add HOST1 helper

README.md

@@ -46,11 +46,11 @@ func (h *DNSHandler) ServeDNS(rw fastdns.ResponseWriter, req *fastdns.Message) {
 
 	switch req.Question.Type {
 	case fastdns.TypeA:
-		fastdns.HOST(rw, req, 60, []netip.Addr{netip.AddrFrom4([4]byte{8, 8, 8, 8})})
+		fastdns.HOST1(rw, req, 60, netip.AddrFrom4([4]byte{8, 8, 8, 8}))
 	case fastdns.TypeAAAA:
 		fastdns.HOST(rw, req, 60, []netip.Addr{netip.MustParseAddr("2001:4860:4860::8888")})
 	case fastdns.TypeCNAME:
-		fastdns.CNAME(rw, req, 60, []string{"dns.google"}, []netip.Addr{netip.AddrFrom4([4]byte{8, 8, 4, 4})})
+		fastdns.CNAME(rw, req, 60, []string{"dns.google"}, []netip.Addr{netip.MustParseAddr("8.8.8.8")})
 	case fastdns.TypeSRV:
 		fastdns.SRV(rw, req, 60, []net.SRV{{"www.google.com", 443, 1000, 1000}})
 	case fastdns.TypeNS:

handler.go

@@ -16,6 +16,13 @@ func Error(rw ResponseWriter, req *Message, rcode Rcode) {
 	_, _ = rw.Write(req.Raw)
 }
 
+// HOST1 replies to the request with the specified Host record.
+func HOST1(rw ResponseWriter, req *Message, ttl uint32, ip netip.Addr) {
+	req.SetResponseHeader(RcodeNoError, 1)
+	req.Raw = AppendHOST1Record(req.Raw, req, ttl, ip)
+	_, _ = rw.Write(req.Raw)
+}
+
 // HOST replies to the request with the specified Host records.
 func HOST(rw ResponseWriter, req *Message, ttl uint32, ips []netip.Addr) {
 	req.SetResponseHeader(RcodeNoError, uint16(len(ips)))

handler_test.go

@@ -47,6 +47,28 @@ func TestHandlerError(t *testing.T) {
 	}
 }
 
+func TestHandlerHost1(t *testing.T) {
+	var cases = []struct {
+		Hex string
+		IP  netip.Addr
+		TTL uint32
+	}{
+		{
+			"00028180000100010000000002686b0470687573026c750000010001c00c000100010000012c000401020408",
+			netip.AddrFrom4([4]byte{1, 2, 4, 8}),
+			300,
+		},
+	}
+
+	rw, req := &MemResponseWriter{}, mockMessage()
+	for _, c := range cases {
+		HOST1(rw, req, c.TTL, c.IP)
+		if got, want := hex.EncodeToString(rw.Data), c.Hex; got != want {
+			t.Errorf("HOST1(%v) error got=%#v want=%#v", c.IP, got, want)
+		}
+	}
+}
+
 func TestHandlerHost(t *testing.T) {
 	var cases = []struct {
 		Hex string
@@ -243,6 +265,14 @@ func (rw *nilResponseWriter) LocalAddr() netip.AddrPort { return netip.AddrPort{
 
 func (rw *nilResponseWriter) Write(p []byte) (n int, err error) { return len(p), nil }
 
+func BenchmarkHOST1(b *testing.B) {
+	req := mockMessage()
+	ip := netip.AddrFrom4([4]byte{8, 8, 8, 8})
+	for i := 0; i < b.N; i++ {
+		HOST1(&nilResponseWriter{}, req, 3000, ip)
+	}
+}
+
 func BenchmarkHOST(b *testing.B) {
 	req := mockMessage()
 	ips := []netip.Addr{netip.AddrFrom4([4]byte{8, 8, 8, 8})}

record_be.go

@@ -53,6 +53,49 @@ func AppendHOSTRecord(dst []byte, req *Message, ttl uint32, ips []netip.Addr) []
 	return dst
 }
 
+// AppendHOST1Record appends a Host record to dst and returns the resulting dst.
+func AppendHOST1Record(dst []byte, req *Message, ttl uint32, ip netip.Addr) []byte {
+	b := (*[16]byte)(unsafe.Pointer(&ip))
+	if ip.Is4() {
+		answer := [...]byte{
+			// NAME
+			0xc0, 0x0c,
+			// TYPE
+			0x00, byte(TypeA),
+			// CLASS
+			byte(req.Question.Class >> 8), byte(req.Question.Class),
+			// TTL
+			byte(ttl >> 24), byte(ttl >> 16), byte(ttl >> 8), byte(ttl),
+			// RDLENGTH
+			0x00, 0x04,
+			// RDATA
+			b[8], b[9], b[10], b[11],
+		}
+		dst = append(dst, answer[:]...)
+	} else {
+		answer := [...]byte{
+			// NAME
+			0xc0, 0x0c,
+			// TYPE
+			0x00, byte(TypeAAAA),
+			// CLASS
+			byte(req.Question.Class >> 8), byte(req.Question.Class),
+			// TTL
+			byte(ttl >> 24), byte(ttl >> 16), byte(ttl >> 8), byte(ttl),
+			// RDLENGTH
+			0x00, 0x10,
+			// RDATA
+			b[8], b[9], b[10], b[11],
+			b[12], b[13], b[14], b[15],
+			b[0], b[1], b[2], b[3],
+			b[4], b[5], b[6], b[7],
+		}
+		dst = append(dst, answer[:]...)
+	}
+
+	return dst
+}
+
 // AppendCNAMERecord appends the CNAME and Host records to dst and returns the resulting dst.
 func AppendCNAMERecord(dst []byte, req *Message, ttl uint32, cnames []string, ips []netip.Addr) []byte {
 	offset := 0x0c

record_le.go

@@ -8,6 +8,49 @@ import (
 	"unsafe"
 )
 
+// AppendHOST1Record appends a Host records to dst and returns the resulting dst.
+func AppendHOST1Record(dst []byte, req *Message, ttl uint32, ip netip.Addr) []byte {
+	b := (*[16]byte)(unsafe.Pointer(&ip))
+	if ip.Is4() {
+		answer := [...]byte{
+			// NAME
+			0xc0, 0x0c,
+			// TYPE
+			0x00, byte(TypeA),
+			// CLASS
+			byte(req.Question.Class >> 8), byte(req.Question.Class),
+			// TTL
+			byte(ttl >> 24), byte(ttl >> 16), byte(ttl >> 8), byte(ttl),
+			// RDLENGTH
+			0x00, 0x04,
+			// RDATA
+			b[11], b[10], b[9], b[8],
+		}
+		dst = append(dst, answer[:]...)
+	} else {
+		answer := [...]byte{
+			// NAME
+			0xc0, 0x0c,
+			// TYPE
+			0x00, byte(TypeAAAA),
+			// CLASS
+			byte(req.Question.Class >> 8), byte(req.Question.Class),
+			// TTL
+			byte(ttl >> 24), byte(ttl >> 16), byte(ttl >> 8), byte(ttl),
+			// RDLENGTH
+			0x00, 0x10,
+			// RDATA
+			b[7], b[6], b[5], b[4],
+			b[3], b[2], b[1], b[0],
+			b[15], b[14], b[13], b[12],
+			b[11], b[10], b[9], b[8],
+		}
+		dst = append(dst, answer[:]...)
+	}
+
+	return dst
+}
+
 // AppendHOSTRecord appends the Host records to dst and returns the resulting dst.
 func AppendHOSTRecord(dst []byte, req *Message, ttl uint32, ips []netip.Addr) []byte {
 	for _, ip := range ips {