Remove global state for ICE TCP

This addresses a few points issue of #245:

 - Take a net.Listener instead of having global state
 - Expose a net.TCPMux based API

Also, the unused closeChannel was removed from tcp_mux.go

Closes #253.

agent.go

@@ -120,8 +120,8 @@ type Agent struct {
 	loggerFactory logging.LoggerFactory
 	log           logging.LeveledLogger
 
-	net *vnet.Net
-	tcp *tcpIPMux
+	net    *vnet.Net
+	tcpMux *TCPMux
 
 	interfaceFilter func(string) bool
 
@@ -306,11 +306,7 @@ func NewAgent(config *AgentConfig) (*Agent, error) {
 		insecureSkipVerify: config.InsecureSkipVerify,
 	}
 
-	a.tcp = newTCPIPMux(tcpIPMuxParams{
-		ListenPort:     config.TCPListenPort,
-		Logger:         log,
-		ReadBufferSize: 8,
-	})
+	a.tcpMux = config.TCPMux
 
 	if a.net == nil {
 		a.net = vnet.NewNet(nil)
@@ -887,7 +883,11 @@ func (a *Agent) Close() error {
 
 	a.gatherCandidateCancel()
 	a.err.Store(ErrClosed)
-	a.tcp.RemoveUfrag(a.localUfrag)
+
+	if a.tcpMux != nil {
+		a.tcpMux.RemoveConnByUfrag(a.localUfrag)
+	}
+
 	close(a.done)
 
 	<-done

agent_config.go

@@ -139,10 +139,10 @@ type AgentConfig struct {
 	// to TURN servers via TLS or DTLS
 	InsecureSkipVerify bool
 
-	// TCPListenPort will be used to start a TCP listener on all allowed interfaces for
-	// ICE TCP. Currently only passive candidates are supported. This functionality is
-	// experimental and this API will likely change in the future.
-	TCPListenPort int
+	// TCPMux will be used for multiplexing incoming TCP connections for ICE TCP.
+	// Currently only passive candidates are supported. This functionality is
+	// experimental and the API might change in the future.
+	TCPMux *TCPMux
 }
 
 // initWithDefaults populates an agent and falls back to defaults if fields are unset

gather.go

@@ -161,28 +161,23 @@ func (a *Agent) gatherCandidatesLocal(ctx context.Context, networkTypes []Networ
 			var tcpType TCPType
 			switch network {
 			case tcp:
-				if a.tcp == nil {
+				if a.tcpMux == nil {
 					continue
 				}
-
 				// below is for passive mode
 				// TODO active mode
 				// TODO S-O mode
 
-				mux, muxErr := a.tcp.Listen(ip)
-				if muxErr != nil {
-					a.log.Warnf("could not listen %s %s\n", network, ip)
-					continue
-				}
-
 				a.log.Debugf("GetConn by ufrag: %s\n", a.localUfrag)
-				conn, err = mux.GetConn(a.localUfrag)
+				conn, err = a.tcpMux.GetConnByUfrag(a.localUfrag)
 				if err != nil {
 					a.log.Warnf("error getting tcp conn by ufrag: %s %s\n", network, ip, a.localUfrag)
 					continue
 				}
 				port = conn.LocalAddr().(*net.TCPAddr).Port
 				tcpType = TCPTypePassive
+				// TODO is there a way to verify that the listen address is even
+				// accessible from the current interface.
 			case udp:
 				conn, err = listenUDPInPortRange(a.net, a.log, int(a.portmax), int(a.portmin), network, &net.UDPAddr{IP: ip, Port: 0})
 				if err != nil {

gather_test.go

@@ -14,9 +14,11 @@ import (
 
 	"github.com/pion/dtls/v2"
 	"github.com/pion/dtls/v2/pkg/crypto/selfsign"
+	"github.com/pion/logging"
 	"github.com/pion/transport/test"
 	"github.com/pion/turn/v2"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestListenUDP(t *testing.T) {
@@ -116,11 +118,25 @@ func TestSTUNConcurrency(t *testing.T) {
 		Port:   serverPort,
 	})
 
+	listener, err := net.ListenTCP("tcp", &net.TCPAddr{
+		IP: net.IP{127, 0, 0, 1},
+	})
+	require.NoError(t, err)
+	defer func() {
+		_ = listener.Close()
+	}()
+
 	a, err := NewAgent(&AgentConfig{
 		NetworkTypes:   supportedNetworkTypes,
 		Urls:           urls,
 		CandidateTypes: []CandidateType{CandidateTypeHost, CandidateTypeServerReflexive},
-		TCPListenPort:  9999,
+		TCPMux: NewTCPMux(
+			TCPMuxParams{
+				Listener:       listener,
+				Logger:         logging.NewDefaultLoggerFactory().NewLogger("ice"),
+				ReadBufferSize: 8,
+			},
+		),
 	})
 	assert.NoError(t, err)
 

tcp_mux.go

@@ -11,31 +11,35 @@ import (
 	"github.com/pion/stun"
 )
 
-type tcpMux struct {
-	params *tcpMuxParams
+// TCPMux muxes TCP net.Conns into net.PacketConns and groups them by Ufrag.
+type TCPMux struct {
+	params *TCPMuxParams
+	closed bool
 
