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[p2p] opportunistically accept 1-parent-1-child packages

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This commit is contained in:
glozow 2024-03-08 13:15:47 +00:00
parent 6c51e1d7d0
commit 87c5c524d6
1 changed files with 196 additions and 2 deletions
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198
src/net_processing.cpp
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@ -596,6 +596,45 @@ private:
void ProcessValidTx(NodeId nodeid, const CTransactionRef& tx, const std::list<CTransactionRef>& replaced_transactions)
EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
/** Handle the results of package validation: calls ProcessValidTx and ProcessInvalidTx for
* individual transactions, and caches rejection for the package as a group.
* @param[in] senders Must contain the nodeids of the peers that provided each transaction
* in package, in the same order.
* */
void ProcessPackageResult(const Package& package, const PackageMempoolAcceptResult& package_result, const std::vector<NodeId>& senders)
EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
/** A package to validate */
struct PackageToValidate {
const Package m_txns;
const std::vector<NodeId> m_senders;
/** Construct a 1-parent-1-child package. */
explicit PackageToValidate(const CTransactionRef& parent,
const CTransactionRef& child,
NodeId parent_sender,
NodeId child_sender) :
m_txns{parent, child},
m_senders {parent_sender, child_sender}
{}
std::string ToString() const {
Assume(m_txns.size() == 2);
return strprintf("parent %s (wtxid=%s, sender=%d) + child %s (wtxid=%s, sender=%d)",
m_txns.front()->GetHash().ToString(),
m_txns.front()->GetWitnessHash().ToString(),
m_senders.front(),
m_txns.back()->GetHash().ToString(),
m_txns.back()->GetWitnessHash().ToString(),
m_senders.back());
}
};
/** Look for a child of this transaction in the orphanage to form a 1-parent-1-child package,
* skipping any combinations that have already been tried. Return the resulting package along with
* the senders of its respective transactions, or std::nullopt if no package is found. */
std::optional<PackageToValidate> Find1P1CPackage(const CTransactionRef& ptx, NodeId nodeid)
EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
/**
* Reconsider orphan transactions after a parent has been accepted to the mempool.
*
@ -3198,6 +3237,117 @@ void PeerManagerImpl::ProcessValidTx(NodeId nodeid, const CTransactionRef& tx, c
}
}
void PeerManagerImpl::ProcessPackageResult(const Package& package, const PackageMempoolAcceptResult& package_result, const std::vector<NodeId>& senders)
{
AssertLockNotHeld(m_peer_mutex);
AssertLockHeld(g_msgproc_mutex);
AssertLockHeld(cs_main);
if (package_result.m_state.IsInvalid()) {
m_recent_rejects_reconsiderable.insert(GetPackageHash(package));
}
// We currently only expect to process 1-parent-1-child packages. Remove if this changes.
if (!Assume(package.size() == 2)) return;
// No package results to look through for PCKG_POLICY or PCKG_MEMPOOL_ERROR
if (package_result.m_state.GetResult() == PackageValidationResult::PCKG_POLICY ||
package_result.m_state.GetResult() == PackageValidationResult::PCKG_MEMPOOL_ERROR) return;
// Iterate backwards to erase in-package descendants from the orphanage before they become
// relevant in AddChildrenToWorkSet.
auto package_iter = package.rbegin();
auto senders_iter = senders.rbegin();
while (package_iter != package.rend()) {
const auto& tx = *package_iter;
const NodeId nodeid = *senders_iter;
const auto it_result{package_result.m_tx_results.find(tx->GetWitnessHash())};
if (Assume(it_result != package_result.m_tx_results.end())) {
const auto& tx_result = it_result->second;
switch (tx_result.m_result_type) {
case MempoolAcceptResult::ResultType::VALID:
{
Assume(tx_result.m_replaced_transactions.has_value());
std::list<CTransactionRef> empty_replacement_list;
ProcessValidTx(nodeid, tx, tx_result.m_replaced_transactions.value_or(empty_replacement_list));
break;
}
case MempoolAcceptResult::ResultType::INVALID:
case MempoolAcceptResult::ResultType::DIFFERENT_WITNESS:
{
// Don't add to vExtraTxnForCompact, as these transactions should have already been
// added there when added to the orphanage or rejected for TX_RECONSIDERABLE.
