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// 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 implements the ethash proof-of-work consensus engine.
package ethash
import (
"errors"
"fmt"
"math"
"math/big"
"math/rand"
"os"
"path/filepath"
"reflect"
"runtime"
"strconv"
"sync"
"sync/atomic"
"time"
"unsafe"
mmap "github.com/edsrzf/mmap-go"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/metrics"
"github.com/ethereum/go-ethereum/rpc"
"github.com/hashicorp/golang-lru/simplelru"
)
var ErrInvalidDumpMagic = errors.New("invalid dump magic")
var (
// two256 is a big integer representing 2^256
two256 = 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(Config{"", 3, 0, "", 1, 0, ModeNormal}, nil, false)
// algorithmRevision is the data structure version used for file naming.
algorithmRevision = 23
// dumpMagic is a dataset dump header to sanity check a data dump.
dumpMagic = []uint32{0xbaddcafe, 0xfee1dead}
)
// isLittleEndian returns whether the local system is running in little or big
// endian byte order.
func isLittleEndian() bool {
n := uint32(0x01020304)
return *(*byte)(unsafe.Pointer(&n)) == 0x04
}
// memoryMap tries to memory map a file of uint32s for read only access.
func memoryMap(path string) (*os.File, mmap.MMap, []uint32, error) {
file, err := os.OpenFile(path, os.O_RDONLY, 0644)
if err != nil {
return nil, nil, nil, err
}
mem, buffer, err := memoryMapFile(file, false)
if err != nil {
file.Close()
return nil, nil, nil, err
}
for i, magic := range dumpMagic {
if buffer[i] != magic {
mem.Unmap()
file.Close()
return nil, nil, nil, ErrInvalidDumpMagic
}
}
return file, mem, buffer[len(dumpMagic):], err
}
// memoryMapFile tries to memory map an already opened file descriptor.
func memoryMapFile(file *os.File, write bool) (mmap.MMap, []uint32, error) {
// Try to memory map the file
flag := mmap.RDONLY
if write {
flag = mmap.RDWR
}
mem, err := mmap.Map(file, flag, 0)
if err != nil {
return nil, nil, err
}
// Yay, we managed to memory map the file, here be dragons
header := *(*reflect.SliceHeader)(unsafe.Pointer(&mem))
header.Len /= 4
header.Cap /= 4
return mem, *(*[]uint32)(unsafe.Pointer(&header)), nil
}
// memoryMapAndGenerate tries to memory map a temporary file of uint32s for write
// access, fill it with the data from a generator and then move it into the final
// path requested.
func memoryMapAndGenerate(path string, size uint64, generator func(buffer []uint32)) (*os.File, mmap.MMap, []uint32, error) {
// Ensure the data folder exists
if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
return nil, nil, nil, err
}
// Create a huge temporary empty file to fill with data
temp := path + "." + strconv.Itoa(rand.Int())
dump, err := os.Create(temp)
if err != nil {
return nil, nil, nil, err
}
if err = dump.Truncate(int64(len(dumpMagic))*4 + int64(size)); err != nil {
return nil, nil, nil, err
}
// Memory map the file for writing and fill it with the generator
mem, buffer, err := memoryMapFile(dump, true)
if err != nil {
dump.Close()
return nil, nil, nil, err
}
copy(buffer, dumpMagic)
data := buffer[len(dumpMagic):]
generator(data)
if err := mem.Unmap(); err != nil {
return nil, nil, nil, err
}
if err := dump.Close(); err != nil {
return nil, nil, nil, err
}
if err := os.Rename(temp, path); err != nil {
return nil, nil, nil, err
}
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 either 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
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
}
// 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() {
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)
return
}
// Disk storage is needed, this will get fancy
var endian string
if !isLittleEndian() {
endian = ".be"
}
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)
if err == nil {
logger.Debug("Loaded old ethash cache from disk")
return
}
logger.Debug("Failed to load old ethash cache", "err", err)
// No previous cache available, create a new cache file to fill
c.dump, c.mmap, c.cache, err = memoryMapAndGenerate(path, size, func(buffer []uint32) { generateCache(buffer, c.epoch, seed) })
if err != nil {
logger.Error("Failed to generate mapped ethash cache", "err", err)
c.cache = make([]uint32, size/4)
generateCache(c.cache, c.epoch, seed)
}
// Iterate over all previous instances and delete old ones
for ep := int(c.epoch) - limit; ep >= 0; ep-- {
seed := seedHash(uint64(ep)*epochLength + 1)
path := filepath.Join(dir, fmt.Sprintf("cache-R%d-%x%s", algorithmRevision, seed[:8], endian))
os.Remove(path)
}
})
}
// finalizer unmaps the memory and closes the file.
