Merge #15632: Remove ResendWalletTransactions from the Validation Interface

833d98ae0 [wallet] Remove unnecessary Chain::Lock parameter from ResendWalletTransactions (John Newbery)
52b760fc6 [wallet] Schedule tx rebroadcasts in wallet (John Newbery)
f463cd107 [wallet] Keep track of the best block time in the wallet (John Newbery)

Pull request description:

  Remove the `Broadcast()`/`ResendWalletTransactions()` notification from the Validation interface.

  Closes #15619. See that issue for discussion.

ACKs for commit 833d98:
  ryanofsky:
    utACK 833d98ae073daf0f25f786f043f2ffa85155c8ff. No changes, just rebase.

Tree-SHA512: 7689f2083608ebad8c95ab6692f7842754e1ebe5508bc926a89cad7105cce41007648f37341ba5feb92b30a7aa87acd3abf264a4f1874e35a7161553f6ff3595

9 files changed, 56 insertions, 41 deletions

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index e409ced601..f278e5de95 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -202,17 +202,11 @@ public:
     {
         m_notifications->BlockDisconnected(*block);
     }
-    void ChainStateFlushed(const CBlockLocator& locator) override { m_notifications->ChainStateFlushed(locator); }
-    void ResendWalletTransactions(int64_t best_block_time, CConnman*) override
+    void UpdatedBlockTip(const CBlockIndex* index, const CBlockIndex* fork_index, bool is_ibd) 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);
+        m_notifications->UpdatedBlockTip();
     }
+    void ChainStateFlushed(const CBlockLocator& locator) override { m_notifications->ChainStateFlushed(locator); }
     Chain& m_chain;
     Chain::Notifications* m_notifications;
 };
@@ -347,6 +341,7 @@ public:
     CAmount maxTxFee() override { return ::maxTxFee; }
     bool getPruneMode() override { return ::fPruneMode; }
     bool p2pEnabled() override { return g_connman != nullptr; }
+    bool isReadyToBroadcast() override { return !::fImporting && !::fReindex && !IsInitialBlockDownload(); }
     bool isInitialBlockDownload() override { return IsInitialBlockDownload(); }
     bool shutdownRequested() override { return ShutdownRequested(); }
     int64_t getAdjustedTime() override { return GetAdjustedTime(); }
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index d11a59241e..4e0ef49f6c 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -223,6 +223,9 @@ public:
     //! Check if p2p enabled.
     virtual bool p2pEnabled() = 0;
 
+    //! Check if the node is ready to broadcast transactions.
+    virtual bool isReadyToBroadcast() = 0;
+
     //! Check if in IBD.
     virtual bool isInitialBlockDownload() = 0;
 
@@ -256,8 +259,8 @@ public:
         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 UpdatedBlockTip() {}
         virtual void ChainStateFlushed(const CBlockLocator& locator) {}
-        virtual void ResendWalletTransactions(Lock& locked_chain, int64_t best_block_time) {}
     };
 
     //! Register handler for notifications.
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 0f13d6e269..044fcc90cd 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -175,8 +175,6 @@ namespace {
     /** Expiration-time ordered list of (expire time, relay map entry) pairs. */
     std::deque<std::pair<int64_t, MapRelay::iterator>> vRelayExpiration GUARDED_BY(cs_main);
 
-    std::atomic<int64_t> nTimeBestReceived(0); // Used only to inform the wallet of when we last received a block
-
     struct IteratorComparator
     {
         template<typename I>
@@ -1121,8 +1119,6 @@ void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CB
         });
         connman->WakeMessageHandler();
     }
-
-    nTimeBestReceived = GetTime();
 }
 
 /**
@@ -3550,14 +3546,6 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
             }
         }
 
-        // Resend wallet transactions that haven't gotten in a block yet
-        // Except during reindex, importing and IBD, when old wallet
-        // transactions become unconfirmed and spams other nodes.
-        if (!fReindex && !fImporting && !IsInitialBlockDownload())
-        {
-            GetMainSignals().Broadcast(nTimeBestReceived, connman);
-        }
-
         //
         // Try sending block announcements via headers
         //
diff --git a/src/validationinterface.cpp b/src/validationinterface.cpp
index 70c274d20e..5d0ee1d1fc 100644
--- a/src/validationinterface.cpp
+++ b/src/validationinterface.cpp
@@ -25,7 +25,6 @@ struct ValidationInterfaceConnections {
     boost::signals2::scoped_connection BlockDisconnected;
     boost::signals2::scoped_connection TransactionRemovedFromMempool;
     boost::signals2::scoped_connection ChainStateFlushed;
-    boost::signals2::scoped_connection Broadcast;
     boost::signals2::scoped_connection BlockChecked;
     boost::signals2::scoped_connection NewPoWValidBlock;
 };
@@ -37,7 +36,6 @@ struct MainSignalsInstance {
     boost::signals2::signal<void (const std::shared_ptr<const CBlock> &)> BlockDisconnected;
     boost::signals2::signal<void (const CTransactionRef &)> TransactionRemovedFromMempool;
     boost::signals2::signal<void (const CBlockLocator &)> ChainStateFlushed;
-    boost::signals2::signal<void (int64_t nBestBlockTime, CConnman* connman)> Broadcast;
     boost::signals2::signal<void (const CBlock&, const CValidationState&)> BlockChecked;
     boost::signals2::signal<void (const CBlockIndex *, const std::shared_ptr<const CBlock>&)> NewPoWValidBlock;
 
