eth, eth/downloader: don't report stall if fetcher filled the block

2 files changed, 64 insertions, 42 deletions

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 4c8b2e8d0..e3e22a784 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -21,6 +21,7 @@ import (
 	"bytes"
 	"errors"
 	"math"
+	"math/big"
 	"math/rand"
 	"sync"
 	"sync/atomic"
@@ -232,10 +233,10 @@ func (d *Downloader) UnregisterPeer(id string) error {
 
 // Synchronise tries to sync up our local block chain with a remote peer, both
 // adding various sanity checks as well as wrapping it with various log entries.
-func (d *Downloader) Synchronise(id string, head common.Hash) {
-	glog.V(logger.Detail).Infof("Attempting synchronisation: %v, 0x%x", id, head)
+func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int) {
+	glog.V(logger.Detail).Infof("Attempting synchronisation: %v, head 0x%x, TD %v", id, head[:4], td)
 
-	switch err := d.synchronise(id, head); err {
+	switch err := d.synchronise(id, head, td); err {
 	case nil:
 		glog.V(logger.Detail).Infof("Synchronisation completed")
 
@@ -257,7 +258,7 @@ func (d *Downloader) Synchronise(id string, head common.Hash) {
 // synchronise will select the peer and use it for synchronising. If an empty string is given
 // it will use the best peer possible and synchronize if it's TD is higher than our own. If any of the
 // checks fail an error will be returned. This method is synchronous
-func (d *Downloader) synchronise(id string, hash common.Hash) error {
+func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int) error {
 	// Mock out the synchonisation if testing
 	if d.synchroniseMock != nil {
 		return d.synchroniseMock(id, hash)
@@ -295,7 +296,7 @@ func (d *Downloader) synchronise(id string, hash common.Hash) error {
 	if p == nil {
 		return errUnknownPeer
 	}
-	return d.syncWithPeer(p, hash)
+	return d.syncWithPeer(p, hash, td)
 }
 
 // Has checks if the downloader knows about a particular hash, meaning that its
@@ -306,7 +307,7 @@ func (d *Downloader) Has(hash common.Hash) bool {
 
 // syncWithPeer starts a block synchronization based on the hash chain from the
 // specified peer and head hash.
-func (d *Downloader) syncWithPeer(p *peer, hash common.Hash) (err error) {
+func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err error) {
 	d.mux.Post(StartEvent{})
 	defer func() {
 		// reset on error
@@ -335,7 +336,7 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash) (err error) {
 			return err
 		}
 		errc := make(chan error, 2)
-		go func() { errc <- d.fetchHashes(p, number+1) }()
+		go func() { errc <- d.fetchHashes(p, td, number+1) }()
 		go func() { errc <- d.fetchBlocks(number + 1) }()
 
 		// If any fetcher fails, cancel the other
@@ -788,7 +789,7 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 
 // fetchHashes keeps retrieving hashes from the requested number, until no more
 // are returned, potentially throttling on the way.
-func (d *Downloader) fetchHashes(p *peer, from uint64) error {
+func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
 	glog.V(logger.Debug).Infof("%v: downloading hashes from #%d", p, from)
 
 	// Create a timeout timer, and the associated hash fetcher
@@ -827,8 +828,19 @@ func (d *Downloader) fetchHashes(p *peer, from uint64) error {
 				case d.processCh <- false:
 				case <-d.cancelCh:
 				}
-				// Error out if no hashes were retrieved at all
-				if !gotHashes {
+				// If no hashes were retrieved at all, the peer violated it's TD promise that it had a
+				// better chain compared to ours. The only exception is if it's promised blocks were
+				// already imported by other means (e.g. fecher):
+				//
+				// R <remote peer>, L <local node>: Both at block 10
+				// R: Mine block 11, and propagate it to L
+				// L: Queue block 11 for import
+				// L: Notice that R's head and TD increased compared to ours, start sync
+				// L: Import of block 11 finishes
+				// L: Sync begins, and finds common ancestor at 11
+				// L: Request new hashes up from 11 (R's TD was higher, it must have something)
+				// R: Nothing to give
+				if !gotHashes && td.Cmp(d.headBlock().Td) > 0 {
 					return errStallingPeer
 				}
 				return nil
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 8299dd62c..61fc7827b 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -97,8 +97,18 @@ func newTester() *downloadTester {
 }
 
 // sync starts synchronizing with a remote peer, blocking until it completes.
-func (dl *downloadTester) sync(id string) error {
-	err := dl.downloader.synchronise(id, dl.peerHashes[id][0])
+func (dl *downloadTester) sync(id string, td *big.Int) error {
+	hash := dl.peerHashes[id][0]
+
+	// If no particular TD was requested, load from the peer's blockchain
+	if td == nil {
+		td = big.NewInt(1)
+		if block, ok := dl.peerBlocks[id][hash]; ok {
+			td = block.Td
+		}
+	}
+	err := dl.downloader.synchronise(id, hash, td)
+
 	for {
 		// If the queue is empty and processing stopped, break
 		hashes, blocks := dl.downloader.queue.Size()
@@ -261,7 +271,7 @@ func TestSynchronisation60(t *testing.T) {
 	tester.newPeer("peer", eth60, hashes, blocks)
 
