnode;
+
+  /**
+   * What's the delay between re-try operations that we currently use for this
+   * request?
+   */
+  struct GNUNET_TIME_Relative retry_frequency;
+
+  /**
+   * What's the next time we should re-try this request?
+   */
+  struct GNUNET_TIME_Absolute retry_time;
+
+  /**
+   * The unique identifier of this request
+   */
+  uint64_t unique_id;
+
+  /**
+   * Number of bytes in xquery.
+   */
+  size_t xquery_size;
+
+  /**
+   * Number of entries in 'seen_replies'.
+   */
+  unsigned int seen_replies_count;
+
+  /**
+   * Desired replication level
+   */
+  uint32_t replication;
+
+  /**
+   * Any message options for this request
+   */
+  uint32_t msg_options;
+
+  /**
+   * The type for the data for the GET request.
+   */
+  enum GNUNET_BLOCK_Type type;
+
+};
+
+
+/**
+ * Struct containing paremeters of monitoring requests.
+ */
+struct ClientMonitorRecord
+{
+
+  /**
+   * Next element in DLL.
+   */
+  struct ClientMonitorRecord    *next;
+
+  /**
+   * Previous element in DLL.
+   */
+  struct ClientMonitorRecord    *prev;
+  
+  /**
+   * Type of blocks that are of interest
+   */
+  enum GNUNET_BLOCK_Type        type;
+
+  /**
+   * Key of data of interest, NULL for all.
+   */
+  GNUNET_HashCode         *key;
+
+  /**
+   * Client to notify of these requests.
+   */
+  struct ClientList             *client;
+};
+
+
+/**
+ * List of active clients.
+ */
+static struct ClientList *client_head;
+
+/**
+ * List of active clients.
+ */
+static struct ClientList *client_tail;
+
+/**
+ * List of active monitoring requests.
+ */
+static struct ClientMonitorRecord *monitor_head;
+
+/**
+ * List of active monitoring requests.
+ */
+static struct ClientMonitorRecord *monitor_tail;
+
+/**
+ * Hashmap for fast key based lookup, maps keys to 'struct ClientQueryRecord' entries.
+ */
+static struct GNUNET_CONTAINER_MultiHashMap *forward_map;
+
+/**
+ * Heap with all of our client's request, sorted by retry time (earliest on top).
+ */
+static struct GNUNET_CONTAINER_Heap *retry_heap;
+
+/**
+ * Task that re-transmits requests (using retry_heap).
+ */
+static GNUNET_SCHEDULER_TaskIdentifier retry_task;
+
+
+/**
+ * Find a client if it exists, add it otherwise.
+ *
+ * @param client the server handle to the client
+ *
+ * @return the client if found, a new client otherwise
+ */
+static struct ClientList *
+find_active_client (struct GNUNET_SERVER_Client *client)
+{
+  struct ClientList *pos = client_head;
+  struct ClientList *ret;
+
+  while (pos != NULL)
+  {
+    if (pos->client_handle == client)
+      return pos;
+    pos = pos->next;
+  }
+  ret = GNUNET_malloc (sizeof (struct ClientList));
+  ret->client_handle = client;
+  GNUNET_CONTAINER_DLL_insert (client_head, client_tail, ret);
+  return ret;
+}
+
+
+/**
+ * Iterator over hash map entries that frees all entries
+ * associated with the given client.
+ *
+ * @param cls client to search for in source routes
+ * @param key current key code (ignored)
+ * @param value value in the hash map, a ClientQueryRecord
+ * @return GNUNET_YES (we should continue to iterate)
+ */
+static int
+remove_client_records (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct ClientList *client = cls;
+  struct ClientQueryRecord *record = value;
+
+  if (record->client != client)
+    return GNUNET_YES;
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Removing client %p's record for key %s\n", client,
+              GNUNET_h2s (key));
+#endif
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CONTAINER_multihashmap_remove (forward_map, key,
+                                                       record));
+  if (NULL != record->hnode)
+    GNUNET_CONTAINER_heap_remove_node (record->hnode);
+  GNUNET_array_grow (record->seen_replies, record->seen_replies_count, 0);
+  GNUNET_free (record);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Functions with this signature are called whenever a client
+ * is disconnected on the network level.
