eth/fetcher, les/fetcher: reuse eth/fetcher as light fetcher

consensus/clique/clique.go

@@ -213,14 +213,14 @@ func (c *Clique) Author(header *types.Header) (common.Address, error) {
 }
 
 // VerifyHeader checks whether a header conforms to the consensus rules.
-func (c *Clique) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
+func (c *Clique) VerifyHeader(chain consensus.ChainHeaderReader, header *types.Header, seal bool) error {
 	return c.verifyHeader(chain, header, nil)
 }
 
 // VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers. The
 // method returns a quit channel to abort the operations and a results channel to
 // retrieve the async verifications (the order is that of the input slice).
-func (c *Clique) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
+func (c *Clique) VerifyHeaders(chain consensus.ChainHeaderReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
 	abort := make(chan struct{})
 	results := make(chan error, len(headers))
 
@@ -242,7 +242,7 @@ func (c *Clique) VerifyHeaders(chain consensus.ChainReader, headers []*types.Hea
 // caller may optionally pass in a batch of parents (ascending order) to avoid
 // looking those up from the database. This is useful for concurrently verifying
 // a batch of new headers.
-func (c *Clique) verifyHeader(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
+func (c *Clique) verifyHeader(chain consensus.ChainHeaderReader, header *types.Header, parents []*types.Header) error {
 	if header.Number == nil {
 		return errUnknownBlock
 	}
@@ -305,7 +305,7 @@ func (c *Clique) verifyHeader(chain consensus.ChainReader, header *types.Header,
 // rather depend on a batch of previous headers. The caller may optionally pass
 // in a batch of parents (ascending order) to avoid looking those up from the
 // database. This is useful for concurrently verifying a batch of new headers.
-func (c *Clique) verifyCascadingFields(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
+func (c *Clique) verifyCascadingFields(chain consensus.ChainHeaderReader, header *types.Header, parents []*types.Header) error {
 	// The genesis block is the always valid dead-end
 	number := header.Number.Uint64()
 	if number == 0 {
@@ -345,7 +345,7 @@ func (c *Clique) verifyCascadingFields(chain consensus.ChainReader, header *type
 }
 
 // snapshot retrieves the authorization snapshot at a given point in time.
-func (c *Clique) snapshot(chain consensus.ChainReader, number uint64, hash common.Hash, parents []*types.Header) (*Snapshot, error) {
+func (c *Clique) snapshot(chain consensus.ChainHeaderReader, number uint64, hash common.Hash, parents []*types.Header) (*Snapshot, error) {
 	// Search for a snapshot in memory or on disk for checkpoints
 	var (
 		headers []*types.Header
@@ -436,7 +436,7 @@ func (c *Clique) VerifyUncles(chain consensus.ChainReader, block *types.Block) e
 
 // VerifySeal implements consensus.Engine, checking whether the signature contained
 // in the header satisfies the consensus protocol requirements.
-func (c *Clique) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
+func (c *Clique) VerifySeal(chain consensus.ChainHeaderReader, header *types.Header) error {
 	return c.verifySeal(chain, header, nil)
 }
 
@@ -444,7 +444,7 @@ func (c *Clique) VerifySeal(chain consensus.ChainReader, header *types.Header) e
 // consensus protocol requirements. The method accepts an optional list of parent
 // headers that aren't yet part of the local blockchain to generate the snapshots
 // from.
-func (c *Clique) verifySeal(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
+func (c *Clique) verifySeal(chain consensus.ChainHeaderReader, header *types.Header, parents []*types.Header) error {
 	// Verifying the genesis block is not supported
 	number := header.Number.Uint64()
 	if number == 0 {
@@ -654,7 +654,7 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, results c
 // CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
 // that a new block should have based on the previous blocks in the chain and the
 // current signer.
-func (c *Clique) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+func (c *Clique) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64, parent *types.Header) *big.Int {
 	snap, err := c.snapshot(chain, parent.Number.Uint64(), parent.Hash(), nil)
 	if err != nil {
 		return nil

consensus/consensus.go

@@ -27,9 +27,9 @@ import (
 	"github.com/ethereum/go-ethereum/rpc"
 )
 
-// ChainReader defines a small collection of methods needed to access the local
+// ChainHeaderReader defines a small collection of methods needed to access the local
-// blockchain during header and/or uncle verification.
+// blockchain during header verification.
-type ChainReader interface {
+type ChainHeaderReader interface {
 	// Config retrieves the blockchain's chain configuration.
 	Config() *params.ChainConfig
 
@@ -44,6 +44,12 @@ type ChainReader interface {
 
 	// GetHeaderByHash retrieves a block header from the database by its hash.
 	GetHeaderByHash(hash common.Hash) *types.Header
+}
+
+// ChainReader defines a small collection of methods needed to access the local
+// blockchain during header and/or uncle verification.
+type ChainReader interface {
+	ChainHeaderReader
 
 	// GetBlock retrieves a block from the database by hash and number.
 	GetBlock(hash common.Hash, number uint64) *types.Block
@@ -59,13 +65,13 @@ type Engine interface {
 	// VerifyHeader checks whether a header conforms to the consensus rules of a
 	// given engine. Verifying the seal may be done optionally here, or explicitly
 	// via the VerifySeal method.
-	VerifyHeader(chain ChainReader, header *types.Header, seal bool) error
+	VerifyHeader(chain ChainHeaderReader, header *types.Header, seal bool) error
 
 	// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
 	// concurrently. The method returns a quit channel to abort the operations and
 	// a results channel to retrieve the async verifications (the order is that of
 	// the input slice).
-	VerifyHeaders(chain ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error)
+	VerifyHeaders(chain ChainHeaderReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error)
 
 	// VerifyUncles verifies that the given block's uncles conform to the consensus
 	// rules of a given engine.
@@ -73,7 +79,7 @@ type Engine interface {
 
 	// VerifySeal checks whether the crypto seal on a header is valid according to
 	// the consensus rules of the given engine.
-	VerifySeal(chain ChainReader, header *types.Header) error
+	VerifySeal(chain ChainHeaderReader, header *types.Header) error
 
 	// Prepare initializes the consensus fields of a block header according to the
 	// rules of a particular engine. The changes are executed inline.
@@ -107,7 +113,7 @@ type Engine interface {
 
 	// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
 	// that a new block should have.
-	CalcDifficulty(chain ChainReader, time uint64, parent *types.Header) *big.Int
+	CalcDifficulty(chain ChainHeaderReader, time uint64, parent *types.Header) *big.Int
 
 	// APIs returns the RPC APIs this consensus engine provides.
 	APIs(chain ChainReader) []rpc.API

consensus/ethash/consensus.go

@@ -81,7 +81,7 @@ func (ethash *Ethash) Author(header *types.Header) (common.Address, error) {
 
 // VerifyHeader checks whether a header conforms to the consensus rules of the
 // stock Ethereum ethash engine.
-func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
+func (ethash *Ethash) VerifyHeader(chain consensus.ChainHeaderReader, header *types.Header, seal bool) error {
 	// If we're running a full engine faking, accept any input as valid
 	if ethash.config.PowMode == ModeFullFake {
 		return nil
@@ -102,7 +102,7 @@ func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.He
 // VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
 // concurrently. The method returns a quit channel to abort the operations and
 // a results channel to retrieve the async verifications.
-func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
+func (ethash *Ethash) VerifyHeaders(chain consensus.ChainHeaderReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
 	// If we're running a full engine faking, accept any input as valid
 	if ethash.config.PowMode == ModeFullFake || len(headers) == 0 {
 		abort, results := make(chan struct{}), make(chan error, len(headers))
@@ -164,7 +164,7 @@ func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*type
 	return abort, errorsOut
 }
 
-func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainReader, headers []*types.Header, seals []bool, index int) error {
+func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainHeaderReader, headers []*types.Header, seals []bool, index int) error {
 	var parent *types.Header
 	if index == 0 {
 		parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1)
@@ -238,7 +238,7 @@ func (ethash *Ethash) VerifyUncles(chain consensus.ChainReader, block *types.Blo
 // verifyHeader checks whether a header conforms to the consensus rules of the
 // stock Ethereum ethash engine.
 // See YP section 4.3.4. "Block Header Validity"
-func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *types.Header, uncle bool, seal bool) error {
+func (ethash *Ethash) verifyHeader(chain consensus.ChainHeaderReader, header, parent *types.Header, uncle bool, seal bool) error {
 	// Ensure that the header's extra-data section is of a reasonable size
 	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
 		return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), params.MaximumExtraDataSize)
@@ -301,7 +301,7 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 // CalcDifficulty is the difficulty adjustment algorithm. It returns
 // the difficulty that a new block should have when created at time
 // given the parent block's time and difficulty.
-func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+func (ethash *Ethash) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64, parent *types.Header) *big.Int {
 	return CalcDifficulty(chain.Config(), time, parent)
 }
 
@@ -479,14 +479,14 @@ func calcDifficultyFrontier(time uint64, parent *types.Header) *big.Int {
 
 // VerifySeal implements consensus.Engine, checking whether the given block satisfies
 // the PoW difficulty requirements.
-func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
+func (ethash *Ethash) VerifySeal(chain consensus.ChainHeaderReader, header *types.Header) error {
 	return ethash.verifySeal(chain, header, false)
 }
 
