github.com/marconiprotocol/go-methereum-lite@v0.0.0-20190918214227-3cd8b06fcf99/consensus/ethash/consensus.go

// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package ethash

import (
	"bytes"
	"errors"
	"fmt"
	"math/big"
	"runtime"
	"time"

	mapset "github.com/deckarep/golang-set"
	"github.com/MarconiProtocol/go-methereum-lite/common"
	"github.com/MarconiProtocol/go-methereum-lite/common/math"
	"github.com/MarconiProtocol/go-methereum-lite/consensus"
	"github.com/MarconiProtocol/go-methereum-lite/consensus/misc"
	"github.com/MarconiProtocol/go-methereum-lite/core/state"
	"github.com/MarconiProtocol/go-methereum-lite/core/types"
	"github.com/MarconiProtocol/go-methereum-lite/log"
	"github.com/MarconiProtocol/go-methereum-lite/params"
	"github.com/MarconiProtocol/go-methereum-lite/rlp"
	"golang.org/x/crypto/sha3"
	"github.com/MarconiProtocol/marconi-cryptonight"
)

// Ethash proof-of-work protocol constants.
var (
	SoftLaunchBlockReward           = big.NewInt(1e+18)                               // Block reward in wei for successfully mining a block during the soft launch period
	MIP1BlockReward                 = big.NewInt(2e+18)                               // Block reward in wei for successfully mining a block upward from MIP1Block
	MIP2BlockReward                 = big.NewInt(5e+18)                               // Block reward in wei for successfully mining a block upward from MIP2Block
	// Note: big.NewInt(int64) overflows for higher digits, use SetString for 10 or higher block rewards
	MIP3BlockReward, _              = new(big.Int).SetString("10000000000000000000", 10) // Block reward in wei for successfully mining a block upward from MIP3Block
	MIP4BlockReward                 = big.NewInt(5e+18)                               // Block reward in wei for successfully mining a block upward from MIP4Block
	DefaultBlockReward              = big.NewInt(3e+18)                               // Default block reward
	maxUncles                       = 2                                                  // Maximum number of uncles allowed in a single block
	allowedFutureBlockTime          = 15 * time.Second                                   // Max time from current time allowed for blocks, before they're considered future blocks
)

// Various error messages to mark blocks invalid. These should be private to
// prevent engine specific errors from being referenced in the remainder of the
// codebase, inherently breaking if the engine is swapped out. Please put common
// error types into the consensus package.
var (
	errLargeBlockTime    = errors.New("timestamp too big")
	errZeroBlockTime     = errors.New("timestamp equals parent's")
	errTooManyUncles     = errors.New("too many uncles")
	errDuplicateUncle    = errors.New("duplicate uncle")
	errUncleIsAncestor   = errors.New("uncle is ancestor")
	errDanglingUncle     = errors.New("uncle's parent is not ancestor")
	errInvalidDifficulty = errors.New("non-positive difficulty")
	errInvalidMixDigest  = errors.New("invalid mix digest")
	errInvalidPoW        = errors.New("invalid proof-of-work")
)

// Author implements consensus.Engine, returning the header's coinbase as the
// proof-of-work verified author of the block.
func (ethash *Ethash) Author(header *types.Header) (common.Address, error) {
	return header.Coinbase, nil
}

// VerifyHeader checks whether a header conforms to the consensus rules of the
// stock Ethereum ethash engine.
func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
	// If we're running a full engine faking, accept any input as valid
	if ethash.config.PowMode == ModeFullFake {
		return nil
	}
	// Short circuit if the header is known, or it's parent not
	number := header.Number.Uint64()
	if chain.GetHeader(header.Hash(), number) != nil {
		return nil
	}
	parent := chain.GetHeader(header.ParentHash, number-1)
	if parent == nil {
		return consensus.ErrUnknownAncestor
	}
	// Sanity checks passed, do a proper verification
	return ethash.verifyHeader(chain, header, parent, false, seal)
}

// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
// concurrently. The method returns a quit channel to abort the operations and
// a results channel to retrieve the async verifications.
func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
	// If we're running a full engine faking, accept any input as valid
	if ethash.config.PowMode == ModeFullFake || len(headers) == 0 {
		abort, results := make(chan struct{}), make(chan error, len(headers))
		for i := 0; i < len(headers); i++ {
			results <- nil
		}
		return abort, results
	}

	// Spawn as many workers as allowed threads
	workers := runtime.GOMAXPROCS(0)
	if len(headers) < workers {
		workers = len(headers)
	}

	// Create a task channel and spawn the verifiers
	var (
		inputs = make(chan int)
		done   = make(chan int, workers)
		errors = make([]error, len(headers))
		abort  = make(chan struct{})
	)
	for i := 0; i < workers; i++ {
		go func() {
			for index := range inputs {
				errors[index] = ethash.verifyHeaderWorker(chain, headers, seals, index)
				done <- index
			}
		}()
	}

	errorsOut := make(chan error, len(headers))
	go func() {
		defer close(inputs)
		var (
			in, out = 0, 0
			checked = make([]bool, len(headers))
			inputs  = inputs
		)
		for {
			select {
			case inputs <- in:
				if in++; in == len(headers) {
					// Reached end of headers. Stop sending to workers.
					inputs = nil
				}
			case index := <-done:
				for checked[index] = true; checked[out]; out++ {
					errorsOut <- errors[out]
					if out == len(headers)-1 {
						return
					}
				}
			case <-abort:
				return
			}
		}
	}()
	return abort, errorsOut
}

func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainReader, headers []*types.Header, seals []bool, index int) error {
	var parent *types.Header
	if index == 0 {
		parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1)
	} else if headers[index-1].Hash() == headers[index].ParentHash {
		parent = headers[index-1]
	}
	if parent == nil {
		return consensus.ErrUnknownAncestor
	}
	if chain.GetHeader(headers[index].Hash(), headers[index].Number.Uint64()) != nil {
		return nil // known block
	}
	return ethash.verifyHeader(chain, headers[index], parent, false, seals[index])
}

// VerifyUncles verifies that the given block's uncles conform to the consensus
// rules of the stock Ethereum ethash engine.
func (ethash *Ethash) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
	// If we're running a full engine faking, accept any input as valid
	if ethash.config.PowMode == ModeFullFake {
		return nil
	}
	// Verify that there are at most 2 uncles included in this block
	if len(block.Uncles()) > maxUncles {
		return errTooManyUncles
	}
	// Gather the set of past uncles and ancestors
	uncles, ancestors := mapset.NewSet(), make(map[common.Hash]*types.Header)

	number, parent := block.NumberU64()-1, block.ParentHash()
	for i := 0; i < 7; i++ {
		ancestor := chain.GetBlock(parent, number)
		if ancestor == nil {
			break
		}
		ancestors[ancestor.Hash()] = ancestor.Header()
		for _, uncle := range ancestor.Uncles() {
			uncles.Add(uncle.Hash())
		}
		parent, number = ancestor.ParentHash(), number-1
	}
	ancestors[block.Hash()] = block.Header()
	uncles.Add(block.Hash())

	// Verify each of the uncles that it's recent, but not an ancestor
	for _, uncle := range block.Uncles() {
		// Make sure every uncle is rewarded only once
		hash := uncle.Hash()
		if uncles.Contains(hash) {
			return errDuplicateUncle
		}
		uncles.Add(hash)

		// Make sure the uncle has a valid ancestry
		if ancestors[hash] != nil {
			return errUncleIsAncestor
		}
		if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == block.ParentHash() {
			return errDanglingUncle
		}
		if err := ethash.verifyHeader(chain, uncle, ancestors[uncle.ParentHash], true, true); err != nil {
			return err
		}
	}
	return nil
}