func (c *cache) finalizer() {
if c.mmap != nil {
c.mmap.Unmap()
c.dump.Close()
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
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
done uint32 // Atomic flag to determine generation status
}
// 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() {
// Mark the dataset generated after we're done. This is needed for remote
defer atomic.StoreUint32(&d.done, 1)
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)
d.dataset = make([]uint32, dsize/4)
generateDataset(d.dataset, d.epoch, cache)
return
}
// Disk storage is needed, this will get fancy
var endian string
if !isLittleEndian() {
endian = ".be"
}
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)
if err == nil {
logger.Debug("Loaded old ethash dataset from disk")
return
}
logger.Debug("Failed to load old ethash dataset", "err", err)
// No previous dataset available, create a new dataset file to fill
cache := make([]uint32, csize/4)
generateCache(cache, d.epoch, seed)
d.dump, d.mmap, d.dataset, err = memoryMapAndGenerate(path, dsize, func(buffer []uint32) { generateDataset(buffer, d.epoch, cache) })
if err != nil {
logger.Error("Failed to generate mapped ethash dataset", "err", err)
d.dataset = make([]uint32, dsize/2)
generateDataset(d.dataset, d.epoch, cache)
}
// Iterate over all previous instances and delete old ones
for ep := int(d.epoch) - limit; ep >= 0; ep-- {
seed := seedHash(uint64(ep)*epochLength + 1)
path := filepath.Join(dir, fmt.Sprintf("full-R%d-%x%s", algorithmRevision, seed[:8], endian))
os.Remove(path)
}
})
}
// generated returns whether this particular dataset finished generating already
// or not (it may not have been started at all). This is useful for remote miners
// to default to verification caches instead of blocking on DAG generations.
func (d *dataset) generated() bool {
return atomic.LoadUint32(&d.done) == 1
}
// finalizer closes any file handlers and memory maps open.
func (d *dataset) finalizer() {
if d.mmap != nil {
d.mmap.Unmap()
d.dump.Close()
d.mmap, d.dump = nil, nil
}
}
// MakeCache generates a new ethash cache and optionally stores it to disk.
func MakeCache(block uint64, dir string) {
c := cache{epoch: block / epochLength}
c.generate(dir, math.MaxInt32, false)
}
// 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)
}
// 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
}
// sealTask wraps a seal block with relative result channel for remote sealer thread.
type sealTask struct {
block *types.Block
results chan<- *types.Block
}
// mineResult wraps the pow solution parameters for the specified block.
type mineResult struct {
nonce types.BlockNonce
mixDigest common.Hash
hash common.Hash
errc chan error
}
// hashrate wraps the hash rate submitted by the remote sealer.
type hashrate struct {
id common.Hash
ping time.Time
rate uint64
done chan struct{}
}
// sealWork wraps a seal work package for remote sealer.
type sealWork struct {
errc chan error
res chan [4]string
}
// Ethash is a consensus engine based on proof-of-work implementing the ethash
// algorithm.
type Ethash struct {
config Config
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
threads int // Number of threads to mine on if mining
update chan struct{} // Notification channel to update mining parameters
hashrate metrics.Meter // Meter tracking the average hashrate
// Remote sealer related fields
workCh chan *sealTask // Notification channel to push new work and relative result channel to remote sealer
fetchWorkCh chan *sealWork // Channel used for remote sealer to fetch mining work
submitWorkCh chan *mineResult // Channel used for remote sealer to submit their mining result
fetchRateCh chan chan uint64 // Channel used to gather submitted hash rate for local or remote sealer.
submitRateCh chan *hashrate // Channel used for remote sealer to submit their mining hashrate
// The fields below are hooks for testing
shared *Ethash // Shared PoW verifier to avoid cache regeneration
fakeFail uint64 // Block number which fails PoW check even in fake mode
fakeDelay time.Duration // Time delay to sleep for before returning from verify
lock sync.Mutex // Ensures thread safety for the in-memory caches and mining fields
closeOnce sync.Once // Ensures exit channel will not be closed twice.
exitCh chan chan error // Notification channel to exiting backend threads
}
// New creates a full sized ethash PoW scheme and starts a background thread for
// remote mining, also optionally notifying a batch of remote services of new work
// packages.
func New(config Config, notify []string, noverify bool) *Ethash {
if config.CachesInMem <= 0 {
log.Warn("One ethash cache must always be in memory", "requested", config.CachesInMem)
config.CachesInMem = 1
}
if config.CacheDir != "" && config.CachesOnDisk > 0 {
log.Info("Disk storage enabled for ethash caches", "dir", config.CacheDir, "count", config.CachesOnDisk)
}
if config.DatasetDir != "" && config.DatasetsOnDisk > 0 {
log.Info("Disk storage enabled for ethash DAGs", "dir", config.DatasetDir, "count", config.DatasetsOnDisk)
}
ethash := &Ethash{
config: config,
caches: newlru("cache", config.CachesInMem, newCache),
datasets: newlru("dataset", config.DatasetsInMem, newDataset),
update: make(chan struct{}),
hashrate: metrics.NewMeterForced(),
workCh: make(chan *sealTask),
fetchWorkCh: make(chan *sealWork),
submitWorkCh: make(chan *mineResult),
fetchRateCh: make(chan chan uint64),
submitRateCh: make(chan *hashrate),
exitCh: make(chan chan error),
}
go ethash.remote(notify, noverify)
return ethash
}
// NewTester creates a small sized ethash PoW scheme useful only for testing
// purposes.
