[client] Fix stale local records (#3776)

client/internal/dns/handler_chain_test.go

@@ -1,7 +1,6 @@
 package dns_test
 
 import (
-	"net"
 	"testing"
 
 	"github.com/miekg/dns"
@@ -9,6 +8,7 @@ import (
 	"github.com/stretchr/testify/mock"
 
 	nbdns "github.com/netbirdio/netbird/client/internal/dns"
+	"github.com/netbirdio/netbird/client/internal/dns/test"
 )
 
 // TestHandlerChain_ServeDNS_Priorities tests that handlers are executed in priority order
@@ -30,7 +30,7 @@ func TestHandlerChain_ServeDNS_Priorities(t *testing.T) {
 	r.SetQuestion("example.com.", dns.TypeA)
 
 	// Create test writer
-	w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 	// Setup expectations - only highest priority handler should be called
 	dnsRouteHandler.On("ServeDNS", mock.Anything, r).Once()
@@ -142,7 +142,7 @@ func TestHandlerChain_ServeDNS_DomainMatching(t *testing.T) {
 
 			r := new(dns.Msg)
 			r.SetQuestion(tt.queryDomain, dns.TypeA)
-			w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 			chain.ServeDNS(w, r)
 
@@ -259,7 +259,7 @@ func TestHandlerChain_ServeDNS_OverlappingDomains(t *testing.T) {
 			// Create and execute request
 			r := new(dns.Msg)
 			r.SetQuestion(tt.queryDomain, dns.TypeA)
-			w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 			chain.ServeDNS(w, r)
 
 			// Verify expectations
@@ -316,7 +316,7 @@ func TestHandlerChain_ServeDNS_ChainContinuation(t *testing.T) {
 	}).Once()
 
 	// Execute
-	w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 	chain.ServeDNS(w, r)
 
 	// Verify all handlers were called in order
@@ -325,20 +325,6 @@ func TestHandlerChain_ServeDNS_ChainContinuation(t *testing.T) {
 	handler3.AssertExpectations(t)
 }
 
-// mockResponseWriter implements dns.ResponseWriter for testing
-type mockResponseWriter struct {
-	mock.Mock
-}
-
-func (m *mockResponseWriter) LocalAddr() net.Addr       { return nil }
-func (m *mockResponseWriter) RemoteAddr() net.Addr      { return nil }
-func (m *mockResponseWriter) WriteMsg(*dns.Msg) error   { return nil }
-func (m *mockResponseWriter) Write([]byte) (int, error) { return 0, nil }
-func (m *mockResponseWriter) Close() error              { return nil }
-func (m *mockResponseWriter) TsigStatus() error         { return nil }
-func (m *mockResponseWriter) TsigTimersOnly(bool)       {}
-func (m *mockResponseWriter) Hijack()                   {}
-
 func TestHandlerChain_PriorityDeregistration(t *testing.T) {
 	tests := []struct {
 		name string
@@ -425,7 +411,7 @@ func TestHandlerChain_PriorityDeregistration(t *testing.T) {
 			// Create test request
 			r := new(dns.Msg)
 			r.SetQuestion(tt.query, dns.TypeA)
-			w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 			// Setup expectations
 			for priority, handler := range handlers {
@@ -471,7 +457,7 @@ func TestHandlerChain_MultiPriorityHandling(t *testing.T) {
 	chain.AddHandler(testDomain, matchHandler, nbdns.PriorityMatchDomain)
 
 	// Test 1: Initial state
-	w1 := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w1 := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 	// Highest priority handler (routeHandler) should be called
 	routeHandler.On("ServeDNS", mock.Anything, r).Return().Once()
 	matchHandler.On("ServeDNS", mock.Anything, r).Maybe()   // Ensure others are not expected yet
@@ -490,7 +476,7 @@ func TestHandlerChain_MultiPriorityHandling(t *testing.T) {
 	// Test 2: Remove highest priority handler
 	chain.RemoveHandler(testDomain, nbdns.PriorityDNSRoute)
 
-	w2 := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w2 := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 	// Now middle priority handler (matchHandler) should be called
 	matchHandler.On("ServeDNS", mock.Anything, r).Return().Once()
 	defaultHandler.On("ServeDNS", mock.Anything, r).Maybe() // Ensure default is not expected yet
@@ -506,7 +492,7 @@ func TestHandlerChain_MultiPriorityHandling(t *testing.T) {
 	// Test 3: Remove middle priority handler
 	chain.RemoveHandler(testDomain, nbdns.PriorityMatchDomain)
 
-	w3 := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w3 := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 	// Now lowest priority handler (defaultHandler) should be called
 	defaultHandler.On("ServeDNS", mock.Anything, r).Return().Once()
 
@@ -519,7 +505,7 @@ func TestHandlerChain_MultiPriorityHandling(t *testing.T) {
 	// Test 4: Remove last handler
 	chain.RemoveHandler(testDomain, nbdns.PriorityDefault)
 
-	w4 := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+	w4 := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 	chain.ServeDNS(w4, r) // Call ServeDNS on the now empty chain for this domain
 
 	for _, m := range mocks {
@@ -675,7 +661,7 @@ func TestHandlerChain_CaseSensitivity(t *testing.T) {
 			// Execute request
 			r := new(dns.Msg)
 			r.SetQuestion(tt.query, dns.TypeA)
-			chain.ServeDNS(&mockResponseWriter{}, r)
+			chain.ServeDNS(&test.MockResponseWriter{}, r)
 
 			// Verify each handler was called exactly as expected
 			for _, h := range tt.addHandlers {
@@ -819,7 +805,7 @@ func TestHandlerChain_DomainSpecificityOrdering(t *testing.T) {
 
 			r := new(dns.Msg)
 			r.SetQuestion(tt.query, dns.TypeA)
-			w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 			// Setup handler expectations
 			for pattern, handler := range handlers {
@@ -969,7 +955,7 @@ func TestHandlerChain_AddRemoveRoundtrip(t *testing.T) {
 			handler := &nbdns.MockHandler{}
 			r := new(dns.Msg)
 			r.SetQuestion(tt.queryPattern, dns.TypeA)
-			w := &nbdns.ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &nbdns.ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 			// First verify no handler is called before adding any
 			chain.ServeDNS(w, r)

