1 files changed, 524 insertions, 0 deletions
diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
new file mode 100644
index 000000000..80247d9d2
--- /dev/null
+++ b/eth/fetcher/fetcher_test.go
@@ -0,0 +1,524 @@
+package fetcher
+
+import (
+	"encoding/binary"
+	"errors"
+	"math/big"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+var (
+	knownHash   = common.Hash{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
+	unknownHash = common.Hash{2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}
+	bannedHash  = common.Hash{3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3}
+
+	genesis = createBlock(1, common.Hash{}, knownHash)
+)
+
+// idCounter is used by the createHashes method the generate deterministic but unique hashes
+var idCounter = int64(2) // #1 is the genesis block
+
+// createHashes generates a batch of hashes rooted at a specific point in the chain.
+func createHashes(amount int, root common.Hash) (hashes []common.Hash) {
+	hashes = make([]common.Hash, amount+1)
+	hashes[len(hashes)-1] = root
+
+	for i := 0; i < len(hashes)-1; i++ {
+		binary.BigEndian.PutUint64(hashes[i][:8], uint64(idCounter))
+		idCounter++
+	}
+	return
+}
+
+// createBlock assembles a new block at the given chain height.
+func createBlock(i int, parent, hash common.Hash) *types.Block {
+	header := &types.Header{Number: big.NewInt(int64(i))}
+	block := types.NewBlockWithHeader(header)
+	block.HeaderHash = hash
+	block.ParentHeaderHash = parent
+	return block
+}
+
+// copyBlock makes a deep copy of a block suitable for local modifications.
+func copyBlock(block *types.Block) *types.Block {
+	return createBlock(int(block.Number().Int64()), block.ParentHeaderHash, block.HeaderHash)
+}
+
+// createBlocksFromHashes assembles a collection of blocks, each having a correct
+// place in the given hash chain.
+func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
+	blocks := make(map[common.Hash]*types.Block)
+	for i := 0; i < len(hashes); i++ {
+		parent := knownHash
+		if i < len(hashes)-1 {
+			parent = hashes[i+1]
+		}
+		blocks[hashes[i]] = createBlock(len(hashes)-i, parent, hashes[i])
+	}
+	return blocks
+}
+
+// fetcherTester is a test simulator for mocking out local block chain.
+type fetcherTester struct {
+	fetcher *Fetcher
+
+	hashes []common.Hash                // Hash chain belonging to the tester
+	blocks map[common.Hash]*types.Block // Blocks belonging to the tester
+
+	lock sync.RWMutex
+}
+
+// newTester creates a new fetcher test mocker.
+func newTester() *fetcherTester {
+	tester := &fetcherTester{
+		hashes: []common.Hash{knownHash},
+		blocks: map[common.Hash]*types.Block{knownHash: genesis},
+	}
+	tester.fetcher = New(tester.getBlock, tester.verifyBlock, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
+	tester.fetcher.Start()
+
+	return tester
+}
+
+// getBlock retrieves a block from the tester's block chain.
+func (f *fetcherTester) getBlock(hash common.Hash) *types.Block {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.blocks[hash]
+}
+
+// verifyBlock is a nop placeholder for the block header verification.
+func (f *fetcherTester) verifyBlock(block *types.Block, parent *types.Block) error {
+	return nil
+}
+
+// broadcastBlock is a nop placeholder for the block broadcasting.
+func (f *fetcherTester) broadcastBlock(block *types.Block, propagate bool) {
+}
+
+// chainHeight retrieves the current height (block number) of the chain.
+func (f *fetcherTester) chainHeight() uint64 {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.blocks[f.hashes[len(f.hashes)-1]].NumberU64()
+}
+
+// insertChain injects a new blocks into the simulated chain.
+func (f *fetcherTester) insertChain(blocks types.Blocks) (int, error) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	for i, block := range blocks {
+		// Make sure the parent in known
+		if _, ok := f.blocks[block.ParentHash()]; !ok {
+			return i, errors.New("unknown parent")
+		}
+		// Discard any new blocks if the same height already exists
+		if block.NumberU64() <= f.blocks[f.hashes[len(f.hashes)-1]].NumberU64() {
+			return i, nil
+		}
+		// Otherwise build our current chain
+		f.hashes = append(f.hashes, block.Hash())
+		f.blocks[block.Hash()] = block
+	}
+	return 0, nil
+}
+
+// dropPeer is a nop placeholder for the peer removal.
