Allow Parity as ingest node (#36)

* Upgrade go-ethereum to v1.8

* Add Node Info for parity nodes

* Upgrade start_private_blockchain to use v1.8

vendor/github.com/ethereum/go-ethereum/consensus/clique/clique.go

@@ -510,7 +510,6 @@ func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) erro
 	header.Nonce = types.BlockNonce{}
 
 	number := header.Number.Uint64()
-
 	// Assemble the voting snapshot to check which votes make sense
 	snap, err := c.snapshot(chain, number-1, header.ParentHash, nil)
 	if err != nil {
@@ -538,10 +537,8 @@ func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) erro
 		c.lock.RUnlock()
 	}
 	// Set the correct difficulty
-	header.Difficulty = diffNoTurn
-	if snap.inturn(header.Number.Uint64(), c.signer) {
-		header.Difficulty = diffInTurn
-	}
+	header.Difficulty = CalcDifficulty(snap, c.signer)
+
 	// Ensure the extra data has all it's components
 	if len(header.Extra) < extraVanity {
 		header.Extra = append(header.Extra, bytes.Repeat([]byte{0x00}, extraVanity-len(header.Extra))...)
@@ -630,7 +627,7 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-ch
 		}
 	}
 	// Sweet, the protocol permits us to sign the block, wait for our time
-	delay := time.Unix(header.Time.Int64(), 0).Sub(time.Now())
+	delay := time.Unix(header.Time.Int64(), 0).Sub(time.Now()) // nolint: gosimple
 	if header.Difficulty.Cmp(diffNoTurn) == 0 {
 		// It's not our turn explicitly to sign, delay it a bit
 		wiggle := time.Duration(len(snap.Signers)/2+1) * wiggleTime
@@ -655,6 +652,27 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-ch
 	return block.WithSeal(header), nil
 }
 
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+// that a new block should have based on the previous blocks in the chain and the
+// current signer.
+func (c *Clique) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+	snap, err := c.snapshot(chain, parent.Number.Uint64(), parent.Hash(), nil)
+	if err != nil {
+		return nil
+	}
+	return CalcDifficulty(snap, c.signer)
+}
+
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+// that a new block should have based on the previous blocks in the chain and the
+// current signer.
+func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
+	if snap.inturn(snap.Number+1, signer) {
+		return new(big.Int).Set(diffInTurn)
+	}
+	return new(big.Int).Set(diffNoTurn)
+}
+
 // APIs implements consensus.Engine, returning the user facing RPC API to allow
 // controlling the signer voting.
 func (c *Clique) APIs(chain consensus.ChainReader) []rpc.API {

vendor/github.com/ethereum/go-ethereum/consensus/consensus.go

@@ -23,6 +23,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
+	"math/big"
 )
 
 // ChainReader defines a small collection of methods needed to access the local
@@ -88,6 +89,10 @@ type Engine interface {
 	// seal place on top.
 	Seal(chain ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error)
 
+	// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+	// that a new block should have.
+	CalcDifficulty(chain ChainReader, time uint64, parent *types.Header) *big.Int
+
 	// APIs returns the RPC APIs this consensus engine provides.
 	APIs(chain ChainReader) []rpc.API
 }

vendor/github.com/ethereum/go-ethereum/consensus/errors.go

@@ -23,6 +23,10 @@ var (
 	// that is unknown.
 	ErrUnknownAncestor = errors.New("unknown ancestor")
 
+	// ErrPrunedAncestor is returned when validating a block requires an ancestor
+	// that is known, but the state of which is not available.
+	ErrPrunedAncestor = errors.New("pruned ancestor")
+
 	// ErrFutureBlock is returned when a block's timestamp is in the future according
 	// to the current node.
 	ErrFutureBlock = errors.New("block in the future")

vendor/github.com/ethereum/go-ethereum/consensus/ethash/algorithm.go

@@ -19,6 +19,7 @@ package ethash
 import (
 	"encoding/binary"
 	"hash"
+	"math/big"
 	"reflect"
 	"runtime"
 	"sync"
@@ -47,6 +48,48 @@ const (
 	loopAccesses       = 64      // Number of accesses in hashimoto loop
 )
 
+// cacheSize returns the size of the ethash verification cache that belongs to a certain
+// block number.
+func cacheSize(block uint64) uint64 {
+	epoch := int(block / epochLength)
+	if epoch < maxEpoch {
+		return cacheSizes[epoch]
+	}
+	return calcCacheSize(epoch)
+}
+
+// calcCacheSize calculates the cache size for epoch. The cache size grows linearly,
+// however, we always take the highest prime below the linearly growing threshold in order
+// to reduce the risk of accidental regularities leading to cyclic behavior.
+func calcCacheSize(epoch int) uint64 {
+	size := cacheInitBytes + cacheGrowthBytes*uint64(epoch) - hashBytes
+	for !new(big.Int).SetUint64(size / hashBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
+		size -= 2 * hashBytes
+	}
+	return size
+}
+
+// datasetSize returns the size of the ethash mining dataset that belongs to a certain
+// block number.
+func datasetSize(block uint64) uint64 {
+	epoch := int(block / epochLength)
+	if epoch < maxEpoch {
+		return datasetSizes[epoch]
+	}
+	return calcDatasetSize(epoch)
+}
+
+// calcDatasetSize calculates the dataset size for epoch. The dataset size grows linearly,
+// however, we always take the highest prime below the linearly growing threshold in order
+// to reduce the risk of accidental regularities leading to cyclic behavior.
+func calcDatasetSize(epoch int) uint64 {
+	size := datasetInitBytes + datasetGrowthBytes*uint64(epoch) - mixBytes
+	for !new(big.Int).SetUint64(size / mixBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
+		size -= 2 * mixBytes
+	}
+	return size
+}
+
 // hasher is a repetitive hasher allowing the same hash data structures to be
 // reused between hash runs instead of requiring new ones to be created.
 type hasher func(dest []byte, data []byte)
@@ -355,9 +398,11 @@ func hashimotoFull(dataset []uint32, hash []byte, nonce uint64) ([]byte, []byte)
 	return hashimoto(hash, nonce, uint64(len(dataset))*4, lookup)
 }
 
