Simplify handling if no TCP mux is configured

agent.go

@@ -297,6 +297,9 @@ func NewAgent(config *AgentConfig) (*Agent, error) { //nolint:gocognit
 		log:               log,
 		net:               config.Net,
 		proxyDialer:       config.ProxyDialer,
+		tcpMux:            config.TCPMux,
+		udpMux:            config.UDPMux,
+		udpMuxSrflx:       config.UDPMuxSrflx,
 
 		mDNSMode: mDNSMode,
 		mDNSName: mDNSName,
@@ -314,13 +317,6 @@ func NewAgent(config *AgentConfig) (*Agent, error) { //nolint:gocognit
 		includeLoopback: config.IncludeLoopback,
 	}
 
-	a.tcpMux = config.TCPMux
-	if a.tcpMux == nil {
-		a.tcpMux = newInvalidTCPMux()
-	}
-	a.udpMux = config.UDPMux
-	a.udpMuxSrflx = config.UDPMuxSrflx
-
 	if a.net == nil {
 		a.net, err = stdnet.NewNet()
 		if err != nil {
@@ -906,7 +902,9 @@ func (a *Agent) GetRemoteUserCredentials() (frag string, pwd string, err error)
 }
 
 func (a *Agent) removeUfragFromMux() {
+	if a.tcpMux != nil {
 		a.tcpMux.RemoveConnByUfrag(a.localUfrag)
+	}
 	if a.udpMux != nil {
 		a.udpMux.RemoveConnByUfrag(a.localUfrag)
 	}

errors.go

@@ -103,9 +103,6 @@ var (
 	// ErrRunCanceled indicates a run operation was canceled by its individual done
 	ErrRunCanceled = errors.New("run was canceled by done")
 
-	// ErrTCPMuxNotInitialized indicates TCPMux is not initialized and that invalidTCPMux is used.
-	ErrTCPMuxNotInitialized = errors.New("TCPMux is not initialized")
-
 	// ErrTCPRemoteAddrAlreadyExists indicates we already have the connection with same remote addr.
 	ErrTCPRemoteAddrAlreadyExists = errors.New("conn with same remote addr already exists")
 

gather.go

@@ -6,7 +6,6 @@ package ice
 import (
 	"context"
 	"crypto/tls"
-	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -166,24 +165,24 @@ func (a *Agent) gatherCandidatesLocal(ctx context.Context, networkTypes []Networ
 
 			switch network {
 			case tcp:
+				if a.tcpMux == nil {
+					continue
+				}
+
 				// Handle ICE TCP passive mode
 				var muxConns []net.PacketConn
 				if multi, ok := a.tcpMux.(AllConnsGetter); ok {
 					a.log.Debugf("GetAllConns by ufrag: %s", a.localUfrag)
 					muxConns, err = multi.GetAllConns(a.localUfrag, mappedIP.To4() == nil, ip)
 					if err != nil {
-						if !errors.Is(err, ErrTCPMuxNotInitialized) {
 						a.log.Warnf("error getting all tcp conns by ufrag: %s %s %s", network, ip, a.localUfrag)
-						}
 						continue
 					}
 				} else {
 					a.log.Debugf("GetConn by ufrag: %s", a.localUfrag)
 					conn, err := a.tcpMux.GetConnByUfrag(a.localUfrag, mappedIP.To4() == nil, ip)
 					if err != nil {
-						if !errors.Is(err, ErrTCPMuxNotInitialized) {
 						a.log.Warnf("error getting tcp conn by ufrag: %s %s %s", network, ip, a.localUfrag)
-						}
 						continue
 					}
 					muxConns = []net.PacketConn{conn}

tcp_mux.go

@@ -20,36 +20,13 @@ var ErrGetTransportAddress = errors.New("failed to get local transport address")
 
 // TCPMux is allows grouping multiple TCP net.Conns and using them like UDP
 // net.PacketConns. The main implementation of this is TCPMuxDefault, and this
-// interface exists to:
+// interface exists to allow mocking in tests.
-//  1. prevent SEGV panics when TCPMuxDefault is not initialized by using the
-//     invalidTCPMux implementation, and
-//  2. allow mocking in tests.
 type TCPMux interface {
 	io.Closer
 	GetConnByUfrag(ufrag string, isIPv6 bool, local net.IP) (net.PacketConn, error)
 	RemoveConnByUfrag(ufrag string)
 }
 
-// invalidTCPMux is an implementation of TCPMux that always returns ErrTCPMuxNotInitialized.
-type invalidTCPMux struct{}
-
-func newInvalidTCPMux() *invalidTCPMux {
-	return &invalidTCPMux{}
-}
-
-// Close implements TCPMux interface.
-func (m *invalidTCPMux) Close() error {
-	return ErrTCPMuxNotInitialized
-}
-
-// GetConnByUfrag implements TCPMux interface.
-func (m *invalidTCPMux) GetConnByUfrag(string, bool, net.IP) (net.PacketConn, error) {
-	return nil, ErrTCPMuxNotInitialized
-}
-
-// RemoveConnByUfrag implements TCPMux interface.
-func (m *invalidTCPMux) RemoveConnByUfrag(string) {}
-
 type ipAddr string
 
 // TCPMuxDefault muxes TCP net.Conns into net.PacketConns and groups them by

tcp_mux_test.go

@@ -15,10 +15,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-var (
+var _ TCPMux = &TCPMuxDefault{}
-	_ TCPMux = &TCPMuxDefault{}
-	_ TCPMux = &invalidTCPMux{}
-)
 
 func TestTCPMux_Recv(t *testing.T) {
 	for name, bufSize := range map[string]int{