path: root/eth/downloader/downloader_test.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package downloader

import (
    "errors"
    "fmt"
    "math/big"
    "sync"
    "sync/atomic"
    "testing"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/params"
    "github.com/ethereum/go-ethereum/trie"
)

var (
    testdb, _   = ethdb.NewMemDatabase()
    testKey, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
    testAddress = crypto.PubkeyToAddress(testKey.PublicKey)
    genesis     = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
)

// Reduce the block cache limit, otherwise the tests will be very heavy.
func init() {
    blockCacheLimit = 1024
}

// makeChain creates a chain of n blocks starting at and including parent.
// the returned hash chain is ordered head->parent. In addition, every 3rd block
// contains a transaction and every 5th an uncle to allow testing correct block
// reassembly.
func makeChain(n int, seed byte, parent *types.Block, parentReceipts types.Receipts) ([]common.Hash, map[common.Hash]*types.Header, map[common.Hash]*types.Block, map[common.Hash]types.Receipts) {
    // Generate the block chain
    blocks, receipts := core.GenerateChain(parent, testdb, n, func(i int, block *core.BlockGen) {
        block.SetCoinbase(common.Address{seed})

        // If the block number is multiple of 3, send a bonus transaction to the miner
        if parent == genesis && i%3 == 0 {
            tx, err := types.NewTransaction(block.TxNonce(testAddress), common.Address{seed}, big.NewInt(1000), params.TxGas, nil, nil).SignECDSA(testKey)
            if err != nil {
                panic(err)
            }
            block.AddTx(tx)
        }
        // If the block number is a multiple of 5, add a bonus uncle to the block
        if i > 0 && i%5 == 0 {
            block.AddUncle(&types.Header{
                ParentHash: block.PrevBlock(i - 1).Hash(),
                Number:     big.NewInt(block.Number().Int64() - 1),
            })
        }
    })
    // Convert the block-chain into a hash-chain and header/block maps
    hashes := make([]common.Hash, n+1)
    hashes[len(hashes)-1] = parent.Hash()

    headerm := make(map[common.Hash]*types.Header, n+1)
    headerm[parent.Hash()] = parent.Header()

    blockm := make(map[common.Hash]*types.Block, n+1)
    blockm[parent.Hash()] = parent

    receiptm := make(map[common.Hash]types.Receipts, n+1)
    receiptm[parent.Hash()] = parentReceipts

    for i, b := range blocks {
        hashes[len(hashes)-i-2] = b.Hash()
        headerm[b.Hash()] = b.Header()
        blockm[b.Hash()] = b
        receiptm[b.Hash()] = receipts[i]
    }
    return hashes, headerm, blockm, receiptm
}

// makeChainFork creates two chains of length n, such that h1[:f] and
// h2[:f] are different but have a common suffix of length n-f.
func makeChainFork(n, f int, parent *types.Block, parentReceipts types.Receipts) ([]common.Hash, []common.Hash, map[common.Hash]*types.Header, map[common.Hash]*types.Header, map[common.Hash]*types.Block, map[common.Hash]*types.Block, map[common.Hash]types.Receipts, map[common.Hash]types.Receipts) {
    // Create the common suffix
    hashes, headers, blocks, receipts := makeChain(n-f, 0, parent, parentReceipts)

    // Create the forks
    hashes1, headers1, blocks1, receipts1 := makeChain(f, 1, blocks[hashes[0]], receipts[hashes[0]])
    hashes1 = append(hashes1, hashes[1:]...)

    hashes2, headers2, blocks2, receipts2 := makeChain(f, 2, blocks[hashes[0]], receipts[hashes[0]])
    hashes2 = append(hashes2, hashes[1:]...)

    for hash, header := range headers {
        headers1[hash] = header
        headers2[hash] = header
    }
    for hash, block := range blocks {
        blocks1[hash] = block
        blocks2[hash] = block
    }
    for hash, receipt := range receipts {
        receipts1[hash] = receipt
        receipts2[hash] = receipt
    }
    return hashes1, hashes2, headers1, headers2, blocks1, blocks2, receipts1, receipts2
}

// downloadTester is a test simulator for mocking out local block chain.
type downloadTester struct {
    stateDb    ethdb.Database
    downloader *Downloader

    ownHashes   []common.Hash                  // Hash chain belonging to the tester
    ownHeaders  map[common.Hash]*types.Header  // Headers belonging to the tester
    ownBlocks   map[common.Hash]*types.Block   // Blocks belonging to the tester
    ownReceipts map[common.Hash]types.Receipts // Receipts belonging to the tester
    ownChainTd  map[common.Hash]*big.Int       // Total difficulties of the blocks in the local chain

    peerHashes   map[string][]common.Hash                  // Hash chain belonging to different test peers
    peerHeaders  map[string]map[common.Hash]*types.Header  // Headers belonging to different test peers
    peerBlocks   map[string]map[common.Hash]*types.Block   // Blocks belonging to different test peers
    peerReceipts map[string]map[common.Hash]types.Receipts // Receipts belonging to different test peers
    peerChainTds map[string]map[common.Hash]*big.Int       // Total difficulties of the blocks in the peer chains

    lock sync.RWMutex
}

// newTester creates a new downloader test mocker.
func newTester() *downloadTester {
    tester := &downloadTester{
        ownHashes:    []common.Hash{genesis.Hash()},
        ownHeaders:   map[common.Hash]*types.Header{genesis.Hash(): genesis.Header()},
        ownBlocks:    map[common.Hash]*types.Block{genesis.Hash(): genesis},
        ownReceipts:  map[common.Hash]types.Receipts{genesis.Hash(): nil},
        ownChainTd:   map[common.Hash]*big.Int{genesis.Hash(): genesis.Difficulty()},
        peerHashes:   make(map[string][]common.Hash),
        peerHeaders:  make(map[string]map[common.Hash]*types.Header),
        peerBlocks:   make(map[string]map[common.Hash]*types.Block),
        peerReceipts: make(map[string]map[common.Hash]types.Receipts),
        peerChainTds: make(map[string]map[common.Hash]*big.Int),
    }
    tester.stateDb, _ = ethdb.NewMemDatabase()
    tester.stateDb.Put(genesis.Root().Bytes(), []byte{0x00})

    tester.downloader = New(tester.stateDb, new(event.TypeMux), tester.hasHeader, tester.hasBlock, tester.getHeader,
        tester.getBlock, tester.headHeader, tester.headBlock, tester.headFastBlock, tester.commitHeadBlock, tester.getTd,
        tester.insertHeaders, tester.insertBlocks, tester.insertReceipts, tester.rollback, tester.dropPeer)

    return tester
}

// sync starts synchronizing with a remote peer, blocking until it completes.
func (dl *downloadTester) sync(id string, td *big.Int, mode SyncMode) error {
    dl.lock.RLock()
    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 diff, ok := dl.peerChainTds[id][hash]; ok {
            td = diff
        }
    }
    dl.lock.RUnlock()
    return dl.downloader.synchronise(id, hash, td, mode)
}

// hasHeader checks if a header is present in the testers canonical chain.
func (dl *downloadTester) hasHeader(hash common.Hash) bool {
    return dl.getHeader(hash) != nil
}

// hasBlock checks if a block and associated state is present in the testers canonical chain.
func (dl *downloadTester) hasBlock(hash common.Hash) bool {
    block := dl.getBlock(hash)
    if block == nil {
        return false
    }
    _, err := dl.stateDb.Get(block.Root().Bytes())
    return err == nil
}

// getHeader retrieves a header from the testers canonical chain.
func (dl *downloadTester) getHeader(hash common.Hash) *types.Header {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    return dl.ownHeaders[hash]
}

// getBlock retrieves a block from the testers canonical chain.
func (dl *downloadTester) getBlock(hash common.Hash) *types.Block {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    return dl.ownBlocks[hash]
}

// headHeader retrieves the current head header from the canonical chain.
func (dl *downloadTester) headHeader() *types.Header {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    for i := len(dl.ownHashes) - 1; i >= 0; i-- {
        if header := dl.ownHeaders[dl.ownHashes[i]]; header != nil {
            return header
        }
    }
    return genesis.Header()
}