+func (f *fetcherTester) dropPeer(peer string) {
+}
+
+// peerFetcher retrieves a fetcher associated with a simulated peer.
+func (f *fetcherTester) makeFetcher(blocks map[common.Hash]*types.Block) blockRequesterFn {
+	// Copy all the blocks to ensure they are not tampered with
+	closure := make(map[common.Hash]*types.Block)
+	for hash, block := range blocks {
+		closure[hash] = copyBlock(block)
+	}
+	// Create a function that returns blocks from the closure
+	return func(hashes []common.Hash) error {
+		// Gather the blocks to return
+		blocks := make([]*types.Block, 0, len(hashes))
+		for _, hash := range hashes {
+			if block, ok := closure[hash]; ok {
+				blocks = append(blocks, block)
+			}
+		}
+		// Return on a new thread
+		go f.fetcher.Filter(blocks)
+
+		return nil
+	}
+}
+
+// verifyImportEvent verifies that one single event arrive on an import channel.
+func verifyImportEvent(t *testing.T, imported chan *types.Block) {
+	select {
+	case <-imported:
+	case <-time.After(time.Second):
+		t.Fatalf("import timeout")
+	}
+}
+
+// verifyImportCount verifies that exactly count number of events arrive on an
+// import hook channel.
+func verifyImportCount(t *testing.T, imported chan *types.Block, count int) {
+	for i := 0; i < count; i++ {
+		select {
+		case <-imported:
+		case <-time.After(time.Second):
+			t.Fatalf("block %d: import timeout", i)
+		}
+	}
+	verifyImportDone(t, imported)
+}
+
+// verifyImportDone verifies that no more events are arriving on an import channel.
+func verifyImportDone(t *testing.T, imported chan *types.Block) {
+	select {
+	case <-imported:
+		t.Fatalf("extra block imported")
+	case <-time.After(50 * time.Millisecond):
+	}
+}
+
+// Tests that a fetcher accepts block announcements and initiates retrievals for
+// them, successfully importing into the local chain.
+func TestSequentialAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks until all are imported
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
+		verifyImportEvent(t, imported)
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that if blocks are announced by multiple peers (or even the same buggy
+// peer), they will only get downloaded at most once.
+func TestConcurrentAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	// Assemble a tester with a built in counter for the requests
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	counter := uint32(0)
+	wrapper := func(hashes []common.Hash) error {
+		atomic.AddUint32(&counter, uint32(len(hashes)))
+		return fetcher(hashes)
+	}
+	// Iteratively announce blocks until all are imported
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("first", hashes[i], time.Now().Add(-arriveTimeout), wrapper)
+		tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout+time.Millisecond), wrapper)
+		tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout-time.Millisecond), wrapper)
+
+		verifyImportEvent(t, imported)
+	}
+	verifyImportDone(t, imported)
+
+	// Make sure no blocks were retrieved twice
+	if int(counter) != targetBlocks {
+		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, targetBlocks)
+	}
+}
+
+// Tests that announcements arriving while a previous is being fetched still
+// results in a valid import.
+func TestOverlappingAnnouncements(t *testing.T) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes := createHashes(targetBlocks, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks, but overlap them continuously
+	fetching := make(chan []common.Hash)
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
+		select {
+		case <-fetching:
+		case <-time.After(time.Second):
+			t.Fatalf("hash %d: announce timeout", len(hashes)-i)
+		}
+	}
+	// Wait for all the imports to complete and check count
+	verifyImportCount(t, imported, len(hashes)-1)
+}
+
+// Tests that announces already being retrieved will not be duplicated.