 // verifySeal checks whether a block satisfies the PoW difficulty requirements,
 // either using the usual ethash cache for it, or alternatively using a full DAG
 // to make remote mining fast.
-func (ethash *Ethash) verifySeal(chain consensus.ChainReader, header *types.Header, fulldag bool) error {
+func (ethash *Ethash) verifySeal(chain consensus.ChainHeaderReader, header *types.Header, fulldag bool) error {
 	// If we're running a fake PoW, accept any seal as valid
 	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
 		time.Sleep(ethash.fakeDelay)

eth/fetcher/fetcher.go

@@ -30,18 +30,21 @@ import (
 )
 
 const (
+	lightTimeout  = time.Millisecond       // Time allowance before an announced header is explicitly requested
 	arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested
 	gatherSlack   = 100 * time.Millisecond // Interval used to collate almost-expired announces with fetches
 	fetchTimeout  = 5 * time.Second        // Maximum allotted time to return an explicitly requested block
 	maxUncleDist  = 7                      // Maximum allowed backward distance from the chain head
 	maxQueueDist  = 32                     // Maximum allowed distance from the chain head to queue
-	hashLimit     = 256                    // Maximum number of unique blocks a peer may have announced
+	hashLimit     = 256                    // Maximum number of unique blocks or headers a peer may have announced
 	blockLimit    = 64                     // Maximum number of unique blocks a peer may have delivered
+	HeaderLimit   = 64                     // Maximum number of unique headers a peer may have delivered
 )
 
-var (
+var errTerminated = errors.New("terminated")
-	errTerminated = errors.New("terminated")
+
-)
+// HeaderRetrievalFn is a callback type for retrieving a header from the local chain.
+type HeaderRetrievalFn func(common.Hash) *types.Header
 
 // blockRetrievalFn is a callback type for retrieving a block from the local chain.
 type blockRetrievalFn func(common.Hash) *types.Block
@@ -61,6 +64,9 @@ type blockBroadcasterFn func(block *types.Block, propagate bool)
 // chainHeightFn is a callback type to retrieve the current chain height.
 type chainHeightFn func() uint64
 
+// headersInsertFn is a callback type to insert a batch of headers into the local chain.
+type headersInsertFn func(headers []*types.Header) (int, error)
+
 // chainInsertFn is a callback type to insert a batch of blocks into the local chain.
 type chainInsertFn func(types.Blocks) (int, error)
 
@@ -100,12 +106,32 @@ type bodyFilterTask struct {
 // inject represents a schedules import operation.
 type inject struct {
 	origin string
-	block  *types.Block
+
+	header *types.Header // Used for light mode fetcher which only cares about header.
+	block  *types.Block  // Used for normal mode fetcher which imports full block.
+}
+
+// number returns the block number of the injected object.
+func (inject *inject) number() uint64 {
+	if inject.header != nil {
+		return inject.header.Number.Uint64()
+	}
+	return inject.block.NumberU64()
+}
+
+// number returns the block hash of the injected object.
+func (inject *inject) hash() common.Hash {
+	if inject.header != nil {
+		return inject.header.Hash()
+	}
+	return inject.block.Hash()
 }
 
 // Fetcher is responsible for accumulating block announcements from various peers
 // and scheduling them for retrieval.
 type Fetcher struct {
+	light bool // The indicator whether it's a light fetcher or not.
+
 	// Various event channels
 	notify chan *announce
 	inject chan *inject
@@ -126,13 +152,15 @@ type Fetcher struct {
 	// Block cache
 	queue  *prque.Prque            // Queue containing the import operations (block number sorted)
 	queues map[string]int          // Per peer block counts to prevent memory exhaustion
-	queued map[common.Hash]*inject // Set of already queued blocks (to dedupe imports)
+	queued map[common.Hash]*inject // Set of already queued blocks (to dedup imports)
 
 	// Callbacks
+	getHeader      HeaderRetrievalFn  // Retrieves a header from the local chain
 	getBlock       blockRetrievalFn   // Retrieves a block from the local chain
 	verifyHeader   headerVerifierFn   // Checks if a block's headers have a valid proof of work
 	broadcastBlock blockBroadcasterFn // Broadcasts a block to connected peers
 	chainHeight    chainHeightFn      // Retrieves the current chain's height
+	insertHeaders  headersInsertFn    // Injects a batch of headers into the chain
 	insertChain    chainInsertFn      // Injects a batch of blocks into the chain
 	dropPeer       peerDropFn         // Drops a peer for misbehaving
 
@@ -141,12 +169,13 @@ type Fetcher struct {
 	queueChangeHook    func(common.Hash, bool)           // Method to call upon adding or deleting a block from the import queue
 	fetchingHook       func([]common.Hash)               // Method to call upon starting a block (eth/61) or header (eth/62) fetch
 	completingHook     func([]common.Hash)               // Method to call upon starting a block body fetch (eth/62)
-	importedHook       func(*types.Block)      // Method to call upon successful block import (both eth/61 and eth/62)
+	importedHook       func(*types.Header, *types.Block) // Method to call upon successful header or block import (both eth/61 and eth/62)
 }
 
 // New creates a block fetcher to retrieve blocks based on hash announcements.
-func New(getBlock blockRetrievalFn, verifyHeader headerVerifierFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher {
+func New(light bool, getHeader HeaderRetrievalFn, getBlock blockRetrievalFn, verifyHeader headerVerifierFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertHeaders headersInsertFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher {
 	return &Fetcher{
+		light:          light,
 		notify:         make(chan *announce),
 		inject:         make(chan *inject),
 		headerFilter:   make(chan chan *headerFilterTask),
@@ -161,10 +190,12 @@ func New(getBlock blockRetrievalFn, verifyHeader headerVerifierFn, broadcastBloc
 		queue:          prque.New(nil),
 		queues:         make(map[string]int),
 		queued:         make(map[common.Hash]*inject),
+		getHeader:      getHeader,
 		getBlock:       getBlock,
 		verifyHeader:   verifyHeader,
 		broadcastBlock: broadcastBlock,
 		chainHeight:    chainHeight,
+		insertHeaders:  insertHeaders,
 		insertChain:    insertChain,
 		dropPeer:       dropPeer,
 	}
@@ -202,8 +233,8 @@ func (f *Fetcher) Notify(peer string, hash common.Hash, number uint64, time time
 	}
 }
 
-// Enqueue tries to fill gaps the fetcher's future import queue.
+// EnqueueBlock tries to fill gaps the fetcher's future import queue.
-func (f *Fetcher) Enqueue(peer string, block *types.Block) error {
+func (f *Fetcher) EnqueueBlock(peer string, block *types.Block) error {
 	op := &inject{
 		origin: peer,
 		block:  block,
@@ -290,12 +321,12 @@ func (f *Fetcher) loop() {
 		height := f.chainHeight()
 		for !f.queue.Empty() {
 			op := f.queue.PopItem().(*inject)
-			hash := op.block.Hash()
+			hash := op.hash()
 			if f.queueChangeHook != nil {
 				f.queueChangeHook(hash, false)
 			}
 			// If too high up the chain or phase, continue later
-			number := op.block.NumberU64()
+			number := op.number()
 			if number > height+1 {
 				f.queue.Push(op, -int64(number))
 				if f.queueChangeHook != nil {
@@ -304,11 +335,15 @@ func (f *Fetcher) loop() {
 				break
 			}
 			// Otherwise if fresh and still unknown, try and import
-			if number+maxUncleDist < height || f.getBlock(hash) != nil {
+			if number+maxUncleDist < height || f.light && f.getHeader(hash) != nil || !f.light && f.getBlock(hash) != nil {
 				f.forgetBlock(hash)
 				continue
 			}
-			f.insert(op.origin, op.block)
+			if f.light {
+				f.importHeaders(op.origin, op.header)
+			} else {
+				f.importBlocks(op.origin, op.block)
+			}
 		}
 		// Wait for an outside event to occur
 		select {
@@ -353,7 +388,10 @@ func (f *Fetcher) loop() {
 		case op := <-f.inject:
 			// A direct block insertion was requested, try and fill any pending gaps
 			propBroadcastInMeter.Mark(1)
-			f.enqueue(op.origin, op.block)
+
+			if !f.light {
+				f.enqueueBlock(op.origin, op.block)
+			}
 
 		case hash := <-f.done:
 			// A pending import finished, remove all traces of the notification
@@ -365,13 +403,18 @@ func (f *Fetcher) loop() {
 			request := make(map[string][]common.Hash)
 
 			for hash, announces := range f.announced {
-				if time.Since(announces[0].time) > arriveTimeout-gatherSlack {
+				timeout := arriveTimeout - gatherSlack
+				if f.light {
+					timeout = 0
+				}
+				if time.Since(announces[0].time) > timeout {
 					// Pick a random peer to retrieve from, reset all others
 					announce := announces[rand.Intn(len(announces))]
 					f.forgetHash(hash)
 
-					// If the block still didn't arrive, queue for fetching
+					// If the block still didn't arrive or it's a light fetcher,
-					if f.getBlock(hash) == nil {
+					// queue for fetching.
+					if f.light && f.getHeader(hash) == nil || !f.light && f.getBlock(hash) == nil {
 						request[announce.origin] = append(request[announce.origin], hash)
 						f.fetching[hash] = announce
 					}
@@ -394,7 +437,9 @@ func (f *Fetcher) loop() {
 				}()
 			}
 			// Schedule the next fetch if blocks are still pending
+			if len(f.announced) >= 1 {
 				f.rescheduleFetch(fetchTimer)
+			}
 
 		case <-completeTimer.C:
 			// At least one header's timer ran out, retrieve everything
@@ -423,7 +468,9 @@ func (f *Fetcher) loop() {
 				go f.completing[hashes[0]].fetchBodies(hashes)
 			}
 			// Schedule the next fetch if blocks are still pending
+			if len(f.fetched) >= 1 {
 				f.rescheduleComplete(completeTimer)
+			}
 
 		case filter := <-f.headerFilter:
 			// Headers arrived from a remote peer. Extract those that were explicitly
@@ -439,7 +486,7 @@ func (f *Fetcher) loop() {
 
