aboutsummaryrefslogblamecommitdiff
path: root/core/headerchain.go
blob: 2a647630c603665715a6e7707b33065c12754818 (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
























































































































































































































































































































































































































































































































































                                                                                                                                                              
// 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/ava-labs/go-ethereum/common"
	"github.com/ava-labs/go-ethereum/consensus"
	"github.com/ava-labs/go-ethereum/core/rawdb"
	"github.com/ava-labs/go-ethereum/core/types"
	"github.com/ava-labs/go-ethereum/ethdb"
	"github.com/ava-labs/go-ethereum/log"
	"github.com/ava-labs/go-ethereum/params"
	lru "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 := rawdb.ReadHeadBlockHash(chainDb); head != (common.Hash{}) {
		if chead := hc.GetHeaderByHash(head); chead != nil {
			hc.currentHeader.Store(chead)
		}
	}
	hc.currentHeaderHash = hc.CurrentHeader().Hash()
	headHeaderGauge.Update(hc.CurrentHeader().Number.Int64())

	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 {
		number := cached.(uint64)
		return &number
	}
	number := rawdb.ReadHeaderNumber(hc.chainDb, hash)
	if number != nil {
		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)
	}
	rawdb.WriteHeader(hc.chainDb, header)

	// 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
		batch := hc.chainDb.NewBatch()
		for i := number + 1; ; i++ {
			hash := rawdb.ReadCanonicalHash(hc.chainDb, i)
			if hash == (common.Hash{}) {
				break
			}
			rawdb.DeleteCanonicalHash(batch, i)
		}
		batch.Write()

		// Overwrite any stale canonical number assignments
		var (
			headHash   = header.ParentHash
			headNumber = header.Number.Uint64() - 1
			headHeader = hc.GetHeader(headHash, headNumber)
		)
		for rawdb.ReadCanonicalHash(hc.chainDb, headNumber) != headHash {
			rawdb.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
		rawdb.WriteCanonicalHash(hc.chainDb, hash, number)
		rawdb.WriteHeadHeaderHash(hc.chainDb, hash)

		hc.currentHeaderHash = hash
		hc.currentHeader.Store(types.CopyHeader(header))
		headHeaderGauge.Update(header.Number.Int64())

		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 message (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))
	if checkFreq != 0 {
		// In case of checkFreq == 0 all seals are left false.
		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
		}
		// Last should always be verified to avoid junk.
		seals[len(seals)-1] = true
	}

	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
		hash := header.Hash()
		if hc.HasHeader(hash, header.Number.Uint64()) {
			externTd := hc.GetTd(hash, header.Number.Uint64())
			localTd := hc.GetTd(hc.currentHeaderHash, hc.CurrentHeader().Number.Uint64())
			if externTd == nil || externTd.Cmp(localTd) <= 0 {
				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]

	context := []interface{}{
		"count", stats.processed, "elapsed", common.PrettyDuration(time.Since(start)),
		"number", last.Number, "hash", last.Hash(),
	}
	if timestamp := time.Unix(int64(last.Time), 0); time.Since(timestamp) > time.Minute {
		context = append(context, []interface{}{"age", common.PrettyAge(timestamp)}...)
	}
	if stats.ignored > 0 {
		context = append(context, []interface{}{"ignored", stats.ignored}...)
	}
	log.Info("Imported new block headers", context...)

	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
}

// GetAncestor retrieves the Nth ancestor of a given block. It assumes that either the given block or
// a close ancestor of it is canonical. maxNonCanonical points to a downwards counter limiting the
// number of blocks to be individually checked before we reach the canonical chain.
//
// Note: ancestor == 0 returns the same block, 1 returns its parent and so on.
func (hc *HeaderChain) GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64) {
	if ancestor > number {
		return common.Hash{}, 0
	}
	if ancestor == 1 {
		// in this case it is cheaper to just read the header
		if header := hc.GetHeader(hash, number); header != nil {
			return header.ParentHash, number - 1
		} else {
			return common.Hash{}, 0
		}
	}
	for ancestor != 0 {
		if rawdb.ReadCanonicalHash(hc.chainDb, number) == hash {
			number -= ancestor
			return rawdb.ReadCanonicalHash(hc.chainDb, number), number
		}
		if *maxNonCanonical == 0 {
			return common.Hash{}, 0
		}
		*maxNonCanonical--
		ancestor--
		header := hc.GetHeader(hash, number)
		if header == nil {
			return common.Hash{}, 0
		}
		hash = header.ParentHash
		number--
	}
	return hash, number
}

// 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 := rawdb.ReadTd(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 {
	number := hc.GetBlockNumber(hash)
	if number == nil {
		return nil
	}
	return hc.GetTd(hash, *number)
}

// 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 {
	rawdb.WriteTd(hc.chainDb, hash, number, td)
	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 := rawdb.ReadHeader(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 {
	number := hc.GetBlockNumber(hash)
	if number == nil {
		return nil
	}
	return hc.GetHeader(hash, *number)
}

// 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
	}
	return rawdb.HasHeader(hc.chainDb, hash, number)
}

// 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 := rawdb.ReadCanonicalHash(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) {
	rawdb.WriteHeadHeaderHash(hc.chainDb, head.Hash())

	hc.currentHeader.Store(head)
	hc.currentHeaderHash = head.Hash()
	headHeaderGauge.Update(head.Number.Int64())
}

type (
	// UpdateHeadBlocksCallback is a callback function that is called by SetHead
	// before head header is updated.
	UpdateHeadBlocksCallback func(ethdb.KeyValueWriter, *types.Header)

	// DeleteBlockContentCallback is a callback function that is called by SetHead
	// before each header is deleted.
	DeleteBlockContentCallback func(ethdb.KeyValueWriter, 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, updateFn UpdateHeadBlocksCallback, delFn DeleteBlockContentCallback) {
	var (
		parentHash common.Hash
		batch      = hc.chainDb.NewBatch()
	)
	for hdr := hc.CurrentHeader(); hdr != nil && hdr.Number.Uint64() > head; hdr = hc.CurrentHeader() {
		hash, num := hdr.Hash(), hdr.Number.Uint64()

		// Rewind block chain to new head.
		parent := hc.GetHeader(hdr.ParentHash, num-1)
		if parent == nil {
			parent = hc.genesisHeader
		}
		parentHash = hdr.ParentHash
		// Notably, since geth has the possibility for setting the head to a low
		// height which is even lower than ancient head.
		// In order to ensure that the head is always no higher than the data in
		// the database(ancient store or active store), we need to update head
		// first then remove the relative data from the database.
		//
		// Update head first(head fast block, head full block) before deleting the data.
		if updateFn != nil {
			updateFn(hc.chainDb, parent)
		}
		// Update head header then.
		rawdb.WriteHeadHeaderHash(hc.chainDb, parentHash)

		// Remove the relative data from the database.
		if delFn != nil {
			delFn(batch, hash, num)
		}
		// Rewind header chain to new head.
		rawdb.DeleteHeader(batch, hash, num)
		rawdb.DeleteTd(batch, hash, num)
		rawdb.DeleteCanonicalHash(batch, num)

		hc.currentHeader.Store(parent)
		hc.currentHeaderHash = parentHash
		headHeaderGauge.Update(parent.Number.Int64())
	}
	batch.Write()

	// Clear out any stale content from the caches
	hc.headerCache.Purge()
	hc.tdCache.Purge()
	hc.numberCache.Purge()
}

// 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
}