Wallet: don't create transaction chains that will be rejected by mempool by default

src/wallet/wallet.h

@@ -98,7 +98,7 @@ static const CAmount WALLET_INCREMENTAL_RELAY_FEE = 5000;
 //! Default for -spendzeroconfchange
 static const bool DEFAULT_SPEND_ZEROCONF_CHANGE = true;
 //! Default for -walletrejectlongchains
-static const bool DEFAULT_WALLET_REJECT_LONG_CHAINS = false;
+static const bool DEFAULT_WALLET_REJECT_LONG_CHAINS{true};
 //! -txconfirmtarget default
 static const unsigned int DEFAULT_TX_CONFIRM_TARGET = 6;
 //! -walletrbf default

test/functional/wallet_balance.py

@@ -53,7 +53,9 @@ def set_test_params(self):
         self.num_nodes = 2
         self.setup_clean_chain = True
         self.extra_args = [
-            ['-limitdescendantcount=3'],  # Limit mempool descendants as a hack to have wallet txs rejected from the mempool
+            # Limit mempool descendants as a hack to have wallet txs rejected from the mempool.
+            # Set walletrejectlongchains=0 so the wallet still creates the transactions.
+            ['-limitdescendantcount=3', '-walletrejectlongchains=0'],
             [],
         ]
 

test/functional/wallet_basic.py

@@ -27,6 +27,7 @@ def set_test_params(self):
         self.extra_args = [[
             "-acceptnonstdtxn=1",
             "-bech32_hrp=bcrt",
+            "-walletrejectlongchains=0"
         ]] * self.num_nodes
         self.setup_clean_chain = True
         self.supports_cli = False
@@ -143,7 +144,7 @@ def run_test(self):
         self.nodes[2].lockunspent(False, [unspent_0], True)
 
         # Restarting the node with the lock written to the wallet should keep the lock
-        self.restart_node(2)
+        self.restart_node(2, ["-walletrejectlongchains=0"])
         assert_raises_rpc_error(-8, "Invalid parameter, output already locked", self.nodes[2].lockunspent, False, [unspent_0])
 
         # Unloading and reloading the wallet with a persistent lock should keep the lock
@@ -573,7 +574,7 @@ def run_test(self):
         self.log.info("Test -reindex")
         self.stop_nodes()
         # set lower ancestor limit for later
-        self.start_node(0, ['-reindex', "-limitancestorcount=" + str(chainlimit)])
+        self.start_node(0, ['-reindex', "-walletrejectlongchains=0", "-limitancestorcount=" + str(chainlimit)])
         self.start_node(1, ['-reindex', "-limitancestorcount=" + str(chainlimit)])
         self.start_node(2, ['-reindex', "-limitancestorcount=" + str(chainlimit)])
         # reindex will leave rpc warm up "early"; Wait for it to finish

test/functional/wallet_create_tx.py

@@ -29,6 +29,7 @@ def run_test(self):
 
         self.test_anti_fee_sniping()
         self.test_tx_size_too_large()
+        self.test_create_too_long_mempool_chain()
 
     def test_anti_fee_sniping(self):
         self.log.info('Check that we have some (old) blocks and that anti-fee-sniping is disabled')
@@ -80,6 +81,31 @@ def test_tx_size_too_large(self):
         )
         self.nodes[0].settxfee(0)
 
+    def test_create_too_long_mempool_chain(self):
+        self.log.info('Check too-long mempool chain error')
+        df_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        self.nodes[0].createwallet("too_long")
+        test_wallet = self.nodes[0].get_wallet_rpc("too_long")
+
+        tx_data = df_wallet.send(outputs=[{test_wallet.getnewaddress(): 25}], options={"change_position": 0})
+        txid = tx_data['txid']
+        vout = 1
+
+        options = {"change_position": 0, "add_inputs": False}
+        for i in range(1, 25):
+            options['inputs'] = [{'txid': txid, 'vout': vout}]
+            tx_data = test_wallet.send(outputs=[{test_wallet.getnewaddress(): 25 - i}], options=options)
+            txid = tx_data['txid']
+
+        # Sending one more chained transaction will fail
+        options = {"include_unsafe": True, 'add_inputs': True}
+        assert_raises_rpc_error(-4, "Insufficient funds",
+                                test_wallet.send, outputs=[{test_wallet.getnewaddress(): 0.3}], options=options)
+
+        test_wallet.unloadwallet()
+
+
 
 if __name__ == '__main__':
     CreateTxWalletTest().main()