packet

type ARP struct {
	HType    ARPType
	PType    EtherType
	HLen     byte
	PLen     byte
	Oper     ARPOpCode
	SourceHW net.HardwareAddr
	SourceIP netip.Addr
	DestHW   net.HardwareAddr
	DestIP   netip.Addr
	PacketBytes
}

type ARPOpCode uint16

type ARPType uint16

type EtherType uint16

type Ethernet struct {
	PacketBytes
	Destination  net.HardwareAddr
	Source       net.HardwareAddr
	EthernetType EtherType
}

type IPv4 struct {
	IHL            uint8
	DSCP           uint8
	ECN            uint8
	TotalLen       uint16
	ID             uint16
	Flags          uint8
	FragOffset     uint16
	Hops           uint8
	Proto          uint8
	HeaderChecksum uint16
	Source         netip.Addr
	Destination    netip.Addr
	// Todo: options
	PacketBytes
}

type Layer interface {
	// Type returns the layer type.
	Type() LayerType

	// GetContents() returns the entire layer contents in bytes.
	GetContents() []byte

	// GetPayload() returns the layer payload. That is Contents()[hdrSize:]
	GetPayload() []byte
}

type LayerType uint8

type Packet struct {
	// Link contains the link-layer representation of the packet.
	Link *Ethernet

	// Network contains the network-layer representation of the packet.
	Network Layer
}

type PacketBytes struct {
	// Contents contains the entire packet's bytes.
	Contents []byte

	// Payload contains the packet's payload. That is, the contents minus the
	// packet header.
	Payload []byte
}

type TCP struct {
	Payload []byte
}