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stakeversion.go
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stakeversion.go
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// Copyright (c) 2016-2018 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package blockchain
import (
"encoding/binary"
"errors"
"fmt"
"github.com/decred/dcrd/chaincfg/chainhash"
)
var (
errVoterVersionMajorityNotFound = errors.New("voter version majority " +
"not found")
errStakeVersionMajorityNotFound = errors.New("stake version majority " +
"not found")
)
// stakeMajorityCacheVersionKey creates a map key that is comprised of a stake
// version and a hash. This is used for caches that require a version in
// addition to a simple hash.
func stakeMajorityCacheVersionKey(version uint32, hash *chainhash.Hash) [stakeMajorityCacheKeySize]byte {
key := [stakeMajorityCacheKeySize]byte{}
binary.LittleEndian.PutUint32(key[0:], version)
copy(key[4:], hash[:])
return key
}
// calcWantHeight calculates the height of the final block of the previous
// interval given a stake validation height, stake validation interval, and
// block height.
func calcWantHeight(stakeValidationHeight, interval, height int64) int64 {
intervalOffset := stakeValidationHeight % interval
// The adjusted height accounts for the fact the starting validation
// height does not necessarily start on an interval and thus the
// intervals might not be zero-based.
adjustedHeight := height - intervalOffset - 1
return (adjustedHeight - ((adjustedHeight + 1) % interval)) +
intervalOffset
}
// CalcWantHeight calculates the height of the final block of the previous
// interval given a block height.
func (b *BlockChain) CalcWantHeight(interval, height int64) int64 {
return calcWantHeight(b.chainParams.StakeValidationHeight, interval,
height)
}
// findStakeVersionPriorNode walks the chain backwards from prevNode until it
// reaches the final block of the previous stake version interval and returns
// that node. The returned node will be nil when the provided prevNode is too
// low such that there is no previous stake version interval due to falling
// prior to the stake validation interval.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) findStakeVersionPriorNode(prevNode *blockNode) (*blockNode, error) {
// Check to see if the blockchain is high enough to begin accounting
// stake versions.
nextHeight := prevNode.height + 1
if nextHeight < b.chainParams.StakeValidationHeight+
b.chainParams.StakeVersionInterval {
return nil, nil
}
wantHeight := calcWantHeight(b.chainParams.StakeValidationHeight,
b.chainParams.StakeVersionInterval, nextHeight)
// Walk backwards until we find an interval block and make sure we
// don't blow through the minimum height.
iterNode := prevNode
for iterNode.height > wantHeight {
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
return nil, err
}
}
return iterNode, nil
}
// isVoterMajorityVersion determines if minVer requirement is met based on
// prevNode. The function always uses the voter versions of the prior window.
// For example, if StakeVersionInterval = 11 and StakeValidationHeight = 13 the
// windows start at 13 + 11 -1 = 24 and are as follows: 24-34, 35-45, 46-56 ...
// If height comes in at 35 we use the 24-34 window, up to height 45.
// If height comes in at 46 we use the 35-45 window, up to height 56 etc.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) isVoterMajorityVersion(minVer uint32, prevNode *blockNode) bool {
// Walk blockchain backwards to calculate version.
node, err := b.findStakeVersionPriorNode(prevNode)
if err != nil {
return false
}
if node == nil {
return 0 >= minVer
}
// Generate map key and look up cached result.
key := stakeMajorityCacheVersionKey(minVer, &node.hash)
if result, ok := b.isVoterMajorityVersionCache[key]; ok {
return result
}
// Tally both the total number of votes in the previous stake version validation
// interval and how many of those votes are at least the requested minimum
// version.
totalVotesFound := int32(0)
versionCount := int32(0)
iterNode := node
for i := int64(0); i < b.chainParams.StakeVersionInterval && iterNode != nil; i++ {
totalVotesFound += int32(len(iterNode.votes))
for _, v := range iterNode.votes {
if v.Version >= minVer {
versionCount += 1
}
}
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
return false
}
}
// Determine the required amount of votes to reach supermajority.
numRequired := totalVotesFound * b.chainParams.StakeMajorityMultiplier /
b.chainParams.StakeMajorityDivisor
// Cache value.
result := versionCount >= numRequired
b.isVoterMajorityVersionCache[key] = result
return result
}
// isStakeMajorityVersion determines if minVer requirement is met based on
// prevNode. The function always uses the stake versions of the prior window.