+const maxEpoch = 2048
+
 // datasetSizes is a lookup table for the ethash dataset size for the first 2048
 // epochs (i.e. 61440000 blocks).
-var datasetSizes = []uint64{
+var datasetSizes = [maxEpoch]uint64{
 	1073739904, 1082130304, 1090514816, 1098906752, 1107293056,
 	1115684224, 1124070016, 1132461952, 1140849536, 1149232768,
 	1157627776, 1166013824, 1174404736, 1182786944, 1191180416,
@@ -771,7 +816,7 @@ var datasetSizes = []uint64{
 
 // cacheSizes is a lookup table for the ethash verification cache size for the
 // first 2048 epochs (i.e. 61440000 blocks).
-var cacheSizes = []uint64{
+var cacheSizes = [maxEpoch]uint64{
 	16776896, 16907456, 17039296, 17170112, 17301056, 17432512, 17563072,
 	17693888, 17824192, 17955904, 18087488, 18218176, 18349504, 18481088,
 	18611392, 18742336, 18874304, 19004224, 19135936, 19267264, 19398208,

vendor/github.com/ethereum/go-ethereum/consensus/ethash/algorithm_go1.7.go

@@ -1,47 +0,0 @@
-// 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/>.
-
-// +build !go1.8
-
-package ethash
-
-// cacheSize calculates and returns the size of the ethash verification cache that
-// belongs to a certain block number. The cache size grows linearly, however, we
-// always take the highest prime below the linearly growing threshold in order to
-// reduce the risk of accidental regularities leading to cyclic behavior.
-func cacheSize(block uint64) uint64 {
-	// If we have a pre-generated value, use that
-	epoch := int(block / epochLength)
-	if epoch < len(cacheSizes) {
-		return cacheSizes[epoch]
-	}
-	// We don't have a way to verify primes fast before Go 1.8
-	panic("fast prime testing unsupported in Go < 1.8")
-}
-
-// datasetSize calculates and returns the size of the ethash mining dataset that
-// belongs to a certain block number. The dataset size grows linearly, however, we
-// always take the highest prime below the linearly growing threshold in order to
-// reduce the risk of accidental regularities leading to cyclic behavior.
-func datasetSize(block uint64) uint64 {
-	// If we have a pre-generated value, use that
-	epoch := int(block / epochLength)
-	if epoch < len(datasetSizes) {
-		return datasetSizes[epoch]
-	}
-	// We don't have a way to verify primes fast before Go 1.8
-	panic("fast prime testing unsupported in Go < 1.8")
-}

vendor/github.com/ethereum/go-ethereum/consensus/ethash/algorithm_go1.8.go

@@ -1,57 +0,0 @@
-// 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/>.
-
-// +build go1.8
-
-package ethash
-
-import "math/big"
-
-// cacheSize calculates and returns the size of the ethash verification cache that
-// belongs to a certain block number. The cache size grows linearly, however, we
-// always take the highest prime below the linearly growing threshold in order to
-// reduce the risk of accidental regularities leading to cyclic behavior.
-func cacheSize(block uint64) uint64 {
-	// If we have a pre-generated value, use that
-	epoch := int(block / epochLength)
-	if epoch < len(cacheSizes) {
-		return cacheSizes[epoch]
-	}
-	// No known cache size, calculate manually (sanity branch only)
-	size := cacheInitBytes + cacheGrowthBytes*uint64(epoch) - hashBytes
-	for !new(big.Int).SetUint64(size / hashBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
-		size -= 2 * hashBytes
-	}
-	return size
-}
-
-// datasetSize calculates and returns the size of the ethash mining dataset that
-// belongs to a certain block number. The dataset size grows linearly, however, we
-// always take the highest prime below the linearly growing threshold in order to
-// reduce the risk of accidental regularities leading to cyclic behavior.
-func datasetSize(block uint64) uint64 {
-	// If we have a pre-generated value, use that
-	epoch := int(block / epochLength)
-	if epoch < len(datasetSizes) {
-		return datasetSizes[epoch]
-	}
-	// No known dataset size, calculate manually (sanity branch only)
-	size := datasetInitBytes + datasetGrowthBytes*uint64(epoch) - mixBytes
-	for !new(big.Int).SetUint64(size / mixBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
-		size -= 2 * mixBytes
-	}
-	return size
-}

vendor/github.com/ethereum/go-ethereum/consensus/ethash/algorithm_go1.8_test.go

@@ -1,46 +0,0 @@
-// 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/>.
-
-// +build go1.8
-
-package ethash
-
-import "testing"
-
-// Tests whether the dataset size calculator works correctly by cross checking the
-// hard coded lookup table with the value generated by it.
-func TestSizeCalculations(t *testing.T) {
-	var tests []uint64
-
-	// Verify all the cache sizes from the lookup table
-	defer func(sizes []uint64) { cacheSizes = sizes }(cacheSizes)
-	tests, cacheSizes = cacheSizes, []uint64{}
-
-	for i, test := range tests {
-		if size := cacheSize(uint64(i*epochLength) + 1); size != test {
-			t.Errorf("cache %d: cache size mismatch: have %d, want %d", i, size, test)
-		}
-	}
-	// Verify all the dataset sizes from the lookup table
-	defer func(sizes []uint64) { datasetSizes = sizes }(datasetSizes)
-	tests, datasetSizes = datasetSizes, []uint64{}
-
-	for i, test := range tests {
-		if size := datasetSize(uint64(i*epochLength) + 1); size != test {
-			t.Errorf("dataset %d: dataset size mismatch: have %d, want %d", i, size, test)
-		}
-	}
-}

vendor/github.com/ethereum/go-ethereum/consensus/ethash/algorithm_test.go

@@ -30,6 +30,22 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 )
 
