*: support extra dBFT stage

Ref. #112.

Signed-off-by: Anna Shaleva <[email protected]>

check.go

@@ -57,6 +57,66 @@ func (d *DBFT[H]) checkCommit() {
 		return
 	}
 
+	if d.isAntiMEVExtensionEnabled() {
+		d.preBlock = d.CreatePreBlock()
+		hash := d.preBlock.Hash()
+
+		d.Logger.Info("processing PreBlock",
+			zap.Uint32("height", d.BlockIndex),
+			zap.Stringer("preBlock hash", hash),
+			zap.Int("tx_count", len(d.preBlock.Transactions())))
+
+		d.preBlockProcessed = true
+		d.ProcessPreBlock(d.preBlock)
+
+		if d.CommitSent() { // TODO: Do we really need to require Commit sent by *self* or M other's Commits is enough to sent CommitAck? It depends on the keys sharing logic
+			d.sendCommitAck()
+			d.changeTimer(d.SecondsPerBlock)
+			d.checkCommitAck()
+		} else {
+			d.Logger.Debug("can't send commitAck since self commit not yet sent")
+		}
+		return
+	}
+
+	d.lastBlockIndex = d.BlockIndex
+	d.lastBlockTime = d.Timer.Now()
+	d.block = d.CreateBlock()
+	hash := d.block.Hash()
+
+	d.Logger.Info("approving block",
+		zap.Uint32("height", d.BlockIndex),
+		zap.Stringer("hash", hash),
+		zap.Int("tx_count", len(d.block.Transactions())),
+		zap.Stringer("merkle", d.block.MerkleRoot()),
+		zap.Stringer("prev", d.block.PrevHash()))
+
+	d.blockProcessed = true
+	d.ProcessBlock(d.block)
+
+	// Do not initialize consensus process immediately. It's the caller's duty to
+	// start the new block acceptance process and call Reset at the
+	// new height.
+}
+
+func (d *DBFT[H]) checkCommitAck() {
+	if !d.hasAllTransactions() {
+		d.Logger.Debug("check commit: some transactions are missing", zap.Any("hashes", d.MissingTransactions))
+		return
+	}
+
+	count := 0
+	for _, msg := range d.CommitAckPayloads {
+		if msg != nil && msg.ViewNumber() == d.ViewNumber {
+			count++
+		}
+	}
+
+	if count < d.M() {
+		d.Logger.Debug("not enough to commit", zap.Int("count", count))
+		return
+	}
+
 	d.lastBlockIndex = d.BlockIndex
 	d.lastBlockTime = d.Timer.Now()
 	d.block = d.CreateBlock()

commit_ack.go

@@ -0,0 +1,8 @@
+package dbft
+
+// CommitAck is an interface for dBFT CommitAck message.
+type CommitAck interface {
+	// Data returns commitAck's data that should be used for the final
+	// block construction.
+	Data() []byte
+}

config.go

@@ -20,9 +20,15 @@ type Config[H Hash] struct {
 	// if current time is less than that of previous context.
 	// By default use millisecond precision.
 	TimestampIncrement uint64
+	// AntiMEVExtensionEnabled denotes the height starting from which dBFT
+	// Anti-MEV extensions should be enabled. -1 means no extensions are
+	// enabled.
+	AntiMEVExtensionEnabled int64
 	// GetKeyPair returns an index of the node in the list of validators
 	// together with it's key pair.
 	GetKeyPair func([]PublicKey) (int, PrivateKey, PublicKey)
+	// NewPreBlockFromContext should allocate, fill from Context and return new block.PreBlock.
+	NewPreBlockFromContext func(ctx *Context[H]) PreBlock[H]
 	// NewBlockFromContext should allocate, fill from Context and return new block.Block.
 	NewBlockFromContext func(ctx *Context[H]) Block[H]
 	// RequestTx is a callback which is called when transaction contained
@@ -40,6 +46,8 @@ type Config[H Hash] struct {
 	VerifyBlock func(b Block[H]) bool
 	// Broadcast should broadcast payload m to the consensus nodes.
 	Broadcast func(m ConsensusPayload[H])
+	// ProcessBlock is called every time new preBlock is accepted.
+	ProcessPreBlock func(b PreBlock[H])
 	// ProcessBlock is called every time new block is accepted.
 	ProcessBlock func(b Block[H])
 	// GetBlock should return block with hash.
@@ -65,6 +73,8 @@ type Config[H Hash] struct {
 	NewChangeView func(newViewNumber byte, reason ChangeViewReason, timestamp uint64) ChangeView
 	// NewCommit is a constructor for payload.Commit.
 	NewCommit func(signature []byte) Commit
+	// NewCommitAck is a constructor for payload.CommitAck.
+	NewCommitAck func(signature []byte) CommitAck
 	// NewRecoveryRequest is a constructor for payload.RecoveryRequest.
 	NewRecoveryRequest func(ts uint64) RecoveryRequest
 	// NewRecoveryMessage is a constructor for payload.RecoveryMessage.
@@ -171,6 +181,14 @@ func WithTimestampIncrement[H Hash](u uint64) func(config *Config[H]) {
 	}
 }
 