// This should be updated if package submission is ever used for transactions
// that haven't already been validated before.
ProcessInvalidTx(nodeid, tx, tx_result.m_state, /*maybe_add_extra_compact_tx=*/false);
break;
}
case MempoolAcceptResult::ResultType::MEMPOOL_ENTRY:
{
// AlreadyHaveTx() should be catching transactions that are already in mempool.
Assume(false);
break;
}
}
}
package_iter++;
senders_iter++;
}
}
std::optional<PeerManagerImpl::PackageToValidate> PeerManagerImpl::Find1P1CPackage(const CTransactionRef& ptx, NodeId nodeid)
{
AssertLockNotHeld(m_peer_mutex);
AssertLockHeld(g_msgproc_mutex);
AssertLockHeld(cs_main);
const auto& parent_wtxid{ptx->GetWitnessHash()};
Assume(m_recent_rejects_reconsiderable.contains(parent_wtxid.ToUint256()));
// Prefer children from this peer. This helps prevent censorship attempts in which an attacker
// sends lots of fake children for the parent, and we (unluckily) keep selecting the fake
// children instead of the real one provided by the honest peer.
const auto cpfp_candidates_same_peer{m_orphanage.GetChildrenFromSamePeer(ptx, nodeid)};
// These children should be sorted from newest to oldest. In the (probably uncommon) case
// of children that replace each other, this helps us accept the highest feerate (probably the
// most recent) one efficiently.
for (const auto& child : cpfp_candidates_same_peer) {
Package maybe_cpfp_package{ptx, child};
if (!m_recent_rejects_reconsiderable.contains(GetPackageHash(maybe_cpfp_package))) {
return PeerManagerImpl::PackageToValidate{ptx, child, nodeid, nodeid};
}
}
// If no suitable candidate from the same peer is found, also try children that were provided by
// a different peer. This is useful because sometimes multiple peers announce both transactions
// to us, and we happen to download them from different peers (we wouldn't have known that these
// 2 transactions are related). We still want to find 1p1c packages then.
//
// If we start tracking all announcers of orphans, we can restrict this logic to parent + child
// pairs in which both were provided by the same peer, i.e. delete this step.
const auto cpfp_candidates_different_peer{m_orphanage.GetChildrenFromDifferentPeer(ptx, nodeid)};
// Find the first 1p1c that hasn't already been rejected. We randomize the order to not
// create a bias that attackers can use to delay package acceptance.
//
// Create a random permutation of the indices.
std::vector<size_t> tx_indices(cpfp_candidates_different_peer.size());
std::iota(tx_indices.begin(), tx_indices.end(), 0);
Shuffle(tx_indices.begin(), tx_indices.end(), m_rng);
for (const auto index : tx_indices) {
// If we already tried a package and failed for any reason, the combined hash was
// cached in m_recent_rejects_reconsiderable.
const auto [child_tx, child_sender] = cpfp_candidates_different_peer.at(index);
Package maybe_cpfp_package{ptx, child_tx};
if (!m_recent_rejects_reconsiderable.contains(GetPackageHash(maybe_cpfp_package))) {
return PeerManagerImpl::PackageToValidate{ptx, child_tx, nodeid, child_sender};
}
}
return std::nullopt;
}
bool PeerManagerImpl::ProcessOrphanTx(Peer& peer)
{
AssertLockHeld(g_msgproc_mutex);
@ -4377,6 +4527,20 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
}
}
if (m_recent_rejects_reconsiderable.contains(wtxid)) {
// When a transaction is already in m_recent_rejects_reconsiderable, we shouldn't submit
// it by itself again. However, look for a matching child in the orphanage, as it is
// possible that they succeed as a package.
LogPrint(BCLog::TXPACKAGES, "found tx %s (wtxid=%s) in reconsiderable rejects, looking for child in orphanage\n",
txid.ToString(), wtxid.ToString());
if (auto package_to_validate{Find1P1CPackage(ptx, pfrom.GetId())}) {
const auto package_result{ProcessNewPackage(m_chainman.ActiveChainstate(), m_mempool, package_to_validate->m_txns, /*test_accept=*/false, /*client_maxfeerate=*/std::nullopt)};
LogDebug(BCLog::TXPACKAGES, "package evaluation for %s: %s\n", package_to_validate->ToString(),
package_result.m_state.IsValid() ? "package accepted" : "package rejected");
ProcessPackageResult(package_to_validate->m_txns, package_result, package_to_validate->m_senders);
}
}
// If a tx is detected by m_recent_rejects it is ignored. Because we haven't
// submitted the tx to our mempool, we won't have computed a DoS
// score for it or determined exactly why we consider it invalid.
