Merge #15759: p2p: Add 2 outbound block-relay-only connections

0ba08020c9791f7caf5986ad6490c16a2b66cd83 Disconnect peers violating blocks-only mode (Suhas Daftuar)
937eba91e1550bc3038dc541c236ac83e0a0e6d5 doc: improve comments relating to block-relay-only peers (Suhas Daftuar)
430f489027f15c1e4948ea4378954df24e3fee88 Don't relay addr messages to block-relay-only peers (Suhas Daftuar)
3a5e885306ea954d7eccdc11502e91a51dab8ec6 Add 2 outbound block-relay-only connections (Suhas Daftuar)
b83f51a4bbe29bf130a2b0c0e85e5bffea107f75 Add comment explaining intended use of m_tx_relay (Suhas Daftuar)
e75c39cd425f8c4e5b6bbb2beecb9c80034fefe1 Check that tx_relay is initialized before access (Suhas Daftuar)
c4aa2ba82211ea5988ed7fe21e1b08bc3367e6d4 [refactor] Change tx_relay structure to be unique_ptr (Suhas Daftuar)
4de0dbac9b286c42a9b10132b7c2d76712f1a319 [refactor] Move tx relay state to separate structure (Suhas Daftuar)
26a93bce29fd813e1402b013f402869c25b656d1 Remove unused variable (Suhas Daftuar)

Pull request description:

  Transaction relay is optimized for a combination of redundancy/robustness as well as bandwidth minimization -- as a result transaction relay leaks information that adversaries can use to infer the network topology.

  Network topology is better kept private for (at least) two reasons:

  (a) Knowledge of the network graph can make it easier to find the source IP of a given transaction.

  (b) Knowledge of the network graph could be used to split a target node or nodes from the honest network (eg by knowing which peers to attack in order to achieve a network split).

  We can eliminate the risks of (b) by separating block relay from transaction relay; inferring network connectivity from the relay of blocks/block headers is much more expensive for an adversary.

  After this commit, bitcoind will make 2 additional outbound connections that are only used for block relay. (In the future, we might consider rotating our transaction-relay peers to help limit the effects of (a).)

ACKs for top commit:
  sipa:
    ACK 0ba08020c9791f7caf5986ad6490c16a2b66cd83
  ajtowns:
    ACK 0ba08020c9791f7caf5986ad6490c16a2b66cd83 -- code review, ran tests. ran it on mainnet for a couple of days with MAX_BLOCKS_ONLY_CONNECTIONS upped from 2 to 16 and didn't observe any unexpected behaviour: it disconnected a couple of peers that tried sending inv's, and it successfully did compact block relay with some block relay peers.
  TheBlueMatt:
    re-utACK 0ba08020c9791f7caf5986ad6490c16a2b66cd83. Pointed out that stats.fRelayTxes was sometimes uninitialized for blocksonly peers (though its not a big deal and only effects RPC), which has since been fixed here. Otherwise changes are pretty trivial so looks good.
  jnewbery:
    utACK 0ba08020c9791f7caf5986ad6490c16a2b66cd83
  jamesob:
    ACK https://github.com/bitcoin/bitcoin/commit/0ba08020c9791f7caf5986ad6490c16a2b66cd83

Tree-SHA512: 4c3629434472c7dd4125253417b1be41967a508c3cfec8af5a34cad685464fbebbb6558f0f8f5c0d4463e3ffa4fa3aabd58247692cb9ab8395f4993078b9bcdf

5 files changed, 305 insertions, 222 deletions

diff --git a/src/init.cpp b/src/init.cpp
index ca419c05fa..ee49ac1914 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1760,7 +1760,8 @@ bool AppInitMain(InitInterfaces& interfaces)
     CConnman::Options connOptions;
     connOptions.nLocalServices = nLocalServices;
     connOptions.nMaxConnections = nMaxConnections;
-    connOptions.nMaxOutbound = std::min(MAX_OUTBOUND_CONNECTIONS, connOptions.nMaxConnections);
+    connOptions.m_max_outbound_full_relay = std::min(MAX_OUTBOUND_FULL_RELAY_CONNECTIONS, connOptions.nMaxConnections);
+    connOptions.m_max_outbound_block_relay = std::min(MAX_BLOCKS_ONLY_CONNECTIONS, connOptions.nMaxConnections-connOptions.m_max_outbound_full_relay);
     connOptions.nMaxAddnode = MAX_ADDNODE_CONNECTIONS;
     connOptions.nMaxFeeler = 1;
     connOptions.nBestHeight = chain_active_height;
diff --git a/src/net.cpp b/src/net.cpp
index 337d1f6a46..89f82aa3d2 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -352,7 +352,7 @@ static CAddress GetBindAddress(SOCKET sock)
     return addr_bind;
 }
 
-CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection)
+CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection, bool block_relay_only)
 {
     if (pszDest == nullptr) {
         if (IsLocal(addrConnect))
@@ -442,7 +442,7 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
     NodeId id = GetNewNodeId();
     uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();
     CAddress addr_bind = GetBindAddress(hSocket);
-    CNode* pnode = new CNode(id, nLocalServices, GetBestHeight(), hSocket, addrConnect, CalculateKeyedNetGroup(addrConnect), nonce, addr_bind, pszDest ? pszDest : "", false);
+    CNode* pnode = new CNode(id, nLocalServices, GetBestHeight(), hSocket, addrConnect, CalculateKeyedNetGroup(addrConnect), nonce, addr_bind, pszDest ? pszDest : "", false, block_relay_only);
     pnode->AddRef();
 
     return pnode;
@@ -499,9 +499,11 @@ void CNode::copyStats(CNodeStats &stats)
     X(nServices);
     X(addr);
     X(addrBind);
-    {
-        LOCK(cs_filter);
-        X(fRelayTxes);
+    if (m_tx_relay != nullptr) {
+        LOCK(m_tx_relay->cs_filter);
+        stats.fRelayTxes = m_tx_relay->fRelayTxes;
+    } else {
+        stats.fRelayTxes = false;
     }
     X(nLastSend);
     X(nLastRecv);
@@ -528,9 +530,11 @@ void CNode::copyStats(CNodeStats &stats)
     }
     X(m_legacyWhitelisted);
     X(m_permissionFlags);
-    {
-        LOCK(cs_feeFilter);
-        X(minFeeFilter);
+    if (m_tx_relay != nullptr) {
+        LOCK(m_tx_relay->cs_feeFilter);
+        stats.minFeeFilter = m_tx_relay->minFeeFilter;
+    } else {
+        stats.minFeeFilter = 0;
     }
 