func NewTester(notify []string, noverify bool) *Ethash {
ethash := &Ethash{
config: Config{PowMode: ModeTest},
caches: newlru("cache", 1, newCache),
datasets: newlru("dataset", 1, newDataset),
update: make(chan struct{}),
hashrate: metrics.NewMeterForced(),
workCh: make(chan *sealTask),
fetchWorkCh: make(chan *sealWork),
submitWorkCh: make(chan *mineResult),
fetchRateCh: make(chan chan uint64),
submitRateCh: make(chan *hashrate),
exitCh: make(chan chan error),
}
go ethash.remote(notify, noverify)
return ethash
}
// 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{
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{
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{
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{
config: Config{
PowMode: ModeFullFake,
},
}
}
// NewShared creates a full sized ethash PoW shared between all requesters running
// in the same process.
func NewShared() *Ethash {
return &Ethash{shared: sharedEthash}
}
// Close closes the exit channel to notify all backend threads exiting.
func (ethash *Ethash) Close() error {
var err error
ethash.closeOnce.Do(func() {
// Short circuit if the exit channel is not allocated.
if ethash.exitCh == nil {
return
}
errc := make(chan error)
ethash.exitCh <- errc
err = <-errc
close(ethash.exitCh)
})
return err
}
// 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) *cache {
epoch := block / epochLength
currentI, futureI := ethash.caches.get(epoch)
current := currentI.(*cache)
// Wait for generation finish.
current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
// 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)
}
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.
//
// If async is specified, not only the future but the current DAG is also
// generates on a background thread.
func (ethash *Ethash) dataset(block uint64, async bool) *dataset {
// Retrieve the requested ethash dataset
epoch := block / epochLength
currentI, futureI := ethash.datasets.get(epoch)
current := currentI.(*dataset)
// If async is specified, generate everything in a background thread
if async && !current.generated() {
go func() {
current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
if futureI != nil {
future := futureI.(*dataset)
future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
}
}()
} else {
// Either blocking generation was requested, or already done
current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
if futureI != nil {
future := futureI.(*dataset)
go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
}
}
return current
}
// Threads returns the number of mining threads currently enabled. This doesn't
// necessarily mean that mining is running!
func (ethash *Ethash) Threads() int {
ethash.lock.Lock()
defer ethash.lock.Unlock()
return ethash.threads
}
// SetThreads updates the number of mining threads currently enabled. Calling
// this method does not start mining, only sets the thread count. If zero is
// specified, the miner will use all cores of the machine. Setting a thread
// count below zero is allowed and will cause the miner to idle, without any
// work being done.
func (ethash *Ethash) SetThreads(threads int) {
ethash.lock.Lock()
defer ethash.lock.Unlock()
// If we're running a shared PoW, set the thread count on that instead
if ethash.shared != nil {
ethash.shared.SetThreads(threads)
return
}
// Update the threads and ping any running seal to pull in any changes
ethash.threads = threads
select {
case ethash.update <- struct{}{}:
default:
}
}
// Hashrate implements PoW, returning the measured rate of the search invocations
// per second over the last minute.
// Note the returned hashrate includes local hashrate, but also includes the total
// hashrate of all remote miner.
func (ethash *Ethash) Hashrate() float64 {
// Short circuit if we are run the ethash in normal/test mode.
if ethash.config.PowMode != ModeNormal && ethash.config.PowMode != ModeTest {
return ethash.hashrate.Rate1()
}
var res = make(chan uint64, 1)
select {
case ethash.fetchRateCh <- res:
case <-ethash.exitCh:
// Return local hashrate only if ethash is stopped.
return ethash.hashrate.Rate1()
}
// Gather total submitted hash rate of remote sealers.
return ethash.hashrate.Rate1() + float64(<-res)
}
// APIs implements consensus.Engine, returning the user facing RPC APIs.
func (ethash *Ethash) APIs(chain consensus.ChainReader) []rpc.API {
// In order to ensure backward compatibility, we exposes ethash RPC APIs
// to both eth and ethash namespaces.
return []rpc.API{
{
Namespace: "eth",
Version: "1.0",
Service: &API{ethash},
Public: true,
},
{
Namespace: "ethash",
Version: "1.0",
Service: &API{ethash},
Public: true,
},
}
}
// SeedHash is the seed to use for generating a verification cache and the mining
// dataset.
func SeedHash(block uint64) []byte {
return seedHash(block)
}
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