// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package ethash
import (
"bytes"
crand "crypto/rand"
"encoding/json"
"errors"
"math"
"math/big"
"math/rand"
"net/http"
"runtime"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/log"
)
const (
// staleThreshold is the maximum depth of the acceptable stale but valid ethash solution.
staleThreshold = 7
)
var (
errNoMiningWork = errors.New("no mining work available yet")
errInvalidSealResult = errors.New("invalid or stale proof-of-work solution")
)
// Seal implements consensus.Engine, attempting to find a nonce that satisfies
// the block's difficulty requirements.
func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error {
// If we're running a fake PoW, simply return a 0 nonce immediately
if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
header := block.Header()
header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
select {
case results <- block.WithSeal(header):
default:
log.Warn("Sealing result is not read by miner", "mode", "fake", "sealhash", ethash.SealHash(block.Header()))
}
return nil
}
// If we're running a shared PoW, delegate sealing to it
if ethash.shared != nil {
return ethash.shared.Seal(chain, block, results, stop)
}
// Create a runner and the multiple search threads it directs
abort := make(chan struct{})
ethash.lock.Lock()
threads := ethash.threads
if ethash.rand == nil {
seed, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
if err != nil {
ethash.lock.Unlock()
return err
}
ethash.rand = rand.New(rand.NewSource(seed.Int64()))
}
ethash.lock.Unlock()
if threads == 0 {
threads = runtime.NumCPU()
}
if threads < 0 {
threads = 0 // Allows disabling local mining without extra logic around local/remote
}
// Push new work to remote sealer
if ethash.workCh != nil {
ethash.workCh <- &sealTask{block: block, results: results}
}
var (
pend sync.WaitGroup
locals = make(chan *types.Block)
)
for i := 0; i < threads; i++ {
pend.Add(1)
go func(id int, nonce uint64) {
defer pend.Done()
ethash.mine(block, id, nonce, abort, locals)
}(i, uint64(ethash.rand.Int63()))
}
// Wait until sealing is terminated or a nonce is found
go func() {
var result *types.Block
select {
case <-stop:
// Outside abort, stop all miner threads
close(abort)
case result = <-locals:
// One of the threads found a block, abort all others
select {
case results <- result:
default:
log.Warn("Sealing result is not read by miner", "mode", "local", "sealhash", ethash.SealHash(block.Header()))
}
close(abort)
case <-ethash.update:
// Thread count was changed on user request, restart
close(abort)
if err := ethash.Seal(chain, block, results, stop); err != nil {
log.Error("Failed to restart sealing after update", "err", err)
}
}
// Wait for all miners to terminate and return the block
pend.Wait()
}()
return nil
}
// mine is the actual proof-of-work miner that searches for a nonce starting from
// seed that results in correct final block difficulty.
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 = ethash.SealHash(header).Bytes()
target = new(big.Int).Div(two256, header.Difficulty)
number = header.Number.Uint64()
dataset = ethash.dataset(number, false)
)
// Start generating random nonces until we abort or find a good one
var (
attempts = int64(0)
nonce = seed
)
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)
break search
default:
// We don't have to update hash rate on every nonce, so update after after 2^X nonces
attempts++
if (attempts % (1 << 15)) == 0 {
ethash.hashrate.Mark(attempts)
attempts = 0
}
// Compute the PoW value of this 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)
header.Nonce = types.EncodeNonce(nonce)
header.MixDigest = common.BytesToHash(digest)
// Seal and return a block (if still needed)
select {
case found <- block.WithSeal(header):
logger.Trace("Ethash nonce found and reported", "attempts", nonce-seed, "nonce", nonce)
case <-abort:
logger.Trace("Ethash nonce found but discarded", "attempts", nonce-seed, "nonce", nonce)
}
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)
}
// remote is a standalone goroutine to handle remote mining related stuff.
func (ethash *Ethash) remote(notify []string, noverify bool) {
var (
works = make(map[common.Hash]*types.Block)
rates = make(map[common.Hash]hashrate)
results chan<- *types.Block
currentBlock *types.Block
currentWork [4]string
notifyTransport = &http.Transport{}
notifyClient = &http.Client{
Transport: notifyTransport,
Timeout: time.Second,
}
notifyReqs = make([]*http.Request, len(notify))
)
// notifyWork notifies all the specified mining endpoints of the availability of
// new work to be processed.
notifyWork := func() {
work := currentWork
blob, _ := json.Marshal(work)
for i, url := range notify {
// Terminate any previously pending request and create the new work
if notifyReqs[i] != nil {
notifyTransport.CancelRequest(notifyReqs[i])
}
notifyReqs[i], _ = http.NewRequest("POST", url, bytes.NewReader(blob))
notifyReqs[i].Header.Set("Content-Type", "application/json")
// Push the new work concurrently to all the remote nodes
go func(req *http.Request, url string) {
res, err := notifyClient.Do(req)
if err != nil {
log.Warn("Failed to notify remote miner", "err", err)
} else {
log.Trace("Notified remote miner", "miner", url, "hash", log.Lazy{Fn: func() common.Hash { return common.HexToHash(work[0]) }}, "target", work[2])
res.Body.Close()
}
}(notifyReqs[i], url)
}
}
// makeWork creates a work package for external miner.