client/internal/dns/local.go

@@ -1,130 +0,0 @@
-package dns
-
-import (
-	"fmt"
-	"strings"
-	"sync"
-
-	"github.com/miekg/dns"
-	log "github.com/sirupsen/logrus"
-
-	nbdns "github.com/netbirdio/netbird/dns"
-)
-
-type registrationMap map[string]struct{}
-
-type localResolver struct {
-	registeredMap registrationMap
-	records       sync.Map // key: string (domain_class_type), value: []dns.RR
-}
-
-func (d *localResolver) MatchSubdomains() bool {
-	return true
-}
-
-func (d *localResolver) stop() {
-}
-
-// String returns a string representation of the local resolver
-func (d *localResolver) String() string {
-	return fmt.Sprintf("local resolver [%d records]", len(d.registeredMap))
-}
-
-// ID returns the unique handler ID
-func (d *localResolver) id() handlerID {
-	return "local-resolver"
-}
-
-// ServeDNS handles a DNS request
-func (d *localResolver) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
-	if len(r.Question) > 0 {
-		log.Tracef("received local question: domain=%s type=%v class=%v", r.Question[0].Name, r.Question[0].Qtype, r.Question[0].Qclass)
-	}
-
-	replyMessage := &dns.Msg{}
-	replyMessage.SetReply(r)
-	replyMessage.RecursionAvailable = true
-
-	// lookup all records matching the question
-	records := d.lookupRecords(r)
-	if len(records) > 0 {
-		replyMessage.Rcode = dns.RcodeSuccess
-		replyMessage.Answer = append(replyMessage.Answer, records...)
-	} else {
-		replyMessage.Rcode = dns.RcodeNameError
-	}
-
-	err := w.WriteMsg(replyMessage)
-	if err != nil {
-		log.Debugf("got an error while writing the local resolver response, error: %v", err)
-	}
-}
-
-// lookupRecords fetches *all* DNS records matching the first question in r.
-func (d *localResolver) lookupRecords(r *dns.Msg) []dns.RR {
-	if len(r.Question) == 0 {
-		return nil
-	}
-	question := r.Question[0]
-	question.Name = strings.ToLower(question.Name)
-	key := buildRecordKey(question.Name, question.Qclass, question.Qtype)
-
-	value, found := d.records.Load(key)
-	if !found {
-		// alternatively check if we have a cname
-		if question.Qtype != dns.TypeCNAME {
-			r.Question[0].Qtype = dns.TypeCNAME
-			return d.lookupRecords(r)
-		}
-
-		return nil
-	}
-
-	records, ok := value.([]dns.RR)
-	if !ok {
-		log.Errorf("failed to cast records to []dns.RR, records: %v", value)
-		return nil
-	}
-
-	// if there's more than one record, rotate them (round-robin)
-	if len(records) > 1 {
-		first := records[0]
-		records = append(records[1:], first)
-		d.records.Store(key, records)
-	}
-
-	return records
-}
-
-// registerRecord stores a new record by appending it to any existing list
-func (d *localResolver) registerRecord(record nbdns.SimpleRecord) (string, error) {
-	rr, err := dns.NewRR(record.String())
-	if err != nil {
-		return "", fmt.Errorf("register record: %w", err)
-	}
-
-	rr.Header().Rdlength = record.Len()
-	header := rr.Header()
-	key := buildRecordKey(header.Name, header.Class, header.Rrtype)
-
-	// load any existing slice of records, then append
-	existing, _ := d.records.LoadOrStore(key, []dns.RR{})
-	records := existing.([]dns.RR)
-	records = append(records, rr)
-
-	// store updated slice
-	d.records.Store(key, records)
-	return key, nil
-}
-
-// deleteRecord removes *all* records under the recordKey.
-func (d *localResolver) deleteRecord(recordKey string) {
-	d.records.Delete(dns.Fqdn(recordKey))
-}
-
-// buildRecordKey consistently generates a key: name_class_type
-func buildRecordKey(name string, class, qType uint16) string {
-	return fmt.Sprintf("%s_%d_%d", dns.Fqdn(name), class, qType)
-}
-
-func (d *localResolver) probeAvailability() {}

client/internal/dns/local/local.go

@@ -0,0 +1,149 @@
+package local
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+	"sync"
+
+	"github.com/miekg/dns"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/exp/maps"
+
+	"github.com/netbirdio/netbird/client/internal/dns/types"
+	nbdns "github.com/netbirdio/netbird/dns"
+)
+
+type Resolver struct {
+	mu      sync.RWMutex
+	records map[dns.Question][]dns.RR
+}
+
+func NewResolver() *Resolver {
+	return &Resolver{
+		records: make(map[dns.Question][]dns.RR),
+	}
+}
+
+func (d *Resolver) MatchSubdomains() bool {
+	return true
+}
+
+// String returns a string representation of the local resolver
+func (d *Resolver) String() string {
+	return fmt.Sprintf("local resolver [%d records]", len(d.records))
+}
+
+func (d *Resolver) Stop() {}
+
+// ID returns the unique handler ID
+func (d *Resolver) ID() types.HandlerID {
+	return "local-resolver"
+}
+
+func (d *Resolver) ProbeAvailability() {}
+
+// ServeDNS handles a DNS request
+func (d *Resolver) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
+	if len(r.Question) == 0 {
+		log.Debugf("received local resolver request with no question")
+		return
+	}
+	question := r.Question[0]
+	question.Name = strings.ToLower(dns.Fqdn(question.Name))
+
+	log.Tracef("received local question: domain=%s type=%v class=%v", r.Question[0].Name, question.Qtype, question.Qclass)
+
+	replyMessage := &dns.Msg{}
+	replyMessage.SetReply(r)
+	replyMessage.RecursionAvailable = true
+
+	// lookup all records matching the question
+	records := d.lookupRecords(question)
+	if len(records) > 0 {
+		replyMessage.Rcode = dns.RcodeSuccess
+		replyMessage.Answer = append(replyMessage.Answer, records...)
+	} else {
+		// TODO: return success if we have a different record type for the same name, relevant for search domains
+		replyMessage.Rcode = dns.RcodeNameError
+	}
+
+	if err := w.WriteMsg(replyMessage); err != nil {
+		log.Warnf("failed to write the local resolver response: %v", err)
+	}
+}
+
+// lookupRecords fetches *all* DNS records matching the first question in r.
+func (d *Resolver) lookupRecords(question dns.Question) []dns.RR {
+	d.mu.RLock()
+	records, found := d.records[question]
+
+	if !found {
+		d.mu.RUnlock()
+		// alternatively check if we have a cname
+		if question.Qtype != dns.TypeCNAME {
+			question.Qtype = dns.TypeCNAME
+			return d.lookupRecords(question)
+		}
+		return nil
+	}
+
+	recordsCopy := slices.Clone(records)
+	d.mu.RUnlock()
+
+	// if there's more than one record, rotate them (round-robin)
+	if len(recordsCopy) > 1 {
+		d.mu.Lock()
+		records = d.records[question]
+		if len(records) > 1 {
+			first := records[0]
+			records = append(records[1:], first)
+			d.records[question] = records
+		}
+		d.mu.Unlock()
+	}
+
+	return recordsCopy
+}
+
+func (d *Resolver) Update(update []nbdns.SimpleRecord) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	maps.Clear(d.records)
+
+	for _, rec := range update {
+		if err := d.registerRecord(rec); err != nil {
+			log.Warnf("failed to register the record (%s): %v", rec, err)
+			continue
+		}
+	}
+}
+
+// RegisterRecord stores a new record by appending it to any existing list
+func (d *Resolver) RegisterRecord(record nbdns.SimpleRecord) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	return d.registerRecord(record)
+}
+
+// registerRecord performs the registration with the lock already held
+func (d *Resolver) registerRecord(record nbdns.SimpleRecord) error {
+	rr, err := dns.NewRR(record.String())
+	if err != nil {
+		return fmt.Errorf("register record: %w", err)
+	}
+
+	rr.Header().Rdlength = record.Len()
+	header := rr.Header()
+	q := dns.Question{
+		Name:   strings.ToLower(dns.Fqdn(header.Name)),
+		Qtype:  header.Rrtype,
+		Qclass: header.Class,
+	}
+
+	d.records[q] = append(d.records[q], rr)
+
+	return nil
+}

