442 lines
13 KiB
Go
442 lines
13 KiB
Go
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// Copyright 2015 The go-ethereum Authors
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// Copyright 2015 Lefteris Karapetsas <lefteris@refu.co>
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// Copyright 2015 Matthew Wampler-Doty <matthew.wampler.doty@gmail.com>
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package ethash
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/*
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#include "src/libethash/internal.h"
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int ethashGoCallback_cgo(unsigned);
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*/
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import "C"
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import (
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"errors"
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"fmt"
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"io/ioutil"
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"math/big"
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"math/rand"
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"os"
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"os/user"
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"path/filepath"
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"runtime"
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"sync"
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"sync/atomic"
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"time"
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"unsafe"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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"github.com/ethereum/go-ethereum/pow"
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)
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var (
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maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
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sharedLight = new(Light)
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)
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const (
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epochLength uint64 = 30000
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cacheSizeForTesting C.uint64_t = 1024
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dagSizeForTesting C.uint64_t = 1024 * 32
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)
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var DefaultDir = defaultDir()
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func defaultDir() string {
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home := os.Getenv("HOME")
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if user, err := user.Current(); err == nil {
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home = user.HomeDir
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}
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if runtime.GOOS == "windows" {
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return filepath.Join(home, "AppData", "Ethash")
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}
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return filepath.Join(home, ".ethash")
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}
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// cache wraps an ethash_light_t with some metadata
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// and automatic memory management.
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type cache struct {
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epoch uint64
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used time.Time
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test bool
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gen sync.Once // ensures cache is only generated once.
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ptr *C.struct_ethash_light
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}
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// generate creates the actual cache. it can be called from multiple
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// goroutines. the first call will generate the cache, subsequent
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// calls wait until it is generated.
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func (cache *cache) generate() {
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cache.gen.Do(func() {
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started := time.Now()
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seedHash := makeSeedHash(cache.epoch)
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glog.V(logger.Debug).Infof("Generating cache for epoch %d (%x)", cache.epoch, seedHash)
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size := C.ethash_get_cachesize(C.uint64_t(cache.epoch * epochLength))
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if cache.test {
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size = cacheSizeForTesting
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}
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cache.ptr = C.ethash_light_new_internal(size, (*C.ethash_h256_t)(unsafe.Pointer(&seedHash[0])))
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runtime.SetFinalizer(cache, freeCache)
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glog.V(logger.Debug).Infof("Done generating cache for epoch %d, it took %v", cache.epoch, time.Since(started))
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})
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}
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func freeCache(cache *cache) {
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C.ethash_light_delete(cache.ptr)
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cache.ptr = nil
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}
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func (cache *cache) compute(dagSize uint64, hash common.Hash, nonce uint64) (ok bool, mixDigest, result common.Hash) {
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ret := C.ethash_light_compute_internal(cache.ptr, C.uint64_t(dagSize), hashToH256(hash), C.uint64_t(nonce))
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// Make sure cache is live until after the C call.
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// This is important because a GC might happen and execute
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// the finalizer before the call completes.
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_ = cache
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return bool(ret.success), h256ToHash(ret.mix_hash), h256ToHash(ret.result)
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}
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// Light implements the Verify half of the proof of work. It uses a few small
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// in-memory caches to verify the nonces found by Full.
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type Light struct {
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test bool // If set, use a smaller cache size
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mu sync.Mutex // Protects the per-epoch map of verification caches
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caches map[uint64]*cache // Currently maintained verification caches
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future *cache // Pre-generated cache for the estimated future DAG
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NumCaches int // Maximum number of caches to keep before eviction (only init, don't modify)
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}
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// Verify checks whether the block's nonce is valid.
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func (l *Light) Verify(block pow.Block) bool {
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// TODO: do ethash_quick_verify before getCache in order
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// to prevent DOS attacks.
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blockNum := block.NumberU64()
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if blockNum >= epochLength*2048 {
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glog.V(logger.Debug).Infof("block number %d too high, limit is %d", epochLength*2048)
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return false
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}
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difficulty := block.Difficulty()
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/* Cannot happen if block header diff is validated prior to PoW, but can
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happen if PoW is checked first due to parallel PoW checking.
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We could check the minimum valid difficulty but for SoC we avoid (duplicating)
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Ethereum protocol consensus rules here which are not in scope of Ethash
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*/
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if difficulty.Cmp(common.Big0) == 0 {
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glog.V(logger.Debug).Infof("invalid block difficulty")
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return false
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}
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cache := l.getCache(blockNum)
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dagSize := C.ethash_get_datasize(C.uint64_t(blockNum))
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if l.test {
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dagSize = dagSizeForTesting
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}
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// Recompute the hash using the cache.
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ok, mixDigest, result := cache.compute(uint64(dagSize), block.HashNoNonce(), block.Nonce())
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if !ok {
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return false
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}
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// avoid mixdigest malleability as it's not included in a block's "hashNononce"
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if block.MixDigest() != mixDigest {
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return false
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}
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// The actual check.
