relay.c

关于tor匿名通信的源代码

        log_info(domain,"end cell (%s) dropped, unknown stream.",
                 connection_edge_end_reason_str(reason));
        return 0;
      }
/* XXX add to this log_fn the exit node's nickname? */
      log_info(domain,"%d: end cell (%s) for stream %d. Removing stream.",
               conn->_base.s,
               connection_edge_end_reason_str(reason),
               conn->stream_id);
      if (conn->socks_request && !conn->socks_request->has_finished)
        log_warn(LD_BUG,
                 "open stream hasn't sent socks answer yet? Closing.");
      /* We just *got* an end; no reason to send one. */
      conn->_base.edge_has_sent_end = 1;
      if (!conn->end_reason)
        conn->end_reason = reason | END_STREAM_REASON_FLAG_REMOTE;
      if (!conn->_base.marked_for_close) {
        /* only mark it if not already marked. it's possible to
         * get the 'end' right around when the client hangs up on us. */
        connection_mark_for_close(TO_CONN(conn));
        conn->_base.hold_open_until_flushed = 1;
      }
      return 0;
    case RELAY_COMMAND_EXTEND:
      if (conn) {
        log_fn(LOG_PROTOCOL_WARN, domain,
               "'extend' cell received for non-zero stream. Dropping.");
        return 0;
      }
      return circuit_extend(cell, circ);
    case RELAY_COMMAND_EXTENDED:
      if (!layer_hint) {
        log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
               "'extended' unsupported at non-origin. Dropping.");
        return 0;
      }
      log_debug(domain,"Got an extended cell! Yay.");
      if ((reason = circuit_finish_handshake(TO_ORIGIN_CIRCUIT(circ),
                                       CELL_CREATED,
                                       cell->payload+RELAY_HEADER_SIZE)) < 0) {
        log_warn(domain,"circuit_finish_handshake failed.");
        return reason;
      }
      if ((reason=circuit_send_next_onion_skin(TO_ORIGIN_CIRCUIT(circ)))<0) {
        log_info(domain,"circuit_send_next_onion_skin() failed.");
        return reason;
      }
      return 0;
    case RELAY_COMMAND_TRUNCATE:
      if (layer_hint) {
        log_fn(LOG_PROTOCOL_WARN, LD_APP,
               "'truncate' unsupported at origin. Dropping.");
        return 0;
      }
      if (circ->n_conn) {
        uint8_t trunc_reason = *(uint8_t*)(cell->payload + RELAY_HEADER_SIZE);
        connection_or_send_destroy(circ->n_circ_id, circ->n_conn,
                                   trunc_reason);
        circuit_set_n_circid_orconn(circ, 0, NULL);
      }
      log_debug(LD_EXIT, "Processed 'truncate', replying.");
      {
        char payload[1];
        payload[0] = (char)END_CIRC_REASON_REQUESTED;
        relay_send_command_from_edge(0, circ, RELAY_COMMAND_TRUNCATED,
                                     payload, sizeof(payload), NULL);
      }
      return 0;
    case RELAY_COMMAND_TRUNCATED:
      if (!layer_hint) {
        log_fn(LOG_PROTOCOL_WARN, LD_EXIT,
               "'truncated' unsupported at non-origin. Dropping.");
        return 0;
      }
      circuit_truncated(TO_ORIGIN_CIRCUIT(circ), layer_hint);
      return 0;
    case RELAY_COMMAND_CONNECTED:
      if (conn) {
        log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
               "'connected' unsupported while open. Closing circ.");
        return -END_CIRC_REASON_TORPROTOCOL;
      }
      log_info(domain,
               "'connected' received, no conn attached anymore. Ignoring.");
      return 0;
    case RELAY_COMMAND_SENDME:
      if (!conn) {
        if (layer_hint) {
          layer_hint->package_window += CIRCWINDOW_INCREMENT;
          log_debug(LD_APP,"circ-level sendme at origin, packagewindow %d.",
                    layer_hint->package_window);
          circuit_resume_edge_reading(circ, layer_hint);
        } else {
          circ->package_window += CIRCWINDOW_INCREMENT;
          log_debug(LD_APP,
                    "circ-level sendme at non-origin, packagewindow %d.",
                    circ->package_window);
          circuit_resume_edge_reading(circ, layer_hint);
        }
        return 0;
      }
      conn->package_window += STREAMWINDOW_INCREMENT;
      log_debug(domain,"stream-level sendme, packagewindow now %d.",
                conn->package_window);
      connection_start_reading(TO_CONN(conn));
      /* handle whatever might still be on the inbuf */
      if (connection_edge_package_raw_inbuf(conn, 1) < 0) {
        /* (We already sent an end cell if possible) */
        connection_mark_for_close(TO_CONN(conn));
        return 0;
      }
      return 0;
    case RELAY_COMMAND_RESOLVE:
      if (layer_hint) {
        log_fn(LOG_PROTOCOL_WARN, LD_APP,
               "resolve request unsupported at AP; dropping.");
        return 0;
      } else if (conn) {
        log_fn(LOG_PROTOCOL_WARN, domain,
               "resolve request for known stream; dropping.");
        return 0;
      } else if (circ->purpose != CIRCUIT_PURPOSE_OR) {
        log_fn(LOG_PROTOCOL_WARN, domain,
               "resolve request on circ with purpose %d; dropping",
               circ->purpose);
        return 0;
      }
      connection_exit_begin_resolve(cell, TO_OR_CIRCUIT(circ));
      return 0;
    case RELAY_COMMAND_RESOLVED:
      if (conn) {
        log_fn(LOG_PROTOCOL_WARN, domain,
               "'resolved' unsupported while open. Closing circ.");
        return -END_CIRC_REASON_TORPROTOCOL;
      }
      log_info(domain,
               "'resolved' received, no conn attached anymore. Ignoring.");
      return 0;
    case RELAY_COMMAND_ESTABLISH_INTRO:
    case RELAY_COMMAND_ESTABLISH_RENDEZVOUS:
    case RELAY_COMMAND_INTRODUCE1:
    case RELAY_COMMAND_INTRODUCE2:
    case RELAY_COMMAND_INTRODUCE_ACK:
    case RELAY_COMMAND_RENDEZVOUS1:
    case RELAY_COMMAND_RENDEZVOUS2:
    case RELAY_COMMAND_INTRO_ESTABLISHED:
    case RELAY_COMMAND_RENDEZVOUS_ESTABLISHED:
      rend_process_relay_cell(circ, rh.command, rh.length,
                              cell->payload+RELAY_HEADER_SIZE);
      return 0;
  }
  log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
         "Received unknown relay command %d. Perhaps the other side is using "
         "a newer version of Tor? Dropping.",
         rh.command);
  return 0; /* for forward compatibility, don't kill the circuit */
}