+// Tests whether the dataset size calculator works correctly by cross checking the
+// hard coded lookup table with the value generated by it.
+func TestSizeCalculations(t *testing.T) {
+	// Verify all the cache and dataset sizes from the lookup table.
+	for epoch, want := range cacheSizes {
+		if size := calcCacheSize(epoch); size != want {
+			t.Errorf("cache %d: cache size mismatch: have %d, want %d", epoch, size, want)
+		}
+	}
+	for epoch, want := range datasetSizes {
+		if size := calcDatasetSize(epoch); size != want {
+			t.Errorf("dataset %d: dataset size mismatch: have %d, want %d", epoch, size, want)
+		}
+	}
+}
+
 // Tests that verification caches can be correctly generated.
 func TestCacheGeneration(t *testing.T) {
 	tests := []struct {
@@ -688,8 +704,8 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 		TxHash:      common.HexToHash("0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"),
 		ReceiptHash: common.HexToHash("0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"),
 		Difficulty:  big.NewInt(167925187834220),
-		GasLimit:    big.NewInt(4015682),
-		GasUsed:     big.NewInt(0),
+		GasLimit:    4015682,
+		GasUsed:     0,
 		Time:        big.NewInt(1488928920),
 		Extra:       []byte("www.bw.com"),
 		MixDigest:   common.HexToHash("0x3e140b0784516af5e5ec6730f2fb20cca22f32be399b9e4ad77d32541f798cd0"),
@@ -703,8 +719,7 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 
 		go func(idx int) {
 			defer pend.Done()
-
-			ethash := New(cachedir, 0, 1, "", 0, 0)
+			ethash := New(Config{cachedir, 0, 1, "", 0, 0, ModeNormal})
 			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
 			}

vendor/github.com/ethereum/go-ethereum/consensus/ethash/consensus.go

@@ -36,9 +36,10 @@ import (
 
 // Ethash proof-of-work protocol constants.
 var (
-	frontierBlockReward  *big.Int = big.NewInt(5e+18) // Block reward in wei for successfully mining a block
-	byzantiumBlockReward *big.Int = big.NewInt(3e+18) // Block reward in wei for successfully mining a block upward from Byzantium
-	maxUncles                     = 2                 // Maximum number of uncles allowed in a single block
+	FrontierBlockReward    *big.Int = big.NewInt(5e+18) // Block reward in wei for successfully mining a block
+	ByzantiumBlockReward   *big.Int = big.NewInt(3e+18) // Block reward in wei for successfully mining a block upward from Byzantium
+	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
@@ -52,7 +53,6 @@ var (
 	errDuplicateUncle    = errors.New("duplicate uncle")
 	errUncleIsAncestor   = errors.New("uncle is ancestor")
 	errDanglingUncle     = errors.New("uncle's parent is not ancestor")
-	errNonceOutOfRange   = errors.New("nonce out of range")
 	errInvalidDifficulty = errors.New("non-positive difficulty")
 	errInvalidMixDigest  = errors.New("invalid mix digest")
 	errInvalidPoW        = errors.New("invalid proof-of-work")
@@ -68,7 +68,7 @@ func (ethash *Ethash) Author(header *types.Header) (common.Address, error) {
 // 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.fakeFull {
+	if ethash.config.PowMode == ModeFullFake {
 		return nil
 	}
 	// Short circuit if the header is known, or it's parent not
@@ -89,7 +89,7 @@ func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.He
 // 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.fakeFull || len(headers) == 0 {
+	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
@@ -169,7 +169,7 @@ func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainReader, headers []
 // 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.fakeFull {
+	if ethash.config.PowMode == ModeFullFake {
 		return nil
 	}
 	// Verify that there are at most 2 uncles included in this block
@@ -231,7 +231,7 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 			return errLargeBlockTime
 		}
 	} else {
-		if header.Time.Cmp(big.NewInt(time.Now().Unix())) > 0 {
+		if header.Time.Cmp(big.NewInt(time.Now().Add(allowedFutureBlockTime).Unix())) > 0 {
 			return consensus.ErrFutureBlock
 		}
 	}
@@ -239,29 +239,30 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 		return errZeroBlockTime
 	}
 	// Verify the block's difficulty based in it's timestamp and parent's difficulty
-	expected := CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
+	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
-	if header.GasLimit.Cmp(math.MaxBig63) > 0 {
-		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, math.MaxBig63)
+	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.Cmp(header.GasLimit) > 0 {
-		return fmt.Errorf("invalid gasUsed: have %v, gasLimit %v", header.GasUsed, header.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 := new(big.Int).Set(parent.GasLimit)
-	diff = diff.Sub(diff, header.GasLimit)
-	diff.Abs(diff)
+	diff := int64(parent.GasLimit) - int64(header.GasLimit)
+	if diff < 0 {
+		diff *= -1
+	}
+	limit := parent.GasLimit / params.GasLimitBoundDivisor
 
