gnunet-service-seti.c

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/*
      This file is part of GNUnet
      Copyright (C) 2013-2017, 2020 GNUnet e.V.
 
      GNUnet is free software: you can redistribute it and/or modify it
      under the terms of the GNU Affero 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
      Affero General Public License for more details.
 
      You should have received a copy of the GNU Affero General Public License
      along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
     SPDX-License-Identifier: AGPL3.0-or-later
 */
#include "platform.h"
#include "gnunet-service-seti_protocol.h"
#include "gnunet_statistics_service.h"
#include "gnunet_cadet_service.h"
#include "gnunet_seti_service.h"
#include "gnunet_block_lib.h"
#include "seti.h"
 
#define INCOMING_CHANNEL_TIMEOUT GNUNET_TIME_UNIT_MINUTES
 
 
enum IntersectionOperationPhase
{
  PHASE_INITIAL,
 
  PHASE_COUNT_SENT,
 
  PHASE_BF_EXCHANGE,
 
  PHASE_MUST_SEND_DONE,
 
  PHASE_DONE_RECEIVED,
 
  PHASE_FINISHED
};
 
 
struct Set;
 
struct ElementEntry;
 
struct Operation;
 
 
struct ElementEntry
{
  struct GNUNET_SETI_Element element;
 
  struct GNUNET_HashCode element_hash;
 
  unsigned int generation_added;
 
  int remote;
};
 
 
struct Listener;
 
 
struct ClientState
{
  struct Set *set;
 
  struct Listener *listener;
 
  struct GNUNET_SERVICE_Client *client;
 
  struct GNUNET_MQ_Handle *mq;
};
 
 
struct Operation
{
  struct GNUNET_PeerIdentity peer;
 
  struct GNUNET_HashCode my_xor;
 
  struct GNUNET_HashCode other_xor;
 
  struct Operation *next;
 
  struct Operation *prev;
 
  struct GNUNET_CADET_Channel *channel;
 
  struct Listener *listener;
 
  struct GNUNET_MQ_Handle *mq;
 
  struct GNUNET_MessageHeader *context_msg;
 
  struct Set *set;
 
  struct GNUNET_CONTAINER_BloomFilter *remote_bf;
 
  struct GNUNET_CONTAINER_BloomFilter *local_bf;
 
  struct GNUNET_CONTAINER_MultiHashMap *my_elements;
 
  struct GNUNET_CONTAINER_MultiHashMapIterator *full_result_iter;
 
  char *bf_data;
 
  struct GNUNET_SCHEDULER_Task *timeout_task;
 
  uint32_t bf_data_offset;
 
  uint32_t my_element_count;
 
  uint32_t bf_data_size;
 
  uint32_t bf_bits_per_element;
 
  uint32_t salt;
 
  enum IntersectionOperationPhase phase;
 
  unsigned int generation_created;
 
  int client_done_sent;
 
  int channel_death_expected;
 
  uint32_t remote_element_count;
 
  uint32_t client_request_id;
 
  int return_intersection;
 
  uint32_t suggest_id;
 
};
 
 
struct SetContent
{
  struct GNUNET_CONTAINER_MultiHashMap *elements;
 
  unsigned int refcount;
 
  unsigned int latest_generation;
 
  int iterator_count;
};
 
 
struct Set
{
  struct Set *next;
 
  struct Set *prev;
 
  struct ClientState *cs;
 
  struct SetContent *content;
 
  uint32_t current_set_element_count;
 
  struct Operation *ops_head;
 
  struct Operation *ops_tail;
 
  unsigned int current_generation;
 
};
 
 
struct Listener
{
  struct Listener *next;
 
  struct Listener *prev;
 
  struct Operation *op_head;
 
  struct Operation *op_tail;
 
  struct ClientState *cs;
 
  struct GNUNET_CADET_Port *open_port;
 
  struct GNUNET_HashCode app_id;
 
};
 
 
static struct GNUNET_CADET_Handle *cadet;
 
static struct GNUNET_STATISTICS_Handle *_GSS_statistics;
 
static struct Listener *listener_head;
 
static struct Listener *listener_tail;
 
static unsigned int num_clients;
 
static int in_shutdown;
 
static uint32_t suggest_id;
 
 
static void
send_client_removed_element (struct Operation *op,
                             struct GNUNET_SETI_Element *element)
{
  struct GNUNET_MQ_Envelope *ev;
  struct GNUNET_SETI_ResultMessage *rm;
 
  if (GNUNET_YES == op->return_intersection)
  {
    GNUNET_break (0);
    return; /* Wrong mode for transmitting removed elements */
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending removed element (size %u) to client\n",
              element->size);
  GNUNET_STATISTICS_update (_GSS_statistics,
                            "# Element removed messages sent",
                            1,
                            GNUNET_NO);
  GNUNET_assert (0 != op->client_request_id);
  ev = GNUNET_MQ_msg_extra (rm,
                            element->size,
                            GNUNET_MESSAGE_TYPE_SETI_RESULT);
  if (NULL == ev)
  {
    GNUNET_break (0);
    return;
  }
  rm->result_status = htons (GNUNET_SETI_STATUS_DEL_LOCAL);
  rm->request_id = htonl (op->client_request_id);
  rm->element_type = element->element_type;
  GNUNET_memcpy (&rm[1],
                 element->data,
                 element->size);
  GNUNET_MQ_send (op->set->cs->mq,
                  ev);
}
 
 
static int
_GSS_is_element_of_operation (struct ElementEntry *ee,
                              struct Operation *op)
{
  return op->generation_created >= ee->generation_added;
}
 
 
static int
filtered_map_initialization (void *cls,
                             const struct GNUNET_HashCode *key,
                             void *value)
{
  struct Operation *op = cls;
  struct ElementEntry *ee = value;
  struct GNUNET_HashCode mutated_hash;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "FIMA called for %s:%u\n",
              GNUNET_h2s (&ee->element_hash),
              ee->element.size);
 
  if (GNUNET_NO == _GSS_is_element_of_operation (ee, op))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Reduced initialization, not starting with %s:%u (wrong generation)\n",
                GNUNET_h2s (&ee->element_hash),
                ee->element.size);
    return GNUNET_YES;   /* element not valid in our operation's generation */
  }
 