client/internal/dns/local/local_test.go

@@ -0,0 +1,472 @@
+package local
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/client/internal/dns/test"
+	nbdns "github.com/netbirdio/netbird/dns"
+)
+
+func TestLocalResolver_ServeDNS(t *testing.T) {
+	recordA := nbdns.SimpleRecord{
+		Name:  "peera.netbird.cloud.",
+		Type:  1,
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "1.2.3.4",
+	}
+
+	recordCNAME := nbdns.SimpleRecord{
+		Name:  "peerb.netbird.cloud.",
+		Type:  5,
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "www.netbird.io",
+	}
+
+	testCases := []struct {
+		name                string
+		inputRecord         nbdns.SimpleRecord
+		inputMSG            *dns.Msg
+		responseShouldBeNil bool
+	}{
+		{
+			name:        "Should Resolve A Record",
+			inputRecord: recordA,
+			inputMSG:    new(dns.Msg).SetQuestion(recordA.Name, dns.TypeA),
+		},
+		{
+			name:        "Should Resolve CNAME Record",
+			inputRecord: recordCNAME,
+			inputMSG:    new(dns.Msg).SetQuestion(recordCNAME.Name, dns.TypeCNAME),
+		},
+		{
+			name:                "Should Not Write When Not Found A Record",
+			inputRecord:         recordA,
+			inputMSG:            new(dns.Msg).SetQuestion("not.found.com", dns.TypeA),
+			responseShouldBeNil: true,
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			resolver := NewResolver()
+			_ = resolver.RegisterRecord(testCase.inputRecord)
+			var responseMSG *dns.Msg
+			responseWriter := &test.MockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+
+			resolver.ServeDNS(responseWriter, testCase.inputMSG)
+
+			if responseMSG == nil || len(responseMSG.Answer) == 0 {
+				if testCase.responseShouldBeNil {
+					return
+				}
+				t.Fatalf("should write a response message")
+			}
+
+			answerString := responseMSG.Answer[0].String()
+			if !strings.Contains(answerString, testCase.inputRecord.Name) {
+				t.Fatalf("answer doesn't contain the same domain name: \nWant: %s\nGot:%s", testCase.name, answerString)
+			}
+			if !strings.Contains(answerString, dns.Type(testCase.inputRecord.Type).String()) {
+				t.Fatalf("answer doesn't contain the correct type: \nWant: %s\nGot:%s", dns.Type(testCase.inputRecord.Type).String(), answerString)
+			}
+			if !strings.Contains(answerString, testCase.inputRecord.RData) {
+				t.Fatalf("answer doesn't contain the same address: \nWant: %s\nGot:%s", testCase.inputRecord.RData, answerString)
+			}
+		})
+	}
+}
+
+// TestLocalResolver_Update_StaleRecord verifies that updating
+// a record correctly replaces the old one, preventing stale entries.
+func TestLocalResolver_Update_StaleRecord(t *testing.T) {
+	recordName := "host.example.com."
+	recordType := dns.TypeA
+	recordClass := dns.ClassINET
+
+	record1 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "1.1.1.1",
+	}
+	record2 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "2.2.2.2",
+	}
+
+	recordKey := dns.Question{Name: recordName, Qtype: uint16(recordClass), Qclass: recordType}
+
+	resolver := NewResolver()
+
+	update1 := []nbdns.SimpleRecord{record1}
+	update2 := []nbdns.SimpleRecord{record2}
+
+	// Apply first update
+	resolver.Update(update1)
+
+	// Verify first update
+	resolver.mu.RLock()
+	rrSlice1, found1 := resolver.records[recordKey]
+	resolver.mu.RUnlock()
+
+	require.True(t, found1, "Record key %s not found after first update", recordKey)
+	require.Len(t, rrSlice1, 1, "Should have exactly 1 record after first update")
+	assert.Contains(t, rrSlice1[0].String(), record1.RData, "Record after first update should be %s", record1.RData)
+
+	// Apply second update
+	resolver.Update(update2)
+
+	// Verify second update
+	resolver.mu.RLock()
+	rrSlice2, found2 := resolver.records[recordKey]
+	resolver.mu.RUnlock()
+
+	require.True(t, found2, "Record key %s not found after second update", recordKey)
+	require.Len(t, rrSlice2, 1, "Should have exactly 1 record after update overwriting the key")
+	assert.Contains(t, rrSlice2[0].String(), record2.RData, "The single record should be the updated one (%s)", record2.RData)
+	assert.NotContains(t, rrSlice2[0].String(), record1.RData, "The stale record (%s) should not be present", record1.RData)
+}
+
+// TestLocalResolver_MultipleRecords_SameQuestion verifies that multiple records
+// with the same question are stored properly
+func TestLocalResolver_MultipleRecords_SameQuestion(t *testing.T) {
+	resolver := NewResolver()
+
+	recordName := "multi.example.com."
+	recordType := dns.TypeA
+
+	// Create two records with the same name and type but different IPs
+	record1 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.1",
+	}
+	record2 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.2",
+	}
+
+	update := []nbdns.SimpleRecord{record1, record2}
+
+	// Apply update with both records
+	resolver.Update(update)
+
+	// Create question that matches both records
+	question := dns.Question{
+		Name:   recordName,
+		Qtype:  recordType,
+		Qclass: dns.ClassINET,
+	}
+
+	// Verify both records are stored
+	resolver.mu.RLock()
+	records, found := resolver.records[question]
+	resolver.mu.RUnlock()
+
+	require.True(t, found, "Records for question %v not found", question)
+	require.Len(t, records, 2, "Should have exactly 2 records for the same question")
+
+	// Verify both record data values are present
+	recordStrings := []string{records[0].String(), records[1].String()}
+	assert.Contains(t, recordStrings[0]+recordStrings[1], record1.RData, "First record data should be present")
+	assert.Contains(t, recordStrings[0]+recordStrings[1], record2.RData, "Second record data should be present")
+}
+
+// TestLocalResolver_RecordRotation verifies that records are rotated in a round-robin fashion
+func TestLocalResolver_RecordRotation(t *testing.T) {
+	resolver := NewResolver()
+
+	recordName := "rotation.example.com."
+	recordType := dns.TypeA
+
+	// Create three records with the same name and type but different IPs
+	record1 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "192.168.1.1",
+	}
+	record2 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "192.168.1.2",
+	}
+	record3 := nbdns.SimpleRecord{
+		Name: recordName, Type: int(recordType), Class: nbdns.DefaultClass, TTL: 300, RData: "192.168.1.3",
+	}
+
+	update := []nbdns.SimpleRecord{record1, record2, record3}
+
+	// Apply update with all three records
+	resolver.Update(update)
+
+	msg := new(dns.Msg).SetQuestion(recordName, recordType)
+
+	// First lookup - should return the records in original order
+	var responses [3]*dns.Msg
+
+	// Perform three lookups to verify rotation
+	for i := 0; i < 3; i++ {
+		responseWriter := &test.MockResponseWriter{
+			WriteMsgFunc: func(m *dns.Msg) error {
+				responses[i] = m
+				return nil
+			},
+		}
+
+		resolver.ServeDNS(responseWriter, msg)
+	}
+
+	// Verify all three responses contain answers
+	for i, resp := range responses {
+		require.NotNil(t, resp, "Response %d should not be nil", i)
+		require.Len(t, resp.Answer, 3, "Response %d should have 3 answers", i)
+	}
+
+	// Verify the first record in each response is different due to rotation
+	firstRecordIPs := []string{
+		responses[0].Answer[0].String(),
+		responses[1].Answer[0].String(),
+		responses[2].Answer[0].String(),
+	}
+
+	// Each record should be different (rotated)
+	assert.NotEqual(t, firstRecordIPs[0], firstRecordIPs[1], "First lookup should differ from second lookup due to rotation")