// For example, if StakeVersionInterval = 11 and StakeValidationHeight = 13 the
// windows start at 13 + (11 * 2) 25 and are as follows: 24-34, 35-45, 46-56 ...
// If height comes in at 35 we use the 24-34 window, up to height 45.
// If height comes in at 46 we use the 35-45 window, up to height 56 etc.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) isStakeMajorityVersion(minVer uint32, prevNode *blockNode) bool {
// Walk blockchain backwards to calculate version.
node, err := b.findStakeVersionPriorNode(prevNode)
if err != nil {
return false
}
if node == nil {
return 0 >= minVer
}
// Generate map key and look up cached result.
key := stakeMajorityCacheVersionKey(minVer, &node.hash)
if result, ok := b.isStakeMajorityVersionCache[key]; ok {
return result
}
// Tally how many of the block headers in the previous stake version validation
// interval have their stake version set to at least the requested minimum
// version.
versionCount := int32(0)
iterNode := node
for i := int64(0); i < b.chainParams.StakeVersionInterval && iterNode != nil; i++ {
if iterNode.stakeVersion >= minVer {
versionCount += 1
}
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
b.isStakeMajorityVersionCache[key] = false
return false
}
}
// Determine the required amount of votes to reach supermajority.
numRequired := int32(b.chainParams.StakeVersionInterval) *
b.chainParams.StakeMajorityMultiplier /
b.chainParams.StakeMajorityDivisor
// Cache result.
result := versionCount >= numRequired
b.isStakeMajorityVersionCache[key] = result
return result
}
// calcPriorStakeVersion calculates the header stake version of the prior
// interval. The function walks the chain backwards by one interval and then
// it performs a standard majority calculation.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) calcPriorStakeVersion(prevNode *blockNode) (uint32, error) {
// Walk blockchain backwards to calculate version.
node, err := b.findStakeVersionPriorNode(prevNode)
if err != nil {
return 0, err
}
if node == nil {
return 0, nil
}
// Check cache.
if result, ok := b.calcPriorStakeVersionCache[node.hash]; ok {
return result, nil
}
// Tally how many of each stake version the block headers in the previous stake
// version validation interval have.
versions := make(map[uint32]int32) // [version][count]
iterNode := node
for i := int64(0); i < b.chainParams.StakeVersionInterval && iterNode != nil; i++ {
versions[iterNode.stakeVersion]++
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
return 0, err
}
}
// Determine the required amount of votes to reach supermajority.
numRequired := int32(b.chainParams.StakeVersionInterval) *
b.chainParams.StakeMajorityMultiplier /
b.chainParams.StakeMajorityDivisor
for version, count := range versions {
if count >= numRequired {
b.calcPriorStakeVersionCache[node.hash] = version
return version, nil
}
}
return 0, errStakeVersionMajorityNotFound
}
// calcVoterVersionInterval tallies all voter versions in an interval and
// returns a version that has reached 75% majority. This function MUST be
// called with a node that is the final node in a valid stake version interval
// and greater than or equal to the stake validation height or it will result in
// an assertion error.
//
// This function is really meant to be called internally only from this file.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) calcVoterVersionInterval(prevNode *blockNode) (uint32, error) {
// Ensure the provided node is the final node in a valid stake version
// interval and is greater than or equal to the stake validation height
// since the logic below relies on these assumptions.
svh := b.chainParams.StakeValidationHeight
svi := b.chainParams.StakeVersionInterval
expectedHeight := calcWantHeight(svh, svi, prevNode.height+1)
if prevNode.height != expectedHeight || expectedHeight < svh {
return 0, AssertError(fmt.Sprintf("calcVoterVersionInterval "+
"must be called with a node that is the final node "+
"in a stake version interval -- called with node %s "+
"(height %d)", prevNode.hash, prevNode.height))
}
// See if we have cached results.