// headBlock retrieves the current head block from the canonical chain.
func (dl *downloadTester) headBlock() *types.Block {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    for i := len(dl.ownHashes) - 1; i >= 0; i-- {
        if block := dl.ownBlocks[dl.ownHashes[i]]; block != nil {
            if _, err := dl.stateDb.Get(block.Root().Bytes()); err == nil {
                return block
            }
        }
    }
    return genesis
}

// headFastBlock retrieves the current head fast-sync block from the canonical chain.
func (dl *downloadTester) headFastBlock() *types.Block {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    for i := len(dl.ownHashes) - 1; i >= 0; i-- {
        if block := dl.ownBlocks[dl.ownHashes[i]]; block != nil {
            return block
        }
    }
    return genesis
}

// commitHeadBlock manually sets the head block to a given hash.
func (dl *downloadTester) commitHeadBlock(hash common.Hash) error {
    // For now only check that the state trie is correct
    if block := dl.getBlock(hash); block != nil {
        _, err := trie.NewSecure(block.Root(), dl.stateDb)
        return err
    }
    return fmt.Errorf("non existent block: %x", hash[:4])
}

// getTd retrieves the block's total difficulty from the canonical chain.
func (dl *downloadTester) getTd(hash common.Hash) *big.Int {
    dl.lock.RLock()
    defer dl.lock.RUnlock()

    return dl.ownChainTd[hash]
}

// insertHeaders injects a new batch of headers into the simulated chain.
func (dl *downloadTester) insertHeaders(headers []*types.Header, checkFreq int) (int, error) {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    // Do a quick check, as the blockchain.InsertHeaderChain doesn't insert anything in case of errors
    if _, ok := dl.ownHeaders[headers[0].ParentHash]; !ok {
        return 0, errors.New("unknown parent")
    }
    for i := 1; i < len(headers); i++ {
        if headers[i].ParentHash != headers[i-1].Hash() {
            return i, errors.New("unknown parent")
        }
    }
    // Do a full insert if pre-checks passed
    for i, header := range headers {
        if _, ok := dl.ownHeaders[header.Hash()]; ok {
            continue
        }
        if _, ok := dl.ownHeaders[header.ParentHash]; !ok {
            return i, errors.New("unknown parent")
        }
        dl.ownHashes = append(dl.ownHashes, header.Hash())
        dl.ownHeaders[header.Hash()] = header
        dl.ownChainTd[header.Hash()] = new(big.Int).Add(dl.ownChainTd[header.ParentHash], header.Difficulty)
    }
    return len(headers), nil
}

// insertBlocks injects a new batch of blocks into the simulated chain.
func (dl *downloadTester) insertBlocks(blocks types.Blocks) (int, error) {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    for i, block := range blocks {
        if parent, ok := dl.ownBlocks[block.ParentHash()]; !ok {
            return i, errors.New("unknown parent")
        } else if _, err := dl.stateDb.Get(parent.Root().Bytes()); err != nil {
            return i, fmt.Errorf("unknown parent state %x: %v", parent.Root(), err)
        }
        if _, ok := dl.ownHeaders[block.Hash()]; !ok {
            dl.ownHashes = append(dl.ownHashes, block.Hash())
            dl.ownHeaders[block.Hash()] = block.Header()
        }
        dl.ownBlocks[block.Hash()] = block
        dl.stateDb.Put(block.Root().Bytes(), []byte{0x00})
        dl.ownChainTd[block.Hash()] = new(big.Int).Add(dl.ownChainTd[block.ParentHash()], block.Difficulty())
    }
    return len(blocks), nil
}

// insertReceipts injects a new batch of blocks into the simulated chain.
func (dl *downloadTester) insertReceipts(blocks types.Blocks, receipts []types.Receipts) (int, error) {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    for i := 0; i < len(blocks) && i < len(receipts); i++ {
        if _, ok := dl.ownHeaders[blocks[i].Hash()]; !ok {
            return i, errors.New("unknown owner")
        }
        if _, ok := dl.ownBlocks[blocks[i].ParentHash()]; !ok {
            return i, errors.New("unknown parent")
        }
        dl.ownBlocks[blocks[i].Hash()] = blocks[i]
        dl.ownReceipts[blocks[i].Hash()] = receipts[i]
    }
    return len(blocks), nil
}

// rollback removes some recently added elements from the chain.
func (dl *downloadTester) rollback(hashes []common.Hash) {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    for i := len(hashes) - 1; i >= 0; i-- {
        if dl.ownHashes[len(dl.ownHashes)-1] == hashes[i] {
            dl.ownHashes = dl.ownHashes[:len(dl.ownHashes)-1]
        }
        delete(dl.ownChainTd, hashes[i])
        delete(dl.ownHeaders, hashes[i])
        delete(dl.ownReceipts, hashes[i])
        delete(dl.ownBlocks, hashes[i])
    }
}

// newPeer registers a new block download source into the downloader.
func (dl *downloadTester) newPeer(id string, version int, hashes []common.Hash, headers map[common.Hash]*types.Header, blocks map[common.Hash]*types.Block, receipts map[common.Hash]types.Receipts) error {
    return dl.newSlowPeer(id, version, hashes, headers, blocks, receipts, 0)
}

// newSlowPeer registers a new block download source into the downloader, with a
// specific delay time on processing the network packets sent to it, simulating
// potentially slow network IO.
func (dl *downloadTester) newSlowPeer(id string, version int, hashes []common.Hash, headers map[common.Hash]*types.Header, blocks map[common.Hash]*types.Block, receipts map[common.Hash]types.Receipts, delay time.Duration) error {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    var err error
    switch version {
    case 61:
        err = dl.downloader.RegisterPeer(id, version, hashes[0], dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, delay), dl.peerGetBlocksFn(id, delay), nil, nil, nil, nil, nil)
    case 62:
        err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), nil, nil)
    case 63:
        err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay), dl.peerGetNodeDataFn(id, delay))
    case 64:
        err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay), dl.peerGetNodeDataFn(id, delay))
    }
    if err == nil {
        // Assign the owned hashes, headers and blocks to the peer (deep copy)
        dl.peerHashes[id] = make([]common.Hash, len(hashes))
        copy(dl.peerHashes[id], hashes)

        dl.peerHeaders[id] = make(map[common.Hash]*types.Header)
        dl.peerBlocks[id] = make(map[common.Hash]*types.Block)
        dl.peerReceipts[id] = make(map[common.Hash]types.Receipts)
        dl.peerChainTds[id] = make(map[common.Hash]*big.Int)

        genesis := hashes[len(hashes)-1]
        if header := headers[genesis]; header != nil {
            dl.peerHeaders[id][genesis] = header
            dl.peerChainTds[id][genesis] = header.Difficulty
        }
        if block := blocks[genesis]; block != nil {
            dl.peerBlocks[id][genesis] = block
            dl.peerChainTds[id][genesis] = block.Difficulty()
        }

        for i := len(hashes) - 2; i >= 0; i-- {
            hash := hashes[i]

            if header, ok := headers[hash]; ok {
                dl.peerHeaders[id][hash] = header
                if _, ok := dl.peerHeaders[id][header.ParentHash]; ok {
                    dl.peerChainTds[id][hash] = new(big.Int).Add(header.Difficulty, dl.peerChainTds[id][header.ParentHash])
                }
            }
            if block, ok := blocks[hash]; ok {
                dl.peerBlocks[id][hash] = block
                if _, ok := dl.peerBlocks[id][block.ParentHash()]; ok {
                    dl.peerChainTds[id][hash] = new(big.Int).Add(block.Difficulty(), dl.peerChainTds[id][block.ParentHash()])
                }
            }
            if receipt, ok := receipts[hash]; ok {
                dl.peerReceipts[id][hash] = receipt
            }
        }
    }
    return err
}

