htlcswitch/hop: make unknown required type const

Currently we use the AMP record type, this allows us to change it easily
as we add new known records. We also bump this to 0x0c instead of 0x0a.

htlcswitch/hop/payload_test.go

@@ -10,6 +10,8 @@ import (
 	"github.com/lightningnetwork/lnd/record"
 )
 
+const testUnknownRequiredType = 0x10
+
 type decodePayloadTest struct {
 	name             string
 	payload          []byte
@@ -81,21 +83,26 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:    "required type after omitted hop id",
-		payload: []byte{0x02, 0x00, 0x04, 0x00, 0x0a, 0x00},
+		name: "required type after omitted hop id",
+		payload: []byte{
+			0x02, 0x00, 0x04, 0x00,
+			testUnknownRequiredType, 0x00,
+		},
 		expErr: hop.ErrInvalidPayload{
-			Type:      10,
+			Type:      testUnknownRequiredType,
 			Violation: hop.RequiredViolation,
 			FinalHop:  true,
 		},
 	},
 	{
 		name: "required type after included hop id",
-		payload: []byte{0x02, 0x00, 0x04, 0x00, 0x06, 0x08, 0x01, 0x00,
-			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x00,
+		payload: []byte{
+			0x02, 0x00, 0x04, 0x00, 0x06, 0x08, 0x01, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00,
+			testUnknownRequiredType, 0x00,
 		},
 		expErr: hop.ErrInvalidPayload{
-			Type:      10,
+			Type:      testUnknownRequiredType,
 			Violation: hop.RequiredViolation,
 			FinalHop:  false,
 		},