gnunet-service-cadet_connection.c

Go to the documentation of this file.

/*
     This file is part of GNUnet.
     Copyright (C) 2001-2017 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 "gnunet-service-cadet.h"
#include "gnunet_common.h"
#include "gnunet_pils_service.h"
#include "gnunet_time_lib.h"
#include "platform.h"
#include "gnunet_signatures.h"
#include "gnunet-service-cadet_connection.h"
#include "gnunet-service-cadet_channel.h"
#include "gnunet-service-cadet_paths.h"
#include "gnunet-service-cadet_tunnels.h"
#include "gnunet_cadet_service.h"
#include "gnunet_statistics_service.h"
#include "cadet_protocol.h"
 
 
#define LOG(level, ...) GNUNET_log_from (level, "cadet-con", __VA_ARGS__)
 
 
#define INITIAL_CONNECTION_CREATE_RETRY_DELAY \
        GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 200)
 
 
enum CadetConnectionState
{
  CADET_CONNECTION_NEW,
 
  CADET_CONNECTION_SENDING_CREATE,
 
  CADET_CONNECTION_SENT,
 
  CADET_CONNECTION_CREATE_RECEIVED,
 
  CADET_CONNECTION_READY
};
 
struct CadetConnection
{
  struct GNUNET_CADET_ConnectionTunnelIdentifier cid;
 
  struct CadetPeer *destination;
 
  struct CadetTConnection *ct;
 
  struct CadetPeerPath *path;
 
  struct GNUNET_MQ_Envelope *env;
 
  struct GCP_MessageQueueManager *mq_man;
 
  struct GNUNET_SCHEDULER_Task *task;
 
  struct GNUNET_TIME_Absolute monotime;
 
  struct GNUNET_PILS_Operation *sign_op;
 
  struct CadetTunnelQueueEntry *keepalive_qe;
 
  GCC_ReadyCallback ready_cb;
 
  void *ready_cb_cls;
 
  struct GNUNET_TIME_Relative retry_delay;
 
  struct GNUNET_TIME_Absolute create_at;
 
  struct GNUNET_TIME_Absolute create_ack_at;
 
  struct CadetConnectionMetrics metrics;
 
  enum CadetConnectionState state;
 
  unsigned int latency_datapoints;
 
  unsigned int off;
 
  int mqm_ready;
};
 
 
struct CadetConnection *
GCC_lookup (const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid)
{
  return GNUNET_CONTAINER_multishortmap_get (connections,
                                             &cid->connection_of_tunnel);
}
 
 
static void
update_state (struct CadetConnection *cc,
              enum CadetConnectionState new_state,
              int new_mqm_ready)
{
  int old_ready;
  int new_ready;
 
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Trying to update connection state for %s having old state %d to new %d and mqm_ready old %d to mqm_ready new %d\n",
       GCT_2s (cc->ct->t),
       cc->state,
       new_state,
       cc->mqm_ready,
       new_mqm_ready);
 
  if ((new_state == cc->state) && (new_mqm_ready == cc->mqm_ready))
    return; /* no change, nothing to do */
  old_ready =
    ((CADET_CONNECTION_READY == cc->state) && (GNUNET_YES == cc->mqm_ready));
  new_ready =
    ((CADET_CONNECTION_READY == new_state) && (GNUNET_YES == new_mqm_ready));
  cc->state = new_state;
  cc->mqm_ready = new_mqm_ready;
 
