path: root/eth/fetcher/fetcher_test.go

package fetcher

import (
    "errors"
    "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/types"
    "github.com/ethereum/go-ethereum/ethdb"
)

var (
    testdb, _    = ethdb.NewMemDatabase()
    genesis      = core.GenesisBlockForTesting(testdb, common.Address{}, big.NewInt(0))
    unknownBlock = types.NewBlock(&types.Header{}, nil, nil, nil)
)

// makeChain creates a chain of n blocks starting at and 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
}

// fetcherTester is a test simulator for mocking out local block chain.
type fetcherTester struct {
    fetcher *Fetcher

    hashes []common.Hash                // Hash chain belonging to the tester
    blocks map[common.Hash]*types.Block // Blocks belonging to the tester

    lock sync.RWMutex
}

// newTester creates a new fetcher test mocker.
func newTester() *fetcherTester {
    tester := &fetcherTester{
        hashes: []common.Hash{genesis.Hash()},
        blocks: map[common.Hash]*types.Block{genesis.Hash(): genesis},
    }
    tester.fetcher = New(tester.getBlock, tester.verifyBlock, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
    tester.fetcher.Start()

    return tester
}

// getBlock retrieves a block from the tester's block chain.
func (f *fetcherTester) getBlock(hash common.Hash) *types.Block {
    f.lock.RLock()
    defer f.lock.RUnlock()

    return f.blocks[hash]
}

// verifyBlock is a nop placeholder for the block header verification.
func (f *fetcherTester) verifyBlock(block *types.Block, parent *types.Block) error {
    return nil
}

// broadcastBlock is a nop placeholder for the block broadcasting.
func (f *fetcherTester) broadcastBlock(block *types.Block, propagate bool) {
}

// chainHeight retrieves the current height (block number) of the chain.
func (f *fetcherTester) chainHeight() uint64 {
    f.lock.RLock()
    defer f.lock.RUnlock()

    return f.blocks[f.hashes[len(f.hashes)-1]].NumberU64()
}

// insertChain injects a new blocks into the simulated chain.
func (f *fetcherTester) insertChain(blocks types.Blocks) (int, error) {
    f.lock.Lock()
    defer f.lock.Unlock()

    for i, block := range blocks {
        // Make sure the parent in known
        if _, ok := f.blocks[block.ParentHash()]; !ok {
            return i, errors.New("unknown parent")
        }
        // Discard any new blocks if the same height already exists
        if block.NumberU64() <= f.blocks[f.hashes[len(f.hashes)-1]].NumberU64() {
            return i, nil
        }
        // Otherwise build our current chain
        f.hashes = append(f.hashes, block.Hash())
        f.blocks[block.Hash()] = block
    }
    return 0, nil
}

// dropPeer is a nop placeholder for the peer removal.
func (f *fetcherTester) dropPeer(peer string) {
}

// peerFetcher retrieves a fetcher associated with a simulated peer.
func (f *fetcherTester) makeFetcher(blocks map[common.Hash]*types.Block) blockRequesterFn {
    closure := make(map[common.Hash]*types.Block)
    for hash, block := range blocks {
        closure[hash] = block
    }
    // Create a function that returns blocks from the closure
    return func(hashes []common.Hash) error {
        // Gather the blocks to return
        blocks := make([]*types.Block, 0, len(hashes))
        for _, hash := range hashes {
            if block, ok := closure[hash]; ok {
                blocks = append(blocks, block)
            }
        }
        // Return on a new thread
        go f.fetcher.Filter(blocks)

        return nil
    }
}

// verifyImportEvent verifies that one single event arrive on an import channel.
func verifyImportEvent(t *testing.T, imported chan *types.Block) {
    select {
    case <-imported:
    case <-time.After(time.Second):
        t.Fatalf("import timeout")
    }
}

// verifyImportCount verifies that exactly count number of events arrive on an
// import hook channel.
func verifyImportCount(t *testing.T, imported chan *types.Block, count int) {
    for i := 0; i < count; i++ {
        select {
        case <-imported:
        case <-time.After(time.Second):
            t.Fatalf("block %d: import timeout", i)
        }
    }
    verifyImportDone(t, imported)
}

