Merge bitcoin/bitcoin#30295: #28984 package rbf followups

3f00aae package rbf: cpfp structure requires package > parent feerate (Greg Sanders)
ad7f1f6 test package rbf boundary conditions more closely (Greg Sanders)
ff4558d doc: reword package RBF documentation (Greg Sanders)
de669a8 doc: replace mention of V3 with TRUC (Greg Sanders)

Pull request description:

  Some suggested nits/changes from #28984

ACKs for top commit:
  glozow:
    ACK 3f00aae
  murchandamus:
    ACK 3f00aae

Tree-SHA512: 79434cc8aba25a43e99793298cdc99cad807db2c3a2e780a31953f244b95eecd97b90559abd67fbf30996c00966675fa257253a7812ec4727420226162c629ae

Author: fanquake

doc/policy/packages.md

@@ -38,11 +38,11 @@ The following rules are enforced for all packages:
 
 * Only limited package replacements are currently considered. (#28984)
 
-   - All direct conflicts must signal replacement (or have `-mempoolfullrbf=1` set).
+   - All direct conflicts must signal replacement (or the node must have `-mempoolfullrbf=1` set).
 
    - Packages are 1-parent-1-child, with no in-mempool ancestors of the package.
 
-   - All conflicting clusters(connected components of mempool transactions) must be clusters of up to size 2.
+   - All conflicting clusters (connected components of mempool transactions) must be clusters of up to size 2.
 
    - No more than MAX_REPLACEMENT_CANDIDATES transactions can be replaced, analogous to
      regular [replacement rule](./mempool-replacements.md) 5).
@@ -56,7 +56,7 @@ The following rules are enforced for all packages:
 
    - *Rationale*: Basic support for package RBF can be used by wallets
      by making chains of no longer than two, then directly conflicting
-     those chains when needed. Combined with V3 transactions this can
+     those chains when needed. Combined with TRUC transactions this can
      result in more robust fee bumping. More general package RBF may be
      enabled in the future.
 

src/validation.cpp

@@ -1208,7 +1208,7 @@ bool MemPoolAccept::PackageMempoolChecks(const std::vector<CTransactionRef>& txn
     const CFeeRate package_feerate(m_subpackage.m_total_modified_fees, m_subpackage.m_total_vsize);
     if (package_feerate <= parent_feerate) {
         return package_state.Invalid(PackageValidationResult::PCKG_POLICY,
-                                     "package RBF failed: package feerate is less than parent feerate",
+                                     "package RBF failed: package feerate is less than or equal to parent feerate",
                                      strprintf("package feerate %s <= parent feerate is %s", package_feerate.ToString(), parent_feerate.ToString()));
     }
 

test/functional/mempool_package_rbf.py

@@ -168,23 +168,35 @@ def test_package_rbf_additional_fees(self):
         self.assert_mempool_contents(expected=package_txns1)
 
         self.log.info("Check replacement pays for incremental bandwidth")
-        package_hex3, package_txns3 = self.create_simple_package(coin, parent_fee=DEFAULT_FEE, child_fee=DEFAULT_CHILD_FEE)
-        pkg_results3 = node.submitpackage(package_hex3)
-        assert_equal(f"package RBF failed: insufficient anti-DoS fees, rejecting replacement {package_txns3[1].rehash()}, not enough additional fees to relay; 0.00 < 0.00000{sum([tx.get_vsize() for tx in package_txns3])}", pkg_results3["package_msg"])
-
+        _, placeholder_txns3 = self.create_simple_package(coin)
+        package_3_size = sum([tx.get_vsize() for tx in placeholder_txns3])
+        incremental_sats_required = Decimal(package_3_size) / COIN
+        incremental_sats_short = incremental_sats_required - Decimal("0.00000001")
+        # Recreate the package with slightly higher fee once we know the size of the new package, but still short of required fee
+        failure_package_hex3, failure_package_txns3 = self.create_simple_package(coin, parent_fee=DEFAULT_FEE, child_fee=DEFAULT_CHILD_FEE + incremental_sats_short)
+        assert_equal(package_3_size, sum([tx.get_vsize() for tx in failure_package_txns3]))
+        pkg_results3 = node.submitpackage(failure_package_hex3)
+        assert_equal(f"package RBF failed: insufficient anti-DoS fees, rejecting replacement {failure_package_txns3[1].rehash()}, not enough additional fees to relay; {incremental_sats_short} < {incremental_sats_required}", pkg_results3["package_msg"])
         self.assert_mempool_contents(expected=package_txns1)
+
+        success_package_hex3, success_package_txns3 = self.create_simple_package(coin, parent_fee=DEFAULT_FEE, child_fee=DEFAULT_CHILD_FEE + incremental_sats_required)
+        node.submitpackage(success_package_hex3)
+        self.assert_mempool_contents(expected=success_package_txns3)
         self.generate(node, 1)
 
         self.log.info("Check Package RBF must have strict cpfp structure")
         coin = self.coins.pop()
         package_hex4, package_txns4 = self.create_simple_package(coin, parent_fee=DEFAULT_FEE, child_fee=DEFAULT_CHILD_FEE)
         node.submitpackage(package_hex4)
         self.assert_mempool_contents(expected=package_txns4)
-        package_hex5, package_txns5 = self.create_simple_package(coin, parent_fee=DEFAULT_CHILD_FEE, child_fee=DEFAULT_CHILD_FEE - Decimal("0.00000001"))
+        package_hex5, package_txns5 = self.create_simple_package(coin, parent_fee=DEFAULT_CHILD_FEE, child_fee=DEFAULT_CHILD_FEE)
         pkg_results5 = node.submitpackage(package_hex5)
-        assert 'package RBF failed: package feerate is less than parent feerate' in pkg_results5["package_msg"]
-
+        assert 'package RBF failed: package feerate is less than or equal to parent feerate' in pkg_results5["package_msg"]
         self.assert_mempool_contents(expected=package_txns4)
+
+        package_hex5_1, package_txns5_1 = self.create_simple_package(coin, parent_fee=DEFAULT_CHILD_FEE, child_fee=DEFAULT_CHILD_FEE + Decimal("0.00000001"))
+        node.submitpackage(package_hex5_1)
+        self.assert_mempool_contents(expected=package_txns5_1)
         self.generate(node, 1)
 
     def test_package_rbf_max_conflicts(self):