Implement ICEBind

iface/udp_mux_universal.go

@@ -0,0 +1,246 @@
+package iface
+
+import (
+	"errors"
+	"fmt"
+	log "github.com/sirupsen/logrus"
+	"net"
+	"time"
+
+	"github.com/pion/logging"
+	"github.com/pion/stun"
+)
+
+// UniversalUDPMux allows multiple connections to go over a single UDP port for
+// host, server reflexive and relayed candidates.
+// Actual connection muxing is happening in the UDPMux.
+type UniversalUDPMux interface {
+	UDPMux
+	GetXORMappedAddr(stunAddr net.Addr, deadline time.Duration) (*stun.XORMappedAddress, error)
+	GetRelayedAddr(turnAddr net.Addr, deadline time.Duration) (*net.Addr, error)
+	GetConnForURL(ufrag string, url string) (net.PacketConn, error)
+}
+
+// UniversalUDPMuxDefault handles STUN and TURN servers packets by wrapping the original UDPConn overriding ReadFrom.
+// It the passes packets to the UDPMux that does the actual connection muxing.
+type UniversalUDPMuxDefault struct {
+	*UDPMuxDefault
+	params UniversalUDPMuxParams
+
+	// since we have a shared socket, for srflx candidates it makes sense to have a shared mapped address across all the agents
+	// stun.XORMappedAddress indexed by the STUN server addr
+	xorMappedMap map[string]*xorMapped
+}
+
+// UniversalUDPMuxParams are parameters for UniversalUDPMux server reflexive.
+type UniversalUDPMuxParams struct {
+	Logger                logging.LeveledLogger
+	UDPConn               net.PacketConn
+	XORMappedAddrCacheTTL time.Duration
+}
+
+// NewUniversalUDPMuxDefault creates an implementation of UniversalUDPMux embedding UDPMux
+func NewUniversalUDPMuxDefault(params UniversalUDPMuxParams) *UniversalUDPMuxDefault {
+	if params.Logger == nil {
+		params.Logger = logging.NewDefaultLoggerFactory().NewLogger("ice")
+	}
+	if params.XORMappedAddrCacheTTL == 0 {
+		params.XORMappedAddrCacheTTL = time.Second * 25
+	}
+
+	m := &UniversalUDPMuxDefault{
+		params:       params,
+		xorMappedMap: make(map[string]*xorMapped),
+	}
+
+	// embed UDPMux
+	udpMuxParams := UDPMuxParams{
+		Logger:  params.Logger,
+		UDPConn: m.params.UDPConn,
+	}
+	m.UDPMuxDefault = NewUDPMuxDefault(udpMuxParams)
+
+	return m
+}
+
+// GetRelayedAddr creates relayed connection to the given TURN service and returns the relayed addr.
+// Not implemented yet.
+func (m *UniversalUDPMuxDefault) GetRelayedAddr(turnAddr net.Addr, deadline time.Duration) (*net.Addr, error) {
+	return nil, errors.New("not implemented yet")
+}
+
+// GetConnForURL add uniques to the muxed connection by concatenating ufrag and URL (e.g. STUN URL) to be able to support multiple STUN/TURN servers
+// and return a unique connection per server.
+func (m *UniversalUDPMuxDefault) GetConnForURL(ufrag string, url string) (net.PacketConn, error) {
+	return m.UDPMuxDefault.GetConn(fmt.Sprintf("%s%s", ufrag, url))
+}
+
+func (m *UniversalUDPMuxDefault) HandlePacket(p []byte, n int, addr net.Addr) error {
+	if stun.IsMessage(p[:n]) {
+		msg := &stun.Message{
+			Raw: append([]byte{}, p[:n]...),
+		}
+
+		if err := msg.Decode(); err != nil {
+			log.Warnf("Failed to handle decode ICE from %s: %v\n", addr.String(), err)
+			// todo proper error
+			return nil
+		}
+
+		udpAddr, ok := addr.(*net.UDPAddr)
+		if !ok {
+			// message about this err will be logged in the UDPMux
+			return nil
+		}
+
+		if m.isXORMappedResponse(msg, udpAddr.String()) {
+			err := m.handleXORMappedResponse(udpAddr, msg)
+			if err != nil {
+				log.Debugf("%w: %v", errors.New("failed to get XOR-MAPPED-ADDRESS response"), err)
+				return nil
+			}
+			return nil
+		}
+	}
+	return m.UDPMuxDefault.HandlePacket(p, n, addr)
+}
+
+// isXORMappedResponse indicates whether the message is a XORMappedAddress and is coming from the known STUN server.
