[client] Forward non-address DNS record types through route forwarders (#6455)

client/internal/dns/resutil/resolve.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"net"
 	"net/netip"
+	"slices"
 	"strings"
 
 	"github.com/miekg/dns"
@@ -167,7 +168,10 @@ func getRcodeForNotFound(ctx context.Context, r resolver, domain string, origina
 	case dns.TypeA:
 		alternativeNetwork = "ip6"
 	default:
-		return dns.RcodeNameError
+		// Non-address types reach LookupIP only unexpectedly; without an
+		// address pair to probe we cannot prove the name is absent, so answer
+		// NODATA rather than a poisoning NXDOMAIN.
+		return dns.RcodeSuccess
 	}
 
 	if _, err := r.LookupNetIP(ctx, alternativeNetwork, domain); err != nil {
@@ -184,6 +188,230 @@ func getRcodeForNotFound(ctx context.Context, r resolver, domain string, origina
 	return dns.RcodeSuccess
 }
 
+// RecordResolver is the host resolver surface used to forward non-address
+// record queries. net.DefaultResolver satisfies it.
+type RecordResolver interface {
+	LookupMX(ctx context.Context, name string) ([]*net.MX, error)
+	LookupTXT(ctx context.Context, name string) ([]string, error)
+	LookupNS(ctx context.Context, name string) ([]*net.NS, error)
+	LookupSRV(ctx context.Context, service, proto, name string) (string, []*net.SRV, error)
+	LookupCNAME(ctx context.Context, host string) (string, error)
+	LookupAddr(ctx context.Context, addr string) ([]string, error)
+}
+
+// LookupRecords resolves a non-address DNS record type through the host
+// resolver and returns the resource records and the DNS rcode. Types the host
+// resolver cannot answer (anything not covered by the net.Resolver Lookup*
+// methods) yield NODATA so that a routed name is never poisoned with NXDOMAIN
+// for an unsupported type.
+func LookupRecords(ctx context.Context, r RecordResolver, name string, qtype uint16, ttl uint32) ([]dns.RR, int) {
+	fqdn := dns.Fqdn(name)
+
+	switch qtype {
+	case dns.TypeMX:
+		return lookupMX(ctx, r, name, fqdn, ttl)
+	case dns.TypeTXT:
+		return lookupTXT(ctx, r, name, fqdn, ttl)
+	case dns.TypeNS:
+		return lookupNS(ctx, r, name, fqdn, ttl)
+	case dns.TypeSRV:
+		return lookupSRV(ctx, r, name, fqdn, ttl)
+	case dns.TypeCNAME:
+		return lookupCNAME(ctx, r, name, fqdn, ttl)
+	case dns.TypePTR:
+		return lookupPTR(ctx, r, name, fqdn, ttl)
+	default:
+		return nil, dns.RcodeSuccess
+	}
+}
+
+func recordHeader(fqdn string, rrtype uint16, ttl uint32) dns.RR_Header {
+	return dns.RR_Header{Name: fqdn, Rrtype: rrtype, Class: dns.ClassINET, Ttl: ttl}
+}
+
+func lookupMX(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	recs, err := r.LookupMX(ctx, name)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	rrs := make([]dns.RR, 0, len(recs))
+	for _, mx := range recs {
+		rrs = append(rrs, &dns.MX{
+			Hdr:        recordHeader(fqdn, dns.TypeMX, ttl),
+			Preference: mx.Pref,
+			Mx:         dns.Fqdn(mx.Host),
+		})
+	}
+	return rrs, dns.RcodeSuccess
+}
+
+func lookupTXT(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	recs, err := r.LookupTXT(ctx, name)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	rrs := make([]dns.RR, 0, len(recs))
+	for _, txt := range recs {
+		rrs = append(rrs, &dns.TXT{
+			Hdr: recordHeader(fqdn, dns.TypeTXT, ttl),
+			Txt: chunkTXT(txt),
+		})
+	}
+	return rrs, dns.RcodeSuccess
+}
+
+func lookupNS(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	recs, err := r.LookupNS(ctx, name)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	rrs := make([]dns.RR, 0, len(recs))
+	for _, ns := range recs {
+		rrs = append(rrs, &dns.NS{
+			Hdr: recordHeader(fqdn, dns.TypeNS, ttl),
+			Ns:  dns.Fqdn(ns.Host),
+		})
+	}
+	return rrs, dns.RcodeSuccess
+}
+
+func lookupSRV(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	_, recs, err := r.LookupSRV(ctx, "", "", name)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	rrs := make([]dns.RR, 0, len(recs))
+	for _, srv := range recs {
+		rrs = append(rrs, &dns.SRV{
