Merge #10973: Refactor: separate wallet from node

d358466de Remove remaining wallet accesses to node globals (Russell Yanofsky)
b1b2b2389 Remove use of CCoinsViewMemPool::GetCoin in wallet code (Russell Yanofsky)
4e4d9e9f8 Remove use of CRPCTable::appendCommand in wallet code (Russell Yanofsky)
91868e628 Remove use CValidationInterface in wallet code (Russell Yanofsky)

Pull request description:

  This PR is the last in a chain of PRs (#14437, #14711, and #15288) that make the wallet code access node state through an abstract [`Chain`](https://github.com/ryanofsky/bitcoin/blob/pr/wipc-sep/src/interfaces/chain.h) class in [`src/interfaces/`](https://github.com/ryanofsky/bitcoin/tree/pr/wipc-sep/src/interfaces) instead of using global variables like `cs_main`, `chainActive`, and `g_connman`. After this PR, wallet code no longer accesses global variables declared outside the wallet directory, and no longer calls functions accessing those globals (as verified by the `hide-globals` script in #10244).

  This PR and the previous PRs have been refactoring changes that do not affect behavior. Previous PRs have consisted of lots of mechanical changes like:

  ```diff
  -    wtx.nTimeReceived = GetAdjustedTime();
  +    wtx.nTimeReceived = m_chain->getAdjustedTime();
  ```

  This PR is smaller, but less mechanical. It replaces last few bits of wallet code that access node state directly (through `CValidationInterface`, `CRPCTable`, and `CCoinsViewMemPool` interfaces) with code that uses the `Chain` interface.

  These changes allow followup PR #10102 (multiprocess gui & wallet PR) to work without any significant updates to wallet code. Additionally they:

  * Provide a single place to describe the interface between wallet and node code.
  * Can make better wallet testing possible, because the `Chain` object consists of virtual methods that can be overloaded for mocking. (This could be used to test edge cases in the rescan code, for example).

Tree-SHA512: e6291d8a3c50bdff18a9c8ad11e729beb30b5b7040d7aaf31ba678800b4a97b2dd2be76340b1e5c01fe2827d67d37ed1bb4c8380cf8ed653aadfea003e9b22e7

22 files changed, 373 insertions, 137 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index da96a1d96a..aadd402e3c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -154,6 +154,7 @@ BITCOIN_CORE_H = \
   netaddress.h \
   netbase.h \
   netmessagemaker.h \
+  node/coin.h \
   node/transaction.h \
   noui.h \
   optional.h \
@@ -262,6 +263,7 @@ libbitcoin_server_a_SOURCES = \
   miner.cpp \
   net.cpp \
   net_processing.cpp \
+  node/coin.cpp \
   node/transaction.cpp \
   noui.cpp \
   outputtype.cpp \
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 2eecea28d0..0c765f2092 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -6,22 +6,29 @@
 
 #include <chain.h>
 #include <chainparams.h>
+#include <interfaces/handler.h>
 #include <interfaces/wallet.h>
 #include <net.h>
+#include <node/coin.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <protocol.h>
+#include <rpc/protocol.h>
+#include <rpc/server.h>
+#include <shutdown.h>
 #include <sync.h>
 #include <threadsafety.h>
 #include <timedata.h>
 #include <txmempool.h>
 #include <ui_interface.h>
 #include <uint256.h>
+#include <univalue.h>
 #include <util/system.h>
 #include <validation.h>
+#include <validationinterface.h>
 
 #include <memory>
 #include <utility>
@@ -161,6 +168,94 @@ class LockingStateImpl : public LockImpl, public UniqueLock<CCriticalSection>
     using UniqueLock::UniqueLock;
 };
 
+class NotificationsHandlerImpl : public Handler, CValidationInterface
+{
+public:
+    explicit NotificationsHandlerImpl(Chain& chain, Chain::Notifications& notifications)
+        : m_chain(chain), m_notifications(&notifications)
+    {
+        RegisterValidationInterface(this);
+    }
+    ~NotificationsHandlerImpl() override { disconnect(); }
+    void disconnect() override
+    {
+        if (m_notifications) {
+            m_notifications = nullptr;
+            UnregisterValidationInterface(this);
+        }
+    }
+    void TransactionAddedToMempool(const CTransactionRef& tx) override
+    {
+        m_notifications->TransactionAddedToMempool(tx);
+    }
+    void TransactionRemovedFromMempool(const CTransactionRef& tx) override
+    {
+        m_notifications->TransactionRemovedFromMempool(tx);
+    }
+    void BlockConnected(const std::shared_ptr<const CBlock>& block,
+        const CBlockIndex* index,
+        const std::vector<CTransactionRef>& tx_conflicted) override
+    {
+        m_notifications->BlockConnected(*block, tx_conflicted);
+    }
+    void BlockDisconnected(const std::shared_ptr<const CBlock>& block) override
+    {
+        m_notifications->BlockDisconnected(*block);
+    }
+    void ChainStateFlushed(const CBlockLocator& locator) override { m_notifications->ChainStateFlushed(locator); }
+    void ResendWalletTransactions(int64_t best_block_time, CConnman*) override
+    {
+        // `cs_main` is always held when this method is called, so it is safe to
+        // call `assumeLocked`. This is awkward, and the `assumeLocked` method
+        // should be able to be removed entirely if `ResendWalletTransactions`
+        // is replaced by a wallet timer as suggested in
+        // https://github.com/bitcoin/bitcoin/issues/15619
+        auto locked_chain = m_chain.assumeLocked();
+        m_notifications->ResendWalletTransactions(*locked_chain, best_block_time);
+    }
+    Chain& m_chain;
+    Chain::Notifications* m_notifications;
+};
+
+class RpcHandlerImpl : public Handler
+{
+public:
+    RpcHandlerImpl(const CRPCCommand& command) : m_command(command), m_wrapped_command(&command)
+    {
+        m_command.actor = [this](const JSONRPCRequest& request, UniValue& result, bool last_handler) {
+            if (!m_wrapped_command) return false;
+            try {
+                return m_wrapped_command->actor(request, result, last_handler);
+            } catch (const UniValue& e) {
+                // If this is not the last handler and a wallet not found
+                // exception was thrown, return false so the next handler can
+                // try to handle the request. Otherwise, reraise the exception.
+                if (!last_handler) {
+                    const UniValue& code = e["code"];
+                    if (code.isNum() && code.get_int() == RPC_WALLET_NOT_FOUND) {
+                        return false;
+                    }
+                }
+                throw;
+            }
+        };
+        ::tableRPC.appendCommand(m_command.name, &m_command);
+    }
+
+    void disconnect() override final
+    {
+        if (m_wrapped_command) {
+            m_wrapped_command = nullptr;
+            ::tableRPC.removeCommand(m_command.name, &m_command);
+        }
+    }
+
+    ~RpcHandlerImpl() override { disconnect(); }
+
+    CRPCCommand m_command;
+    const CRPCCommand* m_wrapped_command;
+};
+
 class ChainImpl : public Chain
 {
 public:
@@ -194,6 +289,7 @@ public:
         }
         return true;
     }
+    void findCoins(std::map<COutPoint, Coin>& coins) override { return FindCoins(coins); }
     double guessVerificationProgress(const uint256& block_hash) override
     {
         LOCK(cs_main);
@@ -245,17 +341,33 @@ public:
     {
         return ::mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
     }
+    CFeeRate relayMinFee() override { return ::minRelayTxFee; }
+    CFeeRate relayIncrementalFee() override { return ::incrementalRelayFee; }
+    CFeeRate relayDustFee() override { return ::dustRelayFee; }
     CAmount maxTxFee() override { return ::maxTxFee; }
     bool getPruneMode() override { return ::fPruneMode; }
     bool p2pEnabled() override { return g_connman != nullptr; }
     bool isInitialBlockDownload() override { return IsInitialBlockDownload(); }
+    bool shutdownRequested() override { return ShutdownRequested(); }
     int64_t getAdjustedTime() override { return GetAdjustedTime(); }
     void initMessage(const std::string& message) override { ::uiInterface.InitMessage(message); }
     void initWarning(const std::string& message) override { InitWarning(message); }
     void initError(const std::string& message) override { InitError(message); }
     void loadWallet(std::unique_ptr<Wallet> wallet) override { ::uiInterface.LoadWallet(wallet); }
+    void showProgress(const std::string& title, int progress, bool resume_possible) override
+    {
+        ::uiInterface.ShowProgress(title, progress, resume_possible);
+    }
+    std::unique_ptr<Handler> handleNotifications(Notifications& notifications) override
+    {
+        return MakeUnique<NotificationsHandlerImpl>(*this, notifications);
+    }
+    void waitForNotifications() override { SyncWithValidationInterfaceQueue(); }
+    std::unique_ptr<Handler> handleRpc(const CRPCCommand& command) override
+    {
+        return MakeUnique<RpcHandlerImpl>(command);
+    }
 };
-
 } // namespace
 