  /* Test if element is in other peer's bloomfilter */
  GNUNET_BLOCK_mingle_hash (&ee->element_hash,
                            op->salt,
                            &mutated_hash);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Testing mingled hash %s with salt %u\n",
              GNUNET_h2s (&mutated_hash),
              op->salt);
  if (GNUNET_NO ==
      GNUNET_CONTAINER_bloomfilter_test (op->remote_bf,
                                         &mutated_hash))
  {
    /* remove this element */
    send_client_removed_element (op,
                                 &ee->element);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Reduced initialization, not starting with %s:%u\n",
                GNUNET_h2s (&ee->element_hash),
                ee->element.size);
    return GNUNET_YES;
  }
  op->my_element_count++;
  GNUNET_CRYPTO_hash_xor (&op->my_xor,
                          &ee->element_hash,
                          &op->my_xor);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Filtered initialization of my_elements, adding %s:%u\n",
              GNUNET_h2s (&ee->element_hash),
              ee->element.size);
  GNUNET_break (GNUNET_YES ==
                GNUNET_CONTAINER_multihashmap_put (op->my_elements,
                                                   &ee->element_hash,
                                                   ee,
                                                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
 
  return GNUNET_YES;
}
 
 
static int
iterator_bf_reduce (void *cls,
                    const struct GNUNET_HashCode *key,
                    void *value)
{
  struct Operation *op = cls;
  struct ElementEntry *ee = value;
  struct GNUNET_HashCode mutated_hash;
 
  GNUNET_BLOCK_mingle_hash (&ee->element_hash,
                            op->salt,
                            &mutated_hash);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Testing mingled hash %s with salt %u\n",
              GNUNET_h2s (&mutated_hash),
              op->salt);
  if (GNUNET_NO ==
      GNUNET_CONTAINER_bloomfilter_test (op->remote_bf,
                                         &mutated_hash))
  {
    GNUNET_break (0 < op->my_element_count);
    op->my_element_count--;
    GNUNET_CRYPTO_hash_xor (&op->my_xor,
                            &ee->element_hash,
                            &op->my_xor);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Bloom filter reduction of my_elements, removing %s:%u\n",
                GNUNET_h2s (&ee->element_hash),
                ee->element.size);
    GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multihashmap_remove (op->my_elements,
                                                         &ee->element_hash,
                                                         ee));
    send_client_removed_element (op,
                                 &ee->element);
  }
  else
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Bloom filter reduction of my_elements, keeping %s:%u\n",
                GNUNET_h2s (&ee->element_hash),
                ee->element.size);
  }
  return GNUNET_YES;
}
 
 
static int
iterator_bf_create (void *cls,
                    const struct GNUNET_HashCode *key,
                    void *value)
{
  struct Operation *op = cls;
  struct ElementEntry *ee = value;
  struct GNUNET_HashCode mutated_hash;
 
  GNUNET_BLOCK_mingle_hash (&ee->element_hash,
                            op->salt,
                            &mutated_hash);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Initializing BF with hash %s with salt %u\n",
              GNUNET_h2s (&mutated_hash),
              op->salt);
  GNUNET_CONTAINER_bloomfilter_add (op->local_bf,
                                    &mutated_hash);
  return GNUNET_YES;
}
 
 
static void
_GSS_operation_destroy (struct Operation *op)
{
  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->remote_bf)
  {
    GNUNET_CONTAINER_bloomfilter_free (op->remote_bf);
    op->remote_bf = NULL;
  }
  if (NULL != op->local_bf)
  {
    GNUNET_CONTAINER_bloomfilter_free (op->local_bf);
    op->local_bf = NULL;
  }
  if (NULL != op->my_elements)
  {
    GNUNET_CONTAINER_multihashmap_destroy (op->my_elements);
    op->my_elements = NULL;
  }
  if (NULL != op->full_result_iter)
  {
    GNUNET_CONTAINER_multihashmap_iterator_destroy (
      op->full_result_iter);
    op->full_result_iter = NULL;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Destroying intersection op state done\n");
  if (NULL != set)
  {
    GNUNET_CONTAINER_DLL_remove (set->ops_head,
                                 set->ops_tail,
                                 op);
    op->set = NULL;
  }
  if (NULL != op->context_msg)
  {
    GNUNET_free (op->context_msg);
    op->context_msg = NULL;
  }
  if (NULL != (channel = op->channel))
  {
    /* 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);
  }
  /* 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. */
}
 
 
static void
_GSS_operation_destroy2 (struct Operation *op);
 
 
static void
incoming_destroy (struct Operation *op)
{
  struct Listener *listener;
 
