TUN-5299: Send/receive QUIC datagram from edge and proxy to origin as UDP

connection/quic.go

@@ -14,6 +14,7 @@ import (
 	"github.com/lucas-clemente/quic-go"
 	"github.com/pkg/errors"
 	"github.com/rs/zerolog"
+	"golang.org/x/sync/errgroup"
 
 	quicpogs "github.com/cloudflare/cloudflared/quic"
 	tunnelpogs "github.com/cloudflare/cloudflared/tunnelrpc/pogs"
@@ -25,17 +26,16 @@ const (
 	// HTTPMethodKey is used to get or set http method in QUIC ALPN if the underlying proxy connection type is HTTP.
 	HTTPMethodKey = "HttpMethod"
 	// HTTPHostKey is used to get or set http Method in QUIC ALPN if the underlying proxy connection type is HTTP.
-	HTTPHostKey = "HttpHost"
+	HTTPHostKey          = "HttpHost"
+	MaxDatagramFrameSize = 1220
 )
 
 // QUICConnection represents the type that facilitates Proxying via QUIC streams.
 type QUICConnection struct {
-	session           quic.Session
-	logger            *zerolog.Logger
-	httpProxy         OriginProxy
-	gracefulShutdownC <-chan struct{}
-	stoppedGracefully bool
-	udpSessions       *udpSessions
+	session     quic.Session
+	logger      *zerolog.Logger
+	httpProxy   OriginProxy
+	udpSessions *udpSessions
 }
 
 // NewQUICConnection returns a new instance of QUICConnection.
@@ -49,6 +49,12 @@ func NewQUICConnection(
 	controlStreamHandler ControlStreamHandler,
 	observer *Observer,
 ) (*QUICConnection, error) {
+	localIP, err := GetLocalIP()
+	if err != nil {
+		return nil, err
+	}
+	observer.log.Info().Msgf("UDP proxy will use %s as packet source IP", localIP)
+	udpSessions := newUDPSessions(localIP)
 	session, err := quic.DialAddr(edgeAddr.String(), tlsConfig, quicConfig)
 	if err != nil {
 		return nil, fmt.Errorf("failed to dial to edge: %w", err)
@@ -69,15 +75,24 @@ func NewQUICConnection(
 		session:     session,
 		httpProxy:   httpProxy,
 		logger:      observer.log,
-		udpSessions: newUDPSessions(),
+		udpSessions: udpSessions,
 	}, nil
 }
 
 // Serve starts a QUIC session that begins accepting streams.
 func (q *QUICConnection) Serve(ctx context.Context) error {
-	ctx, cancel := context.WithCancel(ctx)
-	defer cancel()
+	errGroup, ctx := errgroup.WithContext(ctx)
+	errGroup.Go(func() error {
+		return q.listenEdgeDatagram()
+	})
 
+	errGroup.Go(func() error {
+		return q.acceptStream(ctx)
+	})
+	return errGroup.Wait()
+}
+
+func (q *QUICConnection) acceptStream(ctx context.Context) error {
 	for {
 		stream, err := q.session.AcceptStream(ctx)
 		if err != nil {
@@ -96,6 +111,26 @@ func (q *QUICConnection) Serve(ctx context.Context) error {
 	}
 }
 
+// listenEdgeDatagram listens for datagram from edge, parse the session ID and find the UDPConn to send the payload
+func (q *QUICConnection) listenEdgeDatagram() error {
+	for {
+		msg, err := q.session.ReceiveMessage()
+		if err != nil {
+			return err
+		}
+		go func(msg []byte) {
+			sessionID, msgWithoutID, err := quicpogs.ExtractSessionID(msg)
+			if err != nil {
+				q.logger.Err(err).Msg("Failed to parse session ID from datagram")
+				return
+			}
+			if err := q.udpSessions.send(sessionID, msgWithoutID); err != nil {
+				q.logger.Err(err).Msg("Failed to send UDP to origin")
+			}
+		}(msg)
+	}
+}
+
 // Close closes the session with no errors specified.
 func (q *QUICConnection) Close() {
 	q.session.CloseWithError(0, "")
@@ -120,7 +155,7 @@ func (q *QUICConnection) handleStream(stream quic.Stream) error {
 		}
 		return q.handleRPCStream(rpcStream)
 	default:
-		return fmt.Errorf("Unknown protocol %v", signature)
+		return fmt.Errorf("unknown protocol %v", signature)
 	}
 }
 
