tcp_connection_legacy.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2009-2013 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_resolver_service.h"


#define CONNECT_RETRY_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)



#define LOG_STRERROR(kind,syscall) GNUNET_log_from_strerror (kind, "util-connection", syscall)


struct GNUNET_CONNECTION_TransmitHandle
{

  GNUNET_CONNECTION_TransmitReadyNotify notify_ready;

  void *notify_ready_cls;

  struct GNUNET_CONNECTION_Handle *connection;

  struct GNUNET_TIME_Absolute transmit_timeout;

  struct GNUNET_SCHEDULER_Task * timeout_task;

  size_t notify_size;

};


struct AddressProbe
{

  struct AddressProbe *next;

  struct AddressProbe *prev;

  const struct sockaddr *addr;

  struct GNUNET_NETWORK_Handle *sock;

  struct GNUNET_CONNECTION_Handle *connection;

  socklen_t addrlen;

  struct GNUNET_SCHEDULER_Task * task;
};


struct GNUNET_CONNECTION_Handle
{

  const struct GNUNET_CONFIGURATION_Handle *cfg;

  struct AddressProbe *ap_head;

  struct AddressProbe *ap_tail;

  struct sockaddr *addr;

  char *hostname;

  struct GNUNET_NETWORK_Handle *sock;

  GNUNET_CONNECTION_Receiver receiver;

  void *receiver_cls;

  char *write_buffer;

  size_t write_buffer_size;

  size_t write_buffer_off;

  size_t write_buffer_pos;

  socklen_t addrlen;

  struct GNUNET_SCHEDULER_Task *read_task;

  struct GNUNET_SCHEDULER_Task *write_task;

  struct GNUNET_RESOLVER_RequestHandle *dns_active;

  struct GNUNET_CONNECTION_TransmitHandle nth;

  struct GNUNET_TIME_Absolute receive_timeout;

  size_t max;

  uint16_t port;

  int8_t persist;

  int8_t destroy_later;

  struct GNUNET_CONNECTION_Handle *proxy_handshake;

};


void
GNUNET_CONNECTION_persist_ (struct GNUNET_CONNECTION_Handle *connection)
{
  connection->persist = GNUNET_YES;
}


int
GNUNET_CONNECTION_disable_corking (struct GNUNET_CONNECTION_Handle *connection)
{
  return GNUNET_NETWORK_socket_disable_corking (connection->sock);
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_from_existing (struct GNUNET_NETWORK_Handle *osSocket)
{
  struct GNUNET_CONNECTION_Handle *connection;

  connection = GNUNET_new (struct GNUNET_CONNECTION_Handle);
  connection->write_buffer_size = GNUNET_MIN_MESSAGE_SIZE;
  connection->write_buffer = GNUNET_malloc (connection->write_buffer_size);
  connection->sock = osSocket;
  return connection;
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_from_accept (GNUNET_CONNECTION_AccessCheck access_cb,
                                      void *access_cb_cls,
                                      struct GNUNET_NETWORK_Handle *lsock)
{
  struct GNUNET_CONNECTION_Handle *connection;
  char addr[128];
  socklen_t addrlen;
  struct GNUNET_NETWORK_Handle *sock;
  int aret;
  struct sockaddr_in *v4;
  struct sockaddr_in6 *v6;
  struct sockaddr *sa;
  void *uaddr;
#ifdef SO_PEERCRED
  struct ucred uc;
  socklen_t olen;
#endif
  struct GNUNET_CONNECTION_Credentials *gcp;
#if HAVE_GETPEEREID || defined(SO_PEERCRED) || HAVE_GETPEERUCRED
  struct GNUNET_CONNECTION_Credentials gc;

  gc.uid = 0;
  gc.gid = 0;
#endif

  addrlen = sizeof (addr);
  sock =
      GNUNET_NETWORK_socket_accept (lsock,
                                    (struct sockaddr *) &addr,
                                    &addrlen);
  if (NULL == sock)
  {
    if (EAGAIN != errno)
      LOG_STRERROR (GNUNET_ERROR_TYPE_WARNING, "accept");
    return NULL;
  }
  if ((addrlen > sizeof (addr)) || (addrlen < sizeof (sa_family_t)))
  {
    GNUNET_break (0);
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (sock));
    return NULL;
  }

