package header

import "netstack/tcpip"

const (
	udpSrcPort  = 0
	udpDstPort  = 2
	udpLength   = 4
	udpChecksum = 6
)

// UDPFields contains the fields of a UDP packet. It is used to describe the
// fields of a packet that needs to be encoded.
// udp 首部字段
type UDPFields struct {
	// SrcPort is the "source port" field of a UDP packet.
	SrcPort uint16

	// DstPort is the "destination port" field of a UDP packet.
	DstPort uint16

	// Length is the "length" field of a UDP packet.
	Length uint16

	// Checksum is the "checksum" field of a UDP packet.
	Checksum uint16
}

// UDP represents a UDP header stored in a byte array.
type UDP []byte

const (
	// UDPMinimumSize is the minimum size of a valid UDP packet.
	UDPMinimumSize = 8

	// UDPProtocolNumber is UDP's transport protocol number.
	UDPProtocolNumber tcpip.TransportProtocolNumber = 17
)