Merge #16624: wallet: encapsulate transactions state

442a87cc0ae43ebc9b6654a6165778eecb931f74 Add a test wallet_reorgsrestore (Antoine Riard)
40ede992d97df38282919693dfe851c975c3b1d8 Modify wallet tx status if has been reorged out (Antoine Riard)
7e89994133725125dddbfa8d45484e3b9ed51c6e Remove SyncTransaction for conflicted txn in CWallet::BlockConnected (Antoine Riard)
a31be09bfd77eed497a8e251d31358e16e2f2eb1 Encapsulate tx status in a Confirmation struct (Antoine Riard)

Pull request description:

  While working on #15931, I've tried to rationalize tx state management to ease integration of block height tracking per-wallet tx. We currently rely on a combination of `hashBlock` and `nIndex` with magic value to determine tx confirmation, conflicted or abandoned state. It's hard to reason and error-prone.  To solve that, we encapsulate these fields in a `TxConfirmation` struct and introduce a `TxState` member that we update accordingly at block connection/disconnection.

  Following jnewbery [recommendation](https://github.com/bitcoin/bitcoin/pull/15931#discussion_r312576506), I've taken these changes in its own commit, and open a PR to get them first. It would ease review of aforementioned PR, but above all should ease fixing of long-term issues like :
  * https://github.com/bitcoin/bitcoin/issues/7315 (but maybe we should abandon abandontransaction or relieve it to only free outpoints not track the transaction as abandoned in itself, need its own discussion)
  * https://github.com/bitcoin/bitcoin/issues/8692 where we should cancel conflicted state of transactions chain smoothly
  * `MarkConflicted` in `LoadToWallet` is likely useless if we track conflicts rights at block connection

  Main changes of this PR to get right are tx update in `AddToWallet` and serialization/deserialization logic.

ACKs for top commit:
  meshcollider:
    Light re-Code Review ACK 442a87cc0ae43ebc9b6654a6165778eecb931f74
  ryanofsky:
    utACK 442a87cc0ae43ebc9b6654a6165778eecb931f74. Changes since last review are switching from `hasChain` to `LockChain` and removing chain lock in `WalletBatch::LoadWallet` that's redundant with the new lock still added in `CWallet::LoadWallet`, and fixing python test race condition.

Tree-SHA512: 029209e006de0240436817204e69e548c5665e2b0721b214510e7aba7eba130a5eab441d3a1ad95bd6426114dd27390492c77bf4560a9610009b32cd0a1f72f7

5 files changed, 154 insertions, 86 deletions

diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 7707d6233b..f52e4318c8 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -384,8 +384,7 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Something wrong with merkleblock");
     }
 
-    wtx.nIndex = txnIndex;
-    wtx.hashBlock = merkleBlock.header.GetHash();
+    wtx.SetConf(CWalletTx::Status::CONFIRMED, merkleBlock.header.GetHash(), txnIndex);
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 18be3a6ea5..22a5f7e249 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -134,10 +134,10 @@ static void WalletTxToJSON(interfaces::Chain& chain, interfaces::Chain::Lock& lo
         entry.pushKV("generated", true);
     if (confirms > 0)
     {
-        entry.pushKV("blockhash", wtx.hashBlock.GetHex());
-        entry.pushKV("blockindex", wtx.nIndex);
+        entry.pushKV("blockhash", wtx.m_confirm.hashBlock.GetHex());
+        entry.pushKV("blockindex", wtx.m_confirm.nIndex);
         int64_t block_time;
-        bool found_block = chain.findBlock(wtx.hashBlock, nullptr /* block */, &block_time);
+        bool found_block = chain.findBlock(wtx.m_confirm.hashBlock, nullptr /* block */, &block_time);
         assert(found_block);
         entry.pushKV("blocktime", block_time);
     } else {
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 8af05dea45..fc3be2b6ab 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -249,8 +249,7 @@ BOOST_FIXTURE_TEST_CASE(coin_mark_dirty_immature_credit, TestChain100Setup)
     LockAssertion lock(::cs_main);
     LOCK(wallet.cs_wallet);
 