// verifyHeader checks whether a header conforms to the consensus rules of the
// stock Ethereum ethash engine.
// See YP section 4.3.4. "Block Header Validity"
func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *types.Header, uncle bool, seal bool) error {
	// Ensure that the header's extra-data section is of a reasonable size
	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
		return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), params.MaximumExtraDataSize)
	}
	// Verify the header's timestamp
	if uncle {
		if header.Time.Cmp(math.MaxBig256) > 0 {
			return errLargeBlockTime
		}
	} else {
		if header.Time.Cmp(big.NewInt(time.Now().Add(allowedFutureBlockTime).Unix())) > 0 {
			return consensus.ErrFutureBlock
		}
	}
	if header.Time.Cmp(parent.Time) <= 0 {
		return errZeroBlockTime
	}
	// Verify the block's difficulty based in it's timestamp and parent's difficulty
	expected := ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)

	if expected.Cmp(header.Difficulty) != 0 {
		return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected)
	}
	// Verify that the gas limit is <= 2^63-1
	cap := uint64(0x7fffffffffffffff)
	if header.GasLimit > cap {
		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, cap)
	}
	// Verify that the gasUsed is <= gasLimit
	if header.GasUsed > header.GasLimit {
		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit)
	}

	// Verify that the gas limit remains within allowed bounds
	diff := int64(parent.GasLimit) - int64(header.GasLimit)
	if diff < 0 {
		diff *= -1
	}
	limit := parent.GasLimit / params.GasLimitBoundDivisor

	if uint64(diff) >= limit || header.GasLimit < params.MinGasLimit {
		return fmt.Errorf("invalid gas limit: have %d, want %d += %d", header.GasLimit, parent.GasLimit, limit)
	}
	// Verify that the block number is parent's +1
	if diff := new(big.Int).Sub(header.Number, parent.Number); diff.Cmp(big.NewInt(1)) != 0 {
		return consensus.ErrInvalidNumber
	}
	// Verify the engine specific seal securing the block
	if seal {
		if err := ethash.VerifySeal(chain, header); err != nil {
			return err
		}
	}
	// If all checks passed, validate any special fields for hard forks
	if err := misc.VerifyDAOHeaderExtraData(chain.Config(), header); err != nil {
		return err
	}
	if err := misc.VerifyForkHashes(chain.Config(), header, uncle); err != nil {
		return err
	}
	return nil
}

// CalcDifficulty is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time
// given the parent block's time and difficulty.
func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
	return CalcDifficulty(chain.Config(), time, parent)
}

// CalcDifficulty is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time
// given the parent block's time and difficulty.
func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
	next := new(big.Int).Add(parent.Number, big1)
	switch {
	case config.IsByzantium(next):
		return calcDifficultyByzantium(time, parent)
	default:
		// still use Byzantium's algorithm, but log an warning
		log.Warn("CalcDifficulty found unknown release version in ChainConfig")
		return calcDifficultyByzantium(time, parent)
	}
}

// Some weird constants to avoid constant memory allocs for them.
var (
	big1          = big.NewInt(1)
	big3          = big.NewInt(3)
	big4          = big.NewInt(4)
	big9          = big.NewInt(9)
	bigMinus99    = big.NewInt(-99)
)

// calcDifficultyByzantium is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time given the
// parent block's time and difficulty. The calculation uses the Byzantium rules.
func calcDifficultyByzantium(time uint64, parent *types.Header) *big.Int {
	// The goal of this difficulty calculation is to stabilize the
	// average block time even as hash power is added or removed from
	// the network. Let T be the time between the new block and
	// previous block. If T is short enough, we assume this indicates
	// hashing power was added, so we increase the difficulty to make
	// blocks take longer. If T is already close to our desired
	// average block time, we leave the difficulty unchanged. If T is
	// too long, then hashing power might have been removed, so we
	// decrease the difficulty to get back to the desired average
	// block time.
	//
	// Ethereum targets a ~14 second block time, while Marconi targets
	// a ~32 second block time. Here's how the difficulty changes for
	// Marconi:
	//
	// If block time is:    then difficulty change is:
	//   0 to  8 sec          ~0.15% increase
	//   9 to 17 sec          ~0.10% increase
	//  18 to 26 sec          ~0.05% increase
	//  27 to 35 sec          no change
	//  36 to 44 sec          ~0.05% decrease
	//  45 to 53 sec          ~0.10% decrease
	//      ...                     ...
	//    >= 918 sec          ~5.00% decrease
	//
	// Except in the case of uncles. When an uncle is present in the
	// parent block, we shift the above buckets by 1 position so that
	// it's more likely that the difficulty will increase. See
	// https://gitlab.neji.vm.tc/marconi/EIPs/issues/100 for why the formula
	// takes uncles into account.
	//
	// If we ignore uncles and the cap on decrease amount, the
	// simplified mathematical formula is:
	//
	// difficulty = parent_difficulty + (3 - T/9) * parent_difficulty / 2048
	//
	// The full formula is:
	//
	// difficulty = parent_difficulty +
	//   max(-99, (4 if uncles else 3) - T/9) * parent_difficulty / 2048