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Updating connection state for %s having old_ready %d and new_rady %d\n",
       GCT_2s (cc->ct->t),
       old_ready,
       new_ready);
 
  if (old_ready != new_ready)
    cc->ready_cb (cc->ready_cb_cls, new_ready);
}
 
 
static void
GCC_destroy (struct CadetConnection *cc)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Destroying %s\n", GCC_2s (cc));
  if (NULL != cc->mq_man)
  {
    GCP_request_mq_cancel (cc->mq_man, NULL);
    cc->mq_man = NULL;
  }
  if (NULL != cc->task)
  {
    GNUNET_SCHEDULER_cancel (cc->task);
    cc->task = NULL;
  }
  if (NULL != cc->sign_op)
  {
    GNUNET_PILS_cancel (cc->sign_op);
    cc->sign_op = NULL;
  }
  if (NULL != cc->keepalive_qe)
  {
    GCT_send_cancel (cc->keepalive_qe);
    cc->keepalive_qe = NULL;
  }
  GCPP_del_connection (cc->path, cc->off, cc);
  for (unsigned int i = 0; i < cc->off; i++)
    GCP_remove_connection (GCPP_get_peer_at_offset (cc->path, i), cc);
  GNUNET_assert (
    GNUNET_YES ==
    GNUNET_CONTAINER_multishortmap_remove (connections,
                                           &GCC_get_id (cc)
                                           ->connection_of_tunnel,
                                           cc));
  GNUNET_free (cc);
}
 
 
void
GCC_destroy_without_core (struct CadetConnection *cc)
{
  if (NULL != cc->ct)
  {
    GCT_connection_lost (cc->ct);
    cc->ct = NULL;
  }
  GCC_destroy (cc);
}
 
 
void
GCC_destroy_without_tunnel (struct CadetConnection *cc)
{
  cc->ct = NULL;
  if ((CADET_CONNECTION_SENDING_CREATE != cc->state) && (NULL != cc->mq_man))
  {
    struct GNUNET_MQ_Envelope *env;
    struct GNUNET_CADET_ConnectionDestroyMessage *destroy_msg;
 
    /* Need to notify next hop that we are down. */
    env =
      GNUNET_MQ_msg (destroy_msg, GNUNET_MESSAGE_TYPE_CADET_CONNECTION_DESTROY);
    destroy_msg->cid = cc->cid;
    GCP_request_mq_cancel (cc->mq_man, env);
    cc->mq_man = NULL;
  }
  GCC_destroy (cc);
}
 
 
struct CadetTConnection *
GCC_get_ct (struct CadetConnection *cc)
{
  return cc->ct;
}
 
 
const struct CadetConnectionMetrics *
GCC_get_metrics (struct CadetConnection *cc)
{
  return &cc->metrics;
}
 
 
static void
send_keepalive (void *cls);
 
 
static void
keepalive_done (void *cls,
                const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid)
{
  struct CadetConnection *cc = cls;
 
  cc->keepalive_qe = NULL;
  if ((GNUNET_YES == cc->mqm_ready) && (NULL == cc->task))
    cc->task =
      GNUNET_SCHEDULER_add_delayed (keepalive_period, &send_keepalive, cc);
}
 
 
static void
send_keepalive (void *cls)
{
  struct CadetConnection *cc = cls;
  struct GNUNET_MessageHeader msg;
 
  cc->task = NULL;
  if (CADET_TUNNEL_KEY_OK != GCT_get_estate (cc->ct->t))
  {
    /* Tunnel not yet ready, wait with keepalives... */
    cc->task =
      GNUNET_SCHEDULER_add_delayed (keepalive_period, &send_keepalive, cc);
    return;
  }
  GNUNET_assert (NULL != cc->ct);
  GNUNET_assert (GNUNET_YES == cc->mqm_ready);
  GNUNET_assert (NULL == cc->keepalive_qe);
  LOG (GNUNET_ERROR_TYPE_INFO,
       "Sending KEEPALIVE on behalf of %s via %s\n",
       GCC_2s (cc),
       GCT_2s (cc->ct->t));
  GNUNET_STATISTICS_update (stats, "# keepalives sent", 1, GNUNET_NO);
  msg.size = htons (sizeof(msg));
  msg.type = htons (GNUNET_MESSAGE_TYPE_CADET_CHANNEL_KEEPALIVE);
 
