wallet: track mempool conflicts

Behavior changes are:
- if a tx has a mempool conflict, the wallet will not attempt to
  rebroadcast it
- if a txo is spent by a mempool-conflicted tx, that txo is no
  longer considered spent

3 files changed, 46 insertions, 4 deletions

diff --git a/src/wallet/transaction.h b/src/wallet/transaction.h
index 2ffd85afa9..9c27574103 100644
--- a/src/wallet/transaction.h
+++ b/src/wallet/transaction.h
@@ -48,7 +48,7 @@ struct TxStateBlockConflicted {
     int conflicting_block_height;
 
     explicit TxStateBlockConflicted(const uint256& block_hash, int height) : conflicting_block_hash(block_hash), conflicting_block_height(height) {}
-    std::string toString() const { return strprintf("Conflicted (block=%s, height=%i)", conflicting_block_hash.ToString(), conflicting_block_height); }
+    std::string toString() const { return strprintf("BlockConflicted (block=%s, height=%i)", conflicting_block_hash.ToString(), conflicting_block_height); }
 };
 
 //! State of transaction not confirmed or conflicting with a known block and
@@ -258,6 +258,14 @@ public:
     CTransactionRef tx;
     TxState m_state;
 
+    // Set of mempool transactions that conflict
+    // directly with the transaction, or that conflict
+    // with an ancestor transaction. This set will be
+    // empty if state is InMempool or Confirmed, but
+    // can be nonempty if state is Inactive or
+    // BlockConflicted.
+    std::set<Txid> mempool_conflicts;
+
     template<typename Stream>
     void Serialize(Stream& s) const
     {
@@ -335,9 +343,10 @@ public:
     void updateState(interfaces::Chain& chain);
 
     bool isAbandoned() const { return state<TxStateInactive>() && state<TxStateInactive>()->abandoned; }
+    bool isMempoolConflicted() const { return !mempool_conflicts.empty(); }
     bool isBlockConflicted() const { return state<TxStateBlockConflicted>(); }
     bool isInactive() const { return state<TxStateInactive>(); }
-    bool isUnconfirmed() const { return !isAbandoned() && !isBlockConflicted() && !isConfirmed(); }
+    bool isUnconfirmed() const { return !isAbandoned() && !isBlockConflicted() && !isMempoolConflicted() && !isConfirmed(); }
     bool isConfirmed() const { return state<TxStateConfirmed>(); }
     const Txid& GetHash() const LIFETIMEBOUND { return tx->GetHash(); }
     const Wtxid& GetWitnessHash() const LIFETIMEBOUND { return tx->GetWitnessHash(); }
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 1053b69f32..2adc502642 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -753,7 +753,7 @@ bool CWallet::IsSpent(const COutPoint& outpoint) const
         const auto mit = mapWallet.find(wtxid);
         if (mit != mapWallet.end()) {
             const auto& wtx = mit->second;
-            if (!wtx.isAbandoned() && !wtx.isBlockConflicted())
+            if (!wtx.isAbandoned() && !wtx.isBlockConflicted() && !wtx.isMempoolConflicted())
                 return true; // Spent
         }
     }
@@ -1360,7 +1360,10 @@ void CWallet::MarkConflicted(const uint256& hashBlock, int conflicting_height, c
 void CWallet::RecursiveUpdateTxState(const uint256& tx_hash, const TryUpdatingStateFn& try_updating_state) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) {
     // Do not flush the wallet here for performance reasons
     WalletBatch batch(GetDatabase(), false);
+    RecursiveUpdateTxState(&batch, tx_hash, try_updating_state);
+}
 
+void CWallet::RecursiveUpdateTxState(WalletBatch* batch, const uint256& tx_hash, const TryUpdatingStateFn& try_updating_state) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) {
     std::set<uint256> todo;
     std::set<uint256> done;
 
@@ -1377,7 +1380,7 @@ void CWallet::RecursiveUpdateTxState(const uint256& tx_hash, const TryUpdatingSt
         TxUpdate update_state = try_updating_state(wtx);
         if (update_state != TxUpdate::UNCHANGED) {
             wtx.MarkDirty();
-            batch.WriteTx(wtx);
+            if (batch) batch->WriteTx(wtx);
             // Iterate over all its outputs, and update those tx states as well (if applicable)
             for (unsigned int i = 0; i < wtx.tx->vout.size(); ++i) {
                 std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(COutPoint(Txid::FromUint256(now), i));
@@ -1418,6 +1421,20 @@ void CWallet::transactionAddedToMempool(const CTransactionRef& tx) {
     if (it != mapWallet.end()) {
         RefreshMempoolStatus(it->second, chain());
     }
+
+    const Txid& txid = tx->GetHash();
+
+    for (const CTxIn& tx_in : tx->vin) {
+        // For each wallet transaction spending this prevout..
+        for (auto range = mapTxSpends.equal_range(tx_in.prevout); range.first != range.second; range.first++) {
+            const uint256& spent_id = range.first->second;
+            // Skip the recently added tx
+            if (spent_id == txid) continue;
+            RecursiveUpdateTxState(/*batch=*/nullptr, spent_id, [&txid](CWalletTx& wtx) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) {
+                return wtx.mempool_conflicts.insert(txid).second ? TxUpdate::CHANGED : TxUpdate::UNCHANGED;
+            });
+        }
+    }
 }
 
 void CWallet::transactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason) {
@@ -1455,6 +1472,21 @@ void CWallet::transactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRe
         // https://github.com/bitcoin-core/bitcoin-devwiki/wiki/Wallet-Transaction-Conflict-Tracking
         SyncTransaction(tx, TxStateInactive{});
     }
+
+    const Txid& txid = tx->GetHash();
+
+    for (const CTxIn& tx_in : tx->vin) {
+        // Iterate over all wallet transactions spending txin.prev
+        // and recursively mark them as no longer conflicting with
+        // txid
+        for (auto range = mapTxSpends.equal_range(tx_in.prevout); range.first != range.second; range.first++) {
+            const uint256& spent_id = range.first->second;
+
+            RecursiveUpdateTxState(/*batch=*/nullptr, spent_id, [&txid](CWalletTx& wtx) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) {
+                return wtx.mempool_conflicts.erase(txid) ? TxUpdate::CHANGED : TxUpdate::UNCHANGED;
+            });
+        }
+    }
 }
 
 void CWallet::blockConnected(ChainstateRole role, const interfaces::BlockInfo& block)
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index d55b683f1c..0bc460942c 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -364,6 +364,7 @@ private:
 
     /** Mark a transaction (and its in-wallet descendants) as a particular tx state. */
     void RecursiveUpdateTxState(const uint256& tx_hash, const TryUpdatingStateFn& try_updating_state) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    void RecursiveUpdateTxState(WalletBatch* batch, const uint256& tx_hash, const TryUpdatingStateFn& try_updating_state) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     /** Mark a transaction's inputs dirty, thus forcing the outputs to be recomputed */
     void MarkInputsDirty(const CTransactionRef& tx) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);