 			// Split the batch of headers into unknown ones (to return to the caller),
 			// known incomplete ones (requiring body retrievals) and completed blocks.
-			unknown, incomplete, complete := []*types.Header{}, []*announce{}, []*types.Block{}
+			unknown, incomplete, complete, lightHeaders := []*types.Header{}, []*announce{}, []*types.Block{}, []*announce{}
 			for _, header := range task.headers {
 				hash := header.Hash()
 
@@ -452,6 +499,16 @@ func (f *Fetcher) loop() {
 						f.forgetHash(hash)
 						continue
 					}
+					// Collect all headers only if we are running in light
+					// mode and the headers are not imported by other means.
+					if f.light {
+						if f.getHeader(hash) == nil {
+							announce.header = header
+							lightHeaders = append(lightHeaders, announce)
+							f.forgetHash(hash)
+						}
+						continue
+					}
 					// Only keep if not imported by other means
 					if f.getBlock(hash) == nil {
 						announce.header = header
@@ -496,10 +553,14 @@ func (f *Fetcher) loop() {
 					f.rescheduleComplete(completeTimer)
 				}
 			}
+			// Schedule the header for light fetcher import
+			for _, announce := range lightHeaders {
+				f.enqueueHeader(announce.origin, announce.header)
+			}
 			// Schedule the header-only blocks for import
 			for _, block := range complete {
 				if announce := f.completing[block.Hash()]; announce != nil {
-					f.enqueue(announce.origin, block)
+					f.enqueueBlock(announce.origin, block)
 				}
 			}
 
@@ -555,7 +616,7 @@ func (f *Fetcher) loop() {
 			// Schedule the retrieved blocks for ordered import
 			for _, block := range blocks {
 				if announce := f.completing[block.Hash()]; announce != nil {
-					f.enqueue(announce.origin, block)
+					f.enqueueBlock(announce.origin, block)
 				}
 			}
 		}
@@ -568,6 +629,12 @@ func (f *Fetcher) rescheduleFetch(fetch *time.Timer) {
 	if len(f.announced) == 0 {
 		return
 	}
+	// Schedule announcement retrieval quickly for light mode
+	// since server won't send any headers to client.
+	if f.light {
+		fetch.Reset(lightTimeout)
+		return
+	}
 	// Otherwise find the earliest expiring announcement
 	earliest := time.Now()
 	for _, announces := range f.announced {
@@ -594,9 +661,44 @@ func (f *Fetcher) rescheduleComplete(complete *time.Timer) {
 	complete.Reset(gatherSlack - time.Since(earliest))
 }
 
-// enqueue schedules a new future import operation, if the block to be imported
+// enqueueHeader schedules a new header import operation, if the header to be imported
 // has not yet been seen.
-func (f *Fetcher) enqueue(peer string, block *types.Block) {
+func (f *Fetcher) enqueueHeader(peer string, header *types.Header) {
+	hash := header.Hash()
+	// Ensure the peer isn't DOSing us
+	count := f.queues[peer] + 1
+	if count > HeaderLimit {
+		log.Debug("Discarded propagated header, exceeded allowance", "peer", peer, "number", header.Number, "hash", hash, "limit", blockLimit)
+		propBroadcastDOSMeter.Mark(1)
+		f.forgetHash(hash)
+		return
+	}
+	// Discard any past or too distant blocks
+	if dist := int64(header.Number.Uint64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
+		log.Debug("Discarded propagated header, too far away", "peer", peer, "number", header.Number.Uint64(), "hash", hash, "distance", dist)
+		propBroadcastDropMeter.Mark(1)
+		f.forgetHash(hash)
+		return
+	}
+	// Schedule the block for future importing
+	if _, ok := f.queued[hash]; !ok {
+		op := &inject{
+			origin: peer,
+			header: header,
+		}
+		f.queues[peer] = count
+		f.queued[hash] = op
+		f.queue.Push(op, -int64(header.Number.Uint64()))
+		if f.queueChangeHook != nil {
+			f.queueChangeHook(op.block.Hash(), true)
+		}
+		log.Debug("Queued propagated header", "peer", peer, "number", header.Number.Uint64(), "hash", hash, "queued", f.queue.Size())
+	}
+}
+
+// enqueueBlock schedules a new future import operation, if the block to be imported
+// has not yet been seen.
+func (f *Fetcher) enqueueBlock(peer string, block *types.Block) {
 	hash := block.Hash()
 
 	// Ensure the peer isn't DOSing us
@@ -630,17 +732,52 @@ func (f *Fetcher) enqueue(peer string, block *types.Block) {
 	}
 }
 
-// insert spawns a new goroutine to run a block insertion into the chain. If the
+func (f *Fetcher) importHeaders(peer string, header *types.Header) {
-// block's number is at the same height as the current import phase, it updates
+	hash := header.Hash()
-// the phase states accordingly.
+	log.Debug("Importing propagated header", "peer", peer, "number", header.Number, "hash", hash)
-func (f *Fetcher) insert(peer string, block *types.Block) {
-	hash := block.Hash()
 
-	// Run the import on a new thread
-	log.Debug("Importing propagated block", "peer", peer, "number", block.Number(), "hash", hash)
 	go func() {
 		defer func() { f.done <- hash }()
+		// If the parent's unknown, abort insertion
+		parent := f.getHeader(header.ParentHash)
+		if parent == nil {
+			log.Debug("Unknown parent of propagated header", "peer", peer, "number", header.Number, "hash", hash, "parent", header.ParentHash)
+			return
+		}
+		// Quickly validate the header and propagate the block if it passes
+		switch err := f.verifyHeader(header); err {
+		case nil:
 
+		case consensus.ErrFutureBlock:
+			// Weird future block, don't fail, but neither propagate
+
+		default:
+			// Something went very wrong, drop the peer
+			log.Debug("Propagated header verification failed", "peer", peer, "number", header.Number, "hash", hash, "err", err)
+			f.dropPeer(peer)
+			return
+		}
+		// Run the actual import and log any issues
+		if _, err := f.insertHeaders([]*types.Header{header}); err != nil {
+			log.Debug("Propagated header import failed", "peer", peer, "number", header.Number, "hash", hash, "err", err)
+			return
+		}
+		// Invoke the testing hook if needed
+		if f.importedHook != nil {
+			f.importedHook(header, nil)
+		}
+	}()
+}
+
+// importBlocks spawns a new goroutine to run a block insertion into the chain. If the
+// block's number is at the same height as the current import phase, it updates
+// the phase states accordingly.
+func (f *Fetcher) importBlocks(peer string, block *types.Block) {
+	hash := block.Hash()
+	log.Debug("Importing propagated block", "peer", peer, "number", block.Number(), "hash", hash)
+
+	go func() {
+		defer func() { f.done <- hash }()
 		// If the parent's unknown, abort insertion
 		parent := f.getBlock(block.ParentHash())
 		if parent == nil {
@@ -674,11 +811,25 @@ func (f *Fetcher) insert(peer string, block *types.Block) {
 
 		// Invoke the testing hook if needed
 		if f.importedHook != nil {
-			f.importedHook(block)
+			f.importedHook(nil, block)
 		}
 	}()
 }
 
+func (f *Fetcher) hasHash(hash common.Hash) {
+	if _, ok := f.fetching[hash]; ok {
+	}
+	if _, ok := f.completing[hash]; ok {
+	}
+	if _, ok := f.queued[hash]; ok {
+	}
+	if f.light {
+
+	} else {
+
+	}
+}
+
 // forgetHash removes all traces of a block announcement from the fetcher's
 // internal state.
 func (f *Fetcher) forgetHash(hash common.Hash) {

eth/fetcher/fetcher_test.go

@@ -79,6 +79,7 @@ type fetcherTester struct {
 	fetcher *Fetcher
 
 	hashes  []common.Hash                 // Hash chain belonging to the tester
+	headers map[common.Hash]*types.Header // Headers belonging to the tester
 	blocks  map[common.Hash]*types.Block  // Blocks belonging to the tester
 	drops   map[string]bool               // Map of peers dropped by the fetcher
 
@@ -86,18 +87,27 @@ type fetcherTester struct {
 }
 
 // newTester creates a new fetcher test mocker.
-func newTester() *fetcherTester {
+func newTester(light bool) *fetcherTester {
 	tester := &fetcherTester{
 		hashes:  []common.Hash{genesis.Hash()},
+		headers: map[common.Hash]*types.Header{genesis.Hash(): genesis.Header()},
 		blocks:  map[common.Hash]*types.Block{genesis.Hash(): genesis},
 		drops:   make(map[string]bool),
 	}
-	tester.fetcher = New(tester.getBlock, tester.verifyHeader, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
+	tester.fetcher = New(light, tester.getHeader, tester.getBlock, tester.verifyHeader, tester.broadcastBlock, tester.chainHeight, tester.insertHeaders, tester.insertChain, tester.dropPeer)
 	tester.fetcher.Start()
 
 	return tester
 }
 
+// getHeader retrieves a header from the tester's block chain.
+func (f *fetcherTester) getHeader(hash common.Hash) *types.Header {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.headers[hash]
+}
+
 // getBlock retrieves a block from the tester's block chain.
 func (f *fetcherTester) getBlock(hash common.Hash) *types.Block {
 	f.lock.RLock()
@@ -120,9 +130,33 @@ func (f *fetcherTester) chainHeight() uint64 {
 	f.lock.RLock()
 	defer f.lock.RUnlock()
 
