X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Fpeerstore%2Fpeerstore_api.c;h=2138b23ff322033757e4aefa6c457157ef90c47c;hb=0f649608b4d8c3f82fd1f240bc0d28c2713c7699;hp=5a2455014286f372656848b955b6cad8cf1c1782;hpb=d2f4cf2b57f6db7d788173ead9b8826deb3338f2;p=oweals%2Fgnunet.git

diff --git a/src/peerstore/peerstore_api.c b/src/peerstore/peerstore_api.c
index 5a2455014..2138b23ff 100644
--- a/src/peerstore/peerstore_api.c
+++ b/src/peerstore/peerstore_api.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 
+     (C) 2013-2014 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
@@ -17,11 +17,11 @@
      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
      Boston, MA 02111-1307, USA.
 */
-
 /**
  * @file peerstore/peerstore_api.c
  * @brief API for peerstore
  * @author Omar Tarabai
+ * @author Christian Grothoff
  */
 #include "platform.h"
 #include "gnunet_util_lib.h"
@@ -65,6 +65,26 @@ struct GNUNET_PEERSTORE_Handle
    */
   struct GNUNET_PEERSTORE_StoreContext *store_tail;
 
+  /**
+   * Head of active ITERATE requests.
+   */
+  struct GNUNET_PEERSTORE_IterateContext *iterate_head;
+
+  /**
+   * Tail of active ITERATE requests.
+   */
+  struct GNUNET_PEERSTORE_IterateContext *iterate_tail;
+
+  /**
+   * Hashmap of watch requests
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *watches;
+
+  /**
+   * Are we in the process of disconnecting but need to sync first?
+   */
+  int disconnecting;
+
 };
 
 /**
@@ -87,26 +107,150 @@ struct GNUNET_PEERSTORE_StoreContext
    */
   struct GNUNET_PEERSTORE_Handle *h;
 
-  /**
-   * MQ Envelope with store request message
-   */
-  struct GNUNET_MQ_Envelope *ev;
-
   /**
    * Continuation called with service response
    */
   GNUNET_PEERSTORE_Continuation cont;
 
   /**
-   * Closure for 'cont'
+   * Closure for @e cont
    */
   void *cont_cls;
 
   /**
-   * #GNUNET_YES / #GNUNET_NO
-   * if sent, cannot be canceled
+   * Which subsystem does the store?
+   */
+  char *sub_system;
+
+  /**
+   * Key for the store operation.
+   */
+  char *key;
+
+  /**
+   * Contains @e size bytes.
+   */
+  void *value;
+
+  /**
+   * Peer the store is for.
+   */
+  struct GNUNET_PeerIdentity peer;
+
+  /**
+   * Number of bytes in @e value.
+   */
+  size_t size;
+
+  /**
+   * When does the value expire?
+   */
+  struct GNUNET_TIME_Absolute expiry;
+
+  /**
+   * Options for the store operation.
+   */
+  enum GNUNET_PEERSTORE_StoreOption options;
+
+};
+
+/**
+ * Context for a iterate request
+ */
+struct GNUNET_PEERSTORE_IterateContext
+{
+  /**
+   * Kept in a DLL.
+   */
+  struct GNUNET_PEERSTORE_IterateContext *next;
+
+  /**
+   * Kept in a DLL.
+   */
+  struct GNUNET_PEERSTORE_IterateContext *prev;
+
+  /**
+   * Handle to the PEERSTORE service.
+   */
+  struct GNUNET_PEERSTORE_Handle *h;
+
+  /**
+   * Which subsystem does the store?
+   */
+  char *sub_system;
+
+  /**
+   * Peer the store is for.
+   */
+  struct GNUNET_PeerIdentity peer;
+
+  /**
+   * Key for the store operation.
+   */
+  char *key;
+
+  /**
+   * Operation timeout
+   */
+  struct GNUNET_TIME_Relative timeout;
+
+  /**
+   * Callback with each matching record
+   */
+  GNUNET_PEERSTORE_Processor callback;
+
+  /**
+   * Closure for @e callback
+   */
+  void *callback_cls;
+
+  /**
+   * #GNUNET_YES if we are currently processing records.
+   */
+  int iterating;
+
+  /**
+   * Task identifier for the function called
+   * on iterate request timeout
+   */
+  struct GNUNET_SCHEDULER_Task * timeout_task;
+
+};
+
+/**
+ * Context for a watch request
+ */
+struct GNUNET_PEERSTORE_WatchContext
+{
+  /**
+   * Kept in a DLL.
+   */
+  struct GNUNET_PEERSTORE_WatchContext *next;
+
+  /**
+   * Kept in a DLL.
+   */
+  struct GNUNET_PEERSTORE_WatchContext *prev;
+
+  /**
+   * Handle to the PEERSTORE service.
+   */
+  struct GNUNET_PEERSTORE_Handle *h;
+
+  /**
+   * Callback with each record received
+   */
+  GNUNET_PEERSTORE_Processor callback;
+
+  /**
+   * Closure for @e callback
    */
-  int request_sent;
+  void *callback_cls;
+
+  /**
+   * Hash of the combined key
+   */
+  struct GNUNET_HashCode keyhash;
 
