Merge bitcoin/bitcoin#26551: p2p: Track orphans by who provided them

c58c249 net_processing: indicate more work to do when orphans are ready to reconsider (Anthony Towns)
ecb0a3e net_processing: Don't process tx after processing orphans (Anthony Towns)
c583775 net_processing: only process orphans before messages (Anthony Towns)
be23046 txorphange: Drop redundant originator arg from GetTxToReconsider (Anthony Towns)
a4fe099 txorphanage: index workset by originating peer (Anthony Towns)

Pull request description:

  We currently process orphans by assigning them to the peer that provided a missing parent; instead assign them to the peer that provided the orphan in the first place. This prevents a peer from being able to marginally delay another peer's transactions and also simplifies the internal API slightly. Because we're now associating orphan processing with the peer that provided the orphan originally, we no longer process orphans immediately after receiving the parent, but defer until a future call to `ProcessMessage`.

  Based on #26295

ACKs for top commit:
  naumenkogs:
    utACK c58c249
  glozow:
    ACK c58c249
  mzumsande:
    Code Review ACK c58c249

Tree-SHA512: 3186c346f21e60440266a2a80a9d23d7b96071414e14b2b3bfe50457c04c18b1eab109c3d8c2a7726a6b10a2eda1f0512510a52c102da112820a26f5d96f12de

Author: glozow

src/net_processing.cpp

@@ -584,14 +584,17 @@ class PeerManagerImpl final : public PeerManager
     /**
      * Reconsider orphan transactions after a parent has been accepted to the mempool.
      *
-     * @peer[in]  peer     The peer whose orphan transactions we will reconsider. Generally only one
-     *                     orphan will be reconsidered on each call of this function. This set
-     *                     may be added to if accepting an orphan causes its children to be
-     *                     reconsidered.
-     * @return             True if there are still orphans in this peer's work set.
+     * @peer[in]  peer     The peer whose orphan transactions we will reconsider. Generally only
+     *                     one orphan will be reconsidered on each call of this function. If an
+     *                     accepted orphan has orphaned children, those will need to be
+     *                     reconsidered, creating more work, possibly for other peers.
+     * @return             True if meaningful work was done (an orphan was accepted/rejected).
+     *                     If no meaningful work was done, then the work set for this peer
+     *                     will be empty.
      */
     bool ProcessOrphanTx(Peer& peer)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex);
+
     /** Process a single headers message from a peer.
      *
      * @param[in]   pfrom     CNode of the peer
@@ -2897,34 +2900,32 @@ void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, Peer& peer,
 bool PeerManagerImpl::ProcessOrphanTx(Peer& peer)
 {
     AssertLockHeld(g_msgproc_mutex);
-    AssertLockHeld(cs_main);
+    LOCK(cs_main);
 
     CTransactionRef porphanTx = nullptr;
-    NodeId from_peer = -1;
-    bool more = false;
 
-    while (CTransactionRef porphanTx = m_orphanage.GetTxToReconsider(peer.m_id, from_peer, more)) {
+    while (CTransactionRef porphanTx = m_orphanage.GetTxToReconsider(peer.m_id)) {
         const MempoolAcceptResult result = m_chainman.ProcessTransaction(porphanTx);
         const TxValidationState& state = result.m_state;
         const uint256& orphanHash = porphanTx->GetHash();
 
         if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
             LogPrint(BCLog::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
             RelayTransaction(orphanHash, porphanTx->GetWitnessHash());
-            m_orphanage.AddChildrenToWorkSet(*porphanTx, peer.m_id);
+            m_orphanage.AddChildrenToWorkSet(*porphanTx);
             m_orphanage.EraseTx(orphanHash);
             for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
                 AddToCompactExtraTransactions(removedTx);
             }
-            break;
+            return true;
         } else if (state.GetResult() != TxValidationResult::TX_MISSING_INPUTS) {
             if (state.IsInvalid()) {
                 LogPrint(BCLog::MEMPOOL, "   invalid orphan tx %s from peer=%d. %s\n",
                     orphanHash.ToString(),
-                    from_peer,
+                    peer.m_id,
                     state.ToString());
                 // Maybe punish peer that gave us an invalid orphan tx
-                MaybePunishNodeForTx(from_peer, state);
+                MaybePunishNodeForTx(peer.m_id, state);
             }
             // Has inputs but not accepted to mempool
             // Probably non-standard or insufficient fee
@@ -2959,11 +2960,11 @@ bool PeerManagerImpl::ProcessOrphanTx(Peer& peer)
                 }
             }
             m_orphanage.EraseTx(orphanHash);
-            break;
+            return true;
         }
     }
 