+	if f.fetcher.light {
+		return f.headers[f.hashes[len(f.hashes)-1]].Number.Uint64()
+	}
 	return f.blocks[f.hashes[len(f.hashes)-1]].NumberU64()
 }
 
+// insertChain injects a new headers into the simulated chain.
+func (f *fetcherTester) insertHeaders(headers []*types.Header) (int, error) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	for i, header := range headers {
+		// Make sure the parent in known
+		if _, ok := f.headers[header.ParentHash]; !ok {
+			return i, errors.New("unknown parent")
+		}
+		// Discard any new blocks if the same height already exists
+		if header.Number.Uint64() <= f.headers[f.hashes[len(f.hashes)-1]].Number.Uint64() {
+			return i, nil
+		}
+		// Otherwise build our current chain
+		f.hashes = append(f.hashes, header.Hash())
+		f.headers[header.Hash()] = header
+	}
+	return 0, nil
+}
+
 // insertChain injects a new blocks into the simulated chain.
 func (f *fetcherTester) insertChain(blocks types.Blocks) (int, error) {
 	f.lock.Lock()
@@ -233,7 +267,7 @@ func verifyCompletingEvent(t *testing.T, completing chan []common.Hash, arrive b
 }
 
 // verifyImportEvent verifies that one single event arrive on an import channel.
-func verifyImportEvent(t *testing.T, imported chan *types.Block, arrive bool) {
+func verifyImportEvent(t *testing.T, imported chan interface{}, arrive bool) {
 	if arrive {
 		select {
 		case <-imported:
@@ -251,7 +285,7 @@ func verifyImportEvent(t *testing.T, imported chan *types.Block, arrive bool) {
 
 // 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) {
+func verifyImportCount(t *testing.T, imported chan interface{}, count int) {
 	for i := 0; i < count; i++ {
 		select {
 		case <-imported:
@@ -263,7 +297,7 @@ func verifyImportCount(t *testing.T, imported chan *types.Block, count int) {
 }
 
 // verifyImportDone verifies that no more events are arriving on an import channel.
-func verifyImportDone(t *testing.T, imported chan *types.Block) {
+func verifyImportDone(t *testing.T, imported chan interface{}) {
 	select {
 	case <-imported:
 		t.Fatalf("extra block imported")
@@ -271,45 +305,62 @@ func verifyImportDone(t *testing.T, imported chan *types.Block) {
 	}
 }
 
+// verifyChainHeight verifies the chain height is as expected.
+func verifyChainHeight(t *testing.T, fetcher *fetcherTester, height uint64) {
+	if fetcher.chainHeight() != height {
+		t.Fatalf("chain height mismatch, got %d, want %d", fetcher.chainHeight(), height)
+	}
+}
+
 // Tests that a fetcher accepts block announcements and initiates retrievals for
 // them, successfully importing into the local chain.
-func TestSequentialAnnouncements62(t *testing.T) { testSequentialAnnouncements(t, 62) }
+func TestFullSequentialAnnouncements(t *testing.T)  { testSequentialAnnouncements(t, false) }
-func TestSequentialAnnouncements63(t *testing.T) { testSequentialAnnouncements(t, 63) }
+func TestLightSequentialAnnouncements(t *testing.T) { testSequentialAnnouncements(t, true) }
-func TestSequentialAnnouncements64(t *testing.T) { testSequentialAnnouncements(t, 64) }
 
-func testSequentialAnnouncements(t *testing.T, protocol int) {
+func testSequentialAnnouncements(t *testing.T, light bool) {
 	// Create a chain of blocks to import
 	targetBlocks := 4 * hashLimit
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
 	// Iteratively announce blocks until all are imported
-	imported := make(chan *types.Block)
+	imported := make(chan interface{})
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
-
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 	for i := len(hashes) - 2; i >= 0; i-- {
 		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
 		verifyImportEvent(t, imported, true)
 	}
 	verifyImportDone(t, imported)
+	verifyChainHeight(t, tester, uint64(len(hashes)-1))
 }
 
 // Tests that if blocks are announced by multiple peers (or even the same buggy
 // peer), they will only get downloaded at most once.
-func TestConcurrentAnnouncements62(t *testing.T) { testConcurrentAnnouncements(t, 62) }
+func TestFullConcurrentAnnouncements(t *testing.T)  { testConcurrentAnnouncements(t, false) }
-func TestConcurrentAnnouncements63(t *testing.T) { testConcurrentAnnouncements(t, 63) }
+func TestLightConcurrentAnnouncements(t *testing.T) { testConcurrentAnnouncements(t, true) }
-func TestConcurrentAnnouncements64(t *testing.T) { testConcurrentAnnouncements(t, 64) }
 
-func testConcurrentAnnouncements(t *testing.T, protocol int) {
+func testConcurrentAnnouncements(t *testing.T, light bool) {
 	// Create a chain of blocks to import
 	targetBlocks := 4 * hashLimit
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
 	// Assemble a tester with a built in counter for the requests
-	tester := newTester()
+	tester := newTester(light)
 	firstHeaderFetcher := tester.makeHeaderFetcher("first", blocks, -gatherSlack)
 	firstBodyFetcher := tester.makeBodyFetcher("first", blocks, 0)
 	secondHeaderFetcher := tester.makeHeaderFetcher("second", blocks, -gatherSlack)
@@ -325,8 +376,20 @@ func testConcurrentAnnouncements(t *testing.T, protocol int) {
 		return secondHeaderFetcher(hash)
 	}
 	// Iteratively announce blocks until all are imported
-	imported := make(chan *types.Block)
+	imported := make(chan interface{})
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 
 	for i := len(hashes) - 2; i >= 0; i-- {
 		tester.fetcher.Notify("first", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), firstHeaderWrapper, firstBodyFetcher)
@@ -340,31 +403,42 @@ func testConcurrentAnnouncements(t *testing.T, protocol int) {
 	if int(counter) != targetBlocks {
 		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, targetBlocks)
 	}
+	verifyChainHeight(t, tester, uint64(len(hashes)-1))
 }
 
 // Tests that announcements arriving while a previous is being fetched still
 // results in a valid import.
-func TestOverlappingAnnouncements62(t *testing.T) { testOverlappingAnnouncements(t, 62) }
+func TestFullOverlappingAnnouncements(t *testing.T)  { testOverlappingAnnouncements(t, false) }
-func TestOverlappingAnnouncements63(t *testing.T) { testOverlappingAnnouncements(t, 63) }
+func TestLightOverlappingAnnouncements(t *testing.T) { testOverlappingAnnouncements(t, true) }
-func TestOverlappingAnnouncements64(t *testing.T) { testOverlappingAnnouncements(t, 64) }
 
-func testOverlappingAnnouncements(t *testing.T, protocol int) {
+func testOverlappingAnnouncements(t *testing.T, light bool) {
 	// Create a chain of blocks to import
 	targetBlocks := 4 * hashLimit
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
 	// Iteratively announce blocks, but overlap them continuously
 	overlap := 16
-	imported := make(chan *types.Block, len(hashes)-1)
+	imported := make(chan interface{}, len(hashes)-1)
 	for i := 0; i < overlap; i++ {
 		imported <- nil
 	}
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
-
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 	for i := len(hashes) - 2; i >= 0; i-- {
 		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
 		select {
@@ -375,19 +449,19 @@ func testOverlappingAnnouncements(t *testing.T, protocol int) {
 	}
 	// Wait for all the imports to complete and check count
 	verifyImportCount(t, imported, overlap)
+	verifyChainHeight(t, tester, uint64(len(hashes)-1))
 }
 
 // Tests that announces already being retrieved will not be duplicated.
-func TestPendingDeduplication62(t *testing.T) { testPendingDeduplication(t, 62) }
+func TestFullPendingDeduplication(t *testing.T)  { testPendingDeduplication(t, false) }
-func TestPendingDeduplication63(t *testing.T) { testPendingDeduplication(t, 63) }
+func TestLightPendingDeduplication(t *testing.T) { testPendingDeduplication(t, true) }
-func TestPendingDeduplication64(t *testing.T) { testPendingDeduplication(t, 64) }
 
-func testPendingDeduplication(t *testing.T, protocol int) {
+func testPendingDeduplication(t *testing.T, light bool) {
 	// Create a hash and corresponding block
 	hashes, blocks := makeChain(1, 0, genesis)
 
 	// Assemble a tester with a built in counter and delayed fetcher
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("repeater", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("repeater", blocks, 0)
 
@@ -404,40 +478,57 @@ func testPendingDeduplication(t *testing.T, protocol int) {
 		return nil
 	}
 	// Announce the same block many times until it's fetched (wait for any pending ops)
-	for tester.getBlock(hashes[0]) == nil {
+	checkNonExist := func() bool {
+		return tester.getBlock(hashes[0]) == nil
+	}
+	if light {
+		checkNonExist = func() bool {
+			return tester.getHeader(hashes[0]) == nil
+		}
+	}
+	for checkNonExist() {
 		tester.fetcher.Notify("repeater", hashes[0], 1, time.Now().Add(-arriveTimeout), headerWrapper, bodyFetcher)
 		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)
 	}
+	verifyChainHeight(t, tester, 1)
 }
 
