gnunet-communicator-tcp.c

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/*
     This file is part of GNUnet
     Copyright (C) 2010-2014, 2018, 2019 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_util_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_signatures.h"
#include "gnunet_constants.h"
#include "gnunet_nt_lib.h"
#include "gnunet_nat_service.h"
#include "gnunet_statistics_service.h"
#include "gnunet_transport_communication_service.h"

#define ADDRESS_VALIDITY_PERIOD \
  GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 4)

#define DEFAULT_MAX_QUEUE_LENGTH 8

#define BUF_SIZE (2 * 64 * 1024 + sizeof(struct TCPBox))

#define DEFAULT_REKEY_INTERVAL GNUNET_TIME_UNIT_DAYS

#define PROTO_QUEUE_TIMEOUT GNUNET_TIME_UNIT_MINUTES

#define REKEY_MAX_BYTES (1024LLU * 1024 * 1024 * 4LLU)

#define INITIAL_KX_SIZE                           \
  (sizeof(struct GNUNET_CRYPTO_EcdhePublicKey)   \
   + sizeof(struct TCPConfirmation))


#define COMMUNICATOR_ADDRESS_PREFIX "tcp"

#define COMMUNICATOR_CONFIG_SECTION "communicator-tcp"

GNUNET_NETWORK_STRUCT_BEGIN


struct TcpHandshakeSignature
{
  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;

  struct GNUNET_PeerIdentity sender;

  struct GNUNET_PeerIdentity receiver;

  struct GNUNET_CRYPTO_EcdhePublicKey ephemeral;

  struct GNUNET_TIME_AbsoluteNBO monotonic_time;
};


struct TCPConfirmation
{
  struct GNUNET_PeerIdentity sender;

  struct GNUNET_CRYPTO_EddsaSignature sender_sig;

  struct GNUNET_TIME_AbsoluteNBO monotonic_time;
};


struct TCPBox
{
  struct GNUNET_MessageHeader header;

  struct GNUNET_ShortHashCode hmac;

  /* followed by as may bytes of payload as indicated in @e header,
     excluding the TCPBox itself! */
};


struct TCPRekey
{
  struct GNUNET_MessageHeader header;

  struct GNUNET_ShortHashCode hmac;

  struct GNUNET_CRYPTO_EcdhePublicKey ephemeral;

  struct GNUNET_CRYPTO_EddsaSignature sender_sig;

  struct GNUNET_TIME_AbsoluteNBO monotonic_time;
};


struct TCPFinish
{
  struct GNUNET_MessageHeader header;

  struct GNUNET_ShortHashCode hmac;
};


GNUNET_NETWORK_STRUCT_END


struct Queue
{
  struct GNUNET_PeerIdentity target;

  struct GNUNET_NETWORK_Handle *sock;

  gcry_cipher_hd_t in_cipher;

  gcry_cipher_hd_t out_cipher;

  struct GNUNET_HashCode in_hmac;

  struct GNUNET_HashCode out_hmac;

  struct GNUNET_CRYPTO_EcdhePrivateKey ephemeral;

  struct GNUNET_SCHEDULER_Task *read_task;

  struct GNUNET_SCHEDULER_Task *write_task;

  struct sockaddr *address;

  uint64_t rekey_left_bytes;

  struct GNUNET_TIME_Absolute rekey_time;

  socklen_t address_len;

  struct GNUNET_MQ_Handle *mq;

  struct GNUNET_TRANSPORT_QueueHandle *qh;

  unsigned long long bytes_in_queue;

  char cread_buf[BUF_SIZE];

  char cwrite_buf[BUF_SIZE];

  char pread_buf[UINT16_MAX + 1 + sizeof(struct TCPBox)];

  char pwrite_buf[UINT16_MAX + 1 + sizeof(struct TCPBox)];

  size_t cread_off;

  size_t cwrite_off;

  size_t pread_off;

  size_t pwrite_off;

  struct GNUNET_TIME_Absolute timeout;

  unsigned int backpressure;

  enum GNUNET_NetworkType nt;

  int mq_awaits_continue;

  int finishing;

  int destroyed;

  int rekeyed;
};


struct ProtoQueue
{
  struct ProtoQueue *next;

  struct ProtoQueue *prev;

  struct GNUNET_NETWORK_Handle *sock;

  struct GNUNET_SCHEDULER_Task *read_task;

  struct sockaddr *address;

  socklen_t address_len;

  struct GNUNET_TIME_Absolute timeout;

  char ibuf[INITIAL_KX_SIZE];

  size_t ibuf_off;
};


static struct GNUNET_SCHEDULER_Task *listen_task;

static unsigned long long max_queue_length;

static struct GNUNET_STATISTICS_Handle *stats;

static struct GNUNET_TRANSPORT_CommunicatorHandle *ch;

static struct GNUNET_CONTAINER_MultiPeerMap *queue_map;

static struct GNUNET_NETWORK_Handle *listen_sock;

static struct GNUNET_PeerIdentity my_identity;

static struct GNUNET_TIME_Relative rekey_interval;

static struct GNUNET_CRYPTO_EddsaPrivateKey *my_private_key;

static const struct GNUNET_CONFIGURATION_Handle *cfg;

static struct GNUNET_NT_InterfaceScanner *is;

static struct GNUNET_NAT_Handle *nat;

static struct ProtoQueue *proto_head;

static struct ProtoQueue *proto_tail;


static void
listen_cb (void *cls);


static void
queue_destroy (struct Queue *queue)
{
  struct GNUNET_MQ_Handle *mq;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Disconnecting queue for peer `%s'\n",
              GNUNET_i2s (&queue->target));
  if (NULL != (mq = queue->mq))
  {
    queue->mq = NULL;
    GNUNET_MQ_destroy (mq);
  }
  if (NULL != queue->qh)
  {
    GNUNET_TRANSPORT_communicator_mq_del (queue->qh);
    queue->qh = NULL;
  }
  GNUNET_assert (
    GNUNET_YES ==
    GNUNET_CONTAINER_multipeermap_remove (queue_map, &queue->target, queue));
  GNUNET_STATISTICS_set (stats,
                         "# queues active",
                         GNUNET_CONTAINER_multipeermap_size (queue_map),
                         GNUNET_NO);
  if (NULL != queue->read_task)
  {
    GNUNET_SCHEDULER_cancel (queue->read_task);
    queue->read_task = NULL;
  }
  if (NULL != queue->write_task)
  {
    GNUNET_SCHEDULER_cancel (queue->write_task);
    queue->write_task = NULL;
  }
  GNUNET_NETWORK_socket_close (queue->sock);
  gcry_cipher_close (queue->in_cipher);
  gcry_cipher_close (queue->out_cipher);
  GNUNET_free (queue->address);
  if (0 != queue->backpressure)
    queue->destroyed = GNUNET_YES;
  else
    GNUNET_free (queue);
  if (NULL == listen_task)
    listen_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                                 listen_sock,
                                                 &listen_cb,
                                                 NULL);
}


static void
calculate_hmac (struct GNUNET_HashCode *hmac_secret,
                const void *buf,
                size_t buf_size,
                struct GNUNET_ShortHashCode *smac)
{
  struct GNUNET_HashCode mac;

