Repository: lightningnetwork/lnd
Pull request #3654 (2019-10-31 02:28:41)

multi: convert the existing channeldb.ChannelType uint8 into a bit field
In this commit, we convert the existing `channeldb.ChannelType` type
into a _bit field_. This doesn't require us to change the current
serialization or interpretation or the type as it is, since all the
current defined values us a distinct bit. This PR lays the ground work
for any future changes that may introduce new channel types (like anchor
outputs), and also any changes that may modify the existing invariants
around channels (if we're the initiator, we always have the funding
transaction).



guggero: Travis fails for the dual funder flow:

```
--- FAIL: TestLightningWallet (356.83s)
    --- PASS: TestLightningWallet/btcwallet/bitcoind:change_output_spend_confirmation (6.29s)
    --- PASS: TestLightningWallet/btcwallet/bitcoind:insane_fee_reject (0.01s)
    --- PASS: TestLightningWallet/btcwallet/bitcoind:single_funding_workflow (0.72s)
    --- PASS: TestLightningWallet/btcwallet/bitcoind:single_funding_workflow_tweakless (2.46s)
    --- FAIL: TestLightningWallet/btcwallet/bitcoind:dual_funder_workflow (0.33s)
        interface_test.go:489: unable to consume alice's sigs: counterparty's commitment signature is invalid
```

Patch:
diff --git a/channeldb/channel.go b/channeldb/channel.go
index 7bc9e4806..1fdd97e9d 100644
--- a/channeldb/channel.go
+++ b/channeldb/channel.go
@@ -125,39 +125,45 @@ var (
 // ChannelType is an enum-like type that describes one of several possible
 // channel types. Each open channel is associated with a particular type as the
 // channel type may determine how higher level operations are conducted such as
-// fee negotiation, channel closing, the format of HTLCs, etc.
-// TODO(roasbeef): split up per-chain?
+// fee negotiation, channel closing, the format of HTLCs, etc. Structure-wise,
+// a ChannelType is a bit field, with each bit denoting a modification from the
+// base channel type of single funder.
 type ChannelType uint8
 
 const (
 	// NOTE: iota isn't used here for this enum needs to be stable
 	// long-term as it will be persisted to the database.
 
-	// SingleFunder represents a channel wherein one party solely funds the
-	// entire capacity of the channel.
-	SingleFunder ChannelType = 0
+	// SingleFunderBit represents a channel wherein one party solely funds
+	// the entire capacity of the channel.
+	SingleFunderBit ChannelType = 0
 
-	// DualFunder represents a channel wherein both parties contribute
+	// DualFunderBit represents a channel wherein both parties contribute
 	// funds towards the total capacity of the channel. The channel may be
 	// funded symmetrically or asymmetrically.
-	DualFunder ChannelType = 1
+	DualFunderBit ChannelType = 1 << 0
 
 	// SingleFunderTweakless is similar to the basic SingleFunder channel
 	// type, but it omits the tweak for one's key in the commitment
 	// transaction of the remote party.
-	SingleFunderTweakless ChannelType = 2
+	SingleFunderTweaklessBit ChannelType = 1 << 1
 )
 
 // IsSingleFunder returns true if the channel type if one of the known single
 // funder variants.
 func (c ChannelType) IsSingleFunder() bool {
-	return c == SingleFunder || c == SingleFunderTweakless
+	return c&DualFunderBit == 0
+}
+
+// IsDualFunder returns true if the ChannelType has the DualFunderBit set.
+func (c ChannelType) IsDualFunder() bool {
+	return c&DualFunderBit == DualFunderBit
 }
 
 // IsTweakless returns true if the target channel uses a commitment that
 // doesn't tweak the key for the remote party.
 func (c ChannelType) IsTweakless() bool {
-	return c == SingleFunderTweakless
+	return c&SingleFunderTweaklessBit == SingleFunderTweaklessBit
 }
 
