void per_packet(libtrace_packet **pkt)
{
  trace_defrag_t res = trace_defrag_push_packet(*pkt);
  libtrace_packet *p = *pkt;
 
  do {
    switch (res) {
      case TRACE_DEFRAG_UNNEEDED:
          /* code here */
          printf("%d\n",trace_get_capture_length(p));
          break;
      case TRACE_DEFRAG_REASSEMBLED:
          /* code here */
          printf("%d\n",trace_get_capture_length(p));
          trace_destroy_packet(p);
          break;
      case TRACE_DEFRAG_TIMED_OUT:
          printf("Reassembly timed out\n");
          trace_destroy_packet(p);
          break;
      case TRACE_DEFRAG_ALTERNATE:
          trace_destroy_packet(p);
          break;
      case TRACE_DEFRAG_WAITING:
          pkt=NULL;
          break;
      default:
          assert(0);
    }
  } while ( p = trace_defrag_pop_packet(defrag, &res));
  if (!*pkt)
    *pkt=trace_create_packet();
}