// verifyImportDone verifies that no more events are arriving on an import channel.
func verifyImportDone(t *testing.T, imported chan *types.Block) {
    select {
    case <-imported:
        t.Fatalf("extra block imported")
    case <-time.After(50 * time.Millisecond):
    }
}

// Tests that a fetcher accepts block announcements and initiates retrievals for
// them, successfully importing into the local chain.
func TestSequentialAnnouncements(t *testing.T) {
    // Create a chain of blocks to import
    targetBlocks := 4 * hashLimit
    hashes, blocks := makeChain(targetBlocks, 0, genesis)

    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    // Iteratively announce blocks until all are imported
    imported := make(chan *types.Block)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    for i := len(hashes) - 2; i >= 0; i-- {
        tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
        verifyImportEvent(t, imported)
    }
    verifyImportDone(t, imported)
}

// Tests that if blocks are announced by multiple peers (or even the same buggy
// peer), they will only get downloaded at most once.
func TestConcurrentAnnouncements(t *testing.T) {
    // Create a chain of blocks to import
    targetBlocks := 4 * hashLimit
    hashes, blocks := makeChain(targetBlocks, 0, genesis)

    // Assemble a tester with a built in counter for the requests
    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    counter := uint32(0)
    wrapper := func(hashes []common.Hash) error {
        atomic.AddUint32(&counter, uint32(len(hashes)))
        return fetcher(hashes)
    }
    // Iteratively announce blocks until all are imported
    imported := make(chan *types.Block)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    for i := len(hashes) - 2; i >= 0; i-- {
        tester.fetcher.Notify("first", hashes[i], time.Now().Add(-arriveTimeout), wrapper)
        tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout+time.Millisecond), wrapper)
        tester.fetcher.Notify("second", hashes[i], time.Now().Add(-arriveTimeout-time.Millisecond), wrapper)

        verifyImportEvent(t, imported)
    }
    verifyImportDone(t, imported)

    // Make sure no blocks were retrieved twice
    if int(counter) != targetBlocks {
        t.Fatalf("retrieval count mismatch: have %v, want %v", counter, targetBlocks)
    }
}

// Tests that announcements arriving while a previous is being fetched still
// results in a valid import.
func TestOverlappingAnnouncements(t *testing.T) {
    // Create a chain of blocks to import
    targetBlocks := 4 * hashLimit
    hashes, blocks := makeChain(targetBlocks, 0, genesis)

    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    // Iteratively announce blocks, but overlap them continuously
    fetching := make(chan []common.Hash)
    imported := make(chan *types.Block, len(hashes)-1)
    tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    for i := len(hashes) - 2; i >= 0; i-- {
        tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
        select {
        case <-fetching:
        case <-time.After(time.Second):
            t.Fatalf("hash %d: announce timeout", len(hashes)-i)
        }
    }
    // Wait for all the imports to complete and check count
    verifyImportCount(t, imported, len(hashes)-1)
}

// Tests that announces already being retrieved will not be duplicated.
func TestPendingDeduplication(t *testing.T) {
    // Create a hash and corresponding block
    hashes, blocks := makeChain(1, 0, genesis)

    // Assemble a tester with a built in counter and delayed fetcher
    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    delay := 50 * time.Millisecond
    counter := uint32(0)
    wrapper := func(hashes []common.Hash) error {
        atomic.AddUint32(&counter, uint32(len(hashes)))

        // Simulate a long running fetch
        go func() {
            time.Sleep(delay)
            fetcher(hashes)
        }()
        return nil
    }
    // Announce the same block many times until it's fetched (wait for any pending ops)
    for tester.getBlock(hashes[0]) == nil {
        tester.fetcher.Notify("repeater", hashes[0], time.Now().Add(-arriveTimeout), wrapper)
        time.Sleep(time.Millisecond)
    }
    time.Sleep(delay)