 };
 
@@ -115,23 +259,61 @@ struct GNUNET_PEERSTORE_StoreContext
 /******************************************************************************/
 
 /**
- * When a response for store request is received
+ * When a response for iterate request is received
  *
- * @param cls a 'struct GNUNET_PEERSTORE_StoreContext *'
+ * @param cls a 'struct GNUNET_PEERSTORE_Handle *'
  * @param msg message received, NULL on timeout or fatal error
  */
-void handle_store_result (void *cls, const struct GNUNET_MessageHeader *msg);
+static void
+handle_iterate_result (void *cls, const struct GNUNET_MessageHeader *msg);
 
+/**
+ * When a watch record is received
+ *
+ * @param cls a 'struct GNUNET_PEERSTORE_Handle *'
+ * @param msg message received, NULL on timeout or fatal error
+ */
+static void
+handle_watch_result (void *cls, const struct GNUNET_MessageHeader *msg);
+
+/**
+ * Close the existing connection to PEERSTORE and reconnect.
+ *
+ * @param h handle to the service
+ */
 static void
 reconnect (struct GNUNET_PEERSTORE_Handle *h);
 
+
+/**
+ * Callback after MQ envelope is sent
+ *
+ * @param cls a `struct GNUNET_PEERSTORE_StoreContext *`
+ */
+static void
+store_request_sent (void *cls)
+{
+  struct GNUNET_PEERSTORE_StoreContext *sc = cls;
+  GNUNET_PEERSTORE_Continuation cont;
+  void *cont_cls;
+
+  cont = sc->cont;
+  cont_cls = sc->cont_cls;
+  GNUNET_PEERSTORE_store_cancel (sc);
+  if (NULL != cont)
+    cont (cont_cls, GNUNET_OK);
+}
+
+
 /**
  * MQ message handlers
  */
 static const struct GNUNET_MQ_MessageHandler mq_handlers[] = {
-    {&handle_store_result, GNUNET_MESSAGE_TYPE_PEERSTORE_STORE_RESULT_OK, sizeof(struct GNUNET_MessageHeader)},
-    {&handle_store_result, GNUNET_MESSAGE_TYPE_PEERSTORE_STORE_RESULT_FAIL, sizeof(struct GNUNET_MessageHeader)},
-    GNUNET_MQ_HANDLERS_END
+  {&handle_iterate_result, GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE_RECORD, 0},
+  {&handle_iterate_result, GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE_END,
+   sizeof (struct GNUNET_MessageHeader)},
+  {&handle_watch_result, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH_RECORD, 0},
+  GNUNET_MQ_HANDLERS_END
 };
 
 /******************************************************************************/
@@ -143,10 +325,57 @@ handle_client_error (void *cls, enum GNUNET_MQ_Error error)
 {
   struct GNUNET_PEERSTORE_Handle *h = cls;
 
-  GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Received an error notification from MQ of type: %d\n", error);
-  reconnect(h);
+  LOG (GNUNET_ERROR_TYPE_ERROR,
+       _("Received an error notification from MQ of type: %d\n"), error);
+  reconnect (h);
+}
+
+
+/**
+ * Iterator over previous watches to resend them
+ *
+ * @param cls the `struct GNUNET_PEERSTORE_Handle`
+ * @param key key for the watch
+ * @param value the `struct GNUNET_PEERSTORE_WatchContext *`
+ * @return #GNUNET_YES (continue to iterate)
+ */
+static int
+rewatch_it (void *cls, const struct GNUNET_HashCode *key, void *value)
+{
+  struct GNUNET_PEERSTORE_Handle *h = cls;
+  struct GNUNET_PEERSTORE_WatchContext *wc = value;
+  struct StoreKeyHashMessage *hm;
+  struct GNUNET_MQ_Envelope *ev;
+
+  ev = GNUNET_MQ_msg (hm, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH);
+  hm->keyhash = wc->keyhash;
+  GNUNET_MQ_send (h->mq, ev);
+  return GNUNET_YES;
 }
 