+			Hdr:      recordHeader(fqdn, dns.TypeSRV, ttl),
+			Priority: srv.Priority,
+			Weight:   srv.Weight,
+			Port:     srv.Port,
+			Target:   dns.Fqdn(srv.Target),
+		})
+	}
+	return rrs, dns.RcodeSuccess
+}
+
+func lookupCNAME(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	cname, err := r.LookupCNAME(ctx, name)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	// LookupCNAME returns the queried name itself when the name resolves but
+	// has no CNAME record; that is a NODATA result, not a CNAME.
+	if strings.EqualFold(dns.Fqdn(cname), fqdn) {
+		return nil, dns.RcodeSuccess
+	}
+	return []dns.RR{&dns.CNAME{
+		Hdr:    recordHeader(fqdn, dns.TypeCNAME, ttl),
+		Target: dns.Fqdn(cname),
+	}}, dns.RcodeSuccess
+}
+
+func lookupPTR(ctx context.Context, r RecordResolver, name, fqdn string, ttl uint32) ([]dns.RR, int) {
+	addr, ok := ptrQueryAddr(name)
+	if !ok {
+		return nil, dns.RcodeSuccess
+	}
+	names, err := r.LookupAddr(ctx, addr)
+	if err != nil {
+		return nil, rcodeForRecordError(err)
+	}
+	rrs := make([]dns.RR, 0, len(names))
+	for _, n := range names {
+		rrs = append(rrs, &dns.PTR{
+			Hdr: recordHeader(fqdn, dns.TypePTR, ttl),
+			Ptr: dns.Fqdn(n),
+		})
+	}
+	return rrs, dns.RcodeSuccess
+}
+
+// ptrQueryAddr converts a reverse-DNS query name (in-addr.arpa or ip6.arpa)
+// into the address string expected by net.Resolver.LookupAddr. It reports false
+// when the name is not a well-formed reverse name.
+func ptrQueryAddr(qname string) (string, bool) {
+	name := strings.TrimSuffix(strings.ToLower(dns.Fqdn(qname)), ".")
+
+	switch {
+	case strings.HasSuffix(name, ".in-addr.arpa"):
+		return parseInAddrArpa(strings.TrimSuffix(name, ".in-addr.arpa"))
+	case strings.HasSuffix(name, ".ip6.arpa"):
+		return parseIP6Arpa(strings.TrimSuffix(name, ".ip6.arpa"))
+	default:
+		return "", false
+	}
+}
+
+// parseInAddrArpa turns the label portion of an in-addr.arpa name into an IPv4
+// address string, reporting false when it is not a well-formed reverse name.
+func parseInAddrArpa(labelPart string) (string, bool) {
+	labels := strings.Split(labelPart, ".")
+	if len(labels) != 4 {
+		return "", false
+	}
+	slices.Reverse(labels)
+	addr, err := netip.ParseAddr(strings.Join(labels, "."))
+	if err != nil || !addr.Is4() {
+		return "", false
+	}
+	return addr.String(), true
+}
+
+// parseIP6Arpa turns the nibble portion of an ip6.arpa name into an IPv6
+// address string, reporting false when it is not a well-formed reverse name.
+func parseIP6Arpa(nibblePart string) (string, bool) {
+	nibbles := strings.Split(nibblePart, ".")
+	if len(nibbles) != 32 {
+		return "", false
+	}
+	slices.Reverse(nibbles)
+	var sb strings.Builder
+	for i, n := range nibbles {
+		if i > 0 && i%4 == 0 {
+			sb.WriteByte(':')
+		}
+		sb.WriteString(n)
+	}
+	addr, err := netip.ParseAddr(sb.String())
+	if err != nil || !addr.Is6() {
+		return "", false
+	}
+	return addr.String(), true
+}
+
+// rcodeForRecordError maps a non-address lookup error to a DNS rcode. A
+// not-found result becomes NODATA rather than NXDOMAIN: net.DNSError.IsNotFound
+// does not distinguish a missing name from a name that exists only with records
+// of other types, so the name cannot be proven absent and must not be poisoned.
+func rcodeForRecordError(err error) int {
+	var dnsErr *net.DNSError
+	if errors.As(err, &dnsErr) && dnsErr.IsNotFound {
+		return dns.RcodeSuccess
+	}
+	return dns.RcodeServerFailure
+}
+
+// chunkTXT splits a TXT string into character-strings no longer than 255 bytes
+// so the record can be packed. The chunks form one TXT resource record.
+func chunkTXT(s string) []string {
+	const maxLen = 255
+	if len(s) <= maxLen {
+		return []string{s}
+	}
+
+	var chunks []string
+	for len(s) > maxLen {
+		chunks = append(chunks, s[:maxLen])
+		s = s[maxLen:]
+	}
+	if len(s) > 0 {
+		chunks = append(chunks, s)
+	}
+	return chunks
+}
+
 // FormatAnswers formats DNS resource records for logging.
 func FormatAnswers(answers []dns.RR) string {
 	if len(answers) == 0 {

