net: push only raw data into CConnman

This fixes one of the last major layer violations in the networking stack.

The network side is no longer in charge of message serialization, so it is now
decoupled from Bitcoin structures. Only the header is serialized and attached
to the payload.

1 files changed, 71 insertions, 60 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 11c7b2ec6a..559538165c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -18,6 +18,7 @@
 #include "init.h"
 #include "merkleblock.h"
 #include "net.h"
+#include "netmessagemaker.h"
 #include "netbase.h"
 #include "policy/fees.h"
 #include "policy/policy.h"
@@ -368,8 +369,8 @@ void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
     CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService(), addr.nServices));
     CAddress addrMe = CAddress(CService(), nLocalNodeServices);
 
-    connman.PushMessageWithVersion(pnode, INIT_PROTO_VERSION, NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
-            nonce, strSubVersion, nNodeStartingHeight, ::fRelayTxes);
+    connman.PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
+            nonce, strSubVersion, nNodeStartingHeight, ::fRelayTxes));
 
     if (fLogIPs)
         LogPrint("net", "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), addrYou.ToString(), nodeid);
@@ -530,13 +531,13 @@ void MaybeSetPeerAsAnnouncingHeaderAndIDs(const CNodeState* nodestate, CNode* pf
             // As per BIP152, we only get 3 of our peers to announce
             // blocks using compact encodings.
             connman.ForNode(lNodesAnnouncingHeaderAndIDs.front(), [&connman, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion](CNode* pnodeStop){
-                connman.PushMessage(pnodeStop, NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
+                connman.PushMessage(pnodeStop, CNetMsgMaker(pnodeStop->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
                 return true;
             });
             lNodesAnnouncingHeaderAndIDs.pop_front();
         }
         fAnnounceUsingCMPCTBLOCK = true;
-        connman.PushMessage(pfrom, NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
+        connman.PushMessage(pfrom, CNetMsgMaker(pfrom->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
         lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
     }
 }
@@ -4893,9 +4894,8 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
 {
     std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
     unsigned int nMaxSendBufferSize = connman.GetSendBufferSize();
-
     vector<CInv> vNotFound;
-
+    CNetMsgMaker msgMaker(pfrom->GetSendVersion());
     LOCK(cs_main);
 
     while (it != pfrom->vRecvGetData.end()) {
@@ -4949,9 +4949,9 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                     if (!ReadBlockFromDisk(block, (*mi).second, consensusParams))
                         assert(!"cannot load block from disk");
                     if (inv.type == MSG_BLOCK)
-                        connman.PushMessageWithFlag(pfrom, SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, block);
+                        connman.PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, block));
                     else if (inv.type == MSG_WITNESS_BLOCK)
-                        connman.PushMessage(pfrom, NetMsgType::BLOCK, block);
+                        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::BLOCK, block));
                     else if (inv.type == MSG_FILTERED_BLOCK)
                     {
                         bool sendMerkleBlock = false;
@@ -4964,7 +4964,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                             }
                         }
                         if (sendMerkleBlock) {
-                            connman.PushMessage(pfrom, NetMsgType::MERKLEBLOCK, merkleBlock);
+                            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::MERKLEBLOCK, merkleBlock));
                             // CMerkleBlock just contains hashes, so also push any transactions in the block the client did not see
                             // This avoids hurting performance by pointlessly requiring a round-trip
                             // Note that there is currently no way for a node to request any single transactions we didn't send here -
@@ -4973,7 +4973,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                             // however we MUST always provide at least what the remote peer needs
                             typedef std::pair<unsigned int, uint256> PairType;
                             BOOST_FOREACH(PairType& pair, merkleBlock.vMatchedTxn)
-                                connman.PushMessageWithFlag(pfrom, SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *block.vtx[pair.first]);
+                                connman.PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *block.vtx[pair.first]));
                         }
                         // else
                             // no response
@@ -4985,11 +4985,12 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                         // and we don't feel like constructing the object for them, so
                         // instead we respond with the full, non-compact block.
                         bool fPeerWantsWitness = State(pfrom->GetId())->fWantsCmpctWitness;
+                        int nSendFlags = fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
                         if (CanDirectFetch(consensusParams) && mi->second->nHeight >= chainActive.Height() - MAX_CMPCTBLOCK_DEPTH) {
                             CBlockHeaderAndShortTxIDs cmpctblock(block, fPeerWantsWitness);
-                            connman.PushMessageWithFlag(pfrom, fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::CMPCTBLOCK, cmpctblock);
+                            connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                         } else
-                            connman.PushMessageWithFlag(pfrom, fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, block);
+                            connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCK, block));
                     }
 
