tunnel.c

Serveez是一个服务器框架

/*
 * Tunnel server TCP and pipe detection routine. It is greedy. Thus it cannot 
 * share the port configuration with other TCP or pipe servers.
 */
int
tnl_detect_proto (svz_server_t *server, svz_socket_t *sock)
{
  svz_log (LOG_NOTICE, "tunnel: %s connection accepted\n",
	   sock->flags & SOCK_FLAG_PIPE ? "pipe" : "tcp");
  return -1;
}

/*
 * If any TCP or pipe connection has been accepted this routine is called 
 * to setup the tunnel server specific callbacks.
 */
int
tnl_connect_socket (svz_server_t *server, svz_socket_t *sock)
{
  svz_socket_t *xsock = NULL;
  tnl_connect_t *source;
  
  sock->flags |= SOCK_FLAG_NOFLOOD;
  sock->check_request = sock->flags & SOCK_FLAG_PIPE ?
    tnl_check_request_pipe_source : tnl_check_request_tcp_source;
  sock->disconnected_socket = tnl_disconnect_source;
  svz_sock_resize_buffers (sock, UDP_BUF_SIZE, UDP_BUF_SIZE);

  /* try connecting to target */
  xsock = tnl_create_socket (sock, sock->flags & SOCK_FLAG_PIPE ?
			     TNL_FLAG_SRC_PIPE : TNL_FLAG_SRC_TCP);
  if (xsock == NULL)
    return -1;

  /* put the source connection into data field */
  source = tnl_create_connect ();
  source->source_sock = sock;
  source->target_sock = xsock;
  source->ip = sock->remote_addr;
  source->port = sock->remote_port;
  xsock->data = source;
  sock->data = source;

  return 0;
}

/*
 * The tunnel servers TCP check_request routine for target connections.
 * Each TCP target connection gets assigned this function in order to
 * send data back to its source connection.
 */
int
tnl_check_request_tcp_target (svz_socket_t *sock)
{
  svz_socket_t *xsock = NULL;
  tnl_connect_t *source = sock->data;

#if ENABLE_DEBUG
  if (source == NULL || source->source_sock == NULL)
    {
      svz_log (LOG_FATAL, "tunnel: tcp target has no source connection\n");
      return -1;
    }
#endif /* ENABLE_DEBUG */

  /* obtain source connection */
  xsock = source->source_sock;
  xsock->remote_addr = source->ip;
  xsock->remote_port = source->port;

  /* forward data to source connection */
  if (tnl_send_request_target (xsock, sock->recv_buffer, 
			       sock->recv_buffer_fill, sock->userflags) == -1)
    {
      svz_sock_schedule_for_shutdown (xsock);
      return -1;
    }

  /* empty the receive buffer of this target connection */
  sock->recv_buffer_fill = 0;
  return 0;
}

/*
 * The tunnel servers TCP check_request() routine for the source connections.
 * It simply copies the received data to the send buffer of the target
 * connection.
 */
int
tnl_check_request_tcp_source (svz_socket_t *sock)
{
  tnl_connect_t *target = sock->data;
  svz_socket_t *xsock;

#if ENABLE_DEBUG
  if (target == NULL || target->target_sock == NULL)
    {
      svz_log (LOG_FATAL, "tunnel: tcp source has no target connection\n");
      return -1;
    }
#endif /* ENABLE_DEBUG */

  /* obtain target connection */
  xsock = target->target_sock;

  /* forward data to target connection */
  if (tnl_send_request_source (xsock, sock->recv_buffer, 
			       sock->recv_buffer_fill, sock->userflags) == -1)
    {
      return -1;
    }

  sock->recv_buffer_fill = 0;
  return 0;
}

/*
 * This function is the handle_request() routine for target UDP sockets.
 */
int
tnl_handle_request_udp_target (svz_socket_t *sock, char *packet, int len)
{
  tnl_connect_t *source = sock->data;
  svz_socket_t *xsock = NULL;

#if ENABLE_DEBUG
  if (source == NULL || source->source_sock == NULL)
    {
      svz_log (LOG_FATAL, "tunnel: udp target has no source connection\n");
      return -1;
    }
#endif /* ENABLE_DEBUG */