 	// Synchronise with the peer and make sure all blocks were retrieved
-	if err := tester.sync("peer"); err != nil {
+	if err := tester.sync("peer", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
@@ -281,7 +291,7 @@ func TestCanonicalSynchronisation61(t *testing.T) {
 	tester.newPeer("peer", eth61, hashes, blocks)
 
 	// Synchronise with the peer and make sure all blocks were retrieved
-	if err := tester.sync("peer"); err != nil {
+	if err := tester.sync("peer", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
@@ -312,7 +322,7 @@ func testThrottling(t *testing.T, protocol int) {
 	// Start a synchronisation concurrently
 	errc := make(chan error)
 	go func() {
-		errc <- tester.sync("peer")
+		errc <- tester.sync("peer", nil)
 	}()
 	// Iteratively take some blocks, always checking the retrieval count
 	for len(tester.ownBlocks) < targetBlocks+1 {
@@ -361,14 +371,14 @@ func TestForkedSynchronisation61(t *testing.T) {
 	tester.newPeer("fork B", eth61, hashesB, blocksB)
 
 	// Synchronise with the peer and make sure all blocks were retrieved
-	if err := tester.sync("fork A"); err != nil {
+	if err := tester.sync("fork A", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != common+fork+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, common+fork+1)
 	}
 	// Synchronise with the second peer and make sure that fork is pulled too
-	if err := tester.sync("fork B"); err != nil {
+	if err := tester.sync("fork B", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != common+2*fork+1 {
@@ -411,7 +421,7 @@ func testCancel(t *testing.T, protocol int) {
 		t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
 	}
 	// Synchronise with the peer, but cancel afterwards
-	if err := tester.sync("peer"); err != nil {
+	if err := tester.sync("peer", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	tester.downloader.cancel()
@@ -438,14 +448,14 @@ func testMultiSynchronisation(t *testing.T, protocol int) {
 	}
 	// Synchronise with the middle peer and make sure half of the blocks were retrieved
 	id := fmt.Sprintf("peer #%d", targetPeers/2)
-	if err := tester.sync(id); err != nil {
+	if err := tester.sync(id, nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != len(tester.peerHashes[id]) {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(tester.peerHashes[id]))
 	}
 	// Synchronise with the best peer and make sure everything is retrieved
-	if err := tester.sync("peer #0"); err != nil {
+	if err := tester.sync("peer #0", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
@@ -469,7 +479,7 @@ func TestSlowSynchronisation60(t *testing.T) {
 
 	// Try to sync with the peers (pull hashes from fast)
 	start := time.Now()
-	if err := tester.sync("fast"); err != nil {
+	if err := tester.sync("fast", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
@@ -497,14 +507,14 @@ func TestNonExistingParentAttack60(t *testing.T) {
 	tester.newPeer("attack", eth60, hashes, blocks)
 
 	// Try and sync with the malicious node and check that it fails
-	if err := tester.sync("attack"); err == nil {
+	if err := tester.sync("attack", nil); err == nil {
 		t.Fatalf("block synchronization succeeded")
 	}
 	if tester.hasBlock(hashes[0]) {
 		t.Fatalf("tester accepted unknown-parent block: %v", blocks[hashes[0]])
 	}
 	// Try to synchronize with the valid chain and make sure it succeeds
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	if !tester.hasBlock(tester.peerHashes["valid"][0]) {
@@ -525,7 +535,7 @@ func TestRepeatingHashAttack60(t *testing.T) { // TODO: Is this thing valid??
 	// Try and sync with the malicious node
 	errc := make(chan error)
 	go func() {
-		errc <- tester.sync("attack")
+		errc <- tester.sync("attack", nil)
 	}()
 	// Make sure that syncing returns and does so with a failure
 	select {
@@ -537,7 +547,7 @@ func TestRepeatingHashAttack60(t *testing.T) { // TODO: Is this thing valid??
 		}
 	}
 	// Ensure that a valid chain can still pass sync
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -555,11 +565,11 @@ func TestNonExistingBlockAttack60(t *testing.T) {
 	tester.newPeer("attack", eth60, hashes, blocks)
 
 	// Try and sync with the malicious node and check that it fails
-	if err := tester.sync("attack"); err != errPeersUnavailable {
+	if err := tester.sync("attack", nil); err != errPeersUnavailable {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errPeersUnavailable)
 	}
 	// Ensure that a valid chain can still pass sync
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -583,11 +593,11 @@ func TestInvalidHashOrderAttack60(t *testing.T) {
 	tester.newPeer("attack", eth60, hashes, blocks)
 
 	// Try and sync with the malicious node and check that it fails
-	if err := tester.sync("attack"); err != errInvalidChain {
+	if err := tester.sync("attack", nil); err != errInvalidChain {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errInvalidChain)
 	}
 	// Ensure that a valid chain can still pass sync
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -611,11 +621,11 @@ func TestMadeupHashChainAttack60(t *testing.T) {
 	tester.newPeer("attack", eth60, randomHashes, nil)
 
