// Copyright 2015 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 core
import (
crand "crypto/rand"
"math"
"math/big"
mrand "math/rand"
"runtime"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/pow"
"github.com/hashicorp/golang-lru"
)
// HeaderChain implements the basic block header chain logic that is shared by
// core.BlockChain and light.LightChain. It is not usable in itself, only as
// a part of either structure.
// It is not thread safe either, the encapsulating chain structures should do
// the necessary mutex locking/unlocking.
type HeaderChain struct {
chainDb ethdb.Database
genesisHeader *types.Header
currentHeader *types.Header // Current head of the header chain (may be above the block chain!)
currentHeaderHash common.Hash // Hash of the current head of the header chain (prevent recomputing all the time)
headerCache *lru.Cache // Cache for the most recent block headers
tdCache *lru.Cache // Cache for the most recent block total difficulties
procInterrupt func() bool
rand *mrand.Rand
getValidator getHeaderValidatorFn
}
// getHeaderValidatorFn returns a HeaderValidator interface
type getHeaderValidatorFn func() HeaderValidator
// NewHeaderChain creates a new HeaderChain structure.
// getValidator should return the parent's validator
// procInterrupt points to the parent's interrupt semaphore
// wg points to the parent's shutdown wait group
func NewHeaderChain(chainDb ethdb.Database, getValidator getHeaderValidatorFn, procInterrupt func() bool) (*HeaderChain, error) {
headerCache, _ := lru.New(headerCacheLimit)
tdCache, _ := lru.New(tdCacheLimit)
// Seed a fast but crypto originating random generator
seed, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
if err != nil {
return nil, err
}
hc := &HeaderChain{
chainDb: chainDb,
headerCache: headerCache,
tdCache: tdCache,
procInterrupt: procInterrupt,
rand: mrand.New(mrand.NewSource(seed.Int64())),
getValidator: getValidator,
}
hc.genesisHeader = hc.GetHeaderByNumber(0)
if hc.genesisHeader == nil {
genesisBlock, err := WriteDefaultGenesisBlock(chainDb)
if err != nil {
return nil, err
}
glog.V(logger.Info).Infoln("WARNING: Wrote default ethereum genesis block")
hc.genesisHeader = genesisBlock.Header()
}
hc.currentHeader = hc.genesisHeader
if head := GetHeadBlockHash(chainDb); head != (common.Hash{}) {
if chead := hc.GetHeader(head); chead != nil {
hc.currentHeader = chead
}
}
hc.currentHeaderHash = hc.currentHeader.Hash()
return hc, nil
}
// WriteHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (hc *HeaderChain) WriteHeader(header *types.Header) (status WriteStatus, err error) {
// Cache some values to prevent constant recalculation
var (
hash = header.Hash()
number = header.Number.Uint64()
)
// Calculate the total difficulty of the header
ptd := hc.GetTd(header.ParentHash)
if ptd == nil {
return NonStatTy, ParentError(header.ParentHash)
}
localTd := hc.GetTd(hc.currentHeaderHash)
externTd := new(big.Int).Add(header.Difficulty, ptd)
// If the total difficulty is higher than our known, add it to the canonical chain
// Second clause in the if statement reduces the vulnerability to selfish mining.
// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
// Delete any canonical number assignments above the new head
for i := number + 1; GetCanonicalHash(hc.chainDb, i) != (common.Hash{}); i++ {
DeleteCanonicalHash(hc.chainDb, i)
}
// Overwrite any stale canonical number assignments
var (
headHash = header.ParentHash
headHeader = hc.GetHeader(headHash)
headNumber = headHeader.Number.Uint64()
)
for GetCanonicalHash(hc.chainDb, headNumber) != headHash {
WriteCanonicalHash(hc.chainDb, headHash, headNumber)
headHash = headHeader.ParentHash
headHeader = hc.GetHeader(headHash)
headNumber = headHeader.Number.Uint64()
}
// Extend the canonical chain with the new header
if err := WriteCanonicalHash(hc.chainDb, hash, number); err != nil {
glog.Fatalf("failed to insert header number: %v", err)
}
if err := WriteHeadHeaderHash(hc.chainDb, hash); err != nil {
glog.Fatalf("failed to insert head header hash: %v", err)
}
hc.currentHeaderHash, hc.currentHeader = hash, types.CopyHeader(header)
status = CanonStatTy
} else {
status = SideStatTy
}
// Irrelevant of the canonical status, write the header itself to the database
if err := hc.WriteTd(hash, externTd); err != nil {
glog.Fatalf("failed to write header total difficulty: %v", err)
}
if err := WriteHeader(hc.chainDb, header); err != nil {
glog.Fatalf("failed to write header contents: %v", err)
}
hc.headerCache.Add(hash, header)
return
}
// WhCallback is a callback function for inserting individual headers.
