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/atomic"
    "testing"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/event"
)

var (
    testdb, _ = ethdb.NewMemDatabase()
    genesis   = core.GenesisBlockForTesting(testdb, common.Address{}, big.NewInt(0))
)

// makeChain creates a chain of n blocks starting at but not including
// parent. the returned hash chain is ordered head->parent.
func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common.Hash]*types.Block) {
    blocks := core.GenerateChain(parent, testdb, n, func(i int, gen *core.BlockGen) {
        gen.SetCoinbase(common.Address{seed})
    })
    hashes := make([]common.Hash, n+1)
    hashes[len(hashes)-1] = parent.Hash()
    blockm := make(map[common.Hash]*types.Block, n+1)
    blockm[parent.Hash()] = parent
    for i, b := range blocks {
        hashes[len(hashes)-i-2] = b.Hash()
        blockm[b.Hash()] = b
    }
    return hashes, blockm
}

// 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) (h1, h2 []common.Hash, b1, b2 map[common.Hash]*types.Block) {
    // Create the common suffix.
    h, b := makeChain(n-f, 0, parent)
    // Create the forks.
    h1, b1 = makeChain(f, 1, b[h[0]])
    h1 = append(h1, h[1:]...)
    h2, b2 = makeChain(f, 2, b[h[0]])
    h2 = append(h2, h[1:]...)
    for hash, block := range b {
        b1[hash] = block
        b2[hash] = block
    }
    return h1, h2, b1, b2
}

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

    ownHashes  []common.Hash                           // Hash chain belonging to the tester
    ownBlocks  map[common.Hash]*types.Block            // Blocks belonging to the tester
    peerHashes map[string][]common.Hash                // Hash chain belonging to different test peers
    peerBlocks map[string]map[common.Hash]*types.Block // Blocks belonging to different test peers

    maxHashFetch int // Overrides the maximum number of retrieved hashes
}

// newTester creates a new downloader test mocker.
func newTester() *downloadTester {
    tester := &downloadTester{
        ownHashes:  []common.Hash{genesis.Hash()},
        ownBlocks:  map[common.Hash]*types.Block{genesis.Hash(): genesis},
        peerHashes: make(map[string][]common.Hash),
        peerBlocks: make(map[string]map[common.Hash]*types.Block),
    }
    tester.downloader = New(new(event.TypeMux), tester.hasBlock, tester.getBlock, tester.headBlock, tester.insertChain, tester.dropPeer)

    return tester
}

// sync starts synchronizing with a remote peer, blocking until it completes.
func (dl *downloadTester) sync(id string, td *big.Int) error {
    hash := dl.peerHashes[id][0]

    // If no particular TD was requested, load from the peer's blockchain
    if td == nil {
        td = big.NewInt(1)
        if block, ok := dl.peerBlocks[id][hash]; ok {
            td = block.Td
        }
    }
    err := dl.downloader.synchronise(id, hash, td)

    for {
        // If the queue is empty and processing stopped, break
        hashes, blocks := dl.downloader.queue.Size()
        if hashes+blocks == 0 && atomic.LoadInt32(&dl.downloader.processing) == 0 {
            break
        }
        // Otherwise sleep a bit and retry
        time.Sleep(time.Millisecond)
    }
    return err
}

// hasBlock checks if a block is pres   ent in the testers canonical chain.
func (dl *downloadTester) hasBlock(hash common.Hash) bool {
    return dl.getBlock(hash) != nil
}

// getBlock retrieves a block from the testers canonical chain.
func (dl *downloadTester) getBlock(hash common.Hash) *types.Block {
    return dl.ownBlocks[hash]
}

// headBlock retrieves the current head block from the canonical chain.
func (dl *downloadTester) headBlock() *types.Block {
    return dl.getBlock(dl.ownHashes[len(dl.ownHashes)-1])
}

// insertChain injects a new batch of blocks into the simulated chain.
func (dl *downloadTester) insertChain(blocks types.Blocks) (int, error) {
    for i, block := range blocks {
        if _, ok := dl.ownBlocks[block.ParentHash()]; !ok {
            return i, errors.New("unknown parent")
        }
        dl.ownHashes = append(dl.ownHashes, block.Hash())
        dl.ownBlocks[block.Hash()] = block
    }
    return len(blocks), nil
}