if result, ok := b.calcVoterVersionIntervalCache[prevNode.hash]; ok {
return result, nil
}
// Tally both the total number of votes in the previous stake version validation
// interval and how many of each version those votes have.
var err error
versions := make(map[uint32]int32) // [version][count]
totalVotesFound := int32(0)
iterNode := prevNode
for i := int64(0); i < svi && iterNode != nil; i++ {
totalVotesFound += int32(len(iterNode.votes))
for _, v := range iterNode.votes {
versions[v.Version]++
}
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
return 0, err
}
}
// Determine the required amount of votes to reach supermajority.
numRequired := totalVotesFound * b.chainParams.StakeMajorityMultiplier /
b.chainParams.StakeMajorityDivisor
for version, count := range versions {
if count >= numRequired {
b.calcVoterVersionIntervalCache[prevNode.hash] = version
return version, nil
}
}
return 0, errVoterVersionMajorityNotFound
}
// calcVoterVersion calculates the last prior valid majority stake version. If
// the current interval does not have a majority stake version it'll go back to
// the prior interval. It'll keep going back up to the minimum height at which
// point we know the version was 0.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) calcVoterVersion(prevNode *blockNode) (uint32, *blockNode) {
// Walk blockchain backwards to find interval.
node, err := b.findStakeVersionPriorNode(prevNode)
if err != nil {
return 0, nil
}
// Iterate over versions until a majority is found. Don't try to count
// votes before the stake validation height since there could not
// possibly have been any.
for node != nil && node.height >= b.chainParams.StakeValidationHeight {
version, err := b.calcVoterVersionInterval(node)
if err == nil {
return version, node
}
if err != errVoterVersionMajorityNotFound {
break
}
prevIntervalHeight := node.height - b.chainParams.StakeVersionInterval
node, err = b.index.AncestorNode(node, prevIntervalHeight)
if err != nil {
break
}
}
// We didn't find a marority version.
return 0, nil
}
// calcStakeVersion calculates the header stake version based on voter
// versions. If there is a majority of voter versions it uses the header stake
// version to prevent reverting to a prior version.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) calcStakeVersion(prevNode *blockNode) uint32 {
version, node := b.calcVoterVersion(prevNode)
if version == 0 || node == nil {
// short circuit
return 0
}
// Check cache.
if result, ok := b.calcStakeVersionCache[node.hash]; ok {
return result
}
// Walk chain backwards to start of node interval (start of current
// period) Note that calcWantHeight returns the LAST height of the
// prior interval; hence the + 1.
startIntervalHeight := calcWantHeight(b.chainParams.StakeValidationHeight,
b.chainParams.StakeVersionInterval, node.height) + 1
iterNode := node
for iterNode.height > startIntervalHeight {
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil || iterNode == nil {
b.calcStakeVersionCache[node.hash] = 0
return 0
}
}
// See if we are enforcing V3 blocks yet. Just return V0 since it it
// wasn't enforced and therefore irrelevant.
if !b.isMajorityVersion(3, iterNode,
b.chainParams.BlockRejectNumRequired) {
b.calcStakeVersionCache[node.hash] = 0
return 0
}
ourVersion := version
if b.isStakeMajorityVersion(version, node) {
priorVersion, _ := b.calcPriorStakeVersion(node)
if version <= priorVersion {
ourVersion = priorVersion
}
}
b.calcStakeVersionCache[node.hash] = ourVersion
return ourVersion
}
// calcStakeVersionByHash calculates the last prior valid majority stake
// version. If the current interval does not have a majority stake version
// it'll go back to the prior interval. It'll keep going back up to the
// minimum height at which point we know the version was 0.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) calcStakeVersionByHash(hash *chainhash.Hash) (uint32, error) {
prevNode, err := b.findNode(hash, 0)
if err != nil {
return 0, err
}
return b.calcStakeVersion(prevNode), nil
}
// CalcStakeVersionByHash calculates the expected stake version for the
// provided block hash.
//
// This function is safe for concurrent access.
func (b *BlockChain) CalcStakeVersionByHash(hash *chainhash.Hash) (uint32, error) {
b.chainLock.Lock()
defer b.chainLock.Unlock()
return b.calcStakeVersionByHash(hash)
}