refactor: move CInstantSendManager::AskNodesForLockedTx into PeerManager

**This does change the logic!** We no longer prioritize asking MNs. This is probably fine? I don't specifically recall why we wanted to ask MNs besides potentially that they may be higher performing or better connected? We can potentially restore this logic once we bring masternode connection logic into Peer

Does also change logic, by short-circuiting once peersToAsk is full.

This commit has the added benefit of reducing contention on m_nodes_mutex due to no-longer calling connman.ForEachNode not once but twice

This may slightly increase contention on m_peer_mutex; but that should be an ok tradeoff for not only removing dependencies, but also reducing contention on a much more contested RecursiveMutex

src/llmq/context.cpp

@@ -46,9 +46,9 @@ LLMQContext::LLMQContext(ChainstateManager& chainman, CConnman& connman, CDeterm
     isman{[&]() -> llmq::CInstantSendManager* const {
         assert(llmq::quorumInstantSendManager == nullptr);
         llmq::quorumInstantSendManager = std::make_unique<llmq::CInstantSendManager>(*llmq::chainLocksHandler,
-                                                                                     chainman.ActiveChainstate(),
-                                                                                     connman, *qman, *sigman, *shareman,
-                                                                                     sporkman, mempool, mn_sync, peerman,
+                                                                                     chainman.ActiveChainstate(), *qman,
+                                                                                     *sigman, *shareman, sporkman,
+                                                                                     mempool, mn_sync, peerman,
                                                                                      is_masternode, unit_tests, wipe);
         return llmq::quorumInstantSendManager.get();
     }()},

src/llmq/instantsend.cpp

@@ -1047,7 +1047,7 @@ void CInstantSendManager::ProcessInstantSendLock(NodeId from, const uint256& has
         // bump mempool counter to make sure newly locked txes are picked up by getblocktemplate
         mempool.AddTransactionsUpdated(1);
     } else {
-        AskNodesForLockedTx(islock->txid, connman, *m_peerman, m_is_masternode);
+        m_peerman->AskPeersForTransaction(islock->txid, m_is_masternode);
     }
 }
 
@@ -1321,7 +1321,7 @@ void CInstantSendManager::RemoveMempoolConflictsForLock(const uint256& hash, con
         for (const auto& p : toDelete) {
             RemoveConflictedTx(*p.second);
         }
-        AskNodesForLockedTx(islock.txid, connman, *m_peerman, m_is_masternode);
+        m_peerman->AskPeersForTransaction(islock.txid, m_is_masternode);
     }
 }
 
@@ -1426,46 +1426,6 @@ void CInstantSendManager::RemoveConflictingLock(const uint256& islockHash, const
     }
 }
 
-void CInstantSendManager::AskNodesForLockedTx(const uint256& txid, const CConnman& connman, PeerManager& peerman,
-                                              bool is_masternode)
-{
-    std::vector<CNode*> nodesToAskFor;
-    nodesToAskFor.reserve(4);
-
-    auto maybe_add_to_nodesToAskFor = [&peerman, &nodesToAskFor, &txid](CNode* pnode) {
-        if (nodesToAskFor.size() >= 4) {
-            return;
-        }
-        if (peerman.IsInvInFilter(pnode->GetId(), txid)) {
-            pnode->AddRef();
-            nodesToAskFor.emplace_back(pnode);
-        }
-    };
-
-    connman.ForEachNode([&](CNode* pnode) {
-        // Check masternodes first
-        if (pnode->m_masternode_connection) maybe_add_to_nodesToAskFor(pnode);
-    });
-    connman.ForEachNode([&](CNode* pnode) {
-        // Check non-masternodes next
-        if (!pnode->m_masternode_connection) maybe_add_to_nodesToAskFor(pnode);
-    });
-    {
-        LOCK(cs_main);
-        for (const CNode* pnode : nodesToAskFor) {
-            LogPrintf("CInstantSendManager::%s -- txid=%s: asking other peer %d for correct TX\n", __func__,
-                      txid.ToString(), pnode->GetId());
-
-            CInv inv(MSG_TX, txid);
-            peerman.RequestObject(pnode->GetId(), inv, GetTime<std::chrono::microseconds>(), is_masternode,
-                                  /* fForce = */ true);
-        }
-    }
-    for (CNode* pnode : nodesToAskFor) {
-        pnode->Release();
-    }
-}
-
 void CInstantSendManager::ProcessPendingRetryLockTxs()
 {
     const auto retryTxs = WITH_LOCK(cs_pendingRetry, return pendingRetryTxs);

src/llmq/instantsend.h

@@ -199,7 +199,6 @@ class CInstantSendManager : public CRecoveredSigsListener
 
     CChainLocksHandler& clhandler;
     CChainState& m_chainstate;
-    CConnman& connman;
     CQuorumManager& qman;
     CSigningManager& sigman;
     CSigSharesManager& shareman;
@@ -254,13 +253,21 @@ class CInstantSendManager : public CRecoveredSigsListener
     std::unordered_set<uint256, StaticSaltedHasher> pendingRetryTxs GUARDED_BY(cs_pendingRetry);
 