                     // Trigger the peer node to send a getblocks request for the next batch of inventory
@@ -5000,7 +5001,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                         // wait for other stuff first.
                         vector<CInv> vInv;
                         vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
-                        connman.PushMessage(pfrom, NetMsgType::INV, vInv);
+                        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
                         pfrom->hashContinue.SetNull();
                     }
                 }
@@ -5010,15 +5011,16 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                 // Send stream from relay memory
                 bool push = false;
                 auto mi = mapRelay.find(inv.hash);
+                int nSendFlags = (inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0);
                 if (mi != mapRelay.end()) {
-                    connman.PushMessageWithFlag(pfrom, inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0, NetMsgType::TX, *mi->second);
+                    connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                     push = true;
                 } else if (pfrom->timeLastMempoolReq) {
                     auto txinfo = mempool.info(inv.hash);
                     // To protect privacy, do not answer getdata using the mempool when
                     // that TX couldn't have been INVed in reply to a MEMPOOL request.
                     if (txinfo.tx && txinfo.nTime <= pfrom->timeLastMempoolReq) {
-                        connman.PushMessageWithFlag(pfrom, inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0, NetMsgType::TX, *txinfo.tx);
+                        connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                         push = true;
                     }
                 }
@@ -5045,7 +5047,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
         // do that because they want to know about (and store and rebroadcast and
         // risk analyze) the dependencies of transactions relevant to them, without
         // having to download the entire memory pool.
-        connman.PushMessage(pfrom, NetMsgType::NOTFOUND, vNotFound);
+        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
     }
 }
 
@@ -5089,7 +5091,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // Each connection can only send one version message
         if (pfrom->nVersion != 0)
         {
-            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message"));
+            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message")));
             LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 1);
             return false;
@@ -5109,8 +5111,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         if (pfrom->nServicesExpected & ~pfrom->nServices)
         {
             LogPrint("net", "peer=%d does not offer the expected services (%08x offered, %08x expected); disconnecting\n", pfrom->id, pfrom->nServices, pfrom->nServicesExpected);
-            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
-                               strprintf("Expected to offer services %08x", pfrom->nServicesExpected));
+            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
+                               strprintf("Expected to offer services %08x", pfrom->nServicesExpected)));
             pfrom->fDisconnect = true;
             return false;
         }
@@ -5119,8 +5121,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         {
             // disconnect from peers older than this proto version
             LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, pfrom->nVersion);
-            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
-                               strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION));
+            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
+                               strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION)));
             pfrom->fDisconnect = true;
             return false;
         }
@@ -5177,8 +5179,9 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
 
         // Change version
-        connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::VERACK);
-        pfrom->SetSendVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
+        connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERACK));
+        int nSendVersion = std::min(pfrom->nVersion, PROTOCOL_VERSION);
+        pfrom->SetSendVersion(nSendVersion);
 
         if (!pfrom->fInbound)
         {
@@ -5201,7 +5204,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             // Get recent addresses
             if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman.GetAddressCount() < 1000)
             {
-                connman.PushMessage(pfrom, NetMsgType::GETADDR);
+                connman.PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make(NetMsgType::GETADDR));
                 pfrom->fGetAddr = true;
             }
             connman.MarkAddressGood(pfrom->addr);
@@ -5227,6 +5230,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             assert(pfrom->fInbound == false);
             pfrom->fDisconnect = true;
         }
+        return true;
     }
 
 
@@ -5238,8 +5242,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         return false;
     }
 