 // ChannelConstraints represents a set of constraints meant to allow a node to
diff --git a/chanrestore.go b/chanrestore.go
index 6196aed58..5586ab920 100644
--- a/chanrestore.go
+++ b/chanrestore.go
@@ -87,10 +87,10 @@ func (c *chanDBRestorer) openChannelShell(backup chanbackup.Single) (
 	switch backup.Version {
 
 	case chanbackup.DefaultSingleVersion:
-		chanType = channeldb.SingleFunder
+		chanType = channeldb.SingleFunderBit
 
 	case chanbackup.TweaklessCommitVersion:
-		chanType = channeldb.SingleFunderTweakless
+		chanType = channeldb.SingleFunderTweaklessBit
 
 	default:
 		return nil, fmt.Errorf("unknown Single version: %v", err)
diff --git a/fundingmanager.go b/fundingmanager.go
index c18df5ab5..4275338c8 100644
--- a/fundingmanager.go
+++ b/fundingmanager.go
@@ -521,7 +521,7 @@ func (f *fundingManager) start() error {
 			// Rebroadcast the funding transaction for any pending
 			// channel that we initiated. No error will be returned
 			// if the transaction already has been broadcasted.
-			if channel.ChanType == channeldb.SingleFunder &&
+			if channel.ChanType.IsSingleFunder() &&
 				channel.IsInitiator {
 
 				err := f.cfg.PublishTransaction(
diff --git a/htlcswitch/link.go b/htlcswitch/link.go
index c0b62633c..b2ffe87c9 100644
--- a/htlcswitch/link.go
+++ b/htlcswitch/link.go
@@ -1860,11 +1860,9 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			}
 
 			chanType := l.channel.State().ChanType
-			isTweakless := chanType == channeldb.SingleFunderTweakless
-
 			chanID := l.ChanID()
 			err = l.cfg.TowerClient.BackupState(
-				&chanID, breachInfo, isTweakless,
+				&chanID, breachInfo, chanType.IsTweakless(),
 			)
 			if err != nil {
 				l.fail(LinkFailureError{code: ErrInternalError},
diff --git a/lnwallet/channel.go b/lnwallet/channel.go
index f9d077875..b199efe53 100644
--- a/lnwallet/channel.go
+++ b/lnwallet/channel.go
@@ -868,8 +868,7 @@ func (lc *LightningChannel) diskCommitToMemCommit(isLocal bool,
 	// If this commit is tweakless, then it'll affect the way we derive our
 	// keys, which will affect the commitment transaction reconstruction.
 	// So we'll determine this first, before we do anything else.
-	tweaklessCommit := (lc.channelState.ChanType ==
-		channeldb.SingleFunderTweakless)
+	tweaklessCommit := lc.channelState.ChanType.IsTweakless()
 
 	// First, we'll need to re-derive the commitment key ring for each
 	// party used within this particular state. If this is a pending commit
diff --git a/lnwallet/reservation.go b/lnwallet/reservation.go
index b96651ff0..465a9b41f 100644
--- a/lnwallet/reservation.go
+++ b/lnwallet/reservation.go
@@ -215,15 +215,15 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	// a single-funder channel.
 	if ourBalance == 0 || theirBalance == 0 || pushMSat != 0 {
 		if tweaklessCommit {
-			chanType = channeldb.SingleFunderTweakless
+			chanType |= channeldb.SingleFunderTweaklessBit
 		} else {
-			chanType = channeldb.SingleFunder
+			chanType |= channeldb.SingleFunderBit
 		}
 	} else {
 		// Otherwise, this is a dual funder channel, and no side is
 		// technically the "initiator"
 		initiator = false
-		chanType = channeldb.DualFunder
+		chanType |= channeldb.DualFunderBit
 	}
 