	bigTime := new(big.Int).SetUint64(time)
	bigParentTime := new(big.Int).Set(parent.Time)

	// Holders for intermediate values.
	x := new(big.Int)
	y := new(big.Int)

	// T/9
	x.Sub(bigTime, bigParentTime)
	x.Div(x, big9)
	// (4 if uncles else 3) - T/9
	if parent.UncleHash == types.EmptyUncleHash {
		x.Sub(big3, x)
	} else {
		x.Sub(big4, x)
	}
	// max(-99, (4 if uncles else 3) - T/9)
	if x.Cmp(bigMinus99) < 0 {
		x.Set(bigMinus99)
	}
	// parent_difficulty + max(-99, (4 if uncles else 3) - T/9) * parent_difficulty / 2048
	y.Div(parent.Difficulty, params.DifficultyBoundDivisor)
	x.Mul(y, x)
	x.Add(parent.Difficulty, x)

	// Minimum the difficulty can ever be.
	if x.Cmp(params.MinimumDifficulty) < 0 {
		x.Set(params.MinimumDifficulty)
	}

	// TODO: determine if we need to have ice age logic which
	// exponentially jacks up the difficulty after a certain number of
	// blocks. Ice age is used in Ethereum to encourage users to
	// moving to new hard forks. Adding the logic is simple, however
	// it might be more preferable to incentivize upgrades in other
	// ways.

	return x
}

// VerifySeal implements consensus.Engine, checking whether the given block satisfies
// the PoW difficulty requirements.
func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
	return ethash.verifySeal(chain, header, false)
}

// verifySeal checks whether a block satisfies the PoW difficulty requirements,
// either using the usual ethash cache for it, or alternatively using a full DAG
// to make remote mining fast.
func (ethash *Ethash) verifySeal(chain consensus.ChainReader, header *types.Header, fulldag bool) error {
	// If we're running a fake PoW, accept any seal as valid
	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
		time.Sleep(ethash.fakeDelay)
		if ethash.fakeFail == header.Number.Uint64() {
			return errInvalidPoW
		}
		return nil
	}
	// If we're running a shared PoW, delegate verification to it
	if ethash.shared != nil {
		return ethash.shared.verifySeal(chain, header, fulldag)
	}
	// Ensure that we have a valid difficulty for the block
	if header.Difficulty.Sign() <= 0 {
		return errInvalidDifficulty
	}
	// Recompute the digest and PoW value and verify against the header
	var digest []byte
	var result []byte
	if ethash.config.PowMode == ModeQuickTest {
		digest, result = quickHash(ethash.SealHash(header).Bytes(), header.Nonce.Uint64())
	} else if ethash.config.PowMode == ModeCryptonight {
		digest, result = cryptonight.HashVariant4ForEthereumHeader(
			ethash.SealHash(header).Bytes(), header.Nonce.Uint64(), header.Number.Uint64())
	} else {
		number := header.Number.Uint64()

		// If fast-but-heavy PoW verification was requested, use an ethash dataset
		if fulldag {
			dataset := ethash.dataset(number, true)
			if dataset.generated() {
				digest, result = hashimotoFull(dataset.dataset, ethash.SealHash(header).Bytes(), header.Nonce.Uint64())