  GNUNET_CRYPTO_hmac_raw (hmac_secret,
                          sizeof(struct GNUNET_HashCode),
                          buf,
                          buf_size,
                          &mac);
  /* truncate to `struct GNUNET_ShortHashCode` */
  memcpy (smac, &mac, sizeof(struct GNUNET_ShortHashCode));
  /* ratchet hmac key */
  GNUNET_CRYPTO_hash (hmac_secret,
                      sizeof(struct GNUNET_HashCode),
                      hmac_secret);
}


static void
queue_finish (struct Queue *queue)
{
  struct TCPFinish fin;

  memset (&fin, 0, sizeof(fin));
  fin.header.size = htons (sizeof(fin));
  fin.header.type = htons (GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_FINISH);
  calculate_hmac (&queue->out_hmac, &fin, sizeof(fin), &fin.hmac);
  /* if there is any message left in pwrite_buf, we
     overwrite it (possibly dropping the last message
     from CORE hard here) */
  memcpy (queue->pwrite_buf, &fin, sizeof(fin));
  queue->pwrite_off = sizeof(fin);
  /* This flag will ensure that #queue_write() no longer
     notifies CORE about the possibility of sending
     more data, and that #queue_write() will call
  #queue_destroy() once the @c fin was fully written. */
  queue->finishing = GNUNET_YES;
}


static void
reschedule_queue_timeout (struct Queue *queue)
{
  queue->timeout =
    GNUNET_TIME_relative_to_absolute (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT);
}


static void
queue_read (void *cls);


static void
core_read_finished_cb (void *cls, int success)
{
  struct Queue *queue = cls;
  if (GNUNET_OK != success)
    GNUNET_STATISTICS_update (stats,
                              "# messages lost in communicator API towards CORE",
                              1,
                              GNUNET_NO);
  queue->backpressure--;
  /* handle deferred queue destruction */
  if ((queue->destroyed) && (0 == queue->backpressure))
  {
    GNUNET_free (queue);
    return;
  }
  reschedule_queue_timeout (queue);
  /* possibly unchoke reading, now that CORE made progress */
  if (NULL == queue->read_task)
    queue->read_task =
      GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_absolute_get_remaining (
                                       queue->timeout),
                                     queue->sock,
                                     &queue_read,
                                     queue);
}


static void
pass_plaintext_to_core (struct Queue *queue,
                        const void *plaintext,
                        size_t plaintext_len)
{
  const struct GNUNET_MessageHeader *hdr = plaintext;
  int ret;

  if (ntohs (hdr->size) != plaintext_len)
  {
    /* NOTE: If we ever allow multiple CORE messages in one
       BOX, this will have to change! */
    GNUNET_break (0);
    return;
  }
  ret = GNUNET_TRANSPORT_communicator_receive (ch,
                                               &queue->target,
                                               hdr,
                                               ADDRESS_VALIDITY_PERIOD,
                                               &core_read_finished_cb,
                                               queue);
  if (GNUNET_OK == ret)
    queue->backpressure++;
  GNUNET_break (GNUNET_NO != ret);  /* backpressure not working!? */
  if (GNUNET_SYSERR == ret)
    GNUNET_STATISTICS_update (stats,
                              "# bytes lost due to CORE not running",
                              plaintext_len,
                              GNUNET_NO);
}


static void
setup_cipher (const struct GNUNET_HashCode *dh,
              const struct GNUNET_PeerIdentity *pid,
              gcry_cipher_hd_t *cipher,
              struct GNUNET_HashCode *hmac_key)
{
  char key[256 / 8];
  char ctr[128 / 8];

  gcry_cipher_open (cipher,
                    GCRY_CIPHER_AES256 /* low level: go for speed */,
                    GCRY_CIPHER_MODE_CTR,
                    0 /* flags */);
  GNUNET_assert (GNUNET_YES == GNUNET_CRYPTO_kdf (key,
                                                  sizeof(key),
                                                  "TCP-key",
                                                  strlen ("TCP-key"),
                                                  dh,
                                                  sizeof(*dh),
                                                  pid,
                                                  sizeof(*pid),
                                                  NULL,
                                                  0));
  gcry_cipher_setkey (*cipher, key, sizeof(key));
  GNUNET_assert (GNUNET_YES == GNUNET_CRYPTO_kdf (ctr,
                                                  sizeof(ctr),
                                                  "TCP-ctr",
                                                  strlen ("TCP-ctr"),
                                                  dh,
                                                  sizeof(*dh),
                                                  pid,
                                                  sizeof(*pid),
                                                  NULL,
                                                  0));
  gcry_cipher_setctr (*cipher, ctr, sizeof(ctr));
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CRYPTO_kdf (hmac_key,
                                    sizeof(struct GNUNET_HashCode),
                                    "TCP-hmac",
                                    strlen ("TCP-hmac"),
                                    dh,
                                    sizeof(*dh),
                                    pid,
                                    sizeof(*pid),
                                    NULL,
                                    0));
}


static void
setup_in_cipher (const struct GNUNET_CRYPTO_EcdhePublicKey *ephemeral,
                 struct Queue *queue)
{
  struct GNUNET_HashCode dh;

