252 lines
6.9 KiB
Go
252 lines
6.9 KiB
Go
package wire
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/internal/utils"
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)
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// ParseConnectionID parses the destination connection ID of a packet.
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// It uses the data slice for the connection ID.
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// That means that the connection ID must not be used after the packet buffer is released.
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func ParseConnectionID(data []byte, shortHeaderConnIDLen int) (protocol.ConnectionID, error) {
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if len(data) == 0 {
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return nil, io.EOF
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}
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isLongHeader := data[0]&0x80 > 0
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if !isLongHeader {
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if len(data) < shortHeaderConnIDLen+1 {
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return nil, io.EOF
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}
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return protocol.ConnectionID(data[1 : 1+shortHeaderConnIDLen]), nil
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}
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if len(data) < 6 {
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return nil, io.EOF
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}
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destConnIDLen, _ := decodeConnIDLen(data[5])
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if len(data) < 6+destConnIDLen {
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return nil, io.EOF
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}
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return protocol.ConnectionID(data[6 : 6+destConnIDLen]), nil
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}
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// IsVersionNegotiationPacket says if this is a version negotiation packet
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func IsVersionNegotiationPacket(b []byte) bool {
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if len(b) < 5 {
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return false
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}
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return b[0]&0x80 > 0 && b[1] == 0 && b[2] == 0 && b[3] == 0 && b[4] == 0
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}
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var errUnsupportedVersion = errors.New("unsupported version")
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// The Header is the version independent part of the header
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type Header struct {
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Version protocol.VersionNumber
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SrcConnectionID protocol.ConnectionID
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DestConnectionID protocol.ConnectionID
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IsLongHeader bool
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Type protocol.PacketType
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Length protocol.ByteCount
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Token []byte
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SupportedVersions []protocol.VersionNumber // sent in a Version Negotiation Packet
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OrigDestConnectionID protocol.ConnectionID // sent in the Retry packet
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typeByte byte
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parsedLen protocol.ByteCount // how many bytes were read while parsing this header
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}
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// ParsePacket parses a packet.
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// If the packet has a long header, the packet is cut according to the length field.
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// If we understand the version, the packet is header up unto the packet number.
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// Otherwise, only the invariant part of the header is parsed.
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func ParsePacket(data []byte, shortHeaderConnIDLen int) (*Header, []byte /* packet data */, []byte /* rest */, error) {
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hdr, err := parseHeader(bytes.NewReader(data), shortHeaderConnIDLen)
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if err != nil {
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if err == errUnsupportedVersion {
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return hdr, nil, nil, nil
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}
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return nil, nil, nil, err
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}
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var rest []byte
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if hdr.IsLongHeader {
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if protocol.ByteCount(len(data)) < hdr.ParsedLen()+hdr.Length {
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return nil, nil, nil, fmt.Errorf("packet length (%d bytes) is smaller than the expected length (%d bytes)", len(data)-int(hdr.ParsedLen()), hdr.Length)
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}
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packetLen := int(hdr.ParsedLen() + hdr.Length)
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rest = data[packetLen:]
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data = data[:packetLen]
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}
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return hdr, data, rest, nil
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}
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// ParseHeader parses the header.
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// For short header packets: up to the packet number.