				// Datasets are unmapped in a finalizer. Ensure that the dataset stays alive
				// until after the call to hashimotoFull so it's not unmapped while being used.
				runtime.KeepAlive(dataset)
			} else {
				// Dataset not yet generated, don't hang, use a cache instead
				fulldag = false
			}
		}
		// If slow-but-light PoW verification was requested (or DAG not yet ready), use an ethash cache
		if !fulldag {
			cache := ethash.cache(number)
			size := datasetSize(number)
			if ethash.config.PowMode == ModeTest {
				size = 32 * 1024
			}
			digest, result = hashimotoLight(size, cache.cache, ethash.SealHash(header).Bytes(), header.Nonce.Uint64())

			// Caches are unmapped in a finalizer. Ensure that the cache stays alive
			// until after the call to hashimotoLight so it's not unmapped while being used.
			runtime.KeepAlive(cache)
		}
	}
	// Verify the calculated values against the ones provided in the header
	if !bytes.Equal(header.MixDigest[:], digest) {
		return errInvalidMixDigest
	}
	target := new(big.Int).Div(two256, header.Difficulty)
	if new(big.Int).SetBytes(result).Cmp(target) > 0 {
		return errInvalidPoW
	}
	return nil
}

// Prepare implements consensus.Engine, initializing the difficulty field of a
// header to conform to the ethash protocol. The changes are done inline.
func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header) error {
	parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)
	if parent == nil {
		return consensus.ErrUnknownAncestor
	}
	header.Difficulty = ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
	return nil
}

// Finalize implements consensus.Engine, accumulating the block and uncle rewards,
// setting the final state and assembling the block.
func (ethash *Ethash) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
	// Accumulate any block and uncle rewards and commit the final state root
	accumulateRewards(chain.Config(), state, header, uncles)
	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))

	// Header seems complete, assemble into a block and return
	return types.NewBlock(header, txs, uncles, receipts), nil
}

// SealHash returns the hash of a block prior to it being sealed.
func (ethash *Ethash) SealHash(header *types.Header) (hash common.Hash) {
	hasher := sha3.NewLegacyKeccak256()

	rlp.Encode(hasher, []interface{}{
		header.ParentHash,
		header.UncleHash,
		header.Coinbase,
		header.Root,
		header.TxHash,
		header.ReceiptHash,
		header.Bloom,
		header.Difficulty,
		header.Number,
		header.GasLimit,
		header.GasUsed,
		header.Time,
		header.Extra,
	})
	hasher.Sum(hash[:0])
	return hash
}

// Some weird constants to avoid constant memory allocs for them.
var (
	big8  = big.NewInt(8)
	big32 = big.NewInt(32)
)

// AccumulateRewards credits the coinbase of the given block with the mining
// reward. The total reward consists of the static block reward and rewards for
// included uncles. The coinbase of each uncle block is also rewarded.
func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
	// Select the correct block reward based on chain progression
	blockReward := SoftLaunchBlockReward
	if config.IsMIP5(header.Number) {
		blockReward = DefaultBlockReward
	} else if config.IsMIP4(header.Number) {
		blockReward = MIP4BlockReward
	} else if config.IsMIP3(header.Number) {
		blockReward = MIP3BlockReward
	} else if config.IsMIP2(header.Number) {
		blockReward = MIP2BlockReward
	} else if config.IsMIP1(header.Number) {
		blockReward = MIP1BlockReward
	}

	// Accumulate the rewards for the miner and any included uncles
	reward := new(big.Int).Set(blockReward)
	r := new(big.Int)
	for _, uncle := range uncles {
		r.Add(uncle.Number, big8)
		r.Sub(r, header.Number)
		r.Mul(r, blockReward)
		r.Div(r, big8)
		// TODO pending Token Economy research, if we want to reduce rewards of uncle blocks, the calculations for 'r' needs to be updated
		state.AddBalance(uncle.Coinbase, r)

		r.Div(blockReward, big32)
		reward.Add(reward, r)
	}

	state.AddBalance(header.Coinbase, reward)
}