  GNUNET_CRYPTO_eddsa_ecdh (my_private_key, ephemeral, &dh);
  setup_cipher (&dh, &my_identity, &queue->in_cipher, &queue->in_hmac);
}


static void
do_rekey (struct Queue *queue, const struct TCPRekey *rekey)
{
  struct TcpHandshakeSignature thp;
  thp.purpose.purpose = htonl (GNUNET_SIGNATURE_COMMUNICATOR_TCP_REKEY);
  thp.purpose.size = htonl (sizeof(thp));
  thp.sender = queue->target;
  thp.receiver = my_identity;
  thp.ephemeral = rekey->ephemeral;
  thp.monotonic_time = rekey->monotonic_time;
  /* FIXME: check monotonic time is monotonic... */
  if (GNUNET_OK !=
      GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_COMMUNICATOR_TCP_REKEY,
                                  &thp,
                                  &rekey->sender_sig,
                                  &queue->target.public_key))
  {
    GNUNET_break (0);
    queue_finish (queue);
    return;
  }
  gcry_cipher_close (queue->in_cipher);
  queue->rekeyed = GNUNET_YES;
  setup_in_cipher (&rekey->ephemeral, queue);
}


static size_t
try_handle_plaintext (struct Queue *queue)
{
  const struct GNUNET_MessageHeader *hdr =
    (const struct GNUNET_MessageHeader *) queue->pread_buf;
  const struct TCPBox *box = (const struct TCPBox *) queue->pread_buf;
  const struct TCPRekey *rekey = (const struct TCPRekey *) queue->pread_buf;
  const struct TCPFinish *fin = (const struct TCPFinish *) queue->pread_buf;
  struct TCPRekey rekeyz;
  struct TCPFinish finz;
  struct GNUNET_ShortHashCode tmac;
  uint16_t type;
  size_t size = 0; /* make compiler happy */

  if (sizeof(*hdr) > queue->pread_off)
    return 0; /* not even a header */
  type = ntohs (hdr->type);
  switch (type)
  {
  case GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_BOX:
    /* Special case: header size excludes box itself! */
    if (ntohs (hdr->size) + sizeof(struct TCPBox) > queue->pread_off)
      return 0;
    calculate_hmac (&queue->in_hmac, &box[1], ntohs (hdr->size), &tmac);
    if (0 != memcmp (&tmac, &box->hmac, sizeof(tmac)))
    {
      GNUNET_break_op (0);
      queue_finish (queue);
      return 0;
    }
    pass_plaintext_to_core (queue, (const void *) &box[1], ntohs (hdr->size));
    size = ntohs (hdr->size) + sizeof(*box);
    break;

  case GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_REKEY:
    if (sizeof(*rekey) > queue->pread_off)
      return 0;
    if (ntohs (hdr->size) != sizeof(*rekey))
    {
      GNUNET_break_op (0);
      queue_finish (queue);
      return 0;
    }
    rekeyz = *rekey;
    memset (&rekeyz.hmac, 0, sizeof(rekeyz.hmac));
    calculate_hmac (&queue->in_hmac, &rekeyz, sizeof(rekeyz), &tmac);
    if (0 != memcmp (&tmac, &rekey->hmac, sizeof(tmac)))
    {
      GNUNET_break_op (0);
      queue_finish (queue);
      return 0;
    }
    do_rekey (queue, rekey);
    size = ntohs (hdr->size);
    break;

  case GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_FINISH:
    if (sizeof(*fin) > queue->pread_off)
      return 0;
    if (ntohs (hdr->size) != sizeof(*fin))
    {
      GNUNET_break_op (0);
      queue_finish (queue);
      return 0;
    }
    finz = *fin;
    memset (&finz.hmac, 0, sizeof(finz.hmac));
    calculate_hmac (&queue->in_hmac, &rekeyz, sizeof(rekeyz), &tmac);
    if (0 != memcmp (&tmac, &fin->hmac, sizeof(tmac)))
    {
      GNUNET_break_op (0);
      queue_finish (queue);
      return 0;
    }
    /* handle FINISH by destroying queue */
    queue_destroy (queue);
    break;

  default:
    GNUNET_break_op (0);
    queue_finish (queue);
    return 0;
  }
  GNUNET_assert (0 != size);
  return size;
}


static void
queue_read (void *cls)
{
  struct Queue *queue = cls;
  struct GNUNET_TIME_Relative left;
  ssize_t rcvd;

  queue->read_task = NULL;
  rcvd = GNUNET_NETWORK_socket_recv (queue->sock,
                                     &queue->cread_buf[queue->cread_off],
                                     BUF_SIZE - queue->cread_off);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received %lu bytes from TCP queue\n", rcvd);
  if (-1 == rcvd)
  {
    if ((EAGAIN != errno) && (EINTR != errno))
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_DEBUG, "recv");
      queue_finish (queue);
      return;
    }
    /* try again */
    left = GNUNET_TIME_absolute_get_remaining (queue->timeout);
    queue->read_task =
      GNUNET_SCHEDULER_add_read_net (left, queue->sock, &queue_read, queue);
    return;
  }
  if (0 != rcvd)
    reschedule_queue_timeout (queue);
  queue->cread_off += rcvd;
  while ((queue->pread_off < sizeof(queue->pread_buf)) &&
         (queue->cread_off > 0))
  {
    size_t max = GNUNET_MIN (sizeof(queue->pread_buf) - queue->pread_off,
                             queue->cread_off);
    size_t done;
    size_t total;
    size_t old_pread_off = queue->pread_off;

    GNUNET_assert (0 ==
                   gcry_cipher_decrypt (queue->in_cipher,
                                        &queue->pread_buf[queue->pread_off],
                                        max,
                                        queue->cread_buf,
                                        max));
    queue->pread_off += max;
    total = 0;
    while (0 != (done = try_handle_plaintext (queue)))
    {
      /* 'done' bytes of plaintext were used, shift buffer */
      GNUNET_assert (done <= queue->pread_off);
      /* NOTE: this memmove() could possibly sometimes be
         avoided if we pass 'total' into try_handle_plaintext()
         and use it at an offset into the buffer there! */
      memmove (queue->pread_buf,
               &queue->pread_buf[done],
               queue->pread_off - done);
      queue->pread_off -= done;
      total += done;
      /* The last plaintext was a rekey, abort for now */
      if (GNUNET_YES == queue->rekeyed)
        break;
    }
    /* when we encounter a rekey message, the decryption above uses the
       wrong key for everything after the rekey; in that case, we have
       to re-do the decryption at 'total' instead of at 'max'.
       However, we have to take into account that the plaintext buffer may have
       already contained data and not jumpt too far ahead in the ciphertext.
       If there is no rekey and the last message is incomplete (max > total),
       it is safe to keep the decryption so we shift by 'max' */if (GNUNET_YES == queue->rekeyed)
    {
      max = total - old_pread_off;
      queue->rekeyed = GNUNET_NO;
      queue->pread_off = 0;
    }
    memmove (queue->cread_buf, &queue->cread_buf[max], queue->cread_off - max);
    queue->cread_off -= max;
  }
  if (BUF_SIZE == queue->cread_off)
    return; /* buffer full, suspend reading */
  left = GNUNET_TIME_absolute_get_remaining (queue->timeout);
  if (0 != left.rel_value_us)
  {
    if (max_queue_length > queue->backpressure)
    {
      /* continue reading */
      left = GNUNET_TIME_absolute_get_remaining (queue->timeout);
      queue->read_task =
        GNUNET_SCHEDULER_add_read_net (left, queue->sock, &queue_read, queue);
    }
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Queue %p was idle for %s, disconnecting\n",
              queue,
              GNUNET_STRINGS_relative_time_to_string (
                GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
                GNUNET_YES));
  queue_finish (queue);
}