+func TestPendingDeduplication(t *testing.T) {
+	// Create a hash and corresponding block
+	hashes := createHashes(1, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	// Assemble a tester with a built in counter and delayed fetcher
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	delay := 50 * time.Millisecond
+	counter := uint32(0)
+	wrapper := func(hashes []common.Hash) error {
+		atomic.AddUint32(&counter, uint32(len(hashes)))
+
+		// Simulate a long running fetch
+		go func() {
+			time.Sleep(delay)
+			fetcher(hashes)
+		}()
+		return nil
+	}
+	// Announce the same block many times until it's fetched (wait for any pending ops)
+	for tester.getBlock(hashes[0]) == nil {
+		tester.fetcher.Notify("repeater", hashes[0], time.Now().Add(-arriveTimeout), wrapper)
+		time.Sleep(time.Millisecond)
+	}
+	time.Sleep(delay)
+
+	// Check that all blocks were imported and none fetched twice
+	if imported := len(tester.blocks); imported != 2 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 2)
+	}
+	if int(counter) != 1 {
+		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, 1)
+	}
+}
+
+// Tests that announcements retrieved in a random order are cached and eventually
+// imported when all the gaps are filled in.
+func TestRandomArrivalImport(t *testing.T) {
+	// Create a chain of blocks to import, and choose one to delay
+	hashes := createHashes(maxQueueDist, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+	skip := maxQueueDist / 2
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks, skipping one entry
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 1; i >= 0; i-- {
+		if i != skip {
+			tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
+			time.Sleep(time.Millisecond)
+		}
+	}
+	// Finally announce the skipped entry and check full import
+	tester.fetcher.Notify("valid", hashes[skip], time.Now().Add(-arriveTimeout), fetcher)
+	verifyImportCount(t, imported, len(hashes)-1)
+}
+
+// Tests that direct block enqueues (due to block propagation vs. hash announce)
+// are correctly schedule, filling and import queue gaps.
+func TestQueueGapFill(t *testing.T) {
+	// Create a chain of blocks to import, and choose one to not announce at all
+	hashes := createHashes(maxQueueDist, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+	skip := maxQueueDist / 2
+
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	// Iteratively announce blocks, skipping one entry
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 1; i >= 0; i-- {
+		if i != skip {
+			tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
+			time.Sleep(time.Millisecond)
+		}
+	}
+	// Fill the missing block directly as if propagated
+	tester.fetcher.Enqueue("valid", blocks[hashes[skip]])
+	verifyImportCount(t, imported, len(hashes)-1)
+}
+
+// Tests that blocks arriving from various sources (multiple propagations, hash
+// announces, etc) do not get scheduled for import multiple times.
+func TestImportDeduplication(t *testing.T) {
+	// Create two blocks to import (one for duplication, the other for stalling)
+	hashes := createHashes(2, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	// Create the tester and wrap the importer with a counter
+	tester := newTester()
+	fetcher := tester.makeFetcher(blocks)
+
+	counter := uint32(0)
+	tester.fetcher.insertChain = func(blocks types.Blocks) (int, error) {
+		atomic.AddUint32(&counter, uint32(len(blocks)))
+		return tester.insertChain(blocks)
+	}
+	// Instrument the fetching and imported events
+	fetching := make(chan []common.Hash)
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Announce the duplicating block, wait for retrieval, and also propagate directly
+	tester.fetcher.Notify("valid", hashes[0], time.Now().Add(-arriveTimeout), fetcher)
+	<-fetching
+
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+
+	// Fill the missing block directly as if propagated, and check import uniqueness
+	tester.fetcher.Enqueue("valid", blocks[hashes[1]])
+	verifyImportCount(t, imported, 2)
+
+	if counter != 2 {
+		t.Fatalf("import invocation count mismatch: have %v, want %v", counter, 2)
+	}
+}
+
+// Tests that blocks with numbers much lower or higher than out current head get
+// discarded no prevent wasting resources on useless blocks from faulty peers.
