MWEB: P2P: NODE_MWEB service flag

src/init.cpp

@@ -1852,6 +1852,8 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
         nLocalServices = ServiceFlags(nLocalServices | NODE_WITNESS);
     }
 
+    nLocalServices = ServiceFlags(nLocalServices | NODE_MWEB);
+
     // ********************************************************* Step 11: import blocks
 
     if (!CheckDiskSpace(GetDataDir())) {

src/net.h

@@ -1199,6 +1199,8 @@ public:
         return nLocalServices;
     }
 
+    bool SupportsMWEB() const noexcept { return (nLocalServices & NODE_MWEB); }
+
     std::string GetAddrName() const;
     //! Sets the addrName only if it was not previously set
     void MaybeSetAddrName(const std::string& addrNameIn);

src/net_processing.cpp

@@ -327,6 +327,8 @@ struct CNodeState {
     bool fProvidesHeaderAndIDs;
     //! Whether this peer can give us witnesses
     bool fHaveWitness;
+    //! Whether this peer can give us MWEB data
+    bool fHaveMWEB;
     //! Whether this peer wants witnesses in cmpctblocks/blocktxns
     bool fWantsCmpctWitness;
     /**
@@ -407,6 +409,7 @@ struct CNodeState {
         fPreferHeaderAndIDs = false;
         fProvidesHeaderAndIDs = false;
         fHaveWitness = false;
+        fHaveMWEB = false;
         fWantsCmpctWitness = false;
         fSupportsDesiredCmpctVersion = false;
         m_chain_sync = { 0, nullptr, false, false };
@@ -736,6 +739,10 @@ static void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vec
                 // We wouldn't download this block or its descendants from this peer.
                 return;
             }
+            if (!State(nodeid)->fHaveMWEB && IsMWEBEnabled(pindex->pprev, consensusParams)) {
+                // MWEB: Can't download this block from this peer.
+                return;
+            }
             if (pindex->nStatus & BLOCK_HAVE_DATA || ::ChainActive().Contains(pindex)) {
                 if (pindex->HaveTxsDownloaded())
                     state->pindexLastCommonBlock = pindex;
@@ -1698,7 +1705,7 @@ void static ProcessGetData(CNode& pfrom, Peer& peer, const CChainParams& chainpa
         CTransactionRef tx = FindTxForGetData(mempool, pfrom, ToGenTxid(inv), mempool_req, now);
         if (tx) {
             // WTX and WITNESS_TX imply we serialize with witness
-            int nSendFlags = (inv.IsMsgTx() ? SERIALIZE_TRANSACTION_NO_WITNESS : 0);
+            int nSendFlags = (inv.IsMsgTx() ? SERIALIZE_TRANSACTION_NO_WITNESS | SERIALIZE_NO_MWEB : (pfrom.SupportsMWEB() ? 0 : SERIALIZE_NO_MWEB));
             connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *tx));
             mempool.RemoveUnbroadcastTx(tx->GetHash());
             // As we're going to send tx, make sure its unconfirmed parents are made requestable.
@@ -1887,7 +1894,8 @@ void PeerManager::ProcessHeadersMessage(CNode& pfrom, const std::vector<CBlockHe
             while (pindexWalk && !::ChainActive().Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                 if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
                         !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) &&
-                        (!IsWitnessEnabled(pindexWalk->pprev, m_chainparams.GetConsensus()) || State(pfrom.GetId())->fHaveWitness)) {
+                        (!IsWitnessEnabled(pindexWalk->pprev, m_chainparams.GetConsensus()) || State(pfrom.GetId())->fHaveWitness) &&
+                        (!IsMWEBEnabled(pindexWalk->pprev, m_chainparams.GetConsensus()) || State(pfrom.GetId())->fHaveMWEB)) {
                     // We don't have this block, and it's not yet in flight.
                     vToFetch.push_back(pindexWalk);
                 }
@@ -2401,6 +2409,10 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
         {
             LOCK(cs_main);
             State(pfrom.GetId())->fHaveWitness = true;
+
+            if (nServices & NODE_MWEB) {
+                State(pfrom.GetId())->fHaveMWEB = true;
+            }
         }
 
         // Potentially mark this peer as a preferred download peer.

src/protocol.cpp

@@ -137,9 +137,9 @@ bool CMessageHeader::IsCommandValid() const
 
 ServiceFlags GetDesirableServiceFlags(ServiceFlags services) {
     if ((services & NODE_NETWORK_LIMITED) && g_initial_block_download_completed) {
-        return ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS);
+        return ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS | NODE_MWEB);
     }
-    return ServiceFlags(NODE_NETWORK | NODE_WITNESS);
+    return ServiceFlags(NODE_NETWORK | NODE_WITNESS | NODE_MWEB);
 }
 
 void SetServiceFlagsIBDCache(bool state) {
@@ -208,6 +208,7 @@ static std::string serviceFlagToStr(size_t bit)
     case NODE_WITNESS:         return "WITNESS";
     case NODE_COMPACT_FILTERS: return "COMPACT_FILTERS";
     case NODE_NETWORK_LIMITED: return "NETWORK_LIMITED";
+    case NODE_MWEB:            return "MWEB";
     // Not using default, so we get warned when a case is missing
     }
 

src/protocol.h

@@ -291,8 +291,11 @@ enum ServiceFlags : uint64_t {
     // serving the last 288 (2 day) blocks
     // See BIP159 for details on how this is implemented.
     NODE_NETWORK_LIMITED = (1 << 10),
+    // NODE_MWEB indicates that a node can be asked for blocks and transactions including
+    // MWEB data.
+    NODE_MWEB = (1 << 24)
 
-    // Bits 24-31 are reserved for temporary experiments. Just pick a bit that
+    // Bits 25-31 are reserved for temporary experiments. Just pick a bit that
     // isn't getting used, or one not being used much, and notify the
     // bitcoin-development mailing list. Remember that service bits are just
     // unauthenticated advertisements, so your code must be robust against