-    wtx.hashBlock = ::ChainActive().Tip()->GetBlockHash();
-    wtx.nIndex = 0;
+    wtx.SetConf(CWalletTx::Status::CONFIRMED, ::ChainActive().Tip()->GetBlockHash(), 0);
 
     // Call GetImmatureCredit() once before adding the key to the wallet to
     // cache the current immature credit amount, which is 0.
@@ -281,14 +280,19 @@ static int64_t AddTx(CWallet& wallet, uint32_t lockTime, int64_t mockTime, int64
     }
 
     CWalletTx wtx(&wallet, MakeTransactionRef(tx));
-    if (block) {
-        wtx.SetMerkleBranch(block->GetBlockHash(), 0);
-    }
-    {
-        LOCK(cs_main);
+    LOCK(cs_main);
+    LOCK(wallet.cs_wallet);
+    // If transaction is already in map, to avoid inconsistencies, unconfirmation
+    // is needed before confirm again with different block.
+    std::map<uint256, CWalletTx>::iterator it = wallet.mapWallet.find(wtx.GetHash());
+    if (it != wallet.mapWallet.end()) {
+        wtx.setUnconfirmed();
         wallet.AddToWallet(wtx);
     }
-    LOCK(wallet.cs_wallet);
+    if (block) {
+        wtx.SetConf(CWalletTx::Status::CONFIRMED, block->GetBlockHash(), 0);
+    }
+    wallet.AddToWallet(wtx);
     return wallet.mapWallet.at(wtx.GetHash()).nTimeSmart;
 }
 
@@ -382,7 +386,7 @@ public:
         LOCK(wallet->cs_wallet);
         auto it = wallet->mapWallet.find(tx->GetHash());
         BOOST_CHECK(it != wallet->mapWallet.end());
-        it->second.SetMerkleBranch(::ChainActive().Tip()->GetBlockHash(), 1);
+        it->second.SetConf(CWalletTx::Status::CONFIRMED, ::ChainActive().Tip()->GetBlockHash(), 1);
         return it->second;
     }
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 84fd01730d..7629a40c5e 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1110,22 +1110,14 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
     bool fUpdated = false;
     if (!fInsertedNew)
     {
-        // Merge
-        if (!wtxIn.hashUnset() && wtxIn.hashBlock != wtx.hashBlock)
-        {
-            wtx.hashBlock = wtxIn.hashBlock;
-            fUpdated = true;
-        }
-        // If no longer abandoned, update
-        if (wtxIn.hashBlock.IsNull() && wtx.isAbandoned())
-        {
-            wtx.hashBlock = wtxIn.hashBlock;
-            fUpdated = true;
-        }
-        if (wtxIn.nIndex != -1 && (wtxIn.nIndex != wtx.nIndex))
-        {
-            wtx.nIndex = wtxIn.nIndex;
+        if (wtxIn.m_confirm.status != wtx.m_confirm.status) {
+            wtx.m_confirm.status = wtxIn.m_confirm.status;
+            wtx.m_confirm.nIndex = wtxIn.m_confirm.nIndex;
+            wtx.m_confirm.hashBlock = wtxIn.m_confirm.hashBlock;
             fUpdated = true;
+        } else {
+            assert(wtx.m_confirm.nIndex == wtxIn.m_confirm.nIndex);
+            assert(wtx.m_confirm.hashBlock == wtxIn.m_confirm.hashBlock);
         }
         if (wtxIn.fFromMe && wtxIn.fFromMe != wtx.fFromMe)
         {
@@ -1172,8 +1164,19 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
     return true;
 }
 
