Merge #15681: [mempool] Allow one extra single-ancestor transaction per package

50cede3f5a [mempool] Allow one extra single-ancestor transaction per package (Matt Corallo)

Pull request description:

  This implements the proposed policy change from [1], which allows
  certain classes of contract protocols involving revocation
  punishments to use CPFP. Note that some such use-cases may still
  want some form of one-deep package relay, though even this alone
  may greatly simplify some lightning fee negotiation.

  [1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-November/016518.html

ACKs for top commit:
  ajtowns:
    ACK 50cede3f5a -- looked over code again, compared with previous commit, compiles, etc.
  sdaftuar:
    ACK 50cede3f5a
  ryanofsky:
    utACK 50cede3f5a. Changes since last review: adding EXTRA_DESCENDANT_TX_SIZE_LIMIT constant, changing max ancestor size from 1,000,000 to nLimitAncestorSize constant (101,000), fixing test comment and getting rid of unused test node.

Tree-SHA512: b052c2a0f384855572b4579310131897b612201214b5abbb225167224e4f550049e300b471dbf320928652571e92ca2d650050b7cf39ac92b3bc1d2bcd386c1c
This commit is contained in:
Wladimir J. van der Laan
2019-07-19 19:56:12 +02:00
4 changed files with 108 additions and 1 deletions

View File

@@ -616,7 +616,21 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
size_t nLimitDescendantSize = gArgs.GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT)*1000;
std::string errString;
if (!pool.CalculateMemPoolAncestors(entry, setAncestors, nLimitAncestors, nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, errString)) {
return state.Invalid(ValidationInvalidReason::TX_MEMPOOL_POLICY, false, REJECT_NONSTANDARD, "too-long-mempool-chain", errString);
setAncestors.clear();
// If the new transaction is relatively small (up to 40k weight)
// and has at most one ancestor (ie ancestor limit of 2, including
// the new transaction), allow it if its parent has exactly the
// descendant limit descendants.
//
// This allows protocols which rely on distrusting counterparties
// being able to broadcast descendants of an unconfirmed transaction
// to be secure by simply only having two immediately-spendable
// outputs - one for each counterparty. For more info on the uses for
// this, see https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-November/016518.html
if (nSize > EXTRA_DESCENDANT_TX_SIZE_LIMIT ||
!pool.CalculateMemPoolAncestors(entry, setAncestors, 2, nLimitAncestorSize, nLimitDescendants + 1, nLimitDescendantSize + EXTRA_DESCENDANT_TX_SIZE_LIMIT, errString)) {
return state.Invalid(ValidationInvalidReason::TX_MEMPOOL_POLICY, false, REJECT_NONSTANDARD, "too-long-mempool-chain", errString);
}
}
// A transaction that spends outputs that would be replaced by it is invalid. Now