+ *
+ * @param cls closure (NULL for dht)
+ * @param client identification of the client; NULL
+ *        for the last call when the server is destroyed
+ */
+static void
+handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
+{
+  struct ClientList *pos;
+  struct PendingMessage *reply;
+  struct ClientMonitorRecord *monitor;
+
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Local client %p disconnects\n", client);
+#endif
+  pos = find_active_client (client);
+  GNUNET_CONTAINER_DLL_remove (client_head, client_tail, pos);
+  if (pos->transmit_handle != NULL)
+    GNUNET_CONNECTION_notify_transmit_ready_cancel (pos->transmit_handle);
+  while (NULL != (reply = pos->pending_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (pos->pending_head, pos->pending_tail, reply);
+    GNUNET_free (reply);
+  }
+  monitor = monitor_head;
+  while (NULL != monitor)
+  {
+    if (monitor->client == pos)
+    {
+      struct ClientMonitorRecord *next;
+      
+      GNUNET_free_non_null (monitor->key);
+      next = monitor->next;
+      GNUNET_CONTAINER_DLL_remove (monitor_head, monitor_tail, monitor);
+      GNUNET_free (monitor);
+      monitor = next;
+    }
+    else
+      monitor = monitor->next;
+  }
+  GNUNET_CONTAINER_multihashmap_iterate (forward_map, &remove_client_records,
+                                         pos);
+  GNUNET_free (pos);
+}
+
+
+/**
+ * Route the given request via the DHT.  This includes updating
+ * the bloom filter and retransmission times, building the P2P
+ * message and initiating the routing operation.
+ */
+static void
+transmit_request (struct ClientQueryRecord *cqr)
+{
+  int32_t reply_bf_mutator;
+  struct GNUNET_CONTAINER_BloomFilter *reply_bf;
+  struct GNUNET_CONTAINER_BloomFilter *peer_bf;
+
+  GNUNET_STATISTICS_update (GDS_stats,
+                            gettext_noop
+                            ("# GET requests from clients injected"), 1,
+                            GNUNET_NO);
+  reply_bf_mutator =
+      (int32_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
+                                          UINT32_MAX);
+  reply_bf =
+      GNUNET_BLOCK_construct_bloomfilter (reply_bf_mutator, cqr->seen_replies,
+                                          cqr->seen_replies_count);
+  peer_bf =
+      GNUNET_CONTAINER_bloomfilter_init (NULL, DHT_BLOOM_SIZE,
+                                         GNUNET_CONSTANTS_BLOOMFILTER_K);
+  GDS_NEIGHBOURS_handle_get (cqr->type, cqr->msg_options, cqr->replication,
+                             0 /* hop count */ ,
+                             &cqr->key, cqr->xquery, cqr->xquery_size, reply_bf,
+                             reply_bf_mutator, peer_bf);
+  GNUNET_CONTAINER_bloomfilter_free (reply_bf);
+  GNUNET_CONTAINER_bloomfilter_free (peer_bf);
+
+  /* exponential back-off for retries, max 1h */
+  cqr->retry_frequency =
+      GNUNET_TIME_relative_min (GNUNET_TIME_UNIT_HOURS,
+                                GNUNET_TIME_relative_multiply
+                                (cqr->retry_frequency, 2));
+  cqr->retry_time = GNUNET_TIME_relative_to_absolute (cqr->retry_frequency);
+}
+
+
+/**
+ * Task that looks at the 'retry_heap' and transmits all of the requests
+ * on the heap that are ready for transmission.  Then re-schedules
+ * itself (unless the heap is empty).
+ *
+ * @param cls unused
+ * @param tc scheduler context
+ */
+static void
+transmit_next_request_task (void *cls,
+                            const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct ClientQueryRecord *cqr;
+  struct GNUNET_TIME_Relative delay;
+
+  retry_task = GNUNET_SCHEDULER_NO_TASK;
+  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;
+  while (NULL != (cqr = GNUNET_CONTAINER_heap_remove_root (retry_heap)))
+  {
+    cqr->hnode = NULL;
+    delay = GNUNET_TIME_absolute_get_remaining (cqr->retry_time);
+    if (delay.rel_value > 0)
+    {
+      cqr->hnode =
+          GNUNET_CONTAINER_heap_insert (retry_heap, cqr,
+                                        cqr->retry_time.abs_value);
+      retry_task =
+          GNUNET_SCHEDULER_add_delayed (delay, &transmit_next_request_task,
+                                        NULL);
+      return;
+    }
+    transmit_request (cqr);
+    cqr->hnode =
+        GNUNET_CONTAINER_heap_insert (retry_heap, cqr,
+                                      cqr->retry_time.abs_value);
+  }
+}
+
+
+/**
+ * Handler for PUT messages.