-void CWallet::LoadToWallet(const CWalletTx& wtxIn)
+void CWallet::LoadToWallet(CWalletTx& wtxIn)
 {
+    // If wallet doesn't have a chain (e.g wallet-tool), lock can't be taken.
+    auto locked_chain = LockChain();
+    // If tx hasn't been reorged out of chain while wallet being shutdown
+    // change tx status to UNCONFIRMED and reset hashBlock/nIndex.
+    if (!wtxIn.m_confirm.hashBlock.IsNull()) {
+        if (locked_chain && !locked_chain->getBlockHeight(wtxIn.m_confirm.hashBlock)) {
+            wtxIn.setUnconfirmed();
+            wtxIn.m_confirm.hashBlock = uint256();
+            wtxIn.m_confirm.nIndex = 0;
+        }
+    }
     uint256 hash = wtxIn.GetHash();
     const auto& ins = mapWallet.emplace(hash, wtxIn);
     CWalletTx& wtx = ins.first->second;
@@ -1186,14 +1189,14 @@ void CWallet::LoadToWallet(const CWalletTx& wtxIn)
         auto it = mapWallet.find(txin.prevout.hash);
         if (it != mapWallet.end()) {
             CWalletTx& prevtx = it->second;
-            if (prevtx.nIndex == -1 && !prevtx.hashUnset()) {
-                MarkConflicted(prevtx.hashBlock, wtx.GetHash());
+            if (prevtx.isConflicted()) {
+                MarkConflicted(prevtx.m_confirm.hashBlock, wtx.GetHash());
             }
         }
     }
 }
 
-bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const uint256& block_hash, int posInBlock, bool fUpdate)
+bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, CWalletTx::Status status, const uint256& block_hash, int posInBlock, bool fUpdate)
 {
     const CTransaction& tx = *ptx;
     {
@@ -1240,9 +1243,9 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const uint256
 
             CWalletTx wtx(this, ptx);
 
-            // Get merkle branch if transaction was found in a block
-            if (!block_hash.IsNull())
-                wtx.SetMerkleBranch(block_hash, posInBlock);
+            // Block disconnection override an abandoned tx as unconfirmed
+            // which means user may have to call abandontransaction again
+            wtx.SetConf(status, block_hash, posInBlock);
 
             return AddToWallet(wtx, false);
         }
@@ -1302,7 +1305,7 @@ bool CWallet::AbandonTransaction(interfaces::Chain::Lock& locked_chain, const ui
         if (currentconfirm == 0 && !wtx.isAbandoned()) {
             // If the orig tx was not in block/mempool, none of its spends can be in mempool
             assert(!wtx.InMempool());
-            wtx.nIndex = -1;
+            wtx.m_confirm.nIndex = 0;
             wtx.setAbandoned();
             wtx.MarkDirty();
             batch.WriteTx(wtx);
@@ -1356,8 +1359,9 @@ void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
         if (conflictconfirms < currentconfirm) {
             // Block is 'more conflicted' than current confirm; update.
             // Mark transaction as conflicted with this block.
-            wtx.nIndex = -1;
-            wtx.hashBlock = hashBlock;
+            wtx.m_confirm.nIndex = 0;
+            wtx.m_confirm.hashBlock = hashBlock;
+            wtx.setConflicted();
             wtx.MarkDirty();
             batch.WriteTx(wtx);
             // Iterate over all its outputs, and mark transactions in the wallet that spend them conflicted too
@@ -1375,8 +1379,9 @@ void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
     }
 }
 
-void CWallet::SyncTransaction(const CTransactionRef& ptx, const uint256& block_hash, int posInBlock, bool update_tx) {
-    if (!AddToWalletIfInvolvingMe(ptx, block_hash, posInBlock, update_tx))
+void CWallet::SyncTransaction(const CTransactionRef& ptx, CWalletTx::Status status, const uint256& block_hash, int posInBlock, bool update_tx)
+{
+    if (!AddToWalletIfInvolvingMe(ptx, status, block_hash, posInBlock, update_tx))
         return; // Not one of ours
 
