stun

type AttributeValue interface {
	Bytes() []byte
}

type MappedAddressAttr struct {
	Family  byte
	Port    int
	Address net.IP
}

type RawAttr struct {
	Data []byte
}

type StunAttribute struct {
	// 16 bit Type
	Type uint16

	// 16 bit length
	Length int

	// Variable Length Attribute
	Attr AttributeValue
}

type StunMessage struct {
	// 14 bit message type: 12 bit Method + 2 bit Class encoding
	//	+--+--+-+-+-+-+-+-+-+-+-+-+-+-+
	//	|M |M |M|M|M|C|M|M|M|C|M|M|M|M|
	//	|11|10|9|8|7|1|6|5|4|0|3|2|1|0|
	//	+--+--+-+-+-+-+-+-+-+-+-+-+-+-+
	Method uint16
	Class  byte

	// Message Length: 16 bits
	Length int

	// Magic Cookie: always 0x2112A442 in network order
	Cookie []byte

	// Transaction ID: Random 96 bits
	TransID []byte

	Attrs []StunAttribute
}