-	limit := new(big.Int).Set(parent.GasLimit)
-	limit = limit.Div(limit, params.GasLimitBoundDivisor)
-
-	if diff.Cmp(limit) >= 0 || header.GasLimit.Cmp(params.MinGasLimit) < 0 {
-		return fmt.Errorf("invalid gas limit: have %v, want %v += %v", header.GasLimit, parent.GasLimit, limit)
+	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 {
@@ -286,7 +287,13 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, 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.
-// TODO (karalabe): Move the chain maker into this package and make this private!
+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 {
@@ -339,7 +346,7 @@ func calcDifficultyByzantium(time uint64, parent *types.Header) *big.Int {
 	if x.Cmp(bigMinus99) < 0 {
 		x.Set(bigMinus99)
 	}
-	// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
+	// parent_diff + (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99))
 	y.Div(parent.Difficulty, params.DifficultyBoundDivisor)
 	x.Mul(y, x)
 	x.Add(parent.Difficulty, x)
@@ -348,7 +355,7 @@ func calcDifficultyByzantium(time uint64, parent *types.Header) *big.Int {
 	if x.Cmp(params.MinimumDifficulty) < 0 {
 		x.Set(params.MinimumDifficulty)
 	}
-	// calculate a fake block numer for the ice-age delay:
+	// calculate a fake block number for the ice-age delay:
 	//   https://github.com/ethereum/EIPs/pull/669
 	//   fake_block_number = min(0, block.number - 3_000_000
 	fakeBlockNumber := new(big.Int)
@@ -373,7 +380,7 @@ func calcDifficultyByzantium(time uint64, parent *types.Header) *big.Int {
 // the difficulty that a new block should have when created at time given the
 // parent block's time and difficulty. The calculation uses the Homestead rules.
 func calcDifficultyHomestead(time uint64, parent *types.Header) *big.Int {
-	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
+	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.md
 	// algorithm:
 	// diff = (parent_diff +
 	//         (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
@@ -455,7 +462,7 @@ func calcDifficultyFrontier(time uint64, parent *types.Header) *big.Int {
 // the PoW difficulty requirements.
 func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
 	// If we're running a fake PoW, accept any seal as valid
-	if ethash.fakeMode {
+	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
 		time.Sleep(ethash.fakeDelay)
 		if ethash.fakeFail == header.Number.Uint64() {
 			return errInvalidPoW
@@ -466,24 +473,23 @@ func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Head
 	if ethash.shared != nil {
 		return ethash.shared.VerifySeal(chain, header)
 	}
-	// Sanity check that the block number is below the lookup table size (60M blocks)
-	number := header.Number.Uint64()
-	if number/epochLength >= uint64(len(cacheSizes)) {
-		// Go < 1.7 cannot calculate new cache/dataset sizes (no fast prime check)
-		return errNonceOutOfRange
-	}
 	// 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
-	cache := ethash.cache(number)
+	number := header.Number.Uint64()
 
+	cache := ethash.cache(number)
 	size := datasetSize(number)
-	if ethash.tester {
+	if ethash.config.PowMode == ModeTest {
 		size = 32 * 1024
 	}
-	digest, result := hashimotoLight(size, cache, header.HashNoNonce().Bytes(), header.Nonce.Uint64())
+	digest, result := hashimotoLight(size, cache.cache, header.HashNoNonce().Bytes(), header.Nonce.Uint64())
+	// Caches are unmapped in a finalizer. Ensure that the cache stays live
+	// until after the call to hashimotoLight so it's not unmapped while being used.
+	runtime.KeepAlive(cache)
+
 	if !bytes.Equal(header.MixDigest[:], digest) {
 		return errInvalidMixDigest
 	}
@@ -501,8 +507,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 	if parent == nil {
 		return consensus.ErrUnknownAncestor
 	}
-	header.Difficulty = CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
-
+	header.Difficulty = ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
 	return nil
 }
 
@@ -510,7 +515,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 // 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)
+	accumulateRewards(chain.Config(), state, header, uncles)
 	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
 
 	// Header seems complete, assemble into a block and return
@@ -526,12 +531,11 @@ var (
 // 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.
-// TODO (karalabe): Move the chain maker into this package and make this private!
-func AccumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
+func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
 	// Select the correct block reward based on chain progression
-	blockReward := frontierBlockReward
+	blockReward := FrontierBlockReward
 	if config.IsByzantium(header.Number) {
-		blockReward = byzantiumBlockReward
+		blockReward = ByzantiumBlockReward
 	}
 	// Accumulate the rewards for the miner and any included uncles
 	reward := new(big.Int).Set(blockReward)

vendor/github.com/ethereum/go-ethereum/consensus/ethash/consensus_test.go

@@ -71,6 +71,7 @@ func TestCalcDifficulty(t *testing.T) {
 	}
 
 	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
+
 	for name, test := range tests {
 		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
 		diff := CalcDifficulty(config, test.CurrentTimestamp, &types.Header{

vendor/github.com/ethereum/go-ethereum/consensus/ethash/ethash.go

@@ -26,6 +26,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"strconv"
 	"sync"
 	"time"
@@ -34,8 +35,9 @@ import (
 	mmap "github.com/edsrzf/mmap-go"
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/rpc"
-	metrics "github.com/rcrowley/go-metrics"
+	"github.com/hashicorp/golang-lru/simplelru"
 )
 
 var ErrInvalidDumpMagic = errors.New("invalid dump magic")
@@ -45,7 +47,7 @@ var (
 	maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
 
 	// sharedEthash is a full instance that can be shared between multiple users.
-	sharedEthash = New("", 3, 0, "", 1, 0)
+	sharedEthash = New(Config{"", 3, 0, "", 1, 0, ModeNormal})
 
 	// algorithmRevision is the data structure version used for file naming.
 	algorithmRevision = 23
@@ -142,32 +144,82 @@ func memoryMapAndGenerate(path string, size uint64, generator func(buffer []uint
 	return memoryMap(path)
 }
 