  cc->keepalive_qe = GCT_send (cc->ct->t, &msg, &keepalive_done, cc, NULL);
}
 
 
void
GCC_ack_expected (const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid)
{
  struct CadetConnection *cc;
 
  cc = GCC_lookup (cid);
  if (NULL == cc)
    return; /* whopise, connection already down? */
  cc->metrics.num_acked_transmissions++;
}
 
 
void
GCC_ack_observed (const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid)
{
  struct CadetConnection *cc;
 
  cc = GCC_lookup (cid);
  if (NULL == cc)
    return; /* whopise, connection already down? */
  cc->metrics.num_successes++;
}
 
 
void
GCC_latency_observed (const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid,
                      struct GNUNET_TIME_Relative latency)
{
  struct CadetConnection *cc;
  double weight;
  double result;
 
  cc = GCC_lookup (cid);
  if (NULL == cc)
    return; /* whopise, connection already down? */
  GNUNET_STATISTICS_update (stats, "# latencies observed", 1, GNUNET_NO);
  cc->latency_datapoints++;
  if (cc->latency_datapoints >= 7)
    weight = 7.0;
  else
    weight = cc->latency_datapoints;
  /* Compute weighted average, giving at MOST weight 7 to the
     existing values, or less if that value is based on fewer than 7
     measurements. */
  result = (weight * cc->metrics.aged_latency.rel_value_us)
           + 1.0 * latency.rel_value_us;
  result /= (weight + 1.0);
  cc->metrics.aged_latency.rel_value_us = (uint64_t) result;
}
 
 
void
GCC_handle_connection_create_ack (struct CadetConnection *cc)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Received CADET_CONNECTION_CREATE_ACK for %s in state %d (%s)\n",
       GCC_2s (cc),
       cc->state,
       (GNUNET_YES == cc->mqm_ready) ? "MQM ready" : "MQM busy");
  if (CADET_CONNECTION_READY == cc->state)
    return; /* Duplicate ACK, ignore */
  if (NULL != cc->task)
  {
    GNUNET_SCHEDULER_cancel (cc->task);
    cc->task = NULL;
  }
  cc->metrics.age = GNUNET_TIME_absolute_get ();
  update_state (cc, CADET_CONNECTION_READY, cc->mqm_ready);
  if ((NULL == cc->keepalive_qe) && (GNUNET_YES == cc->mqm_ready) &&
      (NULL == cc->task))
    cc->task =
      GNUNET_SCHEDULER_add_delayed (keepalive_period, &send_keepalive, cc);
}
 
 
void
GCC_handle_kx (struct CadetConnection *cc,
               const struct GNUNET_CADET_TunnelKeyExchangeMessage *msg)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Received KX message with ephermal %s on CC %s in state %d\n",
       GNUNET_e2s (&msg->ephemeral_key),
       GNUNET_sh2s (&cc->cid.connection_of_tunnel),
       cc->state);
  if (CADET_CONNECTION_SENT == cc->state)
  {
    /* We didn't get the CADET_CONNECTION_CREATE_ACK, but instead got payload. That's fine,
       clearly something is working, so pretend we got an ACK. */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Faking connection CADET_CONNECTION_CREATE_ACK for %s due to KX\n",
         GCC_2s (cc));
    GCC_handle_connection_create_ack (cc);
  }
  GCT_handle_kx (cc->ct, msg);
}
 
 
void
GCC_handle_kx_auth (struct CadetConnection *cc,
                    const struct GNUNET_CADET_TunnelKeyExchangeAuthMessage *msg)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Received KX AUTH message with ephermal %s on CC %s in state %d\n",
       GNUNET_e2s (&msg->kx.ephemeral_key),
       GNUNET_sh2s (&cc->cid.connection_of_tunnel),
       cc->state);
  if (CADET_CONNECTION_SENT == cc->state)
  {
    /* We didn't get the CADET_CONNECTION_CREATE_ACK, but instead got payload. That's fine,
       clearly something is working, so pretend we got an ACK. */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Faking connection CADET_CONNECTION_CREATE_ACK for %s due to KX\n",
         GCC_2s (cc));
    GCC_handle_connection_create_ack (cc);
  }
  GCT_handle_kx_auth (cc->ct, msg);
}
 