 	return &ChannelReservation{


Test patch:
diff --git a/breacharbiter_test.go b/breacharbiter_test.go
index 7f471ea2e..724643aef 100644
--- a/breacharbiter_test.go
+++ b/breacharbiter_test.go
@@ -1865,7 +1865,7 @@ func createInitChannels(revocationWindow int) (*lnwallet.LightningChannel, *lnwa
 		IdentityPub:             aliceKeyPub,
 		FundingOutpoint:         *prevOut,
 		ShortChannelID:          shortChanID,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             true,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: bobCommitPoint,
@@ -1883,7 +1883,7 @@ func createInitChannels(revocationWindow int) (*lnwallet.LightningChannel, *lnwa
 		IdentityPub:             bobKeyPub,
 		FundingOutpoint:         *prevOut,
 		ShortChannelID:          shortChanID,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             false,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: aliceCommitPoint,
diff --git a/chanbackup/single_test.go b/chanbackup/single_test.go
index ba56ece76..776ce0bc8 100644
--- a/chanbackup/single_test.go
+++ b/chanbackup/single_test.go
@@ -124,9 +124,9 @@ func genRandomOpenChannelShell() (*channeldb.OpenChannel, error) {
 		isInitiator = true
 	}
 
-	chanType := channeldb.SingleFunder
+	chanType := channeldb.SingleFunderBit
 	if rand.Int63()%2 == 0 {
-		chanType = channeldb.SingleFunderTweakless
+		chanType = channeldb.SingleFunderTweaklessBit
 	}
 
 	return &channeldb.OpenChannel{
diff --git a/channeldb/channel_test.go b/channeldb/channel_test.go
index 21bb738cf..6d34c2f97 100644
--- a/channeldb/channel_test.go
+++ b/channeldb/channel_test.go
@@ -187,7 +187,7 @@ func createTestChannelState(cdb *DB) (*OpenChannel, error) {
 	chanID := lnwire.NewShortChanIDFromInt(uint64(rand.Int63()))
 
 	return &OpenChannel{
-		ChanType:          SingleFunder,
+		ChanType:          SingleFunderBit,
 		ChainHash:         key,
 		FundingOutpoint:   wire.OutPoint{Hash: key, Index: rand.Uint32()},
 		ShortChannelID:    chanID,
diff --git a/htlcswitch/test_utils.go b/htlcswitch/test_utils.go
index 3c11c3fd6..5ff595663 100644
--- a/htlcswitch/test_utils.go
+++ b/htlcswitch/test_utils.go
@@ -328,7 +328,7 @@ func createTestChannel(alicePrivKey, bobPrivKey []byte,
 		RemoteChanCfg:           bobCfg,
 		IdentityPub:             aliceKeyPub,
 		FundingOutpoint:         *prevOut,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             true,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: bobCommitPoint,
@@ -347,7 +347,7 @@ func createTestChannel(alicePrivKey, bobPrivKey []byte,
 		RemoteChanCfg:           aliceCfg,
 		IdentityPub:             bobKeyPub,
 		FundingOutpoint:         *prevOut,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             false,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: aliceCommitPoint,
diff --git a/lnwallet/interface_test.go b/lnwallet/interface_test.go
index 04af443fa..d998c0a04 100644
--- a/lnwallet/interface_test.go
+++ b/lnwallet/interface_test.go
@@ -511,7 +511,7 @@ func testDualFundingReservationWorkflow(miner *rpctest.Harness,
 	if !bytes.Equal(aliceChannels[0].FundingOutpoint.Hash[:], fundingSha[:]) {
 		t.Fatalf("channel state not properly saved")
 	}
-	if aliceChannels[0].ChanType != channeldb.DualFunder {
+	if !aliceChannels[0].ChanType.IsDualFunder() {
 		t.Fatalf("channel not detected as dual funder")
 	}
 	bobChannels, err := bob.Cfg.Database.FetchOpenChannels(alicePub)
@@ -521,7 +521,7 @@ func testDualFundingReservationWorkflow(miner *rpctest.Harness,
 	if !bytes.Equal(bobChannels[0].FundingOutpoint.Hash[:], fundingSha[:]) {
 		t.Fatalf("channel state not properly saved")
 	}
-	if bobChannels[0].ChanType != channeldb.DualFunder {
+	if !bobChannels[0].ChanType.IsDualFunder() {
 		t.Fatalf("channel not detected as dual funder")
 	}
 