+ *
+ * @param cls closure for the service
+ * @param client the client we received this message from
+ * @param message the actual message received
+ */
+static void
+handle_dht_local_put (void *cls, struct GNUNET_SERVER_Client *client,
+                      const struct GNUNET_MessageHeader *message)
+{
+  const struct GNUNET_DHT_ClientPutMessage *dht_msg;
+  struct GNUNET_CONTAINER_BloomFilter *peer_bf;
+  uint16_t size;
+
+  size = ntohs (message->size);
+  if (size < sizeof (struct GNUNET_DHT_ClientPutMessage))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_STATISTICS_update (GDS_stats,
+                            gettext_noop
+                            ("# PUT requests received from clients"), 1,
+                            GNUNET_NO);
+  dht_msg = (const struct GNUNET_DHT_ClientPutMessage *) message;
+  /* give to local clients */
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Handling local PUT of %u-bytes for query %s\n",
+              size - sizeof (struct GNUNET_DHT_ClientPutMessage),
+              GNUNET_h2s (&dht_msg->key));
+#endif
+  GDS_CLIENTS_handle_reply (GNUNET_TIME_absolute_ntoh (dht_msg->expiration),
+                            &dht_msg->key, 0, NULL, 0, NULL,
+                            ntohl (dht_msg->type),
+                            size - sizeof (struct GNUNET_DHT_ClientPutMessage),
+                            &dht_msg[1]);
+  /* store locally */
+  GDS_DATACACHE_handle_put (GNUNET_TIME_absolute_ntoh (dht_msg->expiration),
+                            &dht_msg->key, 0, NULL, ntohl (dht_msg->type),
+                            size - sizeof (struct GNUNET_DHT_ClientPutMessage),
+                            &dht_msg[1]);
+  /* route to other peers */
+  peer_bf =
+      GNUNET_CONTAINER_bloomfilter_init (NULL, DHT_BLOOM_SIZE,
+                                         GNUNET_CONSTANTS_BLOOMFILTER_K);
+  GDS_NEIGHBOURS_handle_put (ntohl (dht_msg->type), ntohl (dht_msg->options),
+                             ntohl (dht_msg->desired_replication_level),
+                             GNUNET_TIME_absolute_ntoh (dht_msg->expiration),
+                             0 /* hop count */ ,
+                             peer_bf, &dht_msg->key, 0, NULL, &dht_msg[1],
+                             size -
+                             sizeof (struct GNUNET_DHT_ClientPutMessage));
+  GNUNET_CONTAINER_bloomfilter_free (peer_bf);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Handler for any generic DHT messages, calls the appropriate handler
+ * depending on message type, sends confirmation if responses aren't otherwise
+ * expected.
+ *
+ * @param cls closure for the service
+ * @param client the client we received this message from
+ * @param message the actual message received
+ */
+static void
+handle_dht_local_get (void *cls, struct GNUNET_SERVER_Client *client,
+                      const struct GNUNET_MessageHeader *message)
+{
+  const struct GNUNET_DHT_ClientGetMessage *get;
+  struct ClientQueryRecord *cqr;
+  size_t xquery_size;
+  const char *xquery;
+  uint16_t size;
+
+  size = ntohs (message->size);
+  if (size < sizeof (struct GNUNET_DHT_ClientGetMessage))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  xquery_size = size - sizeof (struct GNUNET_DHT_ClientGetMessage);
+  get = (const struct GNUNET_DHT_ClientGetMessage *) message;
+  xquery = (const char *) &get[1];
+  GNUNET_STATISTICS_update (GDS_stats,
+                            gettext_noop
+                            ("# GET requests received from clients"), 1,
+                            GNUNET_NO);
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received request for %s from local client %p\n",
+              GNUNET_h2s (&get->key), client);
+#endif
+  cqr = GNUNET_malloc (sizeof (struct ClientQueryRecord) + xquery_size);
+  cqr->key = get->key;
+  cqr->client = find_active_client (client);
+  cqr->xquery = (void *) &cqr[1];
+  memcpy (&cqr[1], xquery, xquery_size);
+  cqr->hnode = GNUNET_CONTAINER_heap_insert (retry_heap, cqr, 0);
+  cqr->retry_frequency = GNUNET_TIME_UNIT_MILLISECONDS;
+  cqr->retry_time = GNUNET_TIME_absolute_get ();
+  cqr->unique_id = get->unique_id;
+  cqr->xquery_size = xquery_size;
+  cqr->replication = ntohl (get->desired_replication_level);
+  cqr->msg_options = ntohl (get->options);
+  cqr->type = ntohl (get->type);
+  GNUNET_CONTAINER_multihashmap_put (forward_map, &get->key, cqr,
+                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+  /* start remote requests */
+  if (GNUNET_SCHEDULER_NO_TASK != retry_task)
+    GNUNET_SCHEDULER_cancel (retry_task);
+  retry_task = GNUNET_SCHEDULER_add_now (&transmit_next_request_task, NULL);
+  /* perform local lookup */
+  GDS_DATACACHE_handle_get (&get->key, cqr->type, cqr->xquery, xquery_size,
+                            NULL, 0);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Closure for 'remove_by_unique_id'.
