lnwallet: add test for state machine regression

lnwallet/channel_test.go

@@ -9521,3 +9521,125 @@ func TestChannelLocalUnsignedUpdatesFailure(t *testing.T) {
 	err = newAliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
 	require.NoError(t, err)
 }
+
+// TestChannelSignedAckRegression tests a previously-regressing state
+// transition no longer causes channel desynchronization.
+//
+// The full state transition of this test is:
+//
+// Alice                   Bob
+//        <----add-------
+//        <----sig-------
+//        -----rev------>
+//        -----sig------>
+//        <----rev-------
+//        ----settle---->
+//        -----sig------>
+//        <----rev-------
+//        <----sig-------
+//        -----add------>
+//        -----sig------>
+//        <----rev-------
+//                        *restarts*
+//        -----rev------>
+//        <----sig-------
+//
+func TestChannelSignedAckRegression(t *testing.T) {
+	t.Parallel()
+
+	// Create test channels to test out this state transition.
+	aliceChannel, bobChannel, cleanUp, err := CreateTestChannels(
+		channeldb.SingleFunderTweaklessBit,
+	)
+	require.NoError(t, err)
+	defer cleanUp()
+
+	// Create an HTLC that Bob will send to Alice.
+	htlc, preimage := createHTLC(0, lnwire.MilliSatoshi(5000000))
+
+	// <----add------
+	_, err = bobChannel.AddHTLC(htlc, nil)
+	require.NoError(t, err)
+	_, err = aliceChannel.ReceiveHTLC(htlc)
+	require.NoError(t, err)
+
+	// Force a state transition to lock in the HTLC.
+	// <----sig------
+	// -----rev----->
+	// -----sig----->
+	// <----rev------
+	err = ForceStateTransition(bobChannel, aliceChannel)
+	require.NoError(t, err)
+
+	// Alice settles the HTLC back to Bob.
+	// ----settle--->
+	err = aliceChannel.SettleHTLC(preimage, uint64(0), nil, nil, nil)
+	require.NoError(t, err)
+	err = bobChannel.ReceiveHTLCSettle(preimage, uint64(0))
+	require.NoError(t, err)
+
+	// -----sig---->
+	aliceSig, aliceHtlcSigs, _, err := aliceChannel.SignNextCommitment()
+	require.NoError(t, err)
+	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
+	require.NoError(t, err)
+
+	// <----rev-----
+	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
+	require.NoError(t, err)
+	_, _, _, _, err = aliceChannel.ReceiveRevocation(bobRevocation)
+	require.NoError(t, err)
+
+	// <----sig-----
+	bobSig, bobHtlcSigs, _, err := bobChannel.SignNextCommitment()
+	require.NoError(t, err)
+	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
+	require.NoError(t, err)
+
+	// Create an HTLC that Alice will send to Bob.
+	htlc2, _ := createHTLC(0, lnwire.MilliSatoshi(5000000))
+
+	// -----add---->
+	_, err = aliceChannel.AddHTLC(htlc2, nil)
+	require.NoError(t, err)
+	_, err = bobChannel.ReceiveHTLC(htlc2)
+	require.NoError(t, err)
+
+	// -----sig---->
+	aliceSig, aliceHtlcSigs, _, err = aliceChannel.SignNextCommitment()
+	require.NoError(t, err)
+	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
+	require.NoError(t, err)
+
+	// <----rev-----
+	bobRevocation, _, err = bobChannel.RevokeCurrentCommitment()
+	require.NoError(t, err)
+	_, _, _, _, err = aliceChannel.ReceiveRevocation(bobRevocation)
+	require.NoError(t, err)
+
+	// Restart Bob's channel state here.
+	newBobChannel, err := NewLightningChannel(
+		bobChannel.Signer, bobChannel.channelState,
+		bobChannel.sigPool,
+	)
+	require.NoError(t, err)
+
+	// -----rev---->
+	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
+	require.NoError(t, err)
+	fwdPkg, _, _, _, err := newBobChannel.ReceiveRevocation(aliceRevocation)
+	require.NoError(t, err)
+
+	// Assert that the fwdpkg is not empty.
+	require.Equal(t, len(fwdPkg.SettleFails), 1)
+
+	// Bob should no longer fail to sign this commitment due to faulty
+	// update logs.
+	// <----sig-----
+	bobSig, bobHtlcSigs, _, err = newBobChannel.SignNextCommitment()
+	require.NoError(t, err)
+
+	// Alice should receive the new commitment without hiccups.
+	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
+	require.NoError(t, err)
+}