client/internal/dns/resutil/resolve_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"net"
 	"net/netip"
+	"strings"
 	"testing"
 
 	"github.com/miekg/dns"
@@ -121,6 +122,164 @@ func TestLookupIP_DNSErrorNotIsNotFound(t *testing.T) {
 	assert.Equal(t, dns.RcodeServerFailure, result.Rcode, "upstream failure should map to SERVFAIL")
 }
 
+func TestPtrQueryAddr(t *testing.T) {
+	tests := []struct {
+		name   string
+		qname  string
+		want   string
+		wantOK bool
+	}{
+		{name: "ipv4", qname: "4.3.2.1.in-addr.arpa.", want: "1.2.3.4", wantOK: true},
+		{name: "ipv4 no trailing dot", qname: "1.0.0.127.in-addr.arpa", want: "127.0.0.1", wantOK: true},
+		{
+			name:   "ipv6",
+			qname:  "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			want:   "2001:db8::1",
+			wantOK: true,
+		},
+		{name: "ipv4 wrong label count", qname: "2.1.in-addr.arpa.", wantOK: false},
+		{name: "ipv6 wrong nibble count", qname: "1.0.ip6.arpa.", wantOK: false},
+		{name: "not a reverse name", qname: "example.com.", wantOK: false},
+		{name: "ipv4 bad octet", qname: "4.3.2.999.in-addr.arpa.", wantOK: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := ptrQueryAddr(tt.qname)
+			assert.Equal(t, tt.wantOK, ok, "parse success mismatch")
+			if tt.wantOK {
+				assert.Equal(t, tt.want, got, "parsed address mismatch")
+			}
+		})
+	}
+}
+
+type mockRecordResolver struct {
+	mx    []*net.MX
+	txt   []string
+	ns    []*net.NS
+	srv   []*net.SRV
+	cname string
+	ptr   []string
+	err   error
+}
+
+func (m *mockRecordResolver) LookupMX(context.Context, string) ([]*net.MX, error) {
+	return m.mx, m.err
+}
+func (m *mockRecordResolver) LookupTXT(context.Context, string) ([]string, error) {
+	return m.txt, m.err
+}
+func (m *mockRecordResolver) LookupNS(context.Context, string) ([]*net.NS, error) {
+	return m.ns, m.err
+}
+func (m *mockRecordResolver) LookupSRV(context.Context, string, string, string) (string, []*net.SRV, error) {
+	return "", m.srv, m.err
+}
+func (m *mockRecordResolver) LookupCNAME(context.Context, string) (string, error) {
+	return m.cname, m.err
+}
+func (m *mockRecordResolver) LookupAddr(context.Context, string) ([]string, error) {
+	return m.ptr, m.err
+}
+
+func TestLookupRecords(t *testing.T) {
+	notFound := &net.DNSError{IsNotFound: true, Name: "example.com."}
+
+	t.Run("MX success", func(t *testing.T) {
+		r := &mockRecordResolver{mx: []*net.MX{{Host: "mail.example.com.", Pref: 10}}}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeMX, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, "mail.example.com.", rrs[0].(*dns.MX).Mx)
+	})
+
+	t.Run("TXT short string is one character-string", func(t *testing.T) {
+		r := &mockRecordResolver{txt: []string{"v=spf1 -all"}}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeTXT, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, []string{"v=spf1 -all"}, rrs[0].(*dns.TXT).Txt)
+	})
+
+	t.Run("TXT chunks long strings", func(t *testing.T) {
+		long := strings.Repeat("a", 300)
+		r := &mockRecordResolver{txt: []string{long}}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeTXT, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		txt := rrs[0].(*dns.TXT).Txt
+		require.Len(t, txt, 2, "300-byte string should split into two character-strings")
+		assert.Equal(t, 255, len(txt[0]))