 std::unique_ptr<Chain> MakeChain() { return MakeUnique<ChainImpl>(); }
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 037e8e9ff5..a9b05f27fc 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -16,8 +16,10 @@
 
 class CBlock;
 class CFeeRate;
+class CRPCCommand;
 class CScheduler;
 class CValidationState;
+class Coin;
 class uint256;
 enum class RBFTransactionState;
 struct CBlockLocator;
@@ -25,6 +27,7 @@ struct FeeCalculation;
 
 namespace interfaces {
 
+class Handler;
 class Wallet;
 
 //! Interface giving clients (wallet processes, maybe other analysis tools in
@@ -40,6 +43,12 @@ class Wallet;
 //!   asynchronously
 //!   (https://github.com/bitcoin/bitcoin/pull/10973#issuecomment-380101269).
 //!
+//! * The isPotentialTip() and waitForNotifications() methods are too low-level
+//!   and should be replaced with a higher level
+//!   waitForNotificationsUpTo(block_hash) method that the wallet can call
+//!   instead
+//!   (https://github.com/bitcoin/bitcoin/pull/10973#discussion_r266995234).
+//!
 //! * The relayTransactions() and submitToMemoryPool() methods could be replaced
 //!   with a higher-level broadcastTransaction method
 //!   (https://github.com/bitcoin/bitcoin/pull/14978#issuecomment-459373984).
@@ -160,6 +169,11 @@ public:
         int64_t* time = nullptr,
         int64_t* max_time = nullptr) = 0;
 
+    //! Look up unspent output information. Returns coins in the mempool and in
+    //! the current chain UTXO set. Iterates through all the keys in the map and
+    //! populates the values.
+    virtual void findCoins(std::map<COutPoint, Coin>& coins) = 0;
+
     //! Estimate fraction of total transactions verified if blocks up to
     //! the specified block hash are verified.
     virtual double guessVerificationProgress(const uint256& block_hash) = 0;
@@ -188,6 +202,15 @@ public:
     //! Mempool minimum fee.
     virtual CFeeRate mempoolMinFee() = 0;
 
+    //! Relay current minimum fee (from -minrelaytxfee and -incrementalrelayfee settings).
+    virtual CFeeRate relayMinFee() = 0;
+
+    //! Relay incremental fee setting (-incrementalrelayfee), reflecting cost of relay.
+    virtual CFeeRate relayIncrementalFee() = 0;
+
+    //! Relay dust fee setting (-dustrelayfee), reflecting lowest rate it's economical to spend.
+    virtual CFeeRate relayDustFee() = 0;
+
     //! Node max tx fee setting (-maxtxfee).
     //! This could be replaced by a per-wallet max fee, as proposed at
     //! https://github.com/bitcoin/bitcoin/issues/15355
@@ -200,9 +223,12 @@ public:
     //! Check if p2p enabled.
     virtual bool p2pEnabled() = 0;
 
-    // Check if in IBD.
+    //! Check if in IBD.
     virtual bool isInitialBlockDownload() = 0;
 
+    //! Check if shutdown requested.
+    virtual bool shutdownRequested() = 0;
+
     //! Get adjusted time.
     virtual int64_t getAdjustedTime() = 0;
 
@@ -217,6 +243,32 @@ public:
 
     //! Send wallet load notification to the GUI.
     virtual void loadWallet(std::unique_ptr<Wallet> wallet) = 0;
+
+    //! Send progress indicator.
+    virtual void showProgress(const std::string& title, int progress, bool resume_possible) = 0;
+
+    //! Chain notifications.
+    class Notifications
+    {
+    public:
+        virtual ~Notifications() {}
+        virtual void TransactionAddedToMempool(const CTransactionRef& tx) {}
+        virtual void TransactionRemovedFromMempool(const CTransactionRef& ptx) {}
+        virtual void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& tx_conflicted) {}
+        virtual void BlockDisconnected(const CBlock& block) {}
+        virtual void ChainStateFlushed(const CBlockLocator& locator) {}
+        virtual void ResendWalletTransactions(Lock& locked_chain, int64_t best_block_time) {}
+    };
+
+    //! Register handler for notifications.
+    virtual std::unique_ptr<Handler> handleNotifications(Notifications& notifications) = 0;
+
+    //! Wait for pending notifications to be handled.
+    virtual void waitForNotifications() = 0;
+
+    //! Register handler for RPC. Command is not copied, so reference
+    //! needs to remain valid until Handler is disconnected.
+    virtual std::unique_ptr<Handler> handleRpc(const CRPCCommand& command) = 0;
 };
 