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target := new(big.Int).Div(maxUint256, difficulty)
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return result.Big().Cmp(target) <= 0
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}
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func h256ToHash(in C.ethash_h256_t) common.Hash {
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return *(*common.Hash)(unsafe.Pointer(&in.b))
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}
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func hashToH256(in common.Hash) C.ethash_h256_t {
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return C.ethash_h256_t{b: *(*[32]C.uint8_t)(unsafe.Pointer(&in[0]))}
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}
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func (l *Light) getCache(blockNum uint64) *cache {
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var c *cache
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epoch := blockNum / epochLength
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// If we have a PoW for that epoch, use that
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l.mu.Lock()
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if l.caches == nil {
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l.caches = make(map[uint64]*cache)
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}
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if l.NumCaches == 0 {
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l.NumCaches = 3
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}
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c = l.caches[epoch]
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if c == nil {
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// No cached DAG, evict the oldest if the cache limit was reached
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if len(l.caches) >= l.NumCaches {
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var evict *cache
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for _, cache := range l.caches {
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if evict == nil || evict.used.After(cache.used) {
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evict = cache
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}
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}
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glog.V(logger.Debug).Infof("Evicting DAG for epoch %d in favour of epoch %d", evict.epoch, epoch)
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delete(l.caches, evict.epoch)
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}
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// If we have the new DAG pre-generated, use that, otherwise create a new one
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if l.future != nil && l.future.epoch == epoch {
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glog.V(logger.Debug).Infof("Using pre-generated DAG for epoch %d", epoch)
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c, l.future = l.future, nil
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} else {
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glog.V(logger.Debug).Infof("No pre-generated DAG available, creating new for epoch %d", epoch)
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c = &cache{epoch: epoch, test: l.test}
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}
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l.caches[epoch] = c
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// If we just used up the future cache, or need a refresh, regenerate
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if l.future == nil || l.future.epoch <= epoch {
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glog.V(logger.Debug).Infof("Pre-generating DAG for epoch %d", epoch+1)
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l.future = &cache{epoch: epoch + 1, test: l.test}
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go l.future.generate()
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}
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}
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c.used = time.Now()
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l.mu.Unlock()
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// Wait for generation finish and return the cache
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c.generate()
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return c
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}
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// dag wraps an ethash_full_t with some metadata
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// and automatic memory management.
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type dag struct {
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epoch uint64
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test bool
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dir string
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gen sync.Once // ensures DAG is only generated once.
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ptr *C.struct_ethash_full
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}
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// generate creates the actual DAG. it can be called from multiple
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// goroutines. the first call will generate the DAG, subsequent
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// calls wait until it is generated.
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func (d *dag) generate() {
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d.gen.Do(func() {
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var (
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started = time.Now()
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seedHash = makeSeedHash(d.epoch)
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blockNum = C.uint64_t(d.epoch * epochLength)
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cacheSize = C.ethash_get_cachesize(blockNum)
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dagSize = C.ethash_get_datasize(blockNum)
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)
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if d.test {
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cacheSize = cacheSizeForTesting
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dagSize = dagSizeForTesting
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}
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if d.dir == "" {
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d.dir = DefaultDir
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}
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glog.V(logger.Info).Infof("Generating DAG for epoch %d (size %d) (%x)", d.epoch, dagSize, seedHash)
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// Generate a temporary cache.
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// TODO: this could share the cache with Light
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cache := C.ethash_light_new_internal(cacheSize, (*C.ethash_h256_t)(unsafe.Pointer(&seedHash[0])))
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defer C.ethash_light_delete(cache)
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// Generate the actual DAG.
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d.ptr = C.ethash_full_new_internal(
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C.CString(d.dir),
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hashToH256(seedHash),
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dagSize,
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cache,
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(C.ethash_callback_t)(unsafe.Pointer(C.ethashGoCallback_cgo)),
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)
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if d.ptr == nil {
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panic("ethash_full_new IO or memory error")
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}
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runtime.SetFinalizer(d, freeDAG)
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glog.V(logger.Info).Infof("Done generating DAG for epoch %d, it took %v", d.epoch, time.Since(started))
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})
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}
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func freeDAG(d *dag) {
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C.ethash_full_delete(d.ptr)
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d.ptr = nil
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}
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func (d *dag) Ptr() unsafe.Pointer {
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return unsafe.Pointer(d.ptr.data)
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}
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//export ethashGoCallback
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func ethashGoCallback(percent C.unsigned) C.int {
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glog.V(logger.Info).Infof("Generating DAG: %d%%", percent)
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return 0
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}
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// MakeDAG pre-generates a DAG file for the given block number in the
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// given directory. If dir is the empty string, the default directory
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// is used.
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func MakeDAG(blockNum uint64, dir string) error {
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d := &dag{epoch: blockNum / epochLength, dir: dir}
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if blockNum >= epochLength*2048 {
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return fmt.Errorf("block number too high, limit is %d", epochLength*2048)
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}
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d.generate()
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if d.ptr == nil {
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return errors.New("failed")
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}
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return nil
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}
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// Full implements the Search half of the proof of work.