     // It is common for nodes with good ping times to suddenly become lagged,
@@ -818,11 +822,17 @@ bool CConnman::AttemptToEvictConnection()
                 continue;
             if (node->fDisconnect)
                 continue;
-            LOCK(node->cs_filter);
+            bool peer_relay_txes = false;
+            bool peer_filter_not_null = false;
+            if (node->m_tx_relay != nullptr) {
+                LOCK(node->m_tx_relay->cs_filter);
+                peer_relay_txes = node->m_tx_relay->fRelayTxes;
+                peer_filter_not_null = node->m_tx_relay->pfilter != nullptr;
+            }
             NodeEvictionCandidate candidate = {node->GetId(), node->nTimeConnected, node->nMinPingUsecTime,
                                                node->nLastBlockTime, node->nLastTXTime,
                                                HasAllDesirableServiceFlags(node->nServices),
-                                               node->fRelayTxes, node->pfilter != nullptr, node->addr, node->nKeyedNetGroup,
+                                               peer_relay_txes, peer_filter_not_null, node->addr, node->nKeyedNetGroup,
                                                node->m_prefer_evict};
             vEvictionCandidates.push_back(candidate);
         }
@@ -895,7 +905,7 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
     SOCKET hSocket = accept(hListenSocket.socket, (struct sockaddr*)&sockaddr, &len);
     CAddress addr;
     int nInbound = 0;
-    int nMaxInbound = nMaxConnections - (nMaxOutbound + nMaxFeeler);
+    int nMaxInbound = nMaxConnections - m_max_outbound;
 
     if (hSocket != INVALID_SOCKET) {
         if (!addr.SetSockAddr((const struct sockaddr*)&sockaddr)) {
@@ -1655,7 +1665,7 @@ int CConnman::GetExtraOutboundCount()
             }
         }
     }
-    return std::max(nOutbound - nMaxOutbound, 0);
+    return std::max(nOutbound - m_max_outbound_full_relay - m_max_outbound_block_relay, 0);
 }
 
 void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
@@ -1715,7 +1725,8 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
         CAddress addrConnect;
 
         // Only connect out to one peer per network group (/16 for IPv4).
-        int nOutbound = 0;
+        int nOutboundFullRelay = 0;
+        int nOutboundBlockRelay = 0;
         std::set<std::vector<unsigned char> > setConnected;
         {
             LOCK(cs_vNodes);
@@ -1727,7 +1738,11 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
                     // also have the added issue that they're attacker controlled and could be used
                     // to prevent us from connecting to particular hosts if we used them here.
                     setConnected.insert(pnode->addr.GetGroup());
-                    nOutbound++;
+                    if (pnode->m_tx_relay == nullptr) {
+                        nOutboundBlockRelay++;
+                    } else if (!pnode->fFeeler) {
+                        nOutboundFullRelay++;
+                    }
                 }
             }
         }
@@ -1746,7 +1761,7 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
         //
         bool fFeeler = false;
 
-        if (nOutbound >= nMaxOutbound && !GetTryNewOutboundPeer()) {
+        if (nOutboundFullRelay >= m_max_outbound_full_relay && nOutboundBlockRelay >= m_max_outbound_block_relay && !GetTryNewOutboundPeer()) {
             int64_t nTime = GetTimeMicros(); // The current time right now (in microseconds).
             if (nTime > nNextFeeler) {
                 nNextFeeler = PoissonNextSend(nTime, FEELER_INTERVAL);
@@ -1820,7 +1835,14 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
                 LogPrint(BCLog::NET, "Making feeler connection to %s\n", addrConnect.ToString());
             }
 
-            OpenNetworkConnection(addrConnect, (int)setConnected.size() >= std::min(nMaxConnections - 1, 2), &grant, nullptr, false, fFeeler);
+            // Open this connection as block-relay-only if we're already at our
+            // full-relay capacity, but not yet at our block-relay peer limit.
+            // (It should not be possible for fFeeler to be set if we're not
+            // also at our block-relay peer limit, but check against that as
+            // well for sanity.)
+            bool block_relay_only = nOutboundBlockRelay < m_max_outbound_block_relay && !fFeeler && nOutboundFullRelay >= m_max_outbound_full_relay;
+
+            OpenNetworkConnection(addrConnect, (int)setConnected.size() >= std::min(nMaxConnections - 1, 2), &grant, nullptr, false, fFeeler, false, block_relay_only);
         }
     }
 }
@@ -1907,7 +1929,7 @@ void CConnman::ThreadOpenAddedConnections()
 }
 
 // if successful, this moves the passed grant to the constructed node
-void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound, const char *pszDest, bool fOneShot, bool fFeeler, bool manual_connection)
+void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound, const char *pszDest, bool fOneShot, bool fFeeler, bool manual_connection, bool block_relay_only)
 {
     //
     // Initiate outbound network connection
@@ -1926,7 +1948,7 @@ void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFai
     } else if (FindNode(std::string(pszDest)))
         return;
 
-    CNode* pnode = ConnectNode(addrConnect, pszDest, fCountFailure, manual_connection);
+    CNode* pnode = ConnectNode(addrConnect, pszDest, fCountFailure, manual_connection, block_relay_only);
 
     if (!pnode)
         return;
@@ -2229,7 +2251,7 @@ bool CConnman::Start(CScheduler& scheduler, const Options& connOptions)
 
     if (semOutbound == nullptr) {
         // initialize semaphore
-        semOutbound = MakeUnique<CSemaphore>(std::min((nMaxOutbound + nMaxFeeler), nMaxConnections));
+        semOutbound = MakeUnique<CSemaphore>(std::min(m_max_outbound, nMaxConnections));
     }
     if (semAddnode == nullptr) {
         // initialize semaphore
@@ -2307,7 +2329,7 @@ void CConnman::Interrupt()
     InterruptSocks5(true);
 
     if (semOutbound) {
-        for (int i=0; i<(nMaxOutbound + nMaxFeeler); i++) {
+        for (int i=0; i<m_max_outbound; i++) {
             semOutbound->post();
         }
     }
@@ -2617,14 +2639,17 @@ int CConnman::GetBestHeight() const
 
 unsigned int CConnman::GetReceiveFloodSize() const { return nReceiveFloodSize; }
 
-CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress& addrBindIn, const std::string& addrNameIn, bool fInboundIn)
+CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress& addrBindIn, const std::string& addrNameIn, bool fInboundIn, bool block_relay_only)
     : nTimeConnected(GetSystemTimeInSeconds()),
     addr(addrIn),
     addrBind(addrBindIn),
     fInbound(fInboundIn),
     nKeyedNetGroup(nKeyedNetGroupIn),
     addrKnown(5000, 0.001),
-    filterInventoryKnown(50000, 0.000001),
+    // Don't relay addr messages to peers that we connect to as block-relay-only
+    // peers (to prevent adversaries from inferring these links from addr
+    // traffic).
+    m_addr_relay_peer(!block_relay_only),
     id(idIn),
     nLocalHostNonce(nLocalHostNonceIn),
     nLocalServices(nLocalServicesIn),
@@ -2633,8 +2658,9 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
     hSocket = hSocketIn;
     addrName = addrNameIn == "" ? addr.ToStringIPPort() : addrNameIn;
     hashContinue = uint256();
-    filterInventoryKnown.reset();
-    pfilter = MakeUnique<CBloomFilter>();
+    if (!block_relay_only) {
+        m_tx_relay = MakeUnique<TxRelay>();
+    }
 