  sa = (struct sockaddr *) addr;
  v6 = (struct sockaddr_in6 *) addr;
  if ( (AF_INET6 == sa->sa_family) &&
       (IN6_IS_ADDR_V4MAPPED (&v6->sin6_addr)) )
  {
    /* convert to V4 address */
    v4 = GNUNET_new (struct sockaddr_in);
    memset (v4, 0, sizeof (struct sockaddr_in));
    v4->sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
    v4->sin_len = (u_char) sizeof (struct sockaddr_in);
#endif
    GNUNET_memcpy (&v4->sin_addr,
            &((char *) &v6->sin6_addr)[sizeof (struct in6_addr) -
                                       sizeof (struct in_addr)],
            sizeof (struct in_addr));
    v4->sin_port = v6->sin6_port;
    uaddr = v4;
    addrlen = sizeof (struct sockaddr_in);
  }
  else
  {
    uaddr = GNUNET_malloc (addrlen);
    GNUNET_memcpy (uaddr, addr, addrlen);
  }
  gcp = NULL;
  if (AF_UNIX == sa->sa_family)
  {
#if HAVE_GETPEEREID
    /* most BSDs */
    if (0 == getpeereid (GNUNET_NETWORK_get_fd (sock),
                         &gc.uid,
                         &gc.gid))
      gcp = &gc;
#else
#ifdef SO_PEERCRED
    /* largely traditional GNU/Linux */
    olen = sizeof (uc);
    if ( (0 ==
          getsockopt (GNUNET_NETWORK_get_fd (sock),
                      SOL_SOCKET,
                      SO_PEERCRED,
                      &uc,
                      &olen)) &&
         (olen == sizeof (uc)) )
    {
      gc.uid = uc.uid;
      gc.gid = uc.gid;
      gcp = &gc;
    }
#else
#if HAVE_GETPEERUCRED
    /* this is for Solaris 10 */
    ucred_t *uc;

    uc = NULL;
    if (0 == getpeerucred (GNUNET_NETWORK_get_fd (sock), &uc))
    {
      gc.uid = ucred_geteuid (uc);
      gc.gid = ucred_getegid (uc);
      gcp = &gc;
    }
    ucred_free (uc);
#endif
#endif
#endif
  }

  if ( (NULL != access_cb) &&
       (GNUNET_YES != (aret = access_cb (access_cb_cls,
                                         gcp,
                                         uaddr,
                                         addrlen))) )
  {
    if (GNUNET_NO == aret)
      LOG (GNUNET_ERROR_TYPE_INFO,
           _("Access denied to `%s'\n"),
           GNUNET_a2s (uaddr,
                       addrlen));
    GNUNET_break (GNUNET_OK ==
                  GNUNET_NETWORK_socket_shutdown (sock,
                                                  SHUT_RDWR));
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (sock));
    GNUNET_free (uaddr);
    return NULL;
  }
  connection = GNUNET_new (struct GNUNET_CONNECTION_Handle);
  connection->write_buffer_size = GNUNET_MIN_MESSAGE_SIZE;
  connection->write_buffer = GNUNET_malloc (connection->write_buffer_size);
  connection->addr = uaddr;
  connection->addrlen = addrlen;
  connection->sock = sock;
  LOG (GNUNET_ERROR_TYPE_INFO,
       _("Accepting connection from `%s': %p\n"),
       GNUNET_a2s (uaddr,
                   addrlen),
       connection);
  return connection;
}


int
GNUNET_CONNECTION_get_address (struct GNUNET_CONNECTION_Handle *connection,
                               void **addr,
                               size_t *addrlen)
{
  if ((NULL == connection->addr) || (0 == connection->addrlen))
    return GNUNET_NO;
  *addr = GNUNET_malloc (connection->addrlen);
  GNUNET_memcpy (*addr, connection->addr, connection->addrlen);
  *addrlen = connection->addrlen;
  return GNUNET_OK;
}


static void
signal_receive_error (struct GNUNET_CONNECTION_Handle *connection,
                      int errcode)
{
  GNUNET_CONNECTION_Receiver receiver;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Receive encounters error (%s), connection closed (%p)\n",
       STRERROR (errcode),
       connection);
  GNUNET_assert (NULL != (receiver = connection->receiver));
  connection->receiver = NULL;
  receiver (connection->receiver_cls,
            NULL,
            0,
            connection->addr,
            connection->addrlen,
            errcode);
}


static void
signal_receive_timeout (struct GNUNET_CONNECTION_Handle *connection)
{
  GNUNET_CONNECTION_Receiver receiver;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Connection signals timeout to receiver (%p)!\n",
       connection);
  GNUNET_assert (NULL != (receiver = connection->receiver));
  connection->receiver = NULL;
  receiver (connection->receiver_cls, NULL, 0, NULL, 0, 0);
}


static void
signal_transmit_error (struct GNUNET_CONNECTION_Handle *connection,
                       int ecode)
{
  GNUNET_CONNECTION_TransmitReadyNotify notify;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Transmission encounterd error (%s), connection closed (%p)\n",
       STRERROR (ecode),
       connection);
  if (NULL != connection->sock)
  {
    (void) GNUNET_NETWORK_socket_shutdown (connection->sock,
                                           SHUT_RDWR);
    GNUNET_break (GNUNET_OK ==
                  GNUNET_NETWORK_socket_close (connection->sock));
    connection->sock = NULL;
    GNUNET_assert (NULL == connection->write_task);
  }
  if (NULL != connection->read_task)
  {
    /* send errors trigger read errors... */
    GNUNET_SCHEDULER_cancel (connection->read_task);
    connection->read_task = NULL;
    signal_receive_timeout (connection);
    return;
  }
  if (NULL == connection->nth.notify_ready)
    return;                     /* nobody to tell about it */
  notify = connection->nth.notify_ready;
  connection->nth.notify_ready = NULL;
  notify (connection->nth.notify_ready_cls,
          0,
          NULL);
}


