plugeth/core/headerchain.go
Felix Lange 37dd9086ec core: refactor genesis handling
This commit solves several issues concerning the genesis block:

* Genesis/ChainConfig loading was handled by cmd/geth code. This left
  library users in the cold. They could specify a JSON-encoded
  string and overwrite the config, but didn't get any of the additional
  checks performed by geth.
* Decoding and writing of genesis JSON was conflated in
  WriteGenesisBlock. This made it a lot harder to embed the genesis
  block into the forthcoming config file loader. This commit changes
  things so there is a single Genesis type that represents genesis
  blocks. All uses of Write*Genesis* are changed to use the new type
  instead.
* If the chain config supplied by the user was incompatible with the
  current chain (i.e. the chain had already advanced beyond a scheduled
  fork), it got overwritten. This is not an issue in practice because
  previous forks have always had the highest total difficulty. It might
  matter in the future though. The new code reverts the local chain to
  the point of the fork when upgrading configuration.

The change to genesis block data removes compression library
dependencies from package core.
2017-03-23 15:58:43 +01:00

525 lines
18 KiB
Go

// 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"
"fmt"
"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/log"
"github.com/ethereum/go-ethereum/params"
"github.com/ethereum/go-ethereum/pow"
"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 *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
numberCache *lru.Cache // Cache for the most recent block numbers
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, config *params.ChainConfig, getValidator getHeaderValidatorFn, 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())),
getValidator: getValidator,
}
hc.genesisHeader = hc.GetHeaderByNumber(0)
if hc.genesisHeader == nil {
return nil, ErrNoGenesis
}
hc.currentHeader = hc.genesisHeader
if head := GetHeadBlockHash(chainDb); head != (common.Hash{}) {
if chead := hc.GetHeaderByHash(head); chead != nil {
hc.currentHeader = 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, ParentError(header.ParentHash)
}
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, hc.currentHeader = hash, 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
// 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) 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 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, header.Number.Uint64()-1), 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
}
}
}
return 0, nil
}
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 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
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, caching
// it if present.
func (hc *HeaderChain) HasHeader(hash common.Hash) bool {
return hc.GetHeaderByHash(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, 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
}
// 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 = 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 hc.currentHeader != nil {
height = hc.currentHeader.Number.Uint64()
}
for hc.currentHeader != nil && hc.currentHeader.Number.Uint64() > head {
hash := hc.currentHeader.Hash()
num := hc.currentHeader.Number.Uint64()
if delFn != nil {
delFn(hash, num)
}
DeleteHeader(hc.chainDb, hash, num)
DeleteTd(hc.chainDb, hash, num)
hc.currentHeader = hc.GetHeader(hc.currentHeader.ParentHash, hc.currentHeader.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 = 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
}
// headerValidator is responsible for validating block headers
//
// headerValidator implements HeaderValidator.
type headerValidator struct {
config *params.ChainConfig
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(config *params.ChainConfig, chain *HeaderChain, pow pow.PoW) HeaderValidator {
return &headerValidator{
config: config,
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.config, v.Pow, header, parent, checkPow, false)
}