     for (const std::string &msg : getAllNetMessageTypes())
         mapRecvBytesPerMsgCmd[msg] = 0;
diff --git a/src/net.h b/src/net.h
index 6c77d8135f..e9ea0162c9 100644
--- a/src/net.h
+++ b/src/net.h
@@ -61,10 +61,12 @@ static const unsigned int MAX_ADDR_TO_SEND = 1000;
 static const unsigned int MAX_PROTOCOL_MESSAGE_LENGTH = 4 * 1000 * 1000;
 /** Maximum length of the user agent string in `version` message */
 static const unsigned int MAX_SUBVERSION_LENGTH = 256;
-/** Maximum number of automatic outgoing nodes */
-static const int MAX_OUTBOUND_CONNECTIONS = 8;
+/** Maximum number of automatic outgoing nodes over which we'll relay everything (blocks, tx, addrs, etc) */
+static const int MAX_OUTBOUND_FULL_RELAY_CONNECTIONS = 8;
 /** Maximum number of addnode outgoing nodes */
 static const int MAX_ADDNODE_CONNECTIONS = 8;
+/** Maximum number of block-relay-only outgoing connections */
+static const int MAX_BLOCKS_ONLY_CONNECTIONS = 2;
 /** -listen default */
 static const bool DEFAULT_LISTEN = true;
 /** -upnp default */
@@ -131,7 +133,8 @@ public:
     {
         ServiceFlags nLocalServices = NODE_NONE;
         int nMaxConnections = 0;
-        int nMaxOutbound = 0;
+        int m_max_outbound_full_relay = 0;
+        int m_max_outbound_block_relay = 0;
         int nMaxAddnode = 0;
         int nMaxFeeler = 0;
         int nBestHeight = 0;
@@ -155,10 +158,12 @@ public:
     void Init(const Options& connOptions) {
         nLocalServices = connOptions.nLocalServices;
         nMaxConnections = connOptions.nMaxConnections;
-        nMaxOutbound = std::min(connOptions.nMaxOutbound, connOptions.nMaxConnections);
+        m_max_outbound_full_relay = std::min(connOptions.m_max_outbound_full_relay, connOptions.nMaxConnections);
+        m_max_outbound_block_relay = connOptions.m_max_outbound_block_relay;
         m_use_addrman_outgoing = connOptions.m_use_addrman_outgoing;
         nMaxAddnode = connOptions.nMaxAddnode;
         nMaxFeeler = connOptions.nMaxFeeler;
+        m_max_outbound = m_max_outbound_full_relay + m_max_outbound_block_relay + nMaxFeeler;
         nBestHeight = connOptions.nBestHeight;
         clientInterface = connOptions.uiInterface;
         m_banman = connOptions.m_banman;
@@ -197,7 +202,7 @@ public:
     bool GetNetworkActive() const { return fNetworkActive; };
     bool GetUseAddrmanOutgoing() const { return m_use_addrman_outgoing; };
     void SetNetworkActive(bool active);
-    void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound = nullptr, const char *strDest = nullptr, bool fOneShot = false, bool fFeeler = false, bool manual_connection = false);
+    void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound = nullptr, const char *strDest = nullptr, bool fOneShot = false, bool fFeeler = false, bool manual_connection = false, bool block_relay_only = false);
     bool CheckIncomingNonce(uint64_t nonce);
 
     bool ForNode(NodeId id, std::function<bool(CNode* pnode)> func);
@@ -253,7 +258,7 @@ public:
     void AddNewAddresses(const std::vector<CAddress>& vAddr, const CAddress& addrFrom, int64_t nTimePenalty = 0);
     std::vector<CAddress> GetAddresses();
 
-    // This allows temporarily exceeding nMaxOutbound, with the goal of finding
+    // This allows temporarily exceeding m_max_outbound_full_relay, with the goal of finding
     // a peer that is better than all our current peers.
     void SetTryNewOutboundPeer(bool flag);
     bool GetTryNewOutboundPeer();
@@ -355,7 +360,7 @@ private:
     CNode* FindNode(const CService& addr);
 
     bool AttemptToEvictConnection();
-    CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection);
+    CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection, bool block_relay_only);
     void AddWhitelistPermissionFlags(NetPermissionFlags& flags, const CNetAddr &addr) const;
 
     void DeleteNode(CNode* pnode);
@@ -414,9 +419,17 @@ private:
     std::unique_ptr<CSemaphore> semOutbound;
     std::unique_ptr<CSemaphore> semAddnode;
     int nMaxConnections;
-    int nMaxOutbound;
+
+    // How many full-relay (tx, block, addr) outbound peers we want
+    int m_max_outbound_full_relay;
+
+    // How many block-relay only outbound peers we want
+    // We do not relay tx or addr messages with these peers
+    int m_max_outbound_block_relay;
+
     int nMaxAddnode;
     int nMaxFeeler;
+    int m_max_outbound;
     bool m_use_addrman_outgoing;
     std::atomic<int> nBestHeight;
     CClientUIInterface* clientInterface;
@@ -442,7 +455,7 @@ private:
     std::thread threadMessageHandler;
 
     /** flag for deciding to connect to an extra outbound peer,
-     *  in excess of nMaxOutbound
+     *  in excess of m_max_outbound_full_relay
      *  This takes the place of a feeler connection */
     std::atomic_bool m_try_another_outbound_peer;
 
@@ -681,15 +694,8 @@ public:
     // Setting fDisconnect to true will cause the node to be disconnected the
     // next time DisconnectNodes() runs
     std::atomic_bool fDisconnect{false};
-    // We use fRelayTxes for two purposes -
-    // a) it allows us to not relay tx invs before receiving the peer's version message
-    // b) the peer may tell us in its version message that we should not relay tx invs
-    //    unless it loads a bloom filter.
-    bool fRelayTxes GUARDED_BY(cs_filter){false};
     bool fSentAddr{false};
     CSemaphoreGrant grantOutbound;
-    mutable CCriticalSection cs_filter;
-    std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter);
     std::atomic<int> nRefCount{0};
 
     const uint64_t nKeyedNetGroup;
@@ -708,28 +714,51 @@ public:
     std::vector<CAddress> vAddrToSend;
     CRollingBloomFilter addrKnown;
     bool fGetAddr{false};
-    std::set<uint256> setKnown;
     int64_t nNextAddrSend GUARDED_BY(cs_sendProcessing){0};
     int64_t nNextLocalAddrSend GUARDED_BY(cs_sendProcessing){0};
 