+func TestDistantDiscarding(t *testing.T) {
+	// Create a long chain to import
+	hashes := createHashes(3*maxQueueDist, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	head := hashes[len(hashes)/2]
+
+	// Create a tester and simulate a head block being the middle of the above chain
+	tester := newTester()
+	tester.hashes = []common.Hash{head}
+	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
+
+	// Ensure that a block with a lower number than the threshold is discarded
+	tester.fetcher.Enqueue("lower", blocks[hashes[0]])
+	time.Sleep(10 * time.Millisecond)
+	if !tester.fetcher.queue.Empty() {
+		t.Fatalf("fetcher queued stale block")
+	}
+	// Ensure that a block with a higher number than the threshold is discarded
+	tester.fetcher.Enqueue("higher", blocks[hashes[len(hashes)-1]])
+	time.Sleep(10 * time.Millisecond)
+	if !tester.fetcher.queue.Empty() {
+		t.Fatalf("fetcher queued future block")
+	}
+}
+
+// Tests that a peer is unable to use unbounded memory with sending infinite
+// block announcements to a node, but that even in the face of such an attack,
+// the fetcher remains operational.
+func TestHashMemoryExhaustionAttack(t *testing.T) {
+	// Create a tester with instrumented import hooks
+	tester := newTester()
+
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Create a valid chain and an infinite junk chain
+	hashes := createHashes(hashLimit+2*maxQueueDist, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+	valid := tester.makeFetcher(blocks)
+
+	attack := createHashes(hashLimit+2*maxQueueDist, unknownHash)
+	attacker := tester.makeFetcher(nil)
+
+	// Feed the tester a huge hashset from the attacker, and a limited from the valid peer
+	for i := 0; i < len(attack); i++ {
+		if i < maxQueueDist {
+			tester.fetcher.Notify("valid", hashes[len(hashes)-2-i], time.Now(), valid)
+		}
+		tester.fetcher.Notify("attacker", attack[i], time.Now(), attacker)
+	}
+	if len(tester.fetcher.announced) != hashLimit+maxQueueDist {
+		t.Fatalf("queued announce count mismatch: have %d, want %d", len(tester.fetcher.announced), hashLimit+maxQueueDist)
+	}
+	// Wait for fetches to complete
+	verifyImportCount(t, imported, maxQueueDist)
+
+	// Feed the remaining valid hashes to ensure DOS protection state remains clean
+	for i := len(hashes) - maxQueueDist - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), valid)
+		verifyImportEvent(t, imported)
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that blocks sent to the fetcher (either through propagation or via hash
+// announces and retrievals) don't pile up indefinitely, exhausting available
+// system memory.
+func TestBlockMemoryExhaustionAttack(t *testing.T) {
+	// Create a tester with instrumented import hooks
+	tester := newTester()
+
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Create a valid chain and a batch of dangling (but in range) blocks
+	hashes := createHashes(blockLimit+2*maxQueueDist, knownHash)
+	blocks := createBlocksFromHashes(hashes)
+
+	attack := make(map[common.Hash]*types.Block)
+	for len(attack) < blockLimit+2*maxQueueDist {
+		hashes := createHashes(maxQueueDist-1, unknownHash)
+		blocks := createBlocksFromHashes(hashes)
+		for _, hash := range hashes[:maxQueueDist-2] {
+			attack[hash] = blocks[hash]
+		}
+	}
+	// Try to feed all the attacker blocks make sure only a limited batch is accepted
+	for _, block := range attack {
+		tester.fetcher.Enqueue("attacker", block)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if queued := tester.fetcher.queue.Size(); queued != blockLimit {
+		t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit)
+	}
+	// Queue up a batch of valid blocks, and check that a new peer is allowed to do so
+	for i := 0; i < maxQueueDist-1; i++ {
+		tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-3-i]])
+	}
+	time.Sleep(100 * time.Millisecond)
+	if queued := tester.fetcher.queue.Size(); queued != blockLimit+maxQueueDist-1 {
+		t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit+maxQueueDist-1)
+	}
+	// Insert the missing piece (and sanity check the import)
+	tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2]])
+	verifyImportCount(t, imported, maxQueueDist)
+
+	// Insert the remaining blocks in chunks to ensure clean DOS protection
+	for i := maxQueueDist; i < len(hashes)-1; i++ {
+		tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2-i]])
+		verifyImportEvent(t, imported)
+	}
+	verifyImportDone(t, imported)
+}