-    return more;
+    return false;
 }
 
 bool PeerManagerImpl::PrepareBlockFilterRequest(CNode& node, Peer& peer,
@@ -4033,7 +4034,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             m_txrequest.ForgetTxHash(tx.GetHash());
             m_txrequest.ForgetTxHash(tx.GetWitnessHash());
             RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
-            m_orphanage.AddChildrenToWorkSet(tx, peer->m_id);
+            m_orphanage.AddChildrenToWorkSet(tx);
 
             pfrom.m_last_tx_time = GetTime<std::chrono::seconds>();
 
@@ -4045,9 +4046,6 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
                 AddToCompactExtraTransactions(removedTx);
             }
-
-            // Recursively process any orphan transactions that depended on this one
-            ProcessOrphanTx(*peer);
         }
         else if (state.GetResult() == TxValidationResult::TX_MISSING_INPUTS)
         {
@@ -4856,16 +4854,12 @@ bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt
         }
     }
 
-    bool has_more_orphans;
-    {
-        LOCK(cs_main);
-        has_more_orphans = ProcessOrphanTx(*peer);
-    }
+    const bool processed_orphan = ProcessOrphanTx(*peer);
 
     if (pfrom->fDisconnect)
         return false;
 
-    if (has_more_orphans) return true;
+    if (processed_orphan) return true;
 
     // this maintains the order of responses
     // and prevents m_getdata_requests to grow unbounded
@@ -4911,6 +4905,12 @@ bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt
             LOCK(peer->m_getdata_requests_mutex);
             if (!peer->m_getdata_requests.empty()) fMoreWork = true;
         }
+        // Does this peer has an orphan ready to reconsider?
+        // (Note: we may have provided a parent for an orphan provided
+        //  by another peer that was already processed; in that case,
+        //  the extra work may not be noticed, possibly resulting in an
+        //  unnecessary 100ms delay)
+        if (m_orphanage.HaveTxToReconsider(peer->m_id)) fMoreWork = true;
     } catch (const std::exception& e) {
         LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' (%s) caught\n", __func__, SanitizeString(msg.m_type), msg.m_message_size, e.what(), typeid(e).name());
     } catch (...) {

src/test/fuzz/txorphan.cpp

@@ -85,16 +85,12 @@ FUZZ_TARGET_INIT(txorphan, initialize_orphanage)
             CallOneOf(
                 fuzzed_data_provider,
                 [&] {
-                    orphanage.AddChildrenToWorkSet(*tx, peer_id);
+                    orphanage.AddChildrenToWorkSet(*tx);
                 },
                 [&] {
                     {
-                        NodeId originator;
-                        bool more = true;
-                        CTransactionRef ref = orphanage.GetTxToReconsider(peer_id, originator, more);
-                        if (!ref) {
-                            Assert(!more);
-                        } else {
+                        CTransactionRef ref = orphanage.GetTxToReconsider(peer_id);
+                        if (ref) {
                             bool have_tx = orphanage.HaveTx(GenTxid::Txid(ref->GetHash())) || orphanage.HaveTx(GenTxid::Wtxid(ref->GetHash()));
                             Assert(have_tx);
                         }

src/txorphanage.cpp

@@ -145,17 +145,19 @@ void TxOrphanage::LimitOrphans(unsigned int max_orphans)
     if (nEvicted > 0) LogPrint(BCLog::MEMPOOL, "orphanage overflow, removed %u tx\n", nEvicted);
 }
 