-    // inventory based relay
-    CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_inventory);
-    // Set of transaction ids we still have to announce.
-    // They are sorted by the mempool before relay, so the order is not important.
-    std::set<uint256> setInventoryTxToSend;
+    const bool m_addr_relay_peer;
+    bool IsAddrRelayPeer() const { return m_addr_relay_peer; }
+
     // List of block ids we still have announce.
     // There is no final sorting before sending, as they are always sent immediately
     // and in the order requested.
     std::vector<uint256> vInventoryBlockToSend GUARDED_BY(cs_inventory);
     CCriticalSection cs_inventory;
-    int64_t nNextInvSend{0};
+
+    struct TxRelay {
+        TxRelay() { pfilter = MakeUnique<CBloomFilter>(); }
+        mutable CCriticalSection cs_filter;
+        // We use fRelayTxes for two purposes -
+        // a) it allows us to not relay tx invs before receiving the peer's version message
+        // b) the peer may tell us in its version message that we should not relay tx invs
+        //    unless it loads a bloom filter.
+        bool fRelayTxes GUARDED_BY(cs_filter){false};
+        std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter) GUARDED_BY(cs_filter);
+
+        mutable CCriticalSection cs_tx_inventory;
+        CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_tx_inventory){50000, 0.000001};
+        // Set of transaction ids we still have to announce.
+        // They are sorted by the mempool before relay, so the order is not important.
+        std::set<uint256> setInventoryTxToSend;
+        // Used for BIP35 mempool sending
+        bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
+        // Last time a "MEMPOOL" request was serviced.
+        std::atomic<int64_t> timeLastMempoolReq{0};
+        int64_t nNextInvSend{0};
+
+        CCriticalSection cs_feeFilter;
+        // Minimum fee rate with which to filter inv's to this node
+        CAmount minFeeFilter GUARDED_BY(cs_feeFilter){0};
+        CAmount lastSentFeeFilter{0};
+        int64_t nextSendTimeFeeFilter{0};
+    };
+
+    // m_tx_relay == nullptr if we're not relaying transactions with this peer
+    std::unique_ptr<TxRelay> m_tx_relay;
+
     // Used for headers announcements - unfiltered blocks to relay
     std::vector<uint256> vBlockHashesToAnnounce GUARDED_BY(cs_inventory);
-    // Used for BIP35 mempool sending
-    bool fSendMempool GUARDED_BY(cs_inventory){false};
-
-    // Last time a "MEMPOOL" request was serviced.
-    std::atomic<int64_t> timeLastMempoolReq{0};
 
     // Block and TXN accept times
     std::atomic<int64_t> nLastBlockTime{0};
@@ -746,15 +775,10 @@ public:
     std::atomic<int64_t> nMinPingUsecTime{std::numeric_limits<int64_t>::max()};
     // Whether a ping is requested.
     std::atomic<bool> fPingQueued{false};
-    // Minimum fee rate with which to filter inv's to this node
-    CAmount minFeeFilter GUARDED_BY(cs_feeFilter){0};
-    CCriticalSection cs_feeFilter;
-    CAmount lastSentFeeFilter{0};
-    int64_t nextSendTimeFeeFilter{0};
 
     std::set<uint256> orphan_work_set;
 
-    CNode(NodeId id, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress &addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress &addrBindIn, const std::string &addrNameIn = "", bool fInboundIn = false);
+    CNode(NodeId id, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress &addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress &addrBindIn, const std::string &addrNameIn = "", bool fInboundIn = false, bool block_relay_only = false);
     ~CNode();
     CNode(const CNode&) = delete;
     CNode& operator=(const CNode&) = delete;
@@ -847,20 +871,21 @@ public:
 
     void AddInventoryKnown(const CInv& inv)
     {
-        {
-            LOCK(cs_inventory);
-            filterInventoryKnown.insert(inv.hash);
+        if (m_tx_relay != nullptr) {
+            LOCK(m_tx_relay->cs_tx_inventory);
+            m_tx_relay->filterInventoryKnown.insert(inv.hash);
         }
     }
 
     void PushInventory(const CInv& inv)
     {
-        LOCK(cs_inventory);
-        if (inv.type == MSG_TX) {
-            if (!filterInventoryKnown.contains(inv.hash)) {
-                setInventoryTxToSend.insert(inv.hash);
+        if (inv.type == MSG_TX && m_tx_relay != nullptr) {
+            LOCK(m_tx_relay->cs_tx_inventory);
+            if (!m_tx_relay->filterInventoryKnown.contains(inv.hash)) {
+                m_tx_relay->setInventoryTxToSend.insert(inv.hash);
             }
         } else if (inv.type == MSG_BLOCK) {
+            LOCK(cs_inventory);
             vInventoryBlockToSend.push_back(inv.hash);
         }
     }
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 520dfcbb66..7f2fea5584 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -262,7 +262,7 @@ struct CNodeState {
     bool fSupportsDesiredCmpctVersion;
 
     /** State used to enforce CHAIN_SYNC_TIMEOUT
-      * Only in effect for outbound, non-manual connections, with
+      * Only in effect for outbound, non-manual, full-relay connections, with
       * m_protect == false
       * Algorithm: if a peer's best known block has less work than our tip,
       * set a timeout CHAIN_SYNC_TIMEOUT seconds in the future:
@@ -425,7 +425,7 @@ static void PushNodeVersion(CNode *pnode, CConnman* connman, int64_t nTime)
     CAddress addrMe = CAddress(CService(), nLocalNodeServices);
 
     connman->PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
-            nonce, strSubVersion, nNodeStartingHeight, ::g_relay_txes));
+            nonce, strSubVersion, nNodeStartingHeight, ::g_relay_txes && pnode->m_tx_relay != nullptr));
 
     if (fLogIPs) {
         LogPrint(BCLog::NET, "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), addrYou.ToString(), nodeid);
@@ -757,7 +757,7 @@ void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds)
 }
 