+
+/**
+ * Called when the iterate request is timedout
+ *
+ * @param cls a `struct GNUNET_PEERSTORE_IterateContext *`
+ * @param tc Scheduler task context (unused)
+ */
+static void
+iterate_timeout (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_PEERSTORE_IterateContext *ic = cls;
+  GNUNET_PEERSTORE_Processor callback;
+  void *callback_cls;
+
+  ic->timeout_task = NULL;
+  callback = ic->callback;
+  callback_cls = ic->callback_cls;
+  GNUNET_PEERSTORE_iterate_cancel (ic);
+  if (NULL != callback)
+    callback (callback_cls, NULL, _("timeout"));
+}
+
+
 /**
  * Close the existing connection to PEERSTORE and reconnect.
  *
@@ -155,11 +384,26 @@ handle_client_error (void *cls, enum GNUNET_MQ_Error error)
 static void
 reconnect (struct GNUNET_PEERSTORE_Handle *h)
 {
+  struct GNUNET_PEERSTORE_IterateContext *ic;
+  struct GNUNET_PEERSTORE_IterateContext *next;
+  GNUNET_PEERSTORE_Processor icb;
+  void *icb_cls;
+  struct GNUNET_PEERSTORE_StoreContext *sc;
+  struct GNUNET_MQ_Envelope *ev;
 
-  LOG(GNUNET_ERROR_TYPE_DEBUG, "Reconnecting...\n");
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Reconnecting...\n");
+  for (ic = h->iterate_head; NULL != ic; ic = next)
+  {
+    next = ic->next;
+    icb = ic->callback;
+    icb_cls = ic->callback_cls;
+    GNUNET_PEERSTORE_iterate_cancel (ic);
+    if (NULL != icb)
+      icb (icb_cls, NULL, _("Iteration canceled due to reconnection."));
+  }
   if (NULL != h->mq)
   {
-    GNUNET_MQ_destroy(h->mq);
+    GNUNET_MQ_destroy (h->mq);
     h->mq = NULL;
   }
   if (NULL != h->client)
@@ -167,17 +411,85 @@ reconnect (struct GNUNET_PEERSTORE_Handle *h)
     GNUNET_CLIENT_disconnect (h->client);
     h->client = NULL;
   }
+
   h->client = GNUNET_CLIENT_connect ("peerstore", h->cfg);
-  h->mq = GNUNET_MQ_queue_for_connection_client(h->client,
-      mq_handlers,
-      &handle_client_error,
-      h);
+  GNUNET_assert (NULL != h->client);
+  h->mq =
+      GNUNET_MQ_queue_for_connection_client (h->client, mq_handlers,
+                                             &handle_client_error, h);
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Resending pending requests after reconnect.\n");
+  if (NULL != h->watches)
+    GNUNET_CONTAINER_multihashmap_iterate (h->watches, &rewatch_it, h);
+  for (ic = h->iterate_head; NULL != ic; ic = ic->next)
+  {
+    ev =
+      PEERSTORE_create_record_mq_envelope (ic->sub_system, &ic->peer, ic->key,
+                                           NULL, 0, NULL, 0,
+                                           GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE);
+    GNUNET_MQ_send (h->mq, ev);
+    ic->timeout_task =
+        GNUNET_SCHEDULER_add_delayed (ic->timeout, &iterate_timeout, ic);
+  }
+  for (sc = h->store_head; NULL != sc; sc = sc->next)
+  {
+    ev =
+      PEERSTORE_create_record_mq_envelope (sc->sub_system, &sc->peer, sc->key,
+                                           sc->value, sc->size, &sc->expiry,
+                                           sc->options,
+                                           GNUNET_MESSAGE_TYPE_PEERSTORE_STORE);
+    GNUNET_MQ_notify_sent (ev, &store_request_sent, sc);
+    GNUNET_MQ_send (h->mq, ev);
+  }
+}
+
+
+/**
+ * Iterator over watch requests to cancel them.
+ *
+ * @param cls unsused
+ * @param key key to the watch request
+ * @param value watch context
+ * @return #GNUNET_YES to continue iteration
+ */
+static int
+destroy_watch (void *cls, const struct GNUNET_HashCode *key, void *value)
+{
+  struct GNUNET_PEERSTORE_WatchContext *wc = value;
+
+  GNUNET_PEERSTORE_watch_cancel (wc);
+  return GNUNET_YES;
+}
+
 