 // Tests that announcements retrieved in a random order are cached and eventually
 // imported when all the gaps are filled in.
-func TestRandomArrivalImport62(t *testing.T) { testRandomArrivalImport(t, 62) }
+func TestFullRandomArrivalImport(t *testing.T)  { testRandomArrivalImport(t, false) }
-func TestRandomArrivalImport63(t *testing.T) { testRandomArrivalImport(t, 63) }
+func TestLightRandomArrivalImport(t *testing.T) { testRandomArrivalImport(t, true) }
-func TestRandomArrivalImport64(t *testing.T) { testRandomArrivalImport(t, 64) }
 
-func testRandomArrivalImport(t *testing.T, protocol int) {
+func testRandomArrivalImport(t *testing.T, light bool) {
 	// Create a chain of blocks to import, and choose one to delay
 	targetBlocks := maxQueueDist
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 	skip := targetBlocks / 2
 
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
 	// Iteratively announce blocks, skipping one entry
-	imported := make(chan *types.Block, len(hashes)-1)
+	imported := make(chan interface{}, len(hashes)-1)
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 
 	for i := len(hashes) - 1; i >= 0; i-- {
 		if i != skip {
@@ -448,27 +539,26 @@ func testRandomArrivalImport(t *testing.T, protocol int) {
 	// Finally announce the skipped entry and check full import
 	tester.fetcher.Notify("valid", hashes[skip], uint64(len(hashes)-skip-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
 	verifyImportCount(t, imported, len(hashes)-1)
+	verifyChainHeight(t, tester, uint64(len(hashes)-1))
 }
 
 // Tests that direct block enqueues (due to block propagation vs. hash announce)
 // are correctly schedule, filling and import queue gaps.
-func TestQueueGapFill62(t *testing.T) { testQueueGapFill(t, 62) }
+func TestFullQueueGapFill(t *testing.T) { testQueueGapFill(t, false) }
-func TestQueueGapFill63(t *testing.T) { testQueueGapFill(t, 63) }
-func TestQueueGapFill64(t *testing.T) { testQueueGapFill(t, 64) }
 
-func testQueueGapFill(t *testing.T, protocol int) {
+func testQueueGapFill(t *testing.T, light bool) {
 	// Create a chain of blocks to import, and choose one to not announce at all
 	targetBlocks := maxQueueDist
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 	skip := targetBlocks / 2
 
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
 	// Iteratively announce blocks, skipping one entry
-	imported := make(chan *types.Block, len(hashes)-1)
+	imported := make(chan interface{}, len(hashes)-1)
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) { imported <- block }
 
 	for i := len(hashes) - 1; i >= 0; i-- {
 		if i != skip {
@@ -477,22 +567,21 @@ func testQueueGapFill(t *testing.T, protocol int) {
 		}
 	}
 	// Fill the missing block directly as if propagated
-	tester.fetcher.Enqueue("valid", blocks[hashes[skip]])
+	tester.fetcher.EnqueueBlock("valid", blocks[hashes[skip]])
 	verifyImportCount(t, imported, len(hashes)-1)
+	verifyChainHeight(t, tester, uint64(len(hashes)-1))
 }
 
 // Tests that blocks arriving from various sources (multiple propagations, hash
 // announces, etc) do not get scheduled for import multiple times.
-func TestImportDeduplication62(t *testing.T) { testImportDeduplication(t, 62) }
+func TestFullImportDeduplication(t *testing.T) { testImportDeduplication(t, false) }
-func TestImportDeduplication63(t *testing.T) { testImportDeduplication(t, 63) }
-func TestImportDeduplication64(t *testing.T) { testImportDeduplication(t, 64) }
 
-func testImportDeduplication(t *testing.T, protocol int) {
+func testImportDeduplication(t *testing.T, light bool) {
 	// Create two blocks to import (one for duplication, the other for stalling)
 	hashes, blocks := makeChain(2, 0, genesis)
 
 	// Create the tester and wrap the importer with a counter
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
@@ -503,20 +592,20 @@ func testImportDeduplication(t *testing.T, protocol int) {
 	}
 	// Instrument the fetching and imported events
 	fetching := make(chan []common.Hash)
-	imported := make(chan *types.Block, len(hashes)-1)
+	imported := make(chan interface{}, len(hashes)-1)
 	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) { imported <- block }
 
 	// Announce the duplicating block, wait for retrieval, and also propagate directly
 	tester.fetcher.Notify("valid", hashes[0], 1, time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
 	<-fetching
 
-	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.EnqueueBlock("valid", blocks[hashes[0]])
-	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.EnqueueBlock("valid", blocks[hashes[0]])
-	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.EnqueueBlock("valid", blocks[hashes[0]])
 
 	// Fill the missing block directly as if propagated, and check import uniqueness
-	tester.fetcher.Enqueue("valid", blocks[hashes[1]])
+	tester.fetcher.EnqueueBlock("valid", blocks[hashes[1]])
 	verifyImportCount(t, imported, 2)
 
 	if counter != 2 {
@@ -526,7 +615,9 @@ func testImportDeduplication(t *testing.T, protocol int) {
 
 // Tests that blocks with numbers much lower or higher than out current head get
 // discarded to prevent wasting resources on useless blocks from faulty peers.
-func TestDistantPropagationDiscarding(t *testing.T) {
+func TestFullDistantPropagationDiscarding(t *testing.T) { testDistantPropagationDiscarding(t, false) }
+
+func testDistantPropagationDiscarding(t *testing.T, light bool) {
 	// Create a long chain to import and define the discard boundaries
 	hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
 	head := hashes[len(hashes)/2]
@@ -534,7 +625,7 @@ func TestDistantPropagationDiscarding(t *testing.T) {
 	low, high := len(hashes)/2+maxUncleDist+1, len(hashes)/2-maxQueueDist-1
 
 	// Create a tester and simulate a head block being the middle of the above chain
-	tester := newTester()
+	tester := newTester(light)
 
 	tester.lock.Lock()
 	tester.hashes = []common.Hash{head}
@@ -542,13 +633,13 @@ func TestDistantPropagationDiscarding(t *testing.T) {
 	tester.lock.Unlock()
 
 	// Ensure that a block with a lower number than the threshold is discarded
-	tester.fetcher.Enqueue("lower", blocks[hashes[low]])
+	tester.fetcher.EnqueueBlock("lower", blocks[hashes[low]])
 	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[high]])
+	tester.fetcher.EnqueueBlock("higher", blocks[hashes[high]])
 	time.Sleep(10 * time.Millisecond)
 	if !tester.fetcher.queue.Empty() {
 		t.Fatalf("fetcher queued future block")
@@ -558,11 +649,10 @@ func TestDistantPropagationDiscarding(t *testing.T) {
 // Tests that announcements with numbers much lower or higher than out current
 // head get discarded to prevent wasting resources on useless blocks from faulty
 // peers.
-func TestDistantAnnouncementDiscarding62(t *testing.T) { testDistantAnnouncementDiscarding(t, 62) }
+func TestFullDistantAnnouncementDiscarding(t *testing.T)  { testDistantAnnouncementDiscarding(t, false) }
-func TestDistantAnnouncementDiscarding63(t *testing.T) { testDistantAnnouncementDiscarding(t, 63) }
+func TestLightDistantAnnouncementDiscarding(t *testing.T) { testDistantAnnouncementDiscarding(t, true) }
-func TestDistantAnnouncementDiscarding64(t *testing.T) { testDistantAnnouncementDiscarding(t, 64) }
 
-func testDistantAnnouncementDiscarding(t *testing.T, protocol int) {
+func testDistantAnnouncementDiscarding(t *testing.T, light bool) {
 	// Create a long chain to import and define the discard boundaries
 	hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
 	head := hashes[len(hashes)/2]
@@ -570,10 +660,11 @@ func testDistantAnnouncementDiscarding(t *testing.T, protocol int) {
 	low, high := len(hashes)/2+maxUncleDist+1, len(hashes)/2-maxQueueDist-1
 
 	// Create a tester and simulate a head block being the middle of the above chain
-	tester := newTester()
+	tester := newTester(light)
 
 	tester.lock.Lock()
 	tester.hashes = []common.Hash{head}
+	tester.headers = map[common.Hash]*types.Header{head: blocks[head].Header()}
 	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
 	tester.lock.Unlock()
 
@@ -601,20 +692,31 @@ func testDistantAnnouncementDiscarding(t *testing.T, protocol int) {
 
 // Tests that peers announcing blocks with invalid numbers (i.e. not matching
 // the headers provided afterwards) get dropped as malicious.
-func TestInvalidNumberAnnouncement62(t *testing.T) { testInvalidNumberAnnouncement(t, 62) }
+func TestFullInvalidNumberAnnouncement(t *testing.T)  { testInvalidNumberAnnouncement(t, false) }
-func TestInvalidNumberAnnouncement63(t *testing.T) { testInvalidNumberAnnouncement(t, 63) }
+func TestLightInvalidNumberAnnouncement(t *testing.T) { testInvalidNumberAnnouncement(t, true) }
-func TestInvalidNumberAnnouncement64(t *testing.T) { testInvalidNumberAnnouncement(t, 64) }
 