  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;
  }
  _GSS_operation_destroy2 (op);
}
 
 
static void
send_client_done_and_destroy (void *cls)
{
  struct Operation *op = cls;
  struct GNUNET_MQ_Envelope *ev;
  struct GNUNET_SETI_ResultMessage *rm;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Intersection succeeded, sending DONE to local client\n");
  GNUNET_STATISTICS_update (_GSS_statistics,
                            "# Intersection operations succeeded",
                            1,
                            GNUNET_NO);
  ev = GNUNET_MQ_msg (rm,
                      GNUNET_MESSAGE_TYPE_SETI_RESULT);
  rm->request_id = htonl (op->client_request_id);
  rm->result_status = htons (GNUNET_SETI_STATUS_DONE);
  rm->element_type = htons (0);
  GNUNET_MQ_send (op->set->cs->mq,
                  ev);
  _GSS_operation_destroy (op);
}
 
 
static void
_GSS_operation_destroy2 (struct Operation *op)
{
  struct GNUNET_CADET_Channel *channel;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "channel_end_cb called\n");
  if (NULL != (channel = op->channel))
  {
    /* 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);
  }
  if (NULL != op->listener)
  {
    incoming_destroy (op);
    return;
  }
  if (NULL != op->set)
  {
    if (GNUNET_YES == op->channel_death_expected)
    {
      /* oh goodie, we are done! */
      send_client_done_and_destroy (op);
    }
    else
    {
      /* sorry, channel went down early, too bad. */
      _GSS_operation_destroy (op);
    }
  }
  else
    _GSS_operation_destroy (op);
  GNUNET_free (op);
}
 
 
static void
fail_intersection_operation (struct Operation *op)
{
  struct GNUNET_MQ_Envelope *ev;
  struct GNUNET_SETI_ResultMessage *msg;
 
  GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
              "Intersection operation failed\n");
  GNUNET_STATISTICS_update (_GSS_statistics,
                            "# Intersection operations failed",
                            1,
                            GNUNET_NO);
  if (NULL != op->my_elements)
  {
    GNUNET_CONTAINER_multihashmap_destroy (op->my_elements);
    op->my_elements = NULL;
  }
  ev = GNUNET_MQ_msg (msg,
                      GNUNET_MESSAGE_TYPE_SETI_RESULT);
  msg->result_status = htons (GNUNET_SETI_STATUS_FAILURE);
  msg->request_id = htonl (op->client_request_id);
  msg->element_type = htons (0);
  GNUNET_MQ_send (op->set->cs->mq,
                  ev);
  _GSS_operation_destroy (op);
}
 
 
static void
send_bloomfilter (struct Operation *op)
{
  struct GNUNET_MQ_Envelope *ev;
  struct BFMessage *msg;
  uint32_t bf_size;
  uint32_t bf_elementbits;
  uint32_t chunk_size;
  char *bf_data;
  uint32_t offset;
 
  /* We consider the ratio of the set sizes to determine
     the number of bits per element, as the smaller set
     should use more bits to maximize its set reduction
     potential and minimize overall bandwidth consumption. */
  bf_elementbits = 2 + ceil (log2 ((double)
                                   (op->remote_element_count
                                    / (double) op->my_element_count)));
  if (bf_elementbits < 1)
    bf_elementbits = 1; /* make sure k is not 0 */
  /* optimize BF-size to ~50% of bits set */
  bf_size = ceil ((double) (op->my_element_count
                            * bf_elementbits / log (2)));
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending Bloom filter (%u) of size %u bytes\n",
              (unsigned int) bf_elementbits,
              (unsigned int) bf_size);
  op->local_bf = GNUNET_CONTAINER_bloomfilter_init (NULL,
                                                    bf_size,
                                                    bf_elementbits);
  op->salt = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
                                       UINT32_MAX);
  GNUNET_CONTAINER_multihashmap_iterate (op->my_elements,
                                         &iterator_bf_create,
                                         op);
 
  /* send our Bloom filter */
  GNUNET_STATISTICS_update (_GSS_statistics,
                            "# Intersection Bloom filters sent",
                            1,
                            GNUNET_NO);
  chunk_size = 60 * 1024 - sizeof(struct BFMessage);
  if (bf_size <= chunk_size)
  {
    /* singlepart */
    chunk_size = bf_size;
    ev = GNUNET_MQ_msg_extra (msg,
                              chunk_size,
                              GNUNET_MESSAGE_TYPE_SETI_P2P_BF);
    GNUNET_assert (GNUNET_SYSERR !=
                   GNUNET_CONTAINER_bloomfilter_get_raw_data (
                     op->local_bf,
                     (char *) &msg[1],
                     bf_size));
    msg->sender_element_count = htonl (op->my_element_count);
    msg->bloomfilter_total_length = htonl (bf_size);
    msg->bits_per_element = htonl (bf_elementbits);
    msg->sender_mutator = htonl (op->salt);
    msg->element_xor_hash = op->my_xor;
    GNUNET_MQ_send (op->mq, ev);
  }
  else
  {
    /* multipart */
    bf_data = GNUNET_malloc (bf_size);
    GNUNET_assert (GNUNET_SYSERR !=
                   GNUNET_CONTAINER_bloomfilter_get_raw_data (
                     op->local_bf,
                     bf_data,
                     bf_size));
    offset = 0;
    while (offset < bf_size)
    {
      if (bf_size - chunk_size < offset)
        chunk_size = bf_size - offset;
      ev = GNUNET_MQ_msg_extra (msg,
                                chunk_size,
                                GNUNET_MESSAGE_TYPE_SETI_P2P_BF);
      GNUNET_memcpy (&msg[1],
                     &bf_data[offset],
                     chunk_size);
      offset += chunk_size;
      msg->sender_element_count = htonl (op->my_element_count);
      msg->bloomfilter_total_length = htonl (bf_size);
      msg->bits_per_element = htonl (bf_elementbits);
      msg->sender_mutator = htonl (op->salt);
      msg->element_xor_hash = op->my_xor;
      GNUNET_MQ_send (op->mq, ev);
    }
    GNUNET_free (bf_data);
  }
  GNUNET_CONTAINER_bloomfilter_free (op->local_bf);
  op->local_bf = NULL;
}
 