  /* get source connection from data field */
  xsock = source->source_sock;
  xsock->remote_addr = source->ip;
  xsock->remote_port = source->port;

  /* forward packet data to source connection */
  if (tnl_send_request_target (xsock, packet, len, sock->userflags) == -1)
    {
      /* shutdown the source connection if it is TCP or pipe */
      if (sock->userflags & (TNL_FLAG_SRC_TCP | TNL_FLAG_SRC_PIPE))
	svz_sock_schedule_for_shutdown (xsock);
      return -1;
    }

  /* returning zero means that the packet has been processed */
  return 0;
}

/*
 * This function is the handle_request() routine for source UDP sockets.
 * It accepts UDP connections (listening connection) or forwards data
 * to existing target sockets.
 */
int
tnl_handle_request_udp_source (svz_socket_t *sock, char *packet, int len)
{
  tnl_config_t *cfg = sock->cfg;
  tnl_connect_t *source;
  svz_socket_t *xsock = NULL;

  /* check if there is such a connection in the source hash already */
  source = svz_hash_get (cfg->client, tnl_addr (sock));
  if (source)
    {
      /* get existing target socket */
      xsock = source->target_sock;
    }
  else
    {
      /* start connecting to a new target */
      if ((xsock = tnl_create_socket (sock, TNL_FLAG_SRC_UDP)) == NULL)
	return 0;

      /* foreign address not in hash, create new target connection */
      source = tnl_create_connect ();
      source->source_sock = sock;
      source->ip = sock->remote_addr;
      source->port = sock->remote_port;
      svz_hash_put (cfg->client, tnl_addr (sock), source);

      /* put the source connection into data field of target */
      xsock->data = source;
      source->target_sock = xsock;
    }

  /* forward packet data to target connection */
  if (tnl_send_request_source (xsock, packet, len, sock->userflags) == -1)
    {
      svz_sock_schedule_for_shutdown (xsock);
      return 0;
    }

  return 0;
}

/*
 * This function is the handle_request routine for target ICMP sockets.
 */
int
tnl_handle_request_icmp_target (svz_socket_t *sock, char *packet, int len)
{
  tnl_connect_t *source = sock->data;
  svz_socket_t *xsock = NULL;

#if ENABLE_DEBUG
  if (source == NULL || source->source_sock == NULL)
    {
      svz_log (LOG_FATAL,
	       "tunnel: icmp target has no source connection\n");
      return -1;
    }
#endif /* ENABLE_DEBUG */

  /* get source connection from data field */
  xsock = source->source_sock;
  xsock->remote_addr = source->ip;
  xsock->remote_port = source->port;

  /* forward packet data to source connection */
  if (tnl_send_request_target (xsock, packet, len, sock->userflags) == -1)
    {
      /* shutdown source connection if it is TCP or pipe */
      if (sock->userflags & (TNL_FLAG_SRC_TCP | TNL_FLAG_SRC_PIPE))
	svz_sock_schedule_for_shutdown (xsock);
      return -1;
    }

  /* packet successfully processed */
  return 0;
}

/*
 * This function is the handle_request() routine for source ICMP sockets.
 * It accepts ICMP connections (listening connection) or forwards data
 * to existing target sockets.
 */
int
tnl_handle_request_icmp_source (svz_socket_t *sock, char *packet, int len)
{
  tnl_config_t *cfg = sock->cfg;
  tnl_connect_t *source;
  svz_socket_t *xsock = NULL;

  /* check if there is such a connection in the source hash already */
  source = svz_hash_get (cfg->client, tnl_addr (sock));
  if (source)
    {
      /* get existing target socket */
      xsock = source->target_sock;
    }
  else
    {
      /* start connecting */
      if ((xsock = tnl_create_socket (sock, TNL_FLAG_SRC_ICMP)) == NULL)
	return 0;

      /* foreign address not in hash, create new target connection */
      source = tnl_create_connect ();
      source->source_sock = sock;
      source->ip = sock->remote_addr;
      source->port = sock->remote_port;
      svz_hash_put (cfg->client, tnl_addr (sock), source);

      /* put the source connection into data field */
      xsock->data = source;
      source->target_sock = xsock;
    }