+		assert.Equal(t, 45, len(txt[1]))
+	})
+
+	t.Run("NS success", func(t *testing.T) {
+		r := &mockRecordResolver{ns: []*net.NS{{Host: "ns1.example.com."}}}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeNS, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, "ns1.example.com.", rrs[0].(*dns.NS).Ns)
+	})
+
+	t.Run("SRV success", func(t *testing.T) {
+		r := &mockRecordResolver{srv: []*net.SRV{{Target: "sip.example.com.", Port: 5060}}}
+		rrs, rcode := LookupRecords(context.Background(), r, "_sip._tcp.example.com.", dns.TypeSRV, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, uint16(5060), rrs[0].(*dns.SRV).Port)
+	})
+
+	t.Run("CNAME success", func(t *testing.T) {
+		r := &mockRecordResolver{cname: "target.example.com."}
+		rrs, rcode := LookupRecords(context.Background(), r, "www.example.com.", dns.TypeCNAME, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, "target.example.com.", rrs[0].(*dns.CNAME).Target)
+	})
+
+	t.Run("CNAME equal to name is NODATA", func(t *testing.T) {
+		r := &mockRecordResolver{cname: "example.com."}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeCNAME, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		assert.Empty(t, rrs, "self-referential CNAME is NODATA")
+	})
+
+	t.Run("PTR success", func(t *testing.T) {
+		r := &mockRecordResolver{ptr: []string{"host.example.com."}}
+		rrs, rcode := LookupRecords(context.Background(), r, "4.3.2.1.in-addr.arpa.", dns.TypePTR, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		require.Len(t, rrs, 1)
+		assert.Equal(t, "host.example.com.", rrs[0].(*dns.PTR).Ptr)
+	})
+
+	t.Run("PTR malformed name is NODATA", func(t *testing.T) {
+		r := &mockRecordResolver{}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypePTR, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		assert.Empty(t, rrs)
+	})
+
+	t.Run("not found is NODATA never NXDOMAIN", func(t *testing.T) {
+		r := &mockRecordResolver{err: notFound}
+		_, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeMX, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode, "missing record must not poison the name")
+	})
+
+	t.Run("server failure maps to SERVFAIL", func(t *testing.T) {
+		r := &mockRecordResolver{err: &net.DNSError{Err: "server misbehaving", IsTemporary: true}}
+		_, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeMX, 300)
+		assert.Equal(t, dns.RcodeServerFailure, rcode)
+	})
+
+	t.Run("unsupported type is NODATA", func(t *testing.T) {
+		r := &mockRecordResolver{}
+		rrs, rcode := LookupRecords(context.Background(), r, "example.com.", dns.TypeCAA, 300)
+		assert.Equal(t, dns.RcodeSuccess, rcode)
+		assert.Empty(t, rrs)
+	})
+}
+
 func TestStripOPT(t *testing.T) {
 	rm := &dns.Msg{
 		Extra: []dns.RR{

client/internal/dnsfwd/forwarder.go

@@ -37,6 +37,12 @@ const (
 
 type resolver interface {
 	LookupNetIP(ctx context.Context, network, host string) ([]netip.Addr, error)
+	LookupMX(ctx context.Context, name string) ([]*net.MX, error)
+	LookupTXT(ctx context.Context, name string) ([]string, error)
+	LookupNS(ctx context.Context, name string) ([]*net.NS, error)
+	LookupSRV(ctx context.Context, service, proto, name string) (string, []*net.SRV, error)
+	LookupCNAME(ctx context.Context, host string) (string, error)
+	LookupAddr(ctx context.Context, addr string) ([]string, error)
 }
 