+    // At this point, the outgoing message serialization version can't change.
+    CNetMsgMaker msgMaker(pfrom->GetSendVersion());
 
-    else if (strCommand == NetMsgType::VERACK)
+    if (strCommand == NetMsgType::VERACK)
     {
         pfrom->SetRecvVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
 
@@ -5254,7 +5260,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             // We send this to non-NODE NETWORK peers as well, because even
             // non-NODE NETWORK peers can announce blocks (such as pruning
             // nodes)
-            connman.PushMessage(pfrom, NetMsgType::SENDHEADERS);
+            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
         }
         if (pfrom->nVersion >= SHORT_IDS_BLOCKS_VERSION) {
             // Tell our peer we are willing to provide version 1 or 2 cmpctblocks
@@ -5265,9 +5271,9 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             bool fAnnounceUsingCMPCTBLOCK = false;
             uint64_t nCMPCTBLOCKVersion = 2;
             if (pfrom->GetLocalServices() & NODE_WITNESS)
-                connman.PushMessage(pfrom, NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
             nCMPCTBLOCKVersion = 1;
-            connman.PushMessage(pfrom, NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
+            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
         }
     }
 
@@ -5392,7 +5398,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                     // fell back to inv we probably have a reorg which we should get the headers for first,
                     // we now only provide a getheaders response here. When we receive the headers, we will
                     // then ask for the blocks we need.
-                    connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash);
+                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash));
                     LogPrint("net", "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->id);
                 }
             }
@@ -5415,7 +5421,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
 
         if (!vToFetch.empty())
-            connman.PushMessage(pfrom, NetMsgType::GETDATA, vToFetch);
+            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vToFetch));
     }
 
 
@@ -5527,7 +5533,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             }
             resp.txn[i] = block.vtx[req.indexes[i]];
         }
-        connman.PushMessageWithFlag(pfrom, State(pfrom->GetId())->fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCKTXN, resp);
+        int nSendFlags = State(pfrom->GetId())->fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
+        connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
     }
 
 
@@ -5576,7 +5583,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // headers message). In both cases it's safe to update
         // pindexBestHeaderSent to be our tip.
         nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
-        connman.PushMessage(pfrom, NetMsgType::HEADERS, vHeaders);
+        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
     }
 
 
@@ -5739,8 +5746,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 pfrom->id,
                 FormatStateMessage(state));
             if (state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
-                connman.PushMessage(pfrom, NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
-                                   state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
+                                   state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash));
             if (nDoS > 0) {
                 Misbehaving(pfrom->GetId(), nDoS);
             }
@@ -5758,7 +5765,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         if (mapBlockIndex.find(cmpctblock.header.hashPrevBlock) == mapBlockIndex.end()) {
             // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
             if (!IsInitialBlockDownload())
-                connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256());
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
             return true;
         }
 
@@ -5791,7 +5798,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 // so we just grab the block via normal getdata
                 std::vector<CInv> vInv(1);
                 vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom, pindex->pprev, chainparams.GetConsensus()), cmpctblock.header.GetHash());
-                connman.PushMessage(pfrom, NetMsgType::GETDATA, vInv);
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
             }
             return true;
         }
@@ -5835,7 +5842,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                     // Duplicate txindexes, the block is now in-flight, so just request it
                     std::vector<CInv> vInv(1);
                     vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom, pindex->pprev, chainparams.GetConsensus()), cmpctblock.header.GetHash());
-                    connman.PushMessage(pfrom, NetMsgType::GETDATA, vInv);
+                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                     return true;
                 }
 