 
void
GCC_handle_encrypted (struct CadetConnection *cc,
                      const struct GNUNET_CADET_TunnelEncryptedMessage *msg)
{
  if (CADET_CONNECTION_SENT == cc->state)
  {
    /* We didn't get the CREATE_ACK, but instead got payload. That's fine,
       clearly something is working, so pretend we got an ACK. */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Faking connection ACK for %s due to ENCRYPTED payload\n",
         GCC_2s (cc));
    GCC_handle_connection_create_ack (cc);
  }
  cc->metrics.last_use = GNUNET_TIME_absolute_get ();
  GCT_handle_encrypted (cc->ct, msg);
}
 
 
static void
cont_send_create (void *cls,
                  const struct GNUNET_PeerIdentity *my_identity,
                  const struct GNUNET_CRYPTO_EddsaSignature *signature)
{
  struct CadetConnection *cc = cls;
  struct GNUNET_CADET_ConnectionCreateMessage *create_msg;
  struct GNUNET_PeerIdentity *pids;
  struct GNUNET_MQ_Envelope *env;
 
  cc->sign_op = NULL;
 
  GNUNET_assert (my_identity);
 
  env =
    GNUNET_MQ_msg_extra (create_msg,
                         (2 + cc->off) * sizeof(struct GNUNET_PeerIdentity),
                         GNUNET_MESSAGE_TYPE_CADET_CONNECTION_CREATE);
  // TODO This will be removed in a major release, because this will be a protocol breaking change. We set the deprecated 'reliable' bit here that was removed.
  create_msg->options = 2;
  create_msg->cid = cc->cid;
 
  if (signature)
  {
    create_msg->has_monotime = GNUNET_YES;
    create_msg->monotime = GNUNET_TIME_absolute_hton (cc->monotime);
    create_msg->monotime_sig = *signature;
  }
 
  pids = (struct GNUNET_PeerIdentity *) &create_msg[1];
  pids[0] = *my_identity;
  for (unsigned int i = 0; i <= cc->off; i++)
    pids[i + 1] = *GCP_get_id (GCPP_get_peer_at_offset (cc->path, i));
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Sending CADET_CONNECTION_CREATE message for %s with %u hops\n",
       GCC_2s (cc),
       cc->off + 2);
  cc->env = env;
  cc->retry_delay = GNUNET_TIME_STD_BACKOFF (cc->retry_delay);
  cc->create_at = GNUNET_TIME_relative_to_absolute (cc->retry_delay);
  update_state (cc, CADET_CONNECTION_SENT, GNUNET_NO);
  GCP_send (cc->mq_man, env);
}
 
 
static void
send_create (void *cls)
{
  struct CadetConnection *cc = cls;
  struct CadetTunnel *t;
 
  cc->task = NULL;
  GNUNET_assert (GNUNET_YES == cc->mqm_ready);
 
  // check for tunnel state and set signed monotime (xrs,t3ss)
  t = GCP_get_tunnel (cc->destination, GNUNET_YES);
  if ((NULL != t) && (GCT_get_estate (t) == CADET_TUNNEL_KEY_UNINITIALIZED) &&
      (GCT_alice_or_betty (GCP_get_id (cc->destination)) == GNUNET_NO))
  {
    struct CadetConnectionCreatePS cp;
 
    cc->monotime = GNUNET_TIME_absolute_get_monotonic (cfg);
 
    cp.purpose.purpose = htonl (
      GNUNET_SIGNATURE_PURPOSE_CADET_CONNECTION_INITIATOR);
    cp.purpose.size = htonl (sizeof(cp));
    cp.monotonic_time = GNUNET_TIME_absolute_hton (cc->monotime);
 
