htlcswitch/hop/payload: required failures with ErrInvalidPayload

This commit adds a hop.PayloadViolation enum which encompasses the cases
where the sender omits, includes, or requires a type that causes an
ErrInvalidPayload faiulre.

The existing Omitted bool is converted to this PayloadViolation, and
NewPayloadFromReader is updated to return such a failure with a
RequiredViolation when an unknown required type is detected.

The unit tests are updated to cover the three possible cases of
RequiredViolations, as well as included valid intermediate and final hop
tests.

htlcswitch/hop/payload_test.go

@@ -16,13 +16,23 @@ type decodePayloadTest struct {
 }
 
 var decodePayloadTests = []decodePayloadTest{
+	{
+		name:    "final hop valid",
+		payload: []byte{0x02, 0x00, 0x04, 0x00},
+	},
+	{
+		name: "intermediate hop valid",
+		payload: []byte{0x02, 0x00, 0x04, 0x00, 0x06, 0x08, 0x01, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		},
+	},
 	{
 		name:    "final hop no amount",
 		payload: []byte{0x04, 0x00},
 		expErr: hop.ErrInvalidPayload{
-			Type:     record.AmtOnionType,
-			Omitted:  true,
-			FinalHop: true,
+			Type:      record.AmtOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  true,
 		},
 	},
 	{
@@ -31,18 +41,18 @@ var decodePayloadTests = []decodePayloadTest{
 			0x00, 0x00, 0x00, 0x00,
 		},
 		expErr: hop.ErrInvalidPayload{
-			Type:     record.AmtOnionType,
-			Omitted:  true,
-			FinalHop: false,
+			Type:      record.AmtOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  false,
 		},
 	},
 	{
 		name:    "final hop no expiry",
 		payload: []byte{0x02, 0x00},
 		expErr: hop.ErrInvalidPayload{
-			Type:     record.LockTimeOnionType,
-			Omitted:  true,
-			FinalHop: true,
+			Type:      record.LockTimeOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  true,
 		},
 	},
 	{
@@ -51,9 +61,9 @@ var decodePayloadTests = []decodePayloadTest{
 			0x00, 0x00, 0x00, 0x00,
 		},
 		expErr: hop.ErrInvalidPayload{
-			Type:     record.LockTimeOnionType,
-			Omitted:  true,
-			FinalHop: false,
+			Type:      record.LockTimeOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  false,
 		},
 	},
 	{
@@ -62,9 +72,38 @@ var decodePayloadTests = []decodePayloadTest{
 			0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 		},
 		expErr: hop.ErrInvalidPayload{
-			Type:     record.NextHopOnionType,
-			Omitted:  false,
-			FinalHop: true,
+			Type:      record.NextHopOnionType,
+			Violation: hop.IncludedViolation,
+			FinalHop:  true,
+		},
+	},
+	{
+		name:    "required type after omitted hop id",
+		payload: []byte{0x08, 0x00},
+		expErr: hop.ErrInvalidPayload{
+			Type:      8,
+			Violation: hop.RequiredViolation,
+			FinalHop:  true,
+		},
+	},
+	{
+		name: "required type after included hop id",
+		payload: []byte{0x06, 0x08, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x08, 0x00,
+		},
+		expErr: hop.ErrInvalidPayload{
+			Type:      8,
+			Violation: hop.RequiredViolation,
+			FinalHop:  false,
+		},
+	},
+	{
+		name:    "required type zero",
+		payload: []byte{0x00, 0x00},
+		expErr: hop.ErrInvalidPayload{
+			Type:      0,
+			Violation: hop.RequiredViolation,
+			FinalHop:  true,
 		},
 	},
 }