uint64_t stats_n_data_cells_packaged = 0;
uint64_t stats_n_data_bytes_packaged = 0;
uint64_t stats_n_data_cells_received = 0;
uint64_t stats_n_data_bytes_received = 0;

/** While conn->inbuf has an entire relay payload of bytes on it,
 * and the appropriate package windows aren't empty, grab a cell
 * and send it down the circuit.
 *
 * Return -1 (and send a RELAY_END cell if necessary) if conn should
 * be marked for close, else return 0.
 */
int
connection_edge_package_raw_inbuf(edge_connection_t *conn, int package_partial)
{
  size_t amount_to_process, length;
  char payload[CELL_PAYLOAD_SIZE];
  circuit_t *circ;
  unsigned domain = conn->cpath_layer ? LD_APP : LD_EXIT;

  tor_assert(conn);

  if (conn->_base.marked_for_close) {
    log_warn(LD_BUG,
             "called on conn that's already marked for close at %s:%d.",
             conn->_base.marked_for_close_file, conn->_base.marked_for_close);
    return 0;
  }

repeat_connection_edge_package_raw_inbuf:

  circ = circuit_get_by_edge_conn(conn);
  if (!circ) {
    log_info(domain,"conn has no circuit! Closing.");
    conn->end_reason = END_STREAM_REASON_CANT_ATTACH;
    return -1;
  }

  if (circuit_consider_stop_edge_reading(circ, conn->cpath_layer))
    return 0;

  if (conn->package_window <= 0) {
    log_info(domain,"called with package_window %d. Skipping.",
             conn->package_window);
    connection_stop_reading(TO_CONN(conn));
    return 0;
  }

  amount_to_process = buf_datalen(conn->_base.inbuf);

  if (!amount_to_process)
    return 0;

  if (!package_partial && amount_to_process < RELAY_PAYLOAD_SIZE)
    return 0;

  if (amount_to_process > RELAY_PAYLOAD_SIZE) {
    length = RELAY_PAYLOAD_SIZE;
  } else {
    length = amount_to_process;
  }
  stats_n_data_bytes_packaged += length;
  stats_n_data_cells_packaged += 1;

  connection_fetch_from_buf(payload, length, TO_CONN(conn));

  log_debug(domain,"(%d) Packaging %d bytes (%d waiting).", conn->_base.s,
            (int)length, (int)buf_datalen(conn->_base.inbuf));

  if (connection_edge_send_command(conn, RELAY_COMMAND_DATA,
                                   payload, length) < 0 )
    /* circuit got marked for close, don't continue, don't need to mark conn */
    return 0;

  if (!conn->cpath_layer) { /* non-rendezvous exit */
    tor_assert(circ->package_window > 0);
    circ->package_window--;
  } else { /* we're an AP, or an exit on a rendezvous circ */
    tor_assert(conn->cpath_layer->package_window > 0);
    conn->cpath_layer->package_window--;
  }

  if (--conn->package_window <= 0) { /* is it 0 after decrement? */
    connection_stop_reading(TO_CONN(conn));
    log_debug(domain,"conn->package_window reached 0.");
    circuit_consider_stop_edge_reading(circ, conn->cpath_layer);
    return 0; /* don't process the inbuf any more */
  }
  log_debug(domain,"conn->package_window is now %d",conn->package_window);