static struct sockaddr *
tcp_address_to_sockaddr (const char *bindto, socklen_t *sock_len)
{
  struct sockaddr *in;
  unsigned int port;
  char dummy[2];
  char *colon;
  char *cp;

  if (1 == sscanf (bindto, "%u%1s", &port, dummy))
  {
    /* interpreting value as just a PORT number */
    if (port > UINT16_MAX)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "BINDTO specification `%s' invalid: value too large for port\n",
                  bindto);
      return NULL;
    }
    if ((GNUNET_NO == GNUNET_NETWORK_test_pf (PF_INET6)) ||
        (GNUNET_YES ==
         GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                               COMMUNICATOR_CONFIG_SECTION,
                                               "DISABLE_V6")))
    {
      struct sockaddr_in *i4;

      i4 = GNUNET_malloc (sizeof(struct sockaddr_in));
      i4->sin_family = AF_INET;
      i4->sin_port = htons ((uint16_t) port);
#if HAVE_SOCKADDR_IN_SIN_LEN
      i4->sin_len = sizeof(sizeof(struct sockaddr_in));
#endif
      *sock_len = sizeof(struct sockaddr_in);
      in = (struct sockaddr *) i4;
    }
    else
    {
      struct sockaddr_in6 *i6;

      i6 = GNUNET_malloc (sizeof(struct sockaddr_in6));
      i6->sin6_family = AF_INET6;
      i6->sin6_port = htons ((uint16_t) port);
#if HAVE_SOCKADDR_IN_SIN_LEN
      i6->sin6_len = sizeof(sizeof(struct sockaddr_in6));
#endif
      *sock_len = sizeof(struct sockaddr_in6);
      in = (struct sockaddr *) i6;
    }
    return in;
  }
  cp = GNUNET_strdup (bindto);
  colon = strrchr (cp, ':');
  if (NULL != colon)
  {
    /* interpet value after colon as port */
    *colon = '\0';
    colon++;
    if (1 == sscanf (colon, "%u%1s", &port, dummy))
    {
      /* interpreting value as just a PORT number */
      if (port > UINT16_MAX)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                    "BINDTO specification `%s' invalid: value too large for port\n",
                    bindto);
        GNUNET_free (cp);
        return NULL;
      }
    }
    else
    {
      GNUNET_log (
        GNUNET_ERROR_TYPE_ERROR,
        "BINDTO specification `%s' invalid: last ':' not followed by number\n",
        bindto);
      GNUNET_free (cp);
      return NULL;
    }
  }
  else
  {
    /* interpret missing port as 0, aka pick any free one */
    port = 0;
  }
  {
    /* try IPv4 */
    struct sockaddr_in v4;

    if (1 == inet_pton (AF_INET, cp, &v4.sin_addr))
    {
      v4.sin_family = AF_INET;
      v4.sin_port = htons ((uint16_t) port);
#if HAVE_SOCKADDR_IN_SIN_LEN
      v4.sin_len = sizeof(struct sockaddr_in);
#endif
      in = GNUNET_memdup (&v4, sizeof(v4));
      *sock_len = sizeof(v4);
      GNUNET_free (cp);
      return in;
    }
  }
  {
    /* try IPv6 */
    struct sockaddr_in6 v6;
    const char *start;

    start = cp;
    if (('[' == *cp) && (']' == cp[strlen (cp) - 1]))
    {
      start++;   /* skip over '[' */
      cp[strlen (cp) - 1] = '\0';  /* eat ']' */
    }
    if (1 == inet_pton (AF_INET6, start, &v6.sin6_addr))
    {
      v6.sin6_family = AF_INET6;
      v6.sin6_port = htons ((uint16_t) port);
#if HAVE_SOCKADDR_IN_SIN_LEN
      v6.sin6_len = sizeof(sizeof(struct sockaddr_in6));
#endif
      in = GNUNET_memdup (&v6, sizeof(v6));
      *sock_len = sizeof(v6);
      GNUNET_free (cp);
      return in;
    }
  }
  /* #5528 FIXME (feature!): maybe also try getnameinfo()? */
  GNUNET_free (cp);
  return NULL;
}


static void
setup_out_cipher (struct Queue *queue)
{
  struct GNUNET_HashCode dh;

  GNUNET_CRYPTO_ecdh_eddsa (&queue->ephemeral, &queue->target.public_key, &dh);
  /* we don't need the private key anymore, drop it! */
  memset (&queue->ephemeral, 0, sizeof(queue->ephemeral));
  setup_cipher (&dh, &queue->target, &queue->out_cipher, &queue->out_hmac);
  queue->rekey_time = GNUNET_TIME_relative_to_absolute (rekey_interval);
  queue->rekey_left_bytes =
    GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK, REKEY_MAX_BYTES);
}


static void
inject_rekey (struct Queue *queue)
{
  struct TCPRekey rekey;
  struct TcpHandshakeSignature thp;

  GNUNET_assert (0 == queue->pwrite_off);
  memset (&rekey, 0, sizeof(rekey));
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CRYPTO_ecdhe_key_create2 (&queue->ephemeral));
  rekey.header.type = ntohs (GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_REKEY);
  rekey.header.size = ntohs (sizeof(rekey));
  GNUNET_CRYPTO_ecdhe_key_get_public (&queue->ephemeral, &rekey.ephemeral);
  rekey.monotonic_time =
    GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get_monotonic (cfg));
  thp.purpose.purpose = htonl (GNUNET_SIGNATURE_COMMUNICATOR_TCP_REKEY);
  thp.purpose.size = htonl (sizeof(thp));
  thp.sender = my_identity;
  thp.receiver = queue->target;
  thp.ephemeral = rekey.ephemeral;
  thp.monotonic_time = rekey.monotonic_time;
  GNUNET_CRYPTO_eddsa_sign (my_private_key,
                            &thp,
                            &rekey.sender_sig);
  calculate_hmac (&queue->out_hmac, &rekey, sizeof(rekey), &rekey.hmac);
  /* Encrypt rekey message with 'old' cipher */
  GNUNET_assert (0 ==
                 gcry_cipher_encrypt (queue->out_cipher,
                                      &queue->cwrite_buf[queue->cwrite_off],
                                      sizeof(rekey),
                                      &rekey,
                                      sizeof(rekey)));
  queue->cwrite_off += sizeof(rekey);
  /* Setup new cipher for successive messages */
  gcry_cipher_close (queue->out_cipher);
  setup_out_cipher (queue);
}


