1 files changed, 43 insertions, 7 deletions

diff --git a/src/main.cpp b/src/main.cpp
index b86bbda1b8..73fbe53afb 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -276,6 +276,8 @@ struct CNodeState {
     CBlockIndex *pindexLastCommonBlock;
     //! The best header we have sent our peer.
     CBlockIndex *pindexBestHeaderSent;
+    //! Length of current-streak of unconnecting headers announcements
+    int nUnconnectingHeaders;
     //! Whether we've started headers synchronization with this peer.
     bool fSyncStarted;
     //! Since when we're stalling block download progress (in microseconds), or 0.
@@ -304,6 +306,7 @@ struct CNodeState {
         hashLastUnknownBlock.SetNull();
         pindexLastCommonBlock = NULL;
         pindexBestHeaderSent = NULL;
+        nUnconnectingHeaders = 0;
         fSyncStarted = false;
         nStallingSince = 0;
         nDownloadingSince = 0;
@@ -1132,11 +1135,6 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
     if (tx.IsCoinBase())
         return state.DoS(100, false, REJECT_INVALID, "coinbase");
 
-    // Rather not work on nonstandard transactions (unless -testnet/-regtest)
-    string reason;
-    if (fRequireStandard && !IsStandardTx(tx, reason))
-        return state.DoS(0, false, REJECT_NONSTANDARD, reason);
-
     // Don't relay version 2 transactions until CSV is active, and we can be
     // sure that such transactions will be mined (unless we're on
     // -testnet/-regtest).
@@ -1150,6 +1148,11 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         return state.DoS(0, false, REJECT_NONSTANDARD, "no-witness-yet", true);
     }
 
+    // Rather not work on nonstandard transactions (unless -testnet/-regtest)
+    string reason;
+    if (fRequireStandard && !IsStandardTx(tx, reason))
+        return state.DoS(0, false, REJECT_NONSTANDARD, reason);
+
     // Only accept nLockTime-using transactions that can be mined in the next
     // block; we don't want our mempool filled up with transactions that can't
     // be mined yet.
@@ -5773,6 +5776,35 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             return true;
         }
 
+        CNodeState *nodestate = State(pfrom->GetId());
+
+        // If this looks like it could be a block announcement (nCount <
+        // MAX_BLOCKS_TO_ANNOUNCE), use special logic for handling headers that
+        // don't connect:
+        // - Send a getheaders message in response to try to connect the chain.
+        // - The peer can send up to MAX_UNCONNECTING_HEADERS in a row that
+        //   don't connect before giving DoS points
+        // - Once a headers message is received that is valid and does connect,
+        //   nUnconnectingHeaders gets reset back to 0.
+        if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
+            nodestate->nUnconnectingHeaders++;
+            pfrom->PushMessage(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256());
+            LogPrint("net", "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
+                    headers[0].GetHash().ToString(),
+                    headers[0].hashPrevBlock.ToString(),
+                    pindexBestHeader->nHeight,
+                    pfrom->id, nodestate->nUnconnectingHeaders);
+            // Set hashLastUnknownBlock for this peer, so that if we
+            // eventually get the headers - even from a different peer -
+            // we can use this peer to download.
+            UpdateBlockAvailability(pfrom->GetId(), headers.back().GetHash());
+
+            if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
+                Misbehaving(pfrom->GetId(), 20);
+            }
+            return true;
+        }
+
         CBlockIndex *pindexLast = NULL;
         BOOST_FOREACH(const CBlockHeader& header, headers) {
             CValidationState state;
@@ -5790,6 +5822,11 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             }
         }
 
+        if (nodestate->nUnconnectingHeaders > 0) {
+            LogPrint("net", "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->id, nodestate->nUnconnectingHeaders);
+        }
+        nodestate->nUnconnectingHeaders = 0;
+
         assert(pindexLast);
         UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
 
@@ -5802,7 +5839,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
 
         bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
-        CNodeState *nodestate = State(pfrom->GetId());
         // If this set of headers is valid and ends in a block with at least as
         // much work as our tip, download as much as possible.
         if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
@@ -6469,7 +6505,7 @@ bool SendMessages(CNode* pto)
                     CBlock block;
                     assert(ReadBlockFromDisk(block, pBestIndex, consensusParams));
                     CBlockHeaderAndShortTxIDs cmpctblock(block);
-                    pto->PushMessage(NetMsgType::CMPCTBLOCK, cmpctblock);
+                    pto->PushMessageWithFlag(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::CMPCTBLOCK, cmpctblock);
                     state.pindexBestHeaderSent = pBestIndex;
                 } else if (state.fPreferHeaders) {
                     if (vHeaders.size() > 1) {