 	// Try and sync with the malicious node and check that it fails
-	if err := tester.sync("attack"); err != errCrossCheckFailed {
+	if err := tester.sync("attack", nil); err != errCrossCheckFailed {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errCrossCheckFailed)
 	}
 	// Ensure that a valid chain can still pass sync
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -636,7 +646,7 @@ func TestMadeupHashChainDrippingAttack60(t *testing.T) {
 	// Try and sync with the attacker, one hash at a time
 	tester.maxHashFetch = 1
 	tester.newPeer("attack", eth60, randomHashes, nil)
-	if err := tester.sync("attack"); err != errStallingPeer {
+	if err := tester.sync("attack", nil); err != errStallingPeer {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
 	}
 }
@@ -659,7 +669,7 @@ func TestMadeupBlockChainAttack60(t *testing.T) {
 	// Try and sync with the malicious node and check that it fails
 	tester := newTester()
 	tester.newPeer("attack", eth60, gapped, blocks)
-	if err := tester.sync("attack"); err != errCrossCheckFailed {
+	if err := tester.sync("attack", nil); err != errCrossCheckFailed {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errCrossCheckFailed)
 	}
 	// Ensure that a valid chain can still pass sync
@@ -667,7 +677,7 @@ func TestMadeupBlockChainAttack60(t *testing.T) {
 	crossCheckCycle = defaultCrossCheckCycle
 
 	tester.newPeer("valid", eth60, hashes, blocks)
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -690,7 +700,7 @@ func TestBannedChainStarvationAttack60(t *testing.T) {
 	// the head of the invalid chain is blocked too.
 	for banned := tester.downloader.banned.Size(); ; {
 		// Try to sync with the attacker, check hash chain failure
-		if err := tester.sync("attack"); err != errInvalidChain {
+		if err := tester.sync("attack", nil); err != errInvalidChain {
 			if tester.downloader.banned.Has(forkHashes[0]) && err == errBannedHead {
 				break
 			}
@@ -711,7 +721,7 @@ func TestBannedChainStarvationAttack60(t *testing.T) {
 		t.Fatalf("banned attacker registered: %v", peer)
 	}
 	// Ensure that a valid chain can still pass sync
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -743,7 +753,7 @@ func TestBannedChainMemoryExhaustionAttack60(t *testing.T) {
 	// the head of the invalid chain is blocked too.
 	for {
 		// Try to sync with the attacker, check hash chain failure
-		if err := tester.sync("attack"); err != errInvalidChain {
+		if err := tester.sync("attack", nil); err != errInvalidChain {
 			t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errInvalidChain)
 		}
 		// Short circuit if the entire chain was banned.
@@ -754,7 +764,7 @@ func TestBannedChainMemoryExhaustionAttack60(t *testing.T) {
 		if bans := tester.downloader.banned.Size(); bans > maxBannedHashes {
 			t.Fatalf("ban cap exceeded: have %v, want max %v", bans, maxBannedHashes)
 		}
-		for hash, _ := range core.BadHashes {
+		for hash := range core.BadHashes {
 			if !tester.downloader.banned.Has(hash) {
 				t.Fatalf("hard coded ban evacuated: %x", hash)
 			}
@@ -764,7 +774,7 @@ func TestBannedChainMemoryExhaustionAttack60(t *testing.T) {
 	MaxBlockFetch = defaultMaxBlockFetch
 	maxBannedHashes = defaultMaxBannedHashes
 
-	if err := tester.sync("valid"); err != nil {
+	if err := tester.sync("valid", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 }
@@ -790,7 +800,7 @@ func TestOverlappingDeliveryAttack60(t *testing.T) {
 		return rawGetBlocks(append(request, hashes[0]))
 	}
 	// Test that synchronisation can complete, check for import success
-	if err := tester.sync("attack"); err != nil {
+	if err := tester.sync("attack", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	start := time.Now()
@@ -807,7 +817,7 @@ func TestOverlappingDeliveryAttack60(t *testing.T) {
 func TestHighTDStarvationAttack61(t *testing.T) {
 	tester := newTester()
 	tester.newPeer("attack", eth61, []common.Hash{genesis.Hash()}, nil)
-	if err := tester.sync("attack"); err != errStallingPeer {
+	if err := tester.sync("attack", big.NewInt(1000000)); err != errStallingPeer {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
 	}
 }
@@ -849,7 +859,7 @@ func TestHashAttackerDropping(t *testing.T) {
 		// Simulate a synchronisation and check the required result
 		tester.downloader.synchroniseMock = func(string, common.Hash) error { return tt.result }
 
-		tester.downloader.Synchronise(id, genesis.Hash())
+		tester.downloader.Synchronise(id, genesis.Hash(), big.NewInt(1000))
 		if _, ok := tester.peerHashes[id]; !ok != tt.drop {
 			t.Errorf("test %d: peer drop mismatch for %v: have %v, want %v", i, tt.result, !ok, tt.drop)
 		}