first batch of license fixes (boring)
[oweals/gnunet.git] / src / set / gnunet-service-set.c
index b5aa659be848d2836160fefd3f774608656c498b..3e0955108e094f91cc5560b997b01a8c76e5898a 100644 (file)
@@ -1,66 +1,67 @@
 /*
       This file is part of GNUnet
-      (C) 2013 Christian Grothoff (and other contributing authors)
+      Copyright (C) 2013-2017 GNUnet e.V.
 
-      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 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 of the License,
+      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.
+      Affero General Public License for more details.
 */
-
 /**
  * @file set/gnunet-service-set.c
  * @brief two-peer set operations
  * @author Florian Dold
+ * @author Christian Grothoff
  */
 #include "gnunet-service-set.h"
-#include "set_protocol.h"
+#include "gnunet-service-set_union.h"
+#include "gnunet-service-set_intersection.h"
+#include "gnunet-service-set_protocol.h"
+#include "gnunet_statistics_service.h"
+
+/**
+ * How long do we hold on to an incoming channel if there is
+ * no local listener before giving up?
+ */
+#define INCOMING_CHANNEL_TIMEOUT GNUNET_TIME_UNIT_MINUTES
 
 
 /**
- * State of an operation where the peer has connected to us, but is not yet
- * evaluating a set operation.  Once the peer has sent a concrete request, and
- * the client has accepted or rejected it, this information will be deleted
- * and replaced by the real set operation state.
+ * Lazy copy requests made by a client.
  */
-struct OperationState
+struct LazyCopyRequest
 {
   /**
-   * The identity of the requesting peer.  Needs to
-   * be stored here as the op spec might not have been created yet.
+   * Kept in a DLL.
+   */
+  struct LazyCopyRequest *prev;
+
+  /**
+   * Kept in a DLL.
    */
-  struct GNUNET_PeerIdentity peer;
+  struct LazyCopyRequest *next;
 
   /**
-   * Unique request id for the request from
-   * a remote peer, sent to the client, which will
-   * accept or reject the request.
-   * Set to '0' iff the request has not been
-   * suggested yet.
+   * Which set are we supposed to copy?
    */
-  uint32_t suggest_id;
+  struct Set *source_set;
 
   /**
-   * Timeout task, if the incoming peer has not been accepted
-   * after the timeout, it will be disconnected.
+   * Cookie identifying the request.
    */
-  GNUNET_SCHEDULER_TaskIdentifier timeout_task;
+  uint32_t cookie;
+
 };
 
 
 /**
- * A listener is inhabited by a client, and
- * waits for evaluation requests from remote peers.
+ * A listener is inhabited by a client, and waits for evaluation
+ * requests from remote peers.
  */
 struct Listener
 {
@@ -75,651 +76,1010 @@ struct Listener
   struct Listener *prev;
 
   /**
-   * Client that owns the listener.
-   * Only one client may own a listener.
+   * Head of DLL of operations this listener is responsible for.
+   * Once the client has accepted/declined the operation, the
+   * operation is moved to the respective set's operation DLLS.
    */
-  struct GNUNET_SERVER_Client *client;
+  struct Operation *op_head;
 
   /**
-   * Message queue for the client
+   * Tail of DLL of operations this listener is responsible for.
+   * Once the client has accepted/declined the operation, the
+   * operation is moved to the respective set's operation DLLS.
    */
-  struct GNUNET_MQ_Handle *client_mq;
+  struct Operation *op_tail;
 
   /**
-   * The type of the operation.
+   * Client that owns the listener.
+   * Only one client may own a listener.
    */
-  enum GNUNET_SET_OperationType operation;
+  struct ClientState *cs;
+
+  /**
+   * The port we are listening on with CADET.
+   */
+  struct GNUNET_CADET_Port *open_port;
 
   /**
    * Application ID for the operation, used to distinguish
    * multiple operations of the same type with the same peer.
    */
   struct GNUNET_HashCode app_id;
+
+  /**
+   * The type of the operation.
+   */
+  enum GNUNET_SET_OperationType operation;
 };
 
 
 /**
- * Configuration of our local peer.
+ * Handle to the cadet service, used to listen for and connect to
+ * remote peers.
+ */
+static struct GNUNET_CADET_Handle *cadet;
+
+/**
+ * DLL of lazy copy requests by this client.
  */
-static const struct GNUNET_CONFIGURATION_Handle *configuration;
+static struct LazyCopyRequest *lazy_copy_head;
 
 /**
- * Handle to the mesh service, used
- * to listen for and connect to remote peers.
+ * DLL of lazy copy requests by this client.
  */
-static struct GNUNET_MESH_Handle *mesh;
+static struct LazyCopyRequest *lazy_copy_tail;
 
 /**
- * Sets are held in a doubly linked list.
+ * Generator for unique cookie we set per lazy copy request.
  */
-static struct Set *sets_head;
+static uint32_t lazy_copy_cookie;
 
 /**
- * Sets are held in a doubly linked list.
+ * Statistics handle.
  */
-static struct Set *sets_tail;
+struct GNUNET_STATISTICS_Handle *_GSS_statistics;
 
 /**
  * Listeners are held in a doubly linked list.
  */
-static struct Listener *listeners_head;
+static struct Listener *listener_head;
 
 /**
  * Listeners are held in a doubly linked list.
  */
-static struct Listener *listeners_tail;
+static struct Listener *listener_tail;
 
 /**
- * Incoming sockets from remote peers are
- * held in a doubly linked list.
+ * Number of active clients.
  */
-static struct Operation *incoming_head;
+static unsigned int num_clients;
 
 /**
- * Incoming sockets from remote peers are
- * held in a doubly linked list.
+ * Are we in shutdown? if #GNUNET_YES and the number of clients
+ * drops to zero, disconnect from CADET.
  */
-static struct Operation *incoming_tail;
+static int in_shutdown;
 
 /**
- * Counter for allocating unique IDs for clients,
- * used to identify incoming operation requests from remote peers,
- * that the client can choose to accept or refuse.
+ * Counter for allocating unique IDs for clients, used to identify
+ * incoming operation requests from remote peers, that the client can
+ * choose to accept or refuse.  0 must not be used (reserved for
+ * uninitialized).
  */
-static uint32_t suggest_id = 1;
+static uint32_t suggest_id;
 
 
 /**
- * Get set that is owned by the given client, if any.
+ * Get the incoming socket associated with the given id.
  *
- * @param client client to look for
- * @return set that the client owns, NULL if the client
- *         does not own a set
+ * @param listener the listener to look in
+ * @param id id to look for
+ * @return the incoming socket associated with the id,
+ *         or NULL if there is none
  */
-static struct Set *
-set_get (struct GNUNET_SERVER_Client *client)
+static struct Operation *
+get_incoming (uint32_t id)
 {
-  struct Set *set;
-
-  for (set = sets_head; NULL != set; set = set->next)
-    if (set->client == client)
-      return set;
+  for (struct Listener *listener = listener_head;
+       NULL != listener;
+       listener = listener->next)
+  {
+    for (struct Operation *op = listener->op_head; NULL != op; op = op->next)
+      if (op->suggest_id == id)
+        return op;
+  }
   return NULL;
 }
 
 
 /**
- * Get the listener associated with the given client, if any.
+ * Destroy an incoming request from a remote peer
  *
- * @param client the client
- * @return listener associated with the client, NULL
- *         if there isn't any
+ * @param op remote request to destroy
  */
-static struct Listener *
-listener_get (struct GNUNET_SERVER_Client *client)
+static void
+incoming_destroy (struct Operation *op)
 {
   struct Listener *listener;
+  struct GNUNET_CADET_Channel *channel;
 
-  for (listener = listeners_head; NULL != listener; listener = listener->next)
-    if (listener->client == client)
-      return listener;
-  return NULL;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Destroying incoming operation %p\n",
+              op);
+  if (NULL != (listener = op->listener))
+  {
+    GNUNET_CONTAINER_DLL_remove (listener->op_head,
+                                 listener->op_tail,
+                                 op);
+    op->listener = NULL;
+  }
+  if (NULL != op->timeout_task)
+  {
+    GNUNET_SCHEDULER_cancel (op->timeout_task);
+    op->timeout_task = NULL;
+  }
+  if (NULL != (channel = op->channel))
+  {
+    op->channel = NULL;
+    GNUNET_CADET_channel_destroy (channel);
+  }
 }
 
 
 /**
- * Get the incoming socket associated with the given id.
- *
- * @param id id to look for
- * @return the incoming socket associated with the id,
- *         or NULL if there is none
+ * Context for the #garbage_collect_cb().
  */
-static struct Operation *
-get_incoming (uint32_t id)
+struct GarbageContext
 {
-  struct Operation *op;
 
-  for (op = incoming_head; NULL != op; op = op->next)
-    if (op->state->suggest_id == id)
-    {
-      // FIXME: remove this assertion once the corresponding bug is gone!
-      GNUNET_assert (GNUNET_YES == op->is_incoming);
-      return op;
-    }
-  return NULL;
-}
+  /**
+   * Map for which we are garbage collecting removed elements.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *map;
+
+  /**
+   * Lowest generation for which an operation is still pending.
+   */
+  unsigned int min_op_generation;
+
+  /**
+   * Largest generation for which an operation is still pending.
+   */
+  unsigned int max_op_generation;
+
+};
 
 
 /**
- * Destroy a listener, free all resources associated with it.
+ * Function invoked to check if an element can be removed from
+ * the set's history because it is no longer needed.
  *
- * @param listener listener to destroy
+ * @param cls the `struct GarbageContext *`
+ * @param key key of the element in the map
+ * @param value the `struct ElementEntry *`
+ * @return #GNUNET_OK (continue to iterate)
  */
-static void
-listener_destroy (struct Listener *listener)
+static int
+garbage_collect_cb (void *cls,
+                    const struct GNUNET_HashCode *key,
+                    void *value)
 {
-  /* If the client is not dead yet, destroy it.
-   * The client's destroy callback will destroy the listener again. */
-  if (NULL != listener->client)
-  {
-    struct GNUNET_SERVER_Client *client = listener->client;
-    listener->client = NULL;
-    GNUNET_SERVER_client_disconnect (client);
-    return;
-  }
-  if (NULL != listener->client_mq)
-  {
-    GNUNET_MQ_destroy (listener->client_mq);
-    listener->client_mq = NULL;
-  }
-  GNUNET_CONTAINER_DLL_remove (listeners_head, listeners_tail, listener);
-  GNUNET_free (listener);
+  //struct GarbageContext *gc = cls;
+  //struct ElementEntry *ee = value;
+
+  //if (GNUNET_YES != ee->removed)
+  //  return GNUNET_OK;
+  //if ( (gc->max_op_generation < ee->generation_added) ||
+  //     (ee->generation_removed > gc->min_op_generation) )
+  //{
+  //  GNUNET_assert (GNUNET_YES ==
+  //                 GNUNET_CONTAINER_multihashmap_remove (gc->map,
+  //                                                       key,
+  //                                                       ee));
+  //  GNUNET_free (ee);
+  //}
+  return GNUNET_OK;
 }
 
 
 /**
  * Collect and destroy elements that are not needed anymore, because
- * their lifetime (as determined by their generation) does not overlap with any active
- * set operation.
+ * their lifetime (as determined by their generation) does not overlap
+ * with any active set operation.
  *
- * We hereby replace the old element hashmap with a new one, instead of removing elements.
+ * @param set set to garbage collect
  */
-void
+static void
 collect_generation_garbage (struct Set *set)
 {
-  struct GNUNET_CONTAINER_MultiHashMapIterator *iter;
-  struct ElementEntry *ee;
-  struct GNUNET_CONTAINER_MultiHashMap *new_elements;
-  int res;
-  struct Operation *op;
+  struct GarbageContext gc;
 
-  new_elements = GNUNET_CONTAINER_multihashmap_create (1, GNUNET_NO);
-  iter = GNUNET_CONTAINER_multihashmap_iterator_create (set->elements);
-  while (GNUNET_OK ==
-         (res = GNUNET_CONTAINER_multihashmap_iterator_next (iter, NULL, (const void **) &ee)))
+  gc.min_op_generation = UINT_MAX;
+  gc.max_op_generation = 0;
+  for (struct Operation *op = set->ops_head; NULL != op; op = op->next)
   {
-    if (GNUNET_NO == ee->removed)
-      goto still_needed;
-    for (op = set->ops_head; NULL != op; op = op->next)
-      if ((op->generation_created >= ee->generation_added) &&
-          (op->generation_created < ee->generation_removed))
-        goto still_needed;
-    GNUNET_free (ee);
-    continue;
-still_needed:
-    // we don't expect collisions, thus the replace option
-    GNUNET_CONTAINER_multihashmap_put (new_elements, &ee->element_hash, ee,
-                                       GNUNET_CONTAINER_MULTIHASHMAPOPTION_REPLACE);
+    gc.min_op_generation = GNUNET_MIN (gc.min_op_generation,
+                                       op->generation_created);
+    gc.max_op_generation = GNUNET_MAX (gc.max_op_generation,
+                                       op->generation_created);
   }
-  GNUNET_CONTAINER_multihashmap_iterator_destroy (iter);
-  GNUNET_CONTAINER_multihashmap_destroy (set->elements);
-  set->elements = new_elements;
+  gc.map = set->content->elements;
+  GNUNET_CONTAINER_multihashmap_iterate (set->content->elements,
+                                         &garbage_collect_cb,
+                                         &gc);
 }
 
 
 /**
- * Destroy the given operation.  Call the implementation-specific cancel function
- * of the operation.  Disconnects from the remote peer.
- * Does not disconnect the client, as there may be multiple operations per set.
+ * Is @a generation in the range of exclusions?
  *
- * @param op operation to destroy
+ * @param generation generation to query
+ * @param excluded array of generations where the element is excluded
+ * @param excluded_size length of the @a excluded array
+ * @return #GNUNET_YES if @a generation is in any of the ranges
  */
-void
-_GSS_operation_destroy (struct Operation *op)
+static int
+is_excluded_generation (unsigned int generation,
+                        struct GenerationRange *excluded,
+                        unsigned int excluded_size)
 {
-  struct Set *set;
-  struct GNUNET_MESH_Channel *channel;
-
-  if (NULL == op->vt)
-    return;
+  for (unsigned int i = 0; i < excluded_size; i++)
+    if ( (generation >= excluded[i].start) &&
+         (generation < excluded[i].end) )
+      return GNUNET_YES;
+  return GNUNET_NO;
+}
 
-  set = op->spec->set;
 
-  GNUNET_assert (GNUNET_NO == op->is_incoming);
-  GNUNET_assert (NULL != op->spec);
-  GNUNET_CONTAINER_DLL_remove (op->spec->set->ops_head,
-                               op->spec->set->ops_tail,
-                               op);
+/**
+ * Is element @a ee part of the set during @a query_generation?
+ *
+ * @param ee element to test
+ * @param query_generation generation to query
+ * @param excluded array of generations where the element is excluded
+ * @param excluded_size length of the @a excluded array
+ * @return #GNUNET_YES if the element is in the set, #GNUNET_NO if not
+ */
+static int
+is_element_of_generation (struct ElementEntry *ee,
+                          unsigned int query_generation,
+                          struct GenerationRange *excluded,
+                          unsigned int excluded_size)
+{
+  struct MutationEvent *mut;
+  int is_present;
+
+  GNUNET_assert (NULL != ee->mutations);
+  if (GNUNET_YES ==
+      is_excluded_generation (query_generation,
+                              excluded,
+                              excluded_size))
+  {
+    GNUNET_break (0);
+    return GNUNET_NO;
+  }
 
-  op->vt->cancel (op);
-  op->vt = NULL;
+  is_present = GNUNET_NO;
 
-  if (NULL != op->spec)
+  /* Could be made faster with binary search, but lists
+     are small, so why bother. */
+  for (unsigned int i = 0; i < ee->mutations_size; i++)
   {
-    if (NULL != op->spec->context_msg)
+    mut = &ee->mutations[i];
+
+    if (mut->generation > query_generation)
     {
-      GNUNET_free (op->spec->context_msg);
-      op->spec->context_msg = NULL;
+      /* The mutation doesn't apply to our generation
+         anymore.  We can'b break here, since mutations aren't
+         sorted by generation. */
+      continue;
     }
-    GNUNET_free (op->spec);
-    op->spec = NULL;
-  }
 
-  if (NULL != op->mq)
-  {
-    GNUNET_MQ_destroy (op->mq);
-    op->mq = NULL;
-  }
+    if (GNUNET_YES ==
+        is_excluded_generation (mut->generation,
+                                excluded,
+                                excluded_size))
+    {
+      /* The generation is excluded (because it belongs to another
+         fork via a lazy copy) and thus mutations aren't considered
+         for membership testing. */
+      continue;
+    }
 
-  if (NULL != (channel = op->channel))
-  {
-    op->channel = NULL;
-    GNUNET_MESH_channel_destroy (channel);
-  }
+    /* This would be an inconsistency in how we manage mutations. */
+    if ( (GNUNET_YES == is_present) &&
+         (GNUNET_YES == mut->added) )
+      GNUNET_assert (0);
+    /* Likewise. */
+    if ( (GNUNET_NO == is_present) &&
+         (GNUNET_NO == mut->added) )
+      GNUNET_assert (0);
 
-  collect_generation_garbage (set);
+    is_present = mut->added;
+  }
 
-  /* We rely on the channel end handler to free 'op'. When 'op->channel' was NULL,
-   * there was a channel end handler that will free 'op' on the call stack. */
+  return is_present;
 }
 
 
 /**
- * Iterator over hash map entries to free
- * element entries.
+ * Is element @a ee part of the set used by @a op?
  *
- * @param cls closure
- * @param key current key code
- * @param value a `struct ElementEntry *` to be free'd
- * @return #GNUNET_YES if we should continue to
- *         iterate,
- *         #GNUNET_NO if not.
+ * @param ee element to test
+ * @param op operation the defines the set and its generation
+ * @return #GNUNET_YES if the element is in the set, #GNUNET_NO if not
  */
-static int
-destroy_elements_iterator (void *cls,
-                           const struct GNUNET_HashCode * key,
-                           void *value)
+int
+_GSS_is_element_of_operation (struct ElementEntry *ee,
+                              struct Operation *op)
 {
-  struct ElementEntry *ee = value;
-
-  GNUNET_free (ee);
-  return GNUNET_YES;
+  return is_element_of_generation (ee,
+                                   op->generation_created,
+                                   op->set->excluded_generations,
+                                   op->set->excluded_generations_size);
 }
 
 
 /**
- * Destroy a set, and free all resources associated with it.
+ * Destroy the given operation.  Used for any operation where both
+ * peers were known and that thus actually had a vt and channel.  Must
+ * not be used for operations where 'listener' is still set and we do
+ * not know the other peer.
  *
- * @param set the set to destroy
+ * Call the implementation-specific cancel function of the operation.
+ * Disconnects from the remote peer.  Does not disconnect the client,
+ * as there may be multiple operations per set.
+ *
+ * @param op operation to destroy
+ * @param gc #GNUNET_YES to perform garbage collection on the set
  */
-static void
-set_destroy (struct Set *set)
+void
+_GSS_operation_destroy (struct Operation *op,
+                        int gc)
 {
-  /* If the client is not dead yet, destroy it.
-   * The client's destroy callback will destroy the set again.
-   * We do this so that the channel end handler still has a valid set handle
-   * to destroy. */
-  if (NULL != set->client)
+  struct Set *set = op->set;
+  struct GNUNET_CADET_Channel *channel;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Destroying operation %p\n",
+              op);
+  GNUNET_assert (NULL == op->listener);
+  if (NULL != op->state)
   {
-    struct GNUNET_SERVER_Client *client = set->client;
-    set->client = NULL;
-    GNUNET_SERVER_client_disconnect (client);
-    return;
+    set->vt->cancel (op);
+    op->state = NULL;
   }
-  GNUNET_assert (NULL != set->state);
-  while (NULL != set->ops_head)
-    _GSS_operation_destroy (set->ops_head);
-  set->vt->destroy_set (set->state);
-  set->state = NULL;
-  if (NULL != set->client_mq)
+  if (NULL != set)
   {
-    GNUNET_MQ_destroy (set->client_mq);
-    set->client_mq = NULL;
+    GNUNET_CONTAINER_DLL_remove (set->ops_head,
+                                 set->ops_tail,
+                                 op);
+    op->set = NULL;
   }
-  if (NULL != set->iter)
+  if (NULL != op->context_msg)
   {
-    GNUNET_CONTAINER_multihashmap_iterator_destroy (set->iter);
-    set->iter = NULL;
+    GNUNET_free (op->context_msg);
+    op->context_msg = NULL;
   }
-  GNUNET_CONTAINER_DLL_remove (sets_head, sets_tail, set);
-  if (NULL != set->elements)
+  if (NULL != (channel = op->channel))
   {
-    // free all elements in the hashtable, before destroying the table
-    GNUNET_CONTAINER_multihashmap_iterate (set->elements,
-                                           destroy_elements_iterator, NULL);
-    GNUNET_CONTAINER_multihashmap_destroy (set->elements);
-    set->elements = NULL;
+    /* This will free op; called conditionally as this helper function
+       is also called from within the channel disconnect handler. */
+    op->channel = NULL;
+    GNUNET_CADET_channel_destroy (channel);
   }
-  GNUNET_free (set);
+  if ( (NULL != set) &&
+       (GNUNET_YES == gc) )
+    collect_generation_garbage (set);
+  /* We rely on the channel end handler to free 'op'. When 'op->channel' was NULL,
+   * there was a channel end handler that will free 'op' on the call stack. */
 }
 
 
 /**
- * Clean up after a client has disconnected
+ * Callback called when a client connects to the service.
  *
- * @param cls closure, unused
- * @param client the client to clean up after
+ * @param cls closure for the service
+ * @param c the new client that connected to the service
+ * @param mq the message queue used to send messages to the client
+ * @return @a `struct ClientState`
  */
-static void
-handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
+static void *
+client_connect_cb (void *cls,
+                  struct GNUNET_SERVICE_Client *c,
+                  struct GNUNET_MQ_Handle *mq)
 {
-  struct Set *set;
-  struct Listener *listener;
+  struct ClientState *cs;
 
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "client disconnected, cleaning up\n");
-  set = set_get (client);
-  if (NULL != set)
-  {
-    set->client = NULL;
-    set_destroy (set);
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "(client's set destroyed)\n");
-  }
-  listener = listener_get (client);
-  if (NULL != listener)
-  {
-    listener->client = NULL;
-    listener_destroy (listener);
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "(client's listener destroyed)\n");
-  }
+  num_clients++;
+  cs = GNUNET_new (struct ClientState);
+  cs->client = c;
+  cs->mq = mq;
+  return cs;
 }
 
 
 /**
- * Destroy an incoming request from a remote peer
+ * Iterator over hash map entries to free element entries.
  *
- * @param incoming remote request to destroy
+ * @param cls closure
+ * @param key current key code
+ * @param value a `struct ElementEntry *` to be free'd
+ * @return #GNUNET_YES (continue to iterate)
  */
-static void
-incoming_destroy (struct Operation *incoming)
+static int
+destroy_elements_iterator (void *cls,
+                           const struct GNUNET_HashCode *key,
+                           void *value)
 {
-  GNUNET_assert (GNUNET_YES == incoming->is_incoming);
-  GNUNET_CONTAINER_DLL_remove (incoming_head, incoming_tail, incoming);
-  if (GNUNET_SCHEDULER_NO_TASK != incoming->state->timeout_task)
-  {
-    GNUNET_SCHEDULER_cancel (incoming->state->timeout_task);
-    incoming->state->timeout_task = GNUNET_SCHEDULER_NO_TASK;
-  }
-  GNUNET_assert (NULL != incoming->state);
-  GNUNET_free (incoming->state);
-  // make sure that the tunnel end handler will not
-  // destroy us again
-  incoming->vt = NULL;
-  incoming->state = NULL;
+  struct ElementEntry *ee = value;
+
+  GNUNET_free_non_null (ee->mutations);
+  GNUNET_free (ee);
+  return GNUNET_YES;
 }
 
 
 /**
- * remove & free state of the operation from the incoming list
+ * Clean up after a client has disconnected
  *
- * @param incoming the element to remove
+ * @param cls closure, unused
+ * @param client the client to clean up after
+ * @param internal_cls the `struct ClientState`
  */
 static void
-incoming_retire (struct Operation *incoming)
+client_disconnect_cb (void *cls,
+                      struct GNUNET_SERVICE_Client *client,
+                      void *internal_cls)
 {
-  GNUNET_assert (GNUNET_YES == incoming->is_incoming);
-  incoming->is_incoming = GNUNET_NO;
-  GNUNET_assert (NULL != incoming->state);
-  GNUNET_free (incoming->state);
-  incoming->state = NULL;
-  GNUNET_CONTAINER_DLL_remove (incoming_head, incoming_tail, incoming);
-}
+  struct ClientState *cs = internal_cls;
+  struct Operation *op;
+  struct Listener *listener;
+  struct Set *set;
 
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Client disconnected, cleaning up\n");
+  if (NULL != (set = cs->set))
+  {
+    struct SetContent *content = set->content;
+    struct PendingMutation *pm;
+    struct PendingMutation *pm_current;
+    struct LazyCopyRequest *lcr;
 
-/**
- * Find a listener that is interested in the given operation type
- * and application id.
- *
- * @param op operation type to look for
- * @param app_id application id to look for
- * @return a matching listener, or NULL if no listener matches the
- *         given operation and application id
- */
-static struct Listener *
-listener_get_by_target (enum GNUNET_SET_OperationType op,
-                        const struct GNUNET_HashCode *app_id)
-{
-  struct Listener *l;
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Destroying client's set\n");
+    /* Destroy pending set operations */
+    while (NULL != set->ops_head)
+      _GSS_operation_destroy (set->ops_head,
+                              GNUNET_NO);
+
+    /* Destroy operation-specific state */
+    GNUNET_assert (NULL != set->state);
+    set->vt->destroy_set (set->state);
+    set->state = NULL;
+
+    /* Clean up ongoing iterations */
+    if (NULL != set->iter)
+    {
+      GNUNET_CONTAINER_multihashmap_iterator_destroy (set->iter);
+      set->iter = NULL;
+      set->iteration_id++;
+    }
 
-  for (l = listeners_head; NULL != l; l = l->next)
-  {
-    if (l->operation != op)
-      continue;
-    if (0 != GNUNET_CRYPTO_hash_cmp (app_id, &l->app_id))
-      continue;
-    return l;
-  }
-  return NULL;
-}
+    /* discard any pending mutations that reference this set */
+    pm = content->pending_mutations_head;
+    while (NULL != pm)
+    {
+      pm_current = pm;
+      pm = pm->next;
+      if (pm_current->set == set)
+      {
+        GNUNET_CONTAINER_DLL_remove (content->pending_mutations_head,
+                                     content->pending_mutations_tail,
+                                     pm_current);
+        GNUNET_free (pm_current);
+      }
+    }
 
+    /* free set content (or at least decrement RC) */
+    set->content = NULL;
+    GNUNET_assert (0 != content->refcount);
+    content->refcount--;
+    if (0 == content->refcount)
+    {
+      GNUNET_assert (NULL != content->elements);
+      GNUNET_CONTAINER_multihashmap_iterate (content->elements,
+                                             &destroy_elements_iterator,
+                                             NULL);
+      GNUNET_CONTAINER_multihashmap_destroy (content->elements);
+      content->elements = NULL;
+      GNUNET_free (content);
+    }
+    GNUNET_free_non_null (set->excluded_generations);
+    set->excluded_generations = NULL;
 
-/**
- * Suggest the given request to the listener. The listening client can then
- * accept or reject the remote request.
- *
- * @param incoming the incoming peer with the request to suggest
- * @param listener the listener to suggest the request to
- */
-static void
-incoming_suggest (struct Operation *incoming, struct Listener *listener)
-{
-  struct GNUNET_MQ_Envelope *mqm;
-  struct GNUNET_SET_RequestMessage *cmsg;
+    /* remove set from pending copy requests */
+    lcr = lazy_copy_head;
+    while (NULL != lcr)
+    {
+      struct LazyCopyRequest *lcr_current = lcr;
+
+      lcr = lcr->next;
+      if (lcr_current->source_set == set)
+      {
+        GNUNET_CONTAINER_DLL_remove (lazy_copy_head,
+                                     lazy_copy_tail,
+                                     lcr_current);
+        GNUNET_free (lcr_current);
+      }
+    }
+    GNUNET_free (set);
+  }
 
-  GNUNET_assert (GNUNET_YES == incoming->is_incoming);
-  GNUNET_assert (NULL != incoming->state);
-  GNUNET_assert (NULL != incoming->spec);
-  GNUNET_assert (0 == incoming->state->suggest_id);
-  incoming->state->suggest_id = suggest_id++;
-
-  GNUNET_assert (GNUNET_SCHEDULER_NO_TASK != incoming->state->timeout_task);
-  GNUNET_SCHEDULER_cancel (incoming->state->timeout_task);
-  incoming->state->timeout_task = GNUNET_SCHEDULER_NO_TASK;
-
-  mqm = GNUNET_MQ_msg_nested_mh (cmsg, GNUNET_MESSAGE_TYPE_SET_REQUEST,
-                                 incoming->spec->context_msg);
-  GNUNET_assert (NULL != mqm);
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "suggesting request with accept id %u\n",
-              incoming->state->suggest_id);
-  cmsg->accept_id = htonl (incoming->state->suggest_id);
-  cmsg->peer_id = incoming->spec->peer;
-  GNUNET_MQ_send (listener->client_mq, mqm);
+  if (NULL != (listener = cs->listener))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Destroying client's listener\n");
+    GNUNET_CADET_close_port (listener->open_port);
+    listener->open_port = NULL;
+    while (NULL != (op = listener->op_head))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                  "Destroying incoming operation `%u' from peer `%s'\n",
+                  (unsigned int) op->client_request_id,
+                  GNUNET_i2s (&op->peer));
+      incoming_destroy (op);
+    }
+    GNUNET_CONTAINER_DLL_remove (listener_head,
+                                 listener_tail,
+                                 listener);
+    GNUNET_free (listener);
+  }
+  GNUNET_free (cs);
+  num_clients--;
+  if ( (GNUNET_YES == in_shutdown) &&
+       (0 == num_clients) )
+  {
+    if (NULL != cadet)
+    {
+      GNUNET_CADET_disconnect (cadet);
+      cadet = NULL;
+    }
+  }
 }
 
 
 /**
- * Handle a request for a set operation from
- * another peer.
- *
- * This msg is expected as the first and only msg handled through the
- * non-operation bound virtual table, acceptance of this operation replaces
- * our virtual table and subsequent msgs would be routed differently.
+ * Check a request for a set operation from another peer.
  *
- * @param op the operation state
- * @param mh the received message
+ * @param cls the operation state
+ * @param msg the received message
  * @return #GNUNET_OK if the channel should be kept alive,
  *         #GNUNET_SYSERR to destroy the channel
  */
 static int
-handle_incoming_msg (struct Operation *op,
-                     const struct GNUNET_MessageHeader *mh)
+check_incoming_msg (void *cls,
+                    const struct OperationRequestMessage *msg)
 {
-  const struct OperationRequestMessage *msg = (const struct OperationRequestMessage *) mh;
-  struct Listener *listener;
-  struct OperationSpecification *spec;
-
-  GNUNET_assert (GNUNET_YES == op->is_incoming);
+  struct Operation *op = cls;
+  struct Listener *listener = op->listener;
+  const struct GNUNET_MessageHeader *nested_context;
 
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "got op request\n");
-
-  if (GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST != ntohs (mh->type))
+  /* double operation request */
+  if (0 != op->suggest_id)
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-
-  /* double operation request */
-  if (NULL != op->spec)
+  /* This should be equivalent to the previous condition, but can't hurt to check twice */
+  if (NULL == op->listener)
   {
-    GNUNET_break_op (0);
+    GNUNET_break (0);
     return GNUNET_SYSERR;
   }
-
-  spec = GNUNET_new (struct OperationSpecification);
-  spec->context_msg = GNUNET_MQ_extract_nested_mh (msg);
-  // for simplicity we just backup the context msg instead of rebuilding it later on
-  if (NULL != spec->context_msg)
-    spec->context_msg = GNUNET_copy_message (spec->context_msg);
-  spec->operation = ntohl (msg->operation);
-  spec->app_id = msg->app_id;
-  spec->salt = ntohl (msg->salt);
-  spec->peer = op->state->peer;
-  spec->remote_element_count = ntohl (msg->element_count);
-
-  op->spec = spec;
-
-  if ( (NULL != spec->context_msg) &&
-       (ntohs (spec->context_msg->size) > GNUNET_SET_CONTEXT_MESSAGE_MAX_SIZE) )
+  if (listener->operation != (enum GNUNET_SET_OperationType) ntohl (msg->operation))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "received P2P operation request (op %u, app %s)\n",
-              ntohl (msg->operation), GNUNET_h2s (&msg->app_id));
-  listener = listener_get_by_target (ntohl (msg->operation), &msg->app_id);
-  if (NULL == listener)
+  nested_context = GNUNET_MQ_extract_nested_mh (msg);
+  if ( (NULL != nested_context) &&
+       (ntohs (nested_context->size) > GNUNET_SET_CONTEXT_MESSAGE_MAX_SIZE) )
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "no listener matches incoming request, waiting with timeout\n");
-    return GNUNET_OK;
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  incoming_suggest (op, listener);
   return GNUNET_OK;
 }
 
 
 /**
- * Send the next element of a set to the set's client.  The next element is given by
- * the set's current hashmap iterator.  The set's iterator will be set to NULL if there
- * are no more elements in the set.  The caller must ensure that the set's iterator is
- * valid.
+ * Handle a request for a set operation from another peer.  Checks if we
+ * have a listener waiting for such a request (and in that case initiates
+ * asking the listener about accepting the connection). If no listener
+ * is waiting, we queue the operation request in hope that a listener
+ * shows up soon (before timeout).
  *
- * @param set set that should send its next element to its client
+ * This msg is expected as the first and only msg handled through the
+ * non-operation bound virtual table, acceptance of this operation replaces
+ * our virtual table and subsequent msgs would be routed differently (as
+ * we then know what type of operation this is).
+ *
+ * @param cls the operation state
+ * @param msg the received message
+ * @return #GNUNET_OK if the channel should be kept alive,
+ *         #GNUNET_SYSERR to destroy the channel
  */
 static void
-send_client_element (struct Set *set)
+handle_incoming_msg (void *cls,
+                     const struct OperationRequestMessage *msg)
 {
-  int ret;
-  struct ElementEntry *ee;
-  struct GNUNET_MQ_Envelope *ev;
-
-  GNUNET_assert (NULL != set->iter);
-  ret = GNUNET_CONTAINER_multihashmap_iterator_next (set->iter, NULL, (const void **) &ee);
-  if (GNUNET_NO == ret)
-  {
-    ev = GNUNET_MQ_msg_header (GNUNET_MESSAGE_TYPE_SET_ITER_DONE);
-    GNUNET_CONTAINER_multihashmap_iterator_destroy (set->iter);
-    set->iter = NULL;
-  }
-  else
-  {
-    struct GNUNET_SET_IterResponseMessage *msg;
+  struct Operation *op = cls;
+  struct Listener *listener = op->listener;
+  const struct GNUNET_MessageHeader *nested_context;
+  struct GNUNET_MQ_Envelope *env;
+  struct GNUNET_SET_RequestMessage *cmsg;
 
-    GNUNET_assert (NULL != ee);
-    ev = GNUNET_MQ_msg_extra (msg, ee->element.size, GNUNET_MESSAGE_TYPE_SET_ITER_ELEMENT);
-    memcpy (&msg[1], ee->element.data, ee->element.size);
-    msg->element_type = ee->element.type;
-  }
-  GNUNET_MQ_send (set->client_mq, ev);
+  nested_context = GNUNET_MQ_extract_nested_mh (msg);
+  /* Make a copy of the nested_context (application-specific context
+     information that is opaque to set) so we can pass it to the
+     listener later on */
+  if (NULL != nested_context)
+    op->context_msg = GNUNET_copy_message (nested_context);
+  op->remote_element_count = ntohl (msg->element_count);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received P2P operation request (op %u, port %s) for active listener\n",
+              (uint32_t) ntohl (msg->operation),
+              GNUNET_h2s (&op->listener->app_id));
+  GNUNET_assert (0 == op->suggest_id);
+  if (0 == suggest_id)
+    suggest_id++;
+  op->suggest_id = suggest_id++;
+  GNUNET_assert (NULL != op->timeout_task);
+  GNUNET_SCHEDULER_cancel (op->timeout_task);
+  op->timeout_task = NULL;
+  env = GNUNET_MQ_msg_nested_mh (cmsg,
+                                 GNUNET_MESSAGE_TYPE_SET_REQUEST,
+                                 op->context_msg);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Suggesting incoming request with accept id %u to listener %p of client %p\n",
+              op->suggest_id,
+              listener,
+              listener->cs);
+  cmsg->accept_id = htonl (op->suggest_id);
+  cmsg->peer_id = op->peer;
+  GNUNET_MQ_send (listener->cs->mq,
+                  env);
+  /* NOTE: GNUNET_CADET_receive_done() will be called in
+     #handle_client_accept() */
+}
+
+
+/**
+ * Add an element to @a set as specified by @a msg
+ *
+ * @param set set to manipulate
+ * @param msg message specifying the change
+ */
+static void
+execute_add (struct Set *set,
+             const struct GNUNET_SET_ElementMessage *msg)
+{
+  struct GNUNET_SET_Element el;
+  struct ElementEntry *ee;
+  struct GNUNET_HashCode hash;
+
+  GNUNET_assert (GNUNET_MESSAGE_TYPE_SET_ADD == ntohs (msg->header.type));
+  el.size = ntohs (msg->header.size) - sizeof (*msg);
+  el.data = &msg[1];
+  el.element_type = ntohs (msg->element_type);
+  GNUNET_SET_element_hash (&el,
+                           &hash);
+  ee = GNUNET_CONTAINER_multihashmap_get (set->content->elements,
+                                          &hash);
+  if (NULL == ee)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client inserts element %s of size %u\n",
+                GNUNET_h2s (&hash),
+                el.size);
+    ee = GNUNET_malloc (el.size + sizeof (*ee));
+    ee->element.size = el.size;
+    GNUNET_memcpy (&ee[1],
+            el.data,
+            el.size);
+    ee->element.data = &ee[1];
+    ee->element.element_type = el.element_type;
+    ee->remote = GNUNET_NO;
+    ee->mutations = NULL;
+    ee->mutations_size = 0;
+    ee->element_hash = hash;
+    GNUNET_break (GNUNET_YES ==
+                  GNUNET_CONTAINER_multihashmap_put (set->content->elements,
+                                                     &ee->element_hash,
+                                                     ee,
+                                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  }
+  else if (GNUNET_YES ==
+           is_element_of_generation (ee,
+                                     set->current_generation,
+                                     set->excluded_generations,
+                                     set->excluded_generations_size))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client inserted element %s of size %u twice (ignored)\n",
+                GNUNET_h2s (&hash),
+                el.size);
+
+    /* same element inserted twice */
+    return;
+  }
+
+  {
+    struct MutationEvent mut = {
+      .generation = set->current_generation,
+      .added = GNUNET_YES
+    };
+    GNUNET_array_append (ee->mutations,
+                         ee->mutations_size,
+                         mut);
+  }
+  set->vt->add (set->state,
+                ee);
+}
+
+
+/**
+ * Remove an element from @a set as specified by @a msg
+ *
+ * @param set set to manipulate
+ * @param msg message specifying the change
+ */
+static void
+execute_remove (struct Set *set,
+                const struct GNUNET_SET_ElementMessage *msg)
+{
+  struct GNUNET_SET_Element el;
+  struct ElementEntry *ee;
+  struct GNUNET_HashCode hash;
+
+  GNUNET_assert (GNUNET_MESSAGE_TYPE_SET_REMOVE == ntohs (msg->header.type));
+  el.size = ntohs (msg->header.size) - sizeof (*msg);
+  el.data = &msg[1];
+  el.element_type = ntohs (msg->element_type);
+  GNUNET_SET_element_hash (&el, &hash);
+  ee = GNUNET_CONTAINER_multihashmap_get (set->content->elements,
+                                          &hash);
+  if (NULL == ee)
+  {
+    /* Client tried to remove non-existing element. */
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client removes non-existing element of size %u\n",
+                el.size);
+    return;
+  }
+  if (GNUNET_NO ==
+      is_element_of_generation (ee,
+                                set->current_generation,
+                                set->excluded_generations,
+                                set->excluded_generations_size))
+  {
+    /* Client tried to remove element twice */
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client removed element of size %u twice (ignored)\n",
+                el.size);
+    return;
+  }
+  else
+  {
+    struct MutationEvent mut = {
+      .generation = set->current_generation,
+      .added = GNUNET_NO
+    };
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client removes element of size %u\n",
+                el.size);
+
+    GNUNET_array_append (ee->mutations,
+                         ee->mutations_size,
+                         mut);
+  }
+  set->vt->remove (set->state,
+                   ee);
+}
+
+
+/**
+ * Perform a mutation on a set as specified by the @a msg
+ *
+ * @param set the set to mutate
+ * @param msg specification of what to change
+ */
+static void
+execute_mutation (struct Set *set,
+                  const struct GNUNET_SET_ElementMessage *msg)
+{
+  switch (ntohs (msg->header.type))
+  {
+    case GNUNET_MESSAGE_TYPE_SET_ADD:
+      execute_add (set, msg);
+      break;
+    case GNUNET_MESSAGE_TYPE_SET_REMOVE:
+      execute_remove (set, msg);
+      break;
+    default:
+      GNUNET_break (0);
+  }
+}
+
+
+/**
+ * Execute mutations that were delayed on a set because of
+ * pending operations.
+ *
+ * @param set the set to execute mutations on
+ */
+static void
+execute_delayed_mutations (struct Set *set)
+{
+  struct PendingMutation *pm;
+
+  if (0 != set->content->iterator_count)
+    return; /* still cannot do this */
+  while (NULL != (pm = set->content->pending_mutations_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (set->content->pending_mutations_head,
+                                 set->content->pending_mutations_tail,
+                                 pm);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Executing pending mutation on %p.\n",
+                pm->set);
+    execute_mutation (pm->set,
+                      pm->msg);
+    GNUNET_free (pm->msg);
+    GNUNET_free (pm);
+  }
+}
+
+
+/**
+ * Send the next element of a set to the set's client.  The next element is given by
+ * the set's current hashmap iterator.  The set's iterator will be set to NULL if there
+ * are no more elements in the set.  The caller must ensure that the set's iterator is
+ * valid.
+ *
+ * The client will acknowledge each received element with a
+ * #GNUNET_MESSAGE_TYPE_SET_ITER_ACK message.  Our
+ * #handle_client_iter_ack() will then trigger the next transmission.
+ * Note that the #GNUNET_MESSAGE_TYPE_SET_ITER_DONE is not acknowledged.
+ *
+ * @param set set that should send its next element to its client
+ */
+static void
+send_client_element (struct Set *set)
+{
+  int ret;
+  struct ElementEntry *ee;
+  struct GNUNET_MQ_Envelope *ev;
+  struct GNUNET_SET_IterResponseMessage *msg;
+
+  GNUNET_assert (NULL != set->iter);
+  do {
+    ret = GNUNET_CONTAINER_multihashmap_iterator_next (set->iter,
+                                                       NULL,
+                                                       (const void **) &ee);
+    if (GNUNET_NO == ret)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Iteration on %p done.\n",
+                  set);
+      ev = GNUNET_MQ_msg_header (GNUNET_MESSAGE_TYPE_SET_ITER_DONE);
+      GNUNET_CONTAINER_multihashmap_iterator_destroy (set->iter);
+      set->iter = NULL;
+      set->iteration_id++;
+      GNUNET_assert (set->content->iterator_count > 0);
+      set->content->iterator_count--;
+      execute_delayed_mutations (set);
+      GNUNET_MQ_send (set->cs->mq,
+                      ev);
+      return;
+    }
+    GNUNET_assert (NULL != ee);
+  } while (GNUNET_NO ==
+           is_element_of_generation (ee,
+                                     set->iter_generation,
+                                     set->excluded_generations,
+                                     set->excluded_generations_size));
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Sending iteration element on %p.\n",
+              set);
+  ev = GNUNET_MQ_msg_extra (msg,
+                            ee->element.size,
+                            GNUNET_MESSAGE_TYPE_SET_ITER_ELEMENT);
+  GNUNET_memcpy (&msg[1],
+                 ee->element.data,
+                 ee->element.size);
+  msg->element_type = htons (ee->element.element_type);
+  msg->iteration_id = htons (set->iteration_id);
+  GNUNET_MQ_send (set->cs->mq,
+                  ev);
 }
 
 
 /**
  * Called when a client wants to iterate the elements of a set.
+ * Checks if we have a set associated with the client and if we
+ * can right now start an iteration. If all checks out, starts
+ * sending the elements of the set to the client.
  *
- * @param cls unused
- * @param client client that sent the message
+ * @param cls client that sent the message
  * @param m message sent by the client
  */
 static void
 handle_client_iterate (void *cls,
-                       struct GNUNET_SERVER_Client *client,
                        const struct GNUNET_MessageHeader *m)
 {
+  struct ClientState *cs = cls;
   struct Set *set;
 
-  // iterate over a non existing set
-  set = set_get (client);
-  if (NULL == set)
+  if (NULL == (set = cs->set))
   {
+    /* attempt to iterate over a non existing set */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
-  // only one concurrent iterate-action per set
   if (NULL != set->iter)
   {
+    /* Only one concurrent iterate-action allowed per set */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "iterating union set with %u elements\n",
-              GNUNET_CONTAINER_multihashmap_size (set->elements));
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
-  set->iter = GNUNET_CONTAINER_multihashmap_iterator_create (set->elements);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Iterating set %p in gen %u with %u content elements\n",
+              (void *) set,
+              set->current_generation,
+              GNUNET_CONTAINER_multihashmap_size (set->content->elements));
+  GNUNET_SERVICE_client_continue (cs->client);
+  set->content->iterator_count++;
+  set->iter = GNUNET_CONTAINER_multihashmap_iterator_create (set->content->elements);
+  set->iter_generation = set->current_generation;
   send_client_element (set);
 }
 
 
 /**
- * Called when a client wants to create a new set.
+ * Called when a client wants to create a new set.  This is typically
+ * the first request from a client, and includes the type of set
+ * operation to be performed.
  *
- * @param cls unused
- * @param client client that sent the message
+ * @param cls client that sent the message
  * @param m message sent by the client
  */
 static void
 handle_client_create_set (void *cls,
-                          struct GNUNET_SERVER_Client *client,
-                          const struct GNUNET_MessageHeader *m)
+                          const struct GNUNET_SET_CreateMessage *msg)
 {
-  const struct GNUNET_SET_CreateMessage *msg;
+  struct ClientState *cs = cls;
   struct Set *set;
 
-  msg = (const struct GNUNET_SET_CreateMessage *) m;
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "client created new set (operation %u)\n",
-              ntohs (msg->operation));
-
-  // max. one set per client!
-  if (NULL != set_get (client))
+              "Client created new set (operation %u)\n",
+              (uint32_t) ntohl (msg->operation));
+  if (NULL != cs->set)
   {
+    /* There can only be one set per client */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
   set = GNUNET_new (struct Set);
-
-  switch (ntohs (msg->operation))
+  switch (ntohl (msg->operation))
   {
   case GNUNET_SET_OPERATION_INTERSECTION:
-    // FIXME: implement intersection vt
-    // set->vt = _GSS_intersection_vt ();
+    set->vt = _GSS_intersection_vt ();
     break;
   case GNUNET_SET_OPERATION_UNION:
     set->vt = _GSS_union_vt ();
@@ -727,84 +1087,260 @@ handle_client_create_set (void *cls,
   default:
     GNUNET_free (set);
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
+  set->operation = (enum GNUNET_SET_OperationType) ntohl (msg->operation);
   set->state = set->vt->create ();
-  set->elements = GNUNET_CONTAINER_multihashmap_create (1, GNUNET_YES);
-  set->client = client;
-  set->client_mq = GNUNET_MQ_queue_for_server_client (client);
-  GNUNET_CONTAINER_DLL_insert (sets_head, sets_tail, set);
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  if (NULL == set->state)
+  {
+    /* initialization failed (i.e. out of memory) */
+    GNUNET_free (set);
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
+  }
+  set->content = GNUNET_new (struct SetContent);
+  set->content->refcount = 1;
+  set->content->elements = GNUNET_CONTAINER_multihashmap_create (1,
+                                                                 GNUNET_YES);
+  set->cs = cs;
+  cs->set = set;
+  GNUNET_SERVICE_client_continue (cs->client);
+}
+
+
+/**
+ * Timeout happens iff:
+ *  - we suggested an operation to our listener,
+ *    but did not receive a response in time
+ *  - we got the channel from a peer but no #GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST
+ *
+ * @param cls channel context
+ * @param tc context information (why was this task triggered now)
+ */
+static void
+incoming_timeout_cb (void *cls)
+{
+  struct Operation *op = cls;
+
+  op->timeout_task = NULL;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Remote peer's incoming request timed out\n");
+  incoming_destroy (op);
+}
+
+
+/**
+ * Method called whenever another peer has added us to a channel the
+ * other peer initiated.  Only called (once) upon reception of data
+ * from a channel we listen on.
+ *
+ * The channel context represents the operation itself and gets added
+ * to a DLL, from where it gets looked up when our local listener
+ * client responds to a proposed/suggested operation or connects and
+ * associates with this operation.
+ *
+ * @param cls closure
+ * @param channel new handle to the channel
+ * @param source peer that started the channel
+ * @return initial channel context for the channel
+ *         returns NULL on error
+ */
+static void *
+channel_new_cb (void *cls,
+                struct GNUNET_CADET_Channel *channel,
+                const struct GNUNET_PeerIdentity *source)
+{
+  struct Listener *listener = cls;
+  struct Operation *op;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "New incoming channel\n");
+  op = GNUNET_new (struct Operation);
+  op->listener = listener;
+  op->peer = *source;
+  op->channel = channel;
+  op->mq = GNUNET_CADET_get_mq (op->channel);
+  op->salt = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
+                                       UINT32_MAX);
+  op->timeout_task
+    = GNUNET_SCHEDULER_add_delayed (INCOMING_CHANNEL_TIMEOUT,
+                                    &incoming_timeout_cb,
+                                    op);
+  GNUNET_CONTAINER_DLL_insert (listener->op_head,
+                               listener->op_tail,
+                               op);
+  return op;
+}
+
+
+/**
+ * Function called whenever a channel is destroyed.  Should clean up
+ * any associated state.  It must NOT call
+ * GNUNET_CADET_channel_destroy() on the channel.
+ *
+ * The peer_disconnect function is part of a a virtual table set initially either
+ * when a peer creates a new channel with us, or once we create
+ * a new channel ourselves (evaluate).
+ *
+ * Once we know the exact type of operation (union/intersection), the vt is
+ * replaced with an operation specific instance (_GSS_[op]_vt).
+ *
+ * @param channel_ctx place where local state associated
+ *                   with the channel is stored
+ * @param channel connection to the other end (henceforth invalid)
+ */
+static void
+channel_end_cb (void *channel_ctx,
+                const struct GNUNET_CADET_Channel *channel)
+{
+  struct Operation *op = channel_ctx;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "channel_end_cb called\n");
+  op->channel = NULL;
+  if (NULL != op->listener)
+    incoming_destroy (op);
+  else if (NULL != op->set)
+    op->set->vt->channel_death (op);
+  else
+    _GSS_operation_destroy (op,
+                            GNUNET_YES);
+  GNUNET_free (op);
+}
+
+
+/**
+ * Function called whenever an MQ-channel's transmission window size changes.
+ *
+ * The first callback in an outgoing channel will be with a non-zero value
+ * and will mean the channel is connected to the destination.
+ *
+ * For an incoming channel it will be called immediately after the
+ * #GNUNET_CADET_ConnectEventHandler, also with a non-zero value.
+ *
+ * @param cls Channel closure.
+ * @param channel Connection to the other end (henceforth invalid).
+ * @param window_size New window size. If the is more messages than buffer size
+ *                    this value will be negative..
+ */
+static void
+channel_window_cb (void *cls,
+                   const struct GNUNET_CADET_Channel *channel,
+                   int window_size)
+{
+  /* FIXME: not implemented, we could do flow control here... */
 }
 
 
 /**
  * Called when a client wants to create a new listener.
  *
- * @param cls unused
- * @param client client that sent the message
- * @param m message sent by the client
+ * @param cls client that sent the message
+ * @param msg message sent by the client
  */
 static void
 handle_client_listen (void *cls,
-                      struct GNUNET_SERVER_Client *client,
-                      const struct GNUNET_MessageHeader *m)
+                      const struct GNUNET_SET_ListenMessage *msg)
 {
-  const struct GNUNET_SET_ListenMessage *msg;
+  struct ClientState *cs = cls;
+  struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
+    GNUNET_MQ_hd_var_size (incoming_msg,
+                           GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST,
+                           struct OperationRequestMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_ibf,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_IBF,
+                           struct IBFMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_elements,
+                           GNUNET_MESSAGE_TYPE_SET_P2P_ELEMENTS,
+                           struct GNUNET_SET_ElementMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_offer,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_OFFER,
+                           struct GNUNET_MessageHeader,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_inquiry,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_INQUIRY,
+                           struct InquiryMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_demand,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_DEMAND,
+                           struct GNUNET_MessageHeader,
+                           NULL),
+    GNUNET_MQ_hd_fixed_size (union_p2p_done,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_DONE,
+                             struct GNUNET_MessageHeader,
+                             NULL),
+    GNUNET_MQ_hd_fixed_size (union_p2p_over,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_OVER,
+                             struct GNUNET_MessageHeader,
+                             NULL),
+    GNUNET_MQ_hd_fixed_size (union_p2p_full_done,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_FULL_DONE,
+                             struct GNUNET_MessageHeader,
+                             NULL),
+    GNUNET_MQ_hd_fixed_size (union_p2p_request_full,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_REQUEST_FULL,
+                             struct GNUNET_MessageHeader,
+                             NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_strata_estimator,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_SE,
+                           struct StrataEstimatorMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_strata_estimator,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_SEC,
+                           struct StrataEstimatorMessage,
+                           NULL),
+    GNUNET_MQ_hd_var_size (union_p2p_full_element,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_FULL_ELEMENT,
+                           struct GNUNET_SET_ElementMessage,
+                           NULL),
+    GNUNET_MQ_hd_fixed_size (intersection_p2p_element_info,
+                             GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_ELEMENT_INFO,
+                             struct IntersectionElementInfoMessage,
+                             NULL),
+    GNUNET_MQ_hd_var_size (intersection_p2p_bf,
+                           GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_BF,
+                           struct BFMessage,
+                           NULL),
+    GNUNET_MQ_hd_fixed_size (intersection_p2p_done,
+                             GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_DONE,
+                             struct IntersectionDoneMessage,
+                             NULL),
+    GNUNET_MQ_handler_end ()
+  };
   struct Listener *listener;
-  struct Operation *op;
 
-  msg = (const struct GNUNET_SET_ListenMessage *) m;
-  /* max. one per client! */
-  if (NULL != listener_get (client))
+  if (NULL != cs->listener)
   {
+    /* max. one active listener per client! */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
   listener = GNUNET_new (struct Listener);
-  listener->client = client;
-  listener->client_mq = GNUNET_MQ_queue_for_server_client (client);
+  listener->cs = cs;
+  cs->listener = listener;
   listener->app_id = msg->app_id;
-  listener->operation = ntohl (msg->operation);
-  GNUNET_CONTAINER_DLL_insert_tail (listeners_head, listeners_tail, listener);
+  listener->operation = (enum GNUNET_SET_OperationType) ntohl (msg->operation);
+  GNUNET_CONTAINER_DLL_insert (listener_head,
+                               listener_tail,
+                               listener);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "new listener created (op %u, app %s)\n",
+              "New listener created (op %u, port %s)\n",
               listener->operation,
               GNUNET_h2s (&listener->app_id));
-
-  /* check for incoming requests the listener is interested in */
-  for (op = incoming_head; NULL != op; op = op->next)
-  {
-    if (NULL == op->spec)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "request has no spec yet\n");
-      continue;
-    }
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "considering (op: %u, app: %s, suggest: %u)\n",
-                op->spec->operation,
-                GNUNET_h2s (&op->spec->app_id),
-                op->state->suggest_id);
-
-    /* don't consider the incoming request if it has been already suggested to a listener */
-    if (0 != op->state->suggest_id)
-      continue;
-    if (listener->operation != op->spec->operation)
-      continue;
-    if (0 != GNUNET_CRYPTO_hash_cmp (&listener->app_id, &op->spec->app_id))
-      continue;
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "request suggested\n");
-    incoming_suggest (op, listener);
-  }
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "considered all incoming requests\n");
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+  listener->open_port
+    = GNUNET_CADET_open_port (cadet,
+                              &msg->app_id,
+                              &channel_new_cb,
+                              listener,
+                              &channel_window_cb,
+                              &channel_end_cb,
+                              cadet_handlers);
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
@@ -812,532 +1348,612 @@ handle_client_listen (void *cls,
  * Called when the listening client rejects an operation
  * request by another peer.
  *
- * @param cls unused
- * @param client client that sent the message
- * @param m message sent by the client
+ * @param cls client that sent the message
+ * @param msg message sent by the client
  */
 static void
 handle_client_reject (void *cls,
-                      struct GNUNET_SERVER_Client *client,
-                      const struct GNUNET_MessageHeader *m)
+                      const struct GNUNET_SET_RejectMessage *msg)
 {
-  struct Operation *incoming;
-  const struct GNUNET_SET_AcceptRejectMessage *msg;
-
-  msg = (const struct GNUNET_SET_AcceptRejectMessage *) m;
-  GNUNET_break (0 == ntohl (msg->request_id));
+  struct ClientState *cs = cls;
+  struct Operation *op;
 
-  // no matching incoming operation for this reject
-  incoming = get_incoming (ntohl (msg->accept_reject_id));
-  if (NULL == incoming)
+  op = get_incoming (ntohl (msg->accept_reject_id));
+  if (NULL == op)
   {
-    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    /* no matching incoming operation for this reject;
+       could be that the other peer already disconnected... */
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Client rejected unknown operation %u\n",
+                (unsigned int) ntohl (msg->accept_reject_id));
+    GNUNET_SERVICE_client_continue (cs->client);
     return;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "peer request rejected by client\n");
+              "Peer request (op %u, app %s) rejected by client\n",
+              op->listener->operation,
+              GNUNET_h2s (&cs->listener->app_id));
+  GNUNET_CADET_channel_destroy (op->channel);
+  GNUNET_SERVICE_client_continue (cs->client);
+}
 
-  GNUNET_MESH_channel_destroy (incoming->channel);
-  //channel destruction handler called immediately upon destruction
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+
+/**
+ * Called when a client wants to add or remove an element to a set it inhabits.
+ *
+ * @param cls client that sent the message
+ * @param msg message sent by the client
+ */
+static int
+check_client_mutation (void *cls,
+                       const struct GNUNET_SET_ElementMessage *msg)
+{
+  /* NOTE: Technically, we should probably check with the
+     block library whether the element we are given is well-formed */
+  return GNUNET_OK;
 }
 
 
 /**
- * Called when a client wants to add/remove an element to/from a
- * set it inhabits.
+ * Called when a client wants to add or remove an element to a set it inhabits.
  *
- * @param cls unused
- * @param client client that sent the message
- * @param m message sent by the client
+ * @param cls client that sent the message
+ * @param msg message sent by the client
  */
 static void
-handle_client_add_remove (void *cls,
-                          struct GNUNET_SERVER_Client *client,
-                          const struct GNUNET_MessageHeader *m)
+handle_client_mutation (void *cls,
+                        const struct GNUNET_SET_ElementMessage *msg)
 {
+  struct ClientState *cs = cls;
   struct Set *set;
-  const struct GNUNET_SET_ElementMessage *msg;
-  struct GNUNET_SET_Element el;
-  struct ElementEntry *ee;
 
-  // client without a set requested an operation
-  set = set_get (client);
-  if (NULL == set)
+  if (NULL == (set = cs->set))
   {
+    /* client without a set requested an operation */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
-  msg = (const struct GNUNET_SET_ElementMessage *) m;
-  el.size = ntohs (m->size) - sizeof *msg;
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "client ins/rem element of size %u\n", el.size);
-  el.data = &msg[1];
-  if (GNUNET_MESSAGE_TYPE_SET_REMOVE == ntohs (m->type))
-  {
-    struct GNUNET_HashCode hash;
+  GNUNET_SERVICE_client_continue (cs->client);
 
-    GNUNET_CRYPTO_hash (el.data, el.size, &hash);
-    ee = GNUNET_CONTAINER_multihashmap_get (set->elements, &hash);
-    if (NULL == ee)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                  "client tried to remove non-existing element\n");
-      return;
-    }
-    if (GNUNET_YES == ee->removed)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                  "client tried to remove element twice\n");
-      return;
-    }
-    ee->removed = GNUNET_YES;
-    ee->generation_removed = set->current_generation;
-    set->vt->remove (set->state, ee);
-  }
-  else
+  if (0 != set->content->iterator_count)
   {
-    struct ElementEntry *ee_dup;
+    struct PendingMutation *pm;
 
-    ee = GNUNET_malloc (el.size + sizeof *ee);
-    ee->element.size = el.size;
-    memcpy (&ee[1], el.data, el.size);
-    ee->element.data = &ee[1];
-    ee->generation_added = set->current_generation;
-    ee->remote = GNUNET_NO;
-    GNUNET_CRYPTO_hash (ee->element.data, el.size, &ee->element_hash);
-    ee_dup = GNUNET_CONTAINER_multihashmap_get (set->elements,
-                                                &ee->element_hash);
-    if (NULL != ee_dup)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "element inserted twice, ignoring\n");
-      GNUNET_free (ee);
-      return;
-    }
-    GNUNET_CONTAINER_multihashmap_put (set->elements, &ee->element_hash, ee,
-                                       GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);
-    set->vt->add (set->state, ee);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Scheduling mutation on set\n");
+    pm = GNUNET_new (struct PendingMutation);
+    pm->msg = (struct GNUNET_SET_ElementMessage *) GNUNET_copy_message (&msg->header);
+    pm->set = set;
+    GNUNET_CONTAINER_DLL_insert_tail (set->content->pending_mutations_head,
+                                      set->content->pending_mutations_tail,
+                                      pm);
+    return;
   }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Executing mutation on set\n");
+  execute_mutation (set,
+                    msg);
 }
 
 
 /**
- * Called when a client wants to evaluate a set operation with another peer.
+ * Advance the current generation of a set,
+ * adding exclusion ranges if necessary.
  *
- * @param cls unused
- * @param client client that sent the message
- * @param m message sent by the client
+ * @param set the set where we want to advance the generation
  */
 static void
-handle_client_evaluate (void *cls,
-                        struct GNUNET_SERVER_Client *client,
-                        const struct GNUNET_MessageHeader *m)
+advance_generation (struct Set *set)
 {
-  struct Set *set;
-  const struct GNUNET_SET_EvaluateMessage *msg;
-  struct OperationSpecification *spec;
-  struct Operation *op;
+  struct GenerationRange r;
 
-  set = set_get (client);
-  if (NULL == set)
+  if (set->current_generation == set->content->latest_generation)
   {
-    GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    set->content->latest_generation++;
+    set->current_generation++;
     return;
   }
 
-  msg = (const struct GNUNET_SET_EvaluateMessage *) m;
-  spec = GNUNET_new (struct OperationSpecification);
-  spec->operation = set->operation;
-  spec->app_id = msg->app_id;
-  spec->salt = ntohl (msg->salt);
-  spec->peer = msg->target_peer;
-  spec->set = set;
-  spec->result_mode = ntohs (msg->result_mode);
-  spec->client_request_id = ntohl (msg->request_id);
-  spec->context_msg = GNUNET_MQ_extract_nested_mh (msg);
-
-  // for simplicity we just backup the context msg instead of rebuilding it later on
-  if (NULL != spec->context_msg)
-    spec->context_msg = GNUNET_copy_message (spec->context_msg);
+  GNUNET_assert (set->current_generation < set->content->latest_generation);
 
-  op = GNUNET_new (struct Operation);
-  op->spec = spec;
-  op->generation_created = set->current_generation++;
-  op->vt = set->vt;
-  GNUNET_CONTAINER_DLL_insert (set->ops_head, set->ops_tail, op);
-
-  op->channel = GNUNET_MESH_channel_create (mesh, op, &msg->target_peer,
-                                            GNUNET_APPLICATION_TYPE_SET,
-                                            GNUNET_MESH_OPTION_RELIABLE);
+  r.start = set->current_generation + 1;
+  r.end = set->content->latest_generation + 1;
+  set->content->latest_generation = r.end;
+  set->current_generation = r.end;
+  GNUNET_array_append (set->excluded_generations,
+                       set->excluded_generations_size,
+                       r);
+}
 
-  op->mq = GNUNET_MESH_mq_create (op->channel);
 
-  set->vt->evaluate (op);
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+/**
+ * Called when a client wants to initiate a set operation with another
+ * peer.  Initiates the CADET connection to the listener and sends the
+ * request.
+ *
+ * @param cls client that sent the message
+ * @param msg message sent by the client
+ * @return #GNUNET_OK if the message is well-formed
+ */
+static int
+check_client_evaluate (void *cls,
+                        const struct GNUNET_SET_EvaluateMessage *msg)
+{
+  /* FIXME: suboptimal, even if the context below could be NULL,
+     there are malformed messages this does not check for... */
+  return GNUNET_OK;
 }
 
 
 /**
- * Handle an ack from a client, and send the next element.
+ * Called when a client wants to initiate a set operation with another
+ * peer.  Initiates the CADET connection to the listener and sends the
+ * request.
  *
- * @param cls unused
- * @param client the client
- * @param m the message
+ * @param cls client that sent the message
+ * @param msg message sent by the client
  */
 static void
-handle_client_iter_ack (void *cls,
-                   struct GNUNET_SERVER_Client *client,
-                   const struct GNUNET_MessageHeader *m)
+handle_client_evaluate (void *cls,
+                        const struct GNUNET_SET_EvaluateMessage *msg)
 {
+  struct ClientState *cs = cls;
+  struct Operation *op = GNUNET_new (struct Operation);
+  const struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
+    GNUNET_MQ_hd_var_size (incoming_msg,
+                           GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST,
+                           struct OperationRequestMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_ibf,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_IBF,
+                           struct IBFMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_elements,
+                           GNUNET_MESSAGE_TYPE_SET_P2P_ELEMENTS,
+                           struct GNUNET_SET_ElementMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_offer,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_OFFER,
+                           struct GNUNET_MessageHeader,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_inquiry,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_INQUIRY,
+                           struct InquiryMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_demand,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_DEMAND,
+                           struct GNUNET_MessageHeader,
+                           op),
+    GNUNET_MQ_hd_fixed_size (union_p2p_done,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_DONE,
+                             struct GNUNET_MessageHeader,
+                             op),
+    GNUNET_MQ_hd_fixed_size (union_p2p_over,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_OVER,
+                             struct GNUNET_MessageHeader,
+                             op),
+    GNUNET_MQ_hd_fixed_size (union_p2p_full_done,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_FULL_DONE,
+                             struct GNUNET_MessageHeader,
+                             op),
+    GNUNET_MQ_hd_fixed_size (union_p2p_request_full,
+                             GNUNET_MESSAGE_TYPE_SET_UNION_P2P_REQUEST_FULL,
+                             struct GNUNET_MessageHeader,
+                             op),
+    GNUNET_MQ_hd_var_size (union_p2p_strata_estimator,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_SE,
+                           struct StrataEstimatorMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_strata_estimator,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_SEC,
+                           struct StrataEstimatorMessage,
+                           op),
+    GNUNET_MQ_hd_var_size (union_p2p_full_element,
+                           GNUNET_MESSAGE_TYPE_SET_UNION_P2P_FULL_ELEMENT,
+                           struct GNUNET_SET_ElementMessage,
+                           op),
+    GNUNET_MQ_hd_fixed_size (intersection_p2p_element_info,
+                             GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_ELEMENT_INFO,
+                             struct IntersectionElementInfoMessage,
+                             op),
+    GNUNET_MQ_hd_var_size (intersection_p2p_bf,
+                           GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_BF,
+                           struct BFMessage,
+                           op),
+    GNUNET_MQ_hd_fixed_size (intersection_p2p_done,
+                             GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_DONE,
+                             struct IntersectionDoneMessage,
+                             op),
+    GNUNET_MQ_handler_end ()
+  };
   struct Set *set;
+  const struct GNUNET_MessageHeader *context;
 
-  // client without a set requested an operation
-  set = set_get (client);
-  if (NULL == set)
+  if (NULL == (set = cs->set))
   {
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_free (op);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
-  // client sent an ack, but we were not expecting one
-  if (NULL == set->iter)
+  op->salt = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
+                                       UINT32_MAX);
+  op->peer = msg->target_peer;
+  op->result_mode = ntohl (msg->result_mode);
+  op->client_request_id = ntohl (msg->request_id);
+  op->byzantine = msg->byzantine;
+  op->byzantine_lower_bound = msg->byzantine_lower_bound;
+  op->force_full = msg->force_full;
+  op->force_delta = msg->force_delta;
+  context = GNUNET_MQ_extract_nested_mh (msg);
+
+  /* Advance generation values, so that
+     mutations won't interfer with the running operation. */
+  op->set = set;
+  op->generation_created = set->current_generation;
+  advance_generation (set);
+  GNUNET_CONTAINER_DLL_insert (set->ops_head,
+                               set->ops_tail,
+                               op);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Creating new CADET channel to port %s for set operation type %u\n",
+              GNUNET_h2s (&msg->app_id),
+              set->operation);
+  op->channel = GNUNET_CADET_channel_create (cadet,
+                                             op,
+                                             &msg->target_peer,
+                                             &msg->app_id,
+                                             GNUNET_CADET_OPTION_RELIABLE,
+                                             &channel_window_cb,
+                                             &channel_end_cb,
+                                             cadet_handlers);
+  op->mq = GNUNET_CADET_get_mq (op->channel);
+  op->state = set->vt->evaluate (op,
+                                 context);
+  if (NULL == op->state)
   {
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
-  send_client_element (set);
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
 /**
- * Handle a request from the client to
- * cancel a running set operation.
+ * Handle an ack from a client, and send the next element. Note
+ * that we only expect acks for set elements, not after the
+ * #GNUNET_MESSAGE_TYPE_SET_ITER_DONE message.
  *
- * @param cls unused
- * @param client the client
- * @param mh the message
+ * @param cls client the client
+ * @param ack the message
  */
 static void
-handle_client_cancel (void *cls,
-                      struct GNUNET_SERVER_Client *client,
-                      const struct GNUNET_MessageHeader *mh)
+handle_client_iter_ack (void *cls,
+                        const struct GNUNET_SET_IterAckMessage *ack)
 {
-  const struct GNUNET_SET_CancelMessage *msg =
-      (const struct GNUNET_SET_CancelMessage *) mh;
+  struct ClientState *cs = cls;
   struct Set *set;
-  struct Operation *op;
-  int found;
 
-  // client without a set requested an operation
-  set = set_get (client);
-  if (NULL == set)
+  if (NULL == (set = cs->set))
   {
+    /* client without a set acknowledged receiving a value */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-  found = GNUNET_NO;
-  for (op = set->ops_head; NULL != op; op = op->next)
-  {
-    if (op->spec->client_request_id == msg->request_id)
-    {
-      found = GNUNET_YES;
-      break;
-    }
-  }
-
-  if (GNUNET_NO == found)
+  if (NULL == set->iter)
   {
+    /* client sent an ack, but we were not expecting one (as
+       set iteration has finished) */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
-  _GSS_operation_destroy (op);
+  GNUNET_SERVICE_client_continue (cs->client);
+  if (ntohl (ack->send_more))
+  {
+    send_client_element (set);
+  }
+  else
+  {
+    GNUNET_CONTAINER_multihashmap_iterator_destroy (set->iter);
+    set->iter = NULL;
+    set->iteration_id++;
+  }
 }
 
 
 /**
- * Handle a request from the client to accept
- * a set operation that came from a remote peer.
- * We forward the accept to the associated operation for handling
+ * Handle a request from the client to copy a set.
  *
- * @param cls unused
- * @param client the client
+ * @param cls the client
  * @param mh the message
  */
 static void
-handle_client_accept (void *cls,
-                      struct GNUNET_SERVER_Client *client,
-                      const struct GNUNET_MessageHeader *mh)
+handle_client_copy_lazy_prepare (void *cls,
+                                 const struct GNUNET_MessageHeader *mh)
 {
+  struct ClientState *cs = cls;
   struct Set *set;
-  const struct GNUNET_SET_AcceptRejectMessage *msg;
-  struct Operation *op;
-
-  msg = (const struct GNUNET_SET_AcceptRejectMessage *) mh;
-  op = get_incoming (ntohl (msg->accept_reject_id));
+  struct LazyCopyRequest *cr;
+  struct GNUNET_MQ_Envelope *ev;
+  struct GNUNET_SET_CopyLazyResponseMessage *resp_msg;
 
-  // incoming operation does not exist
-  if (NULL == op)
+  if (NULL == (set = cs->set))
   {
+    /* client without a set requested an operation */
     GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
   }
-
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "client accepting %u\n",
-              ntohl (msg->accept_reject_id));
-
-  GNUNET_assert (GNUNET_YES == op->is_incoming);
-
-  // client without a set requested an operation
-  set = set_get (client);
-
-  if (NULL == set)
-  {
-    GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
-    return;
-  }
-
-  op->spec->set = set;
-
-  incoming_retire (op);
-
-  GNUNET_assert (NULL != op->spec->set);
-  GNUNET_assert (NULL != op->spec->set->vt);
-
-  GNUNET_CONTAINER_DLL_insert (set->ops_head, set->ops_tail, op);
-
-  op->spec->client_request_id = ntohl (msg->request_id);
-  op->spec->result_mode = ntohs (msg->result_mode);
-  op->generation_created = set->current_generation++;
-  op->vt = op->spec->set->vt;
-  GNUNET_assert (NULL != op->vt->accept);
-  set->vt->accept (op);
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+              "Client requested creation of lazy copy\n");
+  cr = GNUNET_new (struct LazyCopyRequest);
+  cr->cookie = ++lazy_copy_cookie;
+  cr->source_set = set;
+  GNUNET_CONTAINER_DLL_insert (lazy_copy_head,
+                               lazy_copy_tail,
+                               cr);
+  ev = GNUNET_MQ_msg (resp_msg,
+                      GNUNET_MESSAGE_TYPE_SET_COPY_LAZY_RESPONSE);
+  resp_msg->cookie = cr->cookie;
+  GNUNET_MQ_send (set->cs->mq,
+                  ev);
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
 /**
- * Called to clean up, after a shutdown has been requested.
+ * Handle a request from the client to connect to a copy of a set.
  *
- * @param cls closure
- * @param tc context information (why was this task triggered now)
+ * @param cls the client
+ * @param msg the message
  */
 static void
-shutdown_task (void *cls,
-               const struct GNUNET_SCHEDULER_TaskContext *tc)
+handle_client_copy_lazy_connect (void *cls,
+                                 const struct GNUNET_SET_CopyLazyConnectMessage *msg)
 {
-  while (NULL != incoming_head)
-    incoming_destroy (incoming_head);
-
-  while (NULL != listeners_head)
-    listener_destroy (listeners_head);
-
-  while (NULL != sets_head)
-    set_destroy (sets_head);
+  struct ClientState *cs = cls;
+  struct LazyCopyRequest *cr;
+  struct Set *set;
+  int found;
 
-  /* it's important to destroy mesh at the end, as all channels
-   * must be destroyed before the mesh handle! */
-  if (NULL != mesh)
+  if (NULL != cs->set)
+  {
+    /* There can only be one set per client */
+    GNUNET_break (0);
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
+  }
+  found = GNUNET_NO;
+  for (cr = lazy_copy_head; NULL != cr; cr = cr->next)
   {
-    GNUNET_MESH_disconnect (mesh);
-    mesh = NULL;
+    if (cr->cookie == msg->cookie)
+    {
+      found = GNUNET_YES;
+      break;
+    }
   }
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "handled shutdown request\n");
-}
-
-
-/**
- * Timeout happens iff:
- *  - we suggested an operation to our listener,
- *    but did not receive a response in time
- *  - we got the channel from a peer but no #GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST
- *  - shutdown (obviously)
- *
- * @param cls channel context
- * @param tc context information (why was this task triggered now)
- */
-static void
-incoming_timeout_cb (void *cls,
-                     const struct GNUNET_SCHEDULER_TaskContext *tc)
-{
-  struct Operation *incoming = cls;
-
-  incoming->state->timeout_task = GNUNET_SCHEDULER_NO_TASK;
-  GNUNET_assert (GNUNET_YES == incoming->is_incoming);
-  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+  if (GNUNET_NO == found)
+  {
+    /* client asked for copy with cookie we don't know */
+    GNUNET_break (0);
+    GNUNET_SERVICE_client_drop (cs->client);
     return;
+  }
+  GNUNET_CONTAINER_DLL_remove (lazy_copy_head,
+                               lazy_copy_tail,
+                               cr);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "remote peer timed out\n");
-  incoming_destroy (incoming);
-}
+              "Client %p requested use of lazy copy\n",
+              cs);
+  set = GNUNET_new (struct Set);
+  switch (cr->source_set->operation)
+  {
+  case GNUNET_SET_OPERATION_INTERSECTION:
+    set->vt = _GSS_intersection_vt ();
+    break;
+  case GNUNET_SET_OPERATION_UNION:
+    set->vt = _GSS_union_vt ();
+    break;
+  default:
+    GNUNET_assert (0);
+    return;
+  }
 
+  if (NULL == set->vt->copy_state)
+  {
+    /* Lazy copy not supported for this set operation */
+    GNUNET_break (0);
+    GNUNET_free (set);
+    GNUNET_free (cr);
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
+  }
 
-/**
- * Terminates an incoming operation in case we have not yet received an
- * operation request. Called by the channel destruction handler.
- *
- * @param op the channel context
- */
-static void
-handle_incoming_disconnect (struct Operation *op)
-{
-  GNUNET_assert (GNUNET_YES == op->is_incoming);
-  incoming_destroy (op);
-  op->vt = NULL;
+  set->operation = cr->source_set->operation;
+  set->state = set->vt->copy_state (cr->source_set->state);
+  set->content = cr->source_set->content;
+  set->content->refcount++;
+
+  set->current_generation = cr->source_set->current_generation;
+  set->excluded_generations_size = cr->source_set->excluded_generations_size;
+  set->excluded_generations
+    = GNUNET_memdup (cr->source_set->excluded_generations,
+                     set->excluded_generations_size * sizeof (struct GenerationRange));
+
+  /* Advance the generation of the new set, so that mutations to the
+     of the cloned set and the source set are independent. */
+  advance_generation (set);
+  set->cs = cs;
+  cs->set = set;
+  GNUNET_free (cr);
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
 /**
- * Method called whenever another peer has added us to a channel
- * the other peer initiated.
- * Only called (once) upon reception of data with a message type which was
- * subscribed to in GNUNET_MESH_connect().
- *
- * The channel context represents the operation itself and gets added to a DLL,
- * from where it gets looked up when our local listener client responds
- * to a proposed/suggested operation or connects and associates with this operation.
+ * Handle a request from the client to cancel a running set operation.
  *
- * @param cls closure
- * @param channel new handle to the channel
- * @param initiator peer that started the channel
- * @param port Port this channel is for.
- * @param options Unused.
- * @return initial channel context for the channel
- *         (can be NULL -- that's not an error)
+ * @param cls the client
+ * @param msg the message
  */
-static void *
-channel_new_cb (void *cls,
-               struct GNUNET_MESH_Channel *channel,
-               const struct GNUNET_PeerIdentity *initiator,
-               uint32_t port, enum GNUNET_MESH_ChannelOption options)
+static void
+handle_client_cancel (void *cls,
+                      const struct GNUNET_SET_CancelMessage *msg)
 {
-  struct Operation *incoming;
-  static const struct SetVT incoming_vt = {
-    .msg_handler = handle_incoming_msg,
-    .peer_disconnect = handle_incoming_disconnect
-  };
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "new incoming channel\n");
+  struct ClientState *cs = cls;
+  struct Set *set;
+  struct Operation *op;
+  int found;
 
-  if (GNUNET_APPLICATION_TYPE_SET != port)
+  if (NULL == (set = cs->set))
   {
+    /* client without a set requested an operation */
     GNUNET_break (0);
-    GNUNET_MESH_channel_destroy (channel);
-    return NULL;
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
   }
-
-  incoming = GNUNET_new (struct Operation);
-  incoming->is_incoming = GNUNET_YES;
-  incoming->state = GNUNET_new (struct OperationState);
-  incoming->state->peer = *initiator;
-  incoming->channel = channel;
-  incoming->mq = GNUNET_MESH_mq_create (incoming->channel);
-  incoming->vt = &incoming_vt;
-  incoming->state->timeout_task =
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_MINUTES,
-                                    &incoming_timeout_cb, incoming);
-  GNUNET_CONTAINER_DLL_insert_tail (incoming_head, incoming_tail, incoming);
-
-  return incoming;
+  found = GNUNET_NO;
+  for (op = set->ops_head; NULL != op; op = op->next)
+  {
+    if (op->client_request_id == ntohl (msg->request_id))
+    {
+      found = GNUNET_YES;
+      break;
+    }
+  }
+  if (GNUNET_NO == found)
+  {
+    /* It may happen that the operation was already destroyed due to
+     * the other peer disconnecting.  The client may not know about this
+     * yet and try to cancel the (just barely non-existent) operation.
+     * So this is not a hard error.
+     */
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Client canceled non-existent op %u\n",
+                (uint32_t) ntohl (msg->request_id));
+  }
+  else
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client requested cancel for op %u\n",
+                (uint32_t) ntohl (msg->request_id));
+    _GSS_operation_destroy (op,
+                            GNUNET_YES);
+  }
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
 /**
- * Function called whenever a channel is destroyed.  Should clean up
- * any associated state.  It must NOT call
- * GNUNET_MESH_channel_destroy() on the channel.
- *
- * The peer_disconnect function is part of a a virtual table set initially either
- * when a peer creates a new channel with us (channel_new_cb), or once we create
- * a new channel ourselves (evaluate).
+ * Handle a request from the client to accept a set operation that
+ * came from a remote peer.  We forward the accept to the associated
+ * operation for handling
  *
- * Once we know the exact type of operation (union/intersection), the vt is
- * replaced with an operation specific instance (_GSS_[op]_vt).
- *
- * @param cls closure (set from GNUNET_MESH_connect())
- * @param channel connection to the other end (henceforth invalid)
- * @param channel_ctx place where local state associated
- *                   with the channel is stored
+ * @param cls the client
+ * @param msg the message
  */
 static void
-channel_end_cb (void *cls,
-                const struct GNUNET_MESH_Channel *channel, void *channel_ctx)
+handle_client_accept (void *cls,
+                      const struct GNUNET_SET_AcceptMessage *msg)
 {
-  struct Operation *op = channel_ctx;
+  struct ClientState *cs = cls;
+  struct Set *set;
+  struct Operation *op;
+  struct GNUNET_SET_ResultMessage *result_message;
+  struct GNUNET_MQ_Envelope *ev;
+  struct Listener *listener;
 
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "channel end cb called\n");
-  op->channel = NULL;
-  /* the vt can be null if a client already requested canceling op. */
-  if (NULL != op->vt)
+  if (NULL == (set = cs->set))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "calling peer disconnect due to channel end\n");
-    op->vt->peer_disconnect (op);
+    /* client without a set requested to accept */
+    GNUNET_break (0);
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
   }
-
-  if (GNUNET_YES == op->keep)
+  op = get_incoming (ntohl (msg->accept_reject_id));
+  if (NULL == op)
+  {
+    /* It is not an error if the set op does not exist -- it may
+     * have been destroyed when the partner peer disconnected. */
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Client %p accepted request %u of listener %p that is no longer active\n",
+                cs,
+                ntohl (msg->accept_reject_id),
+                cs->listener);
+    ev = GNUNET_MQ_msg (result_message,
+                        GNUNET_MESSAGE_TYPE_SET_RESULT);
+    result_message->request_id = msg->request_id;
+    result_message->result_status = htons (GNUNET_SET_STATUS_FAILURE);
+    GNUNET_MQ_send (set->cs->mq,
+                    ev);
+    GNUNET_SERVICE_client_continue (cs->client);
     return;
-
-  /* mesh will never call us with the context again! */
-  GNUNET_free (channel_ctx);
+  }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "channel end cb finished\n");
+              "Client accepting request %u\n",
+              (uint32_t) ntohl (msg->accept_reject_id));
+  listener = op->listener;
+  op->listener = NULL;
+  GNUNET_CONTAINER_DLL_remove (listener->op_head,
+                               listener->op_tail,
+                               op);
+  op->set = set;
+  GNUNET_CONTAINER_DLL_insert (set->ops_head,
+                               set->ops_tail,
+                               op);
+  op->client_request_id = ntohl (msg->request_id);
+  op->result_mode = ntohl (msg->result_mode);
+  op->byzantine = msg->byzantine;
+  op->byzantine_lower_bound = msg->byzantine_lower_bound;
+  op->force_full = msg->force_full;
+  op->force_delta = msg->force_delta;
+
+  /* Advance generation values, so that future mutations do not
+     interfer with the running operation. */
+  op->generation_created = set->current_generation;
+  advance_generation (set);
+  GNUNET_assert (NULL == op->state);
+  op->state = set->vt->accept (op);
+  if (NULL == op->state)
+  {
+    GNUNET_break (0);
+    GNUNET_SERVICE_client_drop (cs->client);
+    return;
+  }
+  /* Now allow CADET to continue, as we did not do this in
+     #handle_incoming_msg (as we wanted to first see if the
+     local client would accept the request). */
+  GNUNET_CADET_receive_done (op->channel);
+  GNUNET_SERVICE_client_continue (cs->client);
 }
 
 
 /**
- * Functions with this signature are called whenever a message is
- * received via a mesh channel.
- *
- * The msg_handler is a virtual table set in initially either when a peer
- * creates a new channel with us (channel_new_cb), or once we create a new channel
- * ourselves (evaluate).
- *
- * Once we know the exact type of operation (union/intersection), the vt is
- * replaced with an operation specific instance (_GSS_[op]_vt).
+ * Called to clean up, after a shutdown has been requested.
  *
- * @param cls Closure (set from GNUNET_MESH_connect()).
- * @param channel Connection to the other end.
- * @param channel_ctx Place to store local state associated with the channel.
- * @param message The actual message.
- * @return #GNUNET_OK to keep the channel open,
- *         #GNUNET_SYSERR to close it (signal serious error).
+ * @param cls closure, NULL
  */
-static int
-dispatch_p2p_message (void *cls,
-                      struct GNUNET_MESH_Channel *channel,
-                      void **channel_ctx,
-                      const struct GNUNET_MessageHeader *message)
+static void
+shutdown_task (void *cls)
 {
-  struct Operation *op = *channel_ctx;
-  int ret;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "dispatching mesh message (type: %u)\n",
-              ntohs (message->type));
-  /* do this before the handler, as the handler might kill the channel */
-  GNUNET_MESH_receive_done (channel);
-  ret = op->vt->msg_handler (op, message);
+  /* Delay actual shutdown to allow service to disconnect clients */
+  in_shutdown = GNUNET_YES;
+  if (0 == num_clients)
+  {
+    if (NULL != cadet)
+    {
+      GNUNET_CADET_disconnect (cadet);
+      cadet = NULL;
+    }
+  }
+  GNUNET_STATISTICS_destroy (_GSS_statistics,
+                             GNUNET_YES);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "handled mesh message (type: %u)\n",
-              ntohs (message->type));
-  return ret;
+              "handled shutdown request\n");
 }
 
 
@@ -1346,79 +1962,91 @@ dispatch_p2p_message (void *cls,
  * method to run service-specific setup code.
  *
  * @param cls closure
- * @param server the initialized server
  * @param cfg configuration to use
+ * @param service the initialized service
  */
 static void
-run (void *cls, struct GNUNET_SERVER_Handle *server,
-     const struct GNUNET_CONFIGURATION_Handle *cfg)
+run (void *cls,
+     const struct GNUNET_CONFIGURATION_Handle *cfg,
+     struct GNUNET_SERVICE_Handle *service)
 {
-  static const struct GNUNET_SERVER_MessageHandler server_handlers[] = {
-    {handle_client_accept, NULL, GNUNET_MESSAGE_TYPE_SET_ACCEPT,
-        sizeof (struct GNUNET_SET_AcceptRejectMessage)},
-    {handle_client_iter_ack, NULL, GNUNET_MESSAGE_TYPE_SET_ITER_ACK, 0},
-    {handle_client_add_remove, NULL, GNUNET_MESSAGE_TYPE_SET_ADD, 0},
-    {handle_client_create_set, NULL, GNUNET_MESSAGE_TYPE_SET_CREATE,
-        sizeof (struct GNUNET_SET_CreateMessage)},
-    {handle_client_iterate, NULL, GNUNET_MESSAGE_TYPE_SET_ITER_REQUEST,
-        sizeof (struct GNUNET_MessageHeader)},
-    {handle_client_evaluate, NULL, GNUNET_MESSAGE_TYPE_SET_EVALUATE, 0},
-    {handle_client_listen, NULL, GNUNET_MESSAGE_TYPE_SET_LISTEN,
-        sizeof (struct GNUNET_SET_ListenMessage)},
-    {handle_client_reject, NULL, GNUNET_MESSAGE_TYPE_SET_REJECT,
-        sizeof (struct GNUNET_SET_AcceptRejectMessage)},
-    {handle_client_add_remove, NULL, GNUNET_MESSAGE_TYPE_SET_REMOVE, 0},
-    {handle_client_cancel, NULL, GNUNET_MESSAGE_TYPE_SET_CANCEL,
-        sizeof (struct GNUNET_SET_CancelMessage)},
-    {NULL, NULL, 0, 0}
-  };
-  static const struct GNUNET_MESH_MessageHandler mesh_handlers[] = {
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_P2P_OPERATION_REQUEST, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_UNION_P2P_IBF, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_P2P_ELEMENTS, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_P2P_DONE, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_P2P_ELEMENT_REQUESTS, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_UNION_P2P_SE, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_ELEMENT_INFO, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_BF, 0},
-    {dispatch_p2p_message, GNUNET_MESSAGE_TYPE_SET_INTERSECTION_P2P_BF_PART, 0},
-    {NULL, 0, 0}
-  };
-  static const uint32_t mesh_ports[] = {GNUNET_APPLICATION_TYPE_SET, 0};
-
-  configuration = cfg;
-  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
-                                &shutdown_task, NULL);
-  GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
-  GNUNET_SERVER_add_handlers (server, server_handlers);
-
-  mesh = GNUNET_MESH_connect (cfg, NULL, channel_new_cb, channel_end_cb,
-                              mesh_handlers, mesh_ports);
-  if (NULL == mesh)
+  /* FIXME: need to modify SERVICE (!) API to allow
+     us to run a shutdown task *after* clients were
+     forcefully disconnected! */
+  GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
+                                 NULL);
+  _GSS_statistics = GNUNET_STATISTICS_create ("set",
+                                              cfg);
+  cadet = GNUNET_CADET_connect (cfg);
+  if (NULL == cadet)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                _("Could not connect to mesh service\n"));
+                _("Could not connect to CADET service\n"));
+    GNUNET_SCHEDULER_shutdown ();
     return;
   }
 }
 
 
 /**
- * The main function for the set service.
- *
- * @param argc number of arguments from the command line
- * @param argv command line arguments
- * @return 0 ok, 1 on error
+ * Define "main" method using service macro.
  */
-int
-main (int argc, char *const *argv)
-{
-  int ret;
+GNUNET_SERVICE_MAIN
+("set",
+ GNUNET_SERVICE_OPTION_NONE,
+ &run,
+ &client_connect_cb,
+ &client_disconnect_cb,
+ NULL,
+ GNUNET_MQ_hd_fixed_size (client_accept,
+                          GNUNET_MESSAGE_TYPE_SET_ACCEPT,
+                          struct GNUNET_SET_AcceptMessage,
+                          NULL),
+ GNUNET_MQ_hd_fixed_size (client_iter_ack,
+                          GNUNET_MESSAGE_TYPE_SET_ITER_ACK,
+                          struct GNUNET_SET_IterAckMessage,
+                          NULL),
+ GNUNET_MQ_hd_var_size (client_mutation,
+                        GNUNET_MESSAGE_TYPE_SET_ADD,
+                        struct GNUNET_SET_ElementMessage,
+                        NULL),
+ GNUNET_MQ_hd_fixed_size (client_create_set,
+                          GNUNET_MESSAGE_TYPE_SET_CREATE,
+                          struct GNUNET_SET_CreateMessage,
+                          NULL),
+ GNUNET_MQ_hd_fixed_size (client_iterate,
+                          GNUNET_MESSAGE_TYPE_SET_ITER_REQUEST,
+                          struct GNUNET_MessageHeader,
+                          NULL),
+ GNUNET_MQ_hd_var_size (client_evaluate,
+                        GNUNET_MESSAGE_TYPE_SET_EVALUATE,
+                        struct GNUNET_SET_EvaluateMessage,
+                        NULL),
+ GNUNET_MQ_hd_fixed_size (client_listen,
+                          GNUNET_MESSAGE_TYPE_SET_LISTEN,
+                          struct GNUNET_SET_ListenMessage,
+                          NULL),
+ GNUNET_MQ_hd_fixed_size (client_reject,
+                          GNUNET_MESSAGE_TYPE_SET_REJECT,
+                          struct GNUNET_SET_RejectMessage,
+                          NULL),
+ GNUNET_MQ_hd_var_size (client_mutation,
+                        GNUNET_MESSAGE_TYPE_SET_REMOVE,
+                        struct GNUNET_SET_ElementMessage,
+                        NULL),
+ GNUNET_MQ_hd_fixed_size (client_cancel,
+                          GNUNET_MESSAGE_TYPE_SET_CANCEL,
+                          struct GNUNET_SET_CancelMessage,
+                          NULL),
+ GNUNET_MQ_hd_fixed_size (client_copy_lazy_prepare,
+                          GNUNET_MESSAGE_TYPE_SET_COPY_LAZY_PREPARE,
+                          struct GNUNET_MessageHeader,
+                          NULL),
+ GNUNET_MQ_hd_fixed_size (client_copy_lazy_connect,
+                          GNUNET_MESSAGE_TYPE_SET_COPY_LAZY_CONNECT,
+                          struct GNUNET_SET_CopyLazyConnectMessage,
+                          NULL),
+ GNUNET_MQ_handler_end ());
 
-  ret = GNUNET_SERVICE_run (argc, argv, "set",
-                            GNUNET_SERVICE_OPTION_NONE, &run, NULL);
-  return (GNUNET_OK == ret) ? 0 : 1;
-}
 
 /* end of gnunet-service-set.c */
-