+/**
+ * Kill the connection to the service. This can be delayed in case of pending
+ * STORE requests and the user explicitly asked to sync first. Otherwise it is
+ * performed instantly.
+ *
+ * @param h Handle to the service.
+ */
+static void
+do_disconnect (struct GNUNET_PEERSTORE_Handle *h)
+{
+  if (NULL != h->mq)
+  {
+    GNUNET_MQ_destroy (h->mq);
+    h->mq = NULL;
+  }
+  if (NULL != h->client)
+  {
+    GNUNET_CLIENT_disconnect (h->client);
+    h->client = NULL;
+  }
+  GNUNET_free (h);
 }
 
+
 /**
  * Connect to the PEERSTORE service.
  *
+ * @param cfg configuration to use
  * @return NULL on error
  */
 struct GNUNET_PEERSTORE_Handle *
@@ -186,47 +498,78 @@ GNUNET_PEERSTORE_connect (const struct GNUNET_CONFIGURATION_Handle *cfg)
   struct GNUNET_PEERSTORE_Handle *h;
 
   h = GNUNET_new (struct GNUNET_PEERSTORE_Handle);
+
   h->client = GNUNET_CLIENT_connect ("peerstore", cfg);
-  if(NULL == h->client)
+  if (NULL == h->client)
   {
-    GNUNET_free(h);
+    GNUNET_free (h);
     return NULL;
   }
   h->cfg = cfg;
-  h->mq = GNUNET_MQ_queue_for_connection_client(h->client,
-      mq_handlers,
-      &handle_client_error,
-      h);
-  if(NULL == h->mq)
+  h->disconnecting = GNUNET_NO;
+  h->mq =
+      GNUNET_MQ_queue_for_connection_client (h->client, mq_handlers,
+                                             &handle_client_error, h);
+  if (NULL == h->mq)
   {
-    GNUNET_free(h);
+    GNUNET_CLIENT_disconnect (h->client);
+    GNUNET_free (h);
     return NULL;
   }
-  LOG(GNUNET_ERROR_TYPE_DEBUG, "New connection created\n");
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "New connection created\n");
   return h;
 }
 
+
 /**
- * Disconnect from the PEERSTORE service
- * Do not call in case of pending requests
+ * Disconnect from the PEERSTORE service. Any pending ITERATE and WATCH requests
+ * will be canceled.
+ * Any pending STORE requests will depend on @e snyc_first flag.
  *
  * @param h handle to disconnect
+ * @param sync_first send any pending STORE requests before disconnecting
  */
 void
-GNUNET_PEERSTORE_disconnect(struct GNUNET_PEERSTORE_Handle *h)
+GNUNET_PEERSTORE_disconnect (struct GNUNET_PEERSTORE_Handle *h, int sync_first)
 {
-  if(NULL != h->mq)
+  struct GNUNET_PEERSTORE_IterateContext *ic;
+  struct GNUNET_PEERSTORE_IterateContext *ic_iter;
+  struct GNUNET_PEERSTORE_StoreContext *sc;
+  struct GNUNET_PEERSTORE_StoreContext *sc_iter;
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Disconnecting.\n");
+  if (NULL != h->watches)
   {
-    GNUNET_MQ_destroy(h->mq);
-    h->mq = NULL;
+    GNUNET_CONTAINER_multihashmap_iterate (h->watches, &destroy_watch, NULL);
+    GNUNET_CONTAINER_multihashmap_destroy (h->watches);
+    h->watches = NULL;
   }
-  if (NULL != h->client)
+  ic_iter = h->iterate_head;
+  while (NULL != ic_iter)
   {
-    GNUNET_CLIENT_disconnect (h->client);
-    h->client = NULL;
+    GNUNET_break (0);
+    ic = ic_iter;
+    ic_iter = ic_iter->next;
+    GNUNET_PEERSTORE_iterate_cancel (ic);
   }
-  GNUNET_free(h);
-  LOG(GNUNET_ERROR_TYPE_DEBUG, "Disconnected, BYE!\n");
+  if (NULL != h->store_head)
+  {
+    if (GNUNET_YES == sync_first)
+    {
+      LOG (GNUNET_ERROR_TYPE_DEBUG,
+           "Delaying disconnection due to pending store requests.\n");
+      h->disconnecting = GNUNET_YES;
+      return;
+    }
+    sc_iter = h->store_head;
+    while (NULL != sc_iter)
+    {
+      sc = sc_iter;
+      sc_iter = sc_iter->next;
+      GNUNET_PEERSTORE_store_cancel (sc);
+    }
+  }
+  do_disconnect (h);
 }
 