// A callback is used for two reasons: first, in a LightChain, status should be
// processed and light chain events sent, while in a BlockChain this is not
// necessary since chain events are sent after inserting blocks. Second, the
// header writes should be protected by the parent chain mutex individually.
type WhCallback func(*types.Header) error
// InsertHeaderChain attempts to insert the given header chain in to the local
// chain, possibly creating a reorg. If an error is returned, it will return the
// index number of the failing header as well an error describing what went wrong.
//
// The verify parameter can be used to fine tune whether nonce verification
// should be done or not. The reason behind the optional check is because some
// of the header retrieval mechanisms already need to verfy nonces, as well as
// because nonces can be verified sparsely, not needing to check each.
func (hc *HeaderChain) InsertHeaderChain(chain []*types.Header, checkFreq int, writeHeader WhCallback) (int, error) {
// Collect some import statistics to report on
stats := struct{ processed, ignored int }{}
start := time.Now()
// Generate the list of headers that should be POW verified
verify := make([]bool, len(chain))
for i := 0; i < len(verify)/checkFreq; i++ {
index := i*checkFreq + hc.rand.Intn(checkFreq)
if index >= len(verify) {
index = len(verify) - 1
}
verify[index] = true
}
verify[len(verify)-1] = true // Last should always be verified to avoid junk
// Create the header verification task queue and worker functions
tasks := make(chan int, len(chain))
for i := 0; i < len(chain); i++ {
tasks <- i
}
close(tasks)
errs, failed := make([]error, len(tasks)), int32(0)
process := func(worker int) {
for index := range tasks {
header, hash := chain[index], chain[index].Hash()
// Short circuit insertion if shutting down or processing failed
if hc.procInterrupt() {
return
}
if atomic.LoadInt32(&failed) > 0 {
return
}
// Short circuit if the header is bad or already known
if BadHashes[hash] {
errs[index] = BadHashError(hash)
atomic.AddInt32(&failed, 1)
return
}
if hc.HasHeader(hash) {
continue
}
// Verify that the header honors the chain parameters
checkPow := verify[index]
var err error
if index == 0 {
err = hc.getValidator().ValidateHeader(header, hc.GetHeader(header.ParentHash), checkPow)
} else {
err = hc.getValidator().ValidateHeader(header, chain[index-1], checkPow)
}
if err != nil {
errs[index] = err
atomic.AddInt32(&failed, 1)
return
}
}
}
// Start as many worker threads as goroutines allowed
pending := new(sync.WaitGroup)
for i := 0; i < runtime.GOMAXPROCS(0); i++ {
pending.Add(1)
go func(id int) {
defer pending.Done()
process(id)
}(i)
}
pending.Wait()
// If anything failed, report
if failed > 0 {
for i, err := range errs {
if err != nil {
return i, err
}
}
}
// All headers passed verification, import them into the database
for i, header := range chain {
// Short circuit insertion if shutting down
if hc.procInterrupt() {
glog.V(logger.Debug).Infoln("premature abort during header chain processing")
break
}
hash := header.Hash()
// If the header's already known, skip it, otherwise store
if hc.HasHeader(hash) {
stats.ignored++
continue
}
if err := writeHeader(header); err != nil {
return i, err
}
stats.processed++
}
// Report some public statistics so the user has a clue what's going on
first, last := chain[0], chain[len(chain)-1]
glog.V(logger.Info).Infof("imported %d header(s) (%d ignored) in %v. #%v [%x… / %x…]", stats.processed, stats.ignored,
time.Since(start), last.Number, first.Hash().Bytes()[:4], last.Hash().Bytes()[:4])
return 0, nil
}
// GetBlockHashesFromHash retrieves a number of block hashes starting at a given
// hash, fetching towards the genesis block.
func (hc *HeaderChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash {
// Get the origin header from which to fetch
header := hc.GetHeader(hash)
if header == nil {
return nil
}
// Iterate the headers until enough is collected or the genesis reached
chain := make([]common.Hash, 0, max)
for i := uint64(0); i < max; i++ {
next := header.ParentHash
if header = hc.GetHeader(next); header == nil {
break
}
chain = append(chain, next)
if header.Number.Cmp(common.Big0) == 0 {
break
}
}
return chain
}
// GetTd retrieves a block's total difficulty in the canonical chain from the
// database by hash, caching it if found.