+	assert.NotEqual(t, firstRecordIPs[1], firstRecordIPs[2], "Second lookup should differ from third lookup due to rotation")
+	assert.NotEqual(t, firstRecordIPs[0], firstRecordIPs[2], "First lookup should differ from third lookup due to rotation")
+
+	// After three rotations, we should have cycled through all records
+	assert.Contains(t, firstRecordIPs[0]+firstRecordIPs[1]+firstRecordIPs[2], record1.RData)
+	assert.Contains(t, firstRecordIPs[0]+firstRecordIPs[1]+firstRecordIPs[2], record2.RData)
+	assert.Contains(t, firstRecordIPs[0]+firstRecordIPs[1]+firstRecordIPs[2], record3.RData)
+}
+
+// TestLocalResolver_CaseInsensitiveMatching verifies that DNS record lookups are case-insensitive
+func TestLocalResolver_CaseInsensitiveMatching(t *testing.T) {
+	resolver := NewResolver()
+
+	// Create record with lowercase name
+	lowerCaseRecord := nbdns.SimpleRecord{
+		Name:  "lower.example.com.",
+		Type:  int(dns.TypeA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "10.10.10.10",
+	}
+
+	// Create record with mixed case name
+	mixedCaseRecord := nbdns.SimpleRecord{
+		Name:  "MiXeD.ExAmPlE.CoM.",
+		Type:  int(dns.TypeA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "20.20.20.20",
+	}
+
+	// Update resolver with the records
+	resolver.Update([]nbdns.SimpleRecord{lowerCaseRecord, mixedCaseRecord})
+
+	testCases := []struct {
+		name          string
+		queryName     string
+		expectedRData string
+		shouldResolve bool
+	}{
+		{
+			name:          "Query lowercase with lowercase record",
+			queryName:     "lower.example.com.",
+			expectedRData: "10.10.10.10",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query uppercase with lowercase record",
+			queryName:     "LOWER.EXAMPLE.COM.",
+			expectedRData: "10.10.10.10",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query mixed case with lowercase record",
+			queryName:     "LoWeR.eXaMpLe.CoM.",
+			expectedRData: "10.10.10.10",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query lowercase with mixed case record",
+			queryName:     "mixed.example.com.",
+			expectedRData: "20.20.20.20",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query uppercase with mixed case record",
+			queryName:     "MIXED.EXAMPLE.COM.",
+			expectedRData: "20.20.20.20",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query with different casing pattern",
+			queryName:     "mIxEd.ExaMpLe.cOm.",
+			expectedRData: "20.20.20.20",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query non-existent domain",
+			queryName:     "nonexistent.example.com.",
+			shouldResolve: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var responseMSG *dns.Msg
+
+			// Create DNS query with the test case name
+			msg := new(dns.Msg).SetQuestion(tc.queryName, dns.TypeA)
+
+			// Create mock response writer to capture the response
+			responseWriter := &test.MockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+
+			// Perform DNS query
+			resolver.ServeDNS(responseWriter, msg)
+
+			// Check if we expect a successful resolution
+			if !tc.shouldResolve {
+				if responseMSG == nil || len(responseMSG.Answer) == 0 {
+					// Expected no answer, test passes
+					return
+				}
+				t.Fatalf("Expected no resolution for %s, but got answer: %v", tc.queryName, responseMSG.Answer)
+			}
+
+			// Verify we got a response
+			require.NotNil(t, responseMSG, "Should have received a response message")
+			require.Greater(t, len(responseMSG.Answer), 0, "Response should contain at least one answer")
+
+			// Verify the response contains the expected data
+			answerString := responseMSG.Answer[0].String()
+			assert.Contains(t, answerString, tc.expectedRData,
+				"Answer should contain the expected IP address %s, got: %s",
+				tc.expectedRData, answerString)
+		})
+	}
+}
+
+// TestLocalResolver_CNAMEFallback verifies that the resolver correctly falls back
+// to checking for CNAME records when the requested record type isn't found
+func TestLocalResolver_CNAMEFallback(t *testing.T) {
+	resolver := NewResolver()
+
+	// Create a CNAME record (but no A record for this name)
+	cnameRecord := nbdns.SimpleRecord{
+		Name:  "alias.example.com.",
+		Type:  int(dns.TypeCNAME),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "target.example.com.",
+	}
+
+	// Create an A record for the CNAME target
+	targetRecord := nbdns.SimpleRecord{
+		Name:  "target.example.com.",
+		Type:  int(dns.TypeA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "192.168.100.100",
+	}
+
+	// Update resolver with both records
+	resolver.Update([]nbdns.SimpleRecord{cnameRecord, targetRecord})
+
+	testCases := []struct {
+		name          string
+		queryName     string
+		queryType     uint16
+		expectedType  string
+		expectedRData string
+		shouldResolve bool
+	}{
+		{
+			name:          "Directly query CNAME record",
+			queryName:     "alias.example.com.",
+			queryType:     dns.TypeCNAME,
+			expectedType:  "CNAME",
+			expectedRData: "target.example.com.",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query A record but get CNAME fallback",
+			queryName:     "alias.example.com.",
+			queryType:     dns.TypeA,
+			expectedType:  "CNAME",
+			expectedRData: "target.example.com.",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query AAAA record but get CNAME fallback",
+			queryName:     "alias.example.com.",
+			queryType:     dns.TypeAAAA,
+			expectedType:  "CNAME",
+			expectedRData: "target.example.com.",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query direct A record",
+			queryName:     "target.example.com.",
+			queryType:     dns.TypeA,
+			expectedType:  "A",
+			expectedRData: "192.168.100.100",
+			shouldResolve: true,
+		},
+		{
+			name:          "Query non-existent name",
+			queryName:     "nonexistent.example.com.",
+			queryType:     dns.TypeA,
+			shouldResolve: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var responseMSG *dns.Msg
+
+			// Create DNS query with the test case parameters
+			msg := new(dns.Msg).SetQuestion(tc.queryName, tc.queryType)
+
+			// Create mock response writer to capture the response
+			responseWriter := &test.MockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+
+			// Perform DNS query
+			resolver.ServeDNS(responseWriter, msg)
+
+			// Check if we expect a successful resolution
+			if !tc.shouldResolve {
+				if responseMSG == nil || len(responseMSG.Answer) == 0 || responseMSG.Rcode != dns.RcodeSuccess {
+					// Expected no resolution, test passes
+					return
+				}
+				t.Fatalf("Expected no resolution for %s, but got answer: %v", tc.queryName, responseMSG.Answer)
+			}
+
+			// Verify we got a successful response
+			require.NotNil(t, responseMSG, "Should have received a response message")
+			require.Equal(t, dns.RcodeSuccess, responseMSG.Rcode, "Response should have success status code")
+			require.Greater(t, len(responseMSG.Answer), 0, "Response should contain at least one answer")
+
+			// Verify the response contains the expected data
+			answerString := responseMSG.Answer[0].String()
+			assert.Contains(t, answerString, tc.expectedType,
+				"Answer should be of type %s, got: %s", tc.expectedType, answerString)
+			assert.Contains(t, answerString, tc.expectedRData,
+				"Answer should contain the expected data %s, got: %s", tc.expectedRData, answerString)
+		})
+	}
+}