static void
connect_fail_continuation (struct GNUNET_CONNECTION_Handle *connection)
{
  LOG (GNUNET_ERROR_TYPE_INFO,
       "Failed to establish TCP connection to `%s:%u', no further addresses to try.\n",
       connection->hostname,
    connection->port);
  GNUNET_break (NULL == connection->ap_head);
  GNUNET_break (NULL == connection->ap_tail);
  GNUNET_break (GNUNET_NO == connection->dns_active);
  GNUNET_break (NULL == connection->sock);
  GNUNET_assert (NULL == connection->write_task);
  GNUNET_assert (NULL == connection->proxy_handshake);

  /* signal errors for jobs that used to wait on the connection */
  connection->destroy_later = 1;
  if (NULL != connection->receiver)
    signal_receive_error (connection,
                          ECONNREFUSED);
  if (NULL != connection->nth.notify_ready)
  {
    GNUNET_assert (NULL != connection->nth.timeout_task);
    GNUNET_SCHEDULER_cancel (connection->nth.timeout_task);
    connection->nth.timeout_task = NULL;
    signal_transmit_error (connection,
                           ECONNREFUSED);
  }
  if (-1 == connection->destroy_later)
  {
    /* do it now */
    connection->destroy_later = 0;
    GNUNET_CONNECTION_destroy (connection);
    return;
  }
  connection->destroy_later = 0;
}


static void
transmit_ready (void *cls);


static void
receive_ready (void *cls);


static void
connect_success_continuation (struct GNUNET_CONNECTION_Handle *connection)
{
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Connection to `%s' succeeded! (%p)\n",
       GNUNET_a2s (connection->addr,
                   connection->addrlen),
       connection);
  /* trigger jobs that waited for the connection */
  if (NULL != connection->receiver)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Connection succeeded, starting with receiving data (%p)\n",
         connection);
    GNUNET_assert (NULL == connection->read_task);
    connection->read_task =
      GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_absolute_get_remaining
                                     (connection->receive_timeout),
                                     connection->sock,
                                     &receive_ready, connection);
  }
  if (NULL != connection->nth.notify_ready)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Connection succeeded, starting with sending data (%p)\n",
         connection);
    GNUNET_assert (connection->nth.timeout_task != NULL);
    GNUNET_SCHEDULER_cancel (connection->nth.timeout_task);
    connection->nth.timeout_task = NULL;
    GNUNET_assert (connection->write_task == NULL);
    connection->write_task =
        GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_absolute_get_remaining
                                        (connection->nth.transmit_timeout), connection->sock,
                                        &transmit_ready, connection);
  }
}


static void
connect_probe_continuation (void *cls)
{
  struct AddressProbe *ap = cls;
  struct GNUNET_CONNECTION_Handle *connection = ap->connection;
  const struct GNUNET_SCHEDULER_TaskContext *tc;
  struct AddressProbe *pos;
  int error;
  socklen_t len;

  GNUNET_assert (NULL != ap->sock);
  GNUNET_CONTAINER_DLL_remove (connection->ap_head,
                               connection->ap_tail,
                               ap);
  len = sizeof (error);
  errno = 0;
  error = 0;
  tc = GNUNET_SCHEDULER_get_task_context ();
  if ( (0 == (tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) ||
       (GNUNET_OK !=
        GNUNET_NETWORK_socket_getsockopt (ap->sock,
                                          SOL_SOCKET,
                                          SO_ERROR,
                                          &error,
                                          &len)) ||
       (0 != error) )
  {
    GNUNET_break (GNUNET_OK ==
                  GNUNET_NETWORK_socket_close (ap->sock));
    GNUNET_free (ap);
    if ( (NULL == connection->ap_head) &&
         (GNUNET_NO == connection->dns_active) &&
         (NULL == connection->proxy_handshake) )
      connect_fail_continuation (connection);
    return;
  }
  GNUNET_assert (NULL == connection->sock);
  connection->sock = ap->sock;
  GNUNET_assert (NULL == connection->addr);
  connection->addr = GNUNET_malloc (ap->addrlen);
  GNUNET_memcpy (connection->addr, ap->addr, ap->addrlen);
  connection->addrlen = ap->addrlen;
  GNUNET_free (ap);
  /* cancel all other attempts */
  while (NULL != (pos = connection->ap_head))
  {
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (pos->sock));
    GNUNET_SCHEDULER_cancel (pos->task);
    GNUNET_CONTAINER_DLL_remove (connection->ap_head,
                                 connection->ap_tail,
                                 pos);
    GNUNET_free (pos);
  }
  connect_success_continuation (connection);
}


static void
try_connect_using_address (void *cls,
                           const struct sockaddr *addr,
                           socklen_t addrlen)
{
  struct GNUNET_CONNECTION_Handle *connection = cls;
  struct AddressProbe *ap;
  struct GNUNET_TIME_Relative delay;