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// For long header packets:
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// * if we understand the version: up to the packet number
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// * if not, only the invariant part of the header
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func parseHeader(b *bytes.Reader, shortHeaderConnIDLen int) (*Header, error) {
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startLen := b.Len()
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h, err := parseHeaderImpl(b, shortHeaderConnIDLen)
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if err != nil {
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return h, err
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}
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h.parsedLen = protocol.ByteCount(startLen - b.Len())
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return h, err
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}
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func parseHeaderImpl(b *bytes.Reader, shortHeaderConnIDLen int) (*Header, error) {
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typeByte, err := b.ReadByte()
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if err != nil {
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return nil, err
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}
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h := &Header{
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typeByte: typeByte,
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IsLongHeader: typeByte&0x80 > 0,
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}
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if !h.IsLongHeader {
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if h.typeByte&0x40 == 0 {
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return nil, errors.New("not a QUIC packet")
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}
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if err := h.parseShortHeader(b, shortHeaderConnIDLen); err != nil {
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return nil, err
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}
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return h, nil
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}
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return h, h.parseLongHeader(b)
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}
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func (h *Header) parseShortHeader(b *bytes.Reader, shortHeaderConnIDLen int) error {
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var err error
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h.DestConnectionID, err = protocol.ReadConnectionID(b, shortHeaderConnIDLen)
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return err
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}
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func (h *Header) parseLongHeader(b *bytes.Reader) error {
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v, err := utils.BigEndian.ReadUint32(b)
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if err != nil {
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return err
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}
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h.Version = protocol.VersionNumber(v)
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if h.Version != 0 && h.typeByte&0x40 == 0 {
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return errors.New("not a QUIC packet")
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}
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connIDLenByte, err := b.ReadByte()
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if err != nil {
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return err
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}
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dcil, scil := decodeConnIDLen(connIDLenByte)
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h.DestConnectionID, err = protocol.ReadConnectionID(b, dcil)
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if err != nil {
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return err
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}
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h.SrcConnectionID, err = protocol.ReadConnectionID(b, scil)
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if err != nil {
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return err
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}
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if h.Version == 0 {
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return h.parseVersionNegotiationPacket(b)
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}
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// If we don't understand the version, we have no idea how to interpret the rest of the bytes
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if !protocol.IsSupportedVersion(protocol.SupportedVersions, h.Version) {
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return errUnsupportedVersion
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}
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switch (h.typeByte & 0x30) >> 4 {
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case 0x0:
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h.Type = protocol.PacketTypeInitial
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case 0x1:
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h.Type = protocol.PacketType0RTT
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case 0x2:
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h.Type = protocol.PacketTypeHandshake
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case 0x3:
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h.Type = protocol.PacketTypeRetry
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}
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if h.Type == protocol.PacketTypeRetry {
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odcil := decodeSingleConnIDLen(h.typeByte & 0xf)
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h.OrigDestConnectionID, err = protocol.ReadConnectionID(b, odcil)
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if err != nil {
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return err
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}
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h.Token = make([]byte, b.Len())
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if _, err := io.ReadFull(b, h.Token); err != nil {
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return err
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}
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return nil
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}
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if h.Type == protocol.PacketTypeInitial {
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tokenLen, err := utils.ReadVarInt(b)
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if err != nil {
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return err
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}
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if tokenLen > uint64(b.Len()) {
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return io.EOF
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}
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h.Token = make([]byte, tokenLen)
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if _, err := io.ReadFull(b, h.Token); err != nil {
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return err
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}
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}
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pl, err := utils.ReadVarInt(b)
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if err != nil {
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return err
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}
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h.Length = protocol.ByteCount(pl)
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return nil
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}
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func (h *Header) parseVersionNegotiationPacket(b *bytes.Reader) error {
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if b.Len() == 0 {
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return errors.New("Version Negoation packet has empty version list")
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}
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if b.Len()%4 != 0 {
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return errors.New("Version Negotation packet has a version list with an invalid length")
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}
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h.SupportedVersions = make([]protocol.VersionNumber, b.Len()/4)
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for i := 0; b.Len() > 0; i++ {
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v, err := utils.BigEndian.ReadUint32(b)
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if err != nil {
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return err
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}
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h.SupportedVersions[i] = protocol.VersionNumber(v)
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}
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return nil
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}
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// ParsedLen returns the number of bytes that were consumed when parsing the header
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func (h *Header) ParsedLen() protocol.ByteCount {
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return h.parsedLen
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}
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// ParseExtended parses the version dependent part of the header.
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// The Reader has to be set such that it points to the first byte of the header.
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func (h *Header) ParseExtended(b *bytes.Reader, ver protocol.VersionNumber) (*ExtendedHeader, error) {
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return h.toExtendedHeader().parse(b, ver)
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}
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func (h *Header) toExtendedHeader() *ExtendedHeader {
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return &ExtendedHeader{Header: *h}
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}
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func decodeConnIDLen(enc byte) (int /*dest conn id len*/, int /*src conn id len*/) {
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return decodeSingleConnIDLen(enc >> 4), decodeSingleConnIDLen(enc & 0xf)
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}
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func decodeSingleConnIDLen(enc uint8) int {
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if enc == 0 {
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return 0
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}
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return int(enc) + 3
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}
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