2 files changed, 37 insertions, 8 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index d6ca4fce60..eee66ec582 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1215,6 +1215,19 @@ void CWallet::SyncTransaction(const CTransactionRef& ptx, const CBlockIndex *pin
 void CWallet::TransactionAddedToMempool(const CTransactionRef& ptx) {
     LOCK2(cs_main, cs_wallet);
     SyncTransaction(ptx);
+
+    auto it = mapWallet.find(ptx->GetHash());
+    if (it != mapWallet.end()) {
+        it->second.fInMempool = true;
+    }
+}
+
+void CWallet::TransactionRemovedFromMempool(const CTransactionRef &ptx) {
+    LOCK(cs_wallet);
+    auto it = mapWallet.find(ptx->GetHash());
+    if (it != mapWallet.end()) {
+        it->second.fInMempool = false;
+    }
 }
 
 void CWallet::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex *pindex, const std::vector<CTransactionRef>& vtxConflicted) {
@@ -1229,9 +1242,11 @@ void CWallet::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const
 
     for (const CTransactionRef& ptx : vtxConflicted) {
         SyncTransaction(ptx);
+        TransactionRemovedFromMempool(ptx);
     }
     for (size_t i = 0; i < pblock->vtx.size(); i++) {
         SyncTransaction(pblock->vtx[i], pindex, i);
+        TransactionRemovedFromMempool(pblock->vtx[i]);
     }
 
     m_last_block_processed = pindex;
@@ -1901,8 +1916,7 @@ CAmount CWalletTx::GetChange() const
 
 bool CWalletTx::InMempool() const
 {
-    LOCK(mempool.cs);
-    return mempool.exists(GetHash());
+    return fInMempool;
 }
 
 bool CWalletTx::IsTrusted() const
@@ -3010,14 +3024,18 @@ bool CWallet::CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey, CCon
         // Track how many getdata requests our transaction gets
         mapRequestCount[wtxNew.GetHash()] = 0;
 
+        // Get the inserted-CWalletTx from mapWallet so that the
+        // fInMempool flag is cached properly
+        CWalletTx& wtx = mapWallet[wtxNew.GetHash()];
+
         if (fBroadcastTransactions)
         {
             // Broadcast
-            if (!wtxNew.AcceptToMemoryPool(maxTxFee, state)) {
+            if (!wtx.AcceptToMemoryPool(maxTxFee, state)) {
                 LogPrintf("CommitTransaction(): Transaction cannot be broadcast immediately, %s\n", state.GetRejectReason());
                 // TODO: if we expect the failure to be long term or permanent, instead delete wtx from the wallet and return failure.
             } else {
-                wtxNew.RelayWalletTransaction(connman);
+                wtx.RelayWalletTransaction(connman);
             }
         }
     }
@@ -4091,8 +4109,15 @@ int CMerkleTx::GetBlocksToMaturity() const
 }
 
 
-bool CMerkleTx::AcceptToMemoryPool(const CAmount& nAbsurdFee, CValidationState& state)
+bool CWalletTx::AcceptToMemoryPool(const CAmount& nAbsurdFee, CValidationState& state)
 {
-    return ::AcceptToMemoryPool(mempool, state, tx, nullptr /* pfMissingInputs */,
+    // We must set fInMempool here - while it will be re-set to true by the
+    // entered-mempool callback, if we did not there would be a race where a
+    // user could call sendmoney in a loop and hit spurious out of funds errors
+    // because we think that the transaction they just generated's change is
+    // unavailable as we're not yet aware its in mempool.
+    bool ret = ::AcceptToMemoryPool(mempool, state, tx, nullptr /* pfMissingInputs */,
                                 nullptr /* plTxnReplaced */, false /* bypass_limits */, nAbsurdFee);
+    fInMempool = ret;
+    return ret;
 }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 91029ee462..73da686364 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -252,8 +252,6 @@ public:
     int GetDepthInMainChain() const { const CBlockIndex *pindexRet; return GetDepthInMainChain(pindexRet); }
     bool IsInMainChain() const { const CBlockIndex *pindexRet; return GetDepthInMainChain(pindexRet) > 0; }
     int GetBlocksToMaturity() const;
-    /** Pass this transaction to the mempool. Fails if absolute fee exceeds absurd fee. */
-    bool AcceptToMemoryPool(const CAmount& nAbsurdFee, CValidationState& state);
     bool hashUnset() const { return (hashBlock.IsNull() || hashBlock == ABANDON_HASH); }
     bool isAbandoned() const { return (hashBlock == ABANDON_HASH); }
     void setAbandoned() { hashBlock = ABANDON_HASH; }
@@ -330,6 +328,7 @@ public:
     mutable bool fImmatureWatchCreditCached;
     mutable bool fAvailableWatchCreditCached;
     mutable bool fChangeCached;
+    mutable bool fInMempool;
     mutable CAmount nDebitCached;
     mutable CAmount nCreditCached;
     mutable CAmount nImmatureCreditCached;
@@ -369,6 +368,7 @@ public:
         fImmatureWatchCreditCached = false;
         fAvailableWatchCreditCached = false;
         fChangeCached = false;
+        fInMempool = false;
         nDebitCached = 0;
         nCreditCached = 0;
         nImmatureCreditCached = 0;
@@ -473,6 +473,9 @@ public:
     // RelayWalletTransaction may only be called if fBroadcastTransactions!
     bool RelayWalletTransaction(CConnman* connman);
 
+    /** Pass this transaction to the mempool. Fails if absolute fee exceeds absurd fee. */
+    bool AcceptToMemoryPool(const CAmount& nAbsurdFee, CValidationState& state);
+
     std::set<uint256> GetConflicts() const;
 };
 
@@ -932,6 +935,7 @@ public:
     bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, const CBlockIndex* pIndex, int posInBlock, bool fUpdate);
     int64_t RescanFromTime(int64_t startTime, bool update);
     CBlockIndex* ScanForWalletTransactions(CBlockIndex* pindexStart, CBlockIndex* pindexStop, bool fUpdate = false);
+    void TransactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions();
     void ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman) override;
     // ResendWalletTransactionsBefore may only be called if fBroadcastTransactions!