channeldb: fix migration bug due to interplay between migration #9 and #10

In this commit, we fix an issue that was recently introduced as a result
of migration #10. The new TLV format ended up modifying the
serialization functions called in `serializePaymentAttemptInfo`.
Migration #9, also used this `serializePaymentAttemptInfo` method to
serialize the _new_ (pre TLV, but new payment attempt structure) routes
into the database during its migration. However, migration #10 failed to
copy over the existing unmodified `serializePaymentAttemptInfo` method
into the legacy serialization for migration #9. As a result, once
migration #9 was run, the routes/payments were serialized using the
_new_ format, rather than the format used for v0.7.1. This then lead to
de-serialization either failing, or causing partial payment corruption
as migration #10 was expecting the "legacy" format (no TLV info).

We fix this issue by adding a new fully enclosed
`serializePaymentAttemptInfoMigration9`method that will be used for
migration #9. Note that our tests didn't catch this, as they test the
migration in isolation, rather than in series which is how users will
encounter the migrations.

Fixes #3463.

channeldb/migration_09_legacy_serialization.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/coreos/bbolt"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/routing/route"
 )
 
 var (
@@ -253,3 +254,50 @@ func deserializeOutgoingPayment(r io.Reader) (*outgoingPayment, error) {
 
 	return p, nil
 }
+
+// serializePaymentAttemptInfoMigration9 is the serializePaymentAttemptInfo
+// version as existed when migration #9 was created. We keep this around, along
+// with the methods below to ensure that clients that upgrade will use the
+// correct version of this method.
+func serializePaymentAttemptInfoMigration9(w io.Writer, a *PaymentAttemptInfo) error {
+	if err := WriteElements(w, a.PaymentID, a.SessionKey); err != nil {
+		return err
+	}
+
+	if err := serializeRouteMigration9(w, a.Route); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func serializeHopMigration9(w io.Writer, h *route.Hop) error {
+	if err := WriteElements(w,
+		h.PubKeyBytes[:], h.ChannelID, h.OutgoingTimeLock,
+		h.AmtToForward,
+	); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func serializeRouteMigration9(w io.Writer, r route.Route) error {
+	if err := WriteElements(w,
+		r.TotalTimeLock, r.TotalAmount, r.SourcePubKey[:],
+	); err != nil {
+		return err
+	}
+
+	if err := WriteElements(w, uint32(len(r.Hops))); err != nil {
+		return err
+	}
+
+	for _, h := range r.Hops {
+		if err := serializeHopMigration9(w, h); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

channeldb/migrations.go

@@ -845,7 +845,7 @@ func migrateOutgoingPayments(tx *bbolt.Tx) error {
 		}
 
 		var attemptBuf bytes.Buffer
-		if err := serializePaymentAttemptInfo(&attemptBuf, s); err != nil {
+		if err := serializePaymentAttemptInfoMigration9(&attemptBuf, s); err != nil {
 			return err
 		}