 
static void
finished_local_operations (void *cls)
{
  struct Operation *op = cls;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "DONE sent to other peer, now waiting for other end to close the channel\n");
  op->phase = PHASE_FINISHED;
  op->channel_death_expected = GNUNET_YES;
}
 
 
static void
send_p2p_done (struct Operation *op)
{
  struct GNUNET_MQ_Envelope *ev;
  struct IntersectionDoneMessage *idm;
 
  GNUNET_assert (PHASE_MUST_SEND_DONE == op->phase);
  GNUNET_assert (GNUNET_NO == op->channel_death_expected);
  ev = GNUNET_MQ_msg (idm,
                      GNUNET_MESSAGE_TYPE_SETI_P2P_DONE);
  idm->final_element_count = htonl (op->my_element_count);
  idm->element_xor_hash = op->my_xor;
  GNUNET_MQ_notify_sent (ev,
                         &finished_local_operations,
                         op);
  GNUNET_MQ_send (op->mq,
                  ev);
}
 
 
static void
send_remaining_elements (void *cls)
{
  struct Operation *op = cls;
  const void *nxt;
  const struct ElementEntry *ee;
  struct GNUNET_MQ_Envelope *ev;
  struct GNUNET_SETI_ResultMessage *rm;
  const struct GNUNET_SETI_Element *element;
  int res;
 
  if (GNUNET_NO == op->return_intersection)
  {
    GNUNET_break (0);
    return; /* Wrong mode for transmitting removed elements */
  }
  res = GNUNET_CONTAINER_multihashmap_iterator_next (
    op->full_result_iter,
    NULL,
    &nxt);
  if (GNUNET_NO == res)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Sending done and destroy because iterator ran out\n");
    GNUNET_CONTAINER_multihashmap_iterator_destroy (
      op->full_result_iter);
    op->full_result_iter = NULL;
    if (PHASE_DONE_RECEIVED == op->phase)
    {
      op->phase = PHASE_FINISHED;
      send_client_done_and_destroy (op);
    }
    else if (PHASE_MUST_SEND_DONE == op->phase)
    {
      send_p2p_done (op);
    }
    else
    {
      GNUNET_assert (0);
    }
    return;
  }
  ee = nxt;
  element = &ee->element;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending element %s:%u to client (full set)\n",
              GNUNET_h2s (&ee->element_hash),
              element->size);
  GNUNET_assert (0 != op->client_request_id);
  ev = GNUNET_MQ_msg_extra (rm,
                            element->size,
                            GNUNET_MESSAGE_TYPE_SETI_RESULT);
  GNUNET_assert (NULL != ev);
  rm->result_status = htons (GNUNET_SETI_STATUS_ADD_LOCAL);
  rm->request_id = htonl (op->client_request_id);
  rm->element_type = element->element_type;
  GNUNET_memcpy (&rm[1],
                 element->data,
                 element->size);
  GNUNET_MQ_notify_sent (ev,
                         &send_remaining_elements,
                         op);
  GNUNET_MQ_send (op->set->cs->mq,
                  ev);
}
 
 
static int
initialize_map_unfiltered (void *cls,
                           const struct GNUNET_HashCode *key,
                           void *value)
{
  struct ElementEntry *ee = value;
  struct Operation *op = cls;
 
  if (GNUNET_NO == _GSS_is_element_of_operation (ee, op))
    return GNUNET_YES; /* element not live in operation's generation */
  GNUNET_CRYPTO_hash_xor (&op->my_xor,
                          &ee->element_hash,
                          &op->my_xor);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Initial full initialization of my_elements, adding %s:%u\n",
              GNUNET_h2s (&ee->element_hash),
              ee->element.size);
  GNUNET_break (GNUNET_YES ==
                GNUNET_CONTAINER_multihashmap_put (op->my_elements,
                                                   &ee->element_hash,
                                                   ee,
                                                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
  return GNUNET_YES;
}
 
 
static void
send_element_count (struct Operation *op)
{
  struct GNUNET_MQ_Envelope *ev;
  struct IntersectionElementInfoMessage *msg;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sending our element count (%u)\n",
              op->my_element_count);
  ev = GNUNET_MQ_msg (msg,
                      GNUNET_MESSAGE_TYPE_SETI_P2P_ELEMENT_INFO);
  msg->sender_element_count = htonl (op->my_element_count);
  GNUNET_MQ_send (op->mq, ev);
}
 
 
static void
begin_bf_exchange (struct Operation *op)
{
  op->phase = PHASE_BF_EXCHANGE;
  GNUNET_CONTAINER_multihashmap_iterate (op->set->content->elements,
                                         &initialize_map_unfiltered,
                                         op);
  send_bloomfilter (op);
}
 
 
static void
handle_intersection_p2p_element_info (void *cls,
                                      const struct
                                      IntersectionElementInfoMessage *msg)
{
  struct Operation *op = cls;
 