 //! Interface to let node manage chain clients (wallets, or maybe tools for
diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 7abbee0912..60173b29ac 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -47,8 +47,6 @@ public:
 
     const CTransaction& get() override { return *m_tx; }
 
-    int64_t getVirtualSize() override { return GetVirtualTransactionSize(*m_tx); }
-
     bool commit(WalletValueMap value_map,
         WalletOrderForm order_form,
         std::string& reject_reason) override
@@ -99,12 +97,8 @@ WalletTx MakeWalletTx(interfaces::Chain::Lock& locked_chain, CWallet& wallet, co
 //! Construct wallet tx status struct.
 WalletTxStatus MakeWalletTxStatus(interfaces::Chain::Lock& locked_chain, const CWalletTx& wtx)
 {
-    LockAnnotation lock(::cs_main); // Temporary, for mapBlockIndex below. Removed in upcoming commit.
-
     WalletTxStatus result;
-    auto mi = ::mapBlockIndex.find(wtx.hashBlock);
-    CBlockIndex* block = mi != ::mapBlockIndex.end() ? mi->second : nullptr;
-    result.block_height = (block ? block->nHeight : std::numeric_limits<int>::max());
+    result.block_height = locked_chain.getBlockHeight(wtx.hashBlock).get_value_or(std::numeric_limits<int>::max());
     result.blocks_to_maturity = wtx.GetBlocksToMaturity(locked_chain);
     result.depth_in_main_chain = wtx.GetDepthInMainChain(locked_chain);
     result.time_received = wtx.nTimeReceived;
@@ -514,7 +508,7 @@ public:
         : m_chain(chain), m_wallet_filenames(std::move(wallet_filenames))
     {
     }
-    void registerRpcs() override { return RegisterWalletRPCCommands(::tableRPC); }
+    void registerRpcs() override { return RegisterWalletRPCCommands(m_chain, m_rpc_handlers); }
     bool verify() override { return VerifyWallets(m_chain, m_wallet_filenames); }
     bool load() override { return LoadWallets(m_chain, m_wallet_filenames); }
     void start(CScheduler& scheduler) override { return StartWallets(scheduler); }
@@ -524,6 +518,7 @@ public:
 
     Chain& m_chain;
     std::vector<std::string> m_wallet_filenames;
+    std::vector<std::unique_ptr<Handler>> m_rpc_handlers;
 };
 
 } // namespace
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index a931e5fafb..cabc455b1f 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -292,9 +292,6 @@ public:
     //! Get transaction data.
     virtual const CTransaction& get() = 0;
 
-    //! Get virtual transaction size.
-    virtual int64_t getVirtualSize() = 0;
-
     //! Send pending transaction and commit to wallet.
     virtual bool commit(WalletValueMap value_map,
         WalletOrderForm order_form,
diff --git a/src/node/coin.cpp b/src/node/coin.cpp
new file mode 100644
index 0000000000..bb98e63f3a
--- /dev/null
+++ b/src/node/coin.cpp
@@ -0,0 +1,22 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <node/coin.h>
+
+#include <txmempool.h>
+#include <validation.h>
+
+void FindCoins(std::map<COutPoint, Coin>& coins)
+{
+    LOCK2(cs_main, ::mempool.cs);
+    assert(pcoinsTip);
+    CCoinsViewCache& chain_view = *::pcoinsTip;
+    CCoinsViewMemPool mempool_view(&chain_view, ::mempool);
+    for (auto& coin : coins) {
+        if (!mempool_view.GetCoin(coin.first, coin.second)) {
+            // Either the coin is not in the CCoinsViewCache or is spent. Clear it.
+            coin.second.Clear();
+        }
+    }
+}
diff --git a/src/node/coin.h b/src/node/coin.h
new file mode 100644
index 0000000000..eb95b75cfb
--- /dev/null
+++ b/src/node/coin.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NODE_COIN_H
+#define BITCOIN_NODE_COIN_H
+
+#include <map>
+
+class COutPoint;
+class Coin;
+
+/**
+ * Look up unspent output information. Returns coins in the mempool and in the
+ * current chain UTXO set. Iterates through all the keys in the map and
+ * populates the values.
+ *
+ * @param[in,out] coins map to fill
+ */
+void FindCoins(std::map<COutPoint, Coin>& coins);
+
+#endif // BITCOIN_NODE_COIN_H
diff --git a/src/qt/walletmodeltransaction.cpp b/src/qt/walletmodeltransaction.cpp
index eb3b0baf08..2694d67800 100644
--- a/src/qt/walletmodeltransaction.cpp
+++ b/src/qt/walletmodeltransaction.cpp
@@ -29,7 +29,7 @@ std::unique_ptr<interfaces::PendingWalletTx>& WalletModelTransaction::getWtx()
 
 unsigned int WalletModelTransaction::getTransactionSize()
 {
-    return wtx ? wtx->getVirtualSize() : 0;
+    return wtx ? GetVirtualTransactionSize(wtx->get()) : 0;
 }
 
 CAmount WalletModelTransaction::getTransactionFee() const
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 1d58725a58..0cd1494512 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -11,6 +11,7 @@
 #include <core_io.h>
 #include <index/txindex.h>
 #include <init.h>
+#include <interfaces/chain.h>
 #include <key_io.h>
 #include <keystore.h>
 #include <merkleblock.h>
@@ -791,23 +792,20 @@ static UniValue combinerawtransaction(const JSONRPCRequest& request)
     return EncodeHexTx(CTransaction(mergedTx));
 }
 
+// TODO(https://github.com/bitcoin/bitcoin/pull/10973#discussion_r267084237):
+// This function is called from both wallet and node rpcs
+// (signrawtransactionwithwallet and signrawtransactionwithkey). It should be
+// moved to a util file so wallet code doesn't need to link against node code.
+// Also the dependency on interfaces::Chain should be removed, so
+// signrawtransactionwithkey doesn't need access to a Chain instance.
 UniValue SignTransaction(interfaces::Chain& chain, CMutableTransaction& mtx, const UniValue& prevTxsUnival, CBasicKeyStore *keystore, bool is_temp_keystore, const UniValue& hashType)
 {
     // Fetch previous transactions (inputs):
-    CCoinsView viewDummy;
-    CCoinsViewCache view(&viewDummy);
-    {
-        LOCK2(cs_main, mempool.cs);
-        CCoinsViewCache &viewChain = *pcoinsTip;
-        CCoinsViewMemPool viewMempool(&viewChain, mempool);
-        view.SetBackend(viewMempool); // temporarily switch cache backend to db+mempool view
-
-        for (const CTxIn& txin : mtx.vin) {
-            view.AccessCoin(txin.prevout); // Load entries from viewChain into view; can fail.
-        }
-
-        view.SetBackend(viewDummy); // switch back to avoid locking mempool for too long
+    std::map<COutPoint, Coin> coins;
+    for (const CTxIn& txin : mtx.vin) {
+        coins[txin.prevout]; // Create empty map entry keyed by prevout.
     }
+    chain.findCoins(coins);
 
     // Add previous txouts given in the RPC call:
     if (!prevTxsUnival.isNull()) {
@@ -839,10 +837,10 @@ UniValue SignTransaction(interfaces::Chain& chain, CMutableTransaction& mtx, con
             CScript scriptPubKey(pkData.begin(), pkData.end());
 
             {
-                const Coin& coin = view.AccessCoin(out);
-                if (!coin.IsSpent() && coin.out.scriptPubKey != scriptPubKey) {
+                auto coin = coins.find(out);
+                if (coin != coins.end() && !coin->second.IsSpent() && coin->second.out.scriptPubKey != scriptPubKey) {
                     std::string err("Previous output scriptPubKey mismatch:\n");
-                    err = err + ScriptToAsmStr(coin.out.scriptPubKey) + "\nvs:\n"+
+                    err = err + ScriptToAsmStr(coin->second.out.scriptPubKey) + "\nvs:\n"+
                         ScriptToAsmStr(scriptPubKey);
                     throw JSONRPCError(RPC_DESERIALIZATION_ERROR, err);
                 }
@@ -853,7 +851,7 @@ UniValue SignTransaction(interfaces::Chain& chain, CMutableTransaction& mtx, con
                     newcoin.out.nValue = AmountFromValue(find_value(prevOut, "amount"));
                 }
                 newcoin.nHeight = 1;
-                view.AddCoin(out, std::move(newcoin), true);
+                coins[out] = std::move(newcoin);
             }
 
