implement sending of truncated ConnectionIDs

handshake/connection_parameters_manager.go

@@ -39,7 +39,7 @@ func (h *ConnectionParametersManager) SetFromMap(params map[Tag][]byte) error {
 	h.mutex.Lock()
 	for key, value := range params {
 		switch key {
-		case TagSFCW, TagCFCW, TagICSL, TagMSPC:
+		case TagSFCW, TagCFCW, TagICSL, TagMSPC, TagTCID:
 			h.params[key] = value
 		}
 	}
@@ -61,10 +61,10 @@ func (h *ConnectionParametersManager) GetRawValue(tag Tag) ([]byte, error) {
 
 // GetSHLOMap gets all values (except crypto values) needed for the SHLO
 func (h *ConnectionParametersManager) GetSHLOMap() map[Tag][]byte {
-	// Since GetSHLOMap is only called from the crypto stream, and changes to
-	// the params are only made by the crypto stream itself, there is no data race
-	// here, and we need not copy the map.
-	return h.params
+	return map[Tag][]byte{
+		TagICSL: []byte{0x1e, 0x00, 0x00, 0x00}, //30
+		TagMSPC: []byte{0x64, 0x00, 0x00, 0x00}, //100
+	}
 }
 
 // GetStreamFlowControlWindow gets the size of the stream-level flow control window
@@ -96,3 +96,23 @@ func (h *ConnectionParametersManager) GetIdleConnectionStateLifetime() time.Dura
 	}
 	return time.Duration(binary.LittleEndian.Uint32(rawValue)) * time.Second
 }
+
+// TruncateConnectionID determines if the client requests truncated ConnectionIDs
+func (h *ConnectionParametersManager) TruncateConnectionID() bool {
+	rawValue, err := h.GetRawValue(TagTCID)
+	if err != nil {
+		return false
+	}
+
+	var value uint32
+	buf := bytes.NewBuffer(rawValue)
+	err = binary.Read(buf, binary.LittleEndian, &value)
+	if err != nil {
+		return false
+	}
+
+	if value == 0 {
+		return true
+	}
+	return false
+}

handshake/connection_parameters_manager_test.go

@@ -39,6 +39,20 @@ var _ = Describe("ConnectionsParameterManager", func() {
 		Expect(entryMap).To(HaveKey(TagMSPC))
 	})
 
+	Context("Truncated connection IDs", func() {
+		It("does not send truncated connection IDs if the TCID tag is missing", func() {
+			Expect(cpm.TruncateConnectionID()).To(BeFalse())
+		})
+
+		It("reads the tag for truncated connection IDs", func() {
+			values := map[Tag][]byte{
+				TagTCID: []byte{0, 0, 0, 0},
+			}
+			cpm.SetFromMap(values)
+			Expect(cpm.TruncateConnectionID()).To(BeTrue())
+		})
+	})
+
 	Context("flow control", func() {
 		It("has the correct default flow control window", func() {
 			val, err := cpm.GetStreamFlowControlWindow()

packet_packer.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/lucas-clemente/quic-go/crypto"
 	"github.com/lucas-clemente/quic-go/frames"
+	"github.com/lucas-clemente/quic-go/handshake"
 	"github.com/lucas-clemente/quic-go/protocol"
 	"github.com/lucas-clemente/quic-go/utils"
 )
@@ -20,6 +21,7 @@ type packedPacket struct {
 type packetPacker struct {
 	connectionID                protocol.ConnectionID
 	aead                        crypto.AEAD
+	connectionParametersManager *handshake.ConnectionParametersManager
 
 	streamFrameQueue StreamFrameQueue
 
@@ -68,6 +70,7 @@ func (p *packetPacker) PackPacket(stopWaitingFrame *frames.StopWaitingFrame, con
 	responsePublicHeader := PublicHeader{
 		ConnectionID:         p.connectionID,
 		PacketNumber:         currentPacketNumber,
+		TruncateConnectionID: p.connectionParametersManager.TruncateConnectionID(),
 	}
 	if err := responsePublicHeader.WritePublicHeader(&raw); err != nil {
 		return nil, err

packet_packer_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/lucas-clemente/quic-go/crypto"
 	"github.com/lucas-clemente/quic-go/frames"
+	"github.com/lucas-clemente/quic-go/handshake"
 	"github.com/lucas-clemente/quic-go/protocol"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -17,7 +18,7 @@ var _ = Describe("Packet packer", func() {
 