+ */
+struct RemoveByUniqueIdContext
+{
+  /**
+   * Client that issued the removal request.
+   */
+  struct ClientList *client;
+
+  /**
+   * Unique ID of the request.
+   */
+  uint64_t unique_id;
+};
+
+
+/**
+ * Iterator over hash map entries that frees all entries
+ * that match the given client and unique ID.
+ *
+ * @param cls unique ID and client to search for in source routes
+ * @param key current key code
+ * @param value value in the hash map, a ClientQueryRecord
+ * @return GNUNET_YES (we should continue to iterate)
+ */
+static int
+remove_by_unique_id (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  const struct RemoveByUniqueIdContext *ctx = cls;
+  struct ClientQueryRecord *record = value;
+
+  if (record->unique_id != ctx->unique_id)
+    return GNUNET_YES;
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Removing client %p's record for key %s (by unique id)\n",
+              ctx->client->client_handle, GNUNET_h2s (key));
+#endif
+  return remove_client_records (ctx->client, key, record);
+}
+
+
+/**
+ * Handler for any generic DHT stop messages, calls the appropriate handler
+ * depending on message type (if processed locally)
+ *
+ * @param cls closure for the service
+ * @param client the client we received this message from
+ * @param message the actual message received
+ *
+ */
+static void
+handle_dht_local_get_stop (void *cls, struct GNUNET_SERVER_Client *client,
+                           const struct GNUNET_MessageHeader *message)
+{
+  const struct GNUNET_DHT_ClientGetStopMessage *dht_stop_msg =
+      (const struct GNUNET_DHT_ClientGetStopMessage *) message;
+  struct RemoveByUniqueIdContext ctx;
+
+  GNUNET_STATISTICS_update (GDS_stats,
+                            gettext_noop
+                            ("# GET STOP requests received from clients"), 1,
+                            GNUNET_NO);
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Client %p stopped request for key %s\n",
+              client, GNUNET_h2s (&dht_stop_msg->key));
+#endif
+  ctx.client = find_active_client (client);
+  ctx.unique_id = dht_stop_msg->unique_id;
+  GNUNET_CONTAINER_multihashmap_get_multiple (forward_map, &dht_stop_msg->key,
+                                              &remove_by_unique_id, &ctx);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Handler for monitor messages
+ *
+ * @param cls closure for the service
+ * @param client the client we received this message from
+ * @param message the actual message received
+ *
+ */
+static void
+handle_dht_local_monitor (void *cls, struct GNUNET_SERVER_Client *client,
+                          const struct GNUNET_MessageHeader *message)
+{
+  struct ClientMonitorRecord *r;
+  const struct GNUNET_DHT_MonitorMessage *msg;
+  unsigned int i;
+  char *c;
+
+  msg = (struct GNUNET_DHT_MonitorMessage *) message;
+  r = GNUNET_malloc (sizeof(struct ClientMonitorRecord));
+
+  r->client = find_active_client(client);
+  r->type = ntohl(msg->type);
+  c = (char *) &msg->key;
+  for (i = 0; i < sizeof (GNUNET_HashCode) && c[i] == 0; i++);
+  if (sizeof (GNUNET_HashCode) == i)
+    r->key = NULL;
+  else
+  {
+    r->key = GNUNET_malloc (sizeof (GNUNET_HashCode));
+    memcpy (r->key, &msg->key, sizeof (GNUNET_HashCode));
+  }
+  GNUNET_CONTAINER_DLL_insert (monitor_head, monitor_tail, r);
+  // FIXME add remove somewhere
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Task run to check for messages that need to be sent to a client.