             // if redeemScript and private keys were given, add redeemScript to the keystore so it can be signed
@@ -897,15 +895,15 @@ UniValue SignTransaction(interfaces::Chain& chain, CMutableTransaction& mtx, con
     // Sign what we can:
     for (unsigned int i = 0; i < mtx.vin.size(); i++) {
         CTxIn& txin = mtx.vin[i];
-        const Coin& coin = view.AccessCoin(txin.prevout);
-        if (coin.IsSpent()) {
+        auto coin = coins.find(txin.prevout);
+        if (coin == coins.end() || coin->second.IsSpent()) {
             TxInErrorToJSON(txin, vErrors, "Input not found or already spent");
             continue;
         }
-        const CScript& prevPubKey = coin.out.scriptPubKey;
-        const CAmount& amount = coin.out.nValue;
+        const CScript& prevPubKey = coin->second.out.scriptPubKey;
+        const CAmount& amount = coin->second.out.nValue;
 
-        SignatureData sigdata = DataFromTransaction(mtx, i, coin.out);
+        SignatureData sigdata = DataFromTransaction(mtx, i, coin->second.out);
         // Only sign SIGHASH_SINGLE if there's a corresponding output:
         if (!fHashSingle || (i < mtx.vout.size())) {
             ProduceSignature(*keystore, MutableTransactionSignatureCreator(&mtx, i, amount, nHashType), prevPubKey, sigdata);
@@ -915,7 +913,7 @@ UniValue SignTransaction(interfaces::Chain& chain, CMutableTransaction& mtx, con
 
         // amount must be specified for valid segwit signature
         if (amount == MAX_MONEY && !txin.scriptWitness.IsNull()) {
-            throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Missing amount for %s", coin.out.ToString()));
+            throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Missing amount for %s", coin->second.out.ToString()));
         }
 
         ScriptError serror = SCRIPT_ERR_OK;
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index cd90573da0..e803fabcc6 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -30,6 +30,7 @@ static std::string rpcWarmupStatus GUARDED_BY(cs_rpcWarmup) = "RPC server starte
 static RPCTimerInterface* timerInterface = nullptr;
 /* Map of name to timer. */
 static std::map<std::string, std::unique_ptr<RPCTimerBase> > deadlineTimers;
+static bool ExecuteCommand(const CRPCCommand& command, const JSONRPCRequest& request, UniValue& result, bool last_handler);
 
 struct RPCCommandExecutionInfo
 {
@@ -173,11 +174,11 @@ std::string CRPCTable::help(const std::string& strCommand, const JSONRPCRequest&
 {
     std::string strRet;
     std::string category;
-    std::set<rpcfn_type> setDone;
+    std::set<intptr_t> setDone;
     std::vector<std::pair<std::string, const CRPCCommand*> > vCommands;
 
     for (const auto& entry : mapCommands)
-        vCommands.push_back(make_pair(entry.second->category + entry.first, entry.second));
+        vCommands.push_back(make_pair(entry.second.front()->category + entry.first, entry.second.front()));
     sort(vCommands.begin(), vCommands.end());
 
     JSONRPCRequest jreq(helpreq);
@@ -193,9 +194,9 @@ std::string CRPCTable::help(const std::string& strCommand, const JSONRPCRequest&
         jreq.strMethod = strMethod;
         try
         {
-            rpcfn_type pfn = pcmd->actor;
-            if (setDone.insert(pfn).second)
-                (*pfn)(jreq);
+            UniValue unused_result;
+            if (setDone.insert(pcmd->unique_id).second)
+                pcmd->actor(jreq, unused_result, true /* last_handler */);
         }
         catch (const std::exception& e)
         {
@@ -337,32 +338,32 @@ CRPCTable::CRPCTable()
         const CRPCCommand *pcmd;
 
         pcmd = &vRPCCommands[vcidx];
-        mapCommands[pcmd->name] = pcmd;
+        mapCommands[pcmd->name].push_back(pcmd);
     }
 }
 
-const CRPCCommand *CRPCTable::operator[](const std::string &name) const
-{
-    std::map<std::string, const CRPCCommand*>::const_iterator it = mapCommands.find(name);
-    if (it == mapCommands.end())
-        return nullptr;
-    return (*it).second;
-}
-
 bool CRPCTable::appendCommand(const std::string& name, const CRPCCommand* pcmd)
 {
     if (IsRPCRunning())
         return false;
 
-    // don't allow overwriting for now
-    std::map<std::string, const CRPCCommand*>::const_iterator it = mapCommands.find(name);
-    if (it != mapCommands.end())
-        return false;
-
-    mapCommands[name] = pcmd;
+    mapCommands[name].push_back(pcmd);
     return true;
 }
 
+bool CRPCTable::removeCommand(const std::string& name, const CRPCCommand* pcmd)
+{
+    auto it = mapCommands.find(name);
+    if (it != mapCommands.end()) {
+        auto new_end = std::remove(it->second.begin(), it->second.end(), pcmd);
+        if (it->second.end() != new_end) {
+            it->second.erase(new_end, it->second.end());
+            return true;
+        }
+    }
+    return false;
+}
+
 void StartRPC()
 {
     LogPrint(BCLog::RPC, "Starting RPC\n");
@@ -543,18 +544,28 @@ UniValue CRPCTable::execute(const JSONRPCRequest &request) const
     }
 
     // Find method
-    const CRPCCommand *pcmd = tableRPC[request.strMethod];
-    if (!pcmd)
-        throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found");
+    auto it = mapCommands.find(request.strMethod);
+    if (it != mapCommands.end()) {
+        UniValue result;
+        for (const auto& command : it->second) {
+            if (ExecuteCommand(*command, request, result, &command == &it->second.back())) {
+                return result;
+            }
+        }
+    }
+    throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found");
+}
 