client/internal/dns/local_test.go

@@ -1,88 +0,0 @@
-package dns
-
-import (
-	"strings"
-	"testing"
-
-	"github.com/miekg/dns"
-
-	nbdns "github.com/netbirdio/netbird/dns"
-)
-
-func TestLocalResolver_ServeDNS(t *testing.T) {
-	recordA := nbdns.SimpleRecord{
-		Name:  "peera.netbird.cloud.",
-		Type:  1,
-		Class: nbdns.DefaultClass,
-		TTL:   300,
-		RData: "1.2.3.4",
-	}
-
-	recordCNAME := nbdns.SimpleRecord{
-		Name:  "peerb.netbird.cloud.",
-		Type:  5,
-		Class: nbdns.DefaultClass,
-		TTL:   300,
-		RData: "www.netbird.io",
-	}
-
-	testCases := []struct {
-		name                string
-		inputRecord         nbdns.SimpleRecord
-		inputMSG            *dns.Msg
-		responseShouldBeNil bool
-	}{
-		{
-			name:        "Should Resolve A Record",
-			inputRecord: recordA,
-			inputMSG:    new(dns.Msg).SetQuestion(recordA.Name, dns.TypeA),
-		},
-		{
-			name:        "Should Resolve CNAME Record",
-			inputRecord: recordCNAME,
-			inputMSG:    new(dns.Msg).SetQuestion(recordCNAME.Name, dns.TypeCNAME),
-		},
-		{
-			name:                "Should Not Write When Not Found A Record",
-			inputRecord:         recordA,
-			inputMSG:            new(dns.Msg).SetQuestion("not.found.com", dns.TypeA),
-			responseShouldBeNil: true,
-		},
-	}
-
-	for _, testCase := range testCases {
-		t.Run(testCase.name, func(t *testing.T) {
-			resolver := &localResolver{
-				registeredMap: make(registrationMap),
-			}
-			_, _ = resolver.registerRecord(testCase.inputRecord)
-			var responseMSG *dns.Msg
-			responseWriter := &mockResponseWriter{
-				WriteMsgFunc: func(m *dns.Msg) error {
-					responseMSG = m
-					return nil
-				},
-			}
-
-			resolver.ServeDNS(responseWriter, testCase.inputMSG)
-
-			if responseMSG == nil || len(responseMSG.Answer) == 0 {
-				if testCase.responseShouldBeNil {
-					return
-				}
-				t.Fatalf("should write a response message")
-			}
-
-			answerString := responseMSG.Answer[0].String()
-			if !strings.Contains(answerString, testCase.inputRecord.Name) {
-				t.Fatalf("answer doesn't contain the same domain name: \nWant: %s\nGot:%s", testCase.name, answerString)
-			}
-			if !strings.Contains(answerString, dns.Type(testCase.inputRecord.Type).String()) {
-				t.Fatalf("answer doesn't contain the correct type: \nWant: %s\nGot:%s", dns.Type(testCase.inputRecord.Type).String(), answerString)
-			}
-			if !strings.Contains(answerString, testCase.inputRecord.RData) {
-				t.Fatalf("answer doesn't contain the same address: \nWant: %s\nGot:%s", testCase.inputRecord.RData, answerString)
-			}
-		})
-	}
-}

client/internal/dns/mock_test.go

@@ -1,26 +0,0 @@
-package dns
-
-import (
-	"net"
-
-	"github.com/miekg/dns"
-)
-
-type mockResponseWriter struct {
-	WriteMsgFunc func(m *dns.Msg) error
-}
-
-func (rw *mockResponseWriter) WriteMsg(m *dns.Msg) error {
-	if rw.WriteMsgFunc != nil {
-		return rw.WriteMsgFunc(m)
-	}
-	return nil
-}
-
-func (rw *mockResponseWriter) LocalAddr() net.Addr       { return nil }
-func (rw *mockResponseWriter) RemoteAddr() net.Addr      { return nil }
-func (rw *mockResponseWriter) Write([]byte) (int, error) { return 0, nil }
-func (rw *mockResponseWriter) Close() error              { return nil }
-func (rw *mockResponseWriter) TsigStatus() error         { return nil }
-func (rw *mockResponseWriter) TsigTimersOnly(bool)       {}
-func (rw *mockResponseWriter) Hijack()                   {}

client/internal/dns/server.go

@@ -15,6 +15,8 @@ import (
 	"golang.org/x/exp/maps"
 
 	"github.com/netbirdio/netbird/client/iface/netstack"
+	"github.com/netbirdio/netbird/client/internal/dns/local"
+	"github.com/netbirdio/netbird/client/internal/dns/types"
 	"github.com/netbirdio/netbird/client/internal/listener"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/statemanager"
@@ -46,8 +48,6 @@ type Server interface {
 	ProbeAvailability()
 }
 
-type handlerID string
-
 type nsGroupsByDomain struct {
 	domain string
 	groups []*nbdns.NameServerGroup
@@ -61,7 +61,7 @@ type DefaultServer struct {
 	mux                sync.Mutex
 	service            service
 	dnsMuxMap          registeredHandlerMap
-	localResolver      *localResolver
+	localResolver      *local.Resolver
 	wgInterface        WGIface
 	hostManager        hostManager
 	updateSerial       uint64
@@ -84,9 +84,9 @@ type DefaultServer struct {
 
 type handlerWithStop interface {
 	dns.Handler
-	stop()
+	Stop()
-	probeAvailability()
+	ProbeAvailability()
-	id() handlerID
+	ID() types.HandlerID
 }
 
 type handlerWrapper struct {
@@ -95,7 +95,7 @@ type handlerWrapper struct {
 	priority int
 }
 
-type registeredHandlerMap map[handlerID]handlerWrapper
+type registeredHandlerMap map[types.HandlerID]handlerWrapper
 
 // NewDefaultServer returns a new dns server
 func NewDefaultServer(
@@ -178,9 +178,7 @@ func newDefaultServer(
 		handlerChain:   handlerChain,
 		extraDomains:   make(map[domain.Domain]int),
 		dnsMuxMap:      make(registeredHandlerMap),
-		localResolver: &localResolver{
+		localResolver:  local.NewResolver(),
-			registeredMap: make(registrationMap),
-		},
 		wgInterface:    wgInterface,
 		statusRecorder: statusRecorder,
 		stateManager:   stateManager,
@@ -403,7 +401,7 @@ func (s *DefaultServer) ProbeAvailability() {
 		wg.Add(1)
 		go func(mux handlerWithStop) {
 			defer wg.Done()
-			mux.probeAvailability()
+			mux.ProbeAvailability()
 		}(mux.handler)
 	}
 	wg.Wait()
@@ -420,7 +418,7 @@ func (s *DefaultServer) applyConfiguration(update nbdns.Config) error {
 		s.service.Stop()
 	}
 
-	localMuxUpdates, localRecordsByDomain, err := s.buildLocalHandlerUpdate(update.CustomZones)
+	localMuxUpdates, localRecords, err := s.buildLocalHandlerUpdate(update.CustomZones)
 	if err != nil {
 		return fmt.Errorf("local handler updater: %w", err)
 	}
@@ -434,7 +432,7 @@ func (s *DefaultServer) applyConfiguration(update nbdns.Config) error {
 	s.updateMux(muxUpdates)
 
 	// register local records
-	s.updateLocalResolver(localRecordsByDomain)
+	s.localResolver.Update(localRecords)
 
 	s.currentConfig = dnsConfigToHostDNSConfig(update, s.service.RuntimeIP(), s.service.RuntimePort())
 
@@ -516,11 +514,9 @@ func (s *DefaultServer) handleErrNoGroupaAll(err error) {
 	)
 }
 
-func (s *DefaultServer) buildLocalHandlerUpdate(
+func (s *DefaultServer) buildLocalHandlerUpdate(customZones []nbdns.CustomZone) ([]handlerWrapper, []nbdns.SimpleRecord, error) {
-	customZones []nbdns.CustomZone,
-) ([]handlerWrapper, map[string][]nbdns.SimpleRecord, error) {
 	var muxUpdates []handlerWrapper
-	localRecords := make(map[string][]nbdns.SimpleRecord)
+	var localRecords []nbdns.SimpleRecord
 
 	for _, customZone := range customZones {
 		if len(customZone.Records) == 0 {
@@ -534,17 +530,13 @@ func (s *DefaultServer) buildLocalHandlerUpdate(
 			priority: PriorityMatchDomain,
 		})
 
-		// group all records under this domain
 		for _, record := range customZone.Records {
-			var class uint16 = dns.ClassINET
 			if record.Class != nbdns.DefaultClass {
 				log.Warnf("received an invalid class type: %s", record.Class)
 				continue
 			}
-
+			// zone records contain the fqdn, so we can just flatten them
-			key := buildRecordKey(record.Name, class, uint16(record.Type))
+			localRecords = append(localRecords, record)
-
-			localRecords[key] = append(localRecords[key], record)
 		}
 	}
 