  if (NULL == addr)
  {
    connection->dns_active = NULL;
    if ((NULL == connection->ap_head) &&
        (NULL == connection->sock) &&
        (NULL == connection->proxy_handshake))
      connect_fail_continuation (connection);
    return;
  }
  if (NULL != connection->sock)
    return;                     /* already connected */
  GNUNET_assert (NULL == connection->addr);
  /* try to connect */
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Trying to connect using address `%s:%u/%s:%u'\n",
       connection->hostname,
       connection->port,
       GNUNET_a2s (addr, addrlen),
       connection->port);
  ap = GNUNET_malloc (sizeof (struct AddressProbe) + addrlen);
  ap->addr = (const struct sockaddr *) &ap[1];
  GNUNET_memcpy (&ap[1], addr, addrlen);
  ap->addrlen = addrlen;
  ap->connection = connection;

  switch (ap->addr->sa_family)
  {
  case AF_INET:
    ((struct sockaddr_in *) ap->addr)->sin_port = htons (connection->port);
    break;
  case AF_INET6:
    ((struct sockaddr_in6 *) ap->addr)->sin6_port = htons (connection->port);
    break;
  default:
    GNUNET_break (0);
    GNUNET_free (ap);
    return;                     /* not supported by us */
  }
  ap->sock = GNUNET_NETWORK_socket_create (ap->addr->sa_family,
                                           SOCK_STREAM, 0);
  if (NULL == ap->sock)
  {
    GNUNET_free (ap);
    return;                     /* not supported by OS */
  }
  LOG (GNUNET_ERROR_TYPE_INFO,
       "Trying to connect to `%s' (%p)\n",
       GNUNET_a2s (ap->addr, ap->addrlen),
       connection);
  if ((GNUNET_OK !=
       GNUNET_NETWORK_socket_connect (ap->sock,
                                      ap->addr,
                                      ap->addrlen)) &&
      (EINPROGRESS != errno))
  {
    /* maybe refused / unsupported address, try next */
    LOG_STRERROR (GNUNET_ERROR_TYPE_INFO, "connect");
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (ap->sock));
    GNUNET_free (ap);
    return;
  }
  GNUNET_CONTAINER_DLL_insert (connection->ap_head, connection->ap_tail, ap);
  delay = CONNECT_RETRY_TIMEOUT;
  if (NULL != connection->nth.notify_ready)
    delay = GNUNET_TIME_relative_min (delay,
                                      GNUNET_TIME_absolute_get_remaining (connection->nth.transmit_timeout));
  if (NULL != connection->receiver)
    delay = GNUNET_TIME_relative_min (delay,
                                      GNUNET_TIME_absolute_get_remaining (connection->receive_timeout));
  ap->task = GNUNET_SCHEDULER_add_write_net (delay,
                                             ap->sock,
                                             &connect_probe_continuation,
                                             ap);
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_from_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
                                       const char *hostname,
                                       uint16_t port)
{
  struct GNUNET_CONNECTION_Handle *connection;

  GNUNET_assert (0 < strlen (hostname));        /* sanity check */
  connection = GNUNET_new (struct GNUNET_CONNECTION_Handle);
  connection->cfg = cfg;
  connection->write_buffer_size = GNUNET_MIN_MESSAGE_SIZE;
  connection->write_buffer = GNUNET_malloc (connection->write_buffer_size);
  connection->port = port;
  connection->hostname = GNUNET_strdup (hostname);
  connection->dns_active =
      GNUNET_RESOLVER_ip_get (connection->hostname,
                              AF_UNSPEC,
                              CONNECT_RETRY_TIMEOUT,
                              &try_connect_using_address,
                              connection);
  return connection;
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_from_connect_to_unixpath (const struct GNUNET_CONFIGURATION_Handle *cfg,
                                                   const char *unixpath)
{
#ifdef AF_UNIX
  struct GNUNET_CONNECTION_Handle *connection;
  struct sockaddr_un *un;

  GNUNET_assert (0 < strlen (unixpath));        /* sanity check */
  un = GNUNET_new (struct sockaddr_un);
  un->sun_family = AF_UNIX;
  GNUNET_strlcpy (un->sun_path, unixpath, sizeof (un->sun_path));
#ifdef LINUX
  {
    int abstract;