    if (NULL != cc->sign_op)
      GNUNET_PILS_cancel (cc->sign_op);
 
    cc->sign_op = GNUNET_PILS_sign_by_peer_identity (pils, &cp.purpose,
                                                     &cont_send_create, cc);
  }
  else
    cont_send_create (cc, GNUNET_PILS_get_identity (pils), NULL);
}
 
 
static void
send_create_ack (void *cls)
{
  struct CadetConnection *cc = cls;
  struct GNUNET_CADET_ConnectionCreateAckMessage *ack_msg;
  struct GNUNET_MQ_Envelope *env;
 
  cc->task = NULL;
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Sending CONNECTION_CREATE_ACK message for %s\n",
       GCC_2s (cc));
  GNUNET_assert (GNUNET_YES == cc->mqm_ready);
  env =
    GNUNET_MQ_msg (ack_msg, GNUNET_MESSAGE_TYPE_CADET_CONNECTION_CREATE_ACK);
  ack_msg->cid = cc->cid;
  cc->env = env;
  cc->retry_delay = GNUNET_TIME_STD_BACKOFF (cc->retry_delay);
  cc->create_ack_at = GNUNET_TIME_relative_to_absolute (cc->retry_delay);
  if (CADET_CONNECTION_CREATE_RECEIVED == cc->state)
    update_state (cc, CADET_CONNECTION_READY, GNUNET_NO);
  if (CADET_CONNECTION_READY == cc->state)
    cc->task =
      GNUNET_SCHEDULER_add_delayed (keepalive_period, &send_keepalive, cc);
  GCP_send (cc->mq_man, env);
}
 
 
void
GCC_handle_duplicate_create (struct CadetConnection *cc)
{
  if (GNUNET_YES == cc->mqm_ready)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Got duplicate CREATE for %s, scheduling another ACK (%s)\n",
         GCC_2s (cc),
         (GNUNET_YES == cc->mqm_ready) ? "MQM ready" : "MQM busy");
    /* Revert back to the state of having only received the 'CREATE',
       and immediately proceed to send the CREATE_ACK. */
    update_state (cc, CADET_CONNECTION_CREATE_RECEIVED, cc->mqm_ready);
    if (NULL != cc->task)
      GNUNET_SCHEDULER_cancel (cc->task);
    cc->task =
      GNUNET_SCHEDULER_add_at (cc->create_ack_at, &send_create_ack, cc);
  }
  else
  {
    /* We are currently sending something else back, which
       can only be an ACK or payload, either of which would
       do. So actually no need to do anything. */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Got duplicate CREATE for %s. MQ is busy, not queueing another ACK\n",
         GCC_2s (cc));
  }
}
 
 
static void
manage_first_hop_mq (void *cls, int available)
{
  struct CadetConnection *cc = cls;
 
  if (GNUNET_YES != available)
  {
    /* Connection is down, for now... */
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Core MQ for %s went down\n", GCC_2s (cc));
    update_state (cc, CADET_CONNECTION_NEW, GNUNET_NO);
    cc->retry_delay = INITIAL_CONNECTION_CREATE_RETRY_DELAY;
    if (NULL != cc->task)
    {
      GNUNET_SCHEDULER_cancel (cc->task);
      cc->task = NULL;
    }
    return;
  }
 
  update_state (cc, cc->state, GNUNET_YES);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Core MQ for %s became available in state %d\n",
       GCC_2s (cc),
       cc->state);
  switch (cc->state)
  {
  case CADET_CONNECTION_NEW:
    /* Transmit immediately */
    cc->task = GNUNET_SCHEDULER_add_at (cc->create_at, &send_create, cc);
    break;
 
  case CADET_CONNECTION_SENDING_CREATE:
    /* Should not be possible to be called in this state. */
    GNUNET_assert (0);
    break;
 
