lnwire: add encoding/decoding for DNS addr

Co-authored-by: Elle Mouton <elle.mouton@gmail.com>

lnwire/lnwire.go

@@ -44,6 +44,10 @@ const (
 	// v3OnionAddrLen is the length of a version 3 Tor onion service address
 	// (35 bytes decoded onion + 2 bytes port).
 	v3OnionAddrLen = 37
+
+	// dnsAddrOverhead is the fixed overhead for a DNS address: 1 byte for
+	// the hostname length and 2 bytes for the port.
+	dnsAddrOverhead = 3
 )
 
 // PkScript is simple type definition which represents a raw serialized public
@@ -70,6 +74,9 @@ const (
 
 	// v3OnionAddr denotes a version 3 Tor (prop224) onion service address.
 	v3OnionAddr addressType = 4
+
+	// dnsAddr denotes a DNS address.
+	dnsAddr addressType = 5
 )
 
 // WriteElement is a one-stop shop to write the big endian representation of
@@ -347,6 +354,11 @@ func WriteElement(w *bytes.Buffer, element interface{}) error {
 			return err
 		}
 
+	case *DNSAddress:
+		if err := WriteDNSAddress(w, e); err != nil {
+			return err
+		}
+
 	case *OpaqueAddrs:
 		if err := WriteOpaqueAddrs(w, e); err != nil {
 			return err
@@ -820,6 +832,34 @@ func ReadElement(r io.Reader, element interface{}) error {
 				}
 				addrBytesRead += v3OnionAddrLen
 
+			case dnsAddr:
+				var hostnameLen [1]byte
+				_, err := io.ReadFull(addrBuf, hostnameLen[:])
+				if err != nil {
+					return err
+				}
+
+				hostname := make([]byte, hostnameLen[0])
+				_, err = io.ReadFull(addrBuf, hostname)
+				if err != nil {
+					return err
+				}
+
+				var port [2]byte
+				_, err = io.ReadFull(addrBuf, port[:])
+				if err != nil {
+					return err
+				}
+
+				address = &DNSAddress{
+					Hostname: string(hostname),
+					Port: binary.BigEndian.Uint16(
+						port[:],
+					),
+				}
+				addrBytesRead += dnsAddrOverhead +
+					uint16(len(hostname))
+
 			default:
 				// If we don't understand this address type,
 				// we just store it along with the remaining

lnwire/message_test.go

@@ -1000,13 +1000,32 @@ func randV3OnionAddr(t testing.TB, r *rand.Rand) *tor.OnionAddr {
 	return &tor.OnionAddr{OnionService: onionService, Port: addrPort}
 }
 
+// randDNSAddr generates a random DNS address for testing purposes.
+func randDNSAddr(t testing.TB, r *rand.Rand) *lnwire.DNSAddress {
+	t.Helper()
+
+	var domain [1]byte
+	_, err := r.Read(domain[:])
+	require.NoError(t, err)
+
+	var port [2]byte
+	_, err = r.Read(port[:])
+	require.NoError(t, err, "unable to read port")
+
+	return &lnwire.DNSAddress{
+		Hostname: string(domain[:]),
+		Port:     uint16(port[0]),
+	}
+}
+
 func randAddrs(t testing.TB, r *rand.Rand) []net.Addr {
 	tcp4Addr := randTCP4Addr(t, r)
 	tcp6Addr := randTCP6Addr(t, r)
 	v2OnionAddr := randV2OnionAddr(t, r)
 	v3OnionAddr := randV3OnionAddr(t, r)
+	dnsAddr := randDNSAddr(t, r)
 
-	return []net.Addr{tcp4Addr, tcp6Addr, v2OnionAddr, v3OnionAddr}
+	return []net.Addr{tcp4Addr, tcp6Addr, v2OnionAddr, v3OnionAddr, dnsAddr}
 }
 
 func randAlias(r *rand.Rand) lnwire.NodeAlias {

lnwire/writer.go

@@ -35,6 +35,9 @@ var (
 	// ErrNilOpaqueAddrs is returned when the supplied address is nil.
 	ErrNilOpaqueAddrs = errors.New("cannot write nil OpaqueAddrs")
 
+	// ErrNilDNSAddress is returned when the supplied address is nil.
+	ErrNilDNSAddress = errors.New("cannot write nil DNS address")
+
 	// ErrNilPublicKey is returned when a nil pubkey is used.
 	ErrNilPublicKey = errors.New("cannot write nil pubkey")
 