static void
queue_write (void *cls)
{
  struct Queue *queue = cls;
  ssize_t sent;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "In queue write\n");
  queue->write_task = NULL;
  if (0 != queue->cwrite_off)
  {
    sent = GNUNET_NETWORK_socket_send (queue->sock,
                                       queue->cwrite_buf,
                                       queue->cwrite_off);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Sent %lu bytes to TCP queue\n", sent);
    if ((-1 == sent) && (EAGAIN != errno) && (EINTR != errno))
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING, "send");
      queue_destroy (queue);
      return;
    }
    if (sent > 0)
    {
      size_t usent = (size_t) sent;
      queue->cwrite_off -= usent;
      memmove (queue->cwrite_buf,
               &queue->cwrite_buf[usent],
               queue->cwrite_off);
      reschedule_queue_timeout (queue);
    }
  }
  /* can we encrypt more? (always encrypt full messages, needed
     such that #mq_cancel() can work!) */
  if ((0 < queue->rekey_left_bytes) &&
      (queue->pwrite_off > 0) &&
      (queue->cwrite_off + queue->pwrite_off <= BUF_SIZE))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Encrypting %lu bytes\n", queue->pwrite_off);
    GNUNET_assert (0 ==
                   gcry_cipher_encrypt (queue->out_cipher,
                                        &queue->cwrite_buf[queue->cwrite_off],
                                        queue->pwrite_off,
                                        queue->pwrite_buf,
                                        queue->pwrite_off));
    if (queue->rekey_left_bytes > queue->pwrite_off)
      queue->rekey_left_bytes -= queue->pwrite_off;
    else
      queue->rekey_left_bytes = 0;
    queue->cwrite_off += queue->pwrite_off;
    queue->pwrite_off = 0;
  }
  if ((0 == queue->pwrite_off) &&
      ((0 == queue->rekey_left_bytes) ||
       (0 ==
        GNUNET_TIME_absolute_get_remaining (queue->rekey_time).rel_value_us)))
  {
    inject_rekey (queue);
  }
  if ((0 == queue->pwrite_off) && (! queue->finishing) &&
      (GNUNET_YES == queue->mq_awaits_continue))
  {
    queue->mq_awaits_continue = GNUNET_NO;
    GNUNET_MQ_impl_send_continue (queue->mq);
  }
  /* did we just finish writing 'finish'? */
  if ((0 == queue->cwrite_off) && (GNUNET_YES == queue->finishing))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Finishing queue\n");
    queue_destroy (queue);
    return;
  }
  /* do we care to write more? */
  if ((0 < queue->cwrite_off) || (0 < queue->pwrite_off))
    queue->write_task =
      GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                      queue->sock,
                                      &queue_write,
                                      queue);
}


static void
mq_send (struct GNUNET_MQ_Handle *mq,
         const struct GNUNET_MessageHeader *msg,
         void *impl_state)
{
  struct Queue *queue = impl_state;
  uint16_t msize = ntohs (msg->size);
  struct TCPBox box;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "In MQ send. Queue finishing: %s; write task running: %s\n",
              (GNUNET_YES == queue->finishing) ? "yes" : "no",
              (NULL == queue->write_task) ? "yes" : "no");
  GNUNET_assert (mq == queue->mq);
  queue->mq_awaits_continue = GNUNET_YES;
  if (GNUNET_YES == queue->finishing)
    return; /* this queue is dying, drop msg */
  GNUNET_assert (0 == queue->pwrite_off);
  box.header.type = htons (GNUNET_MESSAGE_TYPE_COMMUNICATOR_TCP_BOX);
  box.header.size = htons (msize);
  calculate_hmac (&queue->out_hmac, msg, msize, &box.hmac);
  memcpy (&queue->pwrite_buf[queue->pwrite_off], &box, sizeof(box));
  queue->pwrite_off += sizeof(box);
  memcpy (&queue->pwrite_buf[queue->pwrite_off], msg, msize);
  queue->pwrite_off += msize;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "%lu bytes of plaintext to send\n", queue->pwrite_off);
  GNUNET_assert (NULL != queue->sock);
  if (NULL == queue->write_task)
    queue->write_task =
      GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                      queue->sock,
                                      &queue_write,
                                      queue);
}


static void
mq_destroy (struct GNUNET_MQ_Handle *mq, void *impl_state)
{
  struct Queue *queue = impl_state;

  if (mq == queue->mq)
  {
    queue->mq = NULL;
    queue_finish (queue);
  }
}


static void
mq_cancel (struct GNUNET_MQ_Handle *mq, void *impl_state)
{
  struct Queue *queue = impl_state;

  GNUNET_assert (0 != queue->pwrite_off);
  queue->pwrite_off = 0;
}


static void
mq_error (void *cls, enum GNUNET_MQ_Error error)
{
  struct Queue *queue = cls;

  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
              "MQ error in queue to %s: %d\n",
              GNUNET_i2s (&queue->target),
              (int) error);
  queue_finish (queue);
}


static void
boot_queue (struct Queue *queue, enum GNUNET_TRANSPORT_ConnectionStatus cs)
{
  queue->nt =
    GNUNET_NT_scanner_get_type (is, queue->address, queue->address_len);
  (void) GNUNET_CONTAINER_multipeermap_put (
    queue_map,
    &queue->target,
    queue,
    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
  GNUNET_STATISTICS_set (stats,
                         "# queues active",
                         GNUNET_CONTAINER_multipeermap_size (queue_map),
                         GNUNET_NO);
  queue->timeout =
    GNUNET_TIME_relative_to_absolute (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT);
  queue->mq = GNUNET_MQ_queue_for_callbacks (&mq_send,
                                             &mq_destroy,
                                             &mq_cancel,
                                             queue,
                                             NULL,
                                             &mq_error,
                                             queue);
  {
    char *foreign_addr;

    switch (queue->address->sa_family)
    {
    case AF_INET:
      GNUNET_asprintf (&foreign_addr,
                       "%s-%s",
                       COMMUNICATOR_ADDRESS_PREFIX,
                       GNUNET_a2s (queue->address, queue->address_len));
      break;

    case AF_INET6:
      GNUNET_asprintf (&foreign_addr,
                       "%s-%s",
                       COMMUNICATOR_ADDRESS_PREFIX,
                       GNUNET_a2s (queue->address, queue->address_len));
      break;