// newPeer registers a new block download source into the downloader.
func (dl *downloadTester) newPeer(id string, version int, hashes []common.Hash, blocks map[common.Hash]*types.Block) error {
    return dl.newSlowPeer(id, version, hashes, blocks, 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, blocks map[common.Hash]*types.Block, delay time.Duration) error {
    err := dl.downloader.RegisterPeer(id, version, hashes[0], dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, version, delay), dl.peerGetBlocksFn(id, delay))
    if err == nil {
        // Assign the owned hashes and blocks to the peer (deep copy)
        dl.peerHashes[id] = make([]common.Hash, len(hashes))
        copy(dl.peerHashes[id], hashes)
        dl.peerBlocks[id] = make(map[common.Hash]*types.Block)
        for hash, block := range blocks {
            dl.peerBlocks[id][hash] = block
        }
    }
    return err
}

// dropPeer simulates a hard peer removal from the connection pool.
func (dl *downloadTester) dropPeer(id string) {
    delete(dl.peerHashes, id)
    delete(dl.peerBlocks, 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)

        limit := MaxHashFetch
        if dl.maxHashFetch > 0 {
            limit = dl.maxHashFetch
        }
        // Gather the next batch of hashes
        hashes := dl.peerHashes[id]
        result := make([]common.Hash, 0, limit)
        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, version int, delay time.Duration) func(uint64, int) error {
    return func(head uint64, count int) error {
        time.Sleep(delay)

        limit := count
        if dl.maxHashFetch > 0 {
            limit = dl.maxHashFetch
        }
        // Gather the next batch of hashes
        hashes := dl.peerHashes[id]
        result := make([]common.Hash, 0, limit)
        for i := 0; i < limit && 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)
        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
    }
}

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

    tester := newTester()
    tester.newPeer("peer", eth61, hashes, blocks)

    // Synchronise with the peer and make sure all blocks were retrieved
    if err := tester.sync("peer", nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 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, eth61) }

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

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

    // Wrap the importer to allow stepping
    done := make(chan int)
    tester.downloader.insertChain = func(blocks types.Blocks) (int, error) {
        n, err := tester.insertChain(blocks)
        done <- n
        return n, err
    }
    // Start a synchronisation concurrently
    errc := make(chan error)
    go func() {
        errc <- tester.sync("peer", nil)
    }()
    // Iteratively take some blocks, always checking the retrieval count
    for len(tester.ownBlocks) < targetBlocks+1 {
        // Wait a bit for sync to throttle itself
        var cached int
        for start := time.Now(); time.Since(start) < 3*time.Second; {
            time.Sleep(25 * time.Millisecond)

            cached = len(tester.downloader.queue.blockPool)
            if cached == blockCacheLimit || len(tester.ownBlocks)+cached == 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
        if cached != blockCacheLimit && len(tester.ownBlocks)+cached < targetBlocks+1 {
            t.Fatalf("block count mismatch: have %v, want %v", cached, blockCacheLimit)
        }
        <-done // finish previous blocking import
        for cached > maxBlockProcess {
            cached -= <-done
        }
        time.Sleep(25 * time.Millisecond) // yield to the insertion
    }
    <-done // finish the last blocking import

    // Check that we haven't pulled more blocks than available
    if len(tester.ownBlocks) > targetBlocks+1 {
        t.Fatalf("target block count mismatch: have %v, want %v", len(tester.ownBlocks), 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) {
    // Create a long enough forked chain
    common, fork := MaxHashFetch, 2*MaxHashFetch
    hashesA, hashesB, blocksA, blocksB := makeChainFork(common+fork, fork, genesis)

    tester := newTester()
    tester.newPeer("fork A", eth61, hashesA, blocksA)
    tester.newPeer("fork B", eth61, hashesB, blocksB)

    // Synchronise with the peer and make sure all blocks were retrieved
    if err := tester.sync("fork A", nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if imported := len(tester.ownBlocks); imported != common+fork+1 {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, common+fork+1)
    }
    // Synchronise with the second peer and make sure that fork is pulled too
    if err := tester.sync("fork B", nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if imported := len(tester.ownBlocks); imported != common+2*fork+1 {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, common+2*fork+1)
    }
}