+func (m *UniversalUDPMuxDefault) isXORMappedResponse(msg *stun.Message, stunAddr string) bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	// check first if it is a STUN server address because remote peer can also send similar messages but as a BindingSuccess
+	_, ok := m.xorMappedMap[stunAddr]
+	_, err := msg.Get(stun.AttrXORMappedAddress)
+	return err == nil && ok
+}
+
+// handleXORMappedResponse parses response from the STUN server, extracts XORMappedAddress attribute
+// and set the mapped address for the server
+func (m *UniversalUDPMuxDefault) handleXORMappedResponse(stunAddr *net.UDPAddr, msg *stun.Message) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	mappedAddr, ok := m.xorMappedMap[stunAddr.String()]
+	if !ok {
+		return errors.New("no address mapping")
+	}
+
+	var addr stun.XORMappedAddress
+	if err := addr.GetFrom(msg); err != nil {
+		return err
+	}
+
+	m.xorMappedMap[stunAddr.String()] = mappedAddr
+	mappedAddr.SetAddr(&addr)
+
+	return nil
+}
+
+// GetXORMappedAddr returns *stun.XORMappedAddress if already present for a given STUN server.
+// Makes a STUN binding request to discover mapped address otherwise.
+// Blocks until the stun.XORMappedAddress has been discovered or deadline.
+// Method is safe for concurrent use.
+func (m *UniversalUDPMuxDefault) GetXORMappedAddr(serverAddr net.Addr, deadline time.Duration) (*stun.XORMappedAddress, error) {
+	m.mu.Lock()
+	mappedAddr, ok := m.xorMappedMap[serverAddr.String()]
+	// if we already have a mapping for this STUN server (address already received)
+	// and if it is not too old we return it without making a new request to STUN server
+	if ok {
+		if mappedAddr.expired() {
+			mappedAddr.closeWaiters()
+			delete(m.xorMappedMap, serverAddr.String())
+			ok = false
+		} else if mappedAddr.pending() {
+			ok = false
+		}
+	}
+	m.mu.Unlock()
+	if ok {
+		return mappedAddr.addr, nil
+	}
+
+	// otherwise, make a STUN request to discover the address
+	// or wait for already sent request to complete
+	waitAddrReceived, err := m.sendStun(serverAddr)
+	if err != nil {
+		return nil, errors.New("failed to send STUN packet")
+	}
+
+	// block until response was handled by the connWorker routine and XORMappedAddress was updated
+	select {
+	case <-waitAddrReceived:
+		// when channel closed, addr was obtained
+		m.mu.Lock()
+		mappedAddr := *m.xorMappedMap[serverAddr.String()]
+		m.mu.Unlock()
+		if mappedAddr.addr == nil {
+			return nil, errors.New("no address mapping")
+		}
+		return mappedAddr.addr, nil
+	case <-time.After(deadline):
+		return nil, errors.New("timeout while waiting for XORMappedAddr")
+	}
+}
+
+// sendStun sends a STUN request via UDP conn.
+//
+// The returned channel is closed when the STUN response has been received.
+// Method is safe for concurrent use.
+func (m *UniversalUDPMuxDefault) sendStun(serverAddr net.Addr) (chan struct{}, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// if record present in the map, we already sent a STUN request,
+	// just wait when waitAddrReceived will be closed
+	addrMap, ok := m.xorMappedMap[serverAddr.String()]
+	if !ok {
+		addrMap = &xorMapped{
+			expiresAt:        time.Now().Add(m.params.XORMappedAddrCacheTTL),
+			waitAddrReceived: make(chan struct{}),
+		}
+		m.xorMappedMap[serverAddr.String()] = addrMap
+	}
+
+	req, err := stun.Build(stun.BindingRequest, stun.TransactionID)
+	if err != nil {
+		return nil, err
+	}
+
+	if _, err = m.params.UDPConn.WriteTo(req.Raw, serverAddr); err != nil {
+		return nil, err
+	}
+
+	return addrMap.waitAddrReceived, nil
+}
+
+type xorMapped struct {
+	addr             *stun.XORMappedAddress
+	waitAddrReceived chan struct{}
+	expiresAt        time.Time
+}
+
+func (a *xorMapped) closeWaiters() {
+	select {
+	case <-a.waitAddrReceived:
+		// notify was close, ok, that means we received duplicate response
+		// just exit
+		break
+	default:
+		// notify tha twe have a new addr
+		close(a.waitAddrReceived)
+	}
+}
+
+func (a *xorMapped) pending() bool {
+	return a.addr == nil
+}
+
+func (a *xorMapped) expired() bool {
+	return a.expiresAt.Before(time.Now())
+}
+
+func (a *xorMapped) SetAddr(addr *stun.XORMappedAddress) {
+	a.addr = addr
+	a.closeWaiters()
+}