    // Check that all blocks were imported and none fetched twice
    if imported := len(tester.blocks); imported != 2 {
        t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 2)
    }
    if int(counter) != 1 {
        t.Fatalf("retrieval count mismatch: have %v, want %v", counter, 1)
    }
}

// Tests that announcements retrieved in a random order are cached and eventually
// imported when all the gaps are filled in.
func TestRandomArrivalImport(t *testing.T) {
    // Create a chain of blocks to import, and choose one to delay
    targetBlocks := maxQueueDist
    hashes, blocks := makeChain(targetBlocks, 0, genesis)
    skip := targetBlocks / 2

    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    // Iteratively announce blocks, skipping one entry
    imported := make(chan *types.Block, len(hashes)-1)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    for i := len(hashes) - 1; i >= 0; i-- {
        if i != skip {
            tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
            time.Sleep(time.Millisecond)
        }
    }
    // Finally announce the skipped entry and check full import
    tester.fetcher.Notify("valid", hashes[skip], time.Now().Add(-arriveTimeout), fetcher)
    verifyImportCount(t, imported, len(hashes)-1)
}

// Tests that direct block enqueues (due to block propagation vs. hash announce)
// are correctly schedule, filling and import queue gaps.
func TestQueueGapFill(t *testing.T) {
    // Create a chain of blocks to import, and choose one to not announce at all
    targetBlocks := maxQueueDist
    hashes, blocks := makeChain(targetBlocks, 0, genesis)
    skip := targetBlocks / 2

    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    // Iteratively announce blocks, skipping one entry
    imported := make(chan *types.Block, len(hashes)-1)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    for i := len(hashes) - 1; i >= 0; i-- {
        if i != skip {
            tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
            time.Sleep(time.Millisecond)
        }
    }
    // Fill the missing block directly as if propagated
    tester.fetcher.Enqueue("valid", blocks[hashes[skip]])
    verifyImportCount(t, imported, len(hashes)-1)
}

// Tests that blocks arriving from various sources (multiple propagations, hash
// announces, etc) do not get scheduled for import multiple times.
func TestImportDeduplication(t *testing.T) {
    // Create two blocks to import (one for duplication, the other for stalling)
    hashes, blocks := makeChain(2, 0, genesis)

    // Create the tester and wrap the importer with a counter
    tester := newTester()
    fetcher := tester.makeFetcher(blocks)

    counter := uint32(0)
    tester.fetcher.insertChain = func(blocks types.Blocks) (int, error) {
        atomic.AddUint32(&counter, uint32(len(blocks)))
        return tester.insertChain(blocks)
    }
    // Instrument the fetching and imported events
    fetching := make(chan []common.Hash)
    imported := make(chan *types.Block, len(hashes)-1)
    tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    // Announce the duplicating block, wait for retrieval, and also propagate directly
    tester.fetcher.Notify("valid", hashes[0], time.Now().Add(-arriveTimeout), fetcher)
    <-fetching

    tester.fetcher.Enqueue("valid", blocks[hashes[0]])
    tester.fetcher.Enqueue("valid", blocks[hashes[0]])
    tester.fetcher.Enqueue("valid", blocks[hashes[0]])

    // Fill the missing block directly as if propagated, and check import uniqueness
    tester.fetcher.Enqueue("valid", blocks[hashes[1]])
    verifyImportCount(t, imported, 2)

    if counter != 2 {
        t.Fatalf("import invocation count mismatch: have %v, want %v", counter, 2)
    }
}

// Tests that blocks with numbers much lower or higher than out current head get
// discarded no prevent wasting resources on useless blocks from faulty peers.
func TestDistantDiscarding(t *testing.T) {
    // Create a long chain to import
    hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
    head := hashes[len(hashes)/2]

    // Create a tester and simulate a head block being the middle of the above chain
    tester := newTester()
    tester.hashes = []common.Hash{head}
    tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}