     // If a transaction changes 'conflicted' state, that changes the balance
@@ -1388,7 +1393,7 @@ void CWallet::SyncTransaction(const CTransactionRef& ptx, const uint256& block_h
 void CWallet::TransactionAddedToMempool(const CTransactionRef& ptx) {
     auto locked_chain = chain().lock();
     LOCK(cs_wallet);
-    SyncTransaction(ptx, {} /* block hash */, 0 /* position in block */);
+    SyncTransaction(ptx, CWalletTx::Status::UNCONFIRMED, {} /* block hash */, 0 /* position in block */);
 
     auto it = mapWallet.find(ptx->GetHash());
     if (it != mapWallet.end()) {
@@ -1408,22 +1413,14 @@ void CWallet::BlockConnected(const CBlock& block, const std::vector<CTransaction
     const uint256& block_hash = block.GetHash();
     auto locked_chain = chain().lock();
     LOCK(cs_wallet);
-    // TODO: Temporarily ensure that mempool removals are notified before
-    // connected transactions.  This shouldn't matter, but the abandoned
-    // state of transactions in our wallet is currently cleared when we
-    // receive another notification and there is a race condition where
-    // notification of a connected conflict might cause an outside process
-    // to abandon a transaction and then have it inadvertently cleared by
-    // the notification that the conflicted transaction was evicted.
 
-    for (const CTransactionRef& ptx : vtxConflicted) {
-        SyncTransaction(ptx, {} /* block hash */, 0 /* position in block */);
-        TransactionRemovedFromMempool(ptx);
-    }
     for (size_t i = 0; i < block.vtx.size(); i++) {
-        SyncTransaction(block.vtx[i], block_hash, i);
+        SyncTransaction(block.vtx[i], CWalletTx::Status::CONFIRMED, block_hash, i);
         TransactionRemovedFromMempool(block.vtx[i]);
     }
+    for (const CTransactionRef& ptx : vtxConflicted) {
+        TransactionRemovedFromMempool(ptx);
+    }
 
     m_last_block_processed = block_hash;
 }
@@ -1432,8 +1429,12 @@ void CWallet::BlockDisconnected(const CBlock& block) {
     auto locked_chain = chain().lock();
     LOCK(cs_wallet);
 
+    // At block disconnection, this will change an abandoned transaction to
+    // be unconfirmed, whether or not the transaction is added back to the mempool.
+    // User may have to call abandontransaction again. It may be addressed in the
+    // future with a stickier abandoned state or even removing abandontransaction call.
     for (const CTransactionRef& ptx : block.vtx) {
-        SyncTransaction(ptx, {} /* block hash */, 0 /* position in block */);
+        SyncTransaction(ptx, CWalletTx::Status::UNCONFIRMED, {} /* block hash */, 0 /* position in block */);
     }
 }
 
@@ -2070,7 +2071,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
                 break;
             }
             for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
-                SyncTransaction(block.vtx[posInBlock], block_hash, posInBlock, fUpdate);
+                SyncTransaction(block.vtx[posInBlock], CWalletTx::Status::CONFIRMED, block_hash, posInBlock, fUpdate);
             }
             // scan succeeded, record block as most recent successfully scanned
             result.last_scanned_block = block_hash;
@@ -3332,6 +3333,11 @@ bool CWallet::CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::ve
 
 DBErrors CWallet::LoadWallet(bool& fFirstRunRet)
 {
+    // Even if we don't use this lock in this function, we want to preserve
+    // lock order in LoadToWallet if query of chain state is needed to know
+    // tx status. If lock can't be taken (e.g wallet-tool), tx confirmation
+    // status may be not reliable.
+    auto locked_chain = LockChain();
     LOCK(cs_wallet);
 