-func testInvalidNumberAnnouncement(t *testing.T, protocol int) {
+func testInvalidNumberAnnouncement(t *testing.T, light bool) {
 	// Create a single block to import and check numbers against
 	hashes, blocks := makeChain(1, 0, genesis)
 
-	tester := newTester()
+	tester := newTester(light)
 	badHeaderFetcher := tester.makeHeaderFetcher("bad", blocks, -gatherSlack)
 	badBodyFetcher := tester.makeBodyFetcher("bad", blocks, 0)
 
-	imported := make(chan *types.Block)
+	imported := make(chan interface{})
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 
 	// Announce a block with a bad number, check for immediate drop
 	tester.fetcher.Notify("bad", hashes[0], 2, time.Now().Add(-arriveTimeout), badHeaderFetcher, badBodyFetcher)
@@ -646,15 +748,13 @@ func testInvalidNumberAnnouncement(t *testing.T, protocol int) {
 
 // Tests that if a block is empty (i.e. header only), no body request should be
 // made, and instead the header should be assembled into a whole block in itself.
-func TestEmptyBlockShortCircuit62(t *testing.T) { testEmptyBlockShortCircuit(t, 62) }
+func TestFullEmptyBlockShortCircuit(t *testing.T) { testEmptyBlockShortCircuit(t, false) }
-func TestEmptyBlockShortCircuit63(t *testing.T) { testEmptyBlockShortCircuit(t, 63) }
-func TestEmptyBlockShortCircuit64(t *testing.T) { testEmptyBlockShortCircuit(t, 64) }
 
-func testEmptyBlockShortCircuit(t *testing.T, protocol int) {
+func testEmptyBlockShortCircuit(t *testing.T, light bool) {
 	// Create a chain of blocks to import
 	hashes, blocks := makeChain(32, 0, genesis)
 
-	tester := newTester()
+	tester := newTester(light)
 	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
 	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
 
@@ -665,8 +765,20 @@ func testEmptyBlockShortCircuit(t *testing.T, protocol int) {
 	completing := make(chan []common.Hash)
 	tester.fetcher.completingHook = func(hashes []common.Hash) { completing <- hashes }
 
-	imported := make(chan *types.Block)
+	imported := make(chan interface{})
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) {
+		if light {
+			if header == nil {
+				t.Fatalf("Fetcher try to import empty header")
+			}
+			imported <- header
+		} else {
+			if block == nil {
+				t.Fatalf("Fetcher try to import empty block")
+			}
+			imported <- block
+		}
+	}
 
 	// Iteratively announce blocks until all are imported
 	for i := len(hashes) - 2; i >= 0; i-- {
@@ -687,16 +799,12 @@ func testEmptyBlockShortCircuit(t *testing.T, protocol int) {
 // 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 TestHashMemoryExhaustionAttack62(t *testing.T) { testHashMemoryExhaustionAttack(t, 62) }
+func TestFullHashMemoryExhaustionAttack(t *testing.T) {
-func TestHashMemoryExhaustionAttack63(t *testing.T) { testHashMemoryExhaustionAttack(t, 63) }
-func TestHashMemoryExhaustionAttack64(t *testing.T) { testHashMemoryExhaustionAttack(t, 64) }
-
-func testHashMemoryExhaustionAttack(t *testing.T, protocol int) {
 	// Create a tester with instrumented import hooks
-	tester := newTester()
+	tester := newTester(false)
 
-	imported, announces := make(chan *types.Block), int32(0)
+	imported, announces := make(chan interface{}), int32(0)
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) { imported <- block }
 	tester.fetcher.announceChangeHook = func(hash common.Hash, added bool) {
 		if added {
 			atomic.AddInt32(&announces, 1)
@@ -740,10 +848,10 @@ func testHashMemoryExhaustionAttack(t *testing.T, protocol int) {
 // system memory.
 func TestBlockMemoryExhaustionAttack(t *testing.T) {
 	// Create a tester with instrumented import hooks
-	tester := newTester()
+	tester := newTester(false)
 
-	imported, enqueued := make(chan *types.Block), int32(0)
+	imported, enqueued := make(chan interface{}), int32(0)
-	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.importedHook = func(header *types.Header, block *types.Block) { imported <- block }
 	tester.fetcher.queueChangeHook = func(hash common.Hash, added bool) {
 		if added {
 			atomic.AddInt32(&enqueued, 1)
@@ -763,7 +871,7 @@ func TestBlockMemoryExhaustionAttack(t *testing.T) {
 	}
 	// Try to feed all the attacker blocks make sure only a limited batch is accepted
 	for _, block := range attack {
-		tester.fetcher.Enqueue("attacker", block)
+		tester.fetcher.EnqueueBlock("attacker", block)
 	}
 	time.Sleep(200 * time.Millisecond)
 	if queued := atomic.LoadInt32(&enqueued); queued != blockLimit {
@@ -771,19 +879,19 @@ func TestBlockMemoryExhaustionAttack(t *testing.T) {
 	}
 	// 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]])
+		tester.fetcher.EnqueueBlock("valid", blocks[hashes[len(hashes)-3-i]])
 	}
 	time.Sleep(100 * time.Millisecond)
 	if queued := atomic.LoadInt32(&enqueued); 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]])
+	tester.fetcher.EnqueueBlock("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]])
+		tester.fetcher.EnqueueBlock("valid", blocks[hashes[len(hashes)-2-i]])
 		verifyImportEvent(t, imported, true)
 	}
 	verifyImportDone(t, imported)

eth/handler.go

@@ -211,7 +211,7 @@ func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, ne
 		}
 		return n, err
 	}
-	manager.fetcher = fetcher.New(blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, inserter, manager.removePeer)
+	manager.fetcher = fetcher.New(false, nil, blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, nil, inserter, manager.removePeer)
 
 	return manager, nil
 }
@@ -683,7 +683,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 
 		// Mark the peer as owning the block and schedule it for import
 		p.MarkBlock(request.Block.Hash())
-		pm.fetcher.Enqueue(p.id, request.Block)
+		pm.fetcher.EnqueueBlock(p.id, request.Block)
 
 		// Assuming the block is importable by the peer, but possibly not yet done so,
 		// calculate the head hash and TD that the peer truly must have.

les/client.go

@@ -226,6 +226,7 @@ func (s *LightEthereum) Start(srvr *p2p.Server) error {
 	// Start bloom request workers.
 	s.wg.Add(bloomServiceThreads)
 	s.startBloomHandlers(params.BloomBitsBlocksClient)
+	s.handler.start()
 
 	s.netRPCService = ethapi.NewPublicNetAPI(srvr, s.config.NetworkId)
 

les/client_handler.go

@@ -60,10 +60,14 @@ func newClientHandler(ulcConfig *eth.ULCConfig, backend *LightEthereum) *clientH
 	return handler
 }
 
+func (h *clientHandler) start() {
+	h.fetcher.start()
+}
+
 func (h *clientHandler) stop() {
 	close(h.closeCh)
 	h.downloader.Terminate()
-	h.fetcher.close()
+	h.fetcher.stop()
 	h.wg.Wait()
 }
 
@@ -172,6 +176,9 @@ func (h *clientHandler) handleMsg(p *serverPeer) error {
 				p.Log().Trace("Valid announcement signature")
 			}
 			p.Log().Trace("Announce message content", "number", req.Number, "hash", req.Hash, "td", req.Td, "reorg", req.ReorgDepth)
+
+			// Update peer head information first
+			p.updateHead(req.Hash, req.Number, req.Td)
 			h.fetcher.announce(p, &req)
 		}
 	case BlockHeadersMsg:
@@ -183,11 +190,16 @@ func (h *clientHandler) handleMsg(p *serverPeer) error {
 		if err := msg.Decode(&resp); err != nil {
 			return errResp(ErrDecode, "msg %v: %v", msg, err)
 		}
+		headers := resp.Headers
 		p.fcServer.ReceivedReply(resp.ReqID, resp.BV)
-		if h.fetcher.requestedID(resp.ReqID) {
+
-			h.fetcher.deliverHeaders(p, resp.ReqID, resp.Headers)
+		// Filter out any explicitly requested headers, deliver the rest to the downloader
-		} else {
+		filter := len(headers) == 1
-			if err := h.downloader.DeliverHeaders(p.id, resp.Headers); err != nil {
+		if filter {
+			headers = h.fetcher.deliverHeaders(p, resp.ReqID, resp.Headers)
+		}
+		if len(headers) != 0 || !filter {
+			if err := h.downloader.DeliverHeaders(p.id, headers); err != nil {
 				log.Debug("Failed to deliver headers", "err", err)
 			}
 		}