@@ -971,7 +971,7 @@ func testSingleFunderReservationWorkflow(miner *rpctest.Harness,
 	}
 	if !aliceChannels[0].ChanType.IsSingleFunder() {
 		t.Fatalf("channel type is incorrect, expected %v instead got %v",
-			channeldb.SingleFunder, aliceChannels[0].ChanType)
+			channeldb.SingleFunderBit, aliceChannels[0].ChanType)
 	}
 
 	bobChannels, err := bob.Cfg.Database.FetchOpenChannels(alicePub)
@@ -991,7 +991,7 @@ func testSingleFunderReservationWorkflow(miner *rpctest.Harness,
 	}
 	if !bobChannels[0].ChanType.IsSingleFunder() {
 		t.Fatalf("channel type is incorrect, expected %v instead got %v",
-			channeldb.SingleFunder, bobChannels[0].ChanType)
+			channeldb.SingleFunderBit, bobChannels[0].ChanType)
 	}
 
 	// Let Alice publish the funding transaction.
diff --git a/lnwallet/test_utils.go b/lnwallet/test_utils.go
index efb30ac1d..324064ffb 100644
--- a/lnwallet/test_utils.go
+++ b/lnwallet/test_utils.go
@@ -274,7 +274,7 @@ func CreateTestChannels(tweaklessCommits bool) (
 		IdentityPub:             aliceKeys[0].PubKey(),
 		FundingOutpoint:         *prevOut,
 		ShortChannelID:          shortChanID,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             true,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: bobCommitPoint,
@@ -292,7 +292,7 @@ func CreateTestChannels(tweaklessCommits bool) (
 		IdentityPub:             bobKeys[0].PubKey(),
 		FundingOutpoint:         *prevOut,
 		ShortChannelID:          shortChanID,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             false,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: aliceCommitPoint,
@@ -305,8 +305,8 @@ func CreateTestChannels(tweaklessCommits bool) (
 	}
 
 	if !tweaklessCommits {
-		aliceChannelState.ChanType = channeldb.SingleFunder
-		bobChannelState.ChanType = channeldb.SingleFunder
+		aliceChannelState.ChanType = channeldb.SingleFunderBit
+		bobChannelState.ChanType = channeldb.SingleFunderBit
 	}
 
 	aliceSigner := &input.MockSigner{Privkeys: aliceKeys}
diff --git a/lnwallet/transactions_test.go b/lnwallet/transactions_test.go
index ed4c533db..9fdacc071 100644
--- a/lnwallet/transactions_test.go
+++ b/lnwallet/transactions_test.go
@@ -370,7 +370,7 @@ func TestCommitmentAndHTLCTransactions(t *testing.T) {
 
 	// Manually construct a new LightningChannel.
 	channelState := channeldb.OpenChannel{
-		ChanType:        channeldb.SingleFunderTweakless,
+		ChanType:        channeldb.SingleFunderTweaklessBit,
 		ChainHash:       *tc.netParams.GenesisHash,
 		FundingOutpoint: tc.fundingOutpoint,
 		ShortChannelID:  tc.shortChanID,
diff --git a/test_utils.go b/test_utils.go
index 671bc0f46..06f3767dd 100644
--- a/test_utils.go
+++ b/test_utils.go
@@ -255,7 +255,7 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 		IdentityPub:             aliceKeyPub,
 		FundingOutpoint:         *prevOut,
 		ShortChannelID:          shortChanID,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             true,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: bobCommitPoint,
@@ -272,7 +272,7 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 		RemoteChanCfg:           aliceCfg,
 		IdentityPub:             bobKeyPub,
 		FundingOutpoint:         *prevOut,
-		ChanType:                channeldb.SingleFunderTweakless,
+		ChanType:                channeldb.SingleFunderTweaklessBit,
 		IsInitiator:             false,
 		Capacity:                channelCapacity,
 		RemoteCurrentRevocation: aliceCommitPoint,