code: func (s *sender) pCount(seg *segment) int {
  	size := seg.data.Size()
  	if size == 0 {
  		return 1
  	}
  
  	return (size-1)/s.maxPayloadSize + 1
  }
docs: // pCount returns the number of packets in the segment. Due to GSO, a segment
  // can be composed of multiple packets.