+ *
+ * @param client a ClientList, containing the client and any messages to be sent to it
+ */
+static void
+process_pending_messages (struct ClientList *client);
+
+
+/**
+ * Callback called as a result of issuing a GNUNET_SERVER_notify_transmit_ready
+ * request.  A ClientList is passed as closure, take the head of the list
+ * and copy it into buf, which has the result of sending the message to the
+ * client.
+ *
+ * @param cls closure to this call
+ * @param size maximum number of bytes available to send
+ * @param buf where to copy the actual message to
+ *
+ * @return the number of bytes actually copied, 0 indicates failure
+ */
+static size_t
+send_reply_to_client (void *cls, size_t size, void *buf)
+{
+  struct ClientList *client = cls;
+  char *cbuf = buf;
+  struct PendingMessage *reply;
+  size_t off;
+  size_t msize;
+
+  client->transmit_handle = NULL;
+  if (buf == NULL)
+  {
+    /* client disconnected */
+#if DEBUG_DHT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client %p disconnected, pending messages will be discarded\n",
+                client->client_handle);
+#endif
+    return 0;
+  }
+  off = 0;
+  while ((NULL != (reply = client->pending_head)) &&
+         (size >= off + (msize = ntohs (reply->msg->size))))
+  {
+    GNUNET_CONTAINER_DLL_remove (client->pending_head, client->pending_tail,
+                                 reply);
+    memcpy (&cbuf[off], reply->msg, msize);
+    GNUNET_free (reply);
+#if DEBUG_DHT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transmitting %u bytes to client %p\n",
+                msize, client->client_handle);
+#endif
+    off += msize;
+  }
+  process_pending_messages (client);
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transmitted %u/%u bytes to client %p\n",
+              (unsigned int) off, (unsigned int) size, client->client_handle);
+#endif
+  return off;
+}
+
+
+/**
+ * Task run to check for messages that need to be sent to a client.
+ *
+ * @param client a ClientList, containing the client and any messages to be sent to it
+ */
+static void
+process_pending_messages (struct ClientList *client)
+{
+  if ((client->pending_head == NULL) || (client->transmit_handle != NULL))
+  {
+#if DEBUG_DHT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Not asking for transmission to %p now: %s\n",
+                client->client_handle,
+                client->pending_head ==
+                NULL ? "no more messages" : "request already pending");
+#endif
+    return;
+  }
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Asking for transmission of %u bytes to client %p\n",
+              ntohs (client->pending_head->msg->size), client->client_handle);
+#endif
+  client->transmit_handle =
+      GNUNET_SERVER_notify_transmit_ready (client->client_handle,
+                                           ntohs (client->pending_head->
+                                                  msg->size),
+                                           GNUNET_TIME_UNIT_FOREVER_REL,
+                                           &send_reply_to_client, client);
+}
+
+
+/**
+ * Add a PendingMessage to the clients list of messages to be sent
+ *
+ * @param client the active client to send the message to
+ * @param pending_message the actual message to send
+ */
+static void
+add_pending_message (struct ClientList *client,
+                     struct PendingMessage *pending_message)
+{
+  GNUNET_CONTAINER_DLL_insert_tail (client->pending_head, client->pending_tail,
+                                    pending_message);
+  process_pending_messages (client);
+}
+
+
+/**
+ * Closure for 'forward_reply'
+ */
+struct ForwardReplyContext
+{
+
+  /**
+   * Actual message to send to matching clients.
+   */
+  struct PendingMessage *pm;
+
+  /**
+   * Embedded payload.
+   */
+  const void *data;
+
+  /**
+   * Type of the data.
+   */
+  enum GNUNET_BLOCK_Type type;
+
+  /**
+   * Number of bytes in data.
+   */
+  size_t data_size;
+
+  /**
+   * Do we need to copy 'pm' because it was already used?
+   */
+  int do_copy;
+
+};
+
+
+/**
+ * Iterator over hash map entries that send a given reply to
+ * each of the matching clients.  With some tricky recycling
+ * of the buffer.