    abstract = GNUNET_CONFIGURATION_get_value_yesno (cfg,
                                                     "TESTING",
                                                     "USE_ABSTRACT_SOCKETS");
    if (GNUNET_YES == abstract)
      un->sun_path[0] = '\0';
  }
#endif
#if HAVE_SOCKADDR_UN_SUN_LEN
  un->sun_len = (u_char) sizeof (struct sockaddr_un);
#endif
  connection = GNUNET_new (struct GNUNET_CONNECTION_Handle);
  connection->cfg = cfg;
  connection->write_buffer_size = GNUNET_MIN_MESSAGE_SIZE;
  connection->write_buffer = GNUNET_malloc (connection->write_buffer_size);
  connection->port = 0;
  connection->hostname = NULL;
  connection->addr = (struct sockaddr *) un;
  connection->addrlen = sizeof (struct sockaddr_un);
  connection->sock = GNUNET_NETWORK_socket_create (AF_UNIX,
                                                   SOCK_STREAM,
                                                   0);
  if (NULL == connection->sock)
  {
    GNUNET_free (connection->addr);
    GNUNET_free (connection->write_buffer);
    GNUNET_free (connection);
    return NULL;
  }
  if ( (GNUNET_OK !=
        GNUNET_NETWORK_socket_connect (connection->sock,
                                       connection->addr,
                                       connection->addrlen)) &&
       (EINPROGRESS != errno) )
  {
    /* Just return; we expect everything to work eventually so don't fail HARD */
    GNUNET_break (GNUNET_OK ==
                  GNUNET_NETWORK_socket_close (connection->sock));
    connection->sock = NULL;
    return connection;
  }
  connect_success_continuation (connection);
  return connection;
#else
  return NULL;
#endif
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_connect_socket (struct GNUNET_NETWORK_Handle *s,
                                  const struct sockaddr *serv_addr,
                                  socklen_t addrlen)
{
  struct GNUNET_CONNECTION_Handle *connection;

  if ( (GNUNET_OK !=
        GNUNET_NETWORK_socket_connect (s, serv_addr, addrlen)) &&
       (EINPROGRESS != errno) )
  {
    /* maybe refused / unsupported address, try next */
    LOG_STRERROR (GNUNET_ERROR_TYPE_DEBUG,
                  "connect");
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Attempt to connect to `%s' failed\n",
         GNUNET_a2s (serv_addr,
                     addrlen));
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (s));
    return NULL;
  }
  connection = GNUNET_CONNECTION_create_from_existing (s);
  connection->addr = GNUNET_malloc (addrlen);
  GNUNET_memcpy (connection->addr, serv_addr, addrlen);
  connection->addrlen = addrlen;
  LOG (GNUNET_ERROR_TYPE_INFO,
       "Trying to connect to `%s' (%p)\n",
       GNUNET_a2s (serv_addr, addrlen),
       connection);
  return connection;
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_from_sockaddr (int af_family,
                                        const struct sockaddr *serv_addr,
                                        socklen_t addrlen)
{
  struct GNUNET_NETWORK_Handle *s;

  s = GNUNET_NETWORK_socket_create (af_family, SOCK_STREAM, 0);
  if (NULL == s)
  {
    LOG_STRERROR (GNUNET_ERROR_TYPE_WARNING | GNUNET_ERROR_TYPE_BULK,
                  "socket");
    return NULL;
  }
  return GNUNET_CONNECTION_connect_socket (s,
                                           serv_addr,
                                           addrlen);
}


int
GNUNET_CONNECTION_check (struct GNUNET_CONNECTION_Handle *connection)
{
  if ((NULL != connection->ap_head) ||
      (NULL != connection->dns_active) ||
      (NULL != connection->proxy_handshake))
    return GNUNET_YES;          /* still trying to connect */
  if ( (0 != connection->destroy_later) ||
       (NULL == connection->sock) )
    return GNUNET_NO;
  return GNUNET_YES;
}


void
GNUNET_CONNECTION_destroy (struct GNUNET_CONNECTION_Handle *connection)
{
  struct AddressProbe *pos;

  if (0 != connection->destroy_later)
  {
    connection->destroy_later = -1;
    return;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Shutting down connection (%p)\n",
       connection);
  GNUNET_assert (NULL == connection->nth.notify_ready);
  GNUNET_assert (NULL == connection->receiver);
  if (NULL != connection->write_task)
  {
    GNUNET_SCHEDULER_cancel (connection->write_task);
    connection->write_task = NULL;
    connection->write_buffer_off = 0;
  }
  if (NULL != connection->read_task)
  {
    GNUNET_SCHEDULER_cancel (connection->read_task);
    connection->read_task = NULL;
  }
  if (NULL != connection->nth.timeout_task)
  {
    GNUNET_SCHEDULER_cancel (connection->nth.timeout_task);
    connection->nth.timeout_task = NULL;
  }
  connection->nth.notify_ready = NULL;
  if (NULL != connection->dns_active)
  {
    GNUNET_RESOLVER_request_cancel (connection->dns_active);
    connection->dns_active = NULL;
  }
  if (NULL != connection->proxy_handshake)
  {
    /* GNUNET_CONNECTION_destroy (connection->proxy_handshake); */
    connection->proxy_handshake->destroy_later = -1;
    connection->proxy_handshake = NULL;  /* Not leaked ??? */
  }
  while (NULL != (pos = connection->ap_head))
  {
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (pos->sock));
    GNUNET_SCHEDULER_cancel (pos->task);
    GNUNET_CONTAINER_DLL_remove (connection->ap_head,
                                 connection->ap_tail,
                                 pos);
    GNUNET_free (pos);
  }
  if ( (NULL != connection->sock) &&
       (GNUNET_YES != connection->persist) )
  {
    if ((GNUNET_OK !=
         GNUNET_NETWORK_socket_shutdown (connection->sock,
                                         SHUT_RDWR)) &&
        (ENOTCONN != errno) &&
        (ECONNRESET != errno) )
      LOG_STRERROR (GNUNET_ERROR_TYPE_WARNING,
                    "shutdown");
  }
  if (NULL != connection->sock)
  {
    if (GNUNET_YES != connection->persist)
    {
      GNUNET_break (GNUNET_OK ==
                    GNUNET_NETWORK_socket_close (connection->sock));
    }
    else
    {
      GNUNET_NETWORK_socket_free_memory_only_ (connection->sock); /* at least no memory leak (we deliberately
                                                                   * leak the socket in this special case) ... */
    }
  }
  GNUNET_free_non_null (connection->addr);
  GNUNET_free_non_null (connection->hostname);
  GNUNET_free (connection->write_buffer);
  GNUNET_free (connection);
}