les/fetcher_test.go

@@ -0,0 +1,284 @@
+// Copyright 2019 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 les
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+// verifyImportEvent verifies that one single event arrive on an import channel.
+func verifyImportEvent(t *testing.T, imported chan interface{}, arrive bool) {
+	if arrive {
+		select {
+		case <-imported:
+		case <-time.After(time.Second):
+			t.Fatalf("import timeout")
+		}
+	} else {
+		select {
+		case <-imported:
+			t.Fatalf("import invoked")
+		case <-time.After(20 * time.Millisecond):
+		}
+	}
+}
+
+// verifyImportDone verifies that no more events are arriving on an import channel.
+func verifyImportDone(t *testing.T, imported chan interface{}) {
+	select {
+	case <-imported:
+		t.Fatalf("extra block imported")
+	case <-time.After(50 * time.Millisecond):
+	}
+}
+
+// verifyChainHeight verifies the chain height is as expected.
+func verifyChainHeight(t *testing.T, fetcher *lightFetcher, height uint64) {
+	local := fetcher.chain.CurrentHeader().Number.Uint64()
+	if local != height {
+		t.Fatalf("chain height mismatch, got %d, want %d", local, height)
+	}
+}
+
+func TestSequentialAnnouncementsLes2(t *testing.T) { testSequentialAnnouncements(t, 2) }
+func TestSequentialAnnouncementsLes3(t *testing.T) { testSequentialAnnouncements(t, 3) }
+
+func testSequentialAnnouncements(t *testing.T, protocol int) {
+	s, c, teardown := newClientServerEnv(t, 4, protocol, nil, nil, false, false)
+	defer teardown()
+
+	// Create connected peer pair.
+	c.handler.fetcher.ignoreAnnounce = true // Ignore the first announce from peer which can trigger a resync.
+	p1, err1, _, err2 := newTestPeerPair("peer", protocol, s.handler, c.handler)
+	select {
+	case <-time.After(time.Millisecond * 100):
+	case err := <-err1:
+		t.Fatalf("peer 1 handshake error: %v", err)
+	case err := <-err2:
+		t.Fatalf("peer 2 handshake error: %v", err)
+	}
+	c.handler.fetcher.ignoreAnnounce = false
+
+	importCh := make(chan interface{})
+	c.handler.fetcher.newHeadHook = func(header *types.Header) {
+		importCh <- header
+	}
+	for i := uint64(1); i <= s.backend.Blockchain().CurrentHeader().Number.Uint64(); i++ {
+		header := s.backend.Blockchain().GetHeaderByNumber(i)
+		hash, number := header.Hash(), header.Number.Uint64()
+		td := rawdb.ReadTd(s.db, hash, number)
+
+		announce := announceData{hash, number, td, 0, nil}
+		if p1.cpeer.announceType == announceTypeSigned {
+			announce.sign(s.handler.server.privateKey)
+		}
+		p1.cpeer.sendAnnounce(announce)
+		verifyImportEvent(t, importCh, true)
+	}
+	verifyImportDone(t, importCh)
+	verifyChainHeight(t, c.handler.fetcher, 4)
+}
+
+func TestGappedAnnouncementsLes2(t *testing.T) { testGappedAnnouncements(t, 2) }
+func TestGappedAnnouncementsLes3(t *testing.T) { testGappedAnnouncements(t, 3) }
+
+func testGappedAnnouncements(t *testing.T, protocol int) {
+	s, c, teardown := newClientServerEnv(t, 4, protocol, nil, nil, false, false)
+	defer teardown()
+
+	// Create connected peer pair.
+	c.handler.fetcher.ignoreAnnounce = true // Ignore the first announce from peer which can trigger a resync.
+	p1, err1, _, err2 := newTestPeerPair("peer", protocol, s.handler, c.handler)
+	select {
+	case <-time.After(time.Millisecond * 100):
+	case err := <-err1:
+		t.Fatalf("peer 1 handshake error: %v", err)
+	case err := <-err2:
+		t.Fatalf("peer 2 handshake error: %v", err)
+	}
+	c.handler.fetcher.ignoreAnnounce = false
+
+	// Prepare announcement by latest header.
+	latest := s.backend.Blockchain().CurrentHeader()
+	hash, number := latest.Hash(), latest.Number.Uint64()
+	td := rawdb.ReadTd(s.db, hash, number)
+
+	// Sign the announcement if necessary.
+	announce := announceData{hash, number, td, 0, nil}
+	if p1.cpeer.announceType == announceTypeSigned {
+		announce.sign(s.handler.server.privateKey)
+	}
+	p1.cpeer.sendAnnounce(announce)
+	time.Sleep(10 * time.Millisecond)
+	verifyChainHeight(t, c.handler.fetcher, 4)
+}
+
+func TestTrustedAnnouncementsLes2(t *testing.T) { testTrustedAnnouncement(t, 2) }
+func TestTrustedAnnouncementsLes3(t *testing.T) { testTrustedAnnouncement(t, 3) }
+
+func testTrustedAnnouncement(t *testing.T, protocol int) {
+	var (
+		servers   []*testServer
+		teardowns []func()
+		nodes     []*enode.Node
+		ids       []string
+		cpeers    []*clientPeer
+		speers    []*serverPeer
+	)
+	for i := 0; i < 10; i++ {
+		s, n, teardown := newTestServerPeer(t, 10, protocol)
+
+		servers = append(servers, s)
+		nodes = append(nodes, n)
+		teardowns = append(teardowns, teardown)
+
+		// A half of them are trusted servers.
+		if i < 5 {
+			ids = append(ids, n.String())
+		}
+	}
+	config := &eth.ULCConfig{
+		MinTrustedFraction: 60, // At least 3 approvals
+		TrustedServers:     ids,
+	}
+	_, c, teardown := newClientServerEnv(t, 0, protocol, nil, config, false, false)
+	defer teardown()
+	defer func() {
+		for i := 0; i < len(teardowns); i++ {
+			teardowns[i]()
+		}
+	}()
+
+	c.handler.fetcher.ignoreAnnounce = true // Ignore the first announce from peer which can trigger a resync.
+
+	// Connect all server instances.
+	for i := 0; i < len(servers); i++ {
+		sp, cp, err := connect(servers[i].handler, nodes[i].ID(), c.handler, protocol)
+		if err != nil {
+			t.Fatalf("connect server and client failed, err %s", err)
+		}
+		cpeers = append(cpeers, cp)
+		speers = append(speers, sp)
+	}
+	c.handler.fetcher.ignoreAnnounce = false
+
+	check := func(height []uint64, expected uint64, callback func()) {
+		for i := 0; i < len(height); i++ {
+			for j := 0; j < len(servers); j++ {
+				h := servers[j].backend.Blockchain().GetHeaderByNumber(height[i])
+				hash, number := h.Hash(), h.Number.Uint64()
+				td := rawdb.ReadTd(servers[j].db, hash, number)
+
+				// Sign the announcement if necessary.
+				announce := announceData{hash, number, td, 0, nil}
+				p := cpeers[j]
+				if p.announceType == announceTypeSigned {
+					announce.sign(servers[j].handler.server.privateKey)
+				}
+				p.sendAnnounce(announce)
+
+				if j < 2 {
+					time.Sleep(10 * time.Millisecond) // Ensure the announcement has been processed.
+					if !c.handler.fetcher.queryAnnounced(speers[j], hash) {
+						t.Fatalf("the announcement from server peer %d should be kept", j+1)
+					}
+				} else if j == 2 {
+					// The block should be imported
+				}
+			}
+		}
+		if callback != nil {
+			callback()
+		}
+		time.Sleep(10 * time.Millisecond) // Ensure the announcement has been processed.
+		verifyChainHeight(t, c.handler.fetcher, expected)
+	}
+	check([]uint64{1}, 1, nil) // Sequential announcements
+	check([]uint64{4}, 4, nil) // ULC-style light syncing, rollback untrusted headers
+
+	done := make(chan struct{})
+	c.handler.fetcher.syncingHook = func() { <-done }
+	check([]uint64{6, 8}, 8, func() { done <- struct{}{} }) // ULC-style light syncing, keep the later trusted announces.
+
+	c.handler.fetcher.syncingHook = nil
+	check([]uint64{10}, 10, nil) // Sync the whole chain.
+}
+
+func TestAnnounceDelayLes2(t *testing.T) { testAnnounceDelay(t, 2) }
+func TestAnnounceDelayLes3(t *testing.T) { testAnnounceDelay(t, 3) }
+
+func testAnnounceDelay(t *testing.T, protocol int) {
+	var (
+		servers   []*testServer
+		teardowns []func()
+		nodes     []*enode.Node
+		cpeers    []*clientPeer
+		speers    []*serverPeer
+	)
+	for i := 0; i < 5; i++ {
+		s, n, teardown := newTestServerPeer(t, 10, protocol)
+
+		servers = append(servers, s)
+		nodes = append(nodes, n)
+		teardowns = append(teardowns, teardown)
+	}
+	_, c, teardown := newClientServerEnv(t, 0, protocol, nil, nil, false, false)
+	defer teardown()
+	defer func() {
+		for i := 0; i < len(teardowns); i++ {
+			teardowns[i]()
+		}
+	}()
+
+	c.handler.fetcher.ignoreAnnounce = true // Ignore the first announce from peer which can trigger a resync.
+	// Connect all server instances.
+	for i := 0; i < len(servers); i++ {
+		sp, cp, err := connect(servers[i].handler, nodes[i].ID(), c.handler, protocol)
+		if err != nil {
+			t.Fatalf("connect server and client failed, err %s", err)
+		}
+		cpeers = append(cpeers, cp)
+		speers = append(speers, sp)
+	}
+	c.handler.fetcher.ignoreAnnounce = false
+
+	delays := make(map[*serverPeer]time.Duration)
+	c.handler.fetcher.addDelayHook = func(p *serverPeer, delay time.Duration) { delays[p] = delay }
+
+	for i := 0; i < 2; i++ {
+		h := servers[i].backend.Blockchain().GetHeaderByNumber(1)
+		hash, number := h.Hash(), h.Number.Uint64()
+		td := rawdb.ReadTd(servers[i].db, hash, number)
+
+		announce := announceData{hash, number, td, 0, nil}
+		p := cpeers[i]
+		if p.announceType == announceTypeSigned {
+			announce.sign(servers[i].handler.server.privateKey)
+		}
+		p.sendAnnounce(announce)
+	}
+	time.Sleep(10 * time.Millisecond)
+	if d, exist := delays[speers[1]]; !exist || d > time.Millisecond {
+		t.Fatalf("the second announcement should be confirmed soon")
+	}
+}

les/odr_requests.go

@@ -84,7 +84,7 @@ func (r *BlockRequest) GetCost(peer *serverPeer) uint64 {
 
 // CanSend tells if a certain peer is suitable for serving the given request
 func (r *BlockRequest) CanSend(peer *serverPeer) bool {
-	return peer.HasBlock(r.Hash, r.Number, false)
+	return peer.hasBlock(r.Hash, r.Number, false)
 }
 