    // Ensure that a block with a lower number than the threshold is discarded
    tester.fetcher.Enqueue("lower", blocks[hashes[0]])
    time.Sleep(10 * time.Millisecond)
    if !tester.fetcher.queue.Empty() {
        t.Fatalf("fetcher queued stale block")
    }
    // Ensure that a block with a higher number than the threshold is discarded
    tester.fetcher.Enqueue("higher", blocks[hashes[len(hashes)-1]])
    time.Sleep(10 * time.Millisecond)
    if !tester.fetcher.queue.Empty() {
        t.Fatalf("fetcher queued future block")
    }
}

// Tests that a peer is unable to use unbounded memory with sending infinite
// block announcements to a node, but that even in the face of such an attack,
// the fetcher remains operational.
func TestHashMemoryExhaustionAttack(t *testing.T) {
    // Create a tester with instrumented import hooks
    tester := newTester()

    imported := make(chan *types.Block)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    // Create a valid chain and an infinite junk chain
    targetBlocks := hashLimit + 2*maxQueueDist
    hashes, blocks := makeChain(targetBlocks, 0, genesis)
    valid := tester.makeFetcher(blocks)

    attack, _ := makeChain(targetBlocks, 0, unknownBlock)
    attacker := tester.makeFetcher(nil)

    // Feed the tester a huge hashset from the attacker, and a limited from the valid peer
    for i := 0; i < len(attack); i++ {
        if i < maxQueueDist {
            tester.fetcher.Notify("valid", hashes[len(hashes)-2-i], time.Now(), valid)
        }
        tester.fetcher.Notify("attacker", attack[i], time.Now(), attacker)
    }
    if len(tester.fetcher.announced) != hashLimit+maxQueueDist {
        t.Fatalf("queued announce count mismatch: have %d, want %d", len(tester.fetcher.announced), hashLimit+maxQueueDist)
    }
    // Wait for fetches to complete
    verifyImportCount(t, imported, maxQueueDist)

    // Feed the remaining valid hashes to ensure DOS protection state remains clean
    for i := len(hashes) - maxQueueDist - 2; i >= 0; i-- {
        tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), valid)
        verifyImportEvent(t, imported)
    }
    verifyImportDone(t, imported)
}

// Tests that blocks sent to the fetcher (either through propagation or via hash
// announces and retrievals) don't pile up indefinitely, exhausting available
// system memory.
func TestBlockMemoryExhaustionAttack(t *testing.T) {
    // Create a tester with instrumented import hooks
    tester := newTester()

    imported := make(chan *types.Block)
    tester.fetcher.importedHook = func(block *types.Block) { imported <- block }

    // Create a valid chain and a batch of dangling (but in range) blocks
    targetBlocks := hashLimit + 2*maxQueueDist
    hashes, blocks := makeChain(targetBlocks, 0, genesis)
    attack := make(map[common.Hash]*types.Block)
    for i := byte(0); len(attack) < blockLimit+2*maxQueueDist; i++ {
        hashes, blocks := makeChain(maxQueueDist-1, i, unknownBlock)
        for _, hash := range hashes[:maxQueueDist-2] {
            attack[hash] = blocks[hash]
        }
    }
    // Try to feed all the attacker blocks make sure only a limited batch is accepted
    for _, block := range attack {
        tester.fetcher.Enqueue("attacker", block)
    }
    time.Sleep(200 * time.Millisecond)
    if queued := tester.fetcher.queue.Size(); queued != blockLimit {
        t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit)
    }
    // Queue up a batch of valid blocks, and check that a new peer is allowed to do so
    for i := 0; i < maxQueueDist-1; i++ {
        tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-3-i]])
    }
    time.Sleep(100 * time.Millisecond)
    if queued := tester.fetcher.queue.Size(); queued != blockLimit+maxQueueDist-1 {
        t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit+maxQueueDist-1)
    }
    // Insert the missing piece (and sanity check the import)
    tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2]])
    verifyImportCount(t, imported, maxQueueDist)

    // Insert the remaining blocks in chunks to ensure clean DOS protection
    for i := maxQueueDist; i < len(hashes)-1; i++ {
        tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2-i]])
        verifyImportEvent(t, imported)
    }
    verifyImportDone(t, imported)
}