From 6a866890a8a6474a6e68a94a25bcc0eefeb1411a Mon Sep 17 00:00:00 2001
From: Joost Jager <joost.jager@gmail.com>
Date: Mon, 23 Dec 2019 12:45:41 +0100
Subject: [PATCH] lnwallet/test: test remote update after restart

This test asserts that remote updates that are locked-in on the local
commitment, but haven't been signed for on the remote commitment, are
properly restored after a restart.
---
 lnwallet/channel_test.go | 108 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/lnwallet/channel_test.go b/lnwallet/channel_test.go
index bddb3cdaf..94b9d63c7 100644
--- a/lnwallet/channel_test.go
+++ b/lnwallet/channel_test.go
@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -3050,6 +3051,113 @@ func TestChanSyncOweCommitment(t *testing.T) {
 	}
 }
 
+// TestChanSyncOweCommitmentPendingRemote asserts that local updates are applied
+// to the remote commit across restarts.
+func TestChanSyncOweCommitmentPendingRemote(t *testing.T) {
+	t.Parallel()
+
+	// Create a test channel which will be used for the duration of this
+	// unittest.
+	aliceChannel, bobChannel, cleanUp, err := CreateTestChannels(true)
+	if err != nil {
+		t.Fatalf("unable to create test channels: %v", err)
+	}
+	defer cleanUp()
+
+	var fakeOnionBlob [lnwire.OnionPacketSize]byte
+	copy(fakeOnionBlob[:], bytes.Repeat([]byte{0x05}, lnwire.OnionPacketSize))
+
+	// We'll start off the scenario where Bob send two htlcs to Alice in a
+	// single state update.
+	var preimages []lntypes.Preimage
+	const numHtlcs = 2
+	for id := byte(0); id < numHtlcs; id++ {
+		htlcAmt := lnwire.NewMSatFromSatoshis(20000)
+		var bobPreimage [32]byte
+		copy(bobPreimage[:], bytes.Repeat([]byte{id}, 32))
+		rHash := sha256.Sum256(bobPreimage[:])
+		h := &lnwire.UpdateAddHTLC{
+			PaymentHash: rHash,
+			Amount:      htlcAmt,
+			Expiry:      uint32(10),
+			OnionBlob:   fakeOnionBlob,
+		}
+
+		htlcIndex, err := bobChannel.AddHTLC(h, nil)
+		if err != nil {
+			t.Fatalf("unable to add bob's htlc: %v", err)
+		}
+
+		h.ID = htlcIndex
+		if _, err := aliceChannel.ReceiveHTLC(h); err != nil {
+			t.Fatalf("unable to recv bob's htlc: %v", err)
+		}
+
+		preimages = append(preimages, bobPreimage)
+	}
+
+	// With the HTLCs applied to both update logs, we'll initiate a state
+	// transition from Bob.
+	if err := ForceStateTransition(bobChannel, aliceChannel); err != nil {
+		t.Fatalf("unable to complete bob's state transition: %v", err)
+	}
+
+	// Next, Alice settles the HTLCs from Bob in distinct state updates.
+	for i := 0; i < numHtlcs; i++ {
+		err = aliceChannel.SettleHTLC(preimages[i], uint64(i), nil, nil, nil)
+		if err != nil {
+			t.Fatalf("unable to settle htlc: %v", err)
+		}
+		err = bobChannel.ReceiveHTLCSettle(preimages[i], uint64(i))
+		if err != nil {
+			t.Fatalf("unable to settle htlc: %v", err)
+		}
+
+		aliceSig, aliceHtlcSigs, _, err := aliceChannel.SignNextCommitment()
+		if err != nil {
+			t.Fatalf("unable to sign commitment: %v", err)
+		}
+
+		err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
+		if err != nil {
+			t.Fatalf("unable to receive commitment: %v", err)
+		}
+
+		// Bob revokes his current commitment. After this call
+		// completes, the htlc is settled on the local commitment
+		// transaction. Bob still owes Alice a signature to also settle
+		// the htlc on her local commitment transaction.
+		bobRevoke, _, err := bobChannel.RevokeCurrentCommitment()
+		if err != nil {
+			t.Fatalf("unable to revoke commitment: %v", err)
+		}
+
+		_, _, _, _, err = aliceChannel.ReceiveRevocation(bobRevoke)
+		if err != nil {
+			t.Fatalf("unable to revoke commitment: %v", err)
+		}
+	}
+
+	// We restart Bob. This should have no impact on further message that
+	// are generated.
+	bobChannel, err = restartChannel(bobChannel)
+	if err != nil {
+		t.Fatalf("unable to restart bob: %v", err)
+	}
+
+	// Bob signs the commitment he owes.
+	_, bobHtlcSigs, _, err := bobChannel.SignNextCommitment()
+	if err != nil {
+		t.Fatalf("unable to sign commitment: %v", err)
+	}
+
+	// This commitment is expected to contain no htlcs anymore, but because
+	// of a bug it is still present. THIS IS NOT CORRECT!
+	if len(bobHtlcSigs) != 2 {
+		t.Fatal("expected htlc to still be pending")
+	}
+}
+
 // TestChanSyncOweRevocation tests that if Bob restarts (and then Alice) before
 // he receiver's Alice's RevokeAndAck message, then Alice concludes that she
 // needs to re-send the RevokeAndAck. After the revocation has been sent, both