 // Request sends an ODR request to the LES network (implementation of LesOdrRequest)
@@ -140,7 +140,7 @@ func (r *ReceiptsRequest) GetCost(peer *serverPeer) uint64 {
 
 // CanSend tells if a certain peer is suitable for serving the given request
 func (r *ReceiptsRequest) CanSend(peer *serverPeer) bool {
-	return peer.HasBlock(r.Hash, r.Number, false)
+	return peer.hasBlock(r.Hash, r.Number, false)
 }
 
 // Request sends an ODR request to the LES network (implementation of LesOdrRequest)
@@ -197,7 +197,7 @@ func (r *TrieRequest) GetCost(peer *serverPeer) uint64 {
 
 // CanSend tells if a certain peer is suitable for serving the given request
 func (r *TrieRequest) CanSend(peer *serverPeer) bool {
-	return peer.HasBlock(r.Id.BlockHash, r.Id.BlockNumber, true)
+	return peer.hasBlock(r.Id.BlockHash, r.Id.BlockNumber, true)
 }
 
 // Request sends an ODR request to the LES network (implementation of LesOdrRequest)
@@ -251,7 +251,7 @@ func (r *CodeRequest) GetCost(peer *serverPeer) uint64 {
 
 // CanSend tells if a certain peer is suitable for serving the given request
 func (r *CodeRequest) CanSend(peer *serverPeer) bool {
-	return peer.HasBlock(r.Id.BlockHash, r.Id.BlockNumber, true)
+	return peer.hasBlock(r.Id.BlockHash, r.Id.BlockNumber, true)
 }
 
 // Request sends an ODR request to the LES network (implementation of LesOdrRequest)

les/odr_test.go

@@ -213,13 +213,13 @@ func testOdr(t *testing.T, protocol int, expFail uint64, checkCached bool, fn od
 
 	// expect retrievals to fail (except genesis block) without a les peer
 	client.handler.backend.peers.lock.Lock()
-	client.peer.speer.hasBlock = func(common.Hash, uint64, bool) bool { return false }
+	client.peer.speer.hasBlockCallback = func() bool { return false }
 	client.handler.backend.peers.lock.Unlock()
 	test(expFail)
 
 	// expect all retrievals to pass
 	client.handler.backend.peers.lock.Lock()
-	client.peer.speer.hasBlock = func(common.Hash, uint64, bool) bool { return true }
+	client.peer.speer.hasBlockCallback = nil
 	client.handler.backend.peers.lock.Unlock()
 	test(5)
 

les/peer.go

@@ -311,8 +311,8 @@ type serverPeer struct {
 	updateCount uint64
 	updateTime  mclock.AbsTime
 
-	// Callbacks
+	// Test Hooks
-	hasBlock func(common.Hash, uint64, bool) bool // Used to determine whether the server has the specified block.
+	hasBlockCallback func() bool
 }
 
 func newServerPeer(version int, network uint64, trusted bool, p *p2p.Peer, rw p2p.MsgReadWriter) *serverPeer {
@@ -475,11 +475,14 @@ func (p *serverPeer) getTxRelayCost(amount, size int) uint64 {
 	return cost
 }
 
-// HasBlock checks if the peer has a given block
+// hasBlock checks if the peer has a given block
-func (p *serverPeer) HasBlock(hash common.Hash, number uint64, hasState bool) bool {
+func (p *serverPeer) hasBlock(hash common.Hash, number uint64, hasState bool) bool {
 	p.lock.RLock()
 	defer p.lock.RUnlock()
 
+	if p.hasBlockCallback != nil {
+		return p.hasBlockCallback()
+	}
 	head := p.headInfo.Number
 	var since, recent uint64
 	if hasState {
@@ -489,9 +492,7 @@ func (p *serverPeer) HasBlock(hash common.Hash, number uint64, hasState bool) bo
 		since = p.chainSince
 		recent = p.chainRecent
 	}
-	hasBlock := p.hasBlock
+	return head >= number && number >= since && (recent == 0 || number+recent+4 > head)
-
-	return head >= number && number >= since && (recent == 0 || number+recent+4 > head) && hasBlock != nil && hasBlock(hash, number, hasState)
 }
 
 // updateFlowControl updates the flow control parameters belonging to the server
@@ -516,6 +517,15 @@ func (p *serverPeer) updateFlowControl(update keyValueMap) {
 	}
 }
 
+// updateHead updates the head information based on the announcement from
+// the peer.
+func (p *serverPeer) updateHead(hash common.Hash, number uint64, td *big.Int) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	p.headInfo = blockInfo{Hash: hash, Number: number, Td: td}
+}
+
 // Handshake executes the les protocol handshake, negotiating version number,
 // network IDs, difficulties, head and genesis blocks.
 func (p *serverPeer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis common.Hash, server *LesServer) error {

les/test_helper.go

@@ -23,6 +23,7 @@ import (
 	"context"
 	"crypto/rand"
 	"math/big"
+	"net"
 	"testing"
 	"time"
 
@@ -221,6 +222,7 @@ func newTestClientHandler(backend *backends.SimulatedBackend, odr *LesOdr, index
 	if client.registrar != nil {
 		client.registrar.start(backend)
 	}
+	client.handler.start()
 	return client.handler
 }
 
@@ -280,6 +282,8 @@ func newTestServerHandler(blocks int, indexers []*core.ChainIndexer, db ethdb.Da
 		},
 		fcManager: flowcontrol.NewClientManager(nil, clock),
 	}
+	key, _ := crypto.GenerateKey()
+	server.privateKey = key
 	server.costTracker, server.minCapacity = newCostTracker(db, server.config, nil)
 	server.costTracker.costListHook = func() RequestCostList { return testCostList(0) } // Disable flow control mechanism.
 	server.handler = newServerHandler(server, simulation.Blockchain(), db, txpool, nil, func() bool { return true })
@@ -349,14 +353,13 @@ func (p *testPeer) close() {
 
 func newTestPeerPair(name string, version int, server *serverHandler, client *clientHandler) (*testPeer, <-chan error, *testPeer, <-chan error) {
 	// Create a message pipe to communicate through
-	app, net := p2p.MsgPipe()
+	app, s := p2p.MsgPipe()
 
 	// Generate a random id and create the peer
-	var id enode.ID
+	en := enode.NewV4(&server.server.privateKey.PublicKey, net.ParseIP("127.0.0.1"), 35000, 35000)
-	rand.Read(id[:])
 
-	peer1 := newClientPeer(version, NetworkId, p2p.NewPeer(id, name, nil), net)
+	peer1 := newClientPeer(version, NetworkId, p2p.NewPeer(en.ID(), name, nil), s)
-	peer2 := newServerPeer(version, NetworkId, false, p2p.NewPeer(id, name, nil), app)
+	peer2 := newServerPeer(version, NetworkId, false, p2p.NewPeer(en.ID(), name, nil), app)
 
 	// Start the peer on a new thread
 	errc1 := make(chan error, 1)
@@ -375,7 +378,7 @@ func newTestPeerPair(name string, version int, server *serverHandler, client *cl
 		case errc1 <- client.handle(peer2):
 		}
 	}()
-	return &testPeer{cpeer: peer1, net: net, app: app}, errc1, &testPeer{speer: peer2, net: app, app: net}, errc2
+	return &testPeer{cpeer: peer1, net: s, app: app}, errc1, &testPeer{speer: peer2, net: app, app: s}, errc2
 }
 
 // handshake simulates a trivial handshake that expects the same state from the

les/txrelay.go

@@ -62,14 +62,18 @@ func (self *lesTxRelay) registerPeer(p *serverPeer) {
 	self.lock.Lock()
 	defer self.lock.Unlock()
 
-	self.peerList = self.ps.allServerPeers()
+	self.peerList = append(self.peerList, p)
 }
 
 func (self *lesTxRelay) unregisterPeer(p *serverPeer) {
 	self.lock.Lock()
 	defer self.lock.Unlock()
 
-	self.peerList = self.ps.allServerPeers()
+	for index, peer := range self.peerList {
+		if peer == p {
+			self.peerList = append(self.peerList[:index], self.peerList[index+1:]...)
+		}
+	}
 }
 
 // send sends a list of transactions to at most a given number of peers at

light/lightchain.go

@@ -256,7 +256,7 @@ func (lc *LightChain) GetBodyRLP(ctx context.Context, hash common.Hash) (rlp.Raw
 	return body, nil
 }
 
-// HasBlock checks if a block is fully present in the database or not, caching
+// hasBlock checks if a block is fully present in the database or not, caching
 // it if present.
 func (lc *LightChain) HasBlock(hash common.Hash, number uint64) bool {
 	blk, _ := lc.GetBlock(NoOdr, hash, number)