// dropPeer simulates a hard peer removal from the connection pool.
func (dl *downloadTester) dropPeer(id string) {
    dl.lock.Lock()
    defer dl.lock.Unlock()

    delete(dl.peerHashes, id)
    delete(dl.peerHeaders, id)
    delete(dl.peerBlocks, id)
    delete(dl.peerChainTds, id)

    dl.downloader.UnregisterPeer(id)
}

// peerGetRelHashesFn constructs a GetHashes function associated with a specific
// peer in the download tester. The returned function can be used to retrieve
// batches of hashes from the particularly requested peer.
func (dl *downloadTester) peerGetRelHashesFn(id string, delay time.Duration) func(head common.Hash) error {
    return func(head common.Hash) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        // Gather the next batch of hashes
        hashes := dl.peerHashes[id]
        result := make([]common.Hash, 0, MaxHashFetch)
        for i, hash := range hashes {
            if hash == head {
                i++
                for len(result) < cap(result) && i < len(hashes) {
                    result = append(result, hashes[i])
                    i++
                }
                break
            }
        }
        // Delay delivery a bit to allow attacks to unfold
        go func() {
            time.Sleep(time.Millisecond)
            dl.downloader.DeliverHashes(id, result)
        }()
        return nil
    }
}

// peerGetAbsHashesFn constructs a GetHashesFromNumber function associated with
// a particular peer in the download tester. The returned function can be used to
// retrieve batches of hashes from the particularly requested peer.
func (dl *downloadTester) peerGetAbsHashesFn(id string, delay time.Duration) func(uint64, int) error {
    return func(head uint64, count int) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        // Gather the next batch of hashes
        hashes := dl.peerHashes[id]
        result := make([]common.Hash, 0, count)
        for i := 0; i < count && len(hashes)-int(head)-1-i >= 0; i++ {
            result = append(result, hashes[len(hashes)-int(head)-1-i])
        }
        // Delay delivery a bit to allow attacks to unfold
        go func() {
            time.Sleep(time.Millisecond)
            dl.downloader.DeliverHashes(id, result)
        }()
        return nil
    }
}

// peerGetBlocksFn constructs a getBlocks function associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of blocks from the particularly requested peer.
func (dl *downloadTester) peerGetBlocksFn(id string, delay time.Duration) func([]common.Hash) error {
    return func(hashes []common.Hash) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        blocks := dl.peerBlocks[id]
        result := make([]*types.Block, 0, len(hashes))
        for _, hash := range hashes {
            if block, ok := blocks[hash]; ok {
                result = append(result, block)
            }
        }
        go dl.downloader.DeliverBlocks(id, result)

        return nil
    }
}

// peerGetRelHeadersFn constructs a GetBlockHeaders function based on a hashed
// origin; associated with a particular peer in the download tester. The returned
// function can be used to retrieve batches of headers from the particular peer.
func (dl *downloadTester) peerGetRelHeadersFn(id string, delay time.Duration) func(common.Hash, int, int, bool) error {
    return func(origin common.Hash, amount int, skip int, reverse bool) error {
        // Find the canonical number of the hash
        dl.lock.RLock()
        number := uint64(0)
        for num, hash := range dl.peerHashes[id] {
            if hash == origin {
                number = uint64(len(dl.peerHashes[id]) - num - 1)
                break
            }
        }
        dl.lock.RUnlock()

        // Use the absolute header fetcher to satisfy the query
        return dl.peerGetAbsHeadersFn(id, delay)(number, amount, skip, reverse)
    }
}

// peerGetAbsHeadersFn constructs a GetBlockHeaders function based on a numbered
// origin; associated with a particular peer in the download tester. The returned
// function can be used to retrieve batches of headers from the particular peer.
func (dl *downloadTester) peerGetAbsHeadersFn(id string, delay time.Duration) func(uint64, int, int, bool) error {
    return func(origin uint64, amount int, skip int, reverse bool) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        // Gather the next batch of headers
        hashes := dl.peerHashes[id]
        headers := dl.peerHeaders[id]
        result := make([]*types.Header, 0, amount)
        for i := 0; i < amount && len(hashes)-int(origin)-1-i >= 0; i++ {
            if header, ok := headers[hashes[len(hashes)-int(origin)-1-i]]; ok {
                result = append(result, header)
            }
        }
        // Delay delivery a bit to allow attacks to unfold
        go func() {
            time.Sleep(time.Millisecond)
            dl.downloader.DeliverHeaders(id, result)
        }()
        return nil
    }
}

// peerGetBodiesFn constructs a getBlockBodies method associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of block bodies from the particularly requested peer.
func (dl *downloadTester) peerGetBodiesFn(id string, delay time.Duration) func([]common.Hash) error {
    return func(hashes []common.Hash) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        blocks := dl.peerBlocks[id]

        transactions := make([][]*types.Transaction, 0, len(hashes))
        uncles := make([][]*types.Header, 0, len(hashes))

        for _, hash := range hashes {
            if block, ok := blocks[hash]; ok {
                transactions = append(transactions, block.Transactions())
                uncles = append(uncles, block.Uncles())
            }
        }
        go dl.downloader.DeliverBodies(id, transactions, uncles)

        return nil
    }
}

// peerGetReceiptsFn constructs a getReceipts method associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of block receipts from the particularly requested peer.
func (dl *downloadTester) peerGetReceiptsFn(id string, delay time.Duration) func([]common.Hash) error {
    return func(hashes []common.Hash) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        receipts := dl.peerReceipts[id]

        results := make([][]*types.Receipt, 0, len(hashes))
        for _, hash := range hashes {
            if receipt, ok := receipts[hash]; ok {
                results = append(results, receipt)
            }
        }
        go dl.downloader.DeliverReceipts(id, results)

        return nil
    }
}

// peerGetNodeDataFn constructs a getNodeData method associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of node state data from the particularly requested peer.
func (dl *downloadTester) peerGetNodeDataFn(id string, delay time.Duration) func([]common.Hash) error {
    return func(hashes []common.Hash) error {
        time.Sleep(delay)

        dl.lock.RLock()
        defer dl.lock.RUnlock()

        results := make([][]byte, 0, len(hashes))
        for _, hash := range hashes {
            if data, err := testdb.Get(hash.Bytes()); err == nil {
                results = append(results, data)
            }
        }
        go dl.downloader.DeliverNodeData(id, results)

        return nil
    }
}

// assertOwnChain checks if the local chain contains the correct number of items
// of the various chain components.
func assertOwnChain(t *testing.T, tester *downloadTester, length int) {
    assertOwnForkedChain(t, tester, 1, []int{length})
}

// assertOwnForkedChain checks if the local forked chain contains the correct
// number of items of the various chain components.
func assertOwnForkedChain(t *testing.T, tester *downloadTester, common int, lengths []int) {
    // Initialize the counters for the first fork
    headers, blocks := lengths[0], lengths[0]

    minReceipts, maxReceipts := lengths[0]-fsMinFullBlocks-fsPivotInterval, lengths[0]-fsMinFullBlocks
    if minReceipts < 0 {
        minReceipts = 1
    }
    if maxReceipts < 0 {
        maxReceipts = 1
    }
    // Update the counters for each subsequent fork
    for _, length := range lengths[1:] {
        headers += length - common
        blocks += length - common

        minReceipts += length - common - fsMinFullBlocks - fsPivotInterval
        maxReceipts += length - common - fsMinFullBlocks
    }
    switch tester.downloader.mode {
    case FullSync:
        minReceipts, maxReceipts = 1, 1
    case LightSync:
        blocks, minReceipts, maxReceipts = 1, 1, 1
    }
    if hs := len(tester.ownHeaders); hs != headers {
        t.Fatalf("synchronised headers mismatch: have %v, want %v", hs, headers)
    }
    if bs := len(tester.ownBlocks); bs != blocks {
        t.Fatalf("synchronised blocks mismatch: have %v, want %v", bs, blocks)
    }
    if rs := len(tester.ownReceipts); rs < minReceipts || rs > maxReceipts {
        t.Fatalf("synchronised receipts mismatch: have %v, want between [%v, %v]", rs, minReceipts, maxReceipts)
    }
    // Verify the state trie too for fast syncs
    if tester.downloader.mode == FastSync {
        index := 0
        if pivot := int(tester.downloader.queue.fastSyncPivot); pivot < common {
            index = pivot
        } else {
            index = len(tester.ownHashes) - lengths[len(lengths)-1] + int(tester.downloader.queue.fastSyncPivot)
        }
        if index > 0 {
            if statedb, err := state.New(tester.ownHeaders[tester.ownHashes[index]].Root, tester.stateDb); statedb == nil || err != nil {
                t.Fatalf("state reconstruction failed: %v", err)
            }
        }
    }
}