 // Returns true for outbound peers, excluding manual connections, feelers, and
-// one-shots
+// one-shots.
 static bool IsOutboundDisconnectionCandidate(const CNode *node)
 {
     return !(node->fInbound || node->m_manual_connection || node->fFeeler || node->fOneShot);
@@ -1330,7 +1330,7 @@ static void RelayAddress(const CAddress& addr, bool fReachable, CConnman* connma
     assert(nRelayNodes <= best.size());
 
     auto sortfunc = [&best, &hasher, nRelayNodes](CNode* pnode) {
-        if (pnode->nVersion >= CADDR_TIME_VERSION) {
+        if (pnode->nVersion >= CADDR_TIME_VERSION && pnode->IsAddrRelayPeer()) {
             uint64_t hashKey = CSipHasher(hasher).Write(pnode->GetId()).Finalize();
             for (unsigned int i = 0; i < nRelayNodes; i++) {
                  if (hashKey > best[i].first) {
@@ -1449,11 +1449,11 @@ void static ProcessGetBlockData(CNode* pfrom, const CChainParams& chainparams, c
             {
                 bool sendMerkleBlock = false;
                 CMerkleBlock merkleBlock;
-                {
-                    LOCK(pfrom->cs_filter);
-                    if (pfrom->pfilter) {
+                if (pfrom->m_tx_relay != nullptr) {
+                    LOCK(pfrom->m_tx_relay->cs_filter);
+                    if (pfrom->m_tx_relay->pfilter) {
                         sendMerkleBlock = true;
-                        merkleBlock = CMerkleBlock(*pblock, *pfrom->pfilter);
+                        merkleBlock = CMerkleBlock(*pblock, *pfrom->m_tx_relay->pfilter);
                     }
                 }
                 if (sendMerkleBlock) {
@@ -1513,7 +1513,12 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
     std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
     std::vector<CInv> vNotFound;
     const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
-    {
+
+    // Note that if we receive a getdata for a MSG_TX or MSG_WITNESS_TX from a
+    // block-relay-only outbound peer, we will stop processing further getdata
+    // messages from this peer (likely resulting in our peer eventually
+    // disconnecting us).
+    if (pfrom->m_tx_relay != nullptr) {
         LOCK(cs_main);
 
         while (it != pfrom->vRecvGetData.end() && (it->type == MSG_TX || it->type == MSG_WITNESS_TX)) {
@@ -1533,11 +1538,11 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
             if (mi != mapRelay.end()) {
                 connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                 push = true;
-            } else if (pfrom->timeLastMempoolReq) {
+            } else if (pfrom->m_tx_relay->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) {
+                if (txinfo.tx && txinfo.nTime <= pfrom->m_tx_relay->timeLastMempoolReq) {
                     connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                     push = true;
                 }
@@ -1773,9 +1778,11 @@ bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::ve
             }
         }
 
-        if (!pfrom->fDisconnect && IsOutboundDisconnectionCandidate(pfrom) && nodestate->pindexBestKnownBlock != nullptr) {
-            // If this is an outbound peer, check to see if we should protect
+        if (!pfrom->fDisconnect && IsOutboundDisconnectionCandidate(pfrom) && nodestate->pindexBestKnownBlock != nullptr && pfrom->m_tx_relay != nullptr) {
+            // If this is an outbound full-relay peer, check to see if we should protect
             // it from the bad/lagging chain logic.
+            // Note that block-relay-only peers are already implicitly protected, so we
+            // only consider setting m_protect for the full-relay peers.
             if (g_outbound_peers_with_protect_from_disconnect < MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT && nodestate->pindexBestKnownBlock->nChainWork >= ::ChainActive().Tip()->nChainWork && !nodestate->m_chain_sync.m_protect) {
                 LogPrint(BCLog::NET, "Protecting outbound peer=%d from eviction\n", pfrom->GetId());
                 nodestate->m_chain_sync.m_protect = true;
@@ -1996,9 +2003,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // set nodes not capable of serving the complete blockchain history as "limited nodes"
         pfrom->m_limited_node = (!(nServices & NODE_NETWORK) && (nServices & NODE_NETWORK_LIMITED));
 
-        {
-            LOCK(pfrom->cs_filter);
-            pfrom->fRelayTxes = fRelay; // set to true after we get the first filter* message
+        if (pfrom->m_tx_relay != nullptr) {
+            LOCK(pfrom->m_tx_relay->cs_filter);
+            pfrom->m_tx_relay->fRelayTxes = fRelay; // set to true after we get the first filter* message
         }
 
         // Change version
@@ -2017,7 +2024,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         UpdatePreferredDownload(pfrom, State(pfrom->GetId()));
         }
 
-        if (!pfrom->fInbound)
+        if (!pfrom->fInbound && pfrom->IsAddrRelayPeer())
         {
             // Advertise our address
             if (fListen && !::ChainstateActive().IsInitialBlockDownload())
@@ -2089,9 +2096,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             // Mark this node as currently connected, so we update its timestamp later.
             LOCK(cs_main);
             State(pfrom->GetId())->fCurrentlyConnected = true;
-            LogPrintf("New outbound peer connected: version: %d, blocks=%d, peer=%d%s\n",
-                      pfrom->nVersion.load(), pfrom->nStartingHeight, pfrom->GetId(),
-                      (fLogIPs ? strprintf(", peeraddr=%s", pfrom->addr.ToString()) : ""));
+            LogPrintf("New outbound peer connected: version: %d, blocks=%d, peer=%d%s (%s)\n",
+                      pfrom->nVersion.load(), pfrom->nStartingHeight,
+                      pfrom->GetId(), (fLogIPs ? strprintf(", peeraddr=%s", pfrom->addr.ToString()) : ""),
+                      pfrom->m_tx_relay == nullptr ? "block-relay" : "full-relay");
         }
 
         if (pfrom->nVersion >= SENDHEADERS_VERSION) {
@@ -2132,6 +2140,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // Don't want addr from older versions unless seeding
         if (pfrom->nVersion < CADDR_TIME_VERSION && connman->GetAddressCount() > 1000)
             return true;
+        if (!pfrom->IsAddrRelayPeer()) {
+            return true;
+        }
         if (vAddr.size() > 1000)
         {
             LOCK(cs_main);
@@ -2215,7 +2226,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             return false;
         }
 
-        bool fBlocksOnly = !g_relay_txes;
+        // We won't accept tx inv's if we're in blocks-only mode, or this is a
+        // block-relay-only peer
+        bool fBlocksOnly = !g_relay_txes || (pfrom->m_tx_relay == nullptr);
 
         // Allow whitelisted peers to send data other than blocks in blocks only mode if whitelistrelay is true
         if (pfrom->HasPermission(PF_RELAY))
@@ -2254,7 +2267,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             {
                 pfrom->AddInventoryKnown(inv);
                 if (fBlocksOnly) {
-                    LogPrint(BCLog::NET, "transaction (%s) inv sent in violation of protocol peer=%d\n", inv.hash.ToString(), pfrom->GetId());
+                    LogPrint(BCLog::NET, "transaction (%s) inv sent in violation of protocol, disconnecting peer=%d\n", inv.hash.ToString(), pfrom->GetId());
+                    pfrom->fDisconnect = true;
+                    return true;
                 } else if (!fAlreadyHave && !fImporting && !fReindex && !::ChainstateActive().IsInitialBlockDownload()) {
                     RequestTx(State(pfrom->GetId()), inv.hash, current_time);
                 }
@@ -2471,9 +2486,11 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
     if (strCommand == NetMsgType::TX) {
         // Stop processing the transaction early if
         // We are in blocks only mode and peer is either not whitelisted or whitelistrelay is off
-        if (!g_relay_txes && !pfrom->HasPermission(PF_RELAY))
+        // or if this peer is supposed to be a block-relay-only peer
+        if ((!g_relay_txes && !pfrom->HasPermission(PF_RELAY)) || (pfrom->m_tx_relay == nullptr))
         {
             LogPrint(BCLog::NET, "transaction sent in violation of protocol peer=%d\n", pfrom->GetId());
+            pfrom->fDisconnect = true;
             return true;
         }
 