+// lru tracks caches or datasets by their last use time, keeping at most N of them.
+type lru struct {
+	what string
+	new  func(epoch uint64) interface{}
+	mu   sync.Mutex
+	// Items are kept in a LRU cache, but there is a special case:
+	// We always keep an item for (highest seen epoch) + 1 as the 'future item'.
+	cache      *simplelru.LRU
+	future     uint64
+	futureItem interface{}
+}
+
+// newlru create a new least-recently-used cache for ither the verification caches
+// or the mining datasets.
+func newlru(what string, maxItems int, new func(epoch uint64) interface{}) *lru {
+	if maxItems <= 0 {
+		maxItems = 1
+	}
+	cache, _ := simplelru.NewLRU(maxItems, func(key, value interface{}) {
+		log.Trace("Evicted ethash "+what, "epoch", key)
+	})
+	return &lru{what: what, new: new, cache: cache}
+}
+
+// get retrieves or creates an item for the given epoch. The first return value is always
+// non-nil. The second return value is non-nil if lru thinks that an item will be useful in
+// the near future.
+func (lru *lru) get(epoch uint64) (item, future interface{}) {
+	lru.mu.Lock()
+	defer lru.mu.Unlock()
+
+	// Get or create the item for the requested epoch.
+	item, ok := lru.cache.Get(epoch)
+	if !ok {
+		if lru.future > 0 && lru.future == epoch {
+			item = lru.futureItem
+		} else {
+			log.Trace("Requiring new ethash "+lru.what, "epoch", epoch)
+			item = lru.new(epoch)
+		}
+		lru.cache.Add(epoch, item)
+	}
+	// Update the 'future item' if epoch is larger than previously seen.
+	if epoch < maxEpoch-1 && lru.future < epoch+1 {
+		log.Trace("Requiring new future ethash "+lru.what, "epoch", epoch+1)
+		future = lru.new(epoch + 1)
+		lru.future = epoch + 1
+		lru.futureItem = future
+	}
+	return item, future
+}
+
 // cache wraps an ethash cache with some metadata to allow easier concurrent use.
 type cache struct {
-	epoch uint64 // Epoch for which this cache is relevant
+	epoch uint64    // Epoch for which this cache is relevant
+	dump  *os.File  // File descriptor of the memory mapped cache
+	mmap  mmap.MMap // Memory map itself to unmap before releasing
+	cache []uint32  // The actual cache data content (may be memory mapped)
+	once  sync.Once // Ensures the cache is generated only once
+}
 
-	dump *os.File  // File descriptor of the memory mapped cache
-	mmap mmap.MMap // Memory map itself to unmap before releasing
-
-	cache []uint32   // The actual cache data content (may be memory mapped)
-	used  time.Time  // Timestamp of the last use for smarter eviction
-	once  sync.Once  // Ensures the cache is generated only once
-	lock  sync.Mutex // Ensures thread safety for updating the usage time
+// newCache creates a new ethash verification cache and returns it as a plain Go
+// interface to be usable in an LRU cache.
+func newCache(epoch uint64) interface{} {
+	return &cache{epoch: epoch}
 }
 
 // generate ensures that the cache content is generated before use.
 func (c *cache) generate(dir string, limit int, test bool) {
 	c.once.Do(func() {
-		// If we have a testing cache, generate and return
-		if test {
-			c.cache = make([]uint32, 1024/4)
-			generateCache(c.cache, c.epoch, seedHash(c.epoch*epochLength+1))
-			return
-		}
-		// If we don't store anything on disk, generate and return
 		size := cacheSize(c.epoch*epochLength + 1)
 		seed := seedHash(c.epoch*epochLength + 1)
-
+		if test {
+			size = 1024
+		}
+		// If we don't store anything on disk, generate and return.
 		if dir == "" {
 			c.cache = make([]uint32, size/4)
 			generateCache(c.cache, c.epoch, seed)
@@ -181,6 +233,10 @@ func (c *cache) generate(dir string, limit int, test bool) {
 		path := filepath.Join(dir, fmt.Sprintf("cache-R%d-%x%s", algorithmRevision, seed[:8], endian))
 		logger := log.New("epoch", c.epoch)
 
+		// We're about to mmap the file, ensure that the mapping is cleaned up when the
+		// cache becomes unused.
+		runtime.SetFinalizer(c, (*cache).finalizer)
+
 		// Try to load the file from disk and memory map it
 		var err error
 		c.dump, c.mmap, c.cache, err = memoryMap(path)
@@ -207,49 +263,41 @@ func (c *cache) generate(dir string, limit int, test bool) {
 	})
 }
 
-// release closes any file handlers and memory maps open.
-func (c *cache) release() {
+// finalizer unmaps the memory and closes the file.
+func (c *cache) finalizer() {
 	if c.mmap != nil {
 		c.mmap.Unmap()
-		c.mmap = nil
-	}
-	if c.dump != nil {
 		c.dump.Close()
-		c.dump = nil
+		c.mmap, c.dump = nil, nil
 	}
 }
 
 // dataset wraps an ethash dataset with some metadata to allow easier concurrent use.
 type dataset struct {
-	epoch uint64 // Epoch for which this cache is relevant
+	epoch   uint64    // Epoch for which this cache is relevant
+	dump    *os.File  // File descriptor of the memory mapped cache
+	mmap    mmap.MMap // Memory map itself to unmap before releasing
+	dataset []uint32  // The actual cache data content
+	once    sync.Once // Ensures the cache is generated only once
+}
 
-	dump *os.File  // File descriptor of the memory mapped cache
-	mmap mmap.MMap // Memory map itself to unmap before releasing
-
-	dataset []uint32   // The actual cache data content
-	used    time.Time  // Timestamp of the last use for smarter eviction
-	once    sync.Once  // Ensures the cache is generated only once
-	lock    sync.Mutex // Ensures thread safety for updating the usage time
+// newDataset creates a new ethash mining dataset and returns it as a plain Go
+// interface to be usable in an LRU cache.
+func newDataset(epoch uint64) interface{} {
+	return &dataset{epoch: epoch}
 }
 
 // generate ensures that the dataset content is generated before use.
 func (d *dataset) generate(dir string, limit int, test bool) {
 	d.once.Do(func() {
-		// If we have a testing dataset, generate and return
-		if test {
-			cache := make([]uint32, 1024/4)
-			generateCache(cache, d.epoch, seedHash(d.epoch*epochLength+1))
-
-			d.dataset = make([]uint32, 32*1024/4)
-			generateDataset(d.dataset, d.epoch, cache)
-
-			return
-		}
-		// If we don't store anything on disk, generate and return
 		csize := cacheSize(d.epoch*epochLength + 1)
 		dsize := datasetSize(d.epoch*epochLength + 1)
 		seed := seedHash(d.epoch*epochLength + 1)
-
+		if test {
+			csize = 1024
+			dsize = 32 * 1024
+		}
+		// If we don't store anything on disk, generate and return
 		if dir == "" {
 			cache := make([]uint32, csize/4)
 			generateCache(cache, d.epoch, seed)
@@ -265,6 +313,10 @@ func (d *dataset) generate(dir string, limit int, test bool) {
 		path := filepath.Join(dir, fmt.Sprintf("full-R%d-%x%s", algorithmRevision, seed[:8], endian))
 		logger := log.New("epoch", d.epoch)
 