// Tests that simple synchronization against a canonical chain works correctly.
// In this test common ancestor lookup should be short circuited and not require
// binary searching.
func TestCanonicalSynchronisation61(t *testing.T)      { testCanonicalSynchronisation(t, 61, FullSync) }
func TestCanonicalSynchronisation62(t *testing.T)      { testCanonicalSynchronisation(t, 62, FullSync) }
func TestCanonicalSynchronisation63Full(t *testing.T)  { testCanonicalSynchronisation(t, 63, FullSync) }
func TestCanonicalSynchronisation63Fast(t *testing.T)  { testCanonicalSynchronisation(t, 63, FastSync) }
func TestCanonicalSynchronisation64Full(t *testing.T)  { testCanonicalSynchronisation(t, 64, FullSync) }
func TestCanonicalSynchronisation64Fast(t *testing.T)  { testCanonicalSynchronisation(t, 64, FastSync) }
func TestCanonicalSynchronisation64Light(t *testing.T) { testCanonicalSynchronisation(t, 64, LightSync) }

func testCanonicalSynchronisation(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()
    tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)

    // Synchronise with the peer and make sure all relevant data was retrieved
    if err := tester.sync("peer", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)
}

// Tests that if a large batch of blocks are being downloaded, it is throttled
// until the cached blocks are retrieved.
func TestThrottling61(t *testing.T)     { testThrottling(t, 61, FullSync) }
func TestThrottling62(t *testing.T)     { testThrottling(t, 62, FullSync) }
func TestThrottling63Full(t *testing.T) { testThrottling(t, 63, FullSync) }
func TestThrottling63Fast(t *testing.T) { testThrottling(t, 63, FastSync) }
func TestThrottling64Full(t *testing.T) { testThrottling(t, 64, FullSync) }
func TestThrottling64Fast(t *testing.T) { testThrottling(t, 64, FastSync) }

func testThrottling(t *testing.T, protocol int, mode SyncMode) {
    // Create a long block chain to download and the tester
    targetBlocks := 8 * blockCacheLimit
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()
    tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)

    // Wrap the importer to allow stepping
    blocked, proceed := uint32(0), make(chan struct{})
    tester.downloader.chainInsertHook = func(results []*fetchResult) {
        atomic.StoreUint32(&blocked, uint32(len(results)))
        <-proceed
    }
    // Start a synchronisation concurrently
    errc := make(chan error)
    go func() {
        errc <- tester.sync("peer", nil, mode)
    }()
    // Iteratively take some blocks, always checking the retrieval count
    for {
        // Check the retrieval count synchronously (! reason for this ugly block)
        tester.lock.RLock()
        retrieved := len(tester.ownBlocks)
        tester.lock.RUnlock()
        if retrieved >= targetBlocks+1 {
            break
        }
        // Wait a bit for sync to throttle itself
        var cached, frozen int
        for start := time.Now(); time.Since(start) < 3*time.Second; {
            time.Sleep(25 * time.Millisecond)

            tester.lock.Lock()
            tester.downloader.queue.lock.Lock()
            cached = len(tester.downloader.queue.blockDonePool)
            if mode == FastSync {
                if receipts := len(tester.downloader.queue.receiptDonePool); receipts < cached {
                    if tester.downloader.queue.resultCache[receipts].Header.Number.Uint64() < tester.downloader.queue.fastSyncPivot {
                        cached = receipts
                    }
                }
            }
            frozen = int(atomic.LoadUint32(&blocked))
            retrieved = len(tester.ownBlocks)
            tester.downloader.queue.lock.Unlock()
            tester.lock.Unlock()

            if cached == blockCacheLimit || retrieved+cached+frozen == targetBlocks+1 {
                break
            }
        }
        // Make sure we filled up the cache, then exhaust it
        time.Sleep(25 * time.Millisecond) // give it a chance to screw up

        tester.lock.RLock()
        retrieved = len(tester.ownBlocks)
        tester.lock.RUnlock()
        if cached != blockCacheLimit && retrieved+cached+frozen != targetBlocks+1 {
            t.Fatalf("block count mismatch: have %v, want %v (owned %v, blocked %v, target %v)", cached, blockCacheLimit, retrieved, frozen, targetBlocks+1)
        }
        // Permit the blocked blocks to import
        if atomic.LoadUint32(&blocked) > 0 {
            atomic.StoreUint32(&blocked, uint32(0))
            proceed <- struct{}{}
        }
    }
    // Check that we haven't pulled more blocks than available
    assertOwnChain(t, tester, targetBlocks+1)
    if err := <-errc; err != nil {
        t.Fatalf("block synchronization failed: %v", err)
    }
}

// Tests that simple synchronization against a forked chain works correctly. In
// this test common ancestor lookup should *not* be short circuited, and a full
// binary search should be executed.
func TestForkedSynchronisation61(t *testing.T)      { testForkedSynchronisation(t, 61, FullSync) }
func TestForkedSynchronisation62(t *testing.T)      { testForkedSynchronisation(t, 62, FullSync) }
func TestForkedSynchronisation63Full(t *testing.T)  { testForkedSynchronisation(t, 63, FullSync) }
func TestForkedSynchronisation63Fast(t *testing.T)  { testForkedSynchronisation(t, 63, FastSync) }
func TestForkedSynchronisation64Full(t *testing.T)  { testForkedSynchronisation(t, 64, FullSync) }
func TestForkedSynchronisation64Fast(t *testing.T)  { testForkedSynchronisation(t, 64, FastSync) }
func TestForkedSynchronisation64Light(t *testing.T) { testForkedSynchronisation(t, 64, LightSync) }

func testForkedSynchronisation(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a long enough forked chain
    common, fork := MaxHashFetch, 2*MaxHashFetch
    hashesA, hashesB, headersA, headersB, blocksA, blocksB, receiptsA, receiptsB := makeChainFork(common+fork, fork, genesis, nil)

    tester := newTester()
    tester.newPeer("fork A", protocol, hashesA, headersA, blocksA, receiptsA)
    tester.newPeer("fork B", protocol, hashesB, headersB, blocksB, receiptsB)

    // Synchronise with the peer and make sure all blocks were retrieved
    if err := tester.sync("fork A", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, common+fork+1)

    // Synchronise with the second peer and make sure that fork is pulled too
    if err := tester.sync("fork B", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnForkedChain(t, tester, common+1, []int{common + fork + 1, common + fork + 1})
}

// Tests that an inactive downloader will not accept incoming hashes and blocks.
func TestInactiveDownloader61(t *testing.T) {
    t.Parallel()
    tester := newTester()

    // Check that neither hashes nor blocks are accepted
    if err := tester.downloader.DeliverHashes("bad peer", []common.Hash{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
    if err := tester.downloader.DeliverBlocks("bad peer", []*types.Block{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
}

// Tests that an inactive downloader will not accept incoming block headers and
// bodies.
func TestInactiveDownloader62(t *testing.T) {
    t.Parallel()
    tester := newTester()

    // Check that neither block headers nor bodies are accepted
    if err := tester.downloader.DeliverHeaders("bad peer", []*types.Header{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
    if err := tester.downloader.DeliverBodies("bad peer", [][]*types.Transaction{}, [][]*types.Header{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
}

// Tests that an inactive downloader will not accept incoming block headers,
// bodies and receipts.
func TestInactiveDownloader63(t *testing.T) {
    t.Parallel()
    tester := newTester()

    // Check that neither block headers nor bodies are accepted
    if err := tester.downloader.DeliverHeaders("bad peer", []*types.Header{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
    if err := tester.downloader.DeliverBodies("bad peer", [][]*types.Transaction{}, [][]*types.Header{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
    if err := tester.downloader.DeliverReceipts("bad peer", [][]*types.Receipt{}); err != errNoSyncActive {
        t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
    }
}