func (hc *HeaderChain) GetTd(hash common.Hash) *big.Int {
// Short circuit if the td's already in the cache, retrieve otherwise
if cached, ok := hc.tdCache.Get(hash); ok {
return cached.(*big.Int)
}
td := GetTd(hc.chainDb, hash)
if td == nil {
return nil
}
// Cache the found body for next time and return
hc.tdCache.Add(hash, td)
return td
}
// WriteTd stores a block's total difficulty into the database, also caching it
// along the way.
func (hc *HeaderChain) WriteTd(hash common.Hash, td *big.Int) error {
if err := WriteTd(hc.chainDb, hash, td); err != nil {
return err
}
hc.tdCache.Add(hash, new(big.Int).Set(td))
return nil
}
// GetHeader retrieves a block header from the database by hash, caching it if
// found.
func (hc *HeaderChain) GetHeader(hash common.Hash) *types.Header {
// Short circuit if the header's already in the cache, retrieve otherwise
if header, ok := hc.headerCache.Get(hash); ok {
return header.(*types.Header)
}
header := GetHeader(hc.chainDb, hash)
if header == nil {
return nil
}
// Cache the found header for next time and return
hc.headerCache.Add(hash, header)
return header
}
// HasHeader checks if a block header is present in the database or not, caching
// it if present.
func (hc *HeaderChain) HasHeader(hash common.Hash) bool {
return hc.GetHeader(hash) != nil
}
// GetHeaderByNumber retrieves a block header from the database by number,
// caching it (associated with its hash) if found.
func (hc *HeaderChain) GetHeaderByNumber(number uint64) *types.Header {
hash := GetCanonicalHash(hc.chainDb, number)
if hash == (common.Hash{}) {
return nil
}
return hc.GetHeader(hash)
}
// CurrentHeader retrieves the current head header of the canonical chain. The
// header is retrieved from the HeaderChain's internal cache.
func (hc *HeaderChain) CurrentHeader() *types.Header {
return hc.currentHeader
}
// SetCurrentHeader sets the current head header of the canonical chain.
func (hc *HeaderChain) SetCurrentHeader(head *types.Header) {
if err := WriteHeadHeaderHash(hc.chainDb, head.Hash()); err != nil {
glog.Fatalf("failed to insert head header hash: %v", err)
}
hc.currentHeader = head
hc.currentHeaderHash = head.Hash()
}
// DeleteCallback is a callback function that is called by SetHead before
// each header is deleted.
type DeleteCallback func(common.Hash)
// SetHead rewinds the local chain to a new head. Everything above the new head
// will be deleted and the new one set.
func (hc *HeaderChain) SetHead(head uint64, delFn DeleteCallback) {
height := uint64(0)
if hc.currentHeader != nil {
height = hc.currentHeader.Number.Uint64()
}
for hc.currentHeader != nil && hc.currentHeader.Number.Uint64() > head {
hash := hc.currentHeader.Hash()
if delFn != nil {
delFn(hash)
}
DeleteHeader(hc.chainDb, hash)
DeleteTd(hc.chainDb, hash)
hc.currentHeader = hc.GetHeader(hc.currentHeader.ParentHash)
}
// Roll back the canonical chain numbering
for i := height; i > head; i-- {
DeleteCanonicalHash(hc.chainDb, i)
}
// Clear out any stale content from the caches
hc.headerCache.Purge()
hc.tdCache.Purge()
if hc.currentHeader == nil {
hc.currentHeader = hc.genesisHeader
}
hc.currentHeaderHash = hc.currentHeader.Hash()
if err := WriteHeadHeaderHash(hc.chainDb, hc.currentHeaderHash); err != nil {
glog.Fatalf("failed to reset head header hash: %v", err)
}
}
// SetGenesis sets a new genesis block header for the chain
func (hc *HeaderChain) SetGenesis(head *types.Header) {
hc.genesisHeader = head
}
// headerValidator is responsible for validating block headers
//
// headerValidator implements HeaderValidator.
type headerValidator struct {
hc *HeaderChain // Canonical header chain
Pow pow.PoW // Proof of work used for validating
}
// NewBlockValidator returns a new block validator which is safe for re-use
func NewHeaderValidator(chain *HeaderChain, pow pow.PoW) HeaderValidator {
return &headerValidator{
Pow: pow,
hc: chain,
}
}
// ValidateHeader validates the given header and, depending on the pow arg,
// checks the proof of work of the given header. Returns an error if the
// validation failed.
func (v *headerValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
// Short circuit if the parent is missing.
if parent == nil {
return ParentError(header.ParentHash)
}
// Short circuit if the header's already known or its parent missing
if v.hc.HasHeader(header.Hash()) {
return nil
}
return ValidateHeader(v.Pow, header, parent, checkPow, false)
}