@@ -101,7 +99,6 @@ void RegisterValidationInterface(CValidationInterface* pwalletIn) {
     conns.BlockDisconnected = g_signals.m_internals->BlockDisconnected.connect(std::bind(&CValidationInterface::BlockDisconnected, pwalletIn, std::placeholders::_1));
     conns.TransactionRemovedFromMempool = g_signals.m_internals->TransactionRemovedFromMempool.connect(std::bind(&CValidationInterface::TransactionRemovedFromMempool, pwalletIn, std::placeholders::_1));
     conns.ChainStateFlushed = g_signals.m_internals->ChainStateFlushed.connect(std::bind(&CValidationInterface::ChainStateFlushed, pwalletIn, std::placeholders::_1));
-    conns.Broadcast = g_signals.m_internals->Broadcast.connect(std::bind(&CValidationInterface::ResendWalletTransactions, pwalletIn, std::placeholders::_1, std::placeholders::_2));
     conns.BlockChecked = g_signals.m_internals->BlockChecked.connect(std::bind(&CValidationInterface::BlockChecked, pwalletIn, std::placeholders::_1, std::placeholders::_2));
     conns.NewPoWValidBlock = g_signals.m_internals->NewPoWValidBlock.connect(std::bind(&CValidationInterface::NewPoWValidBlock, pwalletIn, std::placeholders::_1, std::placeholders::_2));
 }
@@ -175,10 +172,6 @@ void CMainSignals::ChainStateFlushed(const CBlockLocator &locator) {
     });
 }
 
-void CMainSignals::Broadcast(int64_t nBestBlockTime, CConnman* connman) {
-    m_internals->Broadcast(nBestBlockTime, connman);
-}
-
 void CMainSignals::BlockChecked(const CBlock& block, const CValidationState& state) {
     m_internals->BlockChecked(block, state);
 }
diff --git a/src/validationinterface.h b/src/validationinterface.h
index f0374e8e78..78f3026a80 100644
--- a/src/validationinterface.h
+++ b/src/validationinterface.h
@@ -134,8 +134,6 @@ protected:
      * Called on a background thread.
      */
     virtual void ChainStateFlushed(const CBlockLocator &locator) {}
-    /** Tells listeners to broadcast their data. */
-    virtual void ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman) {}
     /**
      * Notifies listeners of a block validation result.
      * If the provided CValidationState IsValid, the provided block
@@ -184,7 +182,6 @@ public:
     void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::shared_ptr<const std::vector<CTransactionRef>> &);
     void BlockDisconnected(const std::shared_ptr<const CBlock> &);
     void ChainStateFlushed(const CBlockLocator &);
-    void Broadcast(int64_t nBestBlockTime, CConnman* connman);
     void BlockChecked(const CBlock&, const CValidationState&);
     void NewPoWValidBlock(const CBlockIndex *, const std::shared_ptr<const CBlock>&);
 };
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 76a7eaa681..a8096dc671 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -211,8 +211,9 @@ void StartWallets(CScheduler& scheduler)
         pwallet->postInitProcess();
     }
 
-    // Run a thread to flush wallet periodically
+    // Schedule periodic wallet flushes and tx rebroadcasts
     scheduler.scheduleEvery(MaybeCompactWalletDB, 500);
+    scheduler.scheduleEvery(MaybeResendWalletTxs, 1000);
 }
 
 void FlushWallets()
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index b62ab0c514..9f89cbefa0 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1276,6 +1276,10 @@ void CWallet::BlockDisconnected(const CBlock& block) {
     }
 }
 
+void CWallet::UpdatedBlockTip()
+{
+    m_best_block_time = GetTime();
+}
 
 
 void CWallet::BlockUntilSyncedToCurrentChain() {
@@ -2110,8 +2114,21 @@ bool CWalletTx::IsEquivalentTo(const CWalletTx& _tx) const
         return CTransaction(tx1) == CTransaction(tx2);
 }
 