  op->remote_element_count = ntohl (msg->sender_element_count);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received remote element count (%u), I have %u\n",
              op->remote_element_count,
              op->my_element_count);
  if (((PHASE_INITIAL != op->phase) &&
       (PHASE_COUNT_SENT != op->phase)) ||
      (op->my_element_count > op->remote_element_count) ||
      (0 == op->my_element_count) ||
      (0 == op->remote_element_count))
  {
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  }
  GNUNET_break (NULL == op->remote_bf);
  begin_bf_exchange (op);
  GNUNET_CADET_receive_done (op->channel);
}
 
 
static void
process_bf (struct Operation *op)
{
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received BF in phase %u, foreign count is %u, my element count is %u/%u\n",
              op->phase,
              op->remote_element_count,
              op->my_element_count,
              GNUNET_CONTAINER_multihashmap_size (op->set->content->elements));
  switch (op->phase)
  {
  case PHASE_INITIAL:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  case PHASE_COUNT_SENT:
    /* This is the first BF being sent, build our initial map with
       filtering in place */
    op->my_element_count = 0;
    GNUNET_CONTAINER_multihashmap_iterate (op->set->content->elements,
                                           &filtered_map_initialization,
                                           op);
    break;
  case PHASE_BF_EXCHANGE:
    /* Update our set by reduction */
    GNUNET_CONTAINER_multihashmap_iterate (op->my_elements,
                                           &iterator_bf_reduce,
                                           op);
    break;
  case PHASE_MUST_SEND_DONE:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  case PHASE_DONE_RECEIVED:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  case PHASE_FINISHED:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  }
  GNUNET_CONTAINER_bloomfilter_free (op->remote_bf);
  op->remote_bf = NULL;
 
  if ((0 == op->my_element_count) ||  /* fully disjoint */
      ((op->my_element_count == op->remote_element_count) &&
       (0 == GNUNET_memcmp (&op->my_xor,
                            &op->other_xor))))
  {
    /* we are done */
    op->phase = PHASE_MUST_SEND_DONE;
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Intersection succeeded, sending DONE to other peer\n");
    GNUNET_CONTAINER_bloomfilter_free (op->local_bf);
    op->local_bf = NULL;
    if (GNUNET_YES == op->return_intersection)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Sending full result set (%u elements)\n",
                  GNUNET_CONTAINER_multihashmap_size (op->my_elements));
      op->full_result_iter
        = GNUNET_CONTAINER_multihashmap_iterator_create (
            op->my_elements);
      send_remaining_elements (op);
      return;
    }
    send_p2p_done (op);
    return;
  }
  op->phase = PHASE_BF_EXCHANGE;
  send_bloomfilter (op);
}
 
 
static int
check_intersection_p2p_bf (void *cls,
                           const struct BFMessage *msg)
{
  struct Operation *op = cls;
 
  (void) op;
  return GNUNET_OK;
}
 
 
static void
handle_intersection_p2p_bf (void *cls,
                            const struct BFMessage *msg)
{
  struct Operation *op = cls;
  uint32_t bf_size;
  uint32_t chunk_size;
  uint32_t bf_bits_per_element;
 
  switch (op->phase)
  {
  case PHASE_INITIAL:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
 
  case PHASE_COUNT_SENT:
  case PHASE_BF_EXCHANGE:
    bf_size = ntohl (msg->bloomfilter_total_length);
    bf_bits_per_element = ntohl (msg->bits_per_element);
    chunk_size = htons (msg->header.size) - sizeof(struct BFMessage);
    op->other_xor = msg->element_xor_hash;
    if (bf_size == chunk_size)
    {
      if (NULL != op->bf_data)
      {
        GNUNET_break_op (0);
        fail_intersection_operation (op);
        return;
      }
      /* single part, done here immediately */
      op->remote_bf
        = GNUNET_CONTAINER_bloomfilter_init ((const char *) &msg[1],
                                             bf_size,
                                             bf_bits_per_element);
      op->salt = ntohl (msg->sender_mutator);
      op->remote_element_count = ntohl (msg->sender_element_count);
      process_bf (op);
      break;
    }
    /* multipart chunk */
    if (NULL == op->bf_data)
    {
      /* first chunk, initialize */
      op->bf_data = GNUNET_malloc (bf_size);
      op->bf_data_size = bf_size;
      op->bf_bits_per_element = bf_bits_per_element;
      op->bf_data_offset = 0;
      op->salt = ntohl (msg->sender_mutator);
      op->remote_element_count = ntohl (msg->sender_element_count);
    }
    else
    {
      /* increment */
      if ((op->bf_data_size != bf_size) ||
          (op->bf_bits_per_element != bf_bits_per_element) ||
          (op->bf_data_offset + chunk_size > bf_size) ||
          (op->salt != ntohl (msg->sender_mutator)) ||
          (op->remote_element_count != ntohl (msg->sender_element_count)))
      {
        GNUNET_break_op (0);
        fail_intersection_operation (op);
        return;
      }
    }
    GNUNET_memcpy (&op->bf_data[op->bf_data_offset],
                   (const char *) &msg[1],
                   chunk_size);
    op->bf_data_offset += chunk_size;
    if (op->bf_data_offset == bf_size)
    {
      /* last chunk, run! */
      op->remote_bf
        = GNUNET_CONTAINER_bloomfilter_init (op->bf_data,
                                             bf_size,
                                             bf_bits_per_element);
      GNUNET_free (op->bf_data);
      op->bf_data = NULL;
      op->bf_data_size = 0;
      process_bf (op);
    }
    break;
 
  default:
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  }
  GNUNET_CADET_receive_done (op->channel);
}
 
 
static int
filter_all (void *cls,
            const struct GNUNET_HashCode *key,
            void *value)
{
  struct Operation *op = cls;
  struct ElementEntry *ee = value;
 