 type firewaller interface {
@@ -210,12 +216,6 @@ func (f *DNSForwarder) handleDNSQuery(logger *log.Entry, w dns.ResponseWriter, q
 		qname, dns.TypeToString[question.Qtype], dns.ClassToString[question.Qclass])
 
 	resp := query.SetReply(query)
-	network := resutil.NetworkForQtype(question.Qtype)
-	if network == "" {
-		resp.Rcode = dns.RcodeNotImplemented
-		f.writeResponse(logger, w, resp, qname, startTime)
-		return
-	}
 
 	mostSpecificResId, matchingEntries := f.getMatchingEntries(strings.TrimSuffix(qname, "."))
 	if mostSpecificResId == "" {
@@ -227,9 +227,46 @@ func (f *DNSForwarder) handleDNSQuery(logger *log.Entry, w dns.ResponseWriter, q
 	ctx, cancel := context.WithTimeout(context.Background(), upstreamTimeout)
 	defer cancel()
 
+	reqHasEdns := query.IsEdns0() != nil
+
+	switch question.Qtype {
+	case dns.TypeA, dns.TypeAAAA:
+		f.handleAddressQuery(ctx, logger, w, resp, mostSpecificResId, matchingEntries, reqHasEdns, startTime)
+	case dns.TypeMX, dns.TypeTXT, dns.TypeNS, dns.TypeSRV, dns.TypeCNAME, dns.TypePTR:
+		f.handleRecordQuery(ctx, logger, w, resp, startTime)
+	default:
+		// The domain is routed here, so any other type is answered NODATA
+		// (NOERROR, empty answer) rather than falling back to a resolver that
+		// would poison the name with NXDOMAIN. The Extended DNS Error lets a
+		// client tell this capability-driven NODATA apart from an
+		// authoritative one. The OPT pseudo-record must not appear unless the
+		// query advertised EDNS0.
+		if reqHasEdns {
+			attachEDE(resp, dns.ExtendedErrorCodeNotSupported, "netbird forwarder: unsupported query type")
+		}
+		f.writeResponse(logger, w, resp, qname, startTime)
+	}
+}
+
+// handleAddressQuery resolves A/AAAA queries, programs the firewall sets and
+// resolved-IP state, and caches the answer for resilience on upstream failure.
+func (f *DNSForwarder) handleAddressQuery(
+	ctx context.Context,
+	logger *log.Entry,
+	w dns.ResponseWriter,
+	resp *dns.Msg,
+	mostSpecificResId route.ResID,
+	matchingEntries []*ForwarderEntry,
+	reqHasEdns bool,
+	startTime time.Time,
+) {
+	question := resp.Question[0]
+	qname := strings.ToLower(question.Name)
+
+	network := resutil.NetworkForQtype(question.Qtype)
 	result := resutil.LookupIP(ctx, f.resolver, network, qname, question.Qtype)
 	if result.Err != nil {
-		f.handleDNSError(ctx, logger, w, question, resp, qname, result, query.IsEdns0() != nil, startTime)
+		f.handleDNSError(ctx, logger, w, question, resp, qname, result, reqHasEdns, startTime)
 		return
 	}
 
@@ -240,6 +277,25 @@ func (f *DNSForwarder) handleDNSQuery(logger *log.Entry, w dns.ResponseWriter, q
 	f.writeResponse(logger, w, resp, qname, startTime)
 }
 
+// handleRecordQuery resolves non-address record types (MX, TXT, NS, SRV,
+// CNAME, PTR) through the host resolver. Missing records are answered NODATA so
+// the routed name is never poisoned with NXDOMAIN.
+func (f *DNSForwarder) handleRecordQuery(
+	ctx context.Context,
+	logger *log.Entry,
+	w dns.ResponseWriter,
+	resp *dns.Msg,
+	startTime time.Time,
+) {
+	question := resp.Question[0]
+	qname := strings.ToLower(question.Name)
+
+	records, rcode := resutil.LookupRecords(ctx, f.resolver, qname, question.Qtype, f.ttl)
+	resp.Rcode = rcode
+	resp.Answer = append(resp.Answer, records...)
+	f.writeResponse(logger, w, resp, qname, startTime)
+}
+
 func (f *DNSForwarder) writeResponse(logger *log.Entry, w dns.ResponseWriter, resp *dns.Msg, qname string, startTime time.Time) {
 	if err := w.WriteMsg(resp); err != nil {
 		logger.Errorf("failed to write DNS response: %v", err)

client/internal/dnsfwd/forwarder_test.go

@@ -133,6 +133,41 @@ func (m *MockResolver) LookupNetIP(ctx context.Context, network, host string) ([
 	return args.Get(0).([]netip.Addr), args.Error(1)
 }
 
