add the exhaustive linter

.golangci.yml

@@ -20,6 +20,7 @@ linters:
     - asciicheck
     - deadcode
     - depguard
+    - exhaustive
     - exportloopref
     - goconst
     - goimports

crypto_stream_manager.go

@@ -35,6 +35,7 @@ func newCryptoStreamManager(
 
 func (m *cryptoStreamManager) HandleCryptoFrame(frame *wire.CryptoFrame, encLevel protocol.EncryptionLevel) (bool /* encryption level changed */, error) {
 	var str cryptoStream
+	//nolint:exhaustive // CRYPTO frames cannot be sent in 0-RTT packets.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		str = m.initialStream

fuzzing/handshake/fuzz.go

@@ -205,6 +205,7 @@ func toEncryptionLevel(n uint8) protocol.EncryptionLevel {
 }
 
 func maxEncLevel(cs handshake.CryptoSetup, encLevel protocol.EncryptionLevel) protocol.EncryptionLevel {
+	//nolint:exhaustive
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		return protocol.EncryptionInitial

integrationtests/self/handshake_drop_test.go

@@ -203,6 +203,7 @@ var _ = Describe("Handshake drop tests", func() {
 											var incoming, outgoing int32
 											startListenerAndProxy(func(d quicproxy.Direction, _ []byte) bool {
 												var p int32
+												//nolint:exhaustive
 												switch d {
 												case quicproxy.DirectionIncoming:
 													p = atomic.AddInt32(&incoming, 1)
@@ -218,6 +219,7 @@ var _ = Describe("Handshake drop tests", func() {
 											var incoming, outgoing int32
 											startListenerAndProxy(func(d quicproxy.Direction, _ []byte) bool {
 												var p int32
+												//nolint:exhaustive
 												switch d {
 												case quicproxy.DirectionIncoming:
 													p = atomic.AddInt32(&incoming, 1)

integrationtests/self/packetization_test.go

@@ -37,6 +37,7 @@ var _ = Describe("Packetization", func() {
 		proxy, err = quicproxy.NewQuicProxy("localhost:0", &quicproxy.Opts{
 			RemoteAddr: serverAddr,
 			DelayPacket: func(dir quicproxy.Direction, _ []byte) time.Duration {
+				//nolint:exhaustive
 				switch dir {
 				case quicproxy.DirectionIncoming:
 					atomic.AddUint32(&incoming, 1)

internal/ackhandler/received_packet_handler.go

@@ -67,6 +67,7 @@ func (h *receivedPacketHandler) ReceivedPacket(
 }
 
 func (h *receivedPacketHandler) DropPackets(encLevel protocol.EncryptionLevel) {
+	//nolint:exhaustive // 1-RTT packet number space is never dropped.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		h.initialPackets = nil
@@ -94,6 +95,7 @@ func (h *receivedPacketHandler) GetAlarmTimeout() time.Time {
 
 func (h *receivedPacketHandler) GetAckFrame(encLevel protocol.EncryptionLevel, onlyIfQueued bool) *wire.AckFrame {
 	var ack *wire.AckFrame
+	//nolint:exhaustive // 0-RTT packets can't contain ACK frames.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		if h.initialPackets != nil {

internal/ackhandler/sent_packet_handler.go

@@ -156,6 +156,7 @@ func (h *sentPacketHandler) dropPackets(encLevel protocol.EncryptionLevel) {
 		})
 	}
 	// drop the packet history
+	//nolint:exhaustive // Not every packet number space can be dropped.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		h.initialPackets = nil
@@ -629,6 +630,7 @@ func (h *sentPacketHandler) onVerifiedLossDetectionTimeout() error {
 			h.tracer.UpdatedPTOCount(h.ptoCount)
 		}
 		h.numProbesToSend += 2
+		//nolint:exhaustive // We never arm a PTO timer for 0-RTT packets.
 		switch encLevel {
 		case protocol.EncryptionInitial:
 			h.ptoMode = SendPTOInitial

internal/handshake/crypto_setup.go

@@ -612,6 +612,7 @@ func (h *cryptoSetup) WriteRecord(p []byte) (int, error) {
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
 
+	//nolint:exhaustive // LS records can only be written for Initial and Handshake.
 	switch h.writeEncLevel {
 	case protocol.EncryptionInitial:
 		// assume that the first WriteRecord call contains the ClientHello

internal/wire/extended_header.go

@@ -128,6 +128,7 @@ func (h *ExtendedHeader) Write(b *bytes.Buffer, ver protocol.VersionNumber) erro
 
 func (h *ExtendedHeader) writeLongHeader(b *bytes.Buffer, _ protocol.VersionNumber) error {
 	var packetType uint8
+	//nolint:exhaustive
 	switch h.Type {
 	case protocol.PacketTypeInitial:
 		packetType = 0x0
@@ -151,6 +152,7 @@ func (h *ExtendedHeader) writeLongHeader(b *bytes.Buffer, _ protocol.VersionNumb
 	b.WriteByte(uint8(h.SrcConnectionID.Len()))
 	b.Write(h.SrcConnectionID.Bytes())
 