  GNUNET_break (0 < op->my_element_count);
  op->my_element_count--;
  GNUNET_CRYPTO_hash_xor (&op->my_xor,
                          &ee->element_hash,
                          &op->my_xor);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Final reduction of my_elements, removing %s:%u\n",
              GNUNET_h2s (&ee->element_hash),
              ee->element.size);
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multihashmap_remove (op->my_elements,
                                                       &ee->element_hash,
                                                       ee));
  send_client_removed_element (op,
                               &ee->element);
  return GNUNET_YES;
}
 
 
static void
handle_intersection_p2p_done (void *cls,
                              const struct IntersectionDoneMessage *idm)
{
  struct Operation *op = cls;
 
  if (PHASE_BF_EXCHANGE != op->phase)
  {
    /* wrong phase to conclude? FIXME: Or should we allow this
       if the other peer has _initially_ already an empty set? */
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  }
  if (0 == ntohl (idm->final_element_count))
  {
    /* other peer determined empty set is the intersection,
       remove all elements */
    GNUNET_CONTAINER_multihashmap_iterate (op->my_elements,
                                           &filter_all,
                                           op);
  }
  if ((op->my_element_count != ntohl (idm->final_element_count)) ||
      (0 != GNUNET_memcmp (&op->my_xor,
                           &idm->element_xor_hash)))
  {
    /* Other peer thinks we are done, but we disagree on the result! */
    GNUNET_break_op (0);
    fail_intersection_operation (op);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Got IntersectionDoneMessage, have %u elements in intersection\n",
              op->my_element_count);
  op->phase = PHASE_DONE_RECEIVED;
  GNUNET_CADET_receive_done (op->channel);
 
  GNUNET_assert (GNUNET_NO == op->client_done_sent);
  if (GNUNET_YES == op->return_intersection)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Sending full result set to client (%u elements)\n",
                GNUNET_CONTAINER_multihashmap_size (op->my_elements));
    op->full_result_iter
      = GNUNET_CONTAINER_multihashmap_iterator_create (op->my_elements);
    send_remaining_elements (op);
    return;
  }
  op->phase = PHASE_FINISHED;
  send_client_done_and_destroy (op);
}
 
 
static struct Operation *
get_incoming (uint32_t id)
{
  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;
}
 
 
static void *
client_connect_cb (void *cls,
                   struct GNUNET_SERVICE_Client *c,
                   struct GNUNET_MQ_Handle *mq)
{
  struct ClientState *cs;
 
  num_clients++;
  cs = GNUNET_new (struct ClientState);
  cs->client = c;
  cs->mq = mq;
  return cs;
}
 
 
static int
destroy_elements_iterator (void *cls,
                           const struct GNUNET_HashCode *key,
                           void *value)
{
  struct ElementEntry *ee = value;
 
  GNUNET_free (ee);
  return GNUNET_YES;
}
 
 
static void
client_disconnect_cb (void *cls,
                      struct GNUNET_SERVICE_Client *client,
                      void *internal_cls)
{
  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;
 
    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);
 
    /* 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 (set);
  }
 
  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;
    }
  }
}
 
 
static int
check_incoming_msg (void *cls,
                    const struct OperationRequestMessage *msg)
{
  struct Operation *op = cls;
  struct Listener *listener = op->listener;
  const struct GNUNET_MessageHeader *nested_context;
 
  /* double operation request */
  if (0 != op->suggest_id)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  /* This should be equivalent to the previous condition, but can't hurt to check twice */
  if (NULL == listener)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  nested_context = GNUNET_MQ_extract_nested_mh (msg);
  if ((NULL != nested_context) &&
      (ntohs (nested_context->size) > GNUNET_SETI_CONTEXT_MESSAGE_MAX_SIZE))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}
 
 
static void
handle_incoming_msg (void *cls,
                     const struct OperationRequestMessage *msg)
{
  struct Operation *op = cls;
  struct Listener *listener = op->listener;
  const struct GNUNET_MessageHeader *nested_context;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_SETI_RequestMessage *cmsg;
 
  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 (port %s) for active listener\n",
    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_SETI_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() */
}
 
 
static void
handle_client_create_set (void *cls,
                          const struct GNUNET_SETI_CreateMessage *msg)
{
  struct ClientState *cs = cls;
  struct Set *set;
 
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client created new intersection set\n");
  if (NULL != cs->set)
  {
    /* There can only be one set per client */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  set = GNUNET_new (struct Set);
  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);
}
 