@@ -627,7 +619,7 @@ func (s *DefaultServer) createHandlersForDomainGroup(domainGroup nsGroupsByDomai
 		}
 
 		if len(handler.upstreamServers) == 0 {
-			handler.stop()
+			handler.Stop()
 			log.Errorf("received a nameserver group with an invalid nameserver list")
 			continue
 		}
@@ -656,7 +648,7 @@ func (s *DefaultServer) updateMux(muxUpdates []handlerWrapper) {
 	// this will introduce a short period of time when the server is not able to handle DNS requests
 	for _, existing := range s.dnsMuxMap {
 		s.deregisterHandler([]string{existing.domain}, existing.priority)
-		existing.handler.stop()
+		existing.handler.Stop()
 	}
 
 	muxUpdateMap := make(registeredHandlerMap)
@@ -667,7 +659,7 @@ func (s *DefaultServer) updateMux(muxUpdates []handlerWrapper) {
 			containsRootUpdate = true
 		}
 		s.registerHandler([]string{update.domain}, update.handler, update.priority)
-		muxUpdateMap[update.handler.id()] = update
+		muxUpdateMap[update.handler.ID()] = update
 	}
 
 	// If there's no root update and we had a root handler, restore it
@@ -683,33 +675,6 @@ func (s *DefaultServer) updateMux(muxUpdates []handlerWrapper) {
 	s.dnsMuxMap = muxUpdateMap
 }
 
-func (s *DefaultServer) updateLocalResolver(update map[string][]nbdns.SimpleRecord) {
-	// remove old records that are no longer present
-	for key := range s.localResolver.registeredMap {
-		_, found := update[key]
-		if !found {
-			s.localResolver.deleteRecord(key)
-		}
-	}
-
-	updatedMap := make(registrationMap)
-	for _, recs := range update {
-		for _, rec := range recs {
-			// convert the record to a dns.RR and register
-			key, err := s.localResolver.registerRecord(rec)
-			if err != nil {
-				log.Warnf("got an error while registering the record (%s), error: %v",
-					rec.String(), err)
-				continue
-			}
-
-			updatedMap[key] = struct{}{}
-		}
-	}
-
-	s.localResolver.registeredMap = updatedMap
-}
-
 func getNSHostPort(ns nbdns.NameServer) string {
 	return fmt.Sprintf("%s:%d", ns.IP.String(), ns.Port)
 }

client/internal/dns/server_test.go

@@ -23,6 +23,9 @@ import (
 	"github.com/netbirdio/netbird/client/iface/device"
 	pfmock "github.com/netbirdio/netbird/client/iface/mocks"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
+	"github.com/netbirdio/netbird/client/internal/dns/local"
+	"github.com/netbirdio/netbird/client/internal/dns/test"
+	"github.com/netbirdio/netbird/client/internal/dns/types"
 	"github.com/netbirdio/netbird/client/internal/netflow"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/statemanager"
@@ -107,6 +110,7 @@ func generateDummyHandler(domain string, servers []nbdns.NameServer) *upstreamRe
 }
 
 func TestUpdateDNSServer(t *testing.T) {
+
 	nameServers := []nbdns.NameServer{
 		{
 			IP:     netip.MustParseAddr("8.8.8.8"),
@@ -120,22 +124,21 @@ func TestUpdateDNSServer(t *testing.T) {
 		},
 	}
 
-	dummyHandler := &localResolver{}
+	dummyHandler := local.NewResolver()
 
 	testCases := []struct {
 		name                string
 		initUpstreamMap     registeredHandlerMap
-		initLocalMap        registrationMap
+		initLocalRecords    []nbdns.SimpleRecord
 		initSerial          uint64
 		inputSerial         uint64
 		inputUpdate         nbdns.Config
 		shouldFail          bool
 		expectedUpstreamMap registeredHandlerMap
-		expectedLocalMap    registrationMap
+		expectedLocalQs     []dns.Question
 	}{
 		{
 			name:            "Initial Config Should Succeed",
-			initLocalMap:    make(registrationMap),
 			initUpstreamMap: make(registeredHandlerMap),
 			initSerial:      0,
 			inputSerial:     1,
@@ -159,30 +162,30 @@ func TestUpdateDNSServer(t *testing.T) {
 				},
 			},
 			expectedUpstreamMap: registeredHandlerMap{
-				generateDummyHandler("netbird.io", nameServers).id(): handlerWrapper{
+				generateDummyHandler("netbird.io", nameServers).ID(): handlerWrapper{
 					domain:   "netbird.io",
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
 				},
-				dummyHandler.id(): handlerWrapper{
+				dummyHandler.ID(): handlerWrapper{
 					domain:   "netbird.cloud",
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
 				},
-				generateDummyHandler(".", nameServers).id(): handlerWrapper{
+				generateDummyHandler(".", nameServers).ID(): handlerWrapper{
 					domain:   nbdns.RootZone,
 					handler:  dummyHandler,
 					priority: PriorityDefault,
 				},
 			},
-			expectedLocalMap: registrationMap{buildRecordKey(zoneRecords[0].Name, 1, 1): struct{}{}},
+			expectedLocalQs: []dns.Question{{Name: "peera.netbird.cloud.", Qtype: dns.TypeA, Qclass: dns.ClassINET}},
 		},
 		{
 			name:             "New Config Should Succeed",
-			initLocalMap: registrationMap{"netbird.cloud": struct{}{}},
+			initLocalRecords: []nbdns.SimpleRecord{{Name: "netbird.cloud", Type: 1, Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.1"}},
 			initUpstreamMap: registeredHandlerMap{
-				generateDummyHandler(zoneRecords[0].Name, nameServers).id(): handlerWrapper{
+				generateDummyHandler(zoneRecords[0].Name, nameServers).ID(): handlerWrapper{
-					domain:   buildRecordKey(zoneRecords[0].Name, 1, 1),
+					domain:   "netbird.cloud",
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
 				},
@@ -205,7 +208,7 @@ func TestUpdateDNSServer(t *testing.T) {
 				},
 			},
 			expectedUpstreamMap: registeredHandlerMap{
-				generateDummyHandler("netbird.io", nameServers).id(): handlerWrapper{
+				generateDummyHandler("netbird.io", nameServers).ID(): handlerWrapper{
 					domain:   "netbird.io",
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
@@ -216,11 +219,11 @@ func TestUpdateDNSServer(t *testing.T) {
 					priority: PriorityMatchDomain,
 				},
 			},
-			expectedLocalMap: registrationMap{buildRecordKey(zoneRecords[0].Name, 1, 1): struct{}{}},
+			expectedLocalQs: []dns.Question{{Name: zoneRecords[0].Name, Qtype: 1, Qclass: 1}},
 		},
 		{
 			name:             "Smaller Config Serial Should Be Skipped",
-			initLocalMap:    make(registrationMap),
+			initLocalRecords: []nbdns.SimpleRecord{},
 			initUpstreamMap:  make(registeredHandlerMap),
 			initSerial:       2,
 			inputSerial:      1,
@@ -228,7 +231,7 @@ func TestUpdateDNSServer(t *testing.T) {
 		},
 		{
 			name:             "Empty NS Group Domain Or Not Primary Element Should Fail",
-			initLocalMap:    make(registrationMap),
+			initLocalRecords: []nbdns.SimpleRecord{},
 			initUpstreamMap:  make(registeredHandlerMap),
 			initSerial:       0,
 			inputSerial:      1,
@@ -250,7 +253,7 @@ func TestUpdateDNSServer(t *testing.T) {
 		},
 		{
 			name:             "Invalid NS Group Nameservers list Should Fail",
-			initLocalMap:    make(registrationMap),
+			initLocalRecords: []nbdns.SimpleRecord{},
 			initUpstreamMap:  make(registeredHandlerMap),
 			initSerial:       0,
 			inputSerial:      1,
@@ -272,7 +275,7 @@ func TestUpdateDNSServer(t *testing.T) {
 		},
 		{
 			name:             "Invalid Custom Zone Records list Should Skip",
-			initLocalMap:    make(registrationMap),
+			initLocalRecords: []nbdns.SimpleRecord{},
 			initUpstreamMap:  make(registeredHandlerMap),
 			initSerial:       0,
 			inputSerial:      1,
@@ -290,7 +293,7 @@ func TestUpdateDNSServer(t *testing.T) {
 					},
 				},
 			},
-			expectedUpstreamMap: registeredHandlerMap{generateDummyHandler(".", nameServers).id(): handlerWrapper{
+			expectedUpstreamMap: registeredHandlerMap{generateDummyHandler(".", nameServers).ID(): handlerWrapper{
 				domain:   ".",
 				handler:  dummyHandler,
 				priority: PriorityDefault,
@@ -298,9 +301,9 @@ func TestUpdateDNSServer(t *testing.T) {
 		},
 		{
 			name:             "Empty Config Should Succeed and Clean Maps",
-			initLocalMap: registrationMap{"netbird.cloud": struct{}{}},
+			initLocalRecords: []nbdns.SimpleRecord{{Name: "netbird.cloud", Type: int(dns.TypeA), Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.1"}},
 			initUpstreamMap: registeredHandlerMap{
-				generateDummyHandler(zoneRecords[0].Name, nameServers).id(): handlerWrapper{
+				generateDummyHandler(zoneRecords[0].Name, nameServers).ID(): handlerWrapper{
 					domain:   zoneRecords[0].Name,
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
@@ -310,13 +313,13 @@ func TestUpdateDNSServer(t *testing.T) {
 			inputSerial:         1,
 			inputUpdate:         nbdns.Config{ServiceEnable: true},
 			expectedUpstreamMap: make(registeredHandlerMap),
-			expectedLocalMap:    make(registrationMap),
+			expectedLocalQs:     []dns.Question{},
 		},
 		{
 			name:             "Disabled Service Should clean map",
-			initLocalMap: registrationMap{"netbird.cloud": struct{}{}},
+			initLocalRecords: []nbdns.SimpleRecord{{Name: "netbird.cloud", Type: int(dns.TypeA), Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.1"}},
 			initUpstreamMap: registeredHandlerMap{
-				generateDummyHandler(zoneRecords[0].Name, nameServers).id(): handlerWrapper{
+				generateDummyHandler(zoneRecords[0].Name, nameServers).ID(): handlerWrapper{
 					domain:   zoneRecords[0].Name,
 					handler:  dummyHandler,
 					priority: PriorityMatchDomain,
@@ -326,7 +329,7 @@ func TestUpdateDNSServer(t *testing.T) {
 			inputSerial:         1,
 			inputUpdate:         nbdns.Config{ServiceEnable: false},
 			expectedUpstreamMap: make(registeredHandlerMap),
-			expectedLocalMap:    make(registrationMap),
+			expectedLocalQs:     []dns.Question{},
 		},
 	}
 