+func (m *MockResolver) LookupMX(ctx context.Context, name string) ([]*net.MX, error) {
+	args := m.Called(ctx, name)
+	recs, _ := args.Get(0).([]*net.MX)
+	return recs, args.Error(1)
+}
+
+func (m *MockResolver) LookupTXT(ctx context.Context, name string) ([]string, error) {
+	args := m.Called(ctx, name)
+	recs, _ := args.Get(0).([]string)
+	return recs, args.Error(1)
+}
+
+func (m *MockResolver) LookupNS(ctx context.Context, name string) ([]*net.NS, error) {
+	args := m.Called(ctx, name)
+	recs, _ := args.Get(0).([]*net.NS)
+	return recs, args.Error(1)
+}
+
+func (m *MockResolver) LookupSRV(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+	args := m.Called(ctx, service, proto, name)
+	recs, _ := args.Get(1).([]*net.SRV)
+	return args.String(0), recs, args.Error(2)
+}
+
+func (m *MockResolver) LookupCNAME(ctx context.Context, host string) (string, error) {
+	args := m.Called(ctx, host)
+	return args.String(0), args.Error(1)
+}
+
+func (m *MockResolver) LookupAddr(ctx context.Context, addr string) ([]string, error) {
+	args := m.Called(ctx, addr)
+	recs, _ := args.Get(0).([]string)
+	return recs, args.Error(1)
+}
+
 func TestDNSForwarder_SubdomainAccessLogic(t *testing.T) {
 	tests := []struct {
 		name             string
@@ -545,12 +580,15 @@ func TestDNSForwarder_MultipleIPsInSingleUpdate(t *testing.T) {
 }
 
 func TestDNSForwarder_ResponseCodes(t *testing.T) {
+	// A type with no net.Resolver Lookup method (CAA) must answer NODATA
+	// (NOERROR, empty) rather than NXDOMAIN/NOTIMP to avoid poisoning the name.
 	tests := []struct {
 		name         string
 		queryType    uint16
 		queryDomain  string
 		configured   string
 		expectedCode int
+		expectEDE    bool
 		description  string
 	}{
 		{
@@ -562,28 +600,13 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 			description:  "RFC compliant REFUSED for unauthorized queries",
 		},
 		{
-			name:         "unsupported query type returns NOTIMP",
+			name:         "unsupported query type returns NODATA",
-			queryType:    dns.TypeMX,
+			queryType:    dns.TypeCAA,
 			queryDomain:  "example.com",
 			configured:   "example.com",
-			expectedCode: dns.RcodeNotImplemented,
+			expectedCode: dns.RcodeSuccess,
-			description:  "RFC compliant NOTIMP for unsupported types",
+			expectEDE:    true,
-		},
+			description:  "Unsupported types answer NODATA, not NXDOMAIN/NOTIMP",
-		{
-			name:         "CNAME query returns NOTIMP",
-			queryType:    dns.TypeCNAME,
-			queryDomain:  "example.com",
-			configured:   "example.com",
-			expectedCode: dns.RcodeNotImplemented,
-			description:  "CNAME queries not supported",
-		},
-		{
-			name:         "TXT query returns NOTIMP",
-			queryType:    dns.TypeTXT,
-			queryDomain:  "example.com",
-			configured:   "example.com",
-			expectedCode: dns.RcodeNotImplemented,
-			description:  "TXT queries not supported",
 		},
 	}
 
@@ -599,6 +622,7 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 
 			query := &dns.Msg{}
 			query.SetQuestion(dns.Fqdn(tt.queryDomain), tt.queryType)
+			query.SetEdns0(dns.DefaultMsgSize, false)
 