@@ -2990,6 +3007,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             LogPrint(BCLog::NET, "Ignoring \"getaddr\" from outbound connection. peer=%d\n", pfrom->GetId());
             return true;
         }
+        if (!pfrom->IsAddrRelayPeer()) {
+            LogPrint(BCLog::NET, "Ignoring \"getaddr\" from block-relay-only connection. peer=%d\n", pfrom->GetId());
+            return true;
+        }
 
         // Only send one GetAddr response per connection to reduce resource waste
         //  and discourage addr stamping of INV announcements.
@@ -3031,8 +3052,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             return true;
         }
 
-        LOCK(pfrom->cs_inventory);
-        pfrom->fSendMempool = true;
+        if (pfrom->m_tx_relay != nullptr) {
+            LOCK(pfrom->m_tx_relay->cs_tx_inventory);
+            pfrom->m_tx_relay->fSendMempool = true;
+        }
         return true;
     }
 
@@ -3123,12 +3146,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 100);
         }
-        else
+        else if (pfrom->m_tx_relay != nullptr)
         {
-            LOCK(pfrom->cs_filter);
-            pfrom->pfilter.reset(new CBloomFilter(filter));
-            pfrom->pfilter->UpdateEmptyFull();
-            pfrom->fRelayTxes = true;
+            LOCK(pfrom->m_tx_relay->cs_filter);
+            pfrom->m_tx_relay->pfilter.reset(new CBloomFilter(filter));
+            pfrom->m_tx_relay->pfilter->UpdateEmptyFull();
+            pfrom->m_tx_relay->fRelayTxes = true;
         }
         return true;
     }
@@ -3142,10 +3165,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         bool bad = false;
         if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE) {
             bad = true;
-        } else {
-            LOCK(pfrom->cs_filter);
-            if (pfrom->pfilter) {
-                pfrom->pfilter->insert(vData);
+        } else if (pfrom->m_tx_relay != nullptr) {
+            LOCK(pfrom->m_tx_relay->cs_filter);
+            if (pfrom->m_tx_relay->pfilter) {
+                pfrom->m_tx_relay->pfilter->insert(vData);
             } else {
                 bad = true;
             }
@@ -3158,11 +3181,14 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
     }
 
     if (strCommand == NetMsgType::FILTERCLEAR) {
-        LOCK(pfrom->cs_filter);
+        if (pfrom->m_tx_relay == nullptr) {
+            return true;
+        }
+        LOCK(pfrom->m_tx_relay->cs_filter);
         if (pfrom->GetLocalServices() & NODE_BLOOM) {
-            pfrom->pfilter.reset(new CBloomFilter());
+            pfrom->m_tx_relay->pfilter.reset(new CBloomFilter());
         }
-        pfrom->fRelayTxes = true;
+        pfrom->m_tx_relay->fRelayTxes = true;
         return true;
     }
 
@@ -3170,9 +3196,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         CAmount newFeeFilter = 0;
         vRecv >> newFeeFilter;
         if (MoneyRange(newFeeFilter)) {
-            {
-                LOCK(pfrom->cs_feeFilter);
-                pfrom->minFeeFilter = newFeeFilter;
+            if (pfrom->m_tx_relay != nullptr) {
+                LOCK(pfrom->m_tx_relay->cs_feeFilter);
+                pfrom->m_tx_relay->minFeeFilter = newFeeFilter;
             }
             LogPrint(BCLog::NET, "received: feefilter of %s from peer=%d\n", CFeeRate(newFeeFilter).ToString(), pfrom->GetId());
         }
@@ -3449,6 +3475,8 @@ void PeerLogicValidation::EvictExtraOutboundPeers(int64_t time_in_seconds)
             if (state == nullptr) return; // shouldn't be possible, but just in case
             // Don't evict our protected peers
             if (state->m_chain_sync.m_protect) return;
+            // Don't evict our block-relay-only peers.
+            if (pnode->m_tx_relay == nullptr) return;
             if (state->m_last_block_announcement < oldest_block_announcement || (state->m_last_block_announcement == oldest_block_announcement && pnode->GetId() > worst_peer)) {
                 worst_peer = pnode->GetId();
                 oldest_block_announcement = state->m_last_block_announcement;
@@ -3576,7 +3604,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
 
         // Address refresh broadcast
         int64_t nNow = GetTimeMicros();
-        if (!::ChainstateActive().IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
+        if (pto->IsAddrRelayPeer() && !::ChainstateActive().IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
             AdvertiseLocal(pto);
             pto->nNextLocalAddrSend = PoissonNextSend(nNow, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
         }
@@ -3584,7 +3612,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
         //
         // Message: addr
         //
-        if (pto->nNextAddrSend < nNow) {
+        if (pto->IsAddrRelayPeer() && pto->nNextAddrSend < nNow) {
             pto->nNextAddrSend = PoissonNextSend(nNow, AVG_ADDRESS_BROADCAST_INTERVAL);
             std::vector<CAddress> vAddr;
             vAddr.reserve(pto->vAddrToSend.size());
@@ -3792,120 +3820,123 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
             }
             pto->vInventoryBlockToSend.clear();
 
-            // Check whether periodic sends should happen
-            bool fSendTrickle = pto->HasPermission(PF_NOBAN);
-            if (pto->nNextInvSend < nNow) {
-                fSendTrickle = true;
-                if (pto->fInbound) {
-                    pto->nNextInvSend = connman->PoissonNextSendInbound(nNow, INVENTORY_BROADCAST_INTERVAL);
-                } else {
-                    // Use half the delay for outbound peers, as there is less privacy concern for them.
-                    pto->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> 1);
+            if (pto->m_tx_relay != nullptr) {
+                LOCK(pto->m_tx_relay->cs_tx_inventory);
+                // Check whether periodic sends should happen
+                bool fSendTrickle = pto->HasPermission(PF_NOBAN);
+                if (pto->m_tx_relay->nNextInvSend < nNow) {
+                    fSendTrickle = true;
+                    if (pto->fInbound) {
+                        pto->m_tx_relay->nNextInvSend = connman->PoissonNextSendInbound(nNow, INVENTORY_BROADCAST_INTERVAL);
+                    } else {
+                        // Use half the delay for outbound peers, as there is less privacy concern for them.
+                        pto->m_tx_relay->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> 1);
+                    }
                 }
-            }
-
-            // Time to send but the peer has requested we not relay transactions.
-            if (fSendTrickle) {
-                LOCK(pto->cs_filter);
-                if (!pto->fRelayTxes) pto->setInventoryTxToSend.clear();
-            }
 