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type Full struct {
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Dir string // use this to specify a non-default DAG directory
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test bool // if set use a smaller DAG size
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turbo bool
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hashRate int32
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mu sync.Mutex // protects dag
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current *dag // current full DAG
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}
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func (pow *Full) getDAG(blockNum uint64) (d *dag) {
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epoch := blockNum / epochLength
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pow.mu.Lock()
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if pow.current != nil && pow.current.epoch == epoch {
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d = pow.current
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} else {
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d = &dag{epoch: epoch, test: pow.test, dir: pow.Dir}
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pow.current = d
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}
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pow.mu.Unlock()
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// wait for it to finish generating.
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d.generate()
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return d
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}
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func (pow *Full) Search(block pow.Block, stop <-chan struct{}, index int) (nonce uint64, mixDigest []byte) {
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dag := pow.getDAG(block.NumberU64())
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r := rand.New(rand.NewSource(time.Now().UnixNano()))
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diff := block.Difficulty()
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i := int64(0)
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starti := i
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start := time.Now().UnixNano()
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previousHashrate := int32(0)
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nonce = uint64(r.Int63())
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hash := hashToH256(block.HashNoNonce())
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target := new(big.Int).Div(maxUint256, diff)
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for {
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select {
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case <-stop:
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atomic.AddInt32(&pow.hashRate, -previousHashrate)
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return 0, nil
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default:
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i++
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// we don't have to update hash rate on every nonce, so update after
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// first nonce check and then after 2^X nonces
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if i == 2 || ((i % (1 << 16)) == 0) {
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elapsed := time.Now().UnixNano() - start
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|
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hashes := (float64(1e9) / float64(elapsed)) * float64(i-starti)
|
||
|
|
hashrateDiff := int32(hashes) - previousHashrate
|
||
|
|
previousHashrate = int32(hashes)
|
||
|
|
atomic.AddInt32(&pow.hashRate, hashrateDiff)
|
||
|
|
}
|
||
|
|
|
||
|
|
ret := C.ethash_full_compute(dag.ptr, hash, C.uint64_t(nonce))
|
||
|
|
result := h256ToHash(ret.result).Big()
|
||
|
|
|
||
|
|
// TODO: disagrees with the spec https://github.com/ethereum/wiki/wiki/Ethash#mining
|
||
|
|
if ret.success && result.Cmp(target) <= 0 {
|
||
|
|
mixDigest = C.GoBytes(unsafe.Pointer(&ret.mix_hash), C.int(32))
|
||
|
|
atomic.AddInt32(&pow.hashRate, -previousHashrate)
|
||
|
|
return nonce, mixDigest
|
||
|
|
}
|
||
|
|
nonce += 1
|
||
|
|
}
|
||
|
|
|
||
|
|
if !pow.turbo {
|
||
|
|
time.Sleep(20 * time.Microsecond)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func (pow *Full) GetHashrate() int64 {
|
||
|
|
return int64(atomic.LoadInt32(&pow.hashRate))
|
||
|
|
}
|
||
|
|
|
||
|
|
func (pow *Full) Turbo(on bool) {
|
||
|
|
// TODO: this needs to use an atomic operation.
|
||
|
|
pow.turbo = on
|
||
|
|
}
|
||
|
|
|
||
|
|
// Ethash combines block verification with Light and
|
||
|
|
// nonce searching with Full into a single proof of work.
|
||
|
|
type Ethash struct {
|
||
|
|
*Light
|
||
|
|
*Full
|
||
|
|
}
|
||
|
|
|
||
|
|
// New creates an instance of the proof of work.
|
||
|
|
func New() *Ethash {
|
||
|
|
return &Ethash{new(Light), &Full{turbo: true}}
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewShared creates an instance of the proof of work., where a single instance
|
||
|
|
// of the Light cache is shared across all instances created with NewShared.
|
||
|
|
func NewShared() *Ethash {
|
||
|
|
return &Ethash{sharedLight, &Full{turbo: true}}
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewForTesting creates a proof of work for use in unit tests.
|
||
|
|
// It uses a smaller DAG and cache size to keep test times low.
|
||
|
|
// DAG files are stored in a temporary directory.
|
||
|
|
//
|
||
|
|
// Nonces found by a testing instance are not verifiable with a
|
||
|
|
// regular-size cache.
|
||
|
|
func NewForTesting() (*Ethash, error) {
|
||
|
|
dir, err := ioutil.TempDir("", "ethash-test")
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
return &Ethash{&Light{test: true}, &Full{Dir: dir, test: true}}, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func GetSeedHash(blockNum uint64) ([]byte, error) {
|
||
|
|
if blockNum >= epochLength*2048 {
|
||
|
|
return nil, fmt.Errorf("block number too high, limit is %d", epochLength*2048)
|
||
|
|
}
|
||
|
|
sh := makeSeedHash(blockNum / epochLength)
|
||
|
|
return sh[:], nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func makeSeedHash(epoch uint64) (sh common.Hash) {
|
||
|
|
for ; epoch > 0; epoch-- {
|
||
|
|
sh = crypto.Sha3Hash(sh[:])
|
||
|
|
}
|
||
|
|
return sh
|
||
|
|
}
|