 			// Capture the written response
 			var writtenResp *dns.Msg
@@ -614,10 +638,213 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 			// Check the response written to the writer
 			require.NotNil(t, writtenResp, "Expected response to be written")
 			assert.Equal(t, tt.expectedCode, writtenResp.Rcode, tt.description)
+			assert.Empty(t, writtenResp.Answer, "Non-address response should carry no answers")
+
+			if tt.expectEDE {
+				require.NotNil(t, writtenResp.IsEdns0(), "EDNS0 client should get an OPT in the reply")
+				assert.True(t, hasEDE(writtenResp, dns.ExtendedErrorCodeNotSupported),
+					"unsupported type NODATA should carry EDE Not Supported")
+			}
 		})
 	}
 }
 
+func hasEDE(m *dns.Msg, code uint16) bool {
+	opt := m.IsEdns0()
+	if opt == nil {
+		return false
+	}
+	for _, o := range opt.Option {
+		if ede, ok := o.(*dns.EDNS0_EDE); ok && ede.InfoCode == code {
+			return true
+		}
+	}
+	return false
+}
+
+func TestDNSForwarder_RecordQueries(t *testing.T) {
+	notFound := &net.DNSError{IsNotFound: true, Name: "example.com"}
+
+	t.Run("MX records are forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		mockResolver.On("LookupMX", mock.Anything, "example.com.").
+			Return([]*net.MX{{Host: "mail.example.com.", Pref: 10}}, nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeMX)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		mx, ok := resp.Answer[0].(*dns.MX)
+		require.True(t, ok, "answer should be an MX record")
+		assert.Equal(t, uint16(10), mx.Preference)
+		assert.Equal(t, "mail.example.com.", mx.Mx)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("missing MX is NODATA not NXDOMAIN", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		// A not-found cannot prove the name is absent (it may exist with only
+		// other record types), so it must answer NODATA, never NXDOMAIN.
+		mockResolver.On("LookupMX", mock.Anything, "example.com.").
+			Return(nil, notFound).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeMX)
+		assert.Equal(t, dns.RcodeSuccess, resp.Rcode, "missing record must be NODATA")
+		assert.Empty(t, resp.Answer)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("NS records are forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		mockResolver.On("LookupNS", mock.Anything, "example.com.").
+			Return([]*net.NS{{Host: "ns1.example.com."}}, nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeNS)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		ns, ok := resp.Answer[0].(*dns.NS)
+		require.True(t, ok, "answer should be an NS record")
+		assert.Equal(t, "ns1.example.com.", ns.Ns)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("missing NS is NODATA", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		mockResolver.On("LookupNS", mock.Anything, "example.com.").
+			Return(nil, notFound).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeNS)
+		assert.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		assert.Empty(t, resp.Answer)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("SRV records are forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "_sip._tcp.example.com")
+
+		mockResolver.On("LookupSRV", mock.Anything, "", "", "_sip._tcp.example.com.").
+			Return("", []*net.SRV{{Target: "sip.example.com.", Port: 5060, Priority: 10, Weight: 5}}, nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "_sip._tcp.example.com", dns.TypeSRV)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		srv, ok := resp.Answer[0].(*dns.SRV)
+		require.True(t, ok, "answer should be an SRV record")
+		assert.Equal(t, "sip.example.com.", srv.Target)
+		assert.Equal(t, uint16(5060), srv.Port)
+		assert.Equal(t, uint16(10), srv.Priority)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("missing SRV is NODATA", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "_sip._tcp.example.com")
+
+		mockResolver.On("LookupSRV", mock.Anything, "", "", "_sip._tcp.example.com.").
+			Return("", nil, notFound).Once()
+
+		resp := runRecordQuery(t, forwarder, "_sip._tcp.example.com", dns.TypeSRV)
+		assert.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		assert.Empty(t, resp.Answer)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("TXT records are forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		mockResolver.On("LookupTXT", mock.Anything, "example.com.").
+			Return([]string{"v=spf1 -all"}, nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeTXT)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		txt, ok := resp.Answer[0].(*dns.TXT)
+		require.True(t, ok, "answer should be a TXT record")
+		assert.Equal(t, []string{"v=spf1 -all"}, txt.Txt)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("CNAME record is forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "www.example.com")
+
+		mockResolver.On("LookupCNAME", mock.Anything, "www.example.com.").
+			Return("target.example.com.", nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "www.example.com", dns.TypeCNAME)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		cname, ok := resp.Answer[0].(*dns.CNAME)
+		require.True(t, ok, "answer should be a CNAME record")
+		assert.Equal(t, "target.example.com.", cname.Target)
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("CNAME equal to the name is NODATA", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "example.com")
+
+		// No CNAME exists: LookupCNAME echoes the queried name back.
+		mockResolver.On("LookupCNAME", mock.Anything, "example.com.").
+			Return("example.com.", nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "example.com", dns.TypeCNAME)
+		assert.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		assert.Empty(t, resp.Answer, "self-referential CNAME means no CNAME record")
+		mockResolver.AssertExpectations(t)
+	})
+
+	t.Run("PTR record is forwarded", func(t *testing.T) {
+		mockResolver := &MockResolver{}
+		forwarder := newRecordTestForwarder(t, mockResolver, "*.in-addr.arpa")
+
+		// The reverse name is parsed back to the address LookupAddr expects.
+		mockResolver.On("LookupAddr", mock.Anything, "1.2.3.4").
+			Return([]string{"host.example.com."}, nil).Once()
+
+		resp := runRecordQuery(t, forwarder, "4.3.2.1.in-addr.arpa", dns.TypePTR)
+		require.Equal(t, dns.RcodeSuccess, resp.Rcode)
+		require.Len(t, resp.Answer, 1)
+		ptr, ok := resp.Answer[0].(*dns.PTR)
+		require.True(t, ok, "answer should be a PTR record")
+		assert.Equal(t, "host.example.com.", ptr.Ptr)
+		mockResolver.AssertExpectations(t)
+	})
+}
+
+func newRecordTestForwarder(t *testing.T, r resolver, configured string) *DNSForwarder {
+	t.Helper()
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
+	forwarder.resolver = r
+
+	d, err := domain.FromString(configured)
+	require.NoError(t, err)
+	forwarder.UpdateDomains([]*ForwarderEntry{{Domain: d, ResID: "test-res"}})
+	return forwarder
+}
+
+func runRecordQuery(t *testing.T, forwarder *DNSForwarder, qname string, qtype uint16) *dns.Msg {
+	t.Helper()
+	query := &dns.Msg{}
+	query.SetQuestion(dns.Fqdn(qname), qtype)
+
+	mockWriter := &test.MockResponseWriter{}
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
+
+	resp := mockWriter.GetLastResponse()
+	require.NotNil(t, resp, "expected response to be written")
+	return resp
+}
+
 func TestDNSForwarder_UpstreamFailureEDE(t *testing.T) {
 	tests := []struct {
 		name        string