+static bool ExecuteCommand(const CRPCCommand& command, const JSONRPCRequest& request, UniValue& result, bool last_handler)
+{
     try
     {
         RPCCommandExecution execution(request.strMethod);
         // Execute, convert arguments to array if necessary
         if (request.params.isObject()) {
-            return pcmd->actor(transformNamedArguments(request, pcmd->argNames));
+            return command.actor(transformNamedArguments(request, command.argNames), result, last_handler);
         } else {
-            return pcmd->actor(request);
+            return command.actor(request, result, last_handler);
         }
     }
     catch (const std::exception& e)
diff --git a/src/rpc/server.h b/src/rpc/server.h
index 2d62a76f3c..e2a85887ba 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -131,10 +131,31 @@ typedef UniValue(*rpcfn_type)(const JSONRPCRequest& jsonRequest);
 class CRPCCommand
 {
 public:
+    //! RPC method handler reading request and assigning result. Should return
+    //! true if request is fully handled, false if it should be passed on to
+    //! subsequent handlers.
+    using Actor = std::function<bool(const JSONRPCRequest& request, UniValue& result, bool last_handler)>;
+
+    //! Constructor taking Actor callback supporting multiple handlers.
+    CRPCCommand(std::string category, std::string name, Actor actor, std::vector<std::string> args, intptr_t unique_id)
+        : category(std::move(category)), name(std::move(name)), actor(std::move(actor)), argNames(std::move(args)),
+          unique_id(unique_id)
+    {
+    }
+
+    //! Simplified constructor taking plain rpcfn_type function pointer.
+    CRPCCommand(const char* category, const char* name, rpcfn_type fn, std::initializer_list<const char*> args)
+        : CRPCCommand(category, name,
+                      [fn](const JSONRPCRequest& request, UniValue& result, bool) { result = fn(request); return true; },
+                      {args.begin(), args.end()}, intptr_t(fn))
+    {
+    }
+
     std::string category;
     std::string name;
-    rpcfn_type actor;
+    Actor actor;
     std::vector<std::string> argNames;
+    intptr_t unique_id;
 };
 
 /**
@@ -143,10 +164,9 @@ public:
 class CRPCTable
 {
 private:
-    std::map<std::string, const CRPCCommand*> mapCommands;
+    std::map<std::string, std::vector<const CRPCCommand*>> mapCommands;
 public:
     CRPCTable();
-    const CRPCCommand* operator[](const std::string& name) const;
     std::string help(const std::string& name, const JSONRPCRequest& helpreq) const;
 
     /**
@@ -169,9 +189,7 @@ public:
      *
      * Returns false if RPC server is already running (dump concurrency protection).
      *
-     * Commands cannot be overwritten (returns false).
-     *
-     * Commands with different method names but the same callback function will
+     * Commands with different method names but the same unique_id will
      * be considered aliases, and only the first registered method name will
      * show up in the help text command listing. Aliased commands do not have
      * to have the same behavior. Server and client code can distinguish
@@ -179,6 +197,7 @@ public:
      * register different names, types, and numbers of parameters.
      */
     bool appendCommand(const std::string& name, const CRPCCommand* pcmd);
+    bool removeCommand(const std::string& name, const CRPCCommand* pcmd);
 };
 
 bool IsDeprecatedRPCEnabled(const std::string& method);
diff --git a/src/test/rpc_tests.cpp b/src/test/rpc_tests.cpp
index ff48398925..9bb2bf551b 100644
--- a/src/test/rpc_tests.cpp
+++ b/src/test/rpc_tests.cpp
@@ -31,10 +31,9 @@ UniValue CallRPC(std::string args)
     request.strMethod = strMethod;
     request.params = RPCConvertValues(strMethod, vArgs);
     request.fHelp = false;
-    BOOST_CHECK(tableRPC[strMethod]);
-    rpcfn_type method = tableRPC[strMethod]->actor;
+    if (RPCIsInWarmup(nullptr)) SetRPCWarmupFinished();
     try {
-        UniValue result = (*method)(request);
+        UniValue result = tableRPC.execute(request);
         return result;
     }
     catch (const UniValue& objError) {
diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index a1c3a21d4b..ef7f3be728 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -123,16 +123,17 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
     // The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
     // future proof against changes to network wide policy for incremental relay
     // fee that our node may not be aware of.
+    CFeeRate nodeIncrementalRelayFee = wallet->chain().relayIncrementalFee();
     CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
-    if (::incrementalRelayFee > walletIncrementalRelayFee) {
-        walletIncrementalRelayFee = ::incrementalRelayFee;
+    if (nodeIncrementalRelayFee > walletIncrementalRelayFee) {
+        walletIncrementalRelayFee = nodeIncrementalRelayFee;
     }
 
     if (total_fee > 0) {
-        CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + ::incrementalRelayFee.GetFee(maxNewTxSize);
+        CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + nodeIncrementalRelayFee.GetFee(maxNewTxSize);
         if (total_fee < minTotalFee) {
             errors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
-                                                                FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(::incrementalRelayFee.GetFee(maxNewTxSize))));
+                                                                FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(nodeIncrementalRelayFee.GetFee(maxNewTxSize))));
             return Result::INVALID_PARAMETER;
         }
         CAmount requiredFee = GetRequiredFee(*wallet, maxNewTxSize);
@@ -159,9 +160,10 @@ Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoin
     }
 
     // Check that in all cases the new fee doesn't violate maxTxFee
-     if (new_fee > maxTxFee) {
+     const CAmount max_tx_fee = wallet->chain().maxTxFee();
+     if (new_fee > max_tx_fee) {
          errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
-                               FormatMoney(new_fee), FormatMoney(maxTxFee)));
+                               FormatMoney(new_fee), FormatMoney(max_tx_fee)));
          return Result::WALLET_ERROR;
      }
 
diff --git a/src/wallet/fees.cpp b/src/wallet/fees.cpp
index 545adaebc1..560c86a70a 100644
--- a/src/wallet/fees.cpp
+++ b/src/wallet/fees.cpp
@@ -22,8 +22,9 @@ CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinC
 {
     CAmount fee_needed = GetMinimumFeeRate(wallet, coin_control, feeCalc).GetFee(nTxBytes);
     // Always obey the maximum
-    if (fee_needed > maxTxFee) {
-        fee_needed = maxTxFee;
+    const CAmount max_tx_fee = wallet.chain().maxTxFee();
+    if (fee_needed > max_tx_fee) {
+        fee_needed = max_tx_fee;
         if (feeCalc) feeCalc->reason = FeeReason::MAXTXFEE;
     }
     return fee_needed;
@@ -31,7 +32,7 @@ CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinC
 
 CFeeRate GetRequiredFeeRate(const CWallet& wallet)
 {
-    return std::max(wallet.m_min_fee, ::minRelayTxFee);
+    return std::max(wallet.m_min_fee, wallet.chain().relayMinFee());
 }
 
 CFeeRate GetMinimumFeeRate(const CWallet& wallet, const CCoinControl& coin_control, FeeCalculation* feeCalc)
@@ -96,6 +97,6 @@ CFeeRate GetDiscardRate(const CWallet& wallet)
     // Don't let discard_rate be greater than longest possible fee estimate if we get a valid fee estimate
     discard_rate = (discard_rate == CFeeRate(0)) ? wallet.m_discard_rate : std::min(discard_rate, wallet.m_discard_rate);
     // Discard rate must be at least dustRelayFee
-    discard_rate = std::max(discard_rate, ::dustRelayFee);
+    discard_rate = std::max(discard_rate, wallet.chain().relayDustFee());
     return discard_rate;
 }
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 7ad343c15f..76a7eaa681 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -153,7 +153,7 @@ bool VerifyWallets(interfaces::Chain& chain, const std::vector<std::string>& wal
 
     LogPrintf("Using wallet directory %s\n", GetWalletDir().string());
 
-    uiInterface.InitMessage(_("Verifying wallet(s)..."));
+    chain.initMessage(_("Verifying wallet(s)..."));
 
