Merge #16421: Conservatively accept RBF bumps bumping one tx at the package limits

5ce822efbe45513ce3517c1ca731ac6d6a0c3b54 Conservatively accept RBF bumps bumping one tx at the package limits (Matt Corallo)

Pull request description:

  Based on #15681, this adds support for some simple cases of RBF inside of large packages. Issue pointed out by sdaftuar in #15681, and this fix (or a broader one) is required ot make #15681 fully useful.

  Accept RBF bumps of single transactions (ie which evict exactly one
  transaction) even when that transaction is a member of a package
  which is currently at the package limit iff the new transaction
  does not add any additional mempool dependencies from the original.

  This could be made a bit looser in the future and still be safe,
  but for now this fixes the case that a transaction which was
  accepted by the carve-out rule will not be directly RBF'able

ACKs for top commit:
  instagibbs:
    re-ACK https://github.com/bitcoin/bitcoin/pull/16421/commits/5ce822efbe45513ce3517c1ca731ac6d6a0c3b54
  ajtowns:
    ACK 5ce822efbe45513ce3517c1ca731ac6d6a0c3b54 ; GetSizeWithDescendants is only change and makes sense
  sipa:
    Code review ACK 5ce822efbe45513ce3517c1ca731ac6d6a0c3b54. I haven't thought hard about the effect on potential DoS issues this policy change may have.

Tree-SHA512: 1cee3bc57393940a30206679eb60c3ec8cb4f4825d27d40d1f062c86bd22542dd5944fa5567601c74c8d9fd425333ed3e686195170925cfc68777e861844bd55

1 files changed, 8 insertions, 2 deletions

diff --git a/test/functional/mempool_package_onemore.py b/test/functional/mempool_package_onemore.py
index 30f851fb8e..0739d7e29b 100755
--- a/test/functional/mempool_package_onemore.py
+++ b/test/functional/mempool_package_onemore.py
@@ -33,7 +33,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
         outputs = {}
         for i in range(num_outputs):
             outputs[node.getnewaddress()] = send_value
-        rawtx = node.createrawtransaction(inputs, outputs)
+        rawtx = node.createrawtransaction(inputs, outputs, 0, True)
         signedtx = node.signrawtransactionwithwallet(rawtx)
         txid = node.sendrawtransaction(signedtx['hex'])
         fulltx = node.getrawtransaction(txid, 1)
@@ -75,10 +75,16 @@ class MempoolPackagesTest(BitcoinTestFramework):
         # ...especially if its > 40k weight
         assert_raises_rpc_error(-26, "too-long-mempool-chain, too many descendants", self.chain_transaction, self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 350)
         # But not if it chains directly off the first transaction
-        self.chain_transaction(self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 1)
+        (replacable_txid, replacable_orig_value) = self.chain_transaction(self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 1)
         # and the second chain should work just fine
         self.chain_transaction(self.nodes[0], [second_chain], [0], second_chain_value, fee, 1)
 
+        # Make sure we can RBF the chain which used our carve-out rule
+        second_tx_outputs = {self.nodes[0].getrawtransaction(replacable_txid, True)["vout"][0]['scriptPubKey']['addresses'][0]: replacable_orig_value - (Decimal(1) / Decimal(100))}
+        second_tx = self.nodes[0].createrawtransaction([{'txid': chain[0][0], 'vout': 1}], second_tx_outputs)
+        signed_second_tx = self.nodes[0].signrawtransactionwithwallet(second_tx)
+        self.nodes[0].sendrawtransaction(signed_second_tx['hex'])
+
         # Finally, check that we added two transactions
         assert_equal(len(self.nodes[0].getrawmempool(True)), MAX_ANCESTORS + 3)