+// WithNewPreBlockFromContext sets NewPreBlockFromContext.
+// TODO: config validation depending on extension.
+func WithNewPreBlockFromContext[H Hash](f func(ctx *Context[H]) PreBlock[H]) func(config *Config[H]) {
+	return func(cfg *Config[H]) {
+		cfg.NewPreBlockFromContext = f
+	}
+}
+
 // WithNewBlockFromContext sets NewBlockFromContext.
 func WithNewBlockFromContext[H Hash](f func(ctx *Context[H]) Block[H]) func(config *Config[H]) {
 	return func(cfg *Config[H]) {
@@ -227,6 +245,13 @@ func WithProcessBlock[H Hash](f func(b Block[H])) func(config *Config[H]) {
 	}
 }
 
+// WithProcessPreBlock sets ProcessPreBlock.
+func WithProcessPreBlock[H Hash](f func(b PreBlock[H])) func(config *Config[H]) {
+	return func(cfg *Config[H]) {
+		cfg.ProcessPreBlock = f
+	}
+}
+
 // WithGetBlock sets GetBlock.
 func WithGetBlock[H Hash](f func(h H) Block[H]) func(config *Config[H]) {
 	return func(cfg *Config[H]) {

consensus_message.go

@@ -17,6 +17,8 @@ type ConsensusMessage[H Hash] interface {
 	GetPrepareResponse() PrepareResponse[H]
 	// GetCommit returns payload as if it was Commit.
 	GetCommit() Commit
+	// GetCommitAck returns payload as if it was CommitAck.
+	GetCommitAck() CommitAck
 	// GetRecoveryRequest returns payload as if it was RecoveryRequest.
 	GetRecoveryRequest() RecoveryRequest
 	// GetRecoveryMessage returns payload as if it was RecoveryMessage.

consensus_message_type.go

@@ -11,6 +11,7 @@ const (
 	PrepareRequestType  MessageType = 0x20
 	PrepareResponseType MessageType = 0x21
 	CommitType          MessageType = 0x30
+	CommitAckType       MessageType = 0x31
 	RecoveryRequestType MessageType = 0x40
 	RecoveryMessageType MessageType = 0x41
 )
@@ -26,6 +27,8 @@ func (m MessageType) String() string {
 		return "PrepareResponse"
 	case CommitType:
 		return "Commit"
+	case CommitAckType:
+		return "CommitAck"
 	case RecoveryRequestType:
 		return "RecoveryRequest"
 	case RecoveryMessageType:

context.go

@@ -23,13 +23,17 @@ type Context[H Hash] struct {
 	// Pub is node's public key.
 	Pub PublicKey
 
-	block  Block[H]
-	header Block[H]
+	preBlock  PreBlock[H]
+	preHeader PreBlock[H]
+	block     Block[H]
+	header    Block[H]
 	// blockProcessed denotes whether Config.ProcessBlock callback was called for the current
 	// height. If so, then no second call must happen. After new block is received by the user,
 	// dBFT stops any new transaction or messages processing as far as timeouts handling till
 	// the next call to Reset.
 	blockProcessed bool
+	// TODO: add a comment, t has another meaning than blockProcessed.
+	preBlockProcessed bool
 