     // Parameter interaction code should have thrown an error if -salvagewallet
     // was enabled with more than wallet file, so the wallet_files size check
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 684d900478..6c3b5a49dc 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -595,11 +595,11 @@ UniValue importwallet(const JSONRPCRequest& request)
 
         // Use uiInterface.ShowProgress instead of pwallet.ShowProgress because pwallet.ShowProgress has a cancel button tied to AbortRescan which
         // we don't want for this progress bar showing the import progress. uiInterface.ShowProgress does not have a cancel button.
-        uiInterface.ShowProgress(strprintf("%s " + _("Importing..."), pwallet->GetDisplayName()), 0, false); // show progress dialog in GUI
+        pwallet->chain().showProgress(strprintf("%s " + _("Importing..."), pwallet->GetDisplayName()), 0, false); // show progress dialog in GUI
         std::vector<std::tuple<CKey, int64_t, bool, std::string>> keys;
         std::vector<std::pair<CScript, int64_t>> scripts;
         while (file.good()) {
-            uiInterface.ShowProgress("", std::max(1, std::min(50, (int)(((double)file.tellg() / (double)nFilesize) * 100))), false);
+            pwallet->chain().showProgress("", std::max(1, std::min(50, (int)(((double)file.tellg() / (double)nFilesize) * 100))), false);
             std::string line;
             std::getline(file, line);
             if (line.empty() || line[0] == '#')
@@ -637,13 +637,13 @@ UniValue importwallet(const JSONRPCRequest& request)
         file.close();
         // We now know whether we are importing private keys, so we can error if private keys are disabled
         if (keys.size() > 0 && pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
-            uiInterface.ShowProgress("", 100, false); // hide progress dialog in GUI
+            pwallet->chain().showProgress("", 100, false); // hide progress dialog in GUI
             throw JSONRPCError(RPC_WALLET_ERROR, "Importing wallets is disabled when private keys are disabled");
         }
         double total = (double)(keys.size() + scripts.size());
         double progress = 0;
         for (const auto& key_tuple : keys) {
-            uiInterface.ShowProgress("", std::max(50, std::min(75, (int)((progress / total) * 100) + 50)), false);
+            pwallet->chain().showProgress("", std::max(50, std::min(75, (int)((progress / total) * 100) + 50)), false);
             const CKey& key = std::get<0>(key_tuple);
             int64_t time = std::get<1>(key_tuple);
             bool has_label = std::get<2>(key_tuple);
@@ -668,7 +668,7 @@ UniValue importwallet(const JSONRPCRequest& request)
             progress++;
         }
         for (const auto& script_pair : scripts) {
-            uiInterface.ShowProgress("", std::max(50, std::min(75, (int)((progress / total) * 100) + 50)), false);
+            pwallet->chain().showProgress("", std::max(50, std::min(75, (int)((progress / total) * 100) + 50)), false);
             const CScript& script = script_pair.first;
             int64_t time = script_pair.second;
             CScriptID id(script);
@@ -687,10 +687,10 @@ UniValue importwallet(const JSONRPCRequest& request)
             }
             progress++;
         }
-        uiInterface.ShowProgress("", 100, false); // hide progress dialog in GUI
+        pwallet->chain().showProgress("", 100, false); // hide progress dialog in GUI
         pwallet->UpdateTimeFirstKey(nTimeBegin);
     }
-    uiInterface.ShowProgress("", 100, false); // hide progress dialog in GUI
+    pwallet->chain().showProgress("", 100, false); // hide progress dialog in GUI
     RescanWallet(*pwallet, reserver, nTimeBegin, false /* update */);
     pwallet->MarkDirty();
 
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 31a3209a49..fa7604b695 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -2367,8 +2367,8 @@ static UniValue settxfee(const JSONRPCRequest& request)
     CFeeRate tx_fee_rate(nAmount, 1000);
     if (tx_fee_rate == 0) {
         // automatic selection
-    } else if (tx_fee_rate < ::minRelayTxFee) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than min relay tx fee (%s)", ::minRelayTxFee.ToString()));
+    } else if (tx_fee_rate < pwallet->chain().relayMinFee()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than min relay tx fee (%s)", pwallet->chain().relayMinFee().ToString()));
     } else if (tx_fee_rate < pwallet->m_min_fee) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than wallet min fee (%s)", pwallet->m_min_fee.ToString()));
     }
@@ -4156,8 +4156,8 @@ static const CRPCCommand commands[] =
 };
 // clang-format on
 
-void RegisterWalletRPCCommands(CRPCTable &t)
+void RegisterWalletRPCCommands(interfaces::Chain& chain, std::vector<std::unique_ptr<interfaces::Handler>>& handlers)
 {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
-        t.appendCommand(commands[vcidx].name, &commands[vcidx]);
+        handlers.emplace_back(chain.handleRpc(commands[vcidx]));
 }
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index 58053bde59..7cf607ccc7 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -5,7 +5,9 @@
 #ifndef BITCOIN_WALLET_RPCWALLET_H
 #define BITCOIN_WALLET_RPCWALLET_H
 
+#include <memory>
 #include <string>
+#include <vector>
 
 class CRPCTable;
 class CWallet;
@@ -14,7 +16,12 @@ class UniValue;
 struct PartiallySignedTransaction;
 class CTransaction;
 
-void RegisterWalletRPCCommands(CRPCTable &t);
+namespace interfaces {
+class Chain;
+class Handler;
+}
+
+void RegisterWalletRPCCommands(interfaces::Chain& chain, std::vector<std::unique_ptr<interfaces::Handler>>& handlers);
 
 /**
  * Figures out what wallet, if any, to use for a JSONRPCRequest.
diff --git a/src/wallet/test/wallet_test_fixture.cpp b/src/wallet/test/wallet_test_fixture.cpp
index a5fb1db86c..6a051214a9 100644
--- a/src/wallet/test/wallet_test_fixture.cpp
+++ b/src/wallet/test/wallet_test_fixture.cpp
@@ -13,12 +13,7 @@ WalletTestingSetup::WalletTestingSetup(const std::string& chainName):
 {
     bool fFirstRun;
     m_wallet.LoadWallet(fFirstRun);
-    RegisterValidationInterface(&m_wallet);
+    m_wallet.m_chain_notifications_handler = m_chain->handleNotifications(m_wallet);
 
-    RegisterWalletRPCCommands(tableRPC);
-}
-
-WalletTestingSetup::~WalletTestingSetup()
-{
-    UnregisterValidationInterface(&m_wallet);
+    m_chain_client->registerRpcs();
 }
diff --git a/src/wallet/test/wallet_test_fixture.h b/src/wallet/test/wallet_test_fixture.h
index e6fe8c9473..dcfbc55f94 100644
--- a/src/wallet/test/wallet_test_fixture.h
+++ b/src/wallet/test/wallet_test_fixture.h
@@ -17,9 +17,9 @@
  */
 struct WalletTestingSetup: public TestingSetup {
     explicit WalletTestingSetup(const std::string& chainName = CBaseChainParams::MAIN);
-    ~WalletTestingSetup();
 
     std::unique_ptr<interfaces::Chain> m_chain = interfaces::MakeChain();
+    std::unique_ptr<interfaces::ChainClient> m_chain_client = interfaces::MakeWalletClient(*m_chain, {});
     CWallet m_wallet;
 };
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index de686b0ddf..95756f988f 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -96,7 +96,7 @@ static void ReleaseWallet(CWallet* wallet)
     wallet->WalletLogPrintf("Releasing wallet\n");
     wallet->BlockUntilSyncedToCurrentChain();
     wallet->Flush();
-    UnregisterValidationInterface(wallet);
+    wallet->m_chain_notifications_handler.reset();
     delete wallet;
     // Wallet is now released, notify UnloadWallet, if any.
     {
@@ -1243,7 +1243,8 @@ void CWallet::TransactionRemovedFromMempool(const CTransactionRef &ptx) {
     }
 }
 