static void
receive_ready (void *cls)
{
  struct GNUNET_CONNECTION_Handle *connection = cls;
  const struct GNUNET_SCHEDULER_TaskContext *tc;
  char buffer[connection->max];
  ssize_t ret;
  GNUNET_CONNECTION_Receiver receiver;

  connection->read_task = NULL;
  tc = GNUNET_SCHEDULER_get_task_context ();
  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_TIMEOUT))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Receive from `%s' encounters error: timeout (%s, %p)\n",
         GNUNET_a2s (connection->addr,
                     connection->addrlen),
         GNUNET_STRINGS_relative_time_to_string (GNUNET_TIME_absolute_get_duration (connection->receive_timeout),
                                                 GNUNET_YES),
         connection);
    signal_receive_timeout (connection);
    return;
  }
  if (NULL == connection->sock)
  {
    /* connect failed for good */
    signal_receive_error (connection, ECONNREFUSED);
    return;
  }
  GNUNET_assert (GNUNET_NETWORK_fdset_isset (tc->read_ready,
                                             connection->sock));
RETRY:
  ret = GNUNET_NETWORK_socket_recv (connection->sock,
                                    buffer,
                                    connection->max);
  if (-1 == ret)
  {
    if (EINTR == errno)
      goto RETRY;
    signal_receive_error (connection, errno);
    return;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "receive_ready read %u/%u bytes from `%s' (%p)!\n",
       (unsigned int) ret,
       connection->max,
       GNUNET_a2s (connection->addr,
                   connection->addrlen),
       connection);
  GNUNET_assert (NULL != (receiver = connection->receiver));
  connection->receiver = NULL;
  receiver (connection->receiver_cls,
            buffer,
            ret,
            connection->addr,
            connection->addrlen,
            0);
}


int
GNUNET_CONNECTION_receive (struct GNUNET_CONNECTION_Handle *connection,
                           size_t max,
                           struct GNUNET_TIME_Relative timeout,
                           GNUNET_CONNECTION_Receiver receiver,
                           void *receiver_cls)
{
  GNUNET_assert ((NULL == connection->read_task) &&
                 (NULL == connection->receiver));
  GNUNET_assert (NULL != receiver);
  connection->receiver = receiver;
  connection->receiver_cls = receiver_cls;
  connection->receive_timeout = GNUNET_TIME_relative_to_absolute (timeout);
  connection->max = max;
  if (NULL != connection->sock)
  {
    connection->read_task =
      GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_absolute_get_remaining
                                     (connection->receive_timeout),
                                     connection->sock,
                                     &receive_ready,
                                     connection);
    return GNUNET_OK;
  }
  if ((NULL == connection->dns_active) &&
      (NULL == connection->ap_head) &&
      (NULL == connection->proxy_handshake))
  {
    connection->receiver = NULL;
    receiver (receiver_cls,
              NULL, 0,
              NULL, 0,
              ETIMEDOUT);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


void *
GNUNET_CONNECTION_receive_cancel (struct GNUNET_CONNECTION_Handle *connection)
{
  if (NULL != connection->read_task)
  {
    GNUNET_assert (connection ==
                   GNUNET_SCHEDULER_cancel (connection->read_task));
    connection->read_task = NULL;
  }
  connection->receiver = NULL;
  return connection->receiver_cls;
}