-void CWallet::ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, int64_t nBestBlockTime)
+// Rebroadcast transactions from the wallet. We do this on a random timer
+// to slightly obfuscate which transactions come from our wallet.
+//
+// Ideally, we'd only resend transactions that we think should have been
+// mined in the most recent block. Any transaction that wasn't in the top
+// blockweight of transactions in the mempool shouldn't have been mined,
+// and so is probably just sitting in the mempool waiting to be confirmed.
+// Rebroadcasting does nothing to speed up confirmation and only damages
+// privacy.
+void CWallet::ResendWalletTransactions()
 {
+    // During reindex, importing and IBD, old wallet transactions become
+    // unconfirmed. Don't resend them as that would spam other nodes.
+    if (!chain().isReadyToBroadcast()) return;
+
     // Do this infrequently and randomly to avoid giving away
     // that these are our transactions.
     if (GetTime() < nNextResend || !fBroadcastTransactions) return;
@@ -2120,12 +2137,13 @@ void CWallet::ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, in
     if (fFirst) return;
 
     // Only do it if there's been a new block since last time
-    if (nBestBlockTime < nLastResend) return;
+    if (m_best_block_time < nLastResend) return;
     nLastResend = GetTime();
 
     int relayed_tx_count = 0;
 
-    { // cs_wallet scope
+    { // locked_chain and cs_wallet scope
+        auto locked_chain = chain().lock();
         LOCK(cs_wallet);
 
         // Relay transactions
@@ -2133,10 +2151,10 @@ void CWallet::ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, in
             CWalletTx& wtx = item.second;
             // only rebroadcast unconfirmed txes older than 5 minutes before the
             // last block was found
-            if (wtx.nTimeReceived > nBestBlockTime - 5 * 60) continue;
-            relayed_tx_count += wtx.RelayWalletTransaction(locked_chain) ? 1 : 0;
+            if (wtx.nTimeReceived > m_best_block_time - 5 * 60) continue;
+            if (wtx.RelayWalletTransaction(*locked_chain)) ++relayed_tx_count;
         }
-    } // cs_wallet
+    } // locked_chain and cs_wallet
 
     if (relayed_tx_count > 0) {
         WalletLogPrintf("%s: rebroadcast %u unconfirmed transactions\n", __func__, relayed_tx_count);
@@ -2145,7 +2163,12 @@ void CWallet::ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, in
 
 /** @} */ // end of mapWallet
 
-
+void MaybeResendWalletTxs()
+{
+    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
+        pwallet->ResendWalletTransactions();
+    }
+}
 
 
 /** @defgroup Actions
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index fd274fa375..587b2814c0 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -657,6 +657,8 @@ private:
     int64_t nNextResend = 0;
     int64_t nLastResend = 0;
     bool fBroadcastTransactions = false;
+    // Local time that the tip block was received. Used to schedule wallet rebroadcasts.
+    std::atomic<int64_t> m_best_block_time {0};
 
     /**
      * Used to keep track of spent outpoints, and
@@ -926,6 +928,7 @@ public:
     void TransactionAddedToMempool(const CTransactionRef& tx) override;
     void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted) override;
     void BlockDisconnected(const CBlock& block) override;
+    void UpdatedBlockTip() override;
     int64_t RescanFromTime(int64_t startTime, const WalletRescanReserver& reserver, bool update);
 
     struct ScanResult {
@@ -946,7 +949,7 @@ public:
     ScanResult ScanForWalletTransactions(const uint256& first_block, const uint256& last_block, const WalletRescanReserver& reserver, bool fUpdate);
     void TransactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions(interfaces::Chain::Lock& locked_chain) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
-    void ResendWalletTransactions(interfaces::Chain::Lock& locked_chain, int64_t nBestBlockTime) override;
+    void ResendWalletTransactions();
     struct Balance {
         CAmount m_mine_trusted{0};           //!< Trusted, at depth=GetBalance.min_depth or more
         CAmount m_mine_untrusted_pending{0}; //!< Untrusted, but in mempool (pending)
@@ -1229,6 +1232,12 @@ public:
     friend struct WalletTestingSetup;
 };
 
+/**
+ * Called periodically by the schedule thread. Prompts individual wallets to resend
+ * their transactions. Actual rebroadcast schedule is managed by the wallets themselves.
+ */
+void MaybeResendWalletTxs();
+
 /** A key allocated from the key pool. */
 class CReserveKey final : public CReserveScript
 {
diff --git a/test/functional/wallet_resendwallettransactions.py b/test/functional/wallet_resendwallettransactions.py
index 8aafa94c2e..ec5e230e5a 100755
--- a/test/functional/wallet_resendwallettransactions.py
+++ b/test/functional/wallet_resendwallettransactions.py
@@ -39,6 +39,12 @@ class ResendWalletTransactionsTest(BitcoinTestFramework):
         self.log.info("Create a new transaction and wait until it's broadcast")
         txid = int(node.sendtoaddress(node.getnewaddress(), 1), 16)
 
+        # Wallet rebroadcast is first scheduled 1 sec after startup (see
+        # nNextResend in ResendWalletTransactions()). Sleep for just over a
+        # second to be certain that it has been called before the first
+        # setmocktime call below.
+        time.sleep(1.1)
+
         # Can take a few seconds due to transaction trickling
         wait_until(lambda: node.p2p.tx_invs_received[txid] >= 1, lock=mininode_lock)