// Tests that a canceled download wipes all previously accumulated state.
func TestCancel61(t *testing.T)      { testCancel(t, 61, FullSync) }
func TestCancel62(t *testing.T)      { testCancel(t, 62, FullSync) }
func TestCancel63Full(t *testing.T)  { testCancel(t, 63, FullSync) }
func TestCancel63Fast(t *testing.T)  { testCancel(t, 63, FastSync) }
func TestCancel64Full(t *testing.T)  { testCancel(t, 64, FullSync) }
func TestCancel64Fast(t *testing.T)  { testCancel(t, 64, FastSync) }
func TestCancel64Light(t *testing.T) { testCancel(t, 64, LightSync) }

func testCancel(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download and the tester
    targetBlocks := blockCacheLimit - 15
    if targetBlocks >= MaxHashFetch {
        targetBlocks = MaxHashFetch - 15
    }
    if targetBlocks >= MaxHeaderFetch {
        targetBlocks = MaxHeaderFetch - 15
    }
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()
    tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)

    // Make sure canceling works with a pristine downloader
    tester.downloader.cancel()
    if !tester.downloader.queue.Idle() {
        t.Errorf("download queue not idle")
    }
    // Synchronise with the peer, but cancel afterwards
    if err := tester.sync("peer", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    tester.downloader.cancel()
    if !tester.downloader.queue.Idle() {
        t.Errorf("download queue not idle")
    }
}

// Tests that synchronisation from multiple peers works as intended (multi thread sanity test).
func TestMultiSynchronisation61(t *testing.T)      { testMultiSynchronisation(t, 61, FullSync) }
func TestMultiSynchronisation62(t *testing.T)      { testMultiSynchronisation(t, 62, FullSync) }
func TestMultiSynchronisation63Full(t *testing.T)  { testMultiSynchronisation(t, 63, FullSync) }
func TestMultiSynchronisation63Fast(t *testing.T)  { testMultiSynchronisation(t, 63, FastSync) }
func TestMultiSynchronisation64Full(t *testing.T)  { testMultiSynchronisation(t, 64, FullSync) }
func TestMultiSynchronisation64Fast(t *testing.T)  { testMultiSynchronisation(t, 64, FastSync) }
func TestMultiSynchronisation64Light(t *testing.T) { testMultiSynchronisation(t, 64, LightSync) }

func testMultiSynchronisation(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create various peers with various parts of the chain
    targetPeers := 8
    targetBlocks := targetPeers*blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()
    for i := 0; i < targetPeers; i++ {
        id := fmt.Sprintf("peer #%d", i)
        tester.newPeer(id, protocol, hashes[i*blockCacheLimit:], headers, blocks, receipts)
    }
    if err := tester.sync("peer #0", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)
}

// Tests that synchronisations behave well in multi-version protocol environments
// and not wreak havoc on other nodes in the network.
func TestMultiProtoSynchronisation61(t *testing.T)      { testMultiProtoSync(t, 61, FullSync) }
func TestMultiProtoSynchronisation62(t *testing.T)      { testMultiProtoSync(t, 62, FullSync) }
func TestMultiProtoSynchronisation63Full(t *testing.T)  { testMultiProtoSync(t, 63, FullSync) }
func TestMultiProtoSynchronisation63Fast(t *testing.T)  { testMultiProtoSync(t, 63, FastSync) }
func TestMultiProtoSynchronisation64Full(t *testing.T)  { testMultiProtoSync(t, 64, FullSync) }
func TestMultiProtoSynchronisation64Fast(t *testing.T)  { testMultiProtoSync(t, 64, FastSync) }
func TestMultiProtoSynchronisation64Light(t *testing.T) { testMultiProtoSync(t, 64, LightSync) }

func testMultiProtoSync(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    // Create peers of every type
    tester := newTester()
    tester.newPeer("peer 61", 61, hashes, nil, blocks, nil)
    tester.newPeer("peer 62", 62, hashes, headers, blocks, nil)
    tester.newPeer("peer 63", 63, hashes, headers, blocks, receipts)
    tester.newPeer("peer 64", 64, hashes, headers, blocks, receipts)

    // Synchronise with the requested peer and make sure all blocks were retrieved
    if err := tester.sync(fmt.Sprintf("peer %d", protocol), nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)

    // Check that no peers have been dropped off
    for _, version := range []int{61, 62, 63, 64} {
        peer := fmt.Sprintf("peer %d", version)
        if _, ok := tester.peerHashes[peer]; !ok {
            t.Errorf("%s dropped", peer)
        }
    }
}

// Tests that if a block is empty (e.g. header only), no body request should be
// made, and instead the header should be assembled into a whole block in itself.
func TestEmptyShortCircuit62(t *testing.T)      { testEmptyShortCircuit(t, 62, FullSync) }
func TestEmptyShortCircuit63Full(t *testing.T)  { testEmptyShortCircuit(t, 63, FullSync) }
func TestEmptyShortCircuit63Fast(t *testing.T)  { testEmptyShortCircuit(t, 63, FastSync) }
func TestEmptyShortCircuit64Full(t *testing.T)  { testEmptyShortCircuit(t, 64, FullSync) }
func TestEmptyShortCircuit64Fast(t *testing.T)  { testEmptyShortCircuit(t, 64, FastSync) }
func TestEmptyShortCircuit64Light(t *testing.T) { testEmptyShortCircuit(t, 64, LightSync) }

func testEmptyShortCircuit(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a block chain to download
    targetBlocks := 2*blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()
    tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)

    // Instrument the downloader to signal body requests
    bodiesHave, receiptsHave := int32(0), int32(0)
    tester.downloader.bodyFetchHook = func(headers []*types.Header) {
        atomic.AddInt32(&bodiesHave, int32(len(headers)))
    }
    tester.downloader.receiptFetchHook = func(headers []*types.Header) {
        atomic.AddInt32(&receiptsHave, int32(len(headers)))
    }
    // Synchronise with the peer and make sure all blocks were retrieved
    if err := tester.sync("peer", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)

    // Validate the number of block bodies that should have been requested
    bodiesNeeded, receiptsNeeded := 0, 0
    for _, block := range blocks {
        if mode != LightSync && block != genesis && (len(block.Transactions()) > 0 || len(block.Uncles()) > 0) {
            bodiesNeeded++
        }
    }
    for hash, receipt := range receipts {
        if mode == FastSync && len(receipt) > 0 && headers[hash].Number.Uint64() <= tester.downloader.queue.fastSyncPivot {
            receiptsNeeded++
        }
    }
    if int(bodiesHave) != bodiesNeeded {
        t.Errorf("body retrieval count mismatch: have %v, want %v", bodiesHave, bodiesNeeded)
    }
    if int(receiptsHave) != receiptsNeeded {
        t.Errorf("receipt retrieval count mismatch: have %v, want %v", receiptsHave, receiptsNeeded)
    }
}

// Tests that headers are enqueued continuously, preventing malicious nodes from
// stalling the downloader by feeding gapped header chains.
func TestMissingHeaderAttack62(t *testing.T)      { testMissingHeaderAttack(t, 62, FullSync) }
func TestMissingHeaderAttack63Full(t *testing.T)  { testMissingHeaderAttack(t, 63, FullSync) }
func TestMissingHeaderAttack63Fast(t *testing.T)  { testMissingHeaderAttack(t, 63, FastSync) }
func TestMissingHeaderAttack64Full(t *testing.T)  { testMissingHeaderAttack(t, 64, FullSync) }
func TestMissingHeaderAttack64Fast(t *testing.T)  { testMissingHeaderAttack(t, 64, FastSync) }
func TestMissingHeaderAttack64Light(t *testing.T) { testMissingHeaderAttack(t, 64, LightSync) }

func testMissingHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()

    // Attempt a full sync with an attacker feeding gapped headers
    tester.newPeer("attack", protocol, hashes, headers, blocks, receipts)
    missing := targetBlocks / 2
    delete(tester.peerHeaders["attack"], hashes[missing])

    if err := tester.sync("attack", nil, mode); err == nil {
        t.Fatalf("succeeded attacker synchronisation")
    }
    // Synchronise with the valid peer and make sure sync succeeds
    tester.newPeer("valid", protocol, hashes, headers, blocks, receipts)
    if err := tester.sync("valid", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)
}