@@ -151,7 +186,45 @@ func (q *QUICConnection) handleRPCStream(rpcStream *quicpogs.RPCServerStream) er
 }
 
 func (q *QUICConnection) RegisterUdpSession(ctx context.Context, sessionID uuid.UUID, dstIP net.IP, dstPort uint16) error {
-	return q.udpSessions.register(sessionID, dstIP, dstPort)
+	udpConn, err := q.udpSessions.register(sessionID, dstIP, dstPort)
+	if err != nil {
+		return err
+	}
+	q.logger.Debug().Msgf("Register session %v, %v, %v", sessionID, dstIP, dstPort)
+	go q.listenOriginUDP(sessionID, udpConn)
+	return nil
+}
+
+// listenOriginUDP reads UDP from origin in a loop, and returns when it cannot write to edge or cannot read from origin
+func (q *QUICConnection) listenOriginUDP(sessionID uuid.UUID, conn *net.UDPConn) {
+	defer func() {
+		q.udpSessions.unregister(sessionID)
+		conn.Close()
+	}()
+	readBuffer := make([]byte, MaxDatagramFrameSize)
+	for {
+		n, err := conn.Read(readBuffer)
+		if n > 0 {
+			if n > MaxDatagramFrameSize-sessionIDLen {
+				// TODO: TUN-5302 return ICMP packet too big message
+				q.logger.Error().Msgf("Origin UDP payload has %d bytes, which exceeds transport MTU %d", n, MaxDatagramFrameSize-sessionIDLen)
+				continue
+			}
+			msgWithID, err := quicpogs.SuffixSessionID(sessionID, readBuffer[:n])
+			if err != nil {
+				q.logger.Err(err).Msg("Failed to suffix session ID to datagram, it will be dropped")
+				continue
+			}
+			if err := q.session.SendMessage(msgWithID); err != nil {
+				q.logger.Err(err).Msg("Failed to send datagram back to edge")
+				return
+			}
+		}
+		if err != nil {
+			q.logger.Err(err).Msg("Failed to read UDP from origin")
+			return
+		}
+	}
 }
 
 // streamReadWriteAcker is a light wrapper over QUIC streams with a callback to send response back to
@@ -208,7 +281,7 @@ func buildHTTPRequest(connectRequest *quicpogs.ConnectRequest, body io.ReadClose
 			// metadata.Key is off the format httpHeaderKey:<HTTPHeader>
 			httpHeaderKey := strings.Split(metadata.Key, ":")
 			if len(httpHeaderKey) != 2 {
-				return nil, fmt.Errorf("Header Key: %s malformed", metadata.Key)
+				return nil, fmt.Errorf("header Key: %s malformed", metadata.Key)
 			}
 			req.Header.Add(httpHeaderKey[1], metadata.Val)
 		}

connection/quic_test.go

@@ -33,7 +33,8 @@ import (
 // It also serves as a demonstration for communication with the QUIC connection started by a cloudflared.
 func TestQUICServer(t *testing.T) {
 	quicConfig := &quic.Config{
-		KeepAlive: true,
+		KeepAlive:       true,
+		EnableDatagrams: true,
 	}
 
 	// Setup test.

connection/udp_session.go

@@ -1,6 +1,7 @@
 package connection
 
 import (
+	"fmt"
 	"net"
 	"sync"
 
@@ -8,18 +9,24 @@ import (
 )
 
 // TODO: TUN-5422 Unregister session
+const (
+	sessionIDLen = len(uuid.UUID{})
+)
+
 type udpSessions struct {
-	lock     sync.Mutex
+	lock     sync.RWMutex
 	sessions map[uuid.UUID]*net.UDPConn
+	localIP  net.IP
 }
 
-func newUDPSessions() *udpSessions {
+func newUDPSessions(localIP net.IP) *udpSessions {
 	return &udpSessions{
 		sessions: make(map[uuid.UUID]*net.UDPConn),
+		localIP:  localIP,
 	}
 }
 