    default:
      GNUNET_assert (0);
    }
    queue->qh = GNUNET_TRANSPORT_communicator_mq_add (ch,
                                                      &queue->target,
                                                      foreign_addr,
                                                      0 /* no MTU */,
                                                      queue->nt,
                                                      cs,
                                                      queue->mq);
    GNUNET_free (foreign_addr);
  }
}


static void
transmit_kx (struct Queue *queue,
             const struct GNUNET_CRYPTO_EcdhePublicKey *epub)
{
  struct TcpHandshakeSignature ths;
  struct TCPConfirmation tc;

  memcpy (queue->cwrite_buf, epub, sizeof(*epub));
  queue->cwrite_off = sizeof(*epub);
  /* compute 'tc' and append in encrypted format to cwrite_buf */
  tc.sender = my_identity;
  tc.monotonic_time =
    GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get_monotonic (cfg));
  ths.purpose.purpose = htonl (GNUNET_SIGNATURE_COMMUNICATOR_TCP_HANDSHAKE);
  ths.purpose.size = htonl (sizeof(ths));
  ths.sender = my_identity;
  ths.receiver = queue->target;
  ths.ephemeral = *epub;
  ths.monotonic_time = tc.monotonic_time;
  GNUNET_CRYPTO_eddsa_sign (my_private_key,
                            &ths,
                            &tc.sender_sig);
  GNUNET_assert (0 ==
                 gcry_cipher_encrypt (queue->out_cipher,
                                      &queue->cwrite_buf[queue->cwrite_off],
                                      sizeof(tc),
                                      &tc,
                                      sizeof(tc)));
  queue->cwrite_off += sizeof(tc);
}


static void
start_initial_kx_out (struct Queue *queue)
{
  struct GNUNET_CRYPTO_EcdhePublicKey epub;

  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CRYPTO_ecdhe_key_create2 (&queue->ephemeral));
  GNUNET_CRYPTO_ecdhe_key_get_public (&queue->ephemeral, &epub);
  setup_out_cipher (queue);
  transmit_kx (queue, &epub);
}


static int
decrypt_and_check_tc (struct Queue *queue,
                      struct TCPConfirmation *tc,
                      char *ibuf)
{
  struct TcpHandshakeSignature ths;

  GNUNET_assert (
    0 ==
    gcry_cipher_decrypt (queue->in_cipher,
                         tc,
                         sizeof(*tc),
                         &ibuf[sizeof(struct GNUNET_CRYPTO_EcdhePublicKey)],
                         sizeof(*tc)));
  ths.purpose.purpose = htonl (GNUNET_SIGNATURE_COMMUNICATOR_TCP_HANDSHAKE);
  ths.purpose.size = htonl (sizeof(ths));
  ths.sender = tc->sender;
  ths.receiver = my_identity;
  memcpy (&ths.ephemeral, ibuf, sizeof(struct GNUNET_CRYPTO_EcdhePublicKey));
  ths.monotonic_time = tc->monotonic_time;
  /* FIXME: check monotonic time against previous mono times
     from this sender! */
  return GNUNET_CRYPTO_eddsa_verify (
    GNUNET_SIGNATURE_COMMUNICATOR_TCP_HANDSHAKE,
    &ths,
    &tc->sender_sig,
    &tc->sender.public_key);
}


static void
free_proto_queue (struct ProtoQueue *pq)
{
  GNUNET_NETWORK_socket_close (pq->sock);
  GNUNET_free (pq->address);
  GNUNET_CONTAINER_DLL_remove (proto_head, proto_tail, pq);
  GNUNET_free (pq);
}


static void
proto_read_kx (void *cls)
{
  struct ProtoQueue *pq = cls;
  ssize_t rcvd;
  struct GNUNET_TIME_Relative left;
  struct Queue *queue;
  struct TCPConfirmation tc;

  pq->read_task = NULL;
  left = GNUNET_TIME_absolute_get_remaining (pq->timeout);
  if (0 == left.rel_value_us)
  {
    free_proto_queue (pq);
    return;
  }
  rcvd = GNUNET_NETWORK_socket_recv (pq->sock,
                                     &pq->ibuf[pq->ibuf_off],
                                     sizeof(pq->ibuf) - pq->ibuf_off);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received %lu bytes for KX\n", rcvd);
  if (-1 == rcvd)
  {
    if ((EAGAIN != errno) && (EINTR != errno))
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_DEBUG, "recv");
      free_proto_queue (pq);
      return;
    }
    /* try again */
    pq->read_task =
      GNUNET_SCHEDULER_add_read_net (left, pq->sock, &proto_read_kx, pq);
    return;
  }
  pq->ibuf_off += rcvd;
  if (pq->ibuf_off > sizeof(pq->ibuf))
  {
    /* read more */
    pq->read_task =
      GNUNET_SCHEDULER_add_read_net (left, pq->sock, &proto_read_kx, pq);
    return;
  }
  /* we got all the data, let's find out who we are talking to! */
  queue = GNUNET_new (struct Queue);
  setup_in_cipher ((const struct GNUNET_CRYPTO_EcdhePublicKey *) pq->ibuf,
                   queue);
  if (GNUNET_OK != decrypt_and_check_tc (queue, &tc, pq->ibuf))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Invalid TCP KX received from %s\n",
                GNUNET_a2s (queue->address, queue->address_len));
    gcry_cipher_close (queue->in_cipher);
    GNUNET_free (queue);
    free_proto_queue (pq);
    return;
  }
  queue->address = pq->address; /* steals reference */
  queue->address_len = pq->address_len;
  queue->target = tc.sender;
  queue->sock = pq->sock;
  start_initial_kx_out (queue);
  boot_queue (queue, GNUNET_TRANSPORT_CS_INBOUND);
  queue->read_task =
    GNUNET_SCHEDULER_add_read_net (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
                                   queue->sock,
                                   &queue_read,
                                   queue);
  queue->write_task =
    GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                    queue->sock,
                                    &queue_write,
                                    queue);
  GNUNET_CONTAINER_DLL_remove (proto_head, proto_tail, pq);
  GNUNET_free (pq);
}


static void
listen_cb (void *cls)
{
  struct sockaddr_storage in;
  socklen_t addrlen;
  struct GNUNET_NETWORK_Handle *sock;
  struct ProtoQueue *pq;