@@ -364,6 +367,28 @@ func WriteOnionAddr(buf *bytes.Buffer, addr *tor.OnionAddr) error {
 	return WriteUint16(buf, uint16(addr.Port))
 }
 
+// WriteDNSAddress appends the DNS address to the provided buffer.
+func WriteDNSAddress(buf *bytes.Buffer, addr *DNSAddress) error {
+	if addr == nil {
+		return ErrNilDNSAddress
+	}
+
+	// Write the descriptor, the hostname length, and the hostname.
+	if _, err := buf.Write([]byte{byte(dnsAddr)}); err != nil {
+		return err
+	}
+
+	if err := WriteUint8(buf, uint8(len(addr.Hostname))); err != nil {
+		return err
+	}
+
+	if _, err := buf.WriteString(addr.Hostname); err != nil {
+		return err
+	}
+
+	return WriteUint16(buf, addr.Port)
+}
+
 // WriteOpaqueAddrs appends the payload of the given OpaqueAddrs to buffer.
 func WriteOpaqueAddrs(buf *bytes.Buffer, addr *OpaqueAddrs) error {
 	if addr == nil {
@@ -397,6 +422,10 @@ func WriteNetAddrs(buf *bytes.Buffer, addresses []net.Addr) error {
 			if err := WriteOpaqueAddrs(addrBuf, a); err != nil {
 				return err
 			}
+		case *DNSAddress:
+			if err := WriteDNSAddress(addrBuf, a); err != nil {
+				return err
+			}
 		default:
 			return ErrNilNetAddress
 		}

lnwire/writer_test.go

@@ -559,7 +559,8 @@ func TestWriteOnionAddr(t *testing.T) {
 }
 
 func TestWriteNetAddrs(t *testing.T) {
-	buf := new(bytes.Buffer)
+	t.Parallel()
+
 	tcpAddr := &net.TCPAddr{
 		IP:   net.IP{127, 0, 0, 1},
 		Port: 8080,
@@ -568,6 +569,10 @@ func TestWriteNetAddrs(t *testing.T) {
 		OnionService: "abcdefghijklmnop.onion",
 		Port:         9065,
 	}
+	dnsAddr := &DNSAddress{
+		Hostname: "example.com",
+		Port:     8080,
+	}
 
 	testCases := []struct {
 		name string
@@ -587,24 +592,27 @@ func TestWriteNetAddrs(t *testing.T) {
 		{
 			// Check empty address slice.
 			name:        "empty address slice",
-			addr:        []net.Addr{},
 			expectedErr: nil,
 			// Use two bytes to encode the address size.
 			expectedBytes: []byte{0, 0},
 		},
 		{
 			// Check a successful writes of a slice of addresses.
-			name:        "two addresses",
+			name:        "multiple addresses",
-			addr:        []net.Addr{tcpAddr, onionAddr},
+			addr:        []net.Addr{tcpAddr, onionAddr, dnsAddr},
 			expectedErr: nil,
 			expectedBytes: []byte{
-				// 7 bytes for TCP and 13 bytes for onion.
+				// 7 bytes for TCP and 13 bytes for onion,
-				0x0, 0x14,
+				// 15 bytes for DNS.
+				0x0, 0x23,
 				// TCP address.
 				0x1, 0x7f, 0x0, 0x0, 0x1, 0x1f, 0x90,
 				// Onion address.
 				0x3, 0x0, 0x44, 0x32, 0x14, 0xc7, 0x42,
 				0x54, 0xb6, 0x35, 0xcf, 0x23, 0x69,
+				// DNS address.
+				0x5, 0xb, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c,
+				0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x1f, 0x90,
 			},
 		},
 	}
@@ -612,13 +620,25 @@ func TestWriteNetAddrs(t *testing.T) {
 	for _, tc := range testCases {
 		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
-			oldLen := buf.Len()
+			buf := new(bytes.Buffer)
 
 			err := WriteNetAddrs(buf, tc.addr)
 			require.Equal(t, tc.expectedErr, err)
 
-			bytesWritten := buf.Bytes()[oldLen:buf.Len()]
+			bytesWritten := buf.Bytes()[:buf.Len()]
 			require.Equal(t, tc.expectedBytes, bytesWritten)
+
+			if tc.expectedErr != nil {
+				return
+			}
+
+			// Read the addresses from the buffer and ensure
+			// they match the original addresses.
+			var addrs []net.Addr
+			err = ReadElement(buf, &addrs)
+			require.NoError(t, err)
+
+			require.Equal(t, tc.addr, addrs)
 		})
 	}
 }