-void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx, NodeId peer)
+void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx)
 {
     LOCK(m_mutex);
 
-    // Get this peer's work set, emplacing an empty set it didn't exist
-    std::set<uint256>& orphan_work_set = m_peer_work_set.try_emplace(peer).first->second;
 
     for (unsigned int i = 0; i < tx.vout.size(); i++) {
         const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(tx.GetHash(), i));
         if (it_by_prev != m_outpoint_to_orphan_it.end()) {
             for (const auto& elem : it_by_prev->second) {
+                // Get this source peer's work set, emplacing an empty set if it didn't exist
+                // (note: if this peer wasn't still connected, we would have removed the orphan tx already)
+                std::set<uint256>& orphan_work_set = m_peer_work_set.try_emplace(elem->second.fromPeer).first->second;
+                // Add this tx to the work set
                 orphan_work_set.insert(elem->first);
             }
         }
@@ -172,7 +174,7 @@ bool TxOrphanage::HaveTx(const GenTxid& gtxid) const
     }
 }
 
-CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer, NodeId& originator, bool& more)
+CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer)
 {
     LOCK(m_mutex);
 
@@ -185,16 +187,25 @@ CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer, NodeId& originator,
 
             const auto orphan_it = m_orphans.find(txid);
             if (orphan_it != m_orphans.end()) {
-                more = !work_set.empty();
-                originator = orphan_it->second.fromPeer;
                 return orphan_it->second.tx;
             }
         }
     }
-    more = false;
     return nullptr;
 }
 
+bool TxOrphanage::HaveTxToReconsider(NodeId peer)
+{
+    LOCK(m_mutex);
+
+    auto work_set_it = m_peer_work_set.find(peer);
+    if (work_set_it != m_peer_work_set.end()) {
+        auto& work_set = work_set_it->second;
+        return !work_set.empty();
+    }
+    return false;
+}
+
 void TxOrphanage::EraseForBlock(const CBlock& block)
 {
     LOCK(m_mutex);

src/txorphanage.h

@@ -27,13 +27,11 @@ class TxOrphanage {
     bool HaveTx(const GenTxid& gtxid) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
 
     /** Extract a transaction from a peer's work set
-     *  Returns nullptr and sets more to false if there are no transactions
-     *  to work on. Otherwise returns the transaction reference, removes
-     *  the transaction from the work set, and populates its arguments with
-     *  the originating peer, and whether there are more orphans for this peer
-     *  to work on after this tx.
+     *  Returns nullptr if there are no transactions to work on.
+     *  Otherwise returns the transaction reference, and removes
+     *  it from the work set.
      */
-    CTransactionRef GetTxToReconsider(NodeId peer, NodeId& originator, bool& more) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    CTransactionRef GetTxToReconsider(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
 
     /** Erase an orphan by txid */
     int EraseTx(const uint256& txid) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
@@ -47,8 +45,11 @@ class TxOrphanage {
     /** Limit the orphanage to the given maximum */
     void LimitOrphans(unsigned int max_orphans) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
 
-    /** Add any orphans that list a particular tx as a parent into a peer's work set */
-    void AddChildrenToWorkSet(const CTransaction& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    /** Add any orphans that list a particular tx as a parent into the from peer's work set */
+    void AddChildrenToWorkSet(const CTransaction& tx) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);;
+
+    /** Does this peer have any work to do? */
+    bool HaveTxToReconsider(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);;
 
     /** Return how many entries exist in the orphange */
     size_t Size() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
@@ -72,7 +73,7 @@ class TxOrphanage {
      *  -maxorphantx/DEFAULT_MAX_ORPHAN_TRANSACTIONS */
     std::map<uint256, OrphanTx> m_orphans GUARDED_BY(m_mutex);
 
-    /** Which peer provided a parent tx of orphans that need to be reconsidered */
+    /** Which peer provided the orphans that need to be reconsidered */
     std::map<NodeId, std::set<uint256>> m_peer_work_set GUARDED_BY(m_mutex);
 
     using OrphanMap = decltype(m_orphans);