-func (us *udpSessions) register(id uuid.UUID, dstIP net.IP, dstPort uint16) error {
+func (us *udpSessions) register(id uuid.UUID, dstIP net.IP, dstPort uint16) (*net.UDPConn, error) {
 	us.lock.Lock()
 	defer us.lock.Unlock()
 	dstAddr := &net.UDPAddr{
@@ -28,16 +35,56 @@ func (us *udpSessions) register(id uuid.UUID, dstIP net.IP, dstPort uint16) erro
 	}
 	conn, err := net.DialUDP("udp", us.localAddr(), dstAddr)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	us.sessions[id] = conn
-	return nil
+	return conn, nil
+}
+
+func (us *udpSessions) unregister(id uuid.UUID) {
+	us.lock.Lock()
+	defer us.lock.Unlock()
+	delete(us.sessions, id)
+}
+
+func (us *udpSessions) send(id uuid.UUID, payload []byte) error {
+	us.lock.RLock()
+	defer us.lock.RUnlock()
+	conn, ok := us.sessions[id]
+	if !ok {
+		return fmt.Errorf("session %s not found", id)
+	}
+	_, err := conn.Write(payload)
+	return err
 }
 
 func (ud *udpSessions) localAddr() *net.UDPAddr {
 	// TODO: Determine the IP to bind to
+
 	return &net.UDPAddr{
-		IP:   net.IPv4zero,
+		IP:   ud.localIP,
 		Port: 0,
 	}
 }
+
+// TODO: TUN-5421 allow user to specify which IP to bind to
+func GetLocalIP() (net.IP, error) {
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return nil, err
+	}
+	for _, addr := range addrs {
+		// Find the IP that is not loop back
+		var ip net.IP
+		switch v := addr.(type) {
+		case *net.IPNet:
+			ip = v.IP
+		case *net.IPAddr:
+			ip = v.IP
+		}
+		if !ip.IsLoopback() {
+			return ip, nil
+		}
+	}
+	return nil, fmt.Errorf("cannot determine IP to bind to")
+}

quic/datagram.go

@@ -0,0 +1,38 @@
+package quic
+
+import (
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+const (
+	sessionIDLen         = len(uuid.UUID{})
+	MaxDatagramFrameSize = 1220
+)
+
+// Each QUIC datagram should be suffixed with session ID.
+// ExtractSessionID extracts the session ID and a slice with only the payload
+func ExtractSessionID(b []byte) (uuid.UUID, []byte, error) {
+	msgLen := len(b)
+	if msgLen < sessionIDLen {
+		return uuid.Nil, nil, fmt.Errorf("session ID has %d bytes, but data only has %d", sessionIDLen, len(b))
+	}
+	// Parse last 16 bytess as UUID and remove it from slice
+	sessionID, err := uuid.FromBytes(b[len(b)-sessionIDLen:])
+	if err != nil {
+		return uuid.Nil, nil, err
+	}
+	b = b[:len(b)-sessionIDLen]
+	return sessionID, b, nil
+}
+
+// SuffixSessionID appends the session ID at the end of the payload. Suffix is more performant than prefix because
+// the payload slice might already have enough capacity to append the session ID at the end
+func SuffixSessionID(sessionID uuid.UUID, b []byte) ([]byte, error) {
+	if len(b)+len(sessionID) > MaxDatagramFrameSize {
+		return nil, fmt.Errorf("datagram size exceed %d", MaxDatagramFrameSize)
+	}
+	b = append(b, sessionID[:]...)
+	return b, nil
+}

quic/datagram_test.go

@@ -0,0 +1,41 @@
+package quic
+
+import (
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	testSessionID = uuid.New()
+)
+
+func TestSuffixThenRemoveSessionID(t *testing.T) {
+	msg := []byte(t.Name())
+	msgWithID, err := SuffixSessionID(testSessionID, msg)
+	require.NoError(t, err)
+	require.Len(t, msgWithID, len(msg)+sessionIDLen)
+
+	sessionID, msgWithoutID, err := ExtractSessionID(msgWithID)
+	require.NoError(t, err)
+	require.Equal(t, msg, msgWithoutID)
+	require.Equal(t, testSessionID, sessionID)
+}
+
+func TestRemoveSessionIDError(t *testing.T) {
+	// message is too short to contain session ID
+	msg := []byte("test")
+	_, _, err := ExtractSessionID(msg)
+	require.Error(t, err)
+}
+
+func TestSuffixSessionIDError(t *testing.T) {
+	msg := make([]byte, MaxDatagramFrameSize-sessionIDLen)
+	_, err := SuffixSessionID(testSessionID, msg)
+	require.NoError(t, err)
+
+	msg = make([]byte, MaxDatagramFrameSize-sessionIDLen+1)
+	_, err = SuffixSessionID(testSessionID, msg)
+	require.Error(t, err)
+}