-void CWallet::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex *pindex, const std::vector<CTransactionRef>& vtxConflicted) {
+void CWallet::BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted) {
+    const uint256& block_hash = block.GetHash();
     auto locked_chain = chain().lock();
     LOCK(cs_wallet);
     // TODO: Temporarily ensure that mempool removals are notified before
@@ -1258,19 +1259,19 @@ void CWallet::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const
         SyncTransaction(ptx, {} /* block hash */, 0 /* position in block */);
         TransactionRemovedFromMempool(ptx);
     }
-    for (size_t i = 0; i < pblock->vtx.size(); i++) {
-        SyncTransaction(pblock->vtx[i], pindex->GetBlockHash(), i);
-        TransactionRemovedFromMempool(pblock->vtx[i]);
+    for (size_t i = 0; i < block.vtx.size(); i++) {
+        SyncTransaction(block.vtx[i], block_hash, i);
+        TransactionRemovedFromMempool(block.vtx[i]);
     }
 
-    m_last_block_processed = pindex->GetBlockHash();
+    m_last_block_processed = block_hash;
 }
 
-void CWallet::BlockDisconnected(const std::shared_ptr<const CBlock>& pblock) {
+void CWallet::BlockDisconnected(const CBlock& block) {
     auto locked_chain = chain().lock();
     LOCK(cs_wallet);
 
-    for (const CTransactionRef& ptx : pblock->vtx) {
+    for (const CTransactionRef& ptx : block.vtx) {
         SyncTransaction(ptx, {} /* block hash */, 0 /* position in block */);
     }
 }
@@ -1297,7 +1298,7 @@ void CWallet::BlockUntilSyncedToCurrentChain() {
     // ...otherwise put a callback in the validation interface queue and wait
     // for the queue to drain enough to execute it (indicating we are caught up
     // at least with the time we entered this function).
-    SyncWithValidationInterfaceQueue();
+    chain().waitForNotifications();
 }
 
 
@@ -1790,7 +1791,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
             progress_end = chain().guessVerificationProgress(stop_block.IsNull() ? tip_hash : stop_block);
         }
         double progress_current = progress_begin;
-        while (block_height && !fAbortRescan && !ShutdownRequested()) {
+        while (block_height && !fAbortRescan && !chain().shutdownRequested()) {
             if (*block_height % 100 == 0 && progress_end - progress_begin > 0.0) {
                 ShowProgress(strprintf("%s " + _("Rescanning..."), GetDisplayName()), std::max(1, std::min(99, (int)((progress_current - progress_begin) / (progress_end - progress_begin) * 100))));
             }
@@ -1852,7 +1853,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
         if (block_height && fAbortRescan) {
             WalletLogPrintf("Rescan aborted at block %d. Progress=%f\n", *block_height, progress_current);
             result.status = ScanResult::USER_ABORT;
-        } else if (block_height && ShutdownRequested()) {
+        } else if (block_height && chain().shutdownRequested()) {
             WalletLogPrintf("Rescan interrupted by shutdown request at block %d. Progress=%f\n", *block_height, progress_current);
             result.status = ScanResult::USER_ABORT;
         }
@@ -2137,7 +2138,7 @@ std::vector<uint256> CWallet::ResendWalletTransactionsBefore(interfaces::Chain::
     return result;
 }
 
-void CWallet::ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman)
+void CWallet::ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, int64_t nBestBlockTime)
 {
     // Do this infrequently and randomly to avoid giving away
     // that these are our transactions.
@@ -2155,8 +2156,7 @@ void CWallet::ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman
 
     // Rebroadcast unconfirmed txes older than 5 minutes before the last
     // block was found:
-    auto locked_chain = chain().assumeLocked();  // Temporary. Removed in upcoming lock cleanup
-    std::vector<uint256> relayed = ResendWalletTransactionsBefore(*locked_chain, nBestBlockTime-5*60);
+    std::vector<uint256> relayed = ResendWalletTransactionsBefore(locked_chain, nBestBlockTime-5*60);
     if (!relayed.empty())
         WalletLogPrintf("%s: rebroadcast %u unconfirmed transactions\n", __func__, relayed.size());
 }
@@ -2310,7 +2310,6 @@ CAmount CWallet::GetAvailableBalance(const CCoinControl* coinControl) const
 
 void CWallet::AvailableCoins(interfaces::Chain::Lock& locked_chain, std::vector<COutput> &vCoins, bool fOnlySafe, const CCoinControl *coinControl, const CAmount &nMinimumAmount, const CAmount &nMaximumAmount, const CAmount &nMinimumSumAmount, const uint64_t nMaximumCount, const int nMinDepth, const int nMaxDepth) const
 {
-    AssertLockHeld(cs_main);
     AssertLockHeld(cs_wallet);
 
     vCoins.clear();
@@ -2420,7 +2419,6 @@ void CWallet::AvailableCoins(interfaces::Chain::Lock& locked_chain, std::vector<
 
 std::map<CTxDestination, std::vector<COutput>> CWallet::ListCoins(interfaces::Chain::Lock& locked_chain) const
 {
-    AssertLockHeld(cs_main);
     AssertLockHeld(cs_wallet);
 
     std::map<CTxDestination, std::vector<COutput>> result;
@@ -2692,13 +2690,13 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nC
     return true;
 }
 
-static bool IsCurrentForAntiFeeSniping(interfaces::Chain::Lock& locked_chain)
+static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, interfaces::Chain::Lock& locked_chain)
 {
-    if (IsInitialBlockDownload()) {
+    if (chain.isInitialBlockDownload()) {
         return false;
     }
     constexpr int64_t MAX_ANTI_FEE_SNIPING_TIP_AGE = 8 * 60 * 60; // in seconds
-    if (chainActive.Tip()->GetBlockTime() < (GetTime() - MAX_ANTI_FEE_SNIPING_TIP_AGE)) {
+    if (locked_chain.getBlockTime(*locked_chain.getHeight()) < (GetTime() - MAX_ANTI_FEE_SNIPING_TIP_AGE)) {
         return false;
     }
     return true;
@@ -2708,7 +2706,7 @@ static bool IsCurrentForAntiFeeSniping(interfaces::Chain::Lock& locked_chain)
  * Return a height-based locktime for new transactions (uses the height of the
  * current chain tip unless we are not synced with the current chain
  */
-static uint32_t GetLocktimeForNewTransaction(interfaces::Chain::Lock& locked_chain)
+static uint32_t GetLocktimeForNewTransaction(interfaces::Chain& chain, interfaces::Chain::Lock& locked_chain)
 {
     uint32_t const height = locked_chain.getHeight().get_value_or(-1);
     uint32_t locktime;
@@ -2732,7 +2730,7 @@ static uint32_t GetLocktimeForNewTransaction(interfaces::Chain::Lock& locked_cha
     // enough, that fee sniping isn't a problem yet, but by implementing a fix
     // now we ensure code won't be written that makes assumptions about
     // nLockTime that preclude a fix later.
-    if (IsCurrentForAntiFeeSniping(locked_chain)) {
+    if (IsCurrentForAntiFeeSniping(chain, locked_chain)) {
         locktime = height;
 
