relay.c

  bool dir_stream = false;
  
  if (relay_command == RELAY_COMMAND_DATA || relay_command == RELAY_COMMAND_BEGIN_DIR) {
    if (!circ->dir_streams) {
      circ->dir_streams = smartlist_new();  
    }
    
    /* Try to find the list entry for this circuit and stream ID */
    SMARTLIST_FOREACH_BEGIN(circ->dir_streams, streamid_t *, sid) {
      if (*sid == stream_id) {
        dir_stream = true;
      }
    } SMARTLIST_FOREACH_END(sid);
  }
  
  if (!dir_stream) {
    /* If we're sending a data cell through a circuit, we want to note the time
     * to determine the length of gaps in the stream */ 
    if (relay_command == RELAY_COMMAND_DATA) {
      char log_message[100], temp[32];
      sprintf(log_message, "cell from %s", cell_direction == CELL_DIRECTION_OUT ? "entry" : "exit");
    
      if (!circ->time_of_last_cell) {
        circ->time_of_last_cell = tor_malloc_zero(sizeof(struct timespec));
        clock_gettime(CLOCK_REALTIME, circ->time_of_last_cell);
      } else {
        struct timespec current_time, gap_length;
        clock_gettime(CLOCK_REALTIME, &current_time);
      
        if (current_time.tv_sec < circ->time_of_last_cell->tv_sec) {
          gap_length.tv_sec = 0;     
          gap_length.tv_nsec = 0;
        } else {
          gap_length.tv_sec = current_time.tv_sec -  circ->time_of_last_cell->tv_sec;
          gap_length.tv_nsec = current_time.tv_nsec -  circ->time_of_last_cell->tv_nsec;
        }

        while(gap_length.tv_nsec < 0) {
          gap_length.tv_sec--;
          gap_length.tv_nsec += 1000000000;
        }

        sprintf(temp, " %lu.%.3d", gap_length.tv_sec, (int)(gap_length.tv_nsec / 1000000));
        strcat(log_message, temp);
        circ->time_of_last_cell = &current_time;
      }
      
      log(LOG_NOTICE, LD_GENERAL, log_message);
    } else if (relay_command == RELAY_COMMAND_BEGIN_DIR ) { 
      smartlist_add(circ->dir_streams, &stream_id);
      log(LOG_NOTICE, LD_GENERAL, "Stream #%d now ignored", stream_id);
    }
  } else {
    log(LOG_NOTICE, LD_GENERAL, "Ignored cell from stream #%d", stream_id);
  }