@@ -377,7 +380,7 @@ func TestUpdateDNSServer(t *testing.T) {
 			}()
 
 			dnsServer.dnsMuxMap = testCase.initUpstreamMap
-			dnsServer.localResolver.registeredMap = testCase.initLocalMap
+			dnsServer.localResolver.Update(testCase.initLocalRecords)
 			dnsServer.updateSerial = testCase.initSerial
 
 			err = dnsServer.UpdateDNSServer(testCase.inputSerial, testCase.inputUpdate)
@@ -399,15 +402,23 @@ func TestUpdateDNSServer(t *testing.T) {
 				}
 			}
 
-			if len(dnsServer.localResolver.registeredMap) != len(testCase.expectedLocalMap) {
+			var responseMSG *dns.Msg
-				t.Fatalf("update local failed, registered map size is different than expected, want %d, got %d", len(testCase.expectedLocalMap), len(dnsServer.localResolver.registeredMap))
+			responseWriter := &test.MockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+			for _, q := range testCase.expectedLocalQs {
+				dnsServer.localResolver.ServeDNS(responseWriter, &dns.Msg{
+					Question: []dns.Question{q},
+				})
 			}
 
-			for key := range testCase.expectedLocalMap {
+			if len(testCase.expectedLocalQs) > 0 {
-				_, found := dnsServer.localResolver.registeredMap[key]
+				assert.NotNil(t, responseMSG, "response message should not be nil")
-				if !found {
+				assert.Equal(t, dns.RcodeSuccess, responseMSG.Rcode, "response code should be success")
-					t.Fatalf("update local failed, key %s was not found in the localResolver.registeredMap: %#v", key, dnsServer.localResolver.registeredMap)
+				assert.NotEmpty(t, responseMSG.Answer, "response message should have answers")
-				}
 			}
 		})
 	}
@@ -491,11 +502,12 @@ func TestDNSFakeResolverHandleUpdates(t *testing.T) {
 	dnsServer.dnsMuxMap = registeredHandlerMap{
 		"id1": handlerWrapper{
 			domain:   zoneRecords[0].Name,
-			handler:  &localResolver{},
+			handler:  &local.Resolver{},
 			priority: PriorityMatchDomain,
 		},
 	}
-	dnsServer.localResolver.registeredMap = registrationMap{"netbird.cloud": struct{}{}}
+	//dnsServer.localResolver.RegisteredMap = local.RegistrationMap{local.BuildRecordKey("netbird.cloud", dns.ClassINET, dns.TypeA): struct{}{}}
+	dnsServer.localResolver.Update([]nbdns.SimpleRecord{{Name: "netbird.cloud", Type: int(dns.TypeA), Class: nbdns.DefaultClass, TTL: 300, RData: "10.0.0.1"}})
 	dnsServer.updateSerial = 0
 
 	nameServers := []nbdns.NameServer{
@@ -582,7 +594,7 @@ func TestDNSServerStartStop(t *testing.T) {
 			}
 			time.Sleep(100 * time.Millisecond)
 			defer dnsServer.Stop()
-			_, err = dnsServer.localResolver.registerRecord(zoneRecords[0])
+			err = dnsServer.localResolver.RegisterRecord(zoneRecords[0])
 			if err != nil {
 				t.Error(err)
 			}
@@ -632,9 +644,7 @@ func TestDNSServerUpstreamDeactivateCallback(t *testing.T) {
 	server := DefaultServer{
 		ctx:           context.Background(),
 		service:       NewServiceViaMemory(&mocWGIface{}),
-		localResolver: &localResolver{
+		localResolver: local.NewResolver(),
-			registeredMap: make(registrationMap),
-		},
 		handlerChain:  NewHandlerChain(),
 		hostManager:   hostManager,
 		currentConfig: HostDNSConfig{
@@ -1004,7 +1014,7 @@ func TestHandlerChain_DomainPriorities(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			r := new(dns.Msg)
 			r.SetQuestion(tc.query, dns.TypeA)
-			w := &ResponseWriterChain{ResponseWriter: &mockResponseWriter{}}
+			w := &ResponseWriterChain{ResponseWriter: &test.MockResponseWriter{}}
 
 			if mh, ok := tc.expectedHandler.(*MockHandler); ok {
 				mh.On("ServeDNS", mock.Anything, r).Once()
@@ -1037,9 +1047,9 @@ type mockHandler struct {
 }
 
 func (m *mockHandler) ServeDNS(dns.ResponseWriter, *dns.Msg) {}
-func (m *mockHandler) stop()                                 {}
+func (m *mockHandler) Stop()                                 {}
-func (m *mockHandler) probeAvailability()                    {}
+func (m *mockHandler) ProbeAvailability()                    {}
-func (m *mockHandler) id() handlerID                         { return handlerID(m.Id) }
+func (m *mockHandler) ID() types.HandlerID                   { return types.HandlerID(m.Id) }
 
 type mockService struct{}
 
@@ -1113,7 +1123,7 @@ func TestDefaultServer_UpdateMux(t *testing.T) {
 		name             string
 		initialHandlers  registeredHandlerMap
 		updates          []handlerWrapper
-		expectedHandlers map[string]string // map[handlerID]domain
+		expectedHandlers map[string]string // map[HandlerID]domain
 		description      string
 	}{
 		{
@@ -1409,7 +1419,7 @@ func TestDefaultServer_UpdateMux(t *testing.T) {
 