         // Secondly occasionally randomly pick a nLockTime even further back, so
@@ -2806,7 +2804,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
 
     CMutableTransaction txNew;
 
-    txNew.nLockTime = GetLocktimeForNewTransaction(locked_chain);
+    txNew.nLockTime = GetLocktimeForNewTransaction(chain(), locked_chain);
 
     FeeCalculation feeCalc;
     CAmount nFeeNeeded;
@@ -2902,7 +2900,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                     // Include the fee cost for outputs. Note this is only used for BnB right now
                     coin_selection_params.tx_noinputs_size += ::GetSerializeSize(txout, PROTOCOL_VERSION);
 
-                    if (IsDust(txout, ::dustRelayFee))
+                    if (IsDust(txout, chain().relayDustFee()))
                     {
                         if (recipient.fSubtractFeeFromAmount && nFeeRet > 0)
                         {
@@ -3003,7 +3001,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
 
                 // If we made it here and we aren't even able to meet the relay fee on the next pass, give up
                 // because we must be at the maximum allowed fee.
-                if (nFeeNeeded < ::minRelayTxFee.GetFee(nBytes))
+                if (nFeeNeeded < chain().relayMinFee().GetFee(nBytes))
                 {
                     strFailReason = _("Transaction too large for fee policy");
                     return false;
@@ -4280,9 +4278,9 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
                               _("This is the transaction fee you will pay if you send a transaction."));
         }
         walletInstance->m_pay_tx_fee = CFeeRate(nFeePerK, 1000);
-        if (walletInstance->m_pay_tx_fee < ::minRelayTxFee) {
+        if (walletInstance->m_pay_tx_fee < chain.relayMinFee()) {
             chain.initError(strprintf(_("Invalid amount for -paytxfee=<amount>: '%s' (must be at least %s)"),
-                gArgs.GetArg("-paytxfee", ""), ::minRelayTxFee.ToString()));
+                gArgs.GetArg("-paytxfee", ""), chain.relayMinFee().ToString()));
             return nullptr;
         }
     }
@@ -4384,8 +4382,8 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
 
     chain.loadWallet(interfaces::MakeWallet(walletInstance));
 
-    // Register with the validation interface. It's ok to do this after rescan since we're still holding cs_main.
-    RegisterValidationInterface(walletInstance.get());
+    // Register with the validation interface. It's ok to do this after rescan since we're still holding locked_chain.
+    walletInstance->m_chain_notifications_handler = chain.handleNotifications(*walletInstance);
 
     walletInstance->SetBroadcastTransactions(gArgs.GetBoolArg("-walletbroadcast", DEFAULT_WALLETBROADCAST));
 
@@ -4445,8 +4443,6 @@ int CMerkleTx::GetDepthInMainChain(interfaces::Chain::Lock& locked_chain) const
     if (hashUnset())
         return 0;
 
-    AssertLockHeld(cs_main);
-
     return locked_chain.getBlockDepth(hashBlock) * (nIndex == -1 ? -1 : 1);
 }
 
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index ea196c8799..86448efcaf 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -8,6 +8,7 @@
 
 #include <amount.h>
 #include <interfaces/chain.h>
+#include <interfaces/handler.h>
 #include <outputtype.h>
 #include <policy/feerate.h>
 #include <streams.h>
@@ -505,7 +506,7 @@ public:
     CAmount GetCredit(interfaces::Chain::Lock& locked_chain, const isminefilter& filter) const;
     CAmount GetImmatureCredit(interfaces::Chain::Lock& locked_chain, bool fUseCache=true) const;
     // TODO: Remove "NO_THREAD_SAFETY_ANALYSIS" and replace it with the correct
-    // annotation "EXCLUSIVE_LOCKS_REQUIRED(cs_main, pwallet->cs_wallet)". The
+    // annotation "EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet)". The
     // annotation "NO_THREAD_SAFETY_ANALYSIS" was temporarily added to avoid
     // having to resolve the issue of member access into incomplete type CWallet.
     CAmount GetAvailableCredit(interfaces::Chain::Lock& locked_chain, bool fUseCache=true, const isminefilter& filter=ISMINE_SPENDABLE) const NO_THREAD_SAFETY_ANALYSIS;
@@ -637,7 +638,7 @@ class WalletRescanReserver; //forward declarations for ScanForWalletTransactions
  * A CWallet is an extension of a keystore, which also maintains a set of transactions and balances,
  * and provides the ability to create new transactions.
  */
-class CWallet final : public CCryptoKeyStore, public CValidationInterface
+class CWallet final : public CCryptoKeyStore, private interfaces::Chain::Notifications
 {
 private:
     std::atomic<bool> fAbortRescan{false};
@@ -808,6 +809,9 @@ public:
 
     std::set<COutPoint> setLockedCoins GUARDED_BY(cs_wallet);
 
+    /** Registered interfaces::Chain::Notifications handler. */
+    std::unique_ptr<interfaces::Handler> m_chain_notifications_handler;
+
     /** Interface for accessing chain state. */
     interfaces::Chain& chain() const { return m_chain; }
 
@@ -920,8 +924,8 @@ public:
     bool AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose=true);
     void LoadToWallet(const CWalletTx& wtxIn) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void TransactionAddedToMempool(const CTransactionRef& tx) override;
-    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex *pindex, const std::vector<CTransactionRef>& vtxConflicted) override;
-    void BlockDisconnected(const std::shared_ptr<const CBlock>& pblock) override;
+    void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted) override;
+    void BlockDisconnected(const CBlock& block) override;
     int64_t RescanFromTime(int64_t startTime, const WalletRescanReserver& reserver, bool update);
 
     struct ScanResult {
@@ -942,7 +946,7 @@ public:
     ScanResult ScanForWalletTransactions(const uint256& first_block, const uint256& last_block, const WalletRescanReserver& reserver, bool fUpdate);
     void TransactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions();
-    void ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman) override EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    void ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, int64_t nBestBlockTime) override;
     // ResendWalletTransactionsBefore may only be called if fBroadcastTransactions!
     std::vector<uint256> ResendWalletTransactionsBefore(interfaces::Chain::Lock& locked_chain, int64_t nTime);
     CAmount GetBalance(const isminefilter& filter=ISMINE_SPENDABLE, const int min_depth=0) const;
@@ -1220,6 +1224,8 @@ public:
 
     /** Add a KeyOriginInfo to the wallet */
     bool AddKeyOrigin(const CPubKey& pubkey, const KeyOriginInfo& info);
+
+    friend struct WalletTestingSetup;
 };
 
 /** A key allocated from the key pool. */