  listen_task = NULL;
  GNUNET_assert (NULL != listen_sock);
  addrlen = sizeof(in);
  memset (&in, 0, sizeof(in));
  sock = GNUNET_NETWORK_socket_accept (listen_sock,
                                       (struct sockaddr*) &in,
                                       &addrlen);
  if ((NULL == sock) && ((EMFILE == errno) || (ENFILE == errno)))
    return; /* system limit reached, wait until connection goes down */
  listen_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                               listen_sock,
                                               &listen_cb,
                                               NULL);
  if ((NULL == sock) && ((EAGAIN == errno) || (ENOBUFS == errno)))
    return;
  if (NULL == sock)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING, "accept");
    return;
  }
  pq = GNUNET_new (struct ProtoQueue);
  pq->address_len = addrlen;
  pq->address = GNUNET_memdup (&in, addrlen);
  pq->timeout = GNUNET_TIME_relative_to_absolute (PROTO_QUEUE_TIMEOUT);
  pq->sock = sock;
  pq->read_task = GNUNET_SCHEDULER_add_read_net (PROTO_QUEUE_TIMEOUT,
                                                 pq->sock,
                                                 &proto_read_kx,
                                                 pq);
  GNUNET_CONTAINER_DLL_insert (proto_head, proto_tail, pq);
}


static void
queue_read_kx (void *cls)
{
  struct Queue *queue = cls;
  ssize_t rcvd;
  struct GNUNET_TIME_Relative left;
  struct TCPConfirmation tc;

  queue->read_task = NULL;
  left = GNUNET_TIME_absolute_get_remaining (queue->timeout);
  if (0 == left.rel_value_us)
  {
    queue_destroy (queue);
    return;
  }
  rcvd = GNUNET_NETWORK_socket_recv (queue->sock,
                                     &queue->cread_buf[queue->cread_off],
                                     BUF_SIZE - queue->cread_off);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received %lu bytes for KX\n", rcvd);
  if (-1 == rcvd)
  {
    if ((EAGAIN != errno) && (EINTR != errno))
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_DEBUG, "recv");
      queue_destroy (queue);
      return;
    }
    queue->read_task =
      GNUNET_SCHEDULER_add_read_net (left, queue->sock, &queue_read_kx, queue);
    return;
  }
  queue->cread_off += rcvd;
  if (queue->cread_off < INITIAL_KX_SIZE)
  {
    /* read more */
    queue->read_task =
      GNUNET_SCHEDULER_add_read_net (left, queue->sock, &queue_read_kx, queue);
    return;
  }
  /* we got all the data, let's find out who we are talking to! */
  setup_in_cipher ((const struct GNUNET_CRYPTO_EcdhePublicKey *)
                   queue->cread_buf,
                   queue);
  if (GNUNET_OK != decrypt_and_check_tc (queue, &tc, queue->cread_buf))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Invalid TCP KX received from %s\n",
                GNUNET_a2s (queue->address, queue->address_len));
    queue_destroy (queue);
    return;
  }
  if (0 !=
      memcmp (&tc.sender, &queue->target, sizeof(struct GNUNET_PeerIdentity)))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Invalid sender in TCP KX received from %s\n",
                GNUNET_a2s (queue->address, queue->address_len));
    queue_destroy (queue);
    return;
  }

  /* update queue timeout */
  reschedule_queue_timeout (queue);
  /* prepare to continue with regular read task immediately */
  memmove (queue->cread_buf,
           &queue->cread_buf[INITIAL_KX_SIZE],
           queue->cread_off - (INITIAL_KX_SIZE));
  queue->cread_off -= INITIAL_KX_SIZE;
  if (0 < queue->cread_off)
    queue->read_task = GNUNET_SCHEDULER_add_now (&queue_read, queue);
}


static int
mq_init (void *cls, const struct GNUNET_PeerIdentity *peer, const char *address)
{
  struct Queue *queue;
  const char *path;
  struct sockaddr *in;
  socklen_t in_len;
  struct GNUNET_NETWORK_Handle *sock;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Connecting to %s\n", address);
  if (0 != strncmp (address,
                    COMMUNICATOR_ADDRESS_PREFIX "-",
                    strlen (COMMUNICATOR_ADDRESS_PREFIX "-")))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  path = &address[strlen (COMMUNICATOR_ADDRESS_PREFIX "-")];
  in = tcp_address_to_sockaddr (path, &in_len);

  sock = GNUNET_NETWORK_socket_create (in->sa_family, SOCK_STREAM, IPPROTO_TCP);
  if (NULL == sock)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "socket(%d) failed: %s",
                in->sa_family,
                strerror (errno));
    GNUNET_free (in);
    return GNUNET_SYSERR;
  }
  if ((GNUNET_OK != GNUNET_NETWORK_socket_connect (sock, in, in_len)) &&
      (errno != EINPROGRESS))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "connect to `%s' failed: %s",
                address,
                strerror (errno));
    GNUNET_NETWORK_socket_close (sock);
    GNUNET_free (in);
    return GNUNET_SYSERR;
  }

  queue = GNUNET_new (struct Queue);
  queue->target = *peer;
  queue->address = in;
  queue->address_len = in_len;
  queue->sock = sock;
  boot_queue (queue, GNUNET_TRANSPORT_CS_OUTBOUND);
  // queue->mq_awaits_continue = GNUNET_YES;
  queue->read_task =
    GNUNET_SCHEDULER_add_read_net (GNUNET_CONSTANTS_IDLE_CONNECTION_TIMEOUT,
                                   queue->sock,
                                   &queue_read_kx,
                                   queue);
  start_initial_kx_out (queue);
  queue->write_task =
    GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                    queue->sock,
                                    &queue_write,
                                    queue);
  return GNUNET_OK;
}


static int
get_queue_delete_it (void *cls,
                     const struct GNUNET_PeerIdentity *target,
                     void *value)
{
  struct Queue *queue = value;

