Merge pull request #2081 from zsfelfoldi/light-chain

core: create a header chain structure shared by full and light clients

1 files changed, 432 insertions, 0 deletions

diff --git a/core/headerchain.go b/core/headerchain.go
new file mode 100644
index 000000000..8528801a7
--- /dev/null
+++ b/core/headerchain.go
@@ -0,0 +1,432 @@
+// 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!)
+	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
+		}
+	}
+
+	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) {
+	// Calculate the total difficulty of the header
+	ptd := hc.GetTd(header.ParentHash)
+	if ptd == nil {
+		return NonStatTy, ParentError(header.ParentHash)
+	}
+	localTd := hc.GetTd(hc.currentHeader.Hash())
+	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 := header.Number.Uint64() + 1; GetCanonicalHash(hc.chainDb, i) != (common.Hash{}); i++ {
+			DeleteCanonicalHash(hc.chainDb, i)
+		}
+		// Overwrite any stale canonical number assignments
+		head := hc.GetHeader(header.ParentHash)
+		for GetCanonicalHash(hc.chainDb, head.Number.Uint64()) != head.Hash() {
+			WriteCanonicalHash(hc.chainDb, head.Hash(), head.Number.Uint64())
+			head = hc.GetHeader(head.ParentHash)
+		}
+		// Extend the canonical chain with the new header
+		if err := WriteCanonicalHash(hc.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
+			glog.Fatalf("failed to insert header number: %v", err)
+		}
+		if err := WriteHeadHeaderHash(hc.chainDb, header.Hash()); err != nil {
+			glog.Fatalf("failed to insert head header hash: %v", err)
+		}
+		hc.currentHeader = types.CopyHeader(header)
+		status = CanonStatTy
+	} else {
+		status = SideStatTy
+	}
+	// Irrelevant of the canonical status, write the header itself to the database
+	if err := WriteTd(hc.chainDb, header.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)
+	}
+	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++ {
+		if header = hc.GetHeader(header.ParentHash); header == nil {
+			break
+		}
+		chain = append(chain, header.Hash())
+		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
+}
+
+// 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(header.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
+}
+
+// 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
+	}
+	if err := WriteHeadHeaderHash(hc.chainDb, hc.currentHeader.Hash()); 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)
+}