+	//nolint:exhaustive
 	switch h.Type {
 	case protocol.PacketTypeRetry:
 		b.Write(h.Token)

internal/wire/transport_parameters.go

@@ -268,6 +268,7 @@ func (p *TransportParameters) readNumericTransportParameter(
 	if remainingLen-r.Len() != expectedLen {
 		return fmt.Errorf("inconsistent transport parameter length for %d", paramID)
 	}
+	//nolint:exhaustive // This only covers the numeric transport parameters.
 	switch paramID {
 	case initialMaxStreamDataBidiLocalParameterID:
 		p.InitialMaxStreamDataBidiLocal = protocol.ByteCount(val)

packet_packer.go

@@ -60,6 +60,7 @@ func (p *packetContents) EncryptionLevel() protocol.EncryptionLevel {
 	if !p.header.IsLongHeader {
 		return protocol.Encryption1RTT
 	}
+	//nolint:exhaustive // Will never be called for Retry packets (and they don't have encrypted data).
 	switch p.header.Type {
 	case protocol.PacketTypeInitial:
 		return protocol.EncryptionInitial
@@ -410,6 +411,7 @@ func (p *packetPacker) maybeAppendCryptoPacket(buffer *packetBuffer, maxPacketSi
 	var sealer sealer
 	var s cryptoStream
 	var hasRetransmission bool
+	//nolint:exhaustive // Initial and Handshake are the only two encryption levels here.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		s = p.initialStream
@@ -452,6 +454,7 @@ func (p *packetPacker) maybeAppendCryptoPacket(buffer *packetBuffer, maxPacketSi
 	if hasRetransmission {
 		for {
 			var f wire.Frame
+			//nolint:exhaustive // 0-RTT packets can't contain any retransmission.s
 			switch encLevel {
 			case protocol.EncryptionInitial:
 				f = p.retransmissionQueue.GetInitialFrame(remainingLen)
@@ -567,6 +570,7 @@ func (p *packetPacker) MaybePackProbePacket(encLevel protocol.EncryptionLevel) (
 	var contents *packetContents
 	var err error
 	buffer := getPacketBuffer()
+	//nolint:exhaustive Probe packets are never sent for 0-RTT.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		contents, err = p.maybeAppendCryptoPacket(buffer, p.maxPacketSize, protocol.EncryptionInitial)
@@ -649,6 +653,7 @@ func (p *packetPacker) getLongHeader(encLevel protocol.EncryptionLevel) *wire.Ex
 	hdr.PacketNumber = pn
 	hdr.PacketNumberLen = pnLen
 
+	//nolint:exhaustive // 1-RTT packets are not long header packets.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		hdr.Type = protocol.PacketTypeInitial

packet_unpacker.go

@@ -65,6 +65,7 @@ func (u *packetUnpacker) Unpack(hdr *wire.Header, rcvTime time.Time, data []byte
 	var encLevel protocol.EncryptionLevel
 	var extHdr *wire.ExtendedHeader
 	var decrypted []byte
+	//nolint:exhaustive // Retry packets can't be unpacked.
 	switch hdr.Type {
 	case protocol.PacketTypeInitial:
 		encLevel = protocol.EncryptionInitial

quictrace/tracer.go

@@ -124,6 +124,8 @@ func getEncryptionLevel(encLevel protocol.EncryptionLevel) *pb.EncryptionLevel {
 		enc = pb.EncryptionLevel_ENCRYPTION_INITIAL
 	case protocol.EncryptionHandshake:
 		enc = pb.EncryptionLevel_ENCRYPTION_HANDSHAKE
+	case protocol.Encryption0RTT:
+		enc = pb.EncryptionLevel_ENCRYPTION_0RTT
 	case protocol.Encryption1RTT:
 		enc = pb.EncryptionLevel_ENCRYPTION_1RTT
 	}

retransmission_queue.go

@@ -117,6 +117,7 @@ func (q *retransmissionQueue) GetAppDataFrame(maxLen protocol.ByteCount) wire.Fr
 }
 
 func (q *retransmissionQueue) DropPackets(encLevel protocol.EncryptionLevel) {
+	//nolint:exhaustive // Can only drop Initial and Handshake packet number space.
 	switch encLevel {
 	case protocol.EncryptionInitial:
 		q.initial = nil

session.go

@@ -1515,6 +1515,7 @@ func (s *session) sendProbePacket(encLevel protocol.EncryptionLevel) error {
 		}
 	}
 	if packet == nil {
+		//nolint:exhaustive // Cannot send probe packets for 0-RTT.
 		switch encLevel {
 		case protocol.EncryptionInitial:
 			s.retransmissionQueue.AddInitial(&wire.PingFrame{})

session_test.go

@@ -1278,6 +1278,7 @@ var _ = Describe("Session", func() {
 				var getFrame func(protocol.ByteCount) wire.Frame
 
 				BeforeEach(func() {
+					//nolint:exhaustive
 					switch encLevel {
 					case protocol.EncryptionInitial:
 						sendMode = ackhandler.SendPTOInitial