Merge bitcoin/bitcoin#28984: Cluster size 2 package rbf

94ed4fbf8e1a396c650b5134d396d6c0be35ce10 Add release note for size 2 package rbf (Greg Sanders)
afd52d8e63ed323a159ea49fd1f10542abeacb97 doc: update package RBF comment (Greg Sanders)
6e3c4394cfadf32c06c8c4732d136ca10c316721 mempool: Improve logging of replaced transactions (Greg Sanders)
d3466e4cc5051c314873dd14ec8f7a88494c0780 CheckPackageMempoolAcceptResult: Check package rbf invariants (Greg Sanders)
316d7b63c97144ba3e21201315c784852210f8ff Fuzz: pass mempool to CheckPackageMempoolAcceptResult (Greg Sanders)
4d15bcf448eb3c4451b63e8f78cc61f3f9f9b639 [test] package rbf (glozow)
dc21f61c72e5a97d974ca2c5cb70b8328f4fab2a [policy] package rbf (Suhas Daftuar)
5da396781589177d4ceb3b4b59c9f309a5e4d029 PackageV3Checks: Relax assumptions (Greg Sanders)

Pull request description:

  Allows any 2 transaction package with no in-mempool ancestors to do package RBF when directly conflicting with other mempool clusters of size two or less.

  Proposed validation steps:
  1) If the transaction package is of size 1, legacy rbf rules apply.
  2) Otherwise the transaction package consists of a (parent, child) pair with no other in-mempool ancestors (or descendants, obviously), so it is also going to create a cluster of size 2. If larger, fail.
  3) The package rbf may not evict more than 100 transactions from the mempool(bip125 rule 5)
  4) The package is a single chunk
  5) Every directly conflicted mempool transaction is connected to at most 1 other in-mempool transaction (ie the cluster size of the conflict is at most 2).
  6) Diagram check: We ensure that the replacement is strictly superior, improving the mempool
  7) The total fee of the package, minus the total fee of what is being evicted, is at least the minrelayfee * size of the package (equivalent to bip125 rule 3 and 4)

  Post-cluster mempool this will likely be expanded to general package rbf, but this is what we can safely support today.

ACKs for top commit:
  achow101:
    ACK 94ed4fbf8e1a396c650b5134d396d6c0be35ce10
  glozow:
    reACK 94ed4fbf8e via range-diff
  ismaelsadeeq:
    re-ACK 94ed4fbf8e1a396c650b5134d396d6c0be35ce10
  theStack:
    Code-review ACK 94ed4fbf8e1a396c650b5134d396d6c0be35ce10
  murchandamus:
    utACK 94ed4fbf8e1a396c650b5134d396d6c0be35ce10

Tree-SHA512: 9bd383e695964f362f147482bbf73b1e77c4d792bda2e91d7f30d74b3540a09146a5528baf86854a113005581e8c75f04737302517b7d5124296bd7a151e3992

1 files changed, 1 insertions, 5 deletions

diff --git a/src/policy/v3_policy.cpp b/src/policy/v3_policy.cpp
index bcf0b2b236..6bd043b8e3 100644
--- a/src/policy/v3_policy.cpp
+++ b/src/policy/v3_policy.cpp
@@ -91,7 +91,6 @@ std::optional<std::string> PackageV3Checks(const CTransactionRef& ptx, int64_t v
             const auto parent_info = [&] {
                 if (mempool_ancestors.size() > 0) {
                     auto& mempool_parent = *mempool_ancestors.begin();
-                    Assume(mempool_parent->GetCountWithDescendants() == 1);
                     return ParentInfo{mempool_parent->GetTx().GetHash(),
                                       mempool_parent->GetTx().GetWitnessHash(),
                                       mempool_parent->GetTx().version,
@@ -135,10 +134,7 @@ std::optional<std::string> PackageV3Checks(const CTransactionRef& ptx, int64_t v
                 }
             }
 
-            // It shouldn't be possible to have any mempool siblings at this point. SingleV3Checks
-            // catches mempool siblings and sibling eviction is not extended to packages. Also, if the package consists of connected transactions,
-            // any tx having a mempool ancestor would mean the package exceeds ancestor limits.
-            if (!Assume(!parent_info.m_has_mempool_descendant)) {
+            if (parent_info.m_has_mempool_descendant) {
                 return strprintf("tx %s (wtxid=%s) would exceed descendant count limit",
                                 parent_info.m_txid.ToString(), parent_info.m_wtxid.ToString());
             }