From e2652002b6011f793185d473f87f1730c625593b Mon Sep 17 00:00:00 2001
From: Suhas Daftuar <sdaftuar@chaincode.com>
Date: Fri, 5 May 2017 14:37:01 -0400
Subject: [PATCH] Delay parallel block download until chain has sufficient work

nMinimumChainWork is an anti-DoS threshold; wait until we have a proposed
tip with more work than that before downloading blocks towards that tip.
---
 src/net_processing.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 4d924b5cd..e4d8d62a2 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -480,7 +480,7 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con
     // Make sure pindexBestKnownBlock is up to date, we'll need it.
     ProcessBlockAvailability(nodeid);
 
-    if (state->pindexBestKnownBlock == NULL || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork) {
+    if (state->pindexBestKnownBlock == NULL || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork || state->pindexBestKnownBlock->nChainWork < UintToArith256(consensusParams.nMinimumChainWork)) {
         // This peer has nothing interesting.
         return;
     }