From efc1d5127f0e037baea0189f8be3f86013788831 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Fri, 16 Oct 2015 13:05:08 +0300
Subject: [PATCH] eth/downloader: assume stale delivery vs. attack

---
 eth/downloader/downloader.go      |  5 -----
 eth/downloader/downloader_test.go |  3 ++-
 eth/downloader/queue.go           | 25 +++++++++++++------------
 3 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index a435e8f171..3e53aec35e 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -1372,11 +1372,6 @@ func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliv
 					// The hash chain is invalid (blocks are not ordered properly), abort
 					return err
 
-				case errInvalidBody, errInvalidReceipt:
-					// The peer delivered something very bad, drop immediately
-					glog.V(logger.Error).Infof("%s: delivered invalid %s, dropping", peer, strings.ToLower(kind))
-					d.dropPeer(peer.id)
-
 				case errNoFetchesPending:
 					// Peer probably timed out with its delivery but came through
 					// in the end, demote, but allow to to pull from this peer.
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index a1754933cb..f0af4cbaee 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -1127,6 +1127,7 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
 	assertOwnChain(t, tester, targetBlocks+1)
 }
 
+/*
 // Tests that if a peer sends an invalid block piece (body or receipt) for a
 // requested block, it gets dropped immediately by the downloader.
 func TestInvalidContentAttack62(t *testing.T)      { testInvalidContentAttack(t, 62, FullSync) }
@@ -1171,7 +1172,7 @@ func testInvalidContentAttack(t *testing.T, protocol int, mode SyncMode) {
 	if _, ok := tester.peerHashes["receipt attack"]; ok {
 		t.Fatalf("receipt attacker not detected/dropped")
 	}
-}
+}*/
 
 // Tests that a peer advertising an high TD doesn't get to stall the downloader
 // afterwards by not sending any useful hashes.
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 3eee4f7b67..e09f90107b 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -859,7 +859,10 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 		}
 	}
 	// Assemble each of the results with their headers and retrieved data parts
-	errs := make([]error, 0)
+	var (
+		failure error
+		useful  bool
+	)
 	for i, header := range request.Headers {
 		// Short circuit assembly if no more fetch results are found
 		if i >= results {
@@ -868,15 +871,16 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 		// Reconstruct the next result if contents match up
 		index := int(header.Number.Int64() - int64(q.resultOffset))
 		if index >= len(q.resultCache) || index < 0 || q.resultCache[index] == nil {
-			errs = []error{errInvalidChain}
+			failure = errInvalidChain
 			break
 		}
 		if err := reconstruct(header, i, q.resultCache[index]); err != nil {
-			errs = []error{err}
+			failure = err
 			break
 		}
 		donePool[header.Hash()] = struct{}{}
 		q.resultCache[index].Pending--
+		useful = true
 
 		// Clean up a successful fetch
 		request.Headers[i] = nil
@@ -888,19 +892,16 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 			taskQueue.Push(header, -float32(header.Number.Uint64()))
 		}
 	}
-	// If none of the blocks were good, it's a stale delivery
+	// If none of the data was good, it's a stale delivery
 	switch {
-	case len(errs) == 0:
-		return nil
+	case failure == nil || failure == errInvalidChain:
+		return failure
 
-	case len(errs) == 1 && (errs[0] == errInvalidChain || errs[0] == errInvalidBody || errs[0] == errInvalidReceipt):
-		return errs[0]
-
-	case len(errs) == results:
-		return errStaleDelivery
+	case useful:
+		return fmt.Errorf("partial failure: %v", failure)
 
 	default:
-		return fmt.Errorf("multiple failures: %v", errs)
+		return errStaleDelivery
 	}
 }