static int
process_notify (struct GNUNET_CONNECTION_Handle *connection)
{
  size_t used;
  size_t avail;
  size_t size;
  GNUNET_CONNECTION_TransmitReadyNotify notify;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "process_notify is running\n");
  GNUNET_assert (NULL == connection->write_task);
  if (NULL == (notify = connection->nth.notify_ready))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "No one to notify\n");
    return GNUNET_NO;
  }
  used = connection->write_buffer_off - connection->write_buffer_pos;
  avail = connection->write_buffer_size - used;
  size = connection->nth.notify_size;
  if (size > avail)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Not enough buffer\n");
    return GNUNET_NO;
  }
  connection->nth.notify_ready = NULL;
  if (connection->write_buffer_size - connection->write_buffer_off < size)
  {
    /* need to compact */
    memmove (connection->write_buffer,
             &connection->write_buffer[connection->write_buffer_pos],
             used);
    connection->write_buffer_off -= connection->write_buffer_pos;
    connection->write_buffer_pos = 0;
  }
  avail = connection->write_buffer_size - connection->write_buffer_off;
  GNUNET_assert (avail >= size);
  size =
      notify (connection->nth.notify_ready_cls, avail,
              &connection->write_buffer[connection->write_buffer_off]);
  GNUNET_assert (size <= avail);
  if (0 != size)
    connection->write_buffer_off += size;
  return GNUNET_YES;
}


static void
transmit_timeout (void *cls)
{
  struct GNUNET_CONNECTION_Handle *connection = cls;
  GNUNET_CONNECTION_TransmitReadyNotify notify;

  connection->nth.timeout_task = NULL;
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Transmit to `%s:%u/%s' fails, time out reached (%p).\n",
       connection->hostname,
       connection->port,
       GNUNET_a2s (connection->addr,
                   connection->addrlen),
       connection);
  notify = connection->nth.notify_ready;
  GNUNET_assert (NULL != notify);
  connection->nth.notify_ready = NULL;
  notify (connection->nth.notify_ready_cls,
          0,
          NULL);
}


static void
connect_error (void *cls)
{
  struct GNUNET_CONNECTION_Handle *connection = cls;
  GNUNET_CONNECTION_TransmitReadyNotify notify;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Transmission request of size %u fails (%s/%u), connection failed (%p).\n",
       connection->nth.notify_size,
       connection->hostname,
       connection->port,
       connection);
  connection->write_task = NULL;
  notify = connection->nth.notify_ready;
  connection->nth.notify_ready = NULL;
  notify (connection->nth.notify_ready_cls,
          0,
          NULL);
}


static void
transmit_ready (void *cls)
{
  struct GNUNET_CONNECTION_Handle *connection = cls;
  GNUNET_CONNECTION_TransmitReadyNotify notify;
  const struct GNUNET_SCHEDULER_TaskContext *tc;
  ssize_t ret;
  size_t have;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "transmit_ready running (%p).\n",
       connection);
  GNUNET_assert (NULL != connection->write_task);
  connection->write_task = NULL;
  GNUNET_assert (NULL == connection->nth.timeout_task);
  tc = GNUNET_SCHEDULER_get_task_context ();
  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_TIMEOUT))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Transmit to `%s' fails, time out reached (%p).\n",
         GNUNET_a2s (connection->addr,
                     connection->addrlen),
         connection);
    notify = connection->nth.notify_ready;
    GNUNET_assert (NULL != notify);
    connection->nth.notify_ready = NULL;
    notify (connection->nth.notify_ready_cls, 0, NULL);
    return;
  }
  GNUNET_assert (NULL != connection->sock);
  if (NULL == tc->write_ready)
  {
    /* special circumstances (in particular, PREREQ_DONE after
     * connect): not yet ready to write, but no "fatal" error either.
     * Hence retry.  */
    goto SCHEDULE_WRITE;
  }
  if (! GNUNET_NETWORK_fdset_isset (tc->write_ready,
                                    connection->sock))
  {
    GNUNET_assert (NULL == connection->write_task);
    /* special circumstances (in particular, shutdown): not yet ready
     * to write, but no "fatal" error either.  Hence retry.  */
    goto SCHEDULE_WRITE;
  }
  GNUNET_assert (connection->write_buffer_off >= connection->write_buffer_pos);
  if ((NULL != connection->nth.notify_ready) &&
      (connection->write_buffer_size < connection->nth.notify_size))
  {
    connection->write_buffer =
        GNUNET_realloc (connection->write_buffer, connection->nth.notify_size);
    connection->write_buffer_size = connection->nth.notify_size;
  }
  process_notify (connection);
  have = connection->write_buffer_off - connection->write_buffer_pos;
  if (0 == have)
  {
    /* no data ready for writing, terminate write loop */
    return;
  }
  GNUNET_assert (have <= connection->write_buffer_size);
  GNUNET_assert (have + connection->write_buffer_pos <= connection->write_buffer_size);
  GNUNET_assert (connection->write_buffer_pos <= connection->write_buffer_size);
RETRY:
  ret =
      GNUNET_NETWORK_socket_send (connection->sock,
                                  &connection->write_buffer[connection->write_buffer_pos],
                                  have);
  if (-1 == ret)
  {
    if (EINTR == errno)
      goto RETRY;
    if (NULL != connection->write_task)
    {
      GNUNET_SCHEDULER_cancel (connection->write_task);
      connection->write_task = NULL;
    }
    signal_transmit_error (connection, errno);
    return;
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Connection transmitted %u/%u bytes to `%s' (%p)\n",
       (unsigned int) ret,
       have,
       GNUNET_a2s (connection->addr,
                   connection->addrlen),
       connection);
  connection->write_buffer_pos += ret;
  if (connection->write_buffer_pos == connection->write_buffer_off)
  {
    /* transmitted all pending data */
    connection->write_buffer_pos = 0;
    connection->write_buffer_off = 0;
  }
  if ( (0 == connection->write_buffer_off) &&
       (NULL == connection->nth.notify_ready) )
    return;                     /* all data sent! */
  /* not done writing, schedule more */
SCHEDULE_WRITE:
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Re-scheduling transmit_ready (more to do) (%p).\n",
       connection);
  have = connection->write_buffer_off - connection->write_buffer_pos;
  GNUNET_assert ( (NULL != connection->nth.notify_ready) ||
                  (have > 0) );
  if (NULL == connection->write_task)
    connection->write_task =
        GNUNET_SCHEDULER_add_write_net ((connection->nth.notify_ready ==
                                         NULL) ? GNUNET_TIME_UNIT_FOREVER_REL :
                                        GNUNET_TIME_absolute_get_remaining
                                        (connection->nth.transmit_timeout),
                                        connection->sock,
                                        &transmit_ready, connection);
}