@ -4418,10 +4582,23 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
}
std::sort(unique_parents.begin(), unique_parents.end());
unique_parents.erase(std::unique(unique_parents.begin(), unique_parents.end()), unique_parents.end());
// Distinguish between parents in m_recent_rejects and m_recent_rejects_reconsiderable.
// We can tolerate having up to 1 parent in m_recent_rejects_reconsiderable since we
// submit 1p1c packages. However, fail immediately if any are in m_recent_rejects.
std::optional<uint256> rejected_parent_reconsiderable;
for (const uint256& parent_txid : unique_parents) {
if (m_recent_rejects.contains(parent_txid)) {
fRejectedParents = true;
break;
} else if (m_recent_rejects_reconsiderable.contains(parent_txid) && !m_mempool.exists(GenTxid::Txid(parent_txid))) {
// More than 1 parent in m_recent_rejects_reconsiderable: 1p1c will not be
// sufficient to accept this package, so just give up here.
if (rejected_parent_reconsiderable.has_value()) {
fRejectedParents = true;
break;
}
rejected_parent_reconsiderable = parent_txid;
}
}
if (!fRejectedParents) {
@ -4435,7 +4612,9 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
// protocol for getting all unconfirmed parents.
const auto gtxid{GenTxid::Txid(parent_txid)};
AddKnownTx(*peer, parent_txid);
if (!AlreadyHaveTx(gtxid, /*include_reconsiderable=*/true)) AddTxAnnouncement(pfrom, gtxid, current_time);
// Exclude m_recent_rejects_reconsiderable: the missing parent may have been
// previously rejected for being too low feerate. This orphan might CPFP it.
if (!AlreadyHaveTx(gtxid, /*include_reconsiderable=*/false)) AddTxAnnouncement(pfrom, gtxid, current_time);
}
if (m_orphanage.AddTx(ptx, pfrom.GetId())) {
@ -4467,6 +4646,19 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
if (state.IsInvalid()) {
ProcessInvalidTx(pfrom.GetId(), ptx, state, /*maybe_add_extra_compact_tx=*/true);
}
// When a transaction fails for TX_RECONSIDERABLE, look for a matching child in the
// orphanage, as it is possible that they succeed as a package.
if (state.GetResult() == TxValidationResult::TX_RECONSIDERABLE) {
LogPrint(BCLog::TXPACKAGES, "tx %s (wtxid=%s) failed but reconsiderable, looking for child in orphanage\n",
txid.ToString(), wtxid.ToString());
if (auto package_to_validate{Find1P1CPackage(ptx, pfrom.GetId())}) {
const auto package_result{ProcessNewPackage(m_chainman.ActiveChainstate(), m_mempool, package_to_validate->m_txns, /*test_accept=*/false, /*client_maxfeerate=*/std::nullopt)};
LogDebug(BCLog::TXPACKAGES, "package evaluation for %s: %s\n", package_to_validate->ToString(),
package_result.m_state.IsValid() ? "package accepted" : "package rejected");
ProcessPackageResult(package_to_validate->m_txns, package_result, package_to_validate->m_senders);
}
}
return;
}
@ -6076,7 +6268,9 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
entry.second.GetHash().ToString(), entry.first);
}
for (const GenTxid& gtxid : requestable) {
if (!AlreadyHaveTx(gtxid, /*include_reconsiderable=*/true)) {
// Exclude m_recent_rejects_reconsiderable: we may be requesting a missing parent
// that was previously rejected for being too low feerate.
if (!AlreadyHaveTx(gtxid, /*include_reconsiderable=*/false)) {
LogPrint(BCLog::NET, "Requesting %s %s peer=%d\n", gtxid.IsWtxid() ? "wtx" : "tx",
gtxid.GetHash().ToString(), pto->GetId());
vGetData.emplace_back(gtxid.IsWtxid() ? MSG_WTX : (MSG_TX | GetFetchFlags(*peer)), gtxid.GetHash());