if packet_num == 1 && frame_size == tail_size {
vstr.start_slice(num_pkts, frame_size as usize, self.slice_buf.as_slice());
} else {
if packet_num == 1 && frame_size == tail_size {
vstr.start_slice(num_pkts, frame_size as usize, self.slice_buf.as_slice());
} else {