 public:
-    explicit CInstantSendManager(CChainLocksHandler& _clhandler, CChainState& chainstate, CConnman& _connman,
-                                 CQuorumManager& _qman, CSigningManager& _sigman, CSigSharesManager& _shareman,
-                                 CSporkManager& sporkman, CTxMemPool& _mempool, const CMasternodeSync& mn_sync,
-                                 const std::unique_ptr<PeerManager>& peerman, bool is_masternode, bool unitTests, bool fWipe) :
+    explicit CInstantSendManager(CChainLocksHandler& _clhandler, CChainState& chainstate, CQuorumManager& _qman,
+                                 CSigningManager& _sigman, CSigSharesManager& _shareman, CSporkManager& sporkman,
+                                 CTxMemPool& _mempool, const CMasternodeSync& mn_sync,
+                                 const std::unique_ptr<PeerManager>& peerman, bool is_masternode, bool unitTests,
+                                 bool fWipe) :
         db(unitTests, fWipe),
-        clhandler(_clhandler), m_chainstate(chainstate), connman(_connman), qman(_qman), sigman(_sigman),
-        shareman(_shareman), spork_manager(sporkman), mempool(_mempool), m_mn_sync(mn_sync), m_peerman(peerman),
+        clhandler(_clhandler),
+        m_chainstate(chainstate),
+        qman(_qman),
+        sigman(_sigman),
+        shareman(_shareman),
+        spork_manager(sporkman),
+        mempool(_mempool),
+        m_mn_sync(mn_sync),
+        m_peerman(peerman),
         m_is_masternode{is_masternode}
     {
         workInterrupt.reset();
@@ -314,7 +321,6 @@ class CInstantSendManager : public CRecoveredSigsListener
         EXCLUSIVE_LOCKS_REQUIRED(!cs_inputReqests, !cs_nonLocked, !cs_pendingRetry);
     void ResolveBlockConflicts(const uint256& islockHash, const CInstantSendLock& islock)
         EXCLUSIVE_LOCKS_REQUIRED(!cs_inputReqests, !cs_nonLocked, !cs_pendingLocks, !cs_pendingRetry);
-    static void AskNodesForLockedTx(const uint256& txid, const CConnman& connman, PeerManager& peerman, bool is_masternode);
     void ProcessPendingRetryLockTxs()
         EXCLUSIVE_LOCKS_REQUIRED(!cs_creating, !cs_inputReqests, !cs_nonLocked, !cs_pendingRetry);
 

src/net_processing.cpp

@@ -619,7 +619,7 @@ class PeerManagerImpl final : public PeerManager
                        bool is_masternode, bool fForce = false) override EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
     size_t GetRequestedObjectCount(NodeId nodeid) const override EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
     bool IsInvInFilter(NodeId nodeid, const uint256& hash) const override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
-
+    void AskPeersForTransaction(const uint256& txid, bool is_masternode) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 private:
     /** Helpers to process result of external handlers of message */
     void ProcessPeerMsgRet(const PeerMsgRet& ret, CNode& pfrom) EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
@@ -634,6 +634,11 @@ class PeerManagerImpl final : public PeerManager
     /** Retrieve unbroadcast transactions from the mempool and reattempt sending to peers */
     void ReattemptInitialBroadcast(CScheduler& scheduler) EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
+    /**
+     * Private implementation of IsInvInFilter which does not call GetPeerRef; to be prefered when the PeerRef is available.
+     */
+    bool IsInvInFilter(const PeerRef& peer, const uint256& hash) const EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
+
     /** Get a shared pointer to the Peer object.
      *  May return an empty shared_ptr if the Peer object can't be found. */
     PeerRef GetPeerRef(NodeId id) const EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
@@ -2242,9 +2247,51 @@ void PeerManagerImpl::SendPings()
     for(auto& it : m_peer_map) it.second->m_ping_queued = true;
 }
 
+void PeerManagerImpl::AskPeersForTransaction(const uint256& txid, bool is_masternode)
+{
+    std::vector<PeerRef> peersToAsk;
+    peersToAsk.reserve(4);
+
+    auto maybe_add_to_nodesToAskFor = [&](const PeerRef& peer) {
+        if (peersToAsk.size() >= 4) {
+            return false;
+        }
+        if (IsInvInFilter(peer, txid)) {
+            peersToAsk.emplace_back(peer);
+        }
+        return true;
+    };
+
+    {
+        LOCK(m_peer_mutex);
+        // TODO consider prioritizing MNs again, once that flag is moved into Peer
+        for (const auto& [_, peer] : m_peer_map) {
+            if (!maybe_add_to_nodesToAskFor(peer)) {
+                break;
+            }
+        }
+    }
+    {
+        CInv inv(MSG_TX, txid);
+        LOCK(cs_main);
+        for (PeerRef& peer : peersToAsk) {
+            LogPrintf("PeerManagerImpl::%s -- txