excluded test cases for SP for now, while it does not fully work yet
[oweals/gnunet.git] / src / scalarproduct / gnunet-service-scalarproduct.c
index 80fe35758ea7496fd12a654b74496a91ed02a39c..3494703333e04d3ea46744dea3f7eee2261a534c 100644 (file)
 #include "gnunet_applications.h"
 #include "gnunet_protocols.h"
 #include "gnunet_scalarproduct_service.h"
-#include "gnunet_scalarproduct.h"
-
+#include "scalarproduct.h"
 
 #define LOG(kind,...) GNUNET_log_from (kind, "scalarproduct", __VA_ARGS__)
 
+///////////////////////////////////////////////////////////////////////////////
+//                     Service Structure Definitions
+///////////////////////////////////////////////////////////////////////////////
+
+/**
+ * state a session can be in
+ */
+enum SessionState
+{
+    CLIENT_REQUEST_RECEIVED,
+    WAITING_FOR_BOBS_CONNECT,
+    CLIENT_RESPONSE_RECEIVED,
+    WAITING_FOR_SERVICE_REQUEST,
+    WAITING_FOR_SERVICE_RESPONSE,
+    SERVICE_REQUEST_RECEIVED,
+    SERVICE_RESPONSE_RECEIVED,
+    FINALIZED
+};
+
+/**
+ * role a peer in a session can assume
+ */
+enum PeerRole
+{
+    ALICE,
+    BOB
+};
+
+
 /**
- * Log an error message at log-level 'level' that indicates
- * a failure of the command 'cmd' with the message given
- * by gcry_strerror(rc).
+ * A scalarproduct session which tracks:
+ * 
+ * a request form the client to our final response.
+ * or
+ * a request from a service to us(service).
  */
-#define LOG_GCRY(level, cmd, rc) do { LOG(level, _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, gcry_strerror(rc)); } while(0)
+struct ServiceSession
+{
+    /**
+     * the role this peer has
+     */
+    enum PeerRole role;
+
+    /**
+     * session information is kept in a DLL
+     */
+    struct ServiceSession *next;
+
+    /**
+     * session information is kept in a DLL
+     */
+    struct ServiceSession *prev;
+
+    /**
+     * (hopefully) unique transaction ID
+     */
+    struct GNUNET_HashCode key;
+
+    /** 
+     * state of the session
+     */
+    enum SessionState state;
+
+    /**
+     * Alice or Bob's peerID
+     */
+    struct GNUNET_PeerIdentity peer;
+
+    /**
+     * the client this request is related to
+     */
+    struct GNUNET_SERVER_Client * client;
+
+    /**
+     * The message to send
+     */
+    struct GNUNET_MessageHeader * msg;
+    
+    /**
+     * how many elements we were supplied with from the client
+     */
+    uint32_t element_count;
+
+    /**
+     * how many elements actually are used after applying the mask
+     */
+    uint32_t used_element_count;
+
+    /**
+     * how many bytes the mask is long. 
+     * just for convenience so we don't have to re-re-re calculate it each time
+     */
+    uint32_t mask_length;
+
+    /**
+     * all the vector elements we received
+     */
+    int32_t * vector;
+
+    /**
+     * mask of which elements to check
+     */
+    unsigned char * mask;
+
+    /**
+     * Public key of the remote service, only used by bob
+     */
+    gcry_sexp_t remote_pubkey;
+
+    /**
+     * E(ai)(Bob) or ai(Alice) after applying the mask
+     */
+    gcry_mpi_t * a;
+
+    /**
+     * The computed scalar 
+     */
+    gcry_mpi_t product;
+
+    /**
+     * My transmit handle for the current message to a alice/bob
+     */
+    struct GNUNET_MESH_TransmitHandle * service_transmit_handle;
+
+    /**
+     * My transmit handle for the current message to the client
+     */
+    struct GNUNET_SERVER_TransmitHandle * client_transmit_handle;
+
+    /**
+     * tunnel-handle associated with our mesh handle
+     */
+    struct GNUNET_MESH_Tunnel * tunnel;
+    
+    GNUNET_SCHEDULER_TaskIdentifier client_notification_task;
+    
+    GNUNET_SCHEDULER_TaskIdentifier service_request_task;
+};
 
 ///////////////////////////////////////////////////////////////////////////////
 //                      Global Variables
@@ -66,7 +197,7 @@ static unsigned char * my_pubkey_external;
 /**
  * Service's own public key represented as string
  */
-static uint16_t my_pubkey_external_length = 0;
+static uint32_t my_pubkey_external_length = 0;
 
 /**
  * Service's own n
@@ -328,7 +459,7 @@ decrypt_element (gcry_mpi_t m, gcry_mpi_t c, gcry_mpi_t mu, gcry_mpi_t lambda, g
  * @return an MPI value containing the calculated sum, never NULL
  */
 static gcry_mpi_t
-compute_square_sum (gcry_mpi_t * vector, uint16_t length)
+compute_square_sum (gcry_mpi_t * vector, uint32_t length)
 {
   gcry_mpi_t elem;
   gcry_mpi_t sum;
@@ -362,30 +493,32 @@ compute_square_sum (gcry_mpi_t * vector, uint16_t length)
 static size_t
 do_send_message (void *cls, size_t size, void *buf)
 {
-  struct MessageObject * info = cls;
-  struct GNUNET_MessageHeader * msg;
+  struct ServiceSession * session = cls;
   size_t written = 0;
 
-  GNUNET_assert (info);
-  msg = info->msg;
-  GNUNET_assert (msg);
   GNUNET_assert (buf);
 
-  if (ntohs (msg->size) == size)
+  if (ntohs (session->msg->size) == size)
     {
-      memcpy (buf, msg, size);
+      memcpy (buf, session->msg, size);
       written = size;
     }
 
-  // reset the transmit handle, if necessary
-  if (info->transmit_handle)
-    *info->transmit_handle = NULL;
-
+  switch (ntohs(session->msg->type)){
+    case GNUNET_MESSAGE_TYPE_SCALARPRODUCT_SERVICE_TO_CLIENT:
+      session->state = FINALIZED;
+      session->client_transmit_handle = NULL;
+      break;
+    default:
+      session->service_transmit_handle = NULL;
+  }
+    
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
              "Sent a message of type %hu.\n", 
-             ntohs (msg->type));
-  GNUNET_free(msg);
-  GNUNET_free(info);
+             ntohs (session->msg->type));
+  GNUNET_free(session->msg);
+  session->msg = NULL;
+  
   return written;
 }
 
@@ -397,7 +530,7 @@ do_send_message (void *cls, size_t size, void *buf)
  * @return the initialized vector, never NULL
  */
 static gcry_mpi_t *
-initialize_mpi_vector (uint16_t length)
+initialize_mpi_vector (uint32_t length)
 {
   uint32_t i;
   gcry_mpi_t * output = GNUNET_malloc (sizeof (gcry_mpi_t) * length);
@@ -444,7 +577,7 @@ permute_vector (gcry_mpi_t * vector,
  * @return an array of MPI values with random values
  */
 static gcry_mpi_t *
-generate_random_vector (uint16_t length)
+generate_random_vector (uint32_t length)
 {
   gcry_mpi_t * random_vector;
   int32_t value;
@@ -480,7 +613,7 @@ generate_random_vector (uint16_t length)
 static struct ServiceSession *
 find_matching_session (struct ServiceSession * tail,
                        const struct GNUNET_HashCode * key,
-                       uint16_t element_count,
+                       uint32_t element_count,
                        enum SessionState * state,
                        const struct GNUNET_PeerIdentity * peerid)
 {
@@ -508,52 +641,31 @@ find_matching_session (struct ServiceSession * tail,
 }
 
 
-static void
-destroy_tunnel (void *cls,
-                const struct GNUNET_SCHEDULER_TaskContext *tc)
-{
-  struct ServiceSession * session = cls;
-
-  if (session->tunnel)
-    {
-      GNUNET_MESH_tunnel_destroy (session->tunnel);
-      session->tunnel = NULL;
-    }
-  session->service_transmit_handle = NULL;
-  // we need to set this to NULL so there is no problem with double-cancel later on.
-}
-
-
 static void
 free_session (struct ServiceSession * session)
 {
   unsigned int i;
 
-  if (FINALIZED != session->state)
-    {
-      if (session->a)
-        {
-          for (i = 0; i < session->used_element_count; i++)
-            gcry_mpi_release (session->a[i]);
-
-          GNUNET_free (session->a);
-        }
-      if (session->product)
-        gcry_mpi_release (session->product);
+  if (session->a)
+  {
+    for (i = 0; i < session->used_element_count; i++)
+      gcry_mpi_release (session->a[i]);
 
-      if (session->remote_pubkey)
-        gcry_sexp_release (session->remote_pubkey);
+    GNUNET_free (session->a);
+  }
+  if (session->product)
+    gcry_mpi_release (session->product);
 
-      GNUNET_free_non_null (session->vector);
-    }
+  if (session->remote_pubkey)
+    gcry_sexp_release (session->remote_pubkey);
 
+  GNUNET_free_non_null (session->vector);
   GNUNET_free (session);
 }
 ///////////////////////////////////////////////////////////////////////////////
 //                      Event and Message Handlers
 ///////////////////////////////////////////////////////////////////////////////
 
-
 /**
  * A client disconnected. 
  * 
@@ -566,32 +678,41 @@ free_session (struct ServiceSession * session)
  */
 static void
 handle_client_disconnect (void *cls,
-                          struct GNUNET_SERVER_Client
-                          * client)
+                          struct GNUNET_SERVER_Client *client)
 {
-  struct ServiceSession * elem;
-  struct ServiceSession * next;
-
-  // start from the tail, old stuff will be there...
-  for (elem = from_client_head; NULL != elem; elem = next)
+  struct ServiceSession *session;
+  
+  session = GNUNET_SERVER_client_get_user_context (client, struct ServiceSession);
+  if (NULL == session)
+    return;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             _ ("Client (%p) disconnected from us.\n"), client);
+  GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
+  
+  if (!(session->role == BOB && session->state == FINALIZED))
     {
-      next = elem->next;
-      if (elem->client != client)
-        continue;
-
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, _ ("Client (%p) disconnected from us.\n"), client);
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, elem);
-
-      if (!(elem->role == BOB && elem->state == FINALIZED))
-        {
-          //we MUST terminate any client message underway
-          if (elem->service_transmit_handle && elem->tunnel)
-            GNUNET_MESH_notify_transmit_ready_cancel (elem->service_transmit_handle);
-          if (elem->tunnel && elem->state == WAITING_FOR_RESPONSE_FROM_SERVICE)
-            destroy_tunnel (elem, NULL);
-        }
-      free_session (elem);
+      //we MUST terminate any client message underway
+      if (session->service_transmit_handle && session->tunnel)
+        GNUNET_MESH_notify_transmit_ready_cancel (session->service_transmit_handle);
+      if (session->tunnel && session->state == WAITING_FOR_SERVICE_RESPONSE)
+        GNUNET_MESH_tunnel_destroy (session->tunnel);
+    }
+  if (GNUNET_SCHEDULER_NO_TASK != session->client_notification_task)
+    {
+      GNUNET_SCHEDULER_cancel (session->client_notification_task);
+      session->client_notification_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (GNUNET_SCHEDULER_NO_TASK != session->service_request_task)
+    {
+      GNUNET_SCHEDULER_cancel (session->service_request_task);
+      session->service_request_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (NULL != session->client_transmit_handle)
+    {
+      GNUNET_SERVER_notify_transmit_ready_cancel (session->client_transmit_handle);
+      session->client_transmit_handle = NULL;
     }
+  free_session (session);
 }
 
 
@@ -611,7 +732,8 @@ prepare_client_end_notification (void * cls,
 {
   struct ServiceSession * session = cls;
   struct GNUNET_SCALARPRODUCT_client_response * msg;
-  struct MessageObject * msg_obj;
+  
+  session->client_notification_task = GNUNET_SCHEDULER_NO_TASK;
 
   msg = GNUNET_new (struct GNUNET_SCALARPRODUCT_client_response);
   msg->header.type = htons (GNUNET_MESSAGE_TYPE_SCALARPRODUCT_SERVICE_TO_CLIENT);
@@ -620,10 +742,9 @@ prepare_client_end_notification (void * cls,
   msg->header.size = htons (sizeof (struct GNUNET_SCALARPRODUCT_client_response));
   // 0 size and the first char in the product is 0, which should never be zero if encoding is used.
   msg->product_length = htonl (0);
-
-  msg_obj = GNUNET_new (struct MessageObject);
-  msg_obj->msg = &msg->header;
-  msg_obj->transmit_handle = NULL; // do not reset the transmit handle, please
+  msg->range = 1;
+  
+  session->msg = &msg->header;
 
   //transmit this message to our client
   session->client_transmit_handle =
@@ -631,22 +752,19 @@ prepare_client_end_notification (void * cls,
                                                sizeof (struct GNUNET_SCALARPRODUCT_client_response),
                                                GNUNET_TIME_UNIT_FOREVER_REL,
                                                &do_send_message,
-                                               msg_obj);
-
+                                               session);
 
   // if we could not even queue our request, something is wrong
-  if ( ! session->client_transmit_handle)
+  if ( NULL == session->client_transmit_handle)
     {
-
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Could not send message to client (%p)! This is OK if it was disconnected beforehand already.\n"), session->client);
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Could not send message to client (%p)!\n"), session->client);
       // usually gets freed by do_send_message
-      GNUNET_free (msg_obj);
+      session->msg = NULL;
       GNUNET_free (msg);
     }
   else
     GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Sending session-end notification to client (%p) for session %s\n"), &session->client, GNUNET_h2s (&session->key));
   
-  free_session(session);
 }
 
 
@@ -678,7 +796,7 @@ prepare_service_response (gcry_mpi_t * r,
                           struct ServiceSession * response)
 {
   struct GNUNET_SCALARPRODUCT_service_response * msg;
-  uint16_t msg_length = 0;
+  uint32_t msg_length = 0;
   unsigned char * current = NULL;
   unsigned char * element_exported = NULL;
   size_t element_length = 0;
@@ -692,8 +810,8 @@ prepare_service_response (gcry_mpi_t * r,
 
   msg->header.type = htons (GNUNET_MESSAGE_TYPE_SCALARPRODUCT_BOB_TO_ALICE);
   msg->header.size = htons (msg_length);
-  msg->element_count = htons (request->element_count);
-  msg->used_element_count = htons (request->used_element_count);
+  msg->element_count = htonl (request->element_count);
+  msg->used_element_count = htonl (request->used_element_count);
   memcpy (&msg->key, &request->key, sizeof (struct GNUNET_HashCode));
   current = (unsigned char *) &msg[1];
 
@@ -757,37 +875,28 @@ prepare_service_response (gcry_mpi_t * r,
 
   if (GNUNET_SERVER_MAX_MESSAGE_SIZE >= msg_length)
     {
-      struct MessageObject * msg_obj;
-
-      msg_obj = GNUNET_new (struct MessageObject);
-      msg_obj->msg = (struct GNUNET_MessageHeader *) msg;
-      msg_obj->transmit_handle = (void *) &request->service_transmit_handle; //and reset the transmit handle
+      request->msg = (struct GNUNET_MessageHeader *) msg;
       request->service_transmit_handle =
               GNUNET_MESH_notify_transmit_ready (request->tunnel,
                                                  GNUNET_YES,
                                                  GNUNET_TIME_UNIT_FOREVER_REL,
-                                                 &request->peer, //must be specified, we are a slave/participant/non-owner
                                                  msg_length,
                                                  &do_send_message,
-                                                 msg_obj);
+                                                 request);
       // we don't care if it could be send or not. either way, the session is over for us.
       request->state = FINALIZED;
-      response->state = FINALIZED;
     }
   else
-    {
-      // TODO FEATURE: fallback to fragmentation, in case the message is too long
       GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Message too large, fragmentation is currently not supported!)\n"));
-    }
 
   //disconnect our client
-  if ( ! request->service_transmit_handle)
+  if ( NULL == request->service_transmit_handle)
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _ ("Could not send service-response message via mesh!)\n"));
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, response);
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                    &prepare_client_end_notification,
-                                    response);
+      
+      response->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        response);
       return GNUNET_NO;
     }
   return GNUNET_OK;
@@ -816,7 +925,7 @@ compute_service_response (struct ServiceSession * request,
   int ret = GNUNET_SYSERR;
   unsigned int * p;
   unsigned int * q;
-  uint16_t count;
+  uint32_t count;
   gcry_mpi_t * rand = NULL;
   gcry_mpi_t * r = NULL;
   gcry_mpi_t * r_prime = NULL;
@@ -1018,23 +1127,21 @@ except:
  */
 static void
 prepare_service_request (void *cls,
-                         const struct GNUNET_PeerIdentity * peer,
-                         const struct GNUNET_ATS_Information * atsi)
+                         const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
   struct ServiceSession * session = cls;
   unsigned char * current;
   struct GNUNET_SCALARPRODUCT_service_request * msg;
-  struct MessageObject * msg_obj;
   unsigned int i;
   unsigned int j;
-  uint16_t msg_length;
-  size_t element_length = 0; //gets initialized by gcry_mpi_print, but the compiler doesn't know that
+  uint32_t msg_length;
+  size_t element_length = 0; // initialized by gcry_mpi_print, but the compiler doesn't know that
   gcry_mpi_t a;
   uint32_t value;
+  
+  session->service_request_task = GNUNET_SCHEDULER_NO_TASK;
 
-  GNUNET_assert (NULL != cls);
-  GNUNET_assert (NULL != peer);
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, _ ("Successfully created new tunnel to peer (%s)!\n"), GNUNET_i2s (peer));
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, _ ("Successfully created new tunnel to peer (%s)!\n"), GNUNET_i2s (&session->peer));
 
   msg_length = sizeof (struct GNUNET_SCALARPRODUCT_service_request)
           + session->used_element_count * PAILLIER_ELEMENT_LENGTH
@@ -1046,22 +1153,20 @@ prepare_service_request (void *cls,
       + session->mask_length
       + my_pubkey_external_length)
     {
-      // TODO FEATURE: fallback to fragmentation, in case the message is too long
       GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Message too large, fragmentation is currently not supported!\n"));
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                    &prepare_client_end_notification,
-                                    session);
+      session->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        session);
       return;
     }
+  
   msg = GNUNET_malloc (msg_length);
-
   msg->header.type = htons (GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ALICE_TO_BOB);
   memcpy (&msg->key, &session->key, sizeof (struct GNUNET_HashCode));
-  msg->mask_length = htons (session->mask_length);
-  msg->pk_length = htons (my_pubkey_external_length);
-  msg->used_element_count = htons (session->used_element_count);
-  msg->element_count = htons (session->element_count);
+  msg->mask_length = htonl (session->mask_length);
+  msg->pk_length = htonl (my_pubkey_external_length);
+  msg->used_element_count = htonl (session->used_element_count);
+  msg->element_count = htonl (session->element_count);
   msg->header.size = htons (msg_length);
 
   // fill in the payload
@@ -1113,71 +1218,28 @@ prepare_service_request (void *cls,
     }
   gcry_mpi_release (a);
 
-  msg_obj = GNUNET_new (struct MessageObject);
-  msg_obj->msg = (struct GNUNET_MessageHeader *) msg;
-  msg_obj->transmit_handle = (void *) &session->service_transmit_handle; //and reset the transmit handle
+  session->msg = (struct GNUNET_MessageHeader *) msg;
   GNUNET_log (GNUNET_ERROR_TYPE_INFO, _("Transmitting service request.\n"));
 
   //transmit via mesh messaging
-  session->state = WAITING_FOR_RESPONSE_FROM_SERVICE;
   session->service_transmit_handle = GNUNET_MESH_notify_transmit_ready (session->tunnel, GNUNET_YES,
                                                                         GNUNET_TIME_UNIT_FOREVER_REL,
-                                                                        peer, //multicast to all targets, maybe useful in the future
                                                                         msg_length,
                                                                         &do_send_message,
-                                                                        msg_obj);
+                                                                        session);
   if ( ! session->service_transmit_handle)
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _("Could not send mutlicast message to tunnel!\n"));
-      GNUNET_free (msg_obj);
       GNUNET_free (msg);
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                    &prepare_client_end_notification,
-                                    session);
-    }
-}
-
-
-/**
- * Method called whenever a peer has disconnected from the tunnel.
- * Implementations of this callback must NOT call
- * #GNUNET_MESH_tunnel_destroy immediately, but instead schedule those
- * to run in some other task later.  However, calling 
- * #GNUNET_MESH_notify_transmit_ready_cancel is allowed.
- *
- * @param cls closure
- * @param peer peer identity the tunnel stopped working with
- */
-static void
-tunnel_peer_disconnect_handler (void *cls, const struct GNUNET_PeerIdentity * peer)
-{
-  // as we have only one peer connected in each session, just remove the session and say good bye
-  struct ServiceSession * session = cls;
-  struct ServiceSession * curr;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
-             "Peer (%s) disconnected from our tunnel!\n",
-             GNUNET_i2s (peer));
-
-  if ((session->role == ALICE) && (FINALIZED != session->state) && ( ! do_shutdown))
-    {
-      for (curr = from_client_head; NULL != curr; curr = curr->next)
-        if (curr == session)
-          {
-            GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
-            break;
-          }
-      // FIXME: dangling tasks, code duplication, use-after-free, fun...
-      GNUNET_SCHEDULER_add_now (&destroy_tunnel,
-                                session);
-      // if this happened before we received the answer, we must terminate the session
-      GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
-                               session);
+      session->msg = NULL;
+      session->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        session);
+      return;
     }
+  session->state = WAITING_FOR_SERVICE_RESPONSE;
 }
 
-
 /**
  * Handler for a client request message. 
  * Can either be type A or B
@@ -1195,13 +1257,23 @@ handle_client_request (void *cls,
 {
   const struct GNUNET_SCALARPRODUCT_client_request * msg = (const struct GNUNET_SCALARPRODUCT_client_request *) message;
   struct ServiceSession * session;
-  uint16_t element_count;
-  uint16_t mask_length;
-  uint16_t msg_type;
+  uint32_t element_count;
+  uint32_t mask_length;
+  uint32_t msg_type;
   int32_t * vector;
   uint32_t i;
 
-  GNUNET_assert (message);
+  // only one concurrent session per client connection allowed, simplifies logics a lot...
+  session = GNUNET_SERVER_client_get_user_context (client, struct ServiceSession);
+  if ((NULL != session) && (session->state != FINALIZED)){
+    GNUNET_SERVER_receive_done (client, GNUNET_OK);
+    return;
+  }
+  else if(NULL != session){
+    // old session is already completed, clean it up
+    GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
+    free_session(session);
+  }
 
   //we need at least a peer and one message id to compare
   if (sizeof (struct GNUNET_SCALARPRODUCT_client_request) > ntohs (msg->header.size))
@@ -1213,8 +1285,8 @@ handle_client_request (void *cls,
     }
 
   msg_type = ntohs (msg->header.type);
-  element_count = ntohs (msg->element_count);
-  mask_length = ntohs (msg->mask_length);
+  element_count = ntohl (msg->element_count);
+  mask_length = ntohl (msg->mask_length);
 
   //sanity check: is the message as long as the message_count fields suggests?
   if (( ntohs (msg->header.size) != (sizeof (struct GNUNET_SCALARPRODUCT_client_request) + element_count * sizeof (int32_t) + mask_length))
@@ -1232,12 +1304,16 @@ handle_client_request (void *cls,
                                      element_count,
                                      NULL, NULL))
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Duplicate session information received, cannot create new session with key `%s'\n"), GNUNET_h2s (&msg->key));
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, 
+                 _ ("Duplicate session information received, cannot create new session with key `%s'\n"), 
+                 GNUNET_h2s (&msg->key));
       GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
       return;
     }
 
   session = GNUNET_new (struct ServiceSession);
+  session->service_request_task = GNUNET_SCHEDULER_NO_TASK;
+  session->client_notification_task = GNUNET_SCHEDULER_NO_TASK;
   session->client = client;
   session->element_count = element_count;
   session->mask_length = mask_length;
@@ -1249,7 +1325,9 @@ handle_client_request (void *cls,
 
   if (GNUNET_MESSAGE_TYPE_SCALARPRODUCT_CLIENT_TO_ALICE == msg_type)
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, _ ("Got client-request-session with key %s, preparing tunnel to remote service.\n"), GNUNET_h2s (&session->key));
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
+                 _ ("Got client-request-session with key %s, preparing tunnel to remote service.\n"), 
+                 GNUNET_h2s (&session->key));
 
       session->role = ALICE;
       // fill in the mask
@@ -1267,11 +1345,10 @@ handle_client_request (void *cls,
             session->used_element_count++;
         }
 
-      if ( ! session->used_element_count)
+      if ( 0 == session->used_element_count)
         {
           GNUNET_break_op (0);
           GNUNET_free (session->vector);
-          GNUNET_free (session->a);
           GNUNET_free (session);
           GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
           return;
@@ -1281,47 +1358,54 @@ handle_client_request (void *cls,
         {
           GNUNET_break (0);
           GNUNET_free (session->vector);
-          GNUNET_free (session->a);
           GNUNET_free (session);
           GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
           return;
         }
       // get our peer ID
       memcpy (&session->peer, &msg->peer, sizeof (struct GNUNET_PeerIdentity));
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Creating new tunnel to for session with key %s.\n"), GNUNET_h2s (&session->key));
-      GNUNET_CONTAINER_DLL_insert (from_client_head, from_client_tail, session);
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, 
+                 _ ("Creating new tunnel to for session with key %s.\n"), 
+                 GNUNET_h2s (&session->key));
       session->tunnel = GNUNET_MESH_tunnel_create (my_mesh, session,
-                                                   prepare_service_request,
-                                                   tunnel_peer_disconnect_handler,
-                                                   session);
+                                                   &session->peer,
+                                                   GNUNET_APPLICATION_TYPE_SCALARPRODUCT,
+                                                   GNUNET_NO,
+                                                   GNUNET_YES);
+      //prepare_service_request, tunnel_peer_disconnect_handler,
       if ( ! session->tunnel)
         {
           GNUNET_break (0);
           GNUNET_free (session->vector);
-          GNUNET_free (session->a);
           GNUNET_free (session);
           GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
           return;
         }
-      GNUNET_MESH_peer_request_connect_add (session->tunnel, &session->peer);
-      GNUNET_SERVER_receive_done (client, GNUNET_YES);
-      session->state = WAITING_FOR_BOBS_CONNECT;
+      GNUNET_SERVER_client_set_user_context (client, session);
+      GNUNET_CONTAINER_DLL_insert (from_client_head, from_client_tail, session);
+      
+      session->state = CLIENT_REQUEST_RECEIVED;
+      session->service_request_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_service_request, 
+                                        session);
+      
     }
   else
     {
       struct ServiceSession * requesting_session;
-      enum SessionState needed_state = REQUEST_FROM_SERVICE_RECEIVED;
-
+      enum SessionState needed_state = SERVICE_REQUEST_RECEIVED;
+      
       session->role = BOB;
       session->mask = NULL;
       // copy over the elements
       session->used_element_count = element_count;
       for (i = 0; i < element_count; i++)
         session->vector[i] = ntohl (vector[i]);
-      session->state = MESSAGE_FROM_RESPONDING_CLIENT_RECEIVED;
+      session->state = CLIENT_RESPONSE_RECEIVED;
       
+      GNUNET_SERVER_client_set_user_context (client, session);
       GNUNET_CONTAINER_DLL_insert (from_client_head, from_client_tail, session);
-      GNUNET_SERVER_receive_done (client, GNUNET_YES);
+      
       //check if service queue contains a matching request 
       requesting_session = find_matching_session (from_service_tail,
                                                   &session->key,
@@ -1331,18 +1415,18 @@ handle_client_request (void *cls,
         {
           GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Got client-responder-session with key %s and a matching service-request-session set, processing.\n"), GNUNET_h2s (&session->key));
           if (GNUNET_OK != compute_service_response (requesting_session, session))
-            {
-              GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
-              GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                            &prepare_client_end_notification,
-                                            session);
-            }
+              session->client_notification_task = 
+                      GNUNET_SCHEDULER_add_now (&prepare_client_end_notification, 
+                                                session);
+              
         }
-      else
+      else{
         GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Got client-responder-session with key %s but NO matching service-request-session set, queuing element for later use.\n"), GNUNET_h2s (&session->key));
         // no matching session exists yet, store the response
         // for later processing by handle_service_request()
+      }
     }
+  GNUNET_SERVER_receive_done (client, GNUNET_YES);
 }
 
 
@@ -1357,68 +1441,85 @@ handle_client_request (void *cls,
  *         (can be NULL -- that's not an error)
  */
 static void *
-tunnel_incoming_handler (void *cls, struct GNUNET_MESH_Tunnel *tunnel,
+tunnel_incoming_handler (void *cls, 
+                         struct GNUNET_MESH_Tunnel *tunnel,
                          const struct GNUNET_PeerIdentity *initiator,
-                         const struct GNUNET_ATS_Information *atsi)
+                         uint32_t port)
 {
-
   struct ServiceSession * c = GNUNET_new (struct ServiceSession);
 
-  memcpy (&c->peer, initiator, sizeof (struct GNUNET_PeerIdentity));
+  c->peer = *initiator;
   c->tunnel = tunnel;
   c->role = BOB;
+  c->state = WAITING_FOR_SERVICE_REQUEST;
   return c;
 }
 
 
 /**
- * Function called whenever an inbound tunnel is destroyed.  Should clean up
- * any associated state.
+ * Function called whenever a tunnel is destroyed.  Should clean up
+ * any associated state. 
+ * 
+ * It must NOT call GNUNET_MESH_tunnel_destroy on the tunnel.
  *
- * @param cls closure (set from #GNUNET_MESH_connect)
+ * @param cls closure (set from GNUNET_MESH_connect)
  * @param tunnel connection to the other end (henceforth invalid)
  * @param tunnel_ctx place where local state associated
- *                   with the tunnel is stored (our 'struct TunnelState')
+ *                   with the tunnel is stored
  */
 static void
 tunnel_destruction_handler (void *cls,
                             const struct GNUNET_MESH_Tunnel *tunnel,
                             void *tunnel_ctx)
 {
-  struct ServiceSession * service_session = tunnel_ctx;
+  struct ServiceSession * session = tunnel_ctx;
   struct ServiceSession * client_session;
   struct ServiceSession * curr;
-
-  GNUNET_assert (service_session);
-  if (!memcmp (&service_session->peer, &me, sizeof (struct GNUNET_PeerIdentity)))
-    return;
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, _ ("Tunnel destroyed, terminating session with peer (%s)\n"), GNUNET_i2s (&service_session->peer));
-  // remove the session, unless it has already been dequeued, but somehow still active
-  // this could bug without the IF in case the queue is empty and the service session was the only one know to the service
-  for (curr = from_service_head; NULL != curr; curr = curr->next)
-        if (curr == service_session)
-          {
-            GNUNET_CONTAINER_DLL_remove (from_service_head, from_service_tail, curr);
-            break;
-          }
-  // there is a client waiting for this service session, terminate it, too!
-  // i assume the tupel of key and element count is unique. if it was not the rest of the code would not work either.
-  client_session = find_matching_session (from_client_tail,
-                                          &service_session->key,
-                                          service_session->element_count,
-                                          NULL, NULL);
-  free_session (service_session);
-
-  // the client has to check if it was waiting for a result 
-  // or if it was a responder, no point in adding more statefulness
-  if (client_session && ( ! do_shutdown))
+  
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             _("Peer disconnected, terminating session %s with peer (%s)\n"), 
+             GNUNET_h2s (&session->key), 
+             GNUNET_i2s (&session->peer));
+  if (ALICE == session->role) {
+    // as we have only one peer connected in each session, just remove the session
+
+    if ((SERVICE_RESPONSE_RECEIVED > session->state) && (!do_shutdown))
     {
-      // remove the session, we just found it in the queue, so it must be there
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, client_session);
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                    &prepare_client_end_notification,
-                                    client_session);
+      session->tunnel = NULL;
+      // if this happened before we received the answer, we must terminate the session
+      session->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        session);
+    }
+  }
+  else { //(BOB == session->role) service session
+            
+    // remove the session, unless it has already been dequeued, but somehow still active
+    // this could bug without the IF in case the queue is empty and the service session was the only one know to the service
+    // scenario: disconnect before alice can send her message to bob.
+    for (curr = from_service_head; NULL != curr; curr = curr->next)
+      if (curr == session)
+      {
+        GNUNET_CONTAINER_DLL_remove (from_service_head, from_service_tail, curr);
+        break;
+      }
+    // there is a client waiting for this service session, terminate it, too!
+    // i assume the tupel of key and element count is unique. if it was not the rest of the code would not work either.
+    client_session = find_matching_session (from_client_tail,
+                                            &session->key,
+                                            session->element_count,
+                                            NULL, NULL);
+    free_session (session);
+
+    // the client has to check if it was waiting for a result 
+    // or if it was a responder, no point in adding more statefulness
+    if (client_session && (!do_shutdown))
+    {
+      client_session->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        client_session);
     }
+  }
 }
 
 
@@ -1440,7 +1541,7 @@ static gcry_mpi_t
 compute_scalar_product (struct ServiceSession * session,
                         gcry_mpi_t * r, gcry_mpi_t * r_prime, gcry_mpi_t s, gcry_mpi_t s_prime)
 {
-  uint16_t count;
+  uint32_t count;
   gcry_mpi_t t;
   gcry_mpi_t u;
   gcry_mpi_t utick;
@@ -1527,10 +1628,12 @@ prepare_client_response (void *cls,
   struct GNUNET_SCALARPRODUCT_client_response * msg;
   unsigned char * product_exported = NULL;
   size_t product_length = 0;
-  uint16_t msg_length = 0;
-  struct MessageObject * msg_obj;
-  int8_t range = 0;
+  uint32_t msg_length = 0;
+  int8_t range = -1;
+  gcry_error_t rc;
   int sign;
+  
+  session->client_notification_task = GNUNET_SCHEDULER_NO_TASK;
 
   if (session->product)
     {
@@ -1538,64 +1641,70 @@ prepare_client_response (void *cls,
       
       sign = gcry_mpi_cmp_ui(session->product, 0);
       // libgcrypt can not handle a print of a negative number
+      // if (a->sign) return gcry_error (GPG_ERR_INTERNAL); /* Can't handle it yet. */
       if (0 > sign){
-          range = -1;
           gcry_mpi_sub(value, value, session->product);
       }
       else if(0 < sign){
           range = 1;
           gcry_mpi_add(value, value, session->product);
       }
+      else
+        range = 0;
+      
+      gcry_mpi_release (session->product);
+      session->product = NULL;
       
       // get representation as string
-      // unfortunately libgcrypt is too stupid to implement print-support in
-      // signed GCRYMPI_FMT_STD format, and simply asserts in that case.
-      // here is the associated sourcecode:
-      // if (a->sign) return gcry_error (GPG_ERR_INTERNAL); /* Can't handle it yet. */
-      if (range)
-          GNUNET_assert ( ! gcry_mpi_aprint (GCRYMPI_FMT_USG, // FIXME: just log (& survive!)
+      if (range
+          && (0 != (rc =  gcry_mpi_aprint (GCRYMPI_FMT_USG,
                                              &product_exported,
                                              &product_length,
-                                             session->product));
-      
-      gcry_mpi_release (session->product);
-      session->product = NULL;
+                                             value)))){
+        LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_mpi_scan", rc);
+        product_length = 0;
+        range = -1; // signal error with product-length = 0 and range = -1
+      }
+      gcry_mpi_release (value);
     }
 
   msg_length = sizeof (struct GNUNET_SCALARPRODUCT_client_response) + product_length;
   msg = GNUNET_malloc (msg_length);
-  memcpy (&msg[1], product_exported, product_length);
-  GNUNET_free_non_null (product_exported);
+  memcpy (&msg->key, &session->key, sizeof (struct GNUNET_HashCode));
+  memcpy (&msg->peer, &session->peer, sizeof ( struct GNUNET_PeerIdentity));
+  if (product_exported != NULL){
+    memcpy (&msg[1], product_exported, product_length);
+    GNUNET_free(product_exported);
+  }
   msg->header.type = htons (GNUNET_MESSAGE_TYPE_SCALARPRODUCT_SERVICE_TO_CLIENT);
   msg->header.size = htons (msg_length);
   msg->range = range;
-  memcpy (&msg->key, &session->key, sizeof (struct GNUNET_HashCode));
-  memcpy (&msg->peer, &session->peer, sizeof ( struct GNUNET_PeerIdentity));
   msg->product_length = htonl (product_length);
   
-  msg_obj = GNUNET_new (struct MessageObject);
-  msg_obj->msg = (struct GNUNET_MessageHeader *) msg;
-  msg_obj->transmit_handle = NULL; // don't reset the transmit handle
-
+  session->msg = (struct GNUNET_MessageHeader *) msg;
   //transmit this message to our client
-  session->client_transmit_handle =  // FIXME: use after free possibility during shutdown
+  session->client_transmit_handle = 
           GNUNET_SERVER_notify_transmit_ready (session->client,
                                                msg_length,
                                                GNUNET_TIME_UNIT_FOREVER_REL,
                                                &do_send_message,
-                                               msg_obj);
-  if ( ! session->client_transmit_handle)
+                                               session);
+  if ( NULL == session->client_transmit_handle)
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Could not send message to client (%p)! This probably is OK if the client disconnected before us.\n"), session->client);
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                 _ ("Could not send message to client (%p)!\n"), 
+                 session->client);
       session->client = NULL;
       // callback was not called!
-      GNUNET_free (msg_obj);
       GNUNET_free (msg);
+      session->msg = NULL;
     }
   else
       // gracefully sent message, just terminate session structure
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Sent result to client (%p), this session (%s) has ended!\n"), session->client, GNUNET_h2s (&session->key));
-  free_session (session);
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, 
+                 _ ("Sent result to client (%p), this session (%s) has ended!\n"), 
+                 session->client, 
+                 GNUNET_h2s (&session->key));
 }
 
 
@@ -1615,56 +1724,50 @@ static int
 handle_service_request (void *cls,
                         struct GNUNET_MESH_Tunnel * tunnel,
                         void **tunnel_ctx,
-                        const struct GNUNET_PeerIdentity * sender,
-                        const struct GNUNET_MessageHeader * message,
-                        const struct GNUNET_ATS_Information * atsi)
+                        const struct GNUNET_MessageHeader * message)
 {
   struct ServiceSession * session;
   const struct GNUNET_SCALARPRODUCT_service_request * msg = (const struct GNUNET_SCALARPRODUCT_service_request *) message;
-  uint16_t mask_length;
-  uint16_t pk_length;
-  uint16_t used_elements;
-  uint16_t element_count;
-  uint16_t msg_length;
+  uint32_t mask_length;
+  uint32_t pk_length;
+  uint32_t used_elements;
+  uint32_t element_count;
+  uint32_t msg_length;
   unsigned char * current;
   struct ServiceSession * responder_session;
   int32_t i = -1;
   enum SessionState needed_state;
 
   session = (struct ServiceSession *) * tunnel_ctx;
+  if (BOB != session->role){
+    GNUNET_break_op(0);
+    return GNUNET_SYSERR;
+  }
   // is this tunnel already in use?
   if ( (session->next) || (from_service_head == session))
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Got a service request over a tunnel that is already in use, ignoring!\n"));
+      GNUNET_break_op(0);
       return GNUNET_SYSERR;
     }
   // Check if message was sent by me, which would be bad!
-  if ( ! memcmp (sender, &me, sizeof (struct GNUNET_PeerIdentity)))
+  if ( ! memcmp (&session->peer, &me, sizeof (struct GNUNET_PeerIdentity)))
     {
-      GNUNET_break (0);
       GNUNET_free (session);
-      return GNUNET_SYSERR;
-    }
-  // this protocol can at best be 1:N, but never M:N!
-  // Check if the sender is not the peer, I am connected to, which would be bad!
-  if (memcmp (sender, &session->peer, sizeof (struct GNUNET_PeerIdentity)))
-    {
       GNUNET_break (0);
-      GNUNET_free (session);
       return GNUNET_SYSERR;
     }
 
   //we need at least a peer and one message id to compare
   if (ntohs (msg->header.size) < sizeof (struct GNUNET_SCALARPRODUCT_service_request))
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Too short message received from peer!\n"));
       GNUNET_free (session);
+      GNUNET_break_op(0);
       return GNUNET_SYSERR;
     }
-  mask_length = ntohs (msg->mask_length);
-  pk_length = ntohs (msg->pk_length);
-  used_elements = ntohs (msg->used_element_count);
-  element_count = ntohs (msg->element_count);
+  mask_length = ntohl (msg->mask_length);
+  pk_length = ntohl (msg->pk_length);
+  used_elements = ntohl (msg->used_element_count);
+  element_count = ntohl (msg->element_count);
   msg_length = sizeof (struct GNUNET_SCALARPRODUCT_service_request)
                + mask_length + pk_length + used_elements * PAILLIER_ELEMENT_LENGTH;
 
@@ -1673,25 +1776,24 @@ handle_service_request (void *cls,
       || (used_elements == 0) || (mask_length != (element_count / 8 + (element_count % 8 ? 1 : 0)))
       )
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Invalid message received from peer, message count does not match message length!\n"));
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _ ("Used elements: %hu\nElement Count: %hu\nExpected Mask Length: %hu\nCalculated Masklength: %d\n"), used_elements, element_count, mask_length, (element_count / 8 + (element_count % 8 ? 1 : 0)));
       GNUNET_free (session);
+      GNUNET_break_op(0);
       return GNUNET_SYSERR;
     }
   if (find_matching_session (from_service_tail,
                              &msg->key,
                              element_count,
                              NULL,
-                             sender))
+                             NULL))
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _ ("Got message with duplicate session key (`%s'), ignoring service request.\n"), (const char *) &(msg->key));
       GNUNET_free (session);
       return GNUNET_SYSERR;
     }
   
-  memcpy (&session->peer, sender, sizeof (struct GNUNET_PeerIdentity));
-  session->state = REQUEST_FROM_SERVICE_RECEIVED;
-  session->element_count = ntohs (msg->element_count);
+  memcpy (&session->peer, &session->peer, sizeof (struct GNUNET_PeerIdentity));
+  session->state = SERVICE_REQUEST_RECEIVED;
+  session->element_count = ntohl (msg->element_count);
   session->used_element_count = used_elements;
   session->tunnel = tunnel;
 
@@ -1716,7 +1818,7 @@ handle_service_request (void *cls,
   current += pk_length;
 
   //check if service queue contains a matching request 
-  needed_state = MESSAGE_FROM_RESPONDING_CLIENT_RECEIVED;
+  needed_state = CLIENT_RESPONSE_RECEIVED;
   responder_session = find_matching_session (from_client_tail,
                                              &session->key,
                                              session->element_count,
@@ -1761,6 +1863,7 @@ handle_service_request (void *cls,
         }
       else
           GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Got session with key %s without a matching element set, queueing.\n"), GNUNET_h2s (&session->key));
+      
       return GNUNET_OK;
     }
   else
@@ -1780,13 +1883,10 @@ except:
   free_session (session);
   // and notify our client-session that we could not complete the session
   if (responder_session)
-    {
       // we just found the responder session in this queue
-      GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, responder_session);
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                    &prepare_client_end_notification,
-                                    responder_session);
-    }
+      responder_session->client_notification_task = 
+              GNUNET_SCHEDULER_add_now (&prepare_client_end_notification,
+                                        responder_session);
   return GNUNET_SYSERR;
 }
 
@@ -1801,51 +1901,46 @@ except:
  * @param message the actual message
  * @param atsi performance data for the connection
  * @return #GNUNET_OK to keep the connection open,
- *         #GNUNET_SYSERR to close it (signal serious error)
+ *         #GNUNET_SYSERR to close it (we are done)
  */
 static int
 handle_service_response (void *cls,
                          struct GNUNET_MESH_Tunnel * tunnel,
                          void **tunnel_ctx,
-                         const struct GNUNET_PeerIdentity * sender,
-                         const struct GNUNET_MessageHeader * message,
-                         const struct GNUNET_ATS_Information * atsi)
+                         const struct GNUNET_MessageHeader * message)
 {
-
   struct ServiceSession * session;
-  struct GNUNET_SCALARPRODUCT_service_response * msg = (struct GNUNET_SCALARPRODUCT_service_response *) message;
+  const struct GNUNET_SCALARPRODUCT_service_response * msg = (const struct GNUNET_SCALARPRODUCT_service_response *) message;
   unsigned char * current;
-  uint16_t count;
+  uint32_t count;
   gcry_mpi_t s = NULL;
   gcry_mpi_t s_prime = NULL;
   size_t read;
   size_t i;
-  uint16_t used_element_count;
+  uint32_t used_element_count;
   size_t msg_size;
   gcry_mpi_t * r = NULL;
   gcry_mpi_t * r_prime = NULL;
   int rc;
 
   GNUNET_assert (NULL != message);
-  GNUNET_assert (NULL != sender);
-  GNUNET_assert (NULL != tunnel_ctx);
   session = (struct ServiceSession *) * tunnel_ctx;
-  GNUNET_assert (NULL != session);
+  if (ALICE != session->role){
+    GNUNET_break_op(0);
+    return GNUNET_SYSERR;
+  }
+  
   count = session->used_element_count;
   session->product = NULL;
+  session->state = SERVICE_RESPONSE_RECEIVED;
 
-  if (memcmp (&session->peer, sender, sizeof (struct GNUNET_PeerIdentity)))
-    {
-      GNUNET_break_op (0);
-      goto invalid_msg;
-    }
   //we need at least a peer and one message id to compare
   if (sizeof (struct GNUNET_SCALARPRODUCT_service_response) > ntohs (msg->header.size))
     {
       GNUNET_break_op (0);
       goto invalid_msg;
     }
-  used_element_count = ntohs (msg->used_element_count);
+  used_element_count = ntohl (msg->used_element_count);
   msg_size = sizeof (struct GNUNET_SCALARPRODUCT_service_response)
           + 2 * used_element_count * PAILLIER_ELEMENT_LENGTH
           + 2 * PAILLIER_ELEMENT_LENGTH;
@@ -1884,7 +1979,7 @@ handle_service_response (void *cls,
                            PAILLIER_ELEMENT_LENGTH, &read)))
         {
           LOG_GCRY (GNUNET_ERROR_TYPE_DEBUG, "gcry_mpi_scan", rc);
-      GNUNET_break_op (0);
+          GNUNET_break_op (0);
           goto invalid_msg;
         }
       current += PAILLIER_ELEMENT_LENGTH;
@@ -1899,12 +1994,11 @@ handle_service_response (void *cls,
                            PAILLIER_ELEMENT_LENGTH, &read)))
         {
           LOG_GCRY (GNUNET_ERROR_TYPE_DEBUG, "gcry_mpi_scan", rc);
-      GNUNET_break_op (0);
+          GNUNET_break_op (0);
           goto invalid_msg;
         }
       current += PAILLIER_ELEMENT_LENGTH;
     }
-  
   session->product = compute_scalar_product (session, r, r_prime, s, s_prime);
   
 invalid_msg:
@@ -1919,18 +2013,17 @@ invalid_msg:
   GNUNET_free_non_null (r);
   GNUNET_free_non_null (r_prime);
   
-  session->state = FINALIZED;
+  session->tunnel = NULL;
+  // send message with product to client
+  session->client_notification_task = 
+             GNUNET_SCHEDULER_add_now (&prepare_client_response, 
+                                        session);
   // the tunnel has done its job, terminate our connection and the tunnel
   // the peer will be notified that the tunnel was destroyed via tunnel_destruction_handler
-  GNUNET_CONTAINER_DLL_remove (from_client_head, from_client_tail, session);
-  GNUNET_SCHEDULER_add_now (&destroy_tunnel, session); // FIXME: use after free!
-  // send message with product to client
-  /* session->current_task = */ GNUNET_SCHEDULER_add_now (&prepare_client_response, session); // FIXME: dangling task!
-  return GNUNET_OK;
-  // if success: terminate the session gracefully, else terminate with error
+  // just close the connection, as recommended by Christian
+  return GNUNET_SYSERR;
 }
 
-
 /**
  * Task run during shutdown.
  *
@@ -1941,22 +2034,30 @@ static void
 shutdown_task (void *cls,
                const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  struct ServiceSession * curr;
-  struct ServiceSession * next;
+  struct ServiceSession * session;
   GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Shutting down, initiating cleanup.\n"));
 
   do_shutdown = GNUNET_YES;
+
   // terminate all owned open tunnels.
-  for (curr = from_client_head; NULL != curr; curr = next)
+  for (session = from_client_head; NULL != session; session = session->next)
+  {
+    if (FINALIZED != session->state)
+      GNUNET_MESH_tunnel_destroy (session->tunnel);
+    if (GNUNET_SCHEDULER_NO_TASK != session->client_notification_task)
     {
-      next = curr->next;
-      if (FINALIZED != curr->state)
-        {
-          destroy_tunnel (curr, NULL);
-          curr->state = FINALIZED;
-        }
+      GNUNET_SCHEDULER_cancel (session->client_notification_task);
+      session->client_notification_task = GNUNET_SCHEDULER_NO_TASK;
     }
-  if (my_mesh)
+    if (GNUNET_SCHEDULER_NO_TASK != session->service_request_task)
+    {
+      GNUNET_SCHEDULER_cancel (session->service_request_task);
+      session->service_request_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  }
+  for (session = from_service_head; NULL != session; session = session->next)
+
+    if (my_mesh)
     {
       GNUNET_MESH_disconnect (my_mesh);
       my_mesh = NULL;
@@ -1986,11 +2087,10 @@ run (void *cls,
     { &handle_service_response, GNUNET_MESSAGE_TYPE_SCALARPRODUCT_BOB_TO_ALICE, 0},
     {NULL, 0, 0}
   };
-  static GNUNET_MESH_ApplicationType mesh_types[] = {
+  static const uint32_t ports[] = {
     GNUNET_APPLICATION_TYPE_SCALARPRODUCT,
-    GNUNET_APPLICATION_TYPE_END
+    0
   };
-
   //generate private/public key set
   GNUNET_log (GNUNET_ERROR_TYPE_INFO, _ ("Generating Paillier-Keyset.\n"));
   generate_keyset ();
@@ -2005,7 +2105,7 @@ run (void *cls,
   my_mesh = GNUNET_MESH_connect (c, NULL,
                                  &tunnel_incoming_handler,
                                  &tunnel_destruction_handler,
-                                 mesh_handlers, mesh_types);
+                                 mesh_handlers, ports);
   if (!my_mesh)
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _ ("Connect to MESH failed\n"));