// 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"
"errors"
"fmt"
"math"
"math/big"
mrand "math/rand"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/params"
"github.com/hashicorp/golang-lru"
)
const (
headerCacheLimit = 512
tdCacheLimit = 1024
numberCacheLimit = 2048
)
// 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 {
config *params.ChainConfig
chainDb ethdb.Database
genesisHeader *types.Header
currentHeader atomic.Value // 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
numberCache *lru.Cache // Cache for the most recent block numbers
procInterrupt func() bool
rand *mrand.Rand
engine consensus.Engine
}
// 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, config *params.ChainConfig, engine consensus.Engine, procInterrupt func() bool) (*HeaderChain, error) {
headerCache, _ := lru.New(headerCacheLimit)
tdCache, _ := lru.New(tdCacheLimit)
numberCache, _ := lru.New(numberCacheLimit)
// 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{
config: config,
chainDb: chainDb,
headerCache: headerCache,
tdCache: tdCache,
numberCache: numberCache,
procInterrupt: procInterrupt,
rand: mrand.New(mrand.NewSource(seed.Int64())),
engine: engine,
}
hc.genesisHeader = hc.GetHeaderByNumber(0)
if hc.genesisHeader == nil {
return nil, ErrNoGenesis
}
hc.currentHeader.Store(hc.genesisHeader)
if head := GetHeadBlockHash(chainDb); head != (common.Hash{}) {
if chead := hc.GetHeaderByHash(head); chead != nil {
hc.currentHeader.Store(chead)
}
}
hc.currentHeaderHash = hc.CurrentHeader().Hash()
return hc, nil
}
// GetBlockNumber retrieves the block number belonging to the given hash
// from the cache or database
func (hc *HeaderChain) GetBlockNumber(hash common.Hash) uint64 {
if cached, ok := hc.numberCache.Get(hash); ok {
return cached.(uint64)
}
number := GetBlockNumber(hc.chainDb, hash)
if number != missingNumber {
hc.numberCache.Add(hash, number)
}
return number
}
// 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, number-1)
if ptd == nil {
return NonStatTy, consensus.ErrUnknownAncestor
}
localTd := hc.GetTd(hc.currentHeaderHash, hc.CurrentHeader().Number.Uint64())
externTd := new(big.Int).Add(header.Difficulty, ptd)
// Irrelevant of the canonical status, write the td and header to the database
if err := hc.WriteTd(hash, number, externTd); err != nil {
log.Crit("Failed to write header total difficulty", "err", err)
}
if err := WriteHeader(hc.chainDb, header); err != nil {
log.Crit("Failed to write header content", "err", err)
}
// 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; ; i++ {
hash := GetCanonicalHash(hc.chainDb, i)
if hash == (common.Hash{}) {
break
}
DeleteCanonicalHash(hc.chainDb, i)
}
// Overwrite any stale canonical number assignments
var (
headHash = header.ParentHash
headNumber = header.Number.Uint64() - 1
headHeader = hc.GetHeader(headHash, headNumber)
)
for GetCanonicalHash(hc.chainDb, headNumber) != headHash {
WriteCanonicalHash(hc.chainDb, headHash, headNumber)
headHash = headHeader.ParentHash
headNumber = headHeader.Number.Uint64() - 1
headHeader = hc.GetHeader(headHash, headNumber)
}
// Extend the canonical chain with the new header
if err := WriteCanonicalHash(hc.chainDb, hash, number); err != nil {
log.Crit("Failed to insert header number", "err", err)
}
if err := WriteHeadHeaderHash(hc.chainDb, hash); err != nil {
log.Crit("Failed to insert head header hash", "err", err)
}
hc.currentHeaderHash = hash
hc.currentHeader.Store(types.CopyHeader(header))
status = CanonStatTy
} else {
status = SideStatTy
}
hc.headerCache.Add(hash, header)
hc.numberCache.Add(hash, number)
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
func (hc *HeaderChain) ValidateHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
// Do a sanity check that the provided chain is actually ordered and linked
for i := 1; i < len(chain); i++ {
if chain[i].Number.Uint64() != chain[i-1].Number.Uint64()+1 || chain[i].ParentHash != chain[i-1].Hash() {
// Chain broke ancestry, log a messge (programming error) and skip insertion
log.Error("Non contiguous header insert", "number", chain[i].Number, "hash", chain[i].Hash(),
"parent", chain[i].ParentHash, "prevnumber", chain[i-1].Number, "prevhash", chain[i-1].Hash())
return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, chain[i-1].Number,
chain[i-1].Hash().Bytes()[:4], i, chain[i].Number, chain[i].Hash().Bytes()[:4], chain[i].ParentHash[:4])
}
}
// Generate the list of seal verification requests, and start the parallel verifier
seals := make([]bool, len(chain))
for i := 0; i < len(seals)/checkFreq; i++ {
index := i*checkFreq + hc.rand.Intn(checkFreq)
if index >= len(seals) {
index = len(seals) - 1
}
seals[index] = true
}
seals[len(seals)-1] = true // Last should always be verified to avoid junk
abort, results := hc.engine.VerifyHeaders(hc, chain, seals)
defer close(abort)
// Iterate over the headers and ensure they all check out
for i, header := range chain {
// If the chain is terminating, stop processing blocks
