[client] Fix local resolver returning error for existing domains with other types (#3959)

client/internal/dns/local/local.go

@@ -12,16 +12,19 @@ import (
 
 	"github.com/netbirdio/netbird/client/internal/dns/types"
 	nbdns "github.com/netbirdio/netbird/dns"
+	"github.com/netbirdio/netbird/management/domain"
 )
 
 type Resolver struct {
 	mu      sync.RWMutex
 	records map[dns.Question][]dns.RR
+	domains map[domain.Domain]struct{}
 }
 
 func NewResolver() *Resolver {
 	return &Resolver{
 		records: make(map[dns.Question][]dns.RR),
+		domains: make(map[domain.Domain]struct{}),
 	}
 }
 
@@ -64,8 +67,12 @@ func (d *Resolver) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
 		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
+		// Check if we have any records for this domain name with different types
+		if d.hasRecordsForDomain(domain.Domain(question.Name)) {
+			replyMessage.Rcode = dns.RcodeSuccess // NOERROR with 0 records
+		} else {
+			replyMessage.Rcode = dns.RcodeNameError // NXDOMAIN
+		}
 	}
 
 	if err := w.WriteMsg(replyMessage); err != nil {
@@ -73,6 +80,15 @@ func (d *Resolver) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
 	}
 }
 
+// hasRecordsForDomain checks if any records exist for the given domain name regardless of type
+func (d *Resolver) hasRecordsForDomain(domainName domain.Domain) bool {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+
+	_, exists := d.domains[domainName]
+	return exists
+}
+
 // lookupRecords fetches *all* DNS records matching the first question in r.
 func (d *Resolver) lookupRecords(question dns.Question) []dns.RR {
 	d.mu.RLock()
@@ -111,6 +127,7 @@ func (d *Resolver) Update(update []nbdns.SimpleRecord) {
 	defer d.mu.Unlock()
 
 	maps.Clear(d.records)
+	maps.Clear(d.domains)
 
 	for _, rec := range update {
 		if err := d.registerRecord(rec); err != nil {
@@ -144,6 +161,7 @@ func (d *Resolver) registerRecord(record nbdns.SimpleRecord) error {
 	}
 
 	d.records[q] = append(d.records[q], rr)
+	d.domains[domain.Domain(q.Name)] = struct{}{}
 
 	return nil
 }

client/internal/dns/local/local_test.go

@@ -470,3 +470,115 @@ func TestLocalResolver_CNAMEFallback(t *testing.T) {
 		})
 	}
 }
+
+// TestLocalResolver_NoErrorWithDifferentRecordType verifies that querying for a record type
+// that doesn't exist but where other record types exist for the same domain returns NOERROR
+// with 0 records instead of NXDOMAIN
+func TestLocalResolver_NoErrorWithDifferentRecordType(t *testing.T) {
+	resolver := NewResolver()
+
+	recordA := nbdns.SimpleRecord{
+		Name:  "example.netbird.cloud.",
+		Type:  int(dns.TypeA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "192.168.1.100",
+	}
+
+	recordCNAME := nbdns.SimpleRecord{
+		Name:  "alias.netbird.cloud.",
+		Type:  int(dns.TypeCNAME),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "target.example.com.",
+	}
+
+	resolver.Update([]nbdns.SimpleRecord{recordA, recordCNAME})
+
+	testCases := []struct {
+		name           string
+		queryName      string
+		queryType      uint16
+		expectedRcode  int
+		shouldHaveData bool
+	}{
+		{
+			name:           "Query A record that exists",
+			queryName:      "example.netbird.cloud.",
+			queryType:      dns.TypeA,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: true,
+		},
+		{
+			name:           "Query AAAA for domain with only A record",
+			queryName:      "example.netbird.cloud.",
+			queryType:      dns.TypeAAAA,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: false,
+		},
+		{
+			name:           "Query other record with different case and non-fqdn",
+			queryName:      "EXAMPLE.netbird.cloud",
+			queryType:      dns.TypeAAAA,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: false,
+		},
+		{
+			name:           "Query TXT for domain with only A record",
+			queryName:      "example.netbird.cloud.",
+			queryType:      dns.TypeTXT,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: false,
+		},
+		{
+			name:           "Query A for domain with only CNAME record",
+			queryName:      "alias.netbird.cloud.",
+			queryType:      dns.TypeA,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: true,
+		},
+		{
+			name:           "Query AAAA for domain with only CNAME record",
+			queryName:      "alias.netbird.cloud.",
+			queryType:      dns.TypeAAAA,
+			expectedRcode:  dns.RcodeSuccess,
+			shouldHaveData: true,
+		},
+		{
+			name:           "Query for completely non-existent domain",
+			queryName:      "nonexistent.netbird.cloud.",
+			queryType:      dns.TypeA,
+			expectedRcode:  dns.RcodeNameError,
+			shouldHaveData: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var responseMSG *dns.Msg
+
+			msg := new(dns.Msg).SetQuestion(tc.queryName, tc.queryType)
+
+			responseWriter := &test.MockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+
+			resolver.ServeDNS(responseWriter, msg)
+
+			require.NotNil(t, responseMSG, "Should have received a response message")
+
+			assert.Equal(t, tc.expectedRcode, responseMSG.Rcode,
+				"Response code should be %d (%s)",
+				tc.expectedRcode, dns.RcodeToString[tc.expectedRcode])
+
+			if tc.shouldHaveData {
+				assert.Greater(t, len(responseMSG.Answer), 0, "Response should contain answers")
+			} else {
+				assert.Equal(t, 0, len(responseMSG.Answer), "Response should contain no answers")
+			}
+		})
+	}
+}