+		// We're about to mmap the file, ensure that the mapping is cleaned up when the
+		// cache becomes unused.
+		runtime.SetFinalizer(d, (*dataset).finalizer)
+
 		// Try to load the file from disk and memory map it
 		var err error
 		d.dump, d.mmap, d.dataset, err = memoryMap(path)
@@ -294,15 +346,12 @@ func (d *dataset) generate(dir string, limit int, test bool) {
 	})
 }
 
-// release closes any file handlers and memory maps open.
-func (d *dataset) release() {
+// finalizer closes any file handlers and memory maps open.
+func (d *dataset) finalizer() {
 	if d.mmap != nil {
 		d.mmap.Unmap()
-		d.mmap = nil
-	}
-	if d.dump != nil {
 		d.dump.Close()
-		d.dump = nil
+		d.mmap, d.dump = nil, nil
 	}
 }
 
@@ -310,30 +359,43 @@ func (d *dataset) release() {
 func MakeCache(block uint64, dir string) {
 	c := cache{epoch: block / epochLength}
 	c.generate(dir, math.MaxInt32, false)
-	c.release()
 }
 
 // MakeDataset generates a new ethash dataset and optionally stores it to disk.
 func MakeDataset(block uint64, dir string) {
 	d := dataset{epoch: block / epochLength}
 	d.generate(dir, math.MaxInt32, false)
-	d.release()
+}
+
+// Mode defines the type and amount of PoW verification an ethash engine makes.
+type Mode uint
+
+const (
+	ModeNormal Mode = iota
+	ModeShared
+	ModeTest
+	ModeFake
+	ModeFullFake
+)
+
+// Config are the configuration parameters of the ethash.
+type Config struct {
+	CacheDir       string
+	CachesInMem    int
+	CachesOnDisk   int
+	DatasetDir     string
+	DatasetsInMem  int
+	DatasetsOnDisk int
+	PowMode        Mode
 }
 
 // Ethash is a consensus engine based on proot-of-work implementing the ethash
 // algorithm.
 type Ethash struct {
-	cachedir     string // Data directory to store the verification caches
-	cachesinmem  int    // Number of caches to keep in memory
-	cachesondisk int    // Number of caches to keep on disk
-	dagdir       string // Data directory to store full mining datasets
-	dagsinmem    int    // Number of mining datasets to keep in memory
-	dagsondisk   int    // Number of mining datasets to keep on disk
+	config Config
 
-	caches   map[uint64]*cache   // In memory caches to avoid regenerating too often
-	fcache   *cache              // Pre-generated cache for the estimated future epoch
-	datasets map[uint64]*dataset // In memory datasets to avoid regenerating too often
-	fdataset *dataset            // Pre-generated dataset for the estimated future epoch
+	caches   *lru // In memory caches to avoid regenerating too often
+	datasets *lru // In memory datasets to avoid regenerating too often
 
 	// Mining related fields
 	rand     *rand.Rand    // Properly seeded random source for nonces
@@ -342,10 +404,7 @@ type Ethash struct {
 	hashrate metrics.Meter // Meter tracking the average hashrate
 
 	// The fields below are hooks for testing
-	tester    bool          // Flag whether to use a smaller test dataset
 	shared    *Ethash       // Shared PoW verifier to avoid cache regeneration
-	fakeMode  bool          // Flag whether to disable PoW checking
-	fakeFull  bool          // Flag whether to disable all consensus rules
 	fakeFail  uint64        // Block number which fails PoW check even in fake mode
 	fakeDelay time.Duration // Time delay to sleep for before returning from verify
 
@@ -353,69 +412,75 @@ type Ethash struct {
 }
 
 // New creates a full sized ethash PoW scheme.
-func New(cachedir string, cachesinmem, cachesondisk int, dagdir string, dagsinmem, dagsondisk int) *Ethash {
-	if cachesinmem <= 0 {
-		log.Warn("One ethash cache must always be in memory", "requested", cachesinmem)
-		cachesinmem = 1
+func New(config Config) *Ethash {
+	if config.CachesInMem <= 0 {
+		log.Warn("One ethash cache must always be in memory", "requested", config.CachesInMem)
+		config.CachesInMem = 1
 	}
-	if cachedir != "" && cachesondisk > 0 {
-		log.Info("Disk storage enabled for ethash caches", "dir", cachedir, "count", cachesondisk)
+	if config.CacheDir != "" && config.CachesOnDisk > 0 {
+		log.Info("Disk storage enabled for ethash caches", "dir", config.CacheDir, "count", config.CachesOnDisk)
 	}
-	if dagdir != "" && dagsondisk > 0 {
-		log.Info("Disk storage enabled for ethash DAGs", "dir", dagdir, "count", dagsondisk)
+	if config.DatasetDir != "" && config.DatasetsOnDisk > 0 {
+		log.Info("Disk storage enabled for ethash DAGs", "dir", config.DatasetDir, "count", config.DatasetsOnDisk)
 	}
 	return &Ethash{
-		cachedir:     cachedir,
-		cachesinmem:  cachesinmem,
-		cachesondisk: cachesondisk,
-		dagdir:       dagdir,
-		dagsinmem:    dagsinmem,
-		dagsondisk:   dagsondisk,
-		caches:       make(map[uint64]*cache),
-		datasets:     make(map[uint64]*dataset),
-		update:       make(chan struct{}),
-		hashrate:     metrics.NewMeter(),
+		config:   config,
+		caches:   newlru("cache", config.CachesInMem, newCache),
+		datasets: newlru("dataset", config.DatasetsInMem, newDataset),
+		update:   make(chan struct{}),
+		hashrate: metrics.NewMeter(),
 	}
 }
 
