code: func (b IPv4) IsValid(pktSize int) bool {
  	if len(b) < IPv4MinimumSize {
  		return false
  	}
  
  	hlen := int(b.HeaderLength())
  	tlen := int(b.TotalLength())
  	if hlen > tlen || tlen > pktSize {
  		return false
  	}
  
  	return true
  }
docs: // IsValid performs basic validation on the packet.