// Tests that if requested headers are shifted (i.e. first is missing), the queue
// detects the invalid numbering.
func TestShiftedHeaderAttack62(t *testing.T)      { testShiftedHeaderAttack(t, 62, FullSync) }
func TestShiftedHeaderAttack63Full(t *testing.T)  { testShiftedHeaderAttack(t, 63, FullSync) }
func TestShiftedHeaderAttack63Fast(t *testing.T)  { testShiftedHeaderAttack(t, 63, FastSync) }
func TestShiftedHeaderAttack64Full(t *testing.T)  { testShiftedHeaderAttack(t, 64, FullSync) }
func TestShiftedHeaderAttack64Fast(t *testing.T)  { testShiftedHeaderAttack(t, 64, FastSync) }
func TestShiftedHeaderAttack64Light(t *testing.T) { testShiftedHeaderAttack(t, 64, LightSync) }

func testShiftedHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()

    // Attempt a full sync with an attacker feeding shifted headers
    tester.newPeer("attack", protocol, hashes, headers, blocks, receipts)
    delete(tester.peerHeaders["attack"], hashes[len(hashes)-2])
    delete(tester.peerBlocks["attack"], hashes[len(hashes)-2])
    delete(tester.peerReceipts["attack"], hashes[len(hashes)-2])

    if err := tester.sync("attack", nil, mode); err == nil {
        t.Fatalf("succeeded attacker synchronisation")
    }
    // Synchronise with the valid peer and make sure sync succeeds
    tester.newPeer("valid", protocol, hashes, headers, blocks, receipts)
    if err := tester.sync("valid", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    assertOwnChain(t, tester, targetBlocks+1)
}

// Tests that upon detecting an invalid header, the recent ones are rolled back
// for various failure scenarios. Afterwards a full sync is attempted to make
// sure no state was corrupted.
func TestInvalidHeaderRollback63Fast(t *testing.T)  { testInvalidHeaderRollback(t, 63, FastSync) }
func TestInvalidHeaderRollback64Fast(t *testing.T)  { testInvalidHeaderRollback(t, 64, FastSync) }
func TestInvalidHeaderRollback64Light(t *testing.T) { testInvalidHeaderRollback(t, 64, LightSync) }

func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
    // Create a small enough block chain to download
    targetBlocks := 3*fsHeaderSafetyNet + fsMinFullBlocks
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    tester := newTester()

    // Attempt to sync with an attacker that feeds junk during the fast sync phase.
    // This should result in the last fsHeaderSafetyNet headers being rolled back.
    tester.newPeer("fast-attack", protocol, hashes, headers, blocks, receipts)
    missing := fsHeaderSafetyNet + MaxHeaderFetch + 1
    delete(tester.peerHeaders["fast-attack"], hashes[len(hashes)-missing])

    if err := tester.sync("fast-attack", nil, mode); err == nil {
        t.Fatalf("succeeded fast attacker synchronisation")
    }
    if head := tester.headHeader().Number.Int64(); int(head) > MaxHeaderFetch {
        t.Errorf("rollback head mismatch: have %v, want at most %v", head, MaxHeaderFetch)
    }
    // Attempt to sync with an attacker that feeds junk during the block import phase.
    // This should result in both the last fsHeaderSafetyNet number of headers being
    // rolled back, and also the pivot point being reverted to a non-block status.
    tester.newPeer("block-attack", protocol, hashes, headers, blocks, receipts)
    missing = 3*fsHeaderSafetyNet + MaxHeaderFetch + 1
    delete(tester.peerHeaders["block-attack"], hashes[len(hashes)-missing])

    if err := tester.sync("block-attack", nil, mode); err == nil {
        t.Fatalf("succeeded block attacker synchronisation")
    }
    if head := tester.headHeader().Number.Int64(); int(head) > 2*fsHeaderSafetyNet+MaxHeaderFetch {
        t.Errorf("rollback head mismatch: have %v, want at most %v", head, 2*fsHeaderSafetyNet+MaxHeaderFetch)
    }
    if mode == FastSync {
        if head := tester.headBlock().NumberU64(); head != 0 {
            t.Errorf("fast sync pivot block #%d not rolled back", head)
        }
    }
    // Attempt to sync with an attacker that withholds promised blocks after the
    // fast sync pivot point. This could be a trial to leave the node with a bad
    // but already imported pivot block.
    tester.newPeer("withhold-attack", protocol, hashes, headers, blocks, receipts)
    missing = 3*fsHeaderSafetyNet + MaxHeaderFetch + 1

    tester.downloader.noFast = false
    tester.downloader.syncInitHook = func(uint64, uint64) {
        for i := missing; i <= len(hashes); i++ {
            delete(tester.peerHeaders["withhold-attack"], hashes[len(hashes)-i])
        }
        tester.downloader.syncInitHook = nil
    }

    if err := tester.sync("withhold-attack", nil, mode); err == nil {
        t.Fatalf("succeeded withholding attacker synchronisation")
    }
    if head := tester.headHeader().Number.Int64(); int(head) > 2*fsHeaderSafetyNet+MaxHeaderFetch {
        t.Errorf("rollback head mismatch: have %v, want at most %v", head, 2*fsHeaderSafetyNet+MaxHeaderFetch)
    }
    if mode == FastSync {
        if head := tester.headBlock().NumberU64(); head != 0 {
            t.Errorf("fast sync pivot block #%d not rolled back", head)
        }
    }
    // Synchronise with the valid peer and make sure sync succeeds. Since the last
    // rollback should also disable fast syncing for this process, verify that we
    // did a fresh full sync. Note, we can't assert anything about the receipts
    // since we won't purge the database of them, hence we can't use assertOwnChain.
    tester.newPeer("valid", protocol, hashes, headers, blocks, receipts)
    if err := tester.sync("valid", nil, mode); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if hs := len(tester.ownHeaders); hs != len(headers) {
        t.Fatalf("synchronised headers mismatch: have %v, want %v", hs, len(headers))
    }
    if mode != LightSync {
        if bs := len(tester.ownBlocks); bs != len(blocks) {
            t.Fatalf("synchronised blocks mismatch: have %v, want %v", bs, len(blocks))
        }
    }
}

// Tests that a peer advertising an high TD doesn't get to stall the downloader
// afterwards by not sending any useful hashes.
func TestHighTDStarvationAttack61(t *testing.T)      { testHighTDStarvationAttack(t, 61, FullSync) }
func TestHighTDStarvationAttack62(t *testing.T)      { testHighTDStarvationAttack(t, 62, FullSync) }
func TestHighTDStarvationAttack63Full(t *testing.T)  { testHighTDStarvationAttack(t, 63, FullSync) }
func TestHighTDStarvationAttack63Fast(t *testing.T)  { testHighTDStarvationAttack(t, 63, FastSync) }
func TestHighTDStarvationAttack64Full(t *testing.T)  { testHighTDStarvationAttack(t, 64, FullSync) }
func TestHighTDStarvationAttack64Fast(t *testing.T)  { testHighTDStarvationAttack(t, 64, FastSync) }
func TestHighTDStarvationAttack64Light(t *testing.T) { testHighTDStarvationAttack(t, 64, LightSync) }

func testHighTDStarvationAttack(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    tester := newTester()
    hashes, headers, blocks, receipts := makeChain(0, 0, genesis, nil)

    tester.newPeer("attack", protocol, []common.Hash{hashes[0]}, headers, blocks, receipts)
    if err := tester.sync("attack", big.NewInt(1000000), mode); err != errStallingPeer {
        t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
    }
}

