Don't grab queue up blocks we already know about.

libethcore/Common.h

@@ -90,7 +90,8 @@ enum class ImportResult
 	AlreadyInChain,
 	AlreadyKnown,
 	Malformed,
-	BadChain
+	BadChain,
+	Unknown
 };
 
 struct ImportRequirements

libethereum/BlockQueue.h

@@ -86,6 +86,9 @@ public:
 	/// Get some infomration on the current status.
 	BlockQueueStatus status() const { ReadGuard l(m_lock); return BlockQueueStatus{m_ready.size(), m_future.size(), m_unknown.size(), m_knownBad.size()}; }
 
+	/// Get some infomration on the given block's status regarding us.
+	ImportResult blockStatus(h256 const& _h) const { ReadGuard l(m_lock); return m_readySet.count(_h) || m_drainingSet.count(_h) ? ImportResult::AlreadyKnown : m_unknownSet.count(_h) ? ImportResult::UnknownParent : m_knownBad.count(_h) ? ImportResult::BadChain : ImportResult::Unknown; }
+
 	template <class T> Handler onReady(T const& _t) { return m_onReady.add(_t); }
 
 private:

libethereum/EthereumPeer.cpp

@@ -389,7 +389,7 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 		{
 			addRating(1);
 			auto h = _r[i].toHash<h256>();
-			if (host()->m_chain.isKnown(h))
+			if (host()->m_bq.blockStatus(h) != ImportResult::Unknown || host()->m_chain.isKnown(h))
 			{
 				transition(Asking::Blocks);
 				return true;
@@ -484,6 +484,8 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 				case ImportResult::UnknownParent:
 					unknown++;
 					break;
+
+				default:;
 				}
 			}
 			else
@@ -535,6 +537,7 @@ bool EthereumPeer::interpret(unsigned _id, RLP const& _r)
 				clog(NetMessageSummary) << "Received block with no known parent. Resyncing...";
 				setNeedsSyncing(h, _r[1].toInt<u256>());
 				break;
+			default:;
 			}
 
 			Guard l(x_knownBlocks);