 			// Check each expected handler
 			for id, expectedDomain := range tt.expectedHandlers {
-				handler, exists := server.dnsMuxMap[handlerID(id)]
+				handler, exists := server.dnsMuxMap[types.HandlerID(id)]
 				assert.True(t, exists, "Expected handler %s not found", id)
 				if exists {
 					assert.Equal(t, expectedDomain, handler.domain,
@@ -1418,9 +1428,9 @@ func TestDefaultServer_UpdateMux(t *testing.T) {
 			}
 
 			// Verify no unexpected handlers exist
-			for handlerID := range server.dnsMuxMap {
+			for HandlerID := range server.dnsMuxMap {
-				_, expected := tt.expectedHandlers[string(handlerID)]
+				_, expected := tt.expectedHandlers[string(HandlerID)]
-				assert.True(t, expected, "Unexpected handler found: %s", handlerID)
+				assert.True(t, expected, "Unexpected handler found: %s", HandlerID)
 			}
 
 			// Verify the handlerChain state and order
@@ -1696,7 +1706,7 @@ func TestExtraDomains(t *testing.T) {
 				handlerChain:   NewHandlerChain(),
 				wgInterface:    &mocWGIface{},
 				hostManager:    mockHostConfig,
-				localResolver:  &localResolver{},
+				localResolver:  &local.Resolver{},
 				service:        mockSvc,
 				statusRecorder: peer.NewRecorder("test"),
 				extraDomains:   make(map[domain.Domain]int),
@@ -1781,7 +1791,7 @@ func TestExtraDomainsRefCounting(t *testing.T) {
 		ctx:            context.Background(),
 		handlerChain:   NewHandlerChain(),
 		hostManager:    mockHostConfig,
-		localResolver:  &localResolver{},
+		localResolver:  &local.Resolver{},
 		service:        mockSvc,
 		statusRecorder: peer.NewRecorder("test"),
 		extraDomains:   make(map[domain.Domain]int),
@@ -1833,7 +1843,7 @@ func TestUpdateConfigWithExistingExtraDomains(t *testing.T) {
 		ctx:            context.Background(),
 		handlerChain:   NewHandlerChain(),
 		hostManager:    mockHostConfig,
-		localResolver:  &localResolver{},
+		localResolver:  &local.Resolver{},
 		service:        mockSvc,
 		statusRecorder: peer.NewRecorder("test"),
 		extraDomains:   make(map[domain.Domain]int),
@@ -1916,7 +1926,7 @@ func TestDomainCaseHandling(t *testing.T) {
 		ctx:            context.Background(),
 		handlerChain:   NewHandlerChain(),
 		hostManager:    mockHostConfig,
-		localResolver:  &localResolver{},
+		localResolver:  &local.Resolver{},
 		service:        mockSvc,
 		statusRecorder: peer.NewRecorder("test"),
 		extraDomains:   make(map[domain.Domain]int),

client/internal/dns/test/mock.go

@@ -0,0 +1,26 @@
+package test
+
+import (
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+type MockResponseWriter struct {
+	WriteMsgFunc func(m *dns.Msg) error
+}
+
+func (rw *MockResponseWriter) WriteMsg(m *dns.Msg) error {
+	if rw.WriteMsgFunc != nil {
+		return rw.WriteMsgFunc(m)
+	}
+	return nil
+}
+
+func (rw *MockResponseWriter) LocalAddr() net.Addr       { return nil }
+func (rw *MockResponseWriter) RemoteAddr() net.Addr      { return nil }
+func (rw *MockResponseWriter) Write([]byte) (int, error) { return 0, nil }
+func (rw *MockResponseWriter) Close() error              { return nil }
+func (rw *MockResponseWriter) TsigStatus() error         { return nil }
+func (rw *MockResponseWriter) TsigTimersOnly(bool)       {}
+func (rw *MockResponseWriter) Hijack()                   {}

client/internal/dns/types/types.go

@@ -0,0 +1,3 @@
+package types
+
+type HandlerID string

client/internal/dns/upstream.go

@@ -19,6 +19,7 @@ import (
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/client/iface"
+	"github.com/netbirdio/netbird/client/internal/dns/types"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/proto"
 )
@@ -81,21 +82,21 @@ func (u *upstreamResolverBase) String() string {
 }
 
 // ID returns the unique handler ID
-func (u *upstreamResolverBase) id() handlerID {
+func (u *upstreamResolverBase) ID() types.HandlerID {
 	servers := slices.Clone(u.upstreamServers)
 	slices.Sort(servers)
 
 	hash := sha256.New()
 	hash.Write([]byte(u.domain + ":"))
 	hash.Write([]byte(strings.Join(servers, ",")))
-	return handlerID("upstream-" + hex.EncodeToString(hash.Sum(nil)[:8]))
+	return types.HandlerID("upstream-" + hex.EncodeToString(hash.Sum(nil)[:8]))
 }
 
 func (u *upstreamResolverBase) MatchSubdomains() bool {
 	return true
 }
 
-func (u *upstreamResolverBase) stop() {
+func (u *upstreamResolverBase) Stop() {
 	log.Debugf("stopping serving DNS for upstreams %s", u.upstreamServers)
 	u.cancel()
 }
@@ -198,9 +199,9 @@ func (u *upstreamResolverBase) checkUpstreamFails(err error) {
 	)
 }
 
-// probeAvailability tests all upstream servers simultaneously and
+// ProbeAvailability tests all upstream servers simultaneously and
 // disables the resolver if none work
-func (u *upstreamResolverBase) probeAvailability() {
+func (u *upstreamResolverBase) ProbeAvailability() {
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
 

client/internal/dns/upstream_test.go

@@ -8,6 +8,8 @@ import (
 	"time"
 
 	"github.com/miekg/dns"
+
+	"github.com/netbirdio/netbird/client/internal/dns/test"
 )
 
 func TestUpstreamResolver_ServeDNS(t *testing.T) {
@@ -66,7 +68,7 @@ func TestUpstreamResolver_ServeDNS(t *testing.T) {
 			}
 
 			var responseMSG *dns.Msg
-			responseWriter := &mockResponseWriter{
+			responseWriter := &test.MockResponseWriter{
 				WriteMsgFunc: func(m *dns.Msg) error {
 					responseMSG = m
 					return nil
@@ -130,7 +132,7 @@ func TestUpstreamResolver_DeactivationReactivation(t *testing.T) {
 	resolver.failsTillDeact = 0
 	resolver.reactivatePeriod = time.Microsecond * 100
 
-	responseWriter := &mockResponseWriter{
+	responseWriter := &test.MockResponseWriter{
 		WriteMsgFunc: func(m *dns.Msg) error { return nil },
 	}
 

dns/dns.go

@@ -66,17 +66,17 @@ func (s SimpleRecord) String() string {
 func (s SimpleRecord) Len() uint16 {
 	emptyString := s.RData == ""
 	switch s.Type {
-	case 1:
+	case int(dns.TypeA):
 		if emptyString {
 			return 0
 		}
 		return net.IPv4len
-	case 5:
+	case int(dns.TypeCNAME):
 		if emptyString || s.RData == "." {
 			return 1
 		}
 		return uint16(len(s.RData) + 1)
-	case 28:
+	case int(dns.TypeAAAA):
 		if emptyString {
 			return 0
 		}