// Tests that misbehaving peers are disconnected, whilst behaving ones are not.
func TestBlockHeaderAttackerDropping61(t *testing.T) { testBlockHeaderAttackerDropping(t, 61) }
func TestBlockHeaderAttackerDropping62(t *testing.T) { testBlockHeaderAttackerDropping(t, 62) }
func TestBlockHeaderAttackerDropping63(t *testing.T) { testBlockHeaderAttackerDropping(t, 63) }
func TestBlockHeaderAttackerDropping64(t *testing.T) { testBlockHeaderAttackerDropping(t, 64) }

func testBlockHeaderAttackerDropping(t *testing.T, protocol int) {
    // Define the disconnection requirement for individual hash fetch errors
    tests := []struct {
        result error
        drop   bool
    }{
        {nil, false},                   // Sync succeeded, all is well
        {errBusy, false},               // Sync is already in progress, no problem
        {errUnknownPeer, false},        // Peer is unknown, was already dropped, don't double drop
        {errBadPeer, true},             // Peer was deemed bad for some reason, drop it
        {errStallingPeer, true},        // Peer was detected to be stalling, drop it
        {errNoPeers, false},            // No peers to download from, soft race, no issue
        {errTimeout, true},             // No hashes received in due time, drop the peer
        {errEmptyHashSet, true},        // No hashes were returned as a response, drop as it's a dead end
        {errEmptyHeaderSet, true},      // No headers were returned as a response, drop as it's a dead end
        {errPeersUnavailable, true},    // Nobody had the advertised blocks, drop the advertiser
        {errInvalidChain, true},        // Hash chain was detected as invalid, definitely drop
        {errInvalidBlock, false},       // A bad peer was detected, but not the sync origin
        {errInvalidBody, false},        // A bad peer was detected, but not the sync origin
        {errInvalidReceipt, false},     // A bad peer was detected, but not the sync origin
        {errCancelHashFetch, false},    // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelBlockFetch, false},   // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelHeaderFetch, false},  // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelBodyFetch, false},    // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelReceiptFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelProcessing, false},   // Synchronisation was canceled, origin may be innocent, don't drop
    }
    // Run the tests and check disconnection status
    tester := newTester()
    for i, tt := range tests {
        // Register a new peer and ensure it's presence
        id := fmt.Sprintf("test %d", i)
        if err := tester.newPeer(id, protocol, []common.Hash{genesis.Hash()}, nil, nil, nil); err != nil {
            t.Fatalf("test %d: failed to register new peer: %v", i, err)
        }
        if _, ok := tester.peerHashes[id]; !ok {
            t.Fatalf("test %d: registered peer not found", i)
        }
        // 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(), big.NewInt(1000), FullSync)
        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)
        }
    }
}

// Tests that synchronisation progress (origin block number, current block number
// and highest block number) is tracked and updated correctly.
func TestSyncProgress61(t *testing.T)      { testSyncProgress(t, 61, FullSync) }
func TestSyncProgress62(t *testing.T)      { testSyncProgress(t, 62, FullSync) }
func TestSyncProgress63Full(t *testing.T)  { testSyncProgress(t, 63, FullSync) }
func TestSyncProgress63Fast(t *testing.T)  { testSyncProgress(t, 63, FastSync) }
func TestSyncProgress64Full(t *testing.T)  { testSyncProgress(t, 64, FullSync) }
func TestSyncProgress64Fast(t *testing.T)  { testSyncProgress(t, 64, FastSync) }
func TestSyncProgress64Light(t *testing.T) { testSyncProgress(t, 64, LightSync) }

func testSyncProgress(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    // Set a sync init hook to catch progress changes
    starting := make(chan struct{})
    progress := make(chan struct{})

    tester := newTester()
    tester.downloader.syncInitHook = func(origin, latest uint64) {
        starting <- struct{}{}
        <-progress
    }
    // Retrieve the sync progress and ensure they are zero (pristine sync)
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != 0 {
        t.Fatalf("Pristine progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, 0)
    }
    // Synchronise half the blocks and check initial progress
    tester.newPeer("peer-half", protocol, hashes[targetBlocks/2:], headers, blocks, receipts)
    pending := new(sync.WaitGroup)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("peer-half", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != uint64(targetBlocks/2+1) {
        t.Fatalf("Initial progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, targetBlocks/2+1)
    }
    progress <- struct{}{}
    pending.Wait()

    // Synchronise all the blocks and check continuation progress
    tester.newPeer("peer-full", protocol, hashes, headers, blocks, receipts)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("peer-full", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != uint64(targetBlocks/2+1) || current != uint64(targetBlocks/2+1) || latest != uint64(targetBlocks) {
        t.Fatalf("Completing progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, targetBlocks/2+1, targetBlocks/2+1, targetBlocks)
    }
    progress <- struct{}{}
    pending.Wait()

    // Check final progress after successful sync
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != uint64(targetBlocks/2+1) || current != uint64(targetBlocks) || latest != uint64(targetBlocks) {
        t.Fatalf("Final progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, targetBlocks/2+1, targetBlocks, targetBlocks)
    }
}

// Tests that synchronisation progress (origin block number and highest block
// number) is tracked and updated correctly in case of a fork (or manual head
// revertal).
func TestForkedSyncProgress61(t *testing.T)      { testForkedSyncProgress(t, 61, FullSync) }
func TestForkedSyncProgress62(t *testing.T)      { testForkedSyncProgress(t, 62, FullSync) }
func TestForkedSyncProgress63Full(t *testing.T)  { testForkedSyncProgress(t, 63, FullSync) }
func TestForkedSyncProgress63Fast(t *testing.T)  { testForkedSyncProgress(t, 63, FastSync) }
func TestForkedSyncProgress64Full(t *testing.T)  { testForkedSyncProgress(t, 64, FullSync) }
func TestForkedSyncProgress64Fast(t *testing.T)  { testForkedSyncProgress(t, 64, FastSync) }
func TestForkedSyncProgress64Light(t *testing.T) { testForkedSyncProgress(t, 64, LightSync) }

func testForkedSyncProgress(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a forked chain to simulate origin revertal
    common, fork := MaxHashFetch, 2*MaxHashFetch
    hashesA, hashesB, headersA, headersB, blocksA, blocksB, receiptsA, receiptsB := makeChainFork(common+fork, fork, genesis, nil)

    // Set a sync init hook to catch progress changes
    starting := make(chan struct{})
    progress := make(chan struct{})

    tester := newTester()
    tester.downloader.syncInitHook = func(origin, latest uint64) {
        starting <- struct{}{}
        <-progress
    }
    // Retrieve the sync progress and ensure they are zero (pristine sync)
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != 0 {
        t.Fatalf("Pristine progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, 0)
    }
    // Synchronise with one of the forks and check progress
    tester.newPeer("fork A", protocol, hashesA, headersA, blocksA, receiptsA)
    pending := new(sync.WaitGroup)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("fork A", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != uint64(len(hashesA)-1) {
        t.Fatalf("Initial progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, len(hashesA)-1)
    }
    progress <- struct{}{}
    pending.Wait()

    // Simulate a successful sync above the fork
    tester.downloader.syncStatsChainOrigin = tester.downloader.syncStatsChainHeight

    // Synchronise with the second fork and check progress resets
    tester.newPeer("fork B", protocol, hashesB, headersB, blocksB, receiptsB)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("fork B", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != uint64(common) || current != uint64(len(hashesA)-1) || latest != uint64(len(hashesB)-1) {
        t.Fatalf("Forking progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, common, len(hashesA)-1, len(hashesB)-1)
    }
    progress <- struct{}{}
    pending.Wait()

    // Check final progress after successful sync
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != uint64(common) || current != uint64(len(hashesB)-1) || latest != uint64(len(hashesB)-1) {
        t.Fatalf("Final progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, common, len(hashesB)-1, len(hashesB)-1)
    }
}

// Tests that if synchronisation is aborted due to some failure, then the progress
// origin is not updated in the next sync cycle, as it should be considered the
// continuation of the previous sync and not a new instance.
func TestFailedSyncProgress61(t *testing.T)      { testFailedSyncProgress(t, 61, FullSync) }
func TestFailedSyncProgress62(t *testing.T)      { testFailedSyncProgress(t, 62, FullSync) }
func TestFailedSyncProgress63Full(t *testing.T)  { testFailedSyncProgress(t, 63, FullSync) }
func TestFailedSyncProgress63Fast(t *testing.T)  { testFailedSyncProgress(t, 63, FastSync) }
func TestFailedSyncProgress64Full(t *testing.T)  { testFailedSyncProgress(t, 64, FullSync) }
func TestFailedSyncProgress64Fast(t *testing.T)  { testFailedSyncProgress(t, 64, FastSync) }
func TestFailedSyncProgress64Light(t *testing.T) { testFailedSyncProgress(t, 64, LightSync) }

func testFailedSyncProgress(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small enough block chain to download
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)