 
@@ -234,133 +577,343 @@ GNUNET_PEERSTORE_disconnect(struct GNUNET_PEERSTORE_Handle *h)
 /*******************            STORE FUNCTIONS           *********************/
 /******************************************************************************/
 
+
+/**
+ * Cancel a store request
+ *
+ * @param sc Store request context
+ */
+void
+GNUNET_PEERSTORE_store_cancel (struct GNUNET_PEERSTORE_StoreContext *sc)
+{
+  struct GNUNET_PEERSTORE_Handle *h = sc->h;
+
+  GNUNET_CONTAINER_DLL_remove (sc->h->store_head, sc->h->store_tail, sc);
+  GNUNET_free (sc->sub_system);
+  GNUNET_free (sc->value);
+  GNUNET_free (sc->key);
+  GNUNET_free (sc);
+  if ((GNUNET_YES == h->disconnecting) && (NULL == h->store_head))
+    do_disconnect (h);
+}
+
+
+/**
+ * Store a new entry in the PEERSTORE.
+ * Note that stored entries can be lost in some cases
+ * such as power failure.
+ *
+ * @param h Handle to the PEERSTORE service
+ * @param sub_system name of the sub system
+ * @param peer Peer Identity
+ * @param key entry key
+ * @param value entry value BLOB
+ * @param size size of @e value
+ * @param expiry absolute time after which the entry is (possibly) deleted
+ * @param options options specific to the storage operation
+ * @param cont Continuation function after the store request is sent
+ * @param cont_cls Closure for @a cont
+ */
+struct GNUNET_PEERSTORE_StoreContext *
+GNUNET_PEERSTORE_store (struct GNUNET_PEERSTORE_Handle *h,
+                        const char *sub_system,
+                        const struct GNUNET_PeerIdentity *peer, const char *key,
+                        const void *value, size_t size,
+                        struct GNUNET_TIME_Absolute expiry,
+                        enum GNUNET_PEERSTORE_StoreOption options,
+                        GNUNET_PEERSTORE_Continuation cont, void *cont_cls)
+{
+  struct GNUNET_MQ_Envelope *ev;
+  struct GNUNET_PEERSTORE_StoreContext *sc;
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Storing value (size: %lu) for subsytem `%s', peer `%s', key `%s'\n",
+       size, sub_system, GNUNET_i2s (peer), key);
+  ev = PEERSTORE_create_record_mq_envelope (sub_system, peer, key, value, size,
+                                            &expiry, options,
+                                            GNUNET_MESSAGE_TYPE_PEERSTORE_STORE);
+  sc = GNUNET_new (struct GNUNET_PEERSTORE_StoreContext);
+
+  sc->sub_system = GNUNET_strdup (sub_system);
+  sc->peer = *peer;
+  sc->key = GNUNET_strdup (key);
+  sc->value = GNUNET_memdup (value, size);
+  sc->size = size;
+  sc->expiry = expiry;
+  sc->options = options;
+  sc->cont = cont;
+  sc->cont_cls = cont_cls;
+  sc->h = h;
+
+  GNUNET_CONTAINER_DLL_insert_tail (h->store_head, h->store_tail, sc);
+  GNUNET_MQ_notify_sent (ev, &store_request_sent, sc);
+  GNUNET_MQ_send (h->mq, ev);
+  return sc;
+
+}
+
+
+/******************************************************************************/
+/*******************           ITERATE FUNCTIONS          *********************/
+/******************************************************************************/
+
 /**
- * When a response for store request is received
+ * When a response for iterate request is received
  *
- * @param cls a 'struct GNUNET_PEERSTORE_StoreContext *'
+ * @param cls a `struct GNUNET_PEERSTORE_Handle *`
  * @param msg message received, NULL on timeout or fatal error
  */
-void handle_store_result (void *cls, const struct GNUNET_MessageHeader *msg)
+static void
+handle_iterate_result (void *cls, const struct GNUNET_MessageHeader *msg)
 {
   struct GNUNET_PEERSTORE_Handle *h = cls;
-  struct GNUNET_PEERSTORE_StoreContext *sc;
+  struct GNUNET_PEERSTORE_IterateContext *ic;
+  GNUNET_PEERSTORE_Processor callback;
+  void *callback_cls;
   uint16_t msg_type;
-  GNUNET_PEERSTORE_Continuation cont;
-  void *cont_cls;
+  struct GNUNET_PEERSTORE_Record *record;
+  int continue_iter;
 
