code: def tcp_traceflow(frame, *, data_link):
      
      if 'TCP' in frame:
          ip = (frame['IPv4'] if 'IPv4' in frame else frame['IPv6']).info
          tcp = frame['TCP'].info
          data = dict(
              protocol=data_link,                     # data link type from global header
              index=frame.info.number,                # frame number
              frame=frame.info,                       # extracted frame info
              syn=tcp.flags.syn,                      # TCP synchronise (SYN) flag
              fin=tcp.flags.fin,                      # TCP finish (FIN) flag
              src=ip.src,                             # source IP
              dst=ip.dst,                             # destination IP
              srcport=tcp.srcport,                    # TCP source port
              dstport=tcp.dstport,                    # TCP destination port
              timestamp=frame.info.time_epoch,        # frame timestamp
          )
          return True, data
      return False, None
docs: Trace packet flow for TCP.