Function TestDistantAnnouncementDiscarding

protocols/cpc/fetcher/fetcher_test.go:526–561

Tests that announcements with numbers much lower or higher than out current head get discarded to prevent wasting resources on useless blocks from faulty peers.

(t *testing.T)

// head get discarded to prevent wasting resources on useless blocks from faulty
// peers.
func TestDistantAnnouncementDiscarding(t *testing.T) {
	// Create a long chain to import and define the discard boundaries
	hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
	head := hashes[len(hashes)/2]

	low, high := len(hashes)/2+maxUncleDist+1, len(hashes)/2-maxQueueDist-1

	// Create a tester and simulate a head block being the middle of the above chain
	tester := newTester()

	tester.lock.Lock()
	tester.hashes = []common.Hash{head}
	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
	tester.lock.Unlock()

	headerFetcher := tester.makeHeaderFetcher("lower", blocks, -gatherSlack)
	bodyFetcher := tester.makeBodyFetcher("lower", blocks, 0)

	fetching := make(chan struct{}, 2)
	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- struct{}{} }

	// Ensure that a block with a lower number than the threshold is discarded
	tester.fetcher.Notify("lower", hashes[low], blocks[hashes[low]].NumberU64(), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
	select {
	case <-time.After(50 * time.Millisecond):
	case <-fetching:
		t.Fatalf("fetcher requested stale header")
	}
	// Ensure that a block with a higher number than the threshold is discarded
	tester.fetcher.Notify("higher", hashes[high], blocks[hashes[high]].NumberU64(), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
	select {
	case <-time.After(50 * time.Millisecond):
	case <-fetching:
		t.Fatalf("fetcher requested future header")
	}
}

// Tests that peers announcing blocks with invalid numbers (i.e. not matching
// the headers provided afterwards) get dropped as malicious.