Merge bitcoin/bitcoin#22674: validation: mempool validation and submission for packages of 1 child + parents

046e8ff264be6b888c0f9a9d822e32aa74e19b78 [unit test] package submission (glozow)
e12fafda2dfbbdf63f125e5af797ecfaa6488f66 [validation] de-duplicate package transactions already in mempool (glozow)
8310d942e046c5a9b6bd90afdcd3af68dd91e081 [packages] add sanity checks for package vs mempool limits (glozow)
be3ff151a1f9665720cdf70d072b098a2f9726a9 [validation] full package accept + mempool submission (glozow)
144a29099a865ac1dc3e5291d9529fbcca9c83a4 [policy] require submitted packages to be child-with-unconfirmed-parents (glozow)
d59ddc5c3d1c035474d7bc9fa9f8a0eeb1c8498c [packages/doc] define and document package rules (glozow)
ba26169f6035c238378a3c9647213328a006fa23 [unit test] context-free package checks (glozow)
9b2fdca7f03911ac40fe0f8a0b5da534bee4554b [packages] add static IsChildWithParents function (glozow)

Pull request description:

  This is 1 chunk of [Package Mempool Accept](https://gist.github.com/glozow/dc4e9d5c5b14ade7cdfac40f43adb18a); it restricts packages to 1 child with its parents, doesn't allow conflicts, and doesn't have CPFP (yet).  Future PRs (see #22290) will add RBF and CPFP within packages.

ACKs for top commit:
  laanwj:
    Code review ACK 046e8ff264be6b888c0f9a9d822e32aa74e19b78

Tree-SHA512: 37dbba37d527712f8efef71ee05c90a8308992615af35f5e0cfeafc60d859cc792737d125aac526e37742fe7683ac8c155ac24af562426213904333c01260c95

1 files changed, 27 insertions, 11 deletions

diff --git a/src/validation.h b/src/validation.h
index 534df9bc87..ddfc8df939 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -60,6 +60,16 @@ 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;
+
+// If a package is submitted, it must be within the mempool's ancestor/descendant limits. Since a
+// submitted package must be child-with-unconfirmed-parents (all of the transactions are an ancestor
+// of the child), package limits are ultimately bounded by mempool package limits. Ensure that the
+// defaults reflect this constraint.
+static_assert(DEFAULT_DESCENDANT_LIMIT >= MAX_PACKAGE_COUNT);
+static_assert(DEFAULT_ANCESTOR_LIMIT >= MAX_PACKAGE_COUNT);
+static_assert(DEFAULT_ANCESTOR_SIZE_LIMIT >= MAX_PACKAGE_SIZE);
+static_assert(DEFAULT_DESCENDANT_SIZE_LIMIT >= MAX_PACKAGE_SIZE);
+
 /** Default for -mempoolexpiry, expiration time for mempool transactions in hours */
 static const unsigned int DEFAULT_MEMPOOL_EXPIRY = 336;
 /** Maximum number of dedicated script-checking threads allowed */
@@ -151,17 +161,19 @@ struct MempoolAcceptResult {
     enum class ResultType {
         VALID, //!> Fully validated, valid.
         INVALID, //!> Invalid.
+        MEMPOOL_ENTRY, //!> Valid, transaction was already in the mempool.
     };
     const ResultType m_result_type;
     const TxValidationState m_state;
 
-    // The following fields are only present when m_result_type = ResultType::VALID
+    // The following fields are only present when m_result_type = ResultType::VALID or MEMPOOL_ENTRY
     /** Mempool transactions replaced by the tx per BIP 125 rules. */
     const std::optional<std::list<CTransactionRef>> m_replaced_transactions;
     /** Virtual size as used by the mempool, calculated using serialized size and sigops. */
     const std::optional<int64_t> m_vsize;
     /** Raw base fees in satoshis. */
     const std::optional<CAmount> m_base_fees;
+
     static MempoolAcceptResult Failure(TxValidationState state) {
         return MempoolAcceptResult(state);
     }
@@ -170,6 +182,10 @@ struct MempoolAcceptResult {
         return MempoolAcceptResult(std::move(replaced_txns), vsize, fees);
     }
 
+    static MempoolAcceptResult MempoolTx(int64_t vsize, CAmount fees) {
+        return MempoolAcceptResult(vsize, fees);
+    }
+
 // Private constructors. Use static methods MempoolAcceptResult::Success, etc. to construct.
 private:
     /** Constructor for failure case */
@@ -182,6 +198,10 @@ private:
     explicit MempoolAcceptResult(std::list<CTransactionRef>&& replaced_txns, int64_t vsize, CAmount fees)
         : m_result_type(ResultType::VALID),
         m_replaced_transactions(std::move(replaced_txns)), m_vsize{vsize}, m_base_fees(fees) {}
+
+    /** Constructor for already-in-mempool case. It wouldn't replace any transactions. */
+    explicit MempoolAcceptResult(int64_t vsize, CAmount fees)
+        : m_result_type(ResultType::MEMPOOL_ENTRY), m_vsize{vsize}, m_base_fees(fees) {}
 };
 
 /**
@@ -191,7 +211,7 @@ struct PackageMempoolAcceptResult
 {
     const PackageValidationState m_state;
     /**
-    * Map from wtxid to finished MempoolAcceptResults. The client is responsible
+    * Map from (w)txid to finished MempoolAcceptResults. The client is responsible
     * for keeping track of the transaction objects themselves. If a result is not
     * present, it means validation was unfinished for that transaction. If there
     * was a package-wide error (see result in m_state), m_tx_results will be empty.
@@ -225,16 +245,12 @@ MempoolAcceptResult AcceptToMemoryPool(CChainState& active_chainstate, const CTr
     EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
 /**
-* Atomically test acceptance of a package. If the package only contains one tx, package rules still
-* apply. Package validation does not allow BIP125 replacements, so the transaction(s) cannot spend
-* the same inputs as any transaction in the mempool.
-* @param[in]    txns                Group of transactions which may be independent or contain
-*                                   parent-child dependencies. The transactions must not conflict
-*                                   with each other, i.e., must not spend the same inputs. If any
-*                                   dependencies exist, parents must appear anywhere in the list
-*                                   before their children.
+* Validate (and maybe submit) a package to the mempool. See doc/policy/packages.md for full details
+* on package validation rules.
+* @param[in]    test_accept     When true, run validation checks but don't submit to mempool.
 * @returns a PackageMempoolAcceptResult which includes a MempoolAcceptResult for each transaction.
-* If a transaction fails, validation will exit early and some results may be missing.
+* If a transaction fails, validation will exit early and some results may be missing. It is also
+* possible for the package to be partially submitted.
 */
 PackageMempoolAcceptResult ProcessNewPackage(CChainState& active_chainstate, CTxMemPool& pool,
                                                    const Package& txns, bool test_accept)