1 files changed, 18 insertions, 5 deletions
diff --git a/src/main.cpp b/src/main.cpp
index 83e85f3d24..c6b82bf825 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3702,6 +3702,11 @@ static bool AcceptBlock(const CBlock& block, CValidationState& state, const CCha
     // not process unrequested blocks.
     bool fTooFarAhead = (pindex->nHeight > int(chainActive.Height() + MIN_BLOCKS_TO_KEEP));
 
+    // TODO: Decouple this function from the block download logic by removing fRequested
+    // This requires some new chain datastructure to efficiently look up if a
+    // block is in a chain leading to a candidate for best tip, despite not
+    // being such a candidate itself.
+
     // TODO: deal better with return value and error conditions for duplicate
     // and unrequested blocks.
     if (fAlreadyHave) return true;
@@ -3750,13 +3755,11 @@ bool ProcessNewBlock(CValidationState& state, const CChainParams& chainparams, C
 {
     {
         LOCK(cs_main);
-        bool fRequested = MarkBlockAsReceived(pblock->GetHash());
-        fRequested |= fForceProcessing;
 
         // Store to disk
         CBlockIndex *pindex = NULL;
         bool fNewBlock = false;
-        bool ret = AcceptBlock(*pblock, state, chainparams, &pindex, fRequested, dbp, &fNewBlock);
+        bool ret = AcceptBlock(*pblock, state, chainparams, &pindex, fForceProcessing, dbp, &fNewBlock);
         if (pindex && pfrom) {
             mapBlockSource[pindex->GetBlockHash()] = pfrom->GetId();
             if (fNewBlock) pfrom->nLastBlockTime = GetTime();
@@ -5858,12 +5861,16 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 std::vector<CInv> invs;
                 invs.push_back(CInv(MSG_BLOCK | GetFetchFlags(pfrom, chainActive.Tip(), chainparams.GetConsensus()), resp.blockhash));
                 pfrom->PushMessage(NetMsgType::GETDATA, invs);
-            } else
+            } else {
+                MarkBlockAsReceived(resp.blockhash); // it is now an empty pointer
                 fBlockRead = true;
+            }
         } // Don't hold cs_main when we call into ProcessNewBlock
         if (fBlockRead) {
             CValidationState state;
-            ProcessNewBlock(state, chainparams, pfrom, &block, false, NULL);
+            // Since we requested this block (it was in mapBlocksInFlight), force it to be processed,
+            // even if it would not be a candidate for new tip (missing previous block, chain not long enough, etc)
+            ProcessNewBlock(state, chainparams, pfrom, &block, true, NULL);
             int nDoS;
             if (state.IsInvalid(nDoS)) {
                 assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
@@ -6039,6 +6046,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // Such an unrequested block may still be processed, subject to the
         // conditions in AcceptBlock().
         bool forceProcessing = pfrom->fWhitelisted && !IsInitialBlockDownload();
+        {
+            LOCK(cs_main);
+            // Also always process if we requested the block explicitly, as we may
+            // need it even though it is not a candidate for a new best tip.
+            forceProcessing |= MarkBlockAsReceived(block.GetHash());
+        }
         ProcessNewBlock(state, chainparams, pfrom, &block, forceProcessing, NULL);
         int nDoS;
         if (state.IsInvalid(nDoS)) {