Fix nil pointer exception when load empty list and try to cast it (#3282)

client/internal/engine.go

@@ -13,7 +13,6 @@ import (
 	"sort"
 	"strings"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/hashicorp/go-multierror"
@@ -147,7 +146,7 @@ type Engine struct {
 	STUNs []*stun.URI
 	// TURNs is a list of STUN servers used by ICE
 	TURNs    []*stun.URI
-	stunTurn atomic.Value
+	stunTurn icemaker.StunTurn
 
 	clientCtx    context.Context
 	clientCancel context.CancelFunc

client/internal/peer/ice/StunTurn.go

@@ -0,0 +1,22 @@
+package ice
+
+import (
+	"sync/atomic"
+
+	"github.com/pion/stun/v2"
+)
+
+type StunTurn atomic.Value
+
+func (s *StunTurn) Load() []*stun.URI {
+	v := (*atomic.Value)(s).Load()
+	if v == nil {
+		return nil
+	}
+
+	return v.([]*stun.URI)
+}
+
+func (s *StunTurn) Store(value []*stun.URI) {
+	(*atomic.Value)(s).Store(value)
+}

client/internal/peer/ice/StunTurn_test.go

@@ -0,0 +1,13 @@
+package ice
+
+import (
+	"testing"
+)
+
+func TestStunTurn_LoadEmpty(t *testing.T) {
+	var stStunTurn StunTurn
+	got := stStunTurn.Load()
+	if len(got) != 0 {
+		t.Errorf("StunTurn.Load() = %v, want %v", got, nil)
+	}
+}

client/internal/peer/ice/agent.go

@@ -5,7 +5,6 @@ import (
 
 	"github.com/pion/ice/v3"
 	"github.com/pion/randutil"
-	"github.com/pion/stun/v2"
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/client/internal/stdnet"
@@ -39,7 +38,7 @@ func NewAgent(iFaceDiscover stdnet.ExternalIFaceDiscover, config Config, candida
 	agentConfig := &ice.AgentConfig{
 		MulticastDNSMode:       ice.MulticastDNSModeDisabled,
 		NetworkTypes:           []ice.NetworkType{ice.NetworkTypeUDP4, ice.NetworkTypeUDP6},
-		Urls:                   config.StunTurn.Load().([]*stun.URI),
+		Urls:                   config.StunTurn.Load(),
 		CandidateTypes:         candidateTypes,
 		InterfaceFilter:        stdnet.InterfaceFilter(config.InterfaceBlackList),
 		UDPMux:                 config.UDPMux,

client/internal/peer/ice/config.go

@@ -1,14 +1,12 @@
 package ice
 
 import (
-	"sync/atomic"
-
 	"github.com/pion/ice/v3"
 )
 
 type Config struct {
 	// StunTurn is a list of STUN and TURN URLs
-	StunTurn *atomic.Value // []*stun.URI
+	StunTurn *StunTurn // []*stun.URI
 
 	// InterfaceBlackList is a list of machine interfaces that should be filtered out by ICE Candidate gathering
 	// (e.g. if eth0 is in the list, host candidate of this interface won't be used)