  /* handle more if there's more, or return 0 if there isn't */
  goto repeat_connection_edge_package_raw_inbuf;
}

/** Called when we've just received a relay data cell, or when
 * we've just finished flushing all bytes to stream <b>conn</b>.
 *
 * If conn->outbuf is not too full, and our deliver window is
 * low, send back a suitable number of stream-level sendme cells.
 */
void
connection_edge_consider_sending_sendme(edge_connection_t *conn)
{
  circuit_t *circ;

  if (connection_outbuf_too_full(TO_CONN(conn)))
    return;

  circ = circuit_get_by_edge_conn(conn);
  if (!circ) {
    /* this can legitimately happen if the destroy has already
     * arrived and torn down the circuit */
    log_info(LD_APP,"No circuit associated with conn. Skipping.");
    return;
  }

  while (conn->deliver_window < STREAMWINDOW_START - STREAMWINDOW_INCREMENT) {
    log_debug(conn->cpath_layer?LD_APP:LD_EXIT,
              "Outbuf %d, Queueing stream sendme.",
              (int)conn->_base.outbuf_flushlen);
    conn->deliver_window += STREAMWINDOW_INCREMENT;
    if (connection_edge_send_command(conn, RELAY_COMMAND_SENDME,
                                     NULL, 0) < 0) {
      log_warn(LD_APP,"connection_edge_send_command failed. Skipping.");
      return; /* the circuit's closed, don't continue */
    }
  }
}

/** The circuit <b>circ</b> has received a circuit-level sendme
 * (on hop <b>layer_hint</b>, if we're the OP). Go through all the
 * attached streams and let them resume reading and packaging, if
 * their stream windows allow it.
 */
static void
circuit_resume_edge_reading(circuit_t *circ, crypt_path_t *layer_hint)
{

  log_debug(layer_hint?LD_APP:LD_EXIT,"resuming");

  if (CIRCUIT_IS_ORIGIN(circ))
    circuit_resume_edge_reading_helper(TO_ORIGIN_CIRCUIT(circ)->p_streams,
                                       circ, layer_hint);
  else
    circuit_resume_edge_reading_helper(TO_OR_CIRCUIT(circ)->n_streams,
                                       circ, layer_hint);
}

/** A helper function for circuit_resume_edge_reading() above.
 * The arguments are the same, except that <b>conn</b> is the head
 * of a linked list of edge streams that should each be considered.
 */
static int
circuit_resume_edge_reading_helper(edge_connection_t *conn,
                                   circuit_t *circ,
                                   crypt_path_t *layer_hint)
{
  for ( ; conn; conn=conn->next_stream) {
    if (conn->_base.marked_for_close)
      continue;
    if ((!layer_hint && conn->package_window > 0) ||
        (layer_hint && conn->package_window > 0 &&
         conn->cpath_layer == layer_hint)) {
      connection_start_reading(TO_CONN(conn));
      /* handle whatever might still be on the inbuf */
      if (connection_edge_package_raw_inbuf(conn, 1)<0) {
        /* (We already sent an end cell if possible) */
        connection_mark_for_close(TO_CONN(conn));
        continue;
      }

      /* If the circuit won't accept any more data, return without looking
       * at any more of the streams. Any connections that should be stopped
       * have already been stopped by connection_edge_package_raw_inbuf. */
      if (circuit_consider_stop_edge_reading(circ, layer_hint))
        return -1;
    }
  }
  return 0;
}

/** Check if the package window for <b>circ</b> is empty (at
 * hop <b>layer_hint</b> if it's defined).
 *
 * If yes, tell edge streams to stop reading and return 1.
 * Else return 0.
 */
static int
circuit_consider_stop_edge_reading(circuit_t *circ, crypt_path_t *layer_hint)
{
  edge_connection_t *conn = NULL;
  unsigned domain = layer_hint ? LD_APP : LD_EXIT;

  if (!layer_hint) {
    or_circuit_t *or_circ = TO_OR_CIRCUIT(circ);
    log_debug(domain,"considering circ->package_window %d",
              circ->package_window);
    if (circ->package_window <= 0) {
      log_debug(domain,"yes, not-at-origin. stopped.");
      for (conn = or_circ->n_streams; conn; conn=conn->next_stream)
        connection_stop_reading(TO_CONN(conn));
      return 1;
    }
    return 0;
  }
  /* else, layer hint is defined, use it */
  log_debug(domain,"considering layer_hint->package_window %d",
            layer_hint->package_window);
  if (layer_hint->package_window <= 0) {