-  sc = h->store_head;
-  if(NULL == sc)
+  ic = h->iterate_head;
+  if (NULL == ic)
   {
-    GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Unexpected store response, this should not happen.\n");
-    reconnect(h);
+    LOG (GNUNET_ERROR_TYPE_ERROR,
+         _("Unexpected iteration response, this should not happen.\n"));
+    reconnect (h);
     return;
   }
-  cont = sc->cont;
-  cont_cls = sc->cont_cls;
-  GNUNET_CONTAINER_DLL_remove(h->store_head, h->store_tail, sc);
-  GNUNET_free(sc);
-  if(NULL == msg) /* Connection error */
+  ic->iterating = GNUNET_YES;
+  callback = ic->callback;
+  callback_cls = ic->callback_cls;
+  if (NULL == msg)              /* Connection error */
   {
-    if(NULL != cont)
-      cont(cont_cls, GNUNET_SYSERR);
-    reconnect(h);
+    if (NULL != callback)
+      callback (callback_cls, NULL,
+                _("Error communicating with `PEERSTORE' service."));
+    reconnect (h);
     return;
   }
-  if(NULL != cont) /* Run continuation */
+  msg_type = ntohs (msg->type);
+  if (GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE_END == msg_type)
   {
-    msg_type = ntohs(msg->type);
-    if(GNUNET_MESSAGE_TYPE_PEERSTORE_STORE_RESULT_OK == msg_type)
-      cont(cont_cls, GNUNET_OK);
-    else if(GNUNET_MESSAGE_TYPE_PEERSTORE_STORE_RESULT_FAIL == msg_type)
-      cont(cont_cls, GNUNET_SYSERR);
+    ic->iterating = GNUNET_NO;
+    GNUNET_PEERSTORE_iterate_cancel (ic);
+    if (NULL != callback)
+      callback (callback_cls, NULL, NULL);
+    return;
+  }
+  if (NULL != callback)
+  {
+    record = PEERSTORE_parse_record_message (msg);
+    if (NULL == record)
+      continue_iter =
+          callback (callback_cls, NULL,
+                    _("Received a malformed response from service."));
+    else
+    {
+      continue_iter = callback (callback_cls, record, NULL);
+      PEERSTORE_destroy_record (record);
+    }
+    if (GNUNET_NO == continue_iter)
+      ic->callback = NULL;
   }
-
 }
 
+
 /**
- * Callback after MQ envelope is sent
+ * Cancel an iterate request
+ * Please do not call after the iterate request is done
  *
- * @param cls a 'struct GNUNET_PEERSTORE_StoreContext *'
+ * @param ic Iterate request context as returned by GNUNET_PEERSTORE_iterate()
  */
-void store_request_sent (void *cls)
+void
+GNUNET_PEERSTORE_iterate_cancel (struct GNUNET_PEERSTORE_IterateContext *ic)
 {
-  struct GNUNET_PEERSTORE_StoreContext *sc = cls;
+  if (NULL != ic->timeout_task)
+  {
+    GNUNET_SCHEDULER_cancel (ic->timeout_task);
+    ic->timeout_task = NULL;
+  }
+  if (GNUNET_NO == ic->iterating)
+  {
+    GNUNET_CONTAINER_DLL_remove (ic->h->iterate_head, ic->h->iterate_tail, ic);
+    GNUNET_free (ic->sub_system);
+    if (NULL != ic->key)
+      GNUNET_free (ic->key);
+    GNUNET_free (ic);
+  }
+  else
+    ic->callback = NULL;
+}
 