 // NewTester creates a small sized ethash PoW scheme useful only for testing
 // purposes.
 func NewTester() *Ethash {
-	return &Ethash{
-		cachesinmem: 1,
-		caches:      make(map[uint64]*cache),
-		datasets:    make(map[uint64]*dataset),
-		tester:      true,
-		update:      make(chan struct{}),
-		hashrate:    metrics.NewMeter(),
-	}
+	return New(Config{CachesInMem: 1, PowMode: ModeTest})
 }
 
 // NewFaker creates a ethash consensus engine with a fake PoW scheme that accepts
 // all blocks' seal as valid, though they still have to conform to the Ethereum
 // consensus rules.
 func NewFaker() *Ethash {
-	return &Ethash{fakeMode: true}
+	return &Ethash{
+		config: Config{
+			PowMode: ModeFake,
+		},
+	}
 }
 
 // NewFakeFailer creates a ethash consensus engine with a fake PoW scheme that
 // accepts all blocks as valid apart from the single one specified, though they
 // still have to conform to the Ethereum consensus rules.
 func NewFakeFailer(fail uint64) *Ethash {
-	return &Ethash{fakeMode: true, fakeFail: fail}
+	return &Ethash{
+		config: Config{
+			PowMode: ModeFake,
+		},
+		fakeFail: fail,
+	}
 }
 
 // NewFakeDelayer creates a ethash consensus engine with a fake PoW scheme that
 // accepts all blocks as valid, but delays verifications by some time, though
 // they still have to conform to the Ethereum consensus rules.
 func NewFakeDelayer(delay time.Duration) *Ethash {
-	return &Ethash{fakeMode: true, fakeDelay: delay}
+	return &Ethash{
+		config: Config{
+			PowMode: ModeFake,
+		},
+		fakeDelay: delay,
+	}
 }
 
 // NewFullFaker creates an ethash consensus engine with a full fake scheme that
 // accepts all blocks as valid, without checking any consensus rules whatsoever.
 func NewFullFaker() *Ethash {
-	return &Ethash{fakeMode: true, fakeFull: true}
+	return &Ethash{
+		config: Config{
+			PowMode: ModeFullFake,
+		},
+	}
 }
 
 // NewShared creates a full sized ethash PoW shared between all requesters running
@@ -427,126 +492,40 @@ func NewShared() *Ethash {
 // cache tries to retrieve a verification cache for the specified block number
 // by first checking against a list of in-memory caches, then against caches
 // stored on disk, and finally generating one if none can be found.
-func (ethash *Ethash) cache(block uint64) []uint32 {
+func (ethash *Ethash) cache(block uint64) *cache {
 	epoch := block / epochLength
+	currentI, futureI := ethash.caches.get(epoch)
+	current := currentI.(*cache)
 
-	// If we have a PoW for that epoch, use that
-	ethash.lock.Lock()
+	// Wait for generation finish.
+	current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
 
-	current, future := ethash.caches[epoch], (*cache)(nil)
-	if current == nil {
-		// No in-memory cache, evict the oldest if the cache limit was reached
-		for len(ethash.caches) > 0 && len(ethash.caches) >= ethash.cachesinmem {
-			var evict *cache
-			for _, cache := range ethash.caches {
-				if evict == nil || evict.used.After(cache.used) {
-					evict = cache
-				}
-			}
-			delete(ethash.caches, evict.epoch)
-			evict.release()
-
-			log.Trace("Evicted ethash cache", "epoch", evict.epoch, "used", evict.used)
-		}
-		// If we have the new cache pre-generated, use that, otherwise create a new one
-		if ethash.fcache != nil && ethash.fcache.epoch == epoch {
-			log.Trace("Using pre-generated cache", "epoch", epoch)
-			current, ethash.fcache = ethash.fcache, nil
-		} else {
-			log.Trace("Requiring new ethash cache", "epoch", epoch)
-			current = &cache{epoch: epoch}
-		}
-		ethash.caches[epoch] = current
-
-		// If we just used up the future cache, or need a refresh, regenerate
-		if ethash.fcache == nil || ethash.fcache.epoch <= epoch {
-			if ethash.fcache != nil {
-				ethash.fcache.release()
-			}
-			log.Trace("Requiring new future ethash cache", "epoch", epoch+1)
-			future = &cache{epoch: epoch + 1}
-			ethash.fcache = future
-		}
-		// New current cache, set its initial timestamp
-		current.used = time.Now()
+	// If we need a new future cache, now's a good time to regenerate it.
+	if futureI != nil {
+		future := futureI.(*cache)
+		go future.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
 	}
-	ethash.lock.Unlock()
-
-	// Wait for generation finish, bump the timestamp and finalize the cache
-	current.generate(ethash.cachedir, ethash.cachesondisk, ethash.tester)
-
-	current.lock.Lock()
-	current.used = time.Now()
-	current.lock.Unlock()
-
-	// If we exhausted the future cache, now's a good time to regenerate it
-	if future != nil {
-		go future.generate(ethash.cachedir, ethash.cachesondisk, ethash.tester)
-	}
-	return current.cache
+	return current
 }
 
 // dataset tries to retrieve a mining dataset for the specified block number
 // by first checking against a list of in-memory datasets, then against DAGs
 // stored on disk, and finally generating one if none can be found.
-func (ethash *Ethash) dataset(block uint64) []uint32 {
+func (ethash *Ethash) dataset(block uint64) *dataset {
 	epoch := block / epochLength
+	currentI, futureI := ethash.datasets.get(epoch)
+	current := currentI.(*dataset)
 
-	// If we have a PoW for that epoch, use that
-	ethash.lock.Lock()
+	// Wait for generation finish.
+	current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
 