 	// conns is a map of all tcpPacketConns indexed by ufrag
 	conns map[string]*tcpPacketConn
 
-	mu         sync.Mutex
-	wg         sync.WaitGroup
-	closedChan chan struct{}
-	closeOnce  sync.Once
+	mu sync.Mutex
+	wg sync.WaitGroup
 }
 
-type tcpMuxParams struct {
+// TCPMuxParams are parameters for TCPMux.
+type TCPMuxParams struct {
 	Listener       net.Listener
 	Logger         logging.LeveledLogger
 	ReadBufferSize int
 }
 
-func newTCPMux(params tcpMuxParams) *tcpMux {
-	m := &tcpMux{
+// NewTCPMux creates a new instance of TCPMux.
+func NewTCPMux(params TCPMuxParams) *TCPMux {
+	if params.Logger == nil {
+		params.Logger = logging.NewDefaultLoggerFactory().NewLogger("ice")
+	}
+
+	m := &TCPMux{
 		params: &params,
 
 		conns: map[string]*tcpPacketConn{},
-
-		closedChan: make(chan struct{}),
 	}
 
 	m.wg.Add(1)
@@ -47,7 +51,7 @@ func newTCPMux(params tcpMuxParams) *tcpMux {
 	return m
 }
 
-func (m *tcpMux) start() {
+func (m *TCPMux) start() {
 	m.params.Logger.Infof("Listening TCP on %s\n", m.params.Listener.Addr())
 	for {
 		conn, err := m.params.Listener.Accept()
@@ -66,11 +70,13 @@ func (m *tcpMux) start() {
 	}
 }
 
-func (m *tcpMux) LocalAddr() net.Addr {
+// LocalAddr returns the listening address of this TCPMux.
+func (m *TCPMux) LocalAddr() net.Addr {
 	return m.params.Listener.Addr()
 }
 
-func (m *tcpMux) GetConn(ufrag string) (net.PacketConn, error) {
+// GetConnByUfrag retrieves an existing or creates a new net.PacketConn.
+func (m *TCPMux) GetConnByUfrag(ufrag string) (net.PacketConn, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
@@ -86,7 +92,7 @@ func (m *tcpMux) GetConn(ufrag string) (net.PacketConn, error) {
 	return conn, nil
 }
 
-func (m *tcpMux) createConn(ufrag string, localAddr net.Addr) *tcpPacketConn {
+func (m *TCPMux) createConn(ufrag string, localAddr net.Addr) *tcpPacketConn {
 	conn := newTCPPacketConn(tcpPacketParams{
 		ReadBuffer: m.params.ReadBufferSize,
 		LocalAddr:  localAddr,
@@ -98,20 +104,20 @@ func (m *tcpMux) createConn(ufrag string, localAddr net.Addr) *tcpPacketConn {
 	go func() {
 		defer m.wg.Done()
 		<-conn.CloseChannel()
-		m.RemoveConn(ufrag)
+		m.RemoveConnByUfrag(ufrag)
 	}()
 
 	return conn
 }
 
-func (m *tcpMux) closeAndLogError(closer io.Closer) {
+func (m *TCPMux) closeAndLogError(closer io.Closer) {
 	err := closer.Close()
 	if err != nil {
 		m.params.Logger.Warnf("Error closing connection: %s", err)
 	}
 }
 
-func (m *tcpMux) handleConn(conn net.Conn) {
+func (m *TCPMux) handleConn(conn net.Conn) {
 	buf := make([]byte, receiveMTU)
 
 	n, err := readStreamingPacket(conn, buf)
@@ -169,43 +175,34 @@ func (m *tcpMux) handleConn(conn net.Conn) {
 	}
 }
 
-func (m *tcpMux) Close() error {
+// Close closes the listener and waits for all goroutines to exit.
+func (m *TCPMux) Close() error {
 	m.mu.Lock()
+	m.closed = true
 
-	m.closeOnce.Do(func() {
-		close(m.closedChan)
-	})
-
+	for _, conn := range m.conns {
+		m.closeAndLogError(conn)
+	}
 	m.conns = map[string]*tcpPacketConn{}
-	m.mu.Unlock()
 
 	err := m.params.Listener.Close()
 
+	m.mu.Unlock()
+
 	m.wg.Wait()
 
 	return err
 }
 
-func (m *tcpMux) CloseChannel() <-chan struct{} {
-	return m.closedChan
-}
-
-func (m *tcpMux) RemoveConn(ufrag string) {
+// RemoveConnByUfrag closes and removes a net.PacketConn by Ufrag.
+func (m *TCPMux) RemoveConnByUfrag(ufrag string) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
 	if conn, ok := m.conns[ufrag]; ok {
 		m.closeAndLogError(conn)
 		delete(m.conns, ufrag)
 	}
-
-	if len(m.conns) == 0 {
-		m.closeOnce.Do(func() {
-			close(m.closedChan)
-		})
-
-		m.closeAndLogError(m.params.Listener)
-	}
 }
 
 const streamingPacketHeaderLen = 2