client/internal/routemanager/dnsinterceptor/handler.go

@@ -226,12 +226,11 @@ func (d *DnsInterceptor) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
 		return
 	}
 
-	// pass if non A/AAAA query
+	// All query types for an intercepted domain are forwarded to the peer's
-	if r.Question[0].Qtype != dns.TypeA && r.Question[0].Qtype != dns.TypeAAAA {
+	// DNS forwarder, which owns the name. Falling through to the system
-		d.continueToNextHandler(w, r, logger, "non A/AAAA query")
+	// resolver would let it answer NXDOMAIN for a name it isn't authoritative
-		return
+	// for, poisoning the whole name (including the A/AAAA records the route
-	}
+	// does serve). The forwarder answers NODATA for types it cannot resolve.
-
 	d.mu.RLock()
 	peerKey := d.currentPeerKey
 	d.mu.RUnlock()
@@ -293,19 +292,6 @@ func (d *DnsInterceptor) writeDNSError(w dns.ResponseWriter, r *dns.Msg, logger
 	}
 }
 
-// continueToNextHandler signals the handler chain to try the next handler
-func (d *DnsInterceptor) continueToNextHandler(w dns.ResponseWriter, r *dns.Msg, logger *log.Entry, reason string) {
-	logger.Tracef("continuing to next handler for domain=%s reason=%s", r.Question[0].Name, reason)
-
-	resp := new(dns.Msg)
-	resp.SetRcode(r, dns.RcodeNameError)
-	// Set Zero bit to signal handler chain to continue
-	resp.MsgHdr.Zero = true
-	if err := w.WriteMsg(resp); err != nil {
-		logger.Errorf("failed writing DNS continue response: %v", err)
-	}
-}
-
 func (d *DnsInterceptor) getUpstreamIP(peerKey string) (netip.Addr, error) {
 	peerAllowedIP, exists := d.peerStore.AllowedIP(peerKey)
 	if !exists {