  (void) cls;
  (void) target;
  queue_destroy (queue);
  return GNUNET_OK;
}


static void
do_shutdown (void *cls)
{
  while (NULL != proto_head)
    free_proto_queue (proto_head);
  if (NULL != nat)
  {
    GNUNET_NAT_unregister (nat);
    nat = NULL;
  }
  if (NULL != listen_task)
  {
    GNUNET_SCHEDULER_cancel (listen_task);
    listen_task = NULL;
  }
  if (NULL != listen_sock)
  {
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (listen_sock));
    listen_sock = NULL;
  }
  GNUNET_CONTAINER_multipeermap_iterate (queue_map, &get_queue_delete_it, NULL);
  GNUNET_CONTAINER_multipeermap_destroy (queue_map);
  if (NULL != ch)
  {
    GNUNET_TRANSPORT_communicator_disconnect (ch);
    ch = NULL;
  }
  if (NULL != stats)
  {
    GNUNET_STATISTICS_destroy (stats, GNUNET_NO);
    stats = NULL;
  }
  if (NULL != my_private_key)
  {
    GNUNET_free (my_private_key);
    my_private_key = NULL;
  }
  if (NULL != is)
  {
    GNUNET_NT_scanner_done (is);
    is = NULL;
  }
}


static void
enc_notify_cb (void *cls,
               const struct GNUNET_PeerIdentity *sender,
               const struct GNUNET_MessageHeader *msg)
{
  (void) cls;
  (void) sender;
  (void) msg;
  GNUNET_break_op (0);
}


static void
nat_address_cb (void *cls,
                void **app_ctx,
                int add_remove,
                enum GNUNET_NAT_AddressClass ac,
                const struct sockaddr *addr,
                socklen_t addrlen)
{
  char *my_addr;
  struct GNUNET_TRANSPORT_AddressIdentifier *ai;

  if (GNUNET_YES == add_remove)
  {
    enum GNUNET_NetworkType nt;

    GNUNET_asprintf (&my_addr,
                     "%s-%s",
                     COMMUNICATOR_ADDRESS_PREFIX,
                     GNUNET_a2s (addr, addrlen));
    nt = GNUNET_NT_scanner_get_type (is, addr, addrlen);
    ai =
      GNUNET_TRANSPORT_communicator_address_add (ch,
                                                 my_addr,
                                                 nt,
                                                 GNUNET_TIME_UNIT_FOREVER_REL);
    GNUNET_free (my_addr);
    *app_ctx = ai;
  }
  else
  {
    ai = *app_ctx;
    GNUNET_TRANSPORT_communicator_address_remove (ai);
    *app_ctx = NULL;
  }
}


static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *c)
{
  char *bindto;
  struct sockaddr *in;
  socklen_t in_len;
  struct sockaddr_storage in_sto;
  socklen_t sto_len;

  (void) cls;
  cfg = c;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg,
                                             COMMUNICATOR_CONFIG_SECTION,
                                             "BINDTO",
                                             &bindto))
  {
    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                               COMMUNICATOR_CONFIG_SECTION,
                               "BINDTO");
    return;
  }
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (cfg,
                                             COMMUNICATOR_CONFIG_SECTION,
                                             "MAX_QUEUE_LENGTH",
                                             &max_queue_length))
    max_queue_length = DEFAULT_MAX_QUEUE_LENGTH;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_time (cfg,
                                           COMMUNICATOR_CONFIG_SECTION,
                                           "REKEY_INTERVAL",
                                           &rekey_interval))
    rekey_interval = DEFAULT_REKEY_INTERVAL;

  in = tcp_address_to_sockaddr (bindto, &in_len);
  if (NULL == in)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to setup TCP socket address with path `%s'\n",
                bindto);
    GNUNET_free (bindto);
    return;
  }
  listen_sock =
    GNUNET_NETWORK_socket_create (in->sa_family, SOCK_STREAM, IPPROTO_TCP);
  if (NULL == listen_sock)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "socket");
    GNUNET_free (in);
    GNUNET_free (bindto);
    return;
  }
  if (GNUNET_OK != GNUNET_NETWORK_socket_bind (listen_sock, in, in_len))
  {
    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR, "bind", bindto);
    GNUNET_NETWORK_socket_close (listen_sock);
    listen_sock = NULL;
    GNUNET_free (in);
    GNUNET_free (bindto);
    return;
  }
  if (GNUNET_OK !=
      GNUNET_NETWORK_socket_listen (listen_sock,
                                    5))
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
                         "listen");
    GNUNET_NETWORK_socket_close (listen_sock);
    listen_sock = NULL;
    GNUNET_free (in);
    GNUNET_free (bindto);
  }
  /* We might have bound to port 0, allowing the OS to figure it out;
     thus, get the real IN-address from the socket */
  sto_len = sizeof(in_sto);
  if (0 != getsockname (GNUNET_NETWORK_get_fd (listen_sock),
                        (struct sockaddr *) &in_sto,
                        &sto_len))
  {
    memcpy (&in_sto, in, in_len);
    sto_len = in_len;
  }
  GNUNET_free (in);
  GNUNET_free (bindto);
  in = (struct sockaddr *) &in_sto;
  in_len = sto_len;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Bound to `%s'\n",
              GNUNET_a2s ((const struct sockaddr *) &in_sto, sto_len));
  stats = GNUNET_STATISTICS_create ("C-TCP", cfg);
  GNUNET_SCHEDULER_add_shutdown (&do_shutdown, NULL);
  is = GNUNET_NT_scanner_init ();
  my_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (cfg);
  if (NULL == my_private_key)
  {
    GNUNET_log (
      GNUNET_ERROR_TYPE_ERROR,
      _ (
        "Transport service is lacking key configuration settings. Exiting.\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_CRYPTO_eddsa_key_get_public (my_private_key, &my_identity.public_key);
  /* start listening */
  listen_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                               listen_sock,
                                               &listen_cb,
                                               NULL);
  queue_map = GNUNET_CONTAINER_multipeermap_create (10, GNUNET_NO);
  ch = GNUNET_TRANSPORT_communicator_connect (cfg,
                                              COMMUNICATOR_CONFIG_SECTION,
                                              COMMUNICATOR_ADDRESS_PREFIX,
                                              GNUNET_TRANSPORT_CC_RELIABLE,
                                              &mq_init,
                                              NULL,
                                              &enc_notify_cb,
                                              NULL);
  if (NULL == ch)
  {
    GNUNET_break (0);
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  nat = GNUNET_NAT_register (cfg,
                             COMMUNICATOR_CONFIG_SECTION,
                             IPPROTO_TCP,
                             1 /* one address */,
                             (const struct sockaddr **) &in,
                             &in_len,
                             &nat_address_cb,
                             NULL /* FIXME: support reversal: #5529 */,
                             NULL /* closure */);
}


int
main (int argc, char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    GNUNET_GETOPT_OPTION_END
  };
  int ret;

  if (GNUNET_OK != GNUNET_STRINGS_get_utf8_args (argc, argv, &argc, &argv))
    return 2;

  ret = (GNUNET_OK == GNUNET_PROGRAM_run (argc,
                                          argv,
                                          "gnunet-communicator-tcp",
                                          _ ("GNUnet TCP communicator"),
                                          options,
                                          &run,
                                          NULL))
        ? 0
        : 1;
  GNUNET_free ((void *) argv);
  return ret;
}


/* end of gnunet-communicator-tcp.c */