struct GNUNET_CONNECTION_TransmitHandle *
GNUNET_CONNECTION_notify_transmit_ready (struct GNUNET_CONNECTION_Handle *connection,
                                         size_t size,
                                         struct GNUNET_TIME_Relative timeout,
                                         GNUNET_CONNECTION_TransmitReadyNotify notify,
                                         void *notify_cls)
{
  if (NULL != connection->nth.notify_ready)
  {
    GNUNET_assert (0);
    return NULL;
  }
  GNUNET_assert (NULL != notify);
  GNUNET_assert (size < GNUNET_MAX_MESSAGE_SIZE);
  GNUNET_assert (connection->write_buffer_off <= connection->write_buffer_size);
  GNUNET_assert (connection->write_buffer_pos <= connection->write_buffer_size);
  GNUNET_assert (connection->write_buffer_pos <= connection->write_buffer_off);
  connection->nth.notify_ready = notify;
  connection->nth.notify_ready_cls = notify_cls;
  connection->nth.connection = connection;
  connection->nth.notify_size = size;
  connection->nth.transmit_timeout = GNUNET_TIME_relative_to_absolute (timeout);
  GNUNET_assert (NULL == connection->nth.timeout_task);
  if ((NULL == connection->sock) &&
      (NULL == connection->ap_head) &&
      (NULL == connection->dns_active) &&
      (NULL == connection->proxy_handshake))
  {
    if (NULL != connection->write_task)
      GNUNET_SCHEDULER_cancel (connection->write_task);
    connection->write_task = GNUNET_SCHEDULER_add_now (&connect_error,
                                                       connection);
    return &connection->nth;
  }
  if (NULL != connection->write_task)
    return &connection->nth; /* previous transmission still in progress */
  if (NULL != connection->sock)
  {
    /* connected, try to transmit now */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Scheduling transmission (%p).\n",
         connection);
    connection->write_task =
        GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_absolute_get_remaining
                                        (connection->nth.transmit_timeout),
                                        connection->sock,
                                        &transmit_ready, connection);
    return &connection->nth;
  }
  /* not yet connected, wait for connection */
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Need to wait to schedule transmission for connection, adding timeout task (%p).\n",
       connection);
  connection->nth.timeout_task =
    GNUNET_SCHEDULER_add_delayed (timeout,
                                  &transmit_timeout,
                                  connection);
  return &connection->nth;
}


void
GNUNET_CONNECTION_notify_transmit_ready_cancel (struct GNUNET_CONNECTION_TransmitHandle *th)
{
  GNUNET_assert (NULL != th->notify_ready);
  th->notify_ready = NULL;
  if (NULL != th->timeout_task)
  {
    GNUNET_SCHEDULER_cancel (th->timeout_task);
    th->timeout_task = NULL;
  }
  if (NULL != th->connection->write_task)
  {
    GNUNET_SCHEDULER_cancel (th->connection->write_task);
    th->connection->write_task = NULL;
  }
}


struct GNUNET_CONNECTION_Handle *
GNUNET_CONNECTION_create_proxied_from_handshake (struct GNUNET_CONNECTION_Handle *cph)
{
  struct GNUNET_CONNECTION_Handle *proxied = GNUNET_CONNECTION_create_from_existing (NULL);

  proxied->proxy_handshake = cph;
  return proxied;
}


void
GNUNET_CONNECTION_acivate_proxied (struct GNUNET_CONNECTION_Handle *proxied)
{
  struct GNUNET_CONNECTION_Handle *cph = proxied->proxy_handshake;

  GNUNET_assert (NULL != cph);
  GNUNET_assert (NULL == proxied->sock);
  GNUNET_assert (NULL != cph->sock);
  proxied->sock = cph->sock;
  cph->sock = NULL;
  GNUNET_CONNECTION_destroy (cph);
  connect_success_continuation (proxied);
}


/* end of connection.c */