 	// BlockIndex is current block index.
 	BlockIndex uint32
@@ -65,6 +69,15 @@ type Context[H Hash] struct {
 	// current round, so it's possible to verify Commit against it) or stored till
 	// the corresponding PrepareRequest receiving.
 	CommitPayloads []ConsensusPayload[H]
+	// CommitAckPayloads stores consensus CommitAck payloads sent through all epochs.
+	// It is assumed that valid CommitAck payloads can only be sent once by a single
+	// node per the whole set of consensus epochs for particular block. Invalid
+	// CommitAck payloads are kicked off this list immediately (if Commit
+	// [TODO: and PrepareRequest? How do we verify CommitAck payloads: based on
+	// Commit only or based on PrepareRequest?] was received for the current round,
+	// so it's possible to verify CommitAck against it) or stored till the
+	// corresponding Commit receiving.
+	CommitAckPayloads []ConsensusPayload[H]
 	// ChangeViewPayloads stores consensus ChangeView payloads for the current epoch.
 	ChangeViewPayloads []ConsensusPayload[H]
 	// LastChangeViewPayloads stores consensus ChangeView payloads for the last epoch.
@@ -149,6 +162,12 @@ func (c *Context[H]) CommitSent() bool {
 	return !c.WatchOnly() && c.CommitPayloads[c.MyIndex] != nil
 }
 
+// CommitAckSent returns true iff CommitAck message was sent for the current epoch
+// assuming that the node can't go further than current epoch after commit was sent.
+func (c *Context[H]) CommitAckSent() bool {
+	return !c.WatchOnly() && c.CommitAckPayloads[c.MyIndex] != nil
+}
+
 // BlockSent returns true iff block was formed AND sent for the current height.
 // Once block is sent, the consensus stops new transactions and messages processing
 // as far as timeouts handling.
@@ -227,6 +246,7 @@ func (c *Context[H]) reset(view byte, ts uint64) {
 	c.ChangeViewPayloads = make([]ConsensusPayload[H], n)
 	if view == 0 {
 		c.CommitPayloads = make([]ConsensusPayload[H], n)
+		c.CommitAckPayloads = make([]ConsensusPayload[H], n)
 	}
 	c.PreparationPayloads = make([]ConsensusPayload[H], n)
 
@@ -285,24 +305,71 @@ func (c *Context[H]) CreateBlock() Block[H] {
 		}
 
 		c.block.SetTransactions(txx)
+
+		// TODO: do we really need this? CreateBlock will be called when all decryption data are available, thus we may
+		// add all necessary information in MakeHeader or in SetTransactions. For now, I'd skip it.
+		//if c.isAntiMEVExtensionEnabled() {
+		//	c.block.Finalize()
+		//}
 	}
 
 	return c.block
 }
 
+// CreatePreBlock returns PreBlock for the current epoch.
+func (c *Context[H]) CreatePreBlock() PreBlock[H] {
+	if c.preBlock == nil {
+		if c.preBlock = c.MakePreHeader(); c.preBlock == nil {
+			return nil
+		}
+
+		txx := make([]Transaction[H], len(c.TransactionHashes))
+
+		for i, h := range c.TransactionHashes {
+			txx[i] = c.Transactions[h]
+		}
+
+		c.preBlock.SetTransactions(txx)
+	}
+
+	return c.preBlock
+}
+
+// isAntiMEVExtensionEnabled returns whether Anti-MEV dBFT extension is enabled
+// at the currently processing block height.
+func (c *Context[H]) isAntiMEVExtensionEnabled() bool {
+	return c.Config.AntiMEVExtensionEnabled >= 0 && uint32(c.Config.AntiMEVExtensionEnabled) < c.BlockIndex
+}
+
 // MakeHeader returns half-filled block for the current epoch.
 // All hashable fields will be filled.
 func (c *Context[H]) MakeHeader() Block[H] {
 	if c.header == nil {
 		if !c.RequestSentOrReceived() {
 			return nil
 		}
+		if c.isAntiMEVExtensionEnabled() && !c.CommitAckSent() {
+			return nil
+		}
 		c.header = c.Config.NewBlockFromContext(c)
 	}
 
 	return c.header
 }
 
+// MakePreHeader returns half-filled block for the current epoch.
+// All hashable fields will be filled.
+func (c *Context[H]) MakePreHeader() PreBlock[H] {
+	if c.preHeader == nil {
+		if !c.RequestSentOrReceived() {
+			return nil
+		}
+		c.preHeader = c.Config.NewPreBlockFromContext(c)
+	}
+
+	return c.preHeader
+}
+
 // hasAllTransactions returns true iff all transactions were received
 // for the proposed block.
 func (c *Context[H]) hasAllTransactions() bool {