@@ -5859,7 +5866,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                     return ProcessMessage(pfrom, NetMsgType::BLOCKTXN, blockTxnMsg, nTimeReceived, chainparams, connman);
                 } else {
                     req.blockhash = pindex->GetBlockHash();
-                    connman.PushMessage(pfrom, NetMsgType::GETBLOCKTXN, req);
+                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETBLOCKTXN, req));
                 }
             }
         } else {
@@ -5868,7 +5875,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 // mempool will probably be useless - request the block normally
                 std::vector<CInv> vInv(1);
                 vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom, pindex->pprev, chainparams.GetConsensus()), cmpctblock.header.GetHash());
-                connman.PushMessage(pfrom, NetMsgType::GETDATA, vInv);
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                 return true;
             } else {
                 // If this was an announce-cmpctblock, we want the same treatment as a header message
@@ -5910,7 +5917,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 // Might have collided, fall back to getdata now :(
                 std::vector<CInv> invs;
                 invs.push_back(CInv(MSG_BLOCK | GetFetchFlags(pfrom, chainActive.Tip(), chainparams.GetConsensus()), resp.blockhash));
-                connman.PushMessage(pfrom, NetMsgType::GETDATA, invs);
+                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, invs));
             } else {
                 // Block is either okay, or possibly we received
                 // READ_STATUS_CHECKBLOCK_FAILED.
@@ -5987,7 +5994,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         //   nUnconnectingHeaders gets reset back to 0.
         if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
             nodestate->nUnconnectingHeaders++;
-            connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256());
+            connman.PushMessage(pfrom, msgMaker.Make(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(),
@@ -6034,7 +6041,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue
             // from there instead.
             LogPrint("net", "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->id, pfrom->nStartingHeight);
-            connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256());
+            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256()));
         }
 
         bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
@@ -6087,7 +6094,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                         // In any case, we want to download using a compact block, not a regular one
                         vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash);
                     }
-                    connman.PushMessage(pfrom, NetMsgType::GETDATA, vGetData);
+                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                 }
             }
         }
@@ -6191,7 +6198,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             // it, if the remote node sends a ping once per second and this node takes 5
             // seconds to respond to each, the 5th ping the remote sends would appear to
             // return very quickly.
-            connman.PushMessage(pfrom, NetMsgType::PONG, nonce);
+            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
         }
     }
 
@@ -6447,7 +6454,7 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman)
         }
         catch (const std::ios_base::failure& e)
         {
-            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_MALFORMED, string("error parsing message"));
+            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_MALFORMED, string("error parsing message")));
             if (strstr(e.what(), "end of data"))
             {
                 // Allow exceptions from under-length message on vRecv
@@ -6515,6 +6522,9 @@ bool SendMessages(CNode* pto, CConnman& connman)
         if (pto->nVersion == 0 || pto->fDisconnect)
             return true;
 
+        // If we get here, the outgoing message serialization version is set and can't change.
+        CNetMsgMaker msgMaker(pto->GetSendVersion());
+
         //
         // Message: ping
         //
@@ -6536,11 +6546,11 @@ bool SendMessages(CNode* pto, CConnman& connman)
             pto->nPingUsecStart = GetTimeMicros();
             if (pto->nVersion > BIP0031_VERSION) {
                 pto->nPingNonceSent = nonce;
-                connman.PushMessage(pto, NetMsgType::PING, nonce);
+                connman.PushMessage(pto, msgMaker.Make(NetMsgType::PING, nonce));
             } else {
                 // Peer is too old to support ping command with nonce, pong will never arrive.
                 pto->nPingNonceSent = 0;
-                connman.PushMessage(pto, NetMsgType::PING);
+                connman.PushMessage(pto, msgMaker.Make(NetMsgType::PING));
             }
         }
 
@@ -6551,7 +6561,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
         CNodeState &state = *State(pto->GetId());
 
         BOOST_FOREACH(const CBlockReject& reject, state.rejects)
-            connman.PushMessage(pto, NetMsgType::REJECT, (string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock);
+            connman.PushMessage(pto, msgMaker.Make(NetMsgType::REJECT, (string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock));
         state.rejects.clear();
 