-            // Respond to BIP35 mempool requests
-            if (fSendTrickle && pto->fSendMempool) {
-                auto vtxinfo = mempool.infoAll();
-                pto->fSendMempool = false;
-                CAmount filterrate = 0;
-                {
-                    LOCK(pto->cs_feeFilter);
-                    filterrate = pto->minFeeFilter;
+                // Time to send but the peer has requested we not relay transactions.
+                if (fSendTrickle) {
+                    LOCK(pto->m_tx_relay->cs_filter);
+                    if (!pto->m_tx_relay->fRelayTxes) pto->m_tx_relay->setInventoryTxToSend.clear();
                 }
 
-                LOCK(pto->cs_filter);
-
-                for (const auto& txinfo : vtxinfo) {
-                    const uint256& hash = txinfo.tx->GetHash();
-                    CInv inv(MSG_TX, hash);
-                    pto->setInventoryTxToSend.erase(hash);
-                    if (filterrate) {
-                        if (txinfo.feeRate.GetFeePerK() < filterrate)
-                            continue;
-                    }
-                    if (pto->pfilter) {
-                        if (!pto->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
+                // Respond to BIP35 mempool requests
+                if (fSendTrickle && pto->m_tx_relay->fSendMempool) {
+                    auto vtxinfo = mempool.infoAll();
+                    pto->m_tx_relay->fSendMempool = false;
+                    CAmount filterrate = 0;
+                    {
+                        LOCK(pto->m_tx_relay->cs_feeFilter);
+                        filterrate = pto->m_tx_relay->minFeeFilter;
                     }
-                    pto->filterInventoryKnown.insert(hash);
-                    vInv.push_back(inv);
-                    if (vInv.size() == MAX_INV_SZ) {
-                        connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
-                        vInv.clear();
+
+                    LOCK(pto->m_tx_relay->cs_filter);
+
+                    for (const auto& txinfo : vtxinfo) {
+                        const uint256& hash = txinfo.tx->GetHash();
+                        CInv inv(MSG_TX, hash);
+                        pto->m_tx_relay->setInventoryTxToSend.erase(hash);
+                        if (filterrate) {
+                            if (txinfo.feeRate.GetFeePerK() < filterrate)
+                                continue;
+                        }
+                        if (pto->m_tx_relay->pfilter) {
+                            if (!pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
+                        }
+                        pto->m_tx_relay->filterInventoryKnown.insert(hash);
+                        vInv.push_back(inv);
+                        if (vInv.size() == MAX_INV_SZ) {
+                            connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                            vInv.clear();
+                        }
                     }
+                    pto->m_tx_relay->timeLastMempoolReq = GetTime();
                 }
-                pto->timeLastMempoolReq = GetTime();
-            }
 
-            // Determine transactions to relay
-            if (fSendTrickle) {
-                // Produce a vector with all candidates for sending
-                std::vector<std::set<uint256>::iterator> vInvTx;
-                vInvTx.reserve(pto->setInventoryTxToSend.size());
-                for (std::set<uint256>::iterator it = pto->setInventoryTxToSend.begin(); it != pto->setInventoryTxToSend.end(); it++) {
-                    vInvTx.push_back(it);
-                }
-                CAmount filterrate = 0;
-                {
-                    LOCK(pto->cs_feeFilter);
-                    filterrate = pto->minFeeFilter;
-                }
-                // Topologically and fee-rate sort the inventory we send for privacy and priority reasons.
-                // A heap is used so that not all items need sorting if only a few are being sent.
-                CompareInvMempoolOrder compareInvMempoolOrder(&mempool);
-                std::make_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
-                // No reason to drain out at many times the network's capacity,
-                // especially since we have many peers and some will draw much shorter delays.
-                unsigned int nRelayedTransactions = 0;
-                LOCK(pto->cs_filter);
-                while (!vInvTx.empty() && nRelayedTransactions < INVENTORY_BROADCAST_MAX) {
-                    // Fetch the top element from the heap
-                    std::pop_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
-                    std::set<uint256>::iterator it = vInvTx.back();
-                    vInvTx.pop_back();
-                    uint256 hash = *it;
-                    // Remove it from the to-be-sent set
-                    pto->setInventoryTxToSend.erase(it);
-                    // Check if not in the filter already
-                    if (pto->filterInventoryKnown.contains(hash)) {
-                        continue;
+                // Determine transactions to relay
+                if (fSendTrickle) {
+                    // Produce a vector with all candidates for sending
+                    std::vector<std::set<uint256>::iterator> vInvTx;
+                    vInvTx.reserve(pto->m_tx_relay->setInventoryTxToSend.size());
+                    for (std::set<uint256>::iterator it = pto->m_tx_relay->setInventoryTxToSend.begin(); it != pto->m_tx_relay->setInventoryTxToSend.end(); it++) {
+                        vInvTx.push_back(it);
                     }
-                    // Not in the mempool anymore? don't bother sending it.
-                    auto txinfo = mempool.info(hash);
-                    if (!txinfo.tx) {
-                        continue;
-                    }
-                    if (filterrate && txinfo.feeRate.GetFeePerK() < filterrate) {
-                        continue;
-                    }
-                    if (pto->pfilter && !pto->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
-                    // Send
-                    vInv.push_back(CInv(MSG_TX, hash));
-                    nRelayedTransactions++;
+                    CAmount filterrate = 0;
                     {
-                        // Expire old relay messages
-                        while (!vRelayExpiration.empty() && vRelayExpiration.front().first < nNow)
-                        {
-                            mapRelay.erase(vRelayExpiration.front().second);
-                            vRelayExpiration.pop_front();
+                        LOCK(pto->m_tx_relay->cs_feeFilter);
+                        filterrate = pto->m_tx_relay->minFeeFilter;
+                    }
+                    // Topologically and fee-rate sort the inventory we send for privacy and priority reasons.
+                    // A heap is used so that not all items need sorting if only a few are being sent.
+                    CompareInvMempoolOrder compareInvMempoolOrder(&mempool);
+                    std::make_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
+                    // No reason to drain out at many times the network's capacity,
+                    // especially since we have many peers and some will draw much shorter delays.
+                    unsigned int nRelayedTransactions = 0;
+                    LOCK(pto->m_tx_relay->cs_filter);
+                    while (!vInvTx.empty() && nRelayedTransactions < INVENTORY_BROADCAST_MAX) {
+                        // Fetch the top element from the heap
+                        std::pop_heap(vInvTx.begin(), vInvTx.end(), compareInvMempoolOrder);
+                        std::set<uint256>::iterator it = vInvTx.back();
+                        vInvTx.pop_back();
+                        uint256 hash = *it;
+                        // Remove it from the to-be-sent set
+                        pto->m_tx_relay->setInventoryTxToSend.erase(it);
+                        // Check if not in the filter already
+                        if (pto->m_tx_relay->filterInventoryKnown.contains(hash)) {
+                            continue;
                         }
+                        // Not in the mempool anymore? don't bother sending it.
+                        auto txinfo = mempool.info(hash);
+                        if (!txinfo.tx) {
+                            continue;
+                        }
+                        if (filterrate && txinfo.feeRate.GetFeePerK() < filterrate) {
+                            continue;
+                        }
+                        if (pto->m_tx_relay->pfilter && !pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
+                        // Send
+                        vInv.push_back(CInv(MSG_TX, hash));
+                        nRelayedTransactions++;
+                        {
+                            // Expire old relay messages
+                            while (!vRelayExpiration.empty() && vRelayExpiration.front().first < nNow)
+                            {
+                                mapRelay.erase(vRelayExpiration.front().second);
+                                vRelayExpiration.pop_front();
+                            }
 