if hc.procInterrupt() {
log.Debug("Premature abort during headers verification")
return 0, errors.New("aborted")
}
// If the header is a banned one, straight out abort
if BadHashes[header.Hash()] {
return i, ErrBlacklistedHash
}
// Otherwise wait for headers checks and ensure they pass
if err := <-results; err != nil {
return i, err
}
}
return 0, nil
}
// 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, writeHeader WhCallback, start time.Time) (int, error) {
// Collect some import statistics to report on
stats := struct{ processed, ignored int }{}
// All headers passed verification, import them into the database
for i, header := range chain {
// Short circuit insertion if shutting down
if hc.procInterrupt() {
log.Debug("Premature abort during headers import")
return i, errors.New("aborted")
}
// If the header's already known, skip it, otherwise store
if hc.HasHeader(header.Hash(), header.Number.Uint64()) {
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
last := chain[len(chain)-1]
log.Info("Imported new block headers", "count", stats.processed, "elapsed", common.PrettyDuration(time.Since(start)),
"number", last.Number, "hash", last.Hash(), "ignored", stats.ignored)
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.GetHeaderByHash(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.Number.Uint64()-1); header == nil {
break
}
chain = append(chain, next)
if header.Number.Sign() == 0 {
break
}
}
return chain
}
// GetTd retrieves a block's total difficulty in the canonical chain from the
// database by hash and number, caching it if found.
func (hc *HeaderChain) GetTd(hash common.Hash, number uint64) *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, number)
if td == nil {
return nil
}
// Cache the found body for next time and return
hc.tdCache.Add(hash, td)
return td
}
// GetTdByHash retrieves a block's total difficulty in the canonical chain from the
// database by hash, caching it if found.
func (hc *HeaderChain) GetTdByHash(hash common.Hash) *big.Int {
return hc.GetTd(hash, hc.GetBlockNumber(hash))
}
// WriteTd stores a block's total difficulty into the database, also caching it
// along the way.
func (hc *HeaderChain) WriteTd(hash common.Hash, number uint64, td *big.Int) error {
if err := WriteTd(hc.chainDb, hash, number, 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 and number,
// caching it if found.
func (hc *HeaderChain) GetHeader(hash common.Hash, number uint64) *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, number)
if header == nil {
return nil
}
// Cache the found header for next time and return
hc.headerCache.Add(hash, header)
return header
}
// GetHeaderByHash retrieves a block header from the database by hash, caching it if
// found.
func (hc *HeaderChain) GetHeaderByHash(hash common.Hash) *types.Header {
return hc.GetHeader(hash, hc.GetBlockNumber(hash))
}
// HasHeader checks if a block header is present in the database or not.
func (hc *HeaderChain) HasHeader(hash common.Hash, number uint64) bool {
if hc.numberCache.Contains(hash) || hc.headerCache.Contains(hash) {
return true
}
ok, _ := hc.chainDb.Has(headerKey(hash, number))
return ok
}
// 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, number)
}
// 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.Load().(*types.Header)
}
// 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 {
log.Crit("Failed to insert head header hash", "err", err)
}
hc.currentHeader.Store(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, uint64)
// 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 hdr := hc.CurrentHeader(); hdr != nil {
height = hdr.Number.Uint64()
}
for hdr := hc.CurrentHeader(); hdr != nil && hdr.Number.Uint64() > head; hdr = hc.CurrentHeader() {
hash := hdr.Hash()
num := hdr.Number.Uint64()
if delFn != nil {
delFn(hash, num)
}
DeleteHeader(hc.chainDb, hash, num)
DeleteTd(hc.chainDb, hash, num)
hc.currentHeader.Store(hc.GetHeader(hdr.ParentHash, hdr.Number.Uint64()-1))
}
// 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()
hc.numberCache.Purge()
if hc.CurrentHeader() == nil {
hc.currentHeader.Store(hc.genesisHeader)
}
hc.currentHeaderHash = hc.CurrentHeader().Hash()
if err := WriteHeadHeaderHash(hc.chainDb, hc.currentHeaderHash); err != nil {
log.Crit("Failed to reset head header hash", "err", err)
}
}
// SetGenesis sets a new genesis block header for the chain
func (hc *HeaderChain) SetGenesis(head *types.Header) {
hc.genesisHeader = head
}
// Config retrieves the header chain's chain configuration.
func (hc *HeaderChain) Config() *params.ChainConfig { return hc.config }
// Engine retrieves the header chain's consensus engine.
func (hc *HeaderChain) Engine() consensus.Engine { return hc.engine }
// GetBlock implements consensus.ChainReader, and returns nil for every input as
// a header chain does not have blocks available for retrieval.
func (hc *HeaderChain) GetBlock(hash common.Hash, number uint64) *types.Block {
return nil
}
