lnwire: Add upfront shutdown messages and feature bit

This commit adds the feature bit and additional fields
required in `open_channel` and `accept_channel` wire
messages for `option_upfront_shutdown_script`.

lnwire/lnwire_test.go

@@ -67,6 +67,15 @@ func randRawKey() ([33]byte, error) {
 	return n, nil
 }
 
+func randDeliveryAddress(r *rand.Rand) (DeliveryAddress, error) {
+	// Generate size minimum one. Empty scripts should be tested specifically.
+	size := r.Intn(deliveryAddressMaxSize) + 1
+	da := DeliveryAddress(make([]byte, size))
+
+	_, err := r.Read(da)
+	return da, err
+}
+
 func randRawFeatureVector(r *rand.Rand) *RawFeatureVector {
 	featureVec := NewRawFeatureVector()
 	for i := 0; i < 10000; i++ {
@@ -241,6 +250,9 @@ func TestEmptyMessageUnknownType(t *testing.T) {
 // TestLightningWireProtocol uses the testing/quick package to create a series
 // of fuzz tests to attempt to break a primary scenario which is implemented as
 // property based testing scenario.
+//
+// Debug help: when the message payload can reach a size larger than the return
+// value of MaxPayloadLength, the test can panic without a helpful message.
 func TestLightningWireProtocol(t *testing.T) {
 	t.Parallel()
 
@@ -353,6 +365,17 @@ func TestLightningWireProtocol(t *testing.T) {
 				return
 			}
 
+			// 1/2 chance empty upfront shutdown script.
+			if r.Intn(2) == 0 {
+				req.UpfrontShutdownScript, err = randDeliveryAddress(r)
+				if err != nil {
+					t.Fatalf("unable to generate delivery address: %v", err)
+					return
+				}
+			} else {
+				req.UpfrontShutdownScript = []byte{}
+			}
+
 			v[0] = reflect.ValueOf(req)
 		},
 		MsgAcceptChannel: func(v []reflect.Value, r *rand.Rand) {
@@ -403,6 +426,17 @@ func TestLightningWireProtocol(t *testing.T) {
 				return
 			}
 
+			// 1/2 chance empty upfront shutdown script.
+			if r.Intn(2) == 0 {
+				req.UpfrontShutdownScript, err = randDeliveryAddress(r)
+				if err != nil {
+					t.Fatalf("unable to generate delivery address: %v", err)
+					return
+				}
+			} else {
+				req.UpfrontShutdownScript = []byte{}
+			}
+
 			v[0] = reflect.ValueOf(req)
 		},
 		MsgFundingCreated: func(v []reflect.Value, r *rand.Rand) {