-	current, future := ethash.datasets[epoch], (*dataset)(nil)
-	if current == nil {
-		// No in-memory dataset, evict the oldest if the dataset limit was reached
-		for len(ethash.datasets) > 0 && len(ethash.datasets) >= ethash.dagsinmem {
-			var evict *dataset
-			for _, dataset := range ethash.datasets {
-				if evict == nil || evict.used.After(dataset.used) {
-					evict = dataset
-				}
-			}
-			delete(ethash.datasets, evict.epoch)
-			evict.release()
-
-			log.Trace("Evicted ethash dataset", "epoch", evict.epoch, "used", evict.used)
-		}
-		// If we have the new cache pre-generated, use that, otherwise create a new one
-		if ethash.fdataset != nil && ethash.fdataset.epoch == epoch {
-			log.Trace("Using pre-generated dataset", "epoch", epoch)
-			current = &dataset{epoch: ethash.fdataset.epoch} // Reload from disk
-			ethash.fdataset = nil
-		} else {
-			log.Trace("Requiring new ethash dataset", "epoch", epoch)
-			current = &dataset{epoch: epoch}
-		}
-		ethash.datasets[epoch] = current
-
-		// If we just used up the future dataset, or need a refresh, regenerate
-		if ethash.fdataset == nil || ethash.fdataset.epoch <= epoch {
-			if ethash.fdataset != nil {
-				ethash.fdataset.release()
-			}
-			log.Trace("Requiring new future ethash dataset", "epoch", epoch+1)
-			future = &dataset{epoch: epoch + 1}
-			ethash.fdataset = future
-		}
-		// New current dataset, set its initial timestamp
-		current.used = time.Now()
+	// If we need a new future dataset, now's a good time to regenerate it.
+	if futureI != nil {
+		future := futureI.(*dataset)
+		go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
 	}
-	ethash.lock.Unlock()
 
-	// Wait for generation finish, bump the timestamp and finalize the cache
-	current.generate(ethash.dagdir, ethash.dagsondisk, ethash.tester)
-
-	current.lock.Lock()
-	current.used = time.Now()
-	current.lock.Unlock()
-
-	// If we exhausted the future dataset, now's a good time to regenerate it
-	if future != nil {
-		go future.generate(ethash.dagdir, ethash.dagsondisk, ethash.tester)
-	}
-	return current.dataset
+	return current
 }
 
 // Threads returns the number of mining threads currently enabled. This doesn't

vendor/github.com/ethereum/go-ethereum/consensus/ethash/ethash_test.go

@@ -17,7 +17,11 @@
 package ethash
 
 import (
+	"io/ioutil"
 	"math/big"
+	"math/rand"
+	"os"
+	"sync"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/core/types"
@@ -38,3 +42,38 @@ func TestTestMode(t *testing.T) {
 		t.Fatalf("unexpected verification error: %v", err)
 	}
 }
+
+// This test checks that cache lru logic doesn't crash under load.
+// It reproduces https://github.com/ethereum/go-ethereum/issues/14943
+func TestCacheFileEvict(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "ethash-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+	e := New(Config{CachesInMem: 3, CachesOnDisk: 10, CacheDir: tmpdir, PowMode: ModeTest})
+
+	workers := 8
+	epochs := 100
+	var wg sync.WaitGroup
+	wg.Add(workers)
+	for i := 0; i < workers; i++ {
+		go verifyTest(&wg, e, i, epochs)
+	}
+	wg.Wait()
+}
+
+func verifyTest(wg *sync.WaitGroup, e *Ethash, workerIndex, epochs int) {
+	defer wg.Done()
+
+	const wiggle = 4 * epochLength
+	r := rand.New(rand.NewSource(int64(workerIndex)))
+	for epoch := 0; epoch < epochs; epoch++ {
+		block := int64(epoch)*epochLength - wiggle/2 + r.Int63n(wiggle)
+		if block < 0 {
+			block = 0
+		}
+		head := &types.Header{Number: big.NewInt(block), Difficulty: big.NewInt(100)}
+		e.VerifySeal(nil, head)
+	}
+}

vendor/github.com/ethereum/go-ethereum/consensus/ethash/sealer.go

@@ -34,7 +34,7 @@ import (
 // the block's difficulty requirements.
 func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
 	// If we're running a fake PoW, simply return a 0 nonce immediately
-	if ethash.fakeMode {
+	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
 		header := block.Header()
 		header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
 		return block.WithSeal(header), nil
@@ -97,10 +97,9 @@ func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, stop
 func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan struct{}, found chan *types.Block) {
 	// Extract some data from the header
 	var (
-		header = block.Header()
-		hash   = header.HashNoNonce().Bytes()
-		target = new(big.Int).Div(maxUint256, header.Difficulty)
-
+		header  = block.Header()
+		hash    = header.HashNoNonce().Bytes()
+		target  = new(big.Int).Div(maxUint256, header.Difficulty)
 		number  = header.Number.Uint64()
 		dataset = ethash.dataset(number)
 	)
@@ -111,13 +110,14 @@ func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan s
 	)
 	logger := log.New("miner", id)
 	logger.Trace("Started ethash search for new nonces", "seed", seed)
+search:
 	for {
 		select {
 		case <-abort:
 			// Mining terminated, update stats and abort
 			logger.Trace("Ethash nonce search aborted", "attempts", nonce-seed)
 			ethash.hashrate.Mark(attempts)
-			return
+			break search
 
 		default:
 			// We don't have to update hash rate on every nonce, so update after after 2^X nonces
@@ -127,7 +127,7 @@ func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan s
 				attempts = 0
 			}
 			// Compute the PoW value of this nonce
-			digest, result := hashimotoFull(dataset, hash, nonce)
+			digest, result := hashimotoFull(dataset.dataset, hash, nonce)
 			if new(big.Int).SetBytes(result).Cmp(target) <= 0 {
 				// Correct nonce found, create a new header with it
 				header = types.CopyHeader(header)
@@ -141,9 +141,12 @@ func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan s
 				case <-abort:
 					logger.Trace("Ethash nonce found but discarded", "attempts", nonce-seed, "nonce", nonce)
 				}
-				return
+				break search
 			}
 			nonce++
 		}
 	}
+	// Datasets are unmapped in a finalizer. Ensure that the dataset stays live
+	// during sealing so it's not unmapped while being read.
+	runtime.KeepAlive(dataset)
 }