     fFirstRunRet = false;
@@ -4042,7 +4048,7 @@ void CWallet::GetKeyBirthTimes(interfaces::Chain::Lock& locked_chain, std::map<C
     for (const auto& entry : mapWallet) {
         // iterate over all wallet transactions...
         const CWalletTx &wtx = entry.second;
-        if (Optional<int> height = locked_chain.getBlockHeight(wtx.hashBlock)) {
+        if (Optional<int> height = locked_chain.getBlockHeight(wtx.m_confirm.hashBlock)) {
             // ... which are already in a block
             for (const CTxOut &txout : wtx.tx->vout) {
                 // iterate over all their outputs
@@ -4085,9 +4091,9 @@ void CWallet::GetKeyBirthTimes(interfaces::Chain::Lock& locked_chain, std::map<C
 unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
 {
     unsigned int nTimeSmart = wtx.nTimeReceived;
-    if (!wtx.hashUnset()) {
+    if (!wtx.isUnconfirmed() && !wtx.isAbandoned()) {
         int64_t blocktime;
-        if (chain().findBlock(wtx.hashBlock, nullptr /* block */, &blocktime)) {
+        if (chain().findBlock(wtx.m_confirm.hashBlock, nullptr /* block */, &blocktime)) {
             int64_t latestNow = wtx.nTimeReceived;
             int64_t latestEntry = 0;
 
@@ -4115,7 +4121,7 @@ unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
 
             nTimeSmart = std::max(latestEntry, std::min(blocktime, latestNow));
         } else {
-            WalletLogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.hashBlock.ToString());
+            WalletLogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.m_confirm.hashBlock.ToString());
         }
     }
     return nTimeSmart;
@@ -4233,6 +4239,11 @@ bool CWallet::Verify(interfaces::Chain& chain, const WalletLocation& location, b
         // Recover readable keypairs:
         CWallet dummyWallet(&chain, WalletLocation(), WalletDatabase::CreateDummy());
         std::string backup_filename;
+        // Even if we don't use this lock in this function, we want to preserve
+        // lock order in LoadToWallet if query of chain state is needed to know
+        // tx status. If lock can't be taken, tx confirmation status may be not
+        // reliable.
+        auto locked_chain = dummyWallet.LockChain();
         if (!WalletBatch::Recover(wallet_path, (void *)&dummyWallet, WalletBatch::RecoverKeysOnlyFilter, backup_filename)) {
             return false;
         }
@@ -4627,21 +4638,23 @@ CKeyPool::CKeyPool(const CPubKey& vchPubKeyIn, bool internalIn)
     m_pre_split = false;
 }
 
-void CWalletTx::SetMerkleBranch(const uint256& block_hash, int posInBlock)
+void CWalletTx::SetConf(Status status, const uint256& block_hash, int posInBlock)
 {
+    // Update tx status
+    m_confirm.status = status;
+
     // Update the tx's hashBlock
-    hashBlock = block_hash;
+    m_confirm.hashBlock = block_hash;
 
     // set the position of the transaction in the block
-    nIndex = posInBlock;
+    m_confirm.nIndex = posInBlock;
 }
 
 int CWalletTx::GetDepthInMainChain(interfaces::Chain::Lock& locked_chain) const
 {
-    if (hashUnset())
-        return 0;
+    if (isUnconfirmed() || isAbandoned()) return 0;
 
-    return locked_chain.getBlockDepth(hashBlock) * (nIndex == -1 ? -1 : 1);
+    return locked_chain.getBlockDepth(m_confirm.hashBlock) * (isConflicted() ? -1 : 1);
 }
 
 int CWalletTx::GetBlocksToMaturity(interfaces::Chain::Lock& locked_chain) const
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 984be3e301..3428e8e001 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -396,7 +396,9 @@ class CWalletTx
 private:
     const CWallet* pwallet;
 
-  /** Constant used in hashBlock to indicate tx has been abandoned */
+    /** Constant used in hashBlock to indicate tx has been abandoned, only used at
+     * serialization/deserialization to avoid ambiguity with conflicted.
+     */
     static const uint256 ABANDON_HASH;
 
 public:
@@ -457,9 +459,7 @@ public:
     mutable CAmount nChangeCached;
 
     CWalletTx(const CWallet* pwalletIn, CTransactionRef arg)
-        : tx(std::move(arg)),
-          hashBlock(uint256()),
-          nIndex(-1)
+        : tx(std::move(arg))
     {
         Init(pwalletIn);
     }
@@ -477,16 +477,37 @@ public:
         fInMempool = false;
         nChangeCached = 0;
         nOrderPos = -1;
+        m_confirm = Confirmation{};
     }
 