 	BeforeEach(func() {
 		aead := &crypto.NullAEAD{}
-		packer = &packetPacker{aead: aead}
+		packer = &packetPacker{aead: aead, connectionParametersManager: handshake.NewConnectionParamatersManager()}
 	})
 
 	It("returns nil when no packet is queued", func() {

public_header.go

@@ -21,6 +21,7 @@ type PublicHeader struct {
 	VersionFlag          bool
 	ResetFlag            bool
 	ConnectionID         protocol.ConnectionID
+	TruncateConnectionID bool
 	VersionNumber        protocol.VersionNumber
 	QuicVersion          uint32
 	PacketNumberLen      uint8
@@ -29,7 +30,7 @@ type PublicHeader struct {
 
 // WritePublicHeader writes a public header
 func (h *PublicHeader) WritePublicHeader(b *bytes.Buffer) error {
-	publicFlagByte := uint8(0x3c)
+	publicFlagByte := uint8(0x34)
 	if h.VersionFlag && h.ResetFlag {
 		return errResetAndVersionFlagSet
 	}
@@ -39,9 +40,16 @@ func (h *PublicHeader) WritePublicHeader(b *bytes.Buffer) error {
 	if h.ResetFlag {
 		publicFlagByte |= 0x02
 	}
+	if !h.TruncateConnectionID {
+		publicFlagByte |= 0x08
+	}
 
 	b.WriteByte(publicFlagByte)
-	utils.WriteUint64(b, uint64(h.ConnectionID)) // TODO: Send shorter connection id if possible
+
+	if !h.TruncateConnectionID {
+		utils.WriteUint64(b, uint64(h.ConnectionID))
+	}
+
 	utils.WriteUint48(b, uint64(h.PacketNumber)) // TODO: Send shorter packet number if possible
 	return nil
 }

public_header_test.go

@@ -125,5 +125,18 @@ var _ = Describe("Public Header", func() {
 			Expect(err).To(HaveOccurred())
 			Expect(err).To(Equal(errResetAndVersionFlagSet))
 		})
+
+		It("truncates the connection ID", func() {
+			b := &bytes.Buffer{}
+			publicHeader := PublicHeader{
+				ConnectionID:         0x4cfa9f9b668619f6,
+				TruncateConnectionID: true,
+			}
+			err := publicHeader.WritePublicHeader(b)
+			Expect(err).ToNot(HaveOccurred())
+			firstByte, _ := b.ReadByte()
+			Expect(firstByte & 0x08).To(BeZero())
+			Expect(b.Bytes()).ToNot(ContainSubstring(string([]byte{0xf6, 0x19, 0x86, 0x66, 0x9b, 0x9f, 0xfa, 0x4c})))
+		})
 	})
 })

session.go

@@ -94,7 +94,7 @@ func NewSession(conn connection, v protocol.VersionNumber, connectionID protocol
 		}
 	}()
 
-	session.packer = &packetPacker{aead: cryptoSetup, connectionID: connectionID}
+	session.packer = &packetPacker{aead: cryptoSetup, connectionParametersManager: session.connectionParametersManager, connectionID: connectionID}
 	session.unpacker = &packetUnpacker{aead: cryptoSetup}
 
 	return session

session_test.go

@@ -352,6 +352,7 @@ var _ = Describe("Session", func() {
 		session.connectionParametersManager.SetFromMap(map[handshake.Tag][]byte{
 			handshake.TagICSL: {0, 0, 0, 0},
 		})
+		session.packer.connectionParametersManager = session.connectionParametersManager
 		session.Run() // Would normally not return
 		Expect(conn.written[0]).To(ContainSubstring("No recent network activity."))
 		close(done)