Merge #20536: wallet: Error with "Transaction too large" if the funded tx will end up being too large after signing

48a0319 Add a test that selects too large if BnB is used (Andrew Chow)
3e69939 Fail if maximum weight is too large (Andrew Chow)
51e2cd3 Have CalculateMaximumSignedTxSize also compute tx weight (Andrew Chow)

Pull request description:

  Currently the `Transaction too large` is calculated on the transaction that is returned from `CreateTransaction`. This does not make sense for when `CreateTransaction` is being used for `fundrawtransaction` as no signing occurs so the final returned transaction is missing signatures. Thus users may successfully fund a transaction but fail to broadcast it after it has been fully signed.

  So instead we should figure out whether the transaction we are funding will be too large after it is signed. We can do this by having `CalculateMaximumSignedTxSize` also return the transaction weight and then comparing that weight against the maximum weight.

ACKs for top commit:
  instagibbs:
    ACK bitcoin/bitcoin@48a0319
  meshcollider:
    utACK 48a0319
  Xekyo:
    utACK with nits 48a0319

Tree-SHA512: 1700c60b07f67e2d5c591c5ccd131ac9f1861fab3def961c3c9c4b3281ec1063fe8e4f0f7f1038cac72692340856406bcee8fb45c8104d2ad34357a0ec878ac7

Author: meshcollider

src/wallet/feebumper.cpp

@@ -190,7 +190,7 @@ Result CreateRateBumpTransaction(CWallet& wallet, const uint256& txid, const CCo
     if (coin_control.m_feerate) {
         // The user provided a feeRate argument.
         // We calculate this here to avoid compiler warning on the cs_wallet lock
-        const int64_t maxTxSize = CalculateMaximumSignedTxSize(*wtx.tx, &wallet);
+        const int64_t maxTxSize = CalculateMaximumSignedTxSize(*wtx.tx, &wallet).first;
         Result res = CheckFeeRate(wallet, wtx, *new_coin_control.m_feerate, maxTxSize, errors);
         if (res != Result::OK) {
             return res;

src/wallet/wallet.cpp

@@ -1611,14 +1611,15 @@ bool CWallet::ImportScriptPubKeys(const std::string& label, const std::set<CScri
     return true;
 }
 
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig)
+// Returns pair of vsize and weight
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig)
 {
     std::vector<CTxOut> txouts;
     for (const CTxIn& input : tx.vin) {
         const auto mi = wallet->mapWallet.find(input.prevout.hash);
         // Can not estimate size without knowing the input details
         if (mi == wallet->mapWallet.end()) {
-            return -1;
+            return std::make_pair(-1, -1);
         }
         assert(input.prevout.n < mi->second.tx->vout.size());
         txouts.emplace_back(mi->second.tx->vout[input.prevout.n]);
@@ -1627,13 +1628,16 @@ int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wall
 }
 
 // txouts needs to be in the order of tx.vin
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig)
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig)
 {
     CMutableTransaction txNew(tx);
     if (!wallet->DummySignTx(txNew, txouts, use_max_sig)) {
-        return -1;
+        return std::make_pair(-1, -1);
     }
-    return GetVirtualTransactionSize(CTransaction(txNew));
+    CTransaction ctx(txNew);
+    int64_t vsize = GetVirtualTransactionSize(ctx);
+    int64_t weight = GetTransactionWeight(ctx);
+    return std::make_pair(vsize, weight);
 }
 
 int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* wallet, bool use_max_sig)
@@ -2779,6 +2783,7 @@ bool CWallet::CreateTransactionInternal(
     CMutableTransaction txNew;
     FeeCalculation feeCalc;
     CAmount nFeeNeeded;
+    std::pair<int64_t, int64_t> tx_sizes;
     int nBytes;
     {
         std::set<CInputCoin> setCoins;
@@ -2962,7 +2967,8 @@ bool CWallet::CreateTransactionInternal(
                     txNew.vin.push_back(CTxIn(coin.outpoint,CScript()));
                 }
 
-                nBytes = CalculateMaximumSignedTxSize(CTransaction(txNew), this, coin_control.fAllowWatchOnly);
+                tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), this, coin_control.fAllowWatchOnly);
+                nBytes = tx_sizes.first;
                 if (nBytes < 0) {
                     error = _("Signing transaction failed");
                     return false;
@@ -3072,7 +3078,8 @@ bool CWallet::CreateTransactionInternal(
         tx = MakeTransactionRef(std::move(txNew));
 
         // Limit size
-        if (GetTransactionWeight(*tx) > MAX_STANDARD_TX_WEIGHT)
+        if ((sign && GetTransactionWeight(*tx) > MAX_STANDARD_TX_WEIGHT) ||
+            (!sign && tx_sizes.second > MAX_STANDARD_TX_WEIGHT))
         {
             error = _("Transaction too large");
             return false;

src/wallet/wallet.h

@@ -1334,8 +1334,8 @@ class WalletRescanReserver
 // Use DummySignatureCreator, which inserts 71 byte signatures everywhere.
 // NOTE: this requires that all inputs must be in mapWallet (eg the tx should
 // be IsAllFromMe).
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig = false) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet);
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig = false);
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig = false) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet);
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig = false);
 
 //! Add wallet name to persistent configuration so it will be loaded on startup.
 bool AddWalletSetting(interfaces::Chain& chain, const std::string& wallet_name);

test/functional/rpc_fundrawtransaction.py

@@ -94,6 +94,7 @@ def run_test(self):
         self.test_address_reuse()
         self.test_option_subtract_fee_from_outputs()
         self.test_subtract_fee_with_presets()
+        self.test_transaction_too_large()
 
     def test_change_position(self):
         """Ensure setting changePosition in fundraw with an exact match is handled properly."""
@@ -907,5 +908,24 @@ def test_subtract_fee_with_presets(self):
         signedtx = self.nodes[0].signrawtransactionwithwallet(fundedtx['hex'])
         self.nodes[0].sendrawtransaction(signedtx['hex'])
 
+    def test_transaction_too_large(self):
+        self.log.info("Test fundrawtx where BnB solution would result in a too large transaction, but Knapsack would not")
+
+        self.nodes[0].createwallet("large")
+        wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+        recipient = self.nodes[0].get_wallet_rpc("large")
+        outputs = {}
+        rawtx = recipient.createrawtransaction([], {wallet.getnewaddress(): 147.99899260})
+
+        # Make 1500 0.1 BTC outputs
+        # The amount that we target for funding is in the BnB range when these outputs are used.
+        # However if these outputs are selected, the transaction will end up being too large, so it shouldn't use BnB and instead fallback to Knapsack
+        # but that behavior is not implemented yet. For now we just check that we get an error.
+        for i in range(0, 1500):
+            outputs[recipient.getnewaddress()] = 0.1
+        wallet.sendmany("", outputs)
+        self.nodes[0].generate(10)
+        assert_raises_rpc_error(-4, "Transaction too large", recipient.fundrawtransaction, rawtx)
+
 if __name__ == '__main__':
     RawTransactionsTest().main()