     CTransactionRef tx;
-    uint256 hashBlock;
-    /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
-     * block in the chain we know this or any in-wallet dependency conflicts
-     * with. Older clients interpret nIndex == -1 as unconfirmed for backward
-     * compatibility.
+
+    /* New transactions start as UNCONFIRMED. At BlockConnected,
+     * they will transition to CONFIRMED. In case of reorg, at BlockDisconnected,
+     * they roll back to UNCONFIRMED. If we detect a conflicting transaction at
+     * block connection, we update conflicted tx and its dependencies as CONFLICTED.
+     * If tx isn't confirmed and outside of mempool, the user may switch it to ABANDONED
+     * by using the abandontransaction call. This last status may be override by a CONFLICTED
+     * or CONFIRMED transition.
+     */
+    enum Status {
+        UNCONFIRMED,
+        CONFIRMED,
+        CONFLICTED,
+        ABANDONED
+    };
+
+    /* Confirmation includes tx status and a pair of {block hash/tx index in block} at which tx has been confirmed.
+     * This pair is both 0 if tx hasn't confirmed yet. Meaning of these fields changes with CONFLICTED state
+     * where they instead point to block hash and index of the deepest conflicting tx.
      */
-    int nIndex;
+    struct Confirmation {
+        Status status = UNCONFIRMED;
+        uint256 hashBlock = uint256();
+        int nIndex = 0;
+    };
+
+    Confirmation m_confirm;
 
     template<typename Stream>
     void Serialize(Stream& s) const
@@ -502,7 +523,9 @@ public:
         std::vector<char> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<char> dummy_vector2; //!< Used to be vtxPrev
         bool dummy_bool = false; //!< Used to be fSpent
-        s << tx << hashBlock << dummy_vector1 << nIndex << dummy_vector2 << mapValueCopy << vOrderForm << fTimeReceivedIsTxTime << nTimeReceived << fFromMe << dummy_bool;
+        uint256 serializedHash = isAbandoned() ? ABANDON_HASH : m_confirm.hashBlock;
+        int serializedIndex = isAbandoned() || isConflicted() ? -1 : m_confirm.nIndex;
+        s << tx << serializedHash << dummy_vector1 << serializedIndex << dummy_vector2 << mapValueCopy << vOrderForm << fTimeReceivedIsTxTime << nTimeReceived << fFromMe << dummy_bool;
     }
 
     template<typename Stream>
@@ -513,7 +536,25 @@ public:
         std::vector<uint256> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<CMerkleTx> dummy_vector2; //!< Used to be vtxPrev
         bool dummy_bool; //! Used to be fSpent
-        s >> tx >> hashBlock >> dummy_vector1 >> nIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_bool;
+        int serializedIndex;
+        s >> tx >> m_confirm.hashBlock >> dummy_vector1 >> serializedIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_bool;
+
+        /* At serialization/deserialization, an nIndex == -1 means that hashBlock refers to
+         * the earliest block in the chain we know this or any in-wallet ancestor conflicts
+         * with. If nIndex == -1 and hashBlock is ABANDON_HASH, it means transaction is abandoned.
+         * In same context, an nIndex >= 0 refers to a confirmed transaction (if hashBlock set) or
+         * unconfirmed one. Older clients interpret nIndex == -1 as unconfirmed for backward
+         * compatibility (pre-commit 9ac63d6).
+         */
+        if (serializedIndex == -1 && m_confirm.hashBlock == ABANDON_HASH) {
+            m_confirm.hashBlock = uint256();
+            setAbandoned();
+        } else if (serializedIndex == -1) {
+            setConflicted();
+        } else if (!m_confirm.hashBlock.IsNull()) {
+            m_confirm.nIndex = serializedIndex;
+            setConfirmed();
+        }
 
