Cache most-recently-connected compact block

Author: TheBlueMatt

src/net_processing.cpp

@@ -754,10 +754,11 @@ void PeerLogicValidation::SyncTransaction(const CTransaction& tx, const CBlockIn
 
 static CCriticalSection cs_most_recent_block;
 static std::shared_ptr<const CBlock> most_recent_block;
+static std::shared_ptr<CBlockHeaderAndShortTxIDs> most_recent_compact_block;
 static uint256 most_recent_block_hash;
 
 void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) {
-    CBlockHeaderAndShortTxIDs cmpctblock(*pblock, true);
+    std::shared_ptr<CBlockHeaderAndShortTxIDs> pcmpctblock = std::make_shared<CBlockHeaderAndShortTxIDs> (*pblock, true);
     CNetMsgMaker msgMaker(PROTOCOL_VERSION);
 
     LOCK(cs_main);
@@ -774,9 +775,10 @@ void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std:
         LOCK(cs_most_recent_block);
         most_recent_block_hash = hashBlock;
         most_recent_block = pblock;
+        most_recent_compact_block = pcmpctblock;
     }
 
-    connman->ForEachNode([this, &cmpctblock, pindex, &msgMaker, fWitnessEnabled, &hashBlock](CNode* pnode) {
+    connman->ForEachNode([this, &pcmpctblock, pindex, &msgMaker, fWitnessEnabled, &hashBlock](CNode* pnode) {
         // TODO: Avoid the repeated-serialization here
         if (pnode->nVersion < INVALID_CB_NO_BAN_VERSION || pnode->fDisconnect)
             return;
@@ -789,7 +791,7 @@ void PeerLogicValidation::NewPoWValidBlock(const CBlockIndex *pindex, const std:
 
             LogPrint("net", "%s sending header-and-ids %s to peer %d\n", "PeerLogicValidation::NewPoWValidBlock",
                     hashBlock.ToString(), pnode->id);
-            connman->PushMessage(pnode, msgMaker.Make(NetMsgType::CMPCTBLOCK, cmpctblock));
+            connman->PushMessage(pnode, msgMaker.Make(NetMsgType::CMPCTBLOCK, *pcmpctblock));
             state.pindexBestHeaderSent = pindex;
         }
     });
@@ -2859,13 +2861,24 @@ bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsg
                     // probably means we're doing an initial-ish-sync or they're slow
                     LogPrint("net", "%s sending header-and-ids %s to peer %d\n", __func__,
                             vHeaders.front().GetHash().ToString(), pto->id);
-                    //TODO: Shouldn't need to reload block from disk, but requires refactor
-                    CBlock block;
-                    bool ret = ReadBlockFromDisk(block, pBestIndex, consensusParams);
-                    assert(ret);
-                    CBlockHeaderAndShortTxIDs cmpctblock(block, state.fWantsCmpctWitness);
+
                     int nSendFlags = state.fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
-                    connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+
+                    LOCK(cs_most_recent_block);
+                    if (most_recent_block_hash == pBestIndex->GetBlockHash()) {
+                        if (state.fWantsCmpctWitness)
+                            connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *most_recent_compact_block));
+                        else {
+                            CBlockHeaderAndShortTxIDs cmpctblock(*most_recent_block, state.fWantsCmpctWitness);
+                            connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+                        }
+                    } else {
+                        CBlock block;
+                        bool ret = ReadBlockFromDisk(block, pBestIndex, consensusParams);
+                        assert(ret);
+                        CBlockHeaderAndShortTxIDs cmpctblock(block, state.fWantsCmpctWitness);
+                        connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+                    }
                     state.pindexBestHeaderSent = pBestIndex;
                 } else if (state.fPreferHeaders) {
                     if (vHeaders.size() > 1) {