  /* forward packet data to target connection */
  if (tnl_send_request_source (xsock, packet, len, sock->userflags) == -1)
    {
      svz_sock_schedule_for_shutdown (xsock);
      return 0;
    }

  return 0;
}

/*
 * The targets's disconnection routine for types of targets (TCP, PIPE,
 * ICMP and UDP).
 */
int
tnl_disconnect_target (svz_socket_t *sock)
{
  tnl_config_t *cfg = sock->cfg;
  tnl_connect_t *source = sock->data;
  svz_socket_t *xsock;
  char *key;

  /* do not do anything if we are shutting down */
  if (svz_nuke_happened)
    {
      /* if source is TCP or PIPE then shutdown referring connection */
      if (sock->userflags & (TNL_FLAG_SRC_TCP | TNL_FLAG_SRC_PIPE))
	{
	  xsock = source ? source->source_sock : NULL;
	  if (xsock)
	    xsock->data = NULL;
	  tnl_free_connect (sock);
	}
      return 0;
    }

#if ENABLE_DEBUG
  if (source == NULL || source->source_sock == NULL)
    {
      svz_log (LOG_FATAL, "tunnel: target has no source connection\n");
      return -1;
    }
#endif /* ENABLE_DEBUG */

  /* obtain source connection */
  xsock = source->source_sock;

  /* if the source connection is ICMP send a disconnection message */
  if (sock->userflags & TNL_FLAG_SRC_ICMP)
    {
#if ENABLE_DEBUG
      svz_log (LOG_DEBUG,
	       "tunnel: sending icmp disconnect on socket id %d\n",
	       xsock->id);
#endif /* ENABLE_DEBUG */
      svz_icmp_send_control (xsock, ICMP_SERVEEZ_CLOSE);
    }

  /* if source is TCP or PIPE then shutdown referring connection */
  if (sock->userflags & (TNL_FLAG_SRC_TCP | TNL_FLAG_SRC_PIPE))
    {
#if ENABLE_DEBUG
      svz_log (LOG_DEBUG, "tunnel: shutdown referrer id %d\n", xsock->id);
#endif /* ENABLE_DEBUG */
      svz_sock_schedule_for_shutdown (xsock);
      xsock->data = NULL;
      tnl_free_connect (sock);
    }
  /* else delete target connection from its hash */
  else if ((key = svz_hash_contains (cfg->client, source)) != NULL)
    {
      svz_hash_delete (cfg->client, key);
      tnl_free_connect (sock);
    }

  return 0;
}

/*
 * What happens if a source connection gets lost.
 */
int
tnl_disconnect_source (svz_socket_t *sock)
{
  tnl_connect_t *target = sock->data;
  svz_socket_t *xsock;

  /* if target is TCP or PIPE shutdown referring connection */
  if (sock->userflags & (TNL_FLAG_TGT_TCP | TNL_FLAG_TGT_PIPE))
    {
#if ENABLE_DEBUG
      if (target == NULL || target->target_sock == NULL)
	{
	  svz_log (LOG_DEBUG, "tunnel: tcp/pipe source has no "
		   "target connection\n");
	  return -1;
	}
#endif /* ENABLE_DEBUG */

      /* get target connection */
      xsock = target->target_sock;

#if ENABLE_DEBUG
      svz_log (LOG_DEBUG, "tunnel: shutdown referrer id %d\n", xsock->id);
#endif /* ENABLE_DEBUG */
      svz_sock_schedule_for_shutdown (xsock);
      xsock->data = NULL;
      tnl_free_connect (sock);
    }

  return 0;
}

/*
 * Because UDP and ICMP sockets cannot not be detected as being closed
 * we need to shutdown target sockets ourselves.
 */
int
tnl_idle (svz_socket_t *sock)
{
  time_t t = time (NULL);

  if (t - sock->last_recv < TNL_TIMEOUT || t - sock->last_send < TNL_TIMEOUT)
    {
      sock->idle_counter = TNL_TIMEOUT;
      return 0;
    }
  return -1;
}

#else /* not ENABLE_TUNNEL */

int tunnel_dummy; /* Shut compiler warnings up. */

#endif /* not ENABLE_TUNNEL */