         ReadOrderPos(nOrderPos, mapValue);
         nTimeSmart = mapValue.count("timesmart") ? (unsigned int)atoi64(mapValue["timesmart"]) : 0;
@@ -590,7 +631,7 @@ public:
     // in place.
     std::set<uint256> GetConflicts() const NO_THREAD_SAFETY_ANALYSIS;
 
-    void SetMerkleBranch(const uint256& block_hash, int posInBlock);
+    void SetConf(Status status, const uint256& block_hash, int posInBlock);
 
     /**
      * Return depth of transaction in blockchain:
@@ -607,10 +648,18 @@ public:
      * >0 : is a coinbase transaction which matures in this many blocks
      */
     int GetBlocksToMaturity(interfaces::Chain::Lock& locked_chain) const;
-    bool hashUnset() const { return (hashBlock.IsNull() || hashBlock == ABANDON_HASH); }
-    bool isAbandoned() const { return (hashBlock == ABANDON_HASH); }
-    void setAbandoned() { hashBlock = ABANDON_HASH; }
-
+    bool isAbandoned() const { return m_confirm.status == CWalletTx::ABANDONED; }
+    void setAbandoned()
+    {
+        m_confirm.status = CWalletTx::ABANDONED;
+        m_confirm.hashBlock = uint256();
+        m_confirm.nIndex = 0;
+    }
+    bool isConflicted() const { return m_confirm.status == CWalletTx::CONFLICTED; }
+    void setConflicted() { m_confirm.status = CWalletTx::CONFLICTED; }
+    bool isUnconfirmed() const { return m_confirm.status == CWalletTx::UNCONFIRMED; }
+    void setUnconfirmed() { m_confirm.status = CWalletTx::UNCONFIRMED; }
+    void setConfirmed() { m_confirm.status = CWalletTx::CONFIRMED; }
     const uint256& GetHash() const { return tx->GetHash(); }
     bool IsCoinBase() const { return tx->IsCoinBase(); }
     bool IsImmatureCoinBase(interfaces::Chain::Lock& locked_chain) const;
@@ -750,7 +799,7 @@ private:
      * Abandoned state should probably be more carefully tracked via different
      * posInBlock signals or by checking mempool presence when necessary.
      */
-    bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, const uint256& block_hash, int posInBlock, bool fUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, CWalletTx::Status status, const uint256& block_hash, int posInBlock, bool fUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     /* Mark a transaction (and its in-wallet descendants) as conflicting with a particular block. */
     void MarkConflicted(const uint256& hashBlock, const uint256& hashTx);
@@ -762,7 +811,7 @@ private:
 
     /* Used by TransactionAddedToMemorypool/BlockConnected/Disconnected/ScanForWalletTransactions.
      * Should be called with non-zero block_hash and posInBlock if this is for a transaction that is included in a block. */
-    void SyncTransaction(const CTransactionRef& tx, const uint256& block_hash, int posInBlock = 0, bool update_tx = true) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    void SyncTransaction(const CTransactionRef& tx, CWalletTx::Status status, const uint256& block_hash, int posInBlock = 0, bool update_tx = true) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     /* the HD chain data model (external chain counters) */
     CHDChain hdChain;
@@ -897,6 +946,9 @@ public:
     bool IsLocked() const;
     bool Lock();
 
+    /** Interface to assert chain access and if successful lock it */
+    std::unique_ptr<interfaces::Chain::Lock> LockChain() { return m_chain ? m_chain->lock() : nullptr; }
+
     std::map<uint256, CWalletTx> mapWallet GUARDED_BY(cs_wallet);
 
     typedef std::multimap<int64_t, CWalletTx*> TxItems;
@@ -1042,7 +1094,7 @@ public:
 
     void MarkDirty();
     bool AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose=true);
-    void LoadToWallet(const CWalletTx& wtxIn) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    void LoadToWallet(CWalletTx& wtxIn) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void TransactionAddedToMempool(const CTransactionRef& tx) override;
     void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted) override;
     void BlockDisconnected(const CBlock& block) override;