+ *
+ * @param cls the 'struct ForwardReplyContext'
+ * @param key current key
+ * @param value value in the hash map, a ClientQueryRecord
+ * @return GNUNET_YES (we should continue to iterate),
+ *         if the result is mal-formed, GNUNET_NO
+ */
+static int
+forward_reply (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct ForwardReplyContext *frc = cls;
+  struct ClientQueryRecord *record = value;
+  struct PendingMessage *pm;
+  struct GNUNET_DHT_ClientResultMessage *reply;
+  enum GNUNET_BLOCK_EvaluationResult eval;
+  int do_free;
+  GNUNET_HashCode ch;
+  unsigned int i;
+
+  if ((record->type != GNUNET_BLOCK_TYPE_ANY) && (record->type != frc->type))
+  {
+#if DEBUG_DHT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Record type missmatch, not passing request for key %s to local client\n",
+                GNUNET_h2s (key));
+#endif
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop
+                              ("# Key match, type mismatches in REPLY to CLIENT"),
+                              1, GNUNET_NO);
+    return GNUNET_YES;          /* type mismatch */
+  }
+  GNUNET_CRYPTO_hash (frc->data, frc->data_size, &ch);
+  for (i = 0; i < record->seen_replies_count; i++)
+    if (0 == memcmp (&record->seen_replies[i], &ch, sizeof (GNUNET_HashCode)))
+    {
+#if DEBUG_DHT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Duplicate reply, not passing request for key %s to local client\n",
+                  GNUNET_h2s (key));
+#endif
+      GNUNET_STATISTICS_update (GDS_stats,
+                                gettext_noop
+                                ("# Duplicate REPLIES to CLIENT request dropped"),
+                                1, GNUNET_NO);
+      return GNUNET_YES;        /* duplicate */
+    }
+  eval =
+      GNUNET_BLOCK_evaluate (GDS_block_context, record->type, key, NULL, 0,
+                             record->xquery, record->xquery_size, frc->data,
+                             frc->data_size);
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Evaluation result is %d for key %s for local client's query\n",
+              (int) eval, GNUNET_h2s (key));
+#endif
+  switch (eval)
+  {
+  case GNUNET_BLOCK_EVALUATION_OK_LAST:
+    do_free = GNUNET_YES;
+    break;
+  case GNUNET_BLOCK_EVALUATION_OK_MORE:
+    GNUNET_array_append (record->seen_replies, record->seen_replies_count, ch);
+    do_free = GNUNET_NO;
+    break;
+  case GNUNET_BLOCK_EVALUATION_OK_DUPLICATE:
+    /* should be impossible to encounter here */
+    GNUNET_break (0);
+    return GNUNET_YES;
+  case GNUNET_BLOCK_EVALUATION_RESULT_INVALID:
+    GNUNET_break_op (0);
+    return GNUNET_NO;
+  case GNUNET_BLOCK_EVALUATION_REQUEST_VALID:
+    GNUNET_break (0);
+    return GNUNET_NO;
+  case GNUNET_BLOCK_EVALUATION_REQUEST_INVALID:
+    GNUNET_break (0);
+    return GNUNET_NO;
+  case GNUNET_BLOCK_EVALUATION_TYPE_NOT_SUPPORTED:
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _("Unsupported block type (%u) in request!\n"), record->type);
+    return GNUNET_NO;
+  default:
+    GNUNET_break (0);
+    return GNUNET_NO;
+  }
+  if (GNUNET_NO == frc->do_copy)
+  {
+    /* first time, we can use the original data */
+    pm = frc->pm;
+    frc->do_copy = GNUNET_YES;
+  }
+  else
+  {
+    /* two clients waiting for same reply, must copy for queueing */
+    pm = GNUNET_malloc (sizeof (struct PendingMessage) +
+                        ntohs (frc->pm->msg->size));
+    memcpy (pm, frc->pm,
+            sizeof (struct PendingMessage) + ntohs (frc->pm->msg->size));
+    pm->next = pm->prev = NULL;
+  }
+  GNUNET_STATISTICS_update (GDS_stats,
+                            gettext_noop ("# RESULTS queued for clients"), 1,
+                            GNUNET_NO);
+  reply = (struct GNUNET_DHT_ClientResultMessage *) &pm[1];
+  reply->unique_id = record->unique_id;
+#if DEBUG_DHT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Queueing reply to query %s for client %p\n", GNUNET_h2s (key),
+              record->client->client_handle);
+#endif
+  add_pending_message (record->client, pm);
+  if (GNUNET_YES == do_free)
+    remove_client_records (record->client, key, record);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Handle a reply we've received from another peer.  If the reply
+ * matches any of our pending queries, forward it to the respective
+ * client(s).
