diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/validation.cpp | 16 | ||||
| -rw-r--r-- | src/validation.h | 6 |
2 files changed, 21 insertions, 1 deletions
diff --git a/src/validation.cpp b/src/validation.cpp index 0bc6167bad..f585bc7d2d 100644 --- a/src/validation.cpp +++ b/src/validation.cpp @@ -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 diff --git a/src/validation.h b/src/validation.h index 7739d3de4a..d747fdbf27 100644 --- a/src/validation.h +++ b/src/validation.h @@ -64,6 +64,12 @@ static const unsigned int DEFAULT_ANCESTOR_SIZE_LIMIT = 101; static const unsigned int DEFAULT_DESCENDANT_LIMIT = 25; /** Default for -limitdescendantsize, maximum kilobytes of in-mempool descendants */ static const unsigned int DEFAULT_DESCENDANT_SIZE_LIMIT = 101; +/** + * An extra transaction can be added to a package, as long as it only has one + * ancestor and is no larger than this. Not really any reason to make this + * configurable as it doesn't materially change DoS parameters. + */ +static const unsigned int EXTRA_DESCENDANT_TX_SIZE_LIMIT = 10000; /** Default for -mempoolexpiry, expiration time for mempool transactions in hours */ static const unsigned int DEFAULT_MEMPOOL_EXPIRY = 336; /** Maximum kilobytes for transactions to store for processing during reorg */ |