 
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);
}
 
 
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;
}
 
 
static void
channel_end_cb (void *channel_ctx,
                const struct GNUNET_CADET_Channel *channel)
{
  struct Operation *op = channel_ctx;
 
  op->channel = NULL;
  _GSS_operation_destroy2 (op);
}
 
 
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... */
}
 
 
static void
handle_client_listen (void *cls,
                      const struct GNUNET_SETI_ListenMessage *msg)
{
  struct ClientState *cs = cls;
  struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
    GNUNET_MQ_hd_var_size (incoming_msg,
                           GNUNET_MESSAGE_TYPE_SETI_P2P_OPERATION_REQUEST,
                           struct OperationRequestMessage,
                           NULL),
    GNUNET_MQ_hd_fixed_size (intersection_p2p_element_info,
                             GNUNET_MESSAGE_TYPE_SETI_P2P_ELEMENT_INFO,
                             struct IntersectionElementInfoMessage,
                             NULL),
    GNUNET_MQ_hd_var_size (intersection_p2p_bf,
                           GNUNET_MESSAGE_TYPE_SETI_P2P_BF,
                           struct BFMessage,
                           NULL),
    GNUNET_MQ_hd_fixed_size (intersection_p2p_done,
                             GNUNET_MESSAGE_TYPE_SETI_P2P_DONE,
                             struct IntersectionDoneMessage,
                             NULL),
    GNUNET_MQ_handler_end ()
  };
  struct Listener *listener;
 
  if (NULL != cs->listener)
  {
    /* max. one active listener per client! */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  listener = GNUNET_new (struct Listener);
  listener->cs = cs;
  cs->listener = listener;
  listener->app_id = msg->app_id;
  GNUNET_CONTAINER_DLL_insert (listener_head,
                               listener_tail,
                               listener);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "New listener for set intersection created (port %s)\n",
              GNUNET_h2s (&listener->app_id));
  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);
}
 
 
static void
handle_client_reject (void *cls,
                      const struct GNUNET_SETI_RejectMessage *msg)
{
  struct ClientState *cs = cls;
  struct Operation *op;
 
  op = get_incoming (ntohl (msg->accept_reject_id));
  if (NULL == op)
  {
    /* 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 (app %s) rejected by client\n",
              GNUNET_h2s (&cs->listener->app_id));
  _GSS_operation_destroy2 (op);
  GNUNET_SERVICE_client_continue (cs->client);
}
 
 
static int
check_client_set_add (void *cls,
                      const struct GNUNET_SETI_ElementMessage *msg)
{
  /* NOTE: Technically, we should probably check with the
     block library whether the element we are given is well-formed */
  return GNUNET_OK;
}
 
 
static void
handle_client_set_add (void *cls,
                       const struct GNUNET_SETI_ElementMessage *msg)
{
  struct ClientState *cs = cls;
  struct Set *set;
  struct GNUNET_SETI_Element el;
  struct ElementEntry *ee;
  struct GNUNET_HashCode hash;
 
  if (NULL == (set = cs->set))
  {
    /* client without a set requested an operation */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  GNUNET_SERVICE_client_continue (cs->client);
  el.size = ntohs (msg->header.size) - sizeof(*msg);
  el.data = &msg[1];
  el.element_type = ntohs (msg->element_type);
  GNUNET_SETI_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->element_hash = hash;
    GNUNET_break (GNUNET_YES ==
                  GNUNET_CONTAINER_multihashmap_put (
                    set->content->elements,
                    &ee->element_hash,
                    ee,
                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
  }
  else
  {
    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;
  }
  set->current_set_element_count++;
}
 
 
static void
advance_generation (struct Set *set)
{
  if (set->current_generation == set->content->latest_generation)
  {
    set->content->latest_generation++;
    set->current_generation++;
    return;
  }
  GNUNET_assert (set->current_generation < set->content->latest_generation);
}
 
 
static int
check_client_evaluate (void *cls,
                       const struct GNUNET_SETI_EvaluateMessage *msg)
{
  /* FIXME: suboptimal, even if the context below could be NULL,
     there are malformed messages this does not check for... */
  return GNUNET_OK;
}
 
 
static void
handle_client_evaluate (void *cls,
                        const struct GNUNET_SETI_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_SETI_P2P_OPERATION_REQUEST,
                           struct OperationRequestMessage,
                           op),
    GNUNET_MQ_hd_fixed_size (intersection_p2p_element_info,
                             GNUNET_MESSAGE_TYPE_SETI_P2P_ELEMENT_INFO,
                             struct IntersectionElementInfoMessage,
                             op),
    GNUNET_MQ_hd_var_size (intersection_p2p_bf,
                           GNUNET_MESSAGE_TYPE_SETI_P2P_BF,
                           struct BFMessage,
                           op),
    GNUNET_MQ_hd_fixed_size (intersection_p2p_done,
                             GNUNET_MESSAGE_TYPE_SETI_P2P_DONE,
                             struct IntersectionDoneMessage,
                             op),
    GNUNET_MQ_handler_end ()
  };
  struct Set *set;
  const struct GNUNET_MessageHeader *context;
 
  if (NULL == (set = cs->set))
  {
    GNUNET_break (0);
    GNUNET_free (op);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  op->salt = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
                                       UINT32_MAX);
  op->peer = msg->target_peer;
  op->return_intersection = htonl (msg->return_intersection);
  fprintf (stderr,
           "Return intersection for evaluate is %d\n",
           op->return_intersection);
  op->client_request_id = ntohl (msg->request_id);
  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 intersection\n",
              GNUNET_h2s (&msg->app_id));
  op->channel = GNUNET_CADET_channel_create (cadet,
                                             op,
                                             &msg->target_peer,
                                             &msg->app_id,
                                             &channel_window_cb,
                                             &channel_end_cb,
                                             cadet_handlers);
  op->mq = GNUNET_CADET_get_mq (op->channel);
  {
    struct GNUNET_MQ_Envelope *ev;
    struct OperationRequestMessage *msg;
 