-  sc->request_sent = GNUNET_YES;
+
+/**
+ * Iterate over records matching supplied key information
+ *
+ * @param h handle to the PEERSTORE service
+ * @param sub_system name of sub system
+ * @param peer Peer identity (can be NULL)
+ * @param key entry key string (can be NULL)
+ * @param timeout time after which the iterate request is canceled
+ * @param callback function called with each matching record, all NULL's on end
+ * @param callback_cls closure for @a callback
+ * @return Handle to iteration request
+ */
+struct GNUNET_PEERSTORE_IterateContext *
+GNUNET_PEERSTORE_iterate (struct GNUNET_PEERSTORE_Handle *h,
+                          const char *sub_system,
+                          const struct GNUNET_PeerIdentity *peer,
+                          const char *key, struct GNUNET_TIME_Relative timeout,
+                          GNUNET_PEERSTORE_Processor callback,
+                          void *callback_cls)
+{
+  struct GNUNET_MQ_Envelope *ev;
+  struct GNUNET_PEERSTORE_IterateContext *ic;
+
+  ev = PEERSTORE_create_record_mq_envelope (sub_system, peer, key, NULL, 0,
+                                            NULL, 0,
+                                            GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE);
+  ic = GNUNET_new (struct GNUNET_PEERSTORE_IterateContext);
+
+  ic->callback = callback;
+  ic->callback_cls = callback_cls;
+  ic->h = h;
+  ic->sub_system = GNUNET_strdup (sub_system);
+  if (NULL != peer)
+    ic->peer = *peer;
+  if (NULL != key)
+    ic->key = GNUNET_strdup (key);
+  ic->timeout = timeout;
+  GNUNET_CONTAINER_DLL_insert_tail (h->iterate_head,
+                                    h->iterate_tail,
+                                    ic);
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Sending an iterate request for sub system `%s'\n", sub_system);
+  GNUNET_MQ_send (h->mq, ev);
+  ic->timeout_task =
+      GNUNET_SCHEDULER_add_delayed (timeout, &iterate_timeout, ic);
+  return ic;
 }
 
+
+/******************************************************************************/
+/*******************            WATCH FUNCTIONS           *********************/
+/******************************************************************************/
+
 /**
- * Cancel a store request
+ * When a watch record is received
  *
- * @param sc Store request context
+ * @param cls a `struct GNUNET_PEERSTORE_Handle *`
+ * @param msg message received, NULL on timeout or fatal error
  */
-void
-GNUNET_PEERSTORE_store_cancel (struct GNUNET_PEERSTORE_StoreContext *sc)
+static void
+handle_watch_result (void *cls, const struct GNUNET_MessageHeader *msg)
 {
-  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
-          "Canceling store request.\n");
-  if(GNUNET_NO == sc->request_sent)
+  struct GNUNET_PEERSTORE_Handle *h = cls;
+  struct GNUNET_PEERSTORE_Record *record;
+  struct GNUNET_HashCode keyhash;
+  struct GNUNET_PEERSTORE_WatchContext *wc;
+
+  if (NULL == msg)
   {
-    if(NULL != sc->ev)
-      GNUNET_MQ_discard(sc->ev);
-    GNUNET_CONTAINER_DLL_remove(sc->h->store_head, sc->h->store_tail, sc);
-    GNUNET_free(sc);
+    LOG (GNUNET_ERROR_TYPE_ERROR,
+         _
+         ("Problem receiving a watch response, no way to determine which request.\n"));
+    reconnect (h);
+    return;
   }
-  else
-  { /* request already sent, will have to wait for response */
-    sc->cont = NULL;
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Received a watch record from service.\n");
+  record = PEERSTORE_parse_record_message (msg);
+  PEERSTORE_hash_key (record->sub_system, record->peer, record->key, &keyhash);
+  // FIXME: what if there are multiple watches for the same key?
+  wc = GNUNET_CONTAINER_multihashmap_get (h->watches, &keyhash);
+  if (NULL == wc)
+  {
+    LOG (GNUNET_ERROR_TYPE_ERROR,
+         _("Received a watch result for a non existing watch.\n"));
+    PEERSTORE_destroy_record (record);
+    reconnect (h);
+    return;
   }
-
+  if (NULL != wc->callback)
+    wc->callback (wc->callback_cls, record, NULL);
+  PEERSTORE_destroy_record (record);
 }
 