    // Set a sync init hook to catch progress changes
    starting := make(chan struct{})
    progress := make(chan struct{})

    tester := newTester()
    tester.downloader.syncInitHook = func(origin, latest uint64) {
        starting <- struct{}{}
        <-progress
    }
    // Retrieve the sync progress and ensure they are zero (pristine sync)
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != 0 {
        t.Fatalf("Pristine progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, 0)
    }
    // Attempt a full sync with a faulty peer
    tester.newPeer("faulty", protocol, hashes, headers, blocks, receipts)
    missing := targetBlocks / 2
    delete(tester.peerHeaders["faulty"], hashes[missing])
    delete(tester.peerBlocks["faulty"], hashes[missing])
    delete(tester.peerReceipts["faulty"], hashes[missing])

    pending := new(sync.WaitGroup)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("faulty", nil, mode); err == nil {
            t.Fatalf("succeeded faulty synchronisation")
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != uint64(targetBlocks) {
        t.Fatalf("Initial progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, targetBlocks)
    }
    progress <- struct{}{}
    pending.Wait()

    // Synchronise with a good peer and check that the progress origin remind the same after a failure
    tester.newPeer("valid", protocol, hashes, headers, blocks, receipts)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("valid", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current > uint64(targetBlocks/2) || latest != uint64(targetBlocks) {
        t.Fatalf("Completing progress mismatch: have %v/%v/%v, want %v/0-%v/%v", origin, current, latest, 0, targetBlocks/2, targetBlocks)
    }
    progress <- struct{}{}
    pending.Wait()

    // Check final progress after successful sync
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin > uint64(targetBlocks/2) || current != uint64(targetBlocks) || latest != uint64(targetBlocks) {
        t.Fatalf("Final progress mismatch: have %v/%v/%v, want 0-%v/%v/%v", origin, current, latest, targetBlocks/2, targetBlocks, targetBlocks)
    }
}

// Tests that if an attacker fakes a chain height, after the attack is detected,
// the progress height is successfully reduced at the next sync invocation.
func TestFakedSyncProgress61(t *testing.T)      { testFakedSyncProgress(t, 61, FullSync) }
func TestFakedSyncProgress62(t *testing.T)      { testFakedSyncProgress(t, 62, FullSync) }
func TestFakedSyncProgress63Full(t *testing.T)  { testFakedSyncProgress(t, 63, FullSync) }
func TestFakedSyncProgress63Fast(t *testing.T)  { testFakedSyncProgress(t, 63, FastSync) }
func TestFakedSyncProgress64Full(t *testing.T)  { testFakedSyncProgress(t, 64, FullSync) }
func TestFakedSyncProgress64Fast(t *testing.T)  { testFakedSyncProgress(t, 64, FastSync) }
func TestFakedSyncProgress64Light(t *testing.T) { testFakedSyncProgress(t, 64, LightSync) }

func testFakedSyncProgress(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()

    // Create a small block chain
    targetBlocks := blockCacheLimit - 15
    hashes, headers, blocks, receipts := makeChain(targetBlocks+3, 0, genesis, nil)

    // Set a sync init hook to catch progress changes
    starting := make(chan struct{})
    progress := make(chan struct{})

    tester := newTester()
    tester.downloader.syncInitHook = func(origin, latest uint64) {
        starting <- struct{}{}
        <-progress
    }
    // Retrieve the sync progress and ensure they are zero (pristine sync)
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != 0 {
        t.Fatalf("Pristine progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, 0)
    }
    //  Create and sync with an attacker that promises a higher chain than available
    tester.newPeer("attack", protocol, hashes, headers, blocks, receipts)
    for i := 1; i < 3; i++ {
        delete(tester.peerHeaders["attack"], hashes[i])
        delete(tester.peerBlocks["attack"], hashes[i])
        delete(tester.peerReceipts["attack"], hashes[i])
    }

    pending := new(sync.WaitGroup)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("attack", nil, mode); err == nil {
            t.Fatalf("succeeded attacker synchronisation")
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current != 0 || latest != uint64(targetBlocks+3) {
        t.Fatalf("Initial progress mismatch: have %v/%v/%v, want %v/%v/%v", origin, current, latest, 0, 0, targetBlocks+3)
    }
    progress <- struct{}{}
    pending.Wait()

    // Synchronise with a good peer and check that the progress height has been reduced to the true value
    tester.newPeer("valid", protocol, hashes[3:], headers, blocks, receipts)
    pending.Add(1)

    go func() {
        defer pending.Done()
        if err := tester.sync("valid", nil, mode); err != nil {
            t.Fatalf("failed to synchronise blocks: %v", err)
        }
    }()
    <-starting
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin != 0 || current > uint64(targetBlocks) || latest != uint64(targetBlocks) {
        t.Fatalf("Completing progress mismatch: have %v/%v/%v, want %v/0-%v/%v", origin, current, latest, 0, targetBlocks, targetBlocks)
    }
    progress <- struct{}{}
    pending.Wait()

    // Check final progress after successful sync
    if origin, current, latest, _, _ := tester.downloader.Progress(); origin > uint64(targetBlocks) || current != uint64(targetBlocks) || latest != uint64(targetBlocks) {
        t.Fatalf("Final progress mismatch: have %v/%v/%v, want 0-%v/%v/%v", origin, current, latest, targetBlocks, targetBlocks, targetBlocks)
    }
}

// This test reproduces an issue where unexpected deliveries would
// block indefinitely if they arrived at the right time.
func TestDeliverHeadersHang62(t *testing.T)      { testDeliverHeadersHang(t, 62, FullSync) }
func TestDeliverHeadersHang63Full(t *testing.T)  { testDeliverHeadersHang(t, 63, FullSync) }
func TestDeliverHeadersHang63Fast(t *testing.T)  { testDeliverHeadersHang(t, 63, FastSync) }
func TestDeliverHeadersHang64Full(t *testing.T)  { testDeliverHeadersHang(t, 64, FullSync) }
func TestDeliverHeadersHang64Fast(t *testing.T)  { testDeliverHeadersHang(t, 64, FastSync) }
func TestDeliverHeadersHang64Light(t *testing.T) { testDeliverHeadersHang(t, 64, LightSync) }

func testDeliverHeadersHang(t *testing.T, protocol int, mode SyncMode) {
    t.Parallel()
    hashes, headers, blocks, receipts := makeChain(5, 0, genesis, nil)
    fakeHeads := []*types.Header{{}, {}, {}, {}}
    for i := 0; i < 200; i++ {
        tester := newTester()
        tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
        // Whenever the downloader requests headers, flood it with
        // a lot of unrequested header deliveries.
        tester.downloader.peers.peers["peer"].getAbsHeaders = func(from uint64, count, skip int, reverse bool) error {
            deliveriesDone := make(chan struct{}, 500)
            for i := 0; i < cap(deliveriesDone); i++ {
                peer := fmt.Sprintf("fake-peer%d", i)
                go func() {
                    tester.downloader.DeliverHeaders(peer, fakeHeads)
                    deliveriesDone <- struct{}{}
                }()
            }
            // Deliver the actual requested headers.
            impl := tester.peerGetAbsHeadersFn("peer", 0)
            go impl(from, count, skip, reverse)
            // None of the extra deliveries should block.
            timeout := time.After(5 * time.Second)
            for i := 0; i < cap(deliveriesDone); i++ {
                select {
                case <-deliveriesDone:
                case <-timeout:
                    panic("blocked")
                }
            }
            return nil
        }
        if err := tester.sync("peer", nil, mode); err != nil {
            t.Errorf("sync failed: %v", err)
        }
    }
}