+ *
+ * @param expiration when will the reply expire
+ * @param key the query this reply is for
+ * @param get_path_length number of peers in 'get_path'
+ * @param get_path path the reply took on get
+ * @param put_path_length number of peers in 'put_path'
+ * @param put_path path the reply took on put
+ * @param type type of the reply
+ * @param data_size number of bytes in 'data'
+ * @param data application payload data
+ */
+void
+GDS_CLIENTS_handle_reply (struct GNUNET_TIME_Absolute expiration,
+                          const GNUNET_HashCode * key,
+                          unsigned int get_path_length,
+                          const struct GNUNET_PeerIdentity *get_path,
+                          unsigned int put_path_length,
+                          const struct GNUNET_PeerIdentity *put_path,
+                          enum GNUNET_BLOCK_Type type, size_t data_size,
+                          const void *data)
+{
+  struct ForwardReplyContext frc;
+  struct PendingMessage *pm;
+  struct GNUNET_DHT_ClientResultMessage *reply;
+  struct GNUNET_PeerIdentity *paths;
+  size_t msize;
+
+  if (NULL == GNUNET_CONTAINER_multihashmap_get (forward_map, key))
+  {
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop
+                              ("# REPLIES ignored for CLIENTS (no match)"), 1,
+                              GNUNET_NO);
+    return;                     /* no matching request, fast exit! */
+  }
+  msize =
+      sizeof (struct GNUNET_DHT_ClientResultMessage) + data_size +
+      (get_path_length + put_path_length) * sizeof (struct GNUNET_PeerIdentity);
+  if (msize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _("Could not pass reply to client, message too big!\n"));
+    return;
+  }
+  pm = (struct PendingMessage *) GNUNET_malloc (msize +
+                                                sizeof (struct PendingMessage));
+  reply = (struct GNUNET_DHT_ClientResultMessage *) &pm[1];
+  pm->msg = &reply->header;
+  reply->header.size = htons ((uint16_t) msize);
+  reply->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CLIENT_RESULT);
+  reply->type = htonl (type);
+  reply->get_path_length = htonl (get_path_length);
+  reply->put_path_length = htonl (put_path_length);
+  reply->unique_id = 0;         /* filled in later */
+  reply->expiration = GNUNET_TIME_absolute_hton (expiration);
+  reply->key = *key;
+  paths = (struct GNUNET_PeerIdentity *) &reply[1];
+  memcpy (paths, put_path,
+          sizeof (struct GNUNET_PeerIdentity) * put_path_length);
+  memcpy (&paths[put_path_length], get_path,
+          sizeof (struct GNUNET_PeerIdentity) * get_path_length);
+  memcpy (&paths[get_path_length + put_path_length], data, data_size);
+  frc.do_copy = GNUNET_NO;
+  frc.pm = pm;
+  frc.data = data;
+  frc.data_size = data_size;
+  frc.type = type;
+  GNUNET_CONTAINER_multihashmap_get_multiple (forward_map, key, &forward_reply,
+                                              &frc);
+  if (GNUNET_NO == frc.do_copy)
+  {
+    /* did not match any of the requests, free! */
+    GNUNET_STATISTICS_update (GDS_stats,
+                              gettext_noop
+                              ("# REPLIES ignored for CLIENTS (no match)"), 1,
+                              GNUNET_NO);
+    GNUNET_free (pm);
+  }
+}
+
+
+/**
+ * Check if some client is monitoring messages of this type and notify
+ * him in that case.
+ *
+ * @param mtype Type of the DHT message.
+ * @param exp When will this value expire.
+ * @param key Key of the result/request.
+ * @param putl number of entries in get_path.
+ * @param put_path peers on the PUT path (or NULL if not recorded).
+ * @param getl number of entries in get_path.
+ * @param get_path Peers on reply path (or NULL if not recorded).
+ * @param desired_replication_level Desired replication level.
+ * @param type Type of the result/request.
+ * @param data Pointer to the result data.
+ * @param size Number of bytes in data.