  case CADET_CONNECTION_SENT:
    /* Retry a bit later... */
    cc->task = GNUNET_SCHEDULER_add_at (cc->create_at, &send_create, cc);
    break;
 
  case CADET_CONNECTION_CREATE_RECEIVED:
    /* We got the 'CREATE' (incoming connection), should send the CREATE_ACK */
    cc->metrics.age = GNUNET_TIME_absolute_get ();
    cc->task =
      GNUNET_SCHEDULER_add_at (cc->create_ack_at, &send_create_ack, cc);
    break;
 
  case CADET_CONNECTION_READY:
    if ((NULL == cc->keepalive_qe) && (GNUNET_YES == cc->mqm_ready) &&
        (NULL == cc->task))
    {
      LOG (GNUNET_ERROR_TYPE_DEBUG,
           "Scheduling keepalive for %s in %s\n",
           GCC_2s (cc),
           GNUNET_STRINGS_relative_time_to_string (keepalive_period,
                                                   GNUNET_YES));
      cc->task =
        GNUNET_SCHEDULER_add_delayed (keepalive_period, &send_keepalive, cc);
    }
    break;
  }
}
 
 
static struct CadetConnection *
connection_create (struct CadetPeer *destination,
                   struct CadetPeerPath *path,
                   unsigned int off,
                   struct CadetTConnection *ct,
                   const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid,
                   enum CadetConnectionState init_state,
                   GCC_ReadyCallback ready_cb,
                   void *ready_cb_cls)
{
  struct CadetConnection *cc;
  struct CadetPeer *first_hop;
 
  cc = GNUNET_new (struct CadetConnection);
  cc->state = init_state;
  cc->ct = ct;
  cc->destination = destination; /* xrs,t3ss,lurchi*/
  cc->cid = *cid;
  cc->retry_delay =
    GNUNET_TIME_relative_multiply (INITIAL_CONNECTION_CREATE_RETRY_DELAY, off);
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONTAINER_multishortmap_put (
                   connections,
                   &GCC_get_id (cc)->connection_of_tunnel,
                   cc,
                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
  cc->ready_cb = ready_cb;
  cc->ready_cb_cls = ready_cb_cls;
  cc->path = path;
  cc->off = off;
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Creating %s using path %s (offset: %u)\n",
       GCC_2s (cc),
       GCPP_2s (path),
       off);
  GCPP_add_connection (path, off, cc);
  for (unsigned int i = 0; i < off; i++)
    GCP_add_connection (GCPP_get_peer_at_offset (path, i), cc);
  first_hop = GCPP_get_peer_at_offset (path, 0);
  cc->mq_man = GCP_request_mq (first_hop, &manage_first_hop_mq, cc);
  return cc;
}
 
 
struct CadetConnection *
GCC_create_inbound (struct CadetPeer *destination,
                    struct CadetPeerPath *path,
                    struct CadetTConnection *ct,
                    const struct GNUNET_CADET_ConnectionTunnelIdentifier *cid,
                    GCC_ReadyCallback ready_cb,
                    void *ready_cb_cls)
{
  struct CadetConnection *cc;
  unsigned int off;
 
  off = GCPP_find_peer (path, destination);
  GNUNET_assert (UINT_MAX != off);
  cc = GCPP_get_connection (path, destination, off);
  if (NULL != cc)
  {
    int cmp;
 
    cmp = GNUNET_memcmp (cid, &cc->cid);
    if (0 == cmp)
    {
      /* Two peers picked the SAME random connection identifier at the
         same time for the same path? Must be malicious.  Drop
         connection (existing and inbound), even if it is the only
         one. */
      GNUNET_break_op (0);
      GCT_connection_lost (cc->ct);
      GCC_destroy_without_tunnel (cc);
      return NULL;
    }
    if (0 < cmp)
    {
      /* drop existing */
      LOG (GNUNET_ERROR_TYPE_DEBUG,
           "Got two connections on %s, dropping my existing %s\n",
           GCPP_2s (path),
           GCC_2s (cc));
      GCT_connection_lost (cc->ct);
      GCC_destroy_without_tunnel (cc);
    }
    else
    {
      /* keep existing */
      LOG (GNUNET_ERROR_TYPE_DEBUG,
           "Got two connections on %s, keeping my existing %s\n",
           GCPP_2s (path),
           GCC_2s (cc));
      return NULL;
    }
  }
 