// Tests that an inactive downloader will not accept incoming hashes and blocks.
func TestInactiveDownloader(t *testing.T) {
    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 a canceled download wipes all previously accumulated state.
func TestCancel61(t *testing.T) { testCancel(t, eth61) }

func testCancel(t *testing.T, protocol int) {
    // Create a small enough block chain to download and the tester
    targetBlocks := blockCacheLimit - 15
    if targetBlocks >= MaxHashFetch {
        targetBlocks = MaxHashFetch - 15
    }
    hashes, blocks := makeChain(targetBlocks, 0, genesis)

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

    // Make sure canceling works with a pristine downloader
    tester.downloader.cancel()
    hashCount, blockCount := tester.downloader.queue.Size()
    if hashCount > 0 || blockCount > 0 {
        t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
    }
    // Synchronise with the peer, but cancel afterwards
    if err := tester.sync("peer", nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    tester.downloader.cancel()
    hashCount, blockCount = tester.downloader.queue.Size()
    if hashCount > 0 || blockCount > 0 {
        t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
    }
}

// Tests that synchronisation from multiple peers works as intended (multi thread sanity test).
func TestMultiSynchronisation61(t *testing.T) { testMultiSynchronisation(t, eth61) }

func testMultiSynchronisation(t *testing.T, protocol int) {
    // Create various peers with various parts of the chain
    targetPeers := 16
    targetBlocks := targetPeers*blockCacheLimit - 15
    hashes, blocks := makeChain(targetBlocks, 0, genesis)

    tester := newTester()
    for i := 0; i < targetPeers; i++ {
        id := fmt.Sprintf("peer #%d", i)
        tester.newPeer(id, protocol, hashes[i*blockCacheLimit:], blocks)
    }
    // Synchronise with the middle peer and make sure half of the blocks were retrieved
    id := fmt.Sprintf("peer #%d", targetPeers/2)
    if err := tester.sync(id, nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if imported := len(tester.ownBlocks); imported != len(tester.peerHashes[id]) {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(tester.peerHashes[id]))
    }
    // Synchronise with the best peer and make sure everything is retrieved
    if err := tester.sync("peer #0", nil); err != nil {
        t.Fatalf("failed to synchronise blocks: %v", err)
    }
    if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
    }
}

// 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) {
    tester := newTester()
    tester.newPeer("attack", eth61, []common.Hash{genesis.Hash()}, nil)
    if err := tester.sync("attack", big.NewInt(1000000)); 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 TestHashAttackerDropping(t *testing.T) {
    // 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
        {errBannedHead, true},        // Peer's head hash is a known bad hash, drop it
        {errNoPeers, false},          // No peers to download from, soft race, no issue
        {errPendingQueue, false},     // There are blocks still cached, wait to exhaust, 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
        {errPeersUnavailable, true},  // Nobody had the advertised blocks, drop the advertiser
        {errInvalidChain, true},      // Hash chain was detected as invalid, definitely drop
        {errCrossCheckFailed, true},  // Hash-origin failed to pass a block cross check, drop
        {errCancelHashFetch, false},  // Synchronisation was canceled, origin may be innocent, don't drop
        {errCancelBlockFetch, 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, eth61, []common.Hash{genesis.Hash()}, 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))
        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 feeding bad blocks will result in a peer drop.
func TestBlockAttackerDropping(t *testing.T) {
    // Define the disconnection requirement for individual block import errors
    tests := []struct {
        failure bool
        drop    bool
    }{
        {true, true},
        {false, false},
    }

    // 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, eth61, []common.Hash{common.Hash{}}, 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)
        }
        // Assemble a good or bad block, depending of the test
        raw := core.GenerateChain(genesis, testdb, 1, nil)[0]
        if tt.failure {
            parent := types.NewBlock(&types.Header{}, nil, nil, nil)
            raw = core.GenerateChain(parent, testdb, 1, nil)[0]
        }
        block := &Block{OriginPeer: id, RawBlock: raw}

        // Simulate block processing and check the result
        tester.downloader.queue.blockCache[0] = block
        tester.downloader.process()
        if _, ok := tester.peerHashes[id]; !ok != tt.drop {
            t.Errorf("test %d: peer drop mismatch for %v: have %v, want %v", i, tt.failure, !ok, tt.drop)
        }
    }
}