+ */
+void
+GDS_CLIENTS_process_monitor (uint16_t mtype,
+                             const struct GNUNET_TIME_Absolute exp,
+                             const GNUNET_HashCode *key,
+                             uint32_t putl,
+                             const struct GNUNET_PeerIdentity *put_path,
+                             uint32_t getl,
+                             const struct GNUNET_PeerIdentity *get_path,
+                             uint32_t desired_replication_level,
+                             enum GNUNET_BLOCK_Type type,
+                             const struct GNUNET_MessageHeader *data,
+                             uint16_t size)
+{
+  struct ClientMonitorRecord *m;
+  struct ClientList **cl;
+  unsigned int cl_size;
+
+  cl = NULL;
+  cl_size = 0;
+  for (m = monitor_head; NULL != m; m = m->next)
+  {
+    if ((GNUNET_BLOCK_TYPE_ANY == m->type || m->type == type) &&
+        (NULL == m->key ||
+         memcmp (key, m->key, sizeof(GNUNET_HashCode)) == 0))
+    {
+      struct PendingMessage *pm;
+      struct GNUNET_DHT_MonitorMessage *mmsg;
+      struct GNUNET_PeerIdentity *path;
+      size_t msize;
+      unsigned int i;
+
+      /* Don't send duplicates */
+      for (i = 0; i < cl_size; i++)
+        if (cl[i] == m->client)
+          break;
+      if (i < cl_size)
+        continue;
+      GNUNET_array_append (cl, cl_size, m->client);
+
+      msize = size;
+      msize += (getl + putl) * sizeof (struct GNUNET_PeerIdentity);
+      msize += sizeof (struct GNUNET_DHT_MonitorMessage);
+      msize += sizeof (struct PendingMessage);
+      pm = (struct PendingMessage *) GNUNET_malloc (msize);
+      mmsg = (struct GNUNET_DHT_MonitorMessage *) &pm[1];
+      pm->msg = (struct GNUNET_MessageHeader *) mmsg;
+      mmsg->header.size = htons (msize - sizeof (struct PendingMessage));
+      mmsg->header.type = htons (mtype);
+      mmsg->expiration = GNUNET_TIME_absolute_hton(exp);
+      memcpy (&mmsg->key, key, sizeof (GNUNET_HashCode));
+      mmsg->put_path_length = htonl(putl);
+      mmsg->get_path_length = htonl(getl);
+      mmsg->desired_replication_level = htonl (desired_replication_level);
+      path = (struct GNUNET_PeerIdentity *) &mmsg[1];
+      if (putl > 0)
+      {
+        memcpy (path, put_path, putl * sizeof (struct GNUNET_PeerIdentity));
+        path = &path[putl];
+      }
+      if (getl > 0)
+        memcpy (path, get_path, getl * sizeof (struct GNUNET_PeerIdentity));
+      if (size > 0)
+        memcpy (&path[getl], data, size);
+      add_pending_message (m->client, pm);
+    }
+  }
+  GNUNET_free_non_null (cl);
+}
+
+
+/**
+ * Initialize client subsystem.
+ *
+ * @param server the initialized server
+ */
+void
+GDS_CLIENTS_init (struct GNUNET_SERVER_Handle *server)
+{
+  static struct GNUNET_SERVER_MessageHandler plugin_handlers[] = {
+    {&handle_dht_local_put, NULL,
+     GNUNET_MESSAGE_TYPE_DHT_CLIENT_PUT, 0},
+    {&handle_dht_local_get, NULL,
+     GNUNET_MESSAGE_TYPE_DHT_CLIENT_GET, 0},
+    {&handle_dht_local_get_stop, NULL,
+     GNUNET_MESSAGE_TYPE_DHT_CLIENT_GET_STOP,
+     sizeof (struct GNUNET_DHT_ClientGetStopMessage)},
+    {&handle_dht_local_monitor, NULL,
+     GNUNET_MESSAGE_TYPE_DHT_MONITOR_GET,
+     sizeof (struct GNUNET_DHT_MonitorMessage)},
+    {NULL, NULL, 0, 0}
+  };
+  forward_map = GNUNET_CONTAINER_multihashmap_create (1024);
+  retry_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
+  GNUNET_SERVER_add_handlers (server, plugin_handlers);
+  GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
+}
+
+
+/**
+ * Shutdown client subsystem.
+ */
+void
+GDS_CLIENTS_done ()
+{
+  GNUNET_assert (client_head == NULL);
+  GNUNET_assert (client_tail == NULL);
+  if (GNUNET_SCHEDULER_NO_TASK != retry_task)
+  {
+    GNUNET_SCHEDULER_cancel (retry_task);
+    retry_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  GNUNET_assert (0 == GNUNET_CONTAINER_heap_get_size (retry_heap));
+  GNUNET_CONTAINER_heap_destroy (retry_heap);
+  retry_heap = NULL;
+  GNUNET_assert (0 == GNUNET_CONTAINER_multihashmap_size (forward_map));
+  GNUNET_CONTAINER_multihashmap_destroy (forward_map);
+  forward_map = NULL;
+}
+
+/* end of gnunet-service-dht_clients.c */