//
// The work package consists of 3 strings:
// result[0], 32 bytes hex encoded current block header pow-hash
// result[1], 32 bytes hex encoded seed hash used for DAG
// result[2], 32 bytes hex encoded boundary condition ("target"), 2^256/difficulty
// result[3], hex encoded block number
makeWork := func(block *types.Block) {
hash := ethash.SealHash(block.Header())
currentWork[0] = hash.Hex()
currentWork[1] = common.BytesToHash(SeedHash(block.NumberU64())).Hex()
currentWork[2] = common.BytesToHash(new(big.Int).Div(two256, block.Difficulty()).Bytes()).Hex()
currentWork[3] = hexutil.EncodeBig(block.Number())
// Trace the seal work fetched by remote sealer.
currentBlock = block
works[hash] = block
}
// submitWork verifies the submitted pow solution, returning
// whether the solution was accepted or not (not can be both a bad pow as well as
// any other error, like no pending work or stale mining result).
submitWork := func(nonce types.BlockNonce, mixDigest common.Hash, sealhash common.Hash) bool {
if currentBlock == nil {
log.Error("Pending work without block", "sealhash", sealhash)
return false
}
// Make sure the work submitted is present
block := works[sealhash]
if block == nil {
log.Warn("Work submitted but none pending", "sealhash", sealhash, "curnumber", currentBlock.NumberU64())
return false
}
// Verify the correctness of submitted result.
header := block.Header()
header.Nonce = nonce
header.MixDigest = mixDigest
start := time.Now()
if !noverify {
if err := ethash.verifySeal(nil, header, true); err != nil {
log.Warn("Invalid proof-of-work submitted", "sealhash", sealhash, "elapsed", time.Since(start), "err", err)
return false
}
}
// Make sure the result channel is assigned.
if results == nil {
log.Warn("Ethash result channel is empty, submitted mining result is rejected")
return false
}
log.Trace("Verified correct proof-of-work", "sealhash", sealhash, "elapsed", time.Since(start))
// Solutions seems to be valid, return to the miner and notify acceptance.
solution := block.WithSeal(header)
// The submitted solution is within the scope of acceptance.
if solution.NumberU64()+staleThreshold > currentBlock.NumberU64() {
select {
case results <- solution:
log.Debug("Work submitted is acceptable", "number", solution.NumberU64(), "sealhash", sealhash, "hash", solution.Hash())
return true
default:
log.Warn("Sealing result is not read by miner", "mode", "remote", "sealhash", sealhash)
return false
}
}
// The submitted block is too old to accept, drop it.
log.Warn("Work submitted is too old", "number", solution.NumberU64(), "sealhash", sealhash, "hash", solution.Hash())
return false
}
ticker := time.NewTicker(5 * time.Second)
defer ticker.Stop()
for {
select {
case work := <-ethash.workCh:
// Update current work with new received block.
// Note same work can be past twice, happens when changing CPU threads.
results = work.results
makeWork(work.block)
// Notify and requested URLs of the new work availability
notifyWork()
case work := <-ethash.fetchWorkCh:
// Return current mining work to remote miner.
if currentBlock == nil {
work.errc <- errNoMiningWork
} else {
work.res <- currentWork
}
case result := <-ethash.submitWorkCh:
// Verify submitted PoW solution based on maintained mining blocks.
if submitWork(result.nonce, result.mixDigest, result.hash) {
result.errc <- nil
} else {
result.errc <- errInvalidSealResult
}
case result := <-ethash.submitRateCh:
// Trace remote sealer's hash rate by submitted value.
rates[result.id] = hashrate{rate: result.rate, ping: time.Now()}
close(result.done)
case req := <-ethash.fetchRateCh:
// Gather all hash rate submitted by remote sealer.
var total uint64
for _, rate := range rates {
// this could overflow
total += rate.rate
}
req <- total
case <-ticker.C:
// Clear stale submitted hash rate.
for id, rate := range rates {
if time.Since(rate.ping) > 10*time.Second {
delete(rates, id)
}
}
// Clear stale pending blocks
if currentBlock != nil {
for hash, block := range works {
if block.NumberU64()+staleThreshold <= currentBlock.NumberU64() {
delete(works, hash)
}
}
}
case errc := <-ethash.exitCh:
// Exit remote loop if ethash is closed and return relevant error.
errc <- nil
log.Trace("Ethash remote sealer is exiting")
return
}
}
}