-                        auto ret = mapRelay.insert(std::make_pair(hash, std::move(txinfo.tx)));
-                        if (ret.second) {
-                            vRelayExpiration.push_back(std::make_pair(nNow + 15 * 60 * 1000000, ret.first));
+                            auto ret = mapRelay.insert(std::make_pair(hash, std::move(txinfo.tx)));
+                            if (ret.second) {
+                                vRelayExpiration.push_back(std::make_pair(nNow + 15 * 60 * 1000000, ret.first));
+                            }
                         }
+                        if (vInv.size() == MAX_INV_SZ) {
+                            connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                            vInv.clear();
+                        }
+                        pto->m_tx_relay->filterInventoryKnown.insert(hash);
                     }
-                    if (vInv.size() == MAX_INV_SZ) {
-                        connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
-                        vInv.clear();
-                    }
-                    pto->filterInventoryKnown.insert(hash);
                 }
             }
         }
@@ -4066,27 +4097,27 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
         // Message: feefilter
         //
         // We don't want white listed peers to filter txs to us if we have -whitelistforcerelay
-        if (pto->nVersion >= FEEFILTER_VERSION && gArgs.GetBoolArg("-feefilter", DEFAULT_FEEFILTER) &&
+        if (pto->m_tx_relay != nullptr && pto->nVersion >= FEEFILTER_VERSION && gArgs.GetBoolArg("-feefilter", DEFAULT_FEEFILTER) &&
             !pto->HasPermission(PF_FORCERELAY)) {
             CAmount currentFilter = mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
             int64_t timeNow = GetTimeMicros();
-            if (timeNow > pto->nextSendTimeFeeFilter) {
+            if (timeNow > pto->m_tx_relay->nextSendTimeFeeFilter) {
                 static CFeeRate default_feerate(DEFAULT_MIN_RELAY_TX_FEE);
                 static FeeFilterRounder filterRounder(default_feerate);
                 CAmount filterToSend = filterRounder.round(currentFilter);
                 // We always have a fee filter of at least minRelayTxFee
                 filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
-                if (filterToSend != pto->lastSentFeeFilter) {
+                if (filterToSend != pto->m_tx_relay->lastSentFeeFilter) {
                     connman->PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
-                    pto->lastSentFeeFilter = filterToSend;
+                    pto->m_tx_relay->lastSentFeeFilter = filterToSend;
                 }
-                pto->nextSendTimeFeeFilter = PoissonNextSend(timeNow, AVG_FEEFILTER_BROADCAST_INTERVAL);
+                pto->m_tx_relay->nextSendTimeFeeFilter = PoissonNextSend(timeNow, AVG_FEEFILTER_BROADCAST_INTERVAL);
             }
             // If the fee filter has changed substantially and it's still more than MAX_FEEFILTER_CHANGE_DELAY
             // until scheduled broadcast, then move the broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
-            else if (timeNow + MAX_FEEFILTER_CHANGE_DELAY * 1000000 < pto->nextSendTimeFeeFilter &&
-                     (currentFilter < 3 * pto->lastSentFeeFilter / 4 || currentFilter > 4 * pto->lastSentFeeFilter / 3)) {
-                pto->nextSendTimeFeeFilter = timeNow + GetRandInt(MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
+            else if (timeNow + MAX_FEEFILTER_CHANGE_DELAY * 1000000 < pto->m_tx_relay->nextSendTimeFeeFilter &&
+                     (currentFilter < 3 * pto->m_tx_relay->lastSentFeeFilter / 4 || currentFilter > 4 * pto->m_tx_relay->lastSentFeeFilter / 3)) {
+                pto->m_tx_relay->nextSendTimeFeeFilter = timeNow + GetRandInt(MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
             }
         }
     }
diff --git a/src/test/denialofservice_tests.cpp b/src/test/denialofservice_tests.cpp
index a50d6854f8..b0a613372f 100644
--- a/src/test/denialofservice_tests.cpp
+++ b/src/test/denialofservice_tests.cpp
@@ -151,17 +151,17 @@ BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
     auto peerLogic = MakeUnique<PeerLogicValidation>(connman.get(), nullptr, scheduler, false);
 
     const Consensus::Params& consensusParams = Params().GetConsensus();
-    constexpr int nMaxOutbound = 8;
+    constexpr int max_outbound_full_relay = 8;
     CConnman::Options options;
     options.nMaxConnections = 125;
-    options.nMaxOutbound = nMaxOutbound;
+    options.m_max_outbound_full_relay = max_outbound_full_relay;
     options.nMaxFeeler = 1;
 
     connman->Init(options);
     std::vector<CNode *> vNodes;
 
     // Mock some outbound peers
-    for (int i=0; i<nMaxOutbound; ++i) {
+    for (int i=0; i<max_outbound_full_relay; ++i) {
         AddRandomOutboundPeer(vNodes, *peerLogic, connman.get());
     }
 
@@ -190,7 +190,7 @@ BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
     AddRandomOutboundPeer(vNodes, *peerLogic, connman.get());
 
     peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
-    for (int i=0; i<nMaxOutbound; ++i) {
+    for (int i=0; i<max_outbound_full_relay; ++i) {
         BOOST_CHECK(vNodes[i]->fDisconnect == false);
     }
     // Last added node should get marked for eviction
@@ -203,10 +203,10 @@ BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
     UpdateLastBlockAnnounceTime(vNodes.back()->GetId(), GetTime());
 
     peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
-    for (int i=0; i<nMaxOutbound-1; ++i) {
+    for (int i=0; i<max_outbound_full_relay-1; ++i) {
         BOOST_CHECK(vNodes[i]->fDisconnect == false);
     }
-    BOOST_CHECK(vNodes[nMaxOutbound-1]->fDisconnect == true);
+    BOOST_CHECK(vNodes[max_outbound_full_relay-1]->fDisconnect == true);
     BOOST_CHECK(vNodes.back()->fDisconnect == false);
 
     bool dummy;