         if (state.fShouldBan) {
@@ -6593,14 +6603,14 @@ bool SendMessages(CNode* pto, CConnman& connman)
                     // receiver rejects addr messages larger than 1000
                     if (vAddr.size() >= 1000)
                     {
-                        connman.PushMessage(pto, NetMsgType::ADDR, vAddr);
+                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
                         vAddr.clear();
                     }
                 }
             }
             pto->vAddrToSend.clear();
             if (!vAddr.empty())
-                connman.PushMessage(pto, NetMsgType::ADDR, vAddr);
+                connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
             // we only send the big addr message once
             if (pto->vAddrToSend.capacity() > 40)
                 pto->vAddrToSend.shrink_to_fit();
@@ -6626,7 +6636,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
                 if (pindexStart->pprev)
                     pindexStart = pindexStart->pprev;
                 LogPrint("net", "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->id, pto->nStartingHeight);
-                connman.PushMessage(pto, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256());
+                connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256()));
             }
         }
 
@@ -6715,7 +6725,8 @@ bool SendMessages(CNode* pto, CConnman& connman)
                     CBlock block;
                     assert(ReadBlockFromDisk(block, pBestIndex, consensusParams));
                     CBlockHeaderAndShortTxIDs cmpctblock(block, state.fWantsCmpctWitness);
-                    connman.PushMessageWithFlag(pto, state.fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::CMPCTBLOCK, cmpctblock);
+                    int nSendFlags = state.fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
+                    connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                     state.pindexBestHeaderSent = pBestIndex;
                 } else if (state.fPreferHeaders) {
                     if (vHeaders.size() > 1) {
@@ -6727,7 +6738,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
                         LogPrint("net", "%s: sending header %s to peer=%d\n", __func__,
                                 vHeaders.front().GetHash().ToString(), pto->id);
                     }
-                    connman.PushMessage(pto, NetMsgType::HEADERS, vHeaders);
+                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
                     state.pindexBestHeaderSent = pBestIndex;
                 } else
                     fRevertToInv = true;
@@ -6773,7 +6784,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
             BOOST_FOREACH(const uint256& hash, pto->vInventoryBlockToSend) {
                 vInv.push_back(CInv(MSG_BLOCK, hash));
                 if (vInv.size() == MAX_INV_SZ) {
-                    connman.PushMessage(pto, NetMsgType::INV, vInv);
+                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                     vInv.clear();
                 }
             }
@@ -6819,7 +6830,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
                     pto->filterInventoryKnown.insert(hash);
                     vInv.push_back(inv);
                     if (vInv.size() == MAX_INV_SZ) {
-                        connman.PushMessage(pto, NetMsgType::INV, vInv);
+                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                         vInv.clear();
                     }
                 }
@@ -6885,7 +6896,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
                         }
                     }
                     if (vInv.size() == MAX_INV_SZ) {
-                        connman.PushMessage(pto, NetMsgType::INV, vInv);
+                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                         vInv.clear();
                     }
                     pto->filterInventoryKnown.insert(hash);
@@ -6893,7 +6904,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
             }
         }
         if (!vInv.empty())
-            connman.PushMessage(pto, NetMsgType::INV, vInv);
+            connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
 
         // Detect whether we're stalling
         nNow = GetTimeMicros();
@@ -6956,7 +6967,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
                 vGetData.push_back(inv);
                 if (vGetData.size() >= 1000)
                 {
-                    connman.PushMessage(pto, NetMsgType::GETDATA, vGetData);
+                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                     vGetData.clear();
                 }
             } else {
@@ -6966,7 +6977,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
             pto->mapAskFor.erase(pto->mapAskFor.begin());
         }
         if (!vGetData.empty())
-            connman.PushMessage(pto, NetMsgType::GETDATA, vGetData);
+            connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
 
         //
         // Message: feefilter
@@ -6979,7 +6990,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
             if (timeNow > pto->nextSendTimeFeeFilter) {
                 CAmount filterToSend = filterRounder.round(currentFilter);
                 if (filterToSend != pto->lastSentFeeFilter) {
-                    connman.PushMessage(pto, NetMsgType::FEEFILTER, filterToSend);
+                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
                     pto->lastSentFeeFilter = filterToSend;
                 }
                 pto->nextSendTimeFeeFilter = PoissonNextSend(timeNow, AVG_FEEFILTER_BROADCAST_INTERVAL);