+
 /**
- * Store a new entry in the PEERSTORE
+ * Cancel a watch request
  *
- * @param h Handle to the PEERSTORE service
- * @param sub_system name of the sub system
- * @param peer Peer Identity
- * @param key entry key
- * @param value entry value BLOB
- * @param size size of 'value'
- * @param expiry absolute time after which the entry is (possibly) deleted
- * @param cont Continuation function after the store request is processed
- * @param cont_cls Closure for 'cont'
+ * @param wc handle to the watch request
  */
-struct GNUNET_PEERSTORE_StoreContext *
-GNUNET_PEERSTORE_store (struct GNUNET_PEERSTORE_Handle *h,
-    const char *sub_system,
-    const struct GNUNET_PeerIdentity *peer,
-    const char *key,
-    const void *value,
-    size_t size,
-    struct GNUNET_TIME_Absolute expiry,
-    GNUNET_PEERSTORE_Continuation cont,
-    void *cont_cls)
+void
+GNUNET_PEERSTORE_watch_cancel (struct GNUNET_PEERSTORE_WatchContext *wc)
 {
+  struct GNUNET_PEERSTORE_Handle *h = wc->h;
   struct GNUNET_MQ_Envelope *ev;
-  struct GNUNET_PEERSTORE_StoreContext *sc;
+  struct StoreKeyHashMessage *hm;
 
   LOG (GNUNET_ERROR_TYPE_DEBUG,
-      "Storing value (size: %lu) for subsytem `%s', peer `%s', key `%s'\n",
-      size, sub_system, GNUNET_i2s (peer), key);
-  ev = PEERSTORE_create_record_mq_envelope(sub_system,
-      peer,
-      key,
-      value,
-      size,
-      expiry,
-      GNUNET_MESSAGE_TYPE_PEERSTORE_STORE);
-  GNUNET_MQ_send(h->mq, ev);
-  GNUNET_MQ_notify_sent(ev, &store_request_sent, ev);
-  sc = GNUNET_new(struct GNUNET_PEERSTORE_StoreContext);
-  sc->ev = ev;
-  sc->cont = cont;
-  sc->cont_cls = cont_cls;
-  sc->h = h;
-  sc->request_sent = GNUNET_NO;
-  GNUNET_CONTAINER_DLL_insert(h->store_head, h->store_tail, sc);
-  return sc;
+       "Canceling watch.\n");
+  ev = GNUNET_MQ_msg (hm, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH_CANCEL);
+  hm->keyhash = wc->keyhash;
+  GNUNET_MQ_send (h->mq, ev);
+  GNUNET_CONTAINER_multihashmap_remove (h->watches,
+                                        &wc->keyhash,
+                                        wc);
+  GNUNET_free (wc);
+}
+
 
+/**
+ * Request watching a given key
+ * User will be notified with any new values added to key
+ *
+ * @param h handle to the PEERSTORE service
+ * @param sub_system name of sub system
+ * @param peer Peer identity
+ * @param key entry key string
+ * @param callback function called with each new value
+ * @param callback_cls closure for @a callback
+ * @return Handle to watch request
+ */
+struct GNUNET_PEERSTORE_WatchContext *
+GNUNET_PEERSTORE_watch (struct GNUNET_PEERSTORE_Handle *h,
+                        const char *sub_system,
+                        const struct GNUNET_PeerIdentity *peer, const char *key,
+                        GNUNET_PEERSTORE_Processor callback, void *callback_cls)
+{
+  struct GNUNET_MQ_Envelope *ev;
+  struct StoreKeyHashMessage *hm;
+  struct GNUNET_PEERSTORE_WatchContext *wc;
+
+  GNUNET_assert (NULL != sub_system);
+  GNUNET_assert (NULL != peer);
+  GNUNET_assert (NULL != key);
+  ev = GNUNET_MQ_msg (hm, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH);
+  PEERSTORE_hash_key (sub_system,
+                      peer,
+                      key,
+                      &hm->keyhash);
+  wc = GNUNET_new (struct GNUNET_PEERSTORE_WatchContext);
+  wc->callback = callback;
+  wc->callback_cls = callback_cls;
+  wc->h = h;
+  wc->keyhash = hm->keyhash;
+  if (NULL == h->watches)
+    h->watches = GNUNET_CONTAINER_multihashmap_create (5, GNUNET_NO);
+  GNUNET_assert (GNUNET_OK ==
+                 GNUNET_CONTAINER_multihashmap_put (h->watches,
+                                                    &wc->keyhash,
+                                                    wc,
+                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Sending a watch request for ss `%s', peer `%s', key `%s'.\n",
+       sub_system,
+       GNUNET_i2s (peer),
+       key);
+  GNUNET_MQ_send (h->mq, ev);
+  return wc;
 }
 
 /* end of peerstore_api.c */