  return connection_create (destination,
                            path,
                            off,
                            ct,
                            cid,
                            CADET_CONNECTION_CREATE_RECEIVED,
                            ready_cb,
                            ready_cb_cls);
}
 
 
struct CadetConnection *
GCC_create (struct CadetPeer *destination,
            struct CadetPeerPath *path,
            unsigned int off,
            struct CadetTConnection *ct,
            GCC_ReadyCallback ready_cb,
            void *ready_cb_cls)
{
  struct GNUNET_CADET_ConnectionTunnelIdentifier cid;
 
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_NONCE, &cid, sizeof(cid));
  return connection_create (destination,
                            path,
                            off,
                            ct,
                            &cid,
                            CADET_CONNECTION_NEW,
                            ready_cb,
                            ready_cb_cls);
}
 
 
void
GCC_transmit (struct CadetConnection *cc, struct GNUNET_MQ_Envelope *env)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Scheduling message for transmission on %s\n",
       GCC_2s (cc));
  GNUNET_assert (GNUNET_YES == cc->mqm_ready);
  GNUNET_assert (CADET_CONNECTION_READY == cc->state);
  cc->metrics.last_use = GNUNET_TIME_absolute_get ();
  cc->mqm_ready = GNUNET_NO;
  if (NULL != cc->task)
  {
    GNUNET_SCHEDULER_cancel (cc->task);
    cc->task = NULL;
  }
  GCP_send (cc->mq_man, env);
}
 
 
struct CadetPeerPath *
GCC_get_path (struct CadetConnection *cc, unsigned int *off)
{
  *off = cc->off;
  return cc->path;
}
 
 
const struct GNUNET_CADET_ConnectionTunnelIdentifier *
GCC_get_id (struct CadetConnection *cc)
{
  return &cc->cid;
}
 
 
const char *
GCC_2s (const struct CadetConnection *cc)
{
  static char buf[128];
 
  if (NULL == cc)
    return "Connection(NULL)";
 
  if (NULL != cc->ct)
  {
    GNUNET_snprintf (buf,
                     sizeof(buf),
                     "Connection %s (%s)",
                     GNUNET_sh2s (&cc->cid.connection_of_tunnel),
                     GCT_2s (cc->ct->t));
    return buf;
  }
  GNUNET_snprintf (buf,
                   sizeof(buf),
                   "Connection %s",
                   GNUNET_sh2s (&cc->cid.connection_of_tunnel));
  return buf;
}
 
 
#define LOG2(level, ...) \
        GNUNET_log_from_nocheck (level, "cadet-con", __VA_ARGS__)
 
 
void
GCC_debug (struct CadetConnection *cc, enum GNUNET_ErrorType level)
{
#if ! defined(GNUNET_CULL_LOGGING)
  int do_log;
 
  do_log = GNUNET_get_log_call_status (level & (~GNUNET_ERROR_TYPE_BULK),
                                       "cadet-con",
                                       __FILE__,
                                       __FUNCTION__,
                                       __LINE__);
  if (0 == do_log)
    return;
  if (NULL == cc)
  {
    LOG2 (level, "Connection (NULL)\n");
    return;
  }
  LOG2 (level,
        "%s to %s via path %s in state %d is %s\n",
        GCC_2s (cc),
        GCP_2s (cc->destination),
        GCPP_2s (cc->path),
        cc->state,
        (GNUNET_YES == cc->mqm_ready) ? "ready" : "busy");
#endif
}
 
 
/* end of gnunet-service-cadet_connection.c */