    ev = GNUNET_MQ_msg_nested_mh (msg,
                                  GNUNET_MESSAGE_TYPE_SETI_P2P_OPERATION_REQUEST,
                                  context);
    if (NULL == ev)
    {
      /* the context message is too large!? */
      GNUNET_break (0);
      GNUNET_SERVICE_client_drop (cs->client);
      return;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Initiating intersection operation evaluation\n");
    /* we started the operation, thus we have to send the operation request */
    op->phase = PHASE_INITIAL;
    op->my_element_count = op->set->current_set_element_count;
    op->my_elements
      = GNUNET_CONTAINER_multihashmap_create (op->my_element_count,
                                              GNUNET_YES);
 
    msg->element_count = htonl (op->my_element_count);
    GNUNET_MQ_send (op->mq,
                    ev);
    op->phase = PHASE_COUNT_SENT;
    if (NULL != context)
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Sent op request with context message\n");
    else
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Sent op request without context message\n");
  }
  GNUNET_SERVICE_client_continue (cs->client);
}
 
 
static void
handle_client_cancel (void *cls,
                      const struct GNUNET_SETI_CancelMessage *msg)
{
  struct ClientState *cs = cls;
  struct Set *set;
  struct Operation *op;
  int found;
 
  if (NULL == (set = cs->set))
  {
    /* client without a set requested an operation */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  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_SERVICE_client_continue (cs->client);
}
 
 
static void
handle_client_accept (void *cls,
                      const struct GNUNET_SETI_AcceptMessage *msg)
{
  struct ClientState *cs = cls;
  struct Set *set;
  struct Operation *op;
  struct GNUNET_SETI_ResultMessage *result_message;
  struct GNUNET_MQ_Envelope *ev;
  struct Listener *listener;
 
  if (NULL == (set = cs->set))
  {
    /* client without a set requested to accept */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cs->client);
    return;
  }
  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_SETI_RESULT);
    result_message->request_id = msg->request_id;
    result_message->result_status = htons (GNUNET_SETI_STATUS_FAILURE);
    GNUNET_MQ_send (set->cs->mq, ev);
    GNUNET_SERVICE_client_continue (cs->client);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client accepting request %u\n",
              (uint32_t) ntohl (msg->accept_reject_id));
  listener = op->listener;
  op->listener = NULL;
  op->return_intersection = htonl (msg->return_intersection);
  fprintf (stderr,
           "Return intersection for accept is %d\n",
           op->return_intersection);
  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);
 
  /* Advance generation values, so that future mutations do not
     interfer with the running operation. */
  op->generation_created = set->current_generation;
  advance_generation (set);
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Accepting set intersection operation\n");
    op->phase = PHASE_INITIAL;
    op->my_element_count
      = op->set->current_set_element_count;
    op->my_elements
      = GNUNET_CONTAINER_multihashmap_create (
          GNUNET_MIN (op->my_element_count,
                      op->remote_element_count),
          GNUNET_YES);
    if (op->remote_element_count < op->my_element_count)
    {
      /* If the other peer (Alice) has fewer elements than us (Bob),
         we just send the count as Alice should send the first BF */
      send_element_count (op);
      op->phase = PHASE_COUNT_SENT;
    }
    else
    {
      /* We have fewer elements, so we start with the BF */
      begin_bf_exchange (op);
    }
  }
  /* 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);
}
 
 
static void
shutdown_task (void *cls)
{
  /* 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 shutdown request\n");
}
 
 
static void
run (void *cls,
     const struct GNUNET_CONFIGURATION_Handle *cfg,
     struct GNUNET_SERVICE_Handle *service)
{
  /* 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 ("seti",
                                              cfg);
  cadet = GNUNET_CADET_connect (cfg);
  if (NULL == cadet)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _ ("Could not connect to CADET service\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
}
 
 
GNUNET_SERVICE_MAIN (
  "seti",
  GNUNET_SERVICE_OPTION_NONE,
  &run,
  &client_connect_cb,
  &client_disconnect_cb,
  NULL,
  GNUNET_MQ_hd_fixed_size (client_accept,
                           GNUNET_MESSAGE_TYPE_SETI_ACCEPT,
                           struct GNUNET_SETI_AcceptMessage,
                           NULL),
  GNUNET_MQ_hd_var_size (client_set_add,
                         GNUNET_MESSAGE_TYPE_SETI_ADD,
                         struct GNUNET_SETI_ElementMessage,
                         NULL),
  GNUNET_MQ_hd_fixed_size (client_create_set,
                           GNUNET_MESSAGE_TYPE_SETI_CREATE,
                           struct GNUNET_SETI_CreateMessage,
                           NULL),
  GNUNET_MQ_hd_var_size (client_evaluate,
                         GNUNET_MESSAGE_TYPE_SETI_EVALUATE,
                         struct GNUNET_SETI_EvaluateMessage,
                         NULL),
  GNUNET_MQ_hd_fixed_size (client_listen,
                           GNUNET_MESSAGE_TYPE_SETI_LISTEN,
                           struct GNUNET_SETI_ListenMessage,
                           NULL),
  GNUNET_MQ_hd_fixed_size (client_reject,
                           GNUNET_MESSAGE_TYPE_SETI_REJECT,
                           struct GNUNET_SETI_RejectMessage,
                           NULL),
  GNUNET_MQ_hd_fixed_size (client_cancel,
                           GNUNET_MESSAGE_TYPE_SETI_CANCEL,
                           struct GNUNET_SETI_CancelMessage,
                           NULL),
  GNUNET_MQ_handler_end ());
 
 
/* end of gnunet-service-seti.c */