Release v0.1.0

vendor/github.com/btcsuite/btcd/blockchain/versionbits.go

@@ -0,0 +1,301 @@
+// Copyright (c) 2016-2017 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package blockchain
+
+import (
+	"math"
+
+	"github.com/btcsuite/btcd/chaincfg"
+)
+
+const (
+	// vbLegacyBlockVersion is the highest legacy block version before the
+	// version bits scheme became active.
+	vbLegacyBlockVersion = 4
+
+	// vbTopBits defines the bits to set in the version to signal that the
+	// version bits scheme is being used.
+	vbTopBits = 0x20000000
+
+	// vbTopMask is the bitmask to use to determine whether or not the
+	// version bits scheme is in use.
+	vbTopMask = 0xe0000000
+
+	// vbNumBits is the total number of bits available for use with the
+	// version bits scheme.
+	vbNumBits = 29
+
+	// unknownVerNumToCheck is the number of previous blocks to consider
+	// when checking for a threshold of unknown block versions for the
+	// purposes of warning the user.
+	unknownVerNumToCheck = 100
+
+	// unknownVerWarnNum is the threshold of previous blocks that have an
+	// unknown version to use for the purposes of warning the user.
+	unknownVerWarnNum = unknownVerNumToCheck / 2
+)
+
+// bitConditionChecker provides a thresholdConditionChecker which can be used to
+// test whether or not a specific bit is set when it's not supposed to be
+// according to the expected version based on the known deployments and the
+// current state of the chain.  This is useful for detecting and warning about
+// unknown rule activations.
+type bitConditionChecker struct {
+	bit   uint32
+	chain *BlockChain
+}
+
+// Ensure the bitConditionChecker type implements the thresholdConditionChecker
+// interface.
+var _ thresholdConditionChecker = bitConditionChecker{}
+
+// BeginTime returns the unix timestamp for the median block time after which
+// voting on a rule change starts (at the next window).
+//
+// Since this implementation checks for unknown rules, it returns 0 so the rule
+// is always treated as active.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c bitConditionChecker) BeginTime() uint64 {
+	return 0
+}
+
+// EndTime returns the unix timestamp for the median block time after which an
+// attempted rule change fails if it has not already been locked in or
+// activated.
+//
+// Since this implementation checks for unknown rules, it returns the maximum
+// possible timestamp so the rule is always treated as active.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c bitConditionChecker) EndTime() uint64 {
+	return math.MaxUint64
+}
+
+// RuleChangeActivationThreshold is the number of blocks for which the condition
+// must be true in order to lock in a rule change.
+//
+// This implementation returns the value defined by the chain params the checker
+// is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c bitConditionChecker) RuleChangeActivationThreshold() uint32 {
+	return c.chain.chainParams.RuleChangeActivationThreshold
+}
+
+// MinerConfirmationWindow is the number of blocks in each threshold state
+// retarget window.
+//
+// This implementation returns the value defined by the chain params the checker
+// is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c bitConditionChecker) MinerConfirmationWindow() uint32 {
+	return c.chain.chainParams.MinerConfirmationWindow
+}
+
+// Condition returns true when the specific bit associated with the checker is
+// set and it's not supposed to be according to the expected version based on
+// the known deployments and the current state of the chain.
+//
+// This function MUST be called with the chain state lock held (for writes).
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c bitConditionChecker) Condition(node *blockNode) (bool, error) {
+	conditionMask := uint32(1) << c.bit
+	version := uint32(node.version)
+	if version&vbTopMask != vbTopBits {
+		return false, nil
+	}
+	if version&conditionMask == 0 {
+		return false, nil
+	}
+
+	expectedVersion, err := c.chain.calcNextBlockVersion(node.parent)
+	if err != nil {
+		return false, err
+	}
+	return uint32(expectedVersion)&conditionMask == 0, nil
+}
+
+// deploymentChecker provides a thresholdConditionChecker which can be used to
+// test a specific deployment rule.  This is required for properly detecting
+// and activating consensus rule changes.
+type deploymentChecker struct {
+	deployment *chaincfg.ConsensusDeployment
+	chain      *BlockChain
+}
+
+// Ensure the deploymentChecker type implements the thresholdConditionChecker
+// interface.
+var _ thresholdConditionChecker = deploymentChecker{}
+
+// BeginTime returns the unix timestamp for the median block time after which
+// voting on a rule change starts (at the next window).
+//
+// This implementation returns the value defined by the specific deployment the
+// checker is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c deploymentChecker) BeginTime() uint64 {
+	return c.deployment.StartTime
+}
+
+// EndTime returns the unix timestamp for the median block time after which an
+// attempted rule change fails if it has not already been locked in or
+// activated.
+//
+// This implementation returns the value defined by the specific deployment the
+// checker is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c deploymentChecker) EndTime() uint64 {
+	return c.deployment.ExpireTime
+}
+
+// RuleChangeActivationThreshold is the number of blocks for which the condition
+// must be true in order to lock in a rule change.
+//
+// This implementation returns the value defined by the chain params the checker
+// is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c deploymentChecker) RuleChangeActivationThreshold() uint32 {
+	return c.chain.chainParams.RuleChangeActivationThreshold
+}
+
+// MinerConfirmationWindow is the number of blocks in each threshold state
+// retarget window.
+//
+// This implementation returns the value defined by the chain params the checker
+// is associated with.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c deploymentChecker) MinerConfirmationWindow() uint32 {
+	return c.chain.chainParams.MinerConfirmationWindow
+}
+
+// Condition returns true when the specific bit defined by the deployment
+// associated with the checker is set.
+//
+// This is part of the thresholdConditionChecker interface implementation.
+func (c deploymentChecker) Condition(node *blockNode) (bool, error) {
+	conditionMask := uint32(1) << c.deployment.BitNumber
+	version := uint32(node.version)
+	return (version&vbTopMask == vbTopBits) && (version&conditionMask != 0),
+		nil
+}
+
+// calcNextBlockVersion calculates the expected version of the block after the
+// passed previous block node based on the state of started and locked in
+// rule change deployments.
+//
+// This function differs from the exported CalcNextBlockVersion in that the
+// exported version uses the current best chain as the previous block node
+// while this function accepts any block node.
+//
+// This function MUST be called with the chain state lock held (for writes).
+func (b *BlockChain) calcNextBlockVersion(prevNode *blockNode) (int32, error) {
+	// Set the appropriate bits for each actively defined rule deployment
+	// that is either in the process of being voted on, or locked in for the
+	// activation at the next threshold window change.
+	expectedVersion := uint32(vbTopBits)
+	for id := 0; id < len(b.chainParams.Deployments); id++ {
+		deployment := &b.chainParams.Deployments[id]
+		cache := &b.deploymentCaches[id]
+		checker := deploymentChecker{deployment: deployment, chain: b}
+		state, err := b.thresholdState(prevNode, checker, cache)
+		if err != nil {
+			return 0, err
+		}
+		if state == ThresholdStarted || state == ThresholdLockedIn {
+			expectedVersion |= uint32(1) << deployment.BitNumber
+		}
+	}
+	return int32(expectedVersion), nil
+}
+
+// CalcNextBlockVersion calculates the expected version of the block after the
+// end of the current best chain based on the state of started and locked in
+// rule change deployments.
+//
+// This function is safe for concurrent access.
+func (b *BlockChain) CalcNextBlockVersion() (int32, error) {
+	b.chainLock.Lock()
+	version, err := b.calcNextBlockVersion(b.bestChain.Tip())
+	b.chainLock.Unlock()
+	return version, err
+}
+
+// warnUnknownRuleActivations displays a warning when any unknown new rules are
+// either about to activate or have been activated.  This will only happen once
+// when new rules have been activated and every block for those about to be
+// activated.
+//
+// This function MUST be called with the chain state lock held (for writes)
+func (b *BlockChain) warnUnknownRuleActivations(node *blockNode) error {
+	// Warn if any unknown new rules are either about to activate or have
+	// already been activated.
+	for bit := uint32(0); bit < vbNumBits; bit++ {
+		checker := bitConditionChecker{bit: bit, chain: b}
+		cache := &b.warningCaches[bit]
+		state, err := b.thresholdState(node.parent, checker, cache)
+		if err != nil {
+			return err
+		}
+
+		switch state {
+		case ThresholdActive:
+			if !b.unknownRulesWarned {
+				log.Warnf("Unknown new rules activated (bit %d)",
+					bit)
+				b.unknownRulesWarned = true
+			}
+
+		case ThresholdLockedIn:
+			window := int32(checker.MinerConfirmationWindow())
+			activationHeight := window - (node.height % window)
+			log.Warnf("Unknown new rules are about to activate in "+
+				"%d blocks (bit %d)", activationHeight, bit)
+		}
+	}
+
+	return nil
+}
+
+// warnUnknownVersions logs a warning if a high enough percentage of the last
+// blocks have unexpected versions.
+//
+// This function MUST be called with the chain state lock held (for writes)
+func (b *BlockChain) warnUnknownVersions(node *blockNode) error {
+	// Nothing to do if already warned.
+	if b.unknownVersionsWarned {
+		return nil
+	}
+
+	// Warn if enough previous blocks have unexpected versions.
+	numUpgraded := uint32(0)
+	for i := uint32(0); i < unknownVerNumToCheck && node != nil; i++ {
+		expectedVersion, err := b.calcNextBlockVersion(node.parent)
+		if err != nil {
+			return err
+		}
+		if expectedVersion > vbLegacyBlockVersion &&
+			(node.version & ^expectedVersion) != 0 {
+
+			numUpgraded++
+		}
+
+		node = node.parent
+	}
+	if numUpgraded > unknownVerWarnNum {
+		log.Warn("Unknown block versions are being mined, so new " +
+			"rules might be in effect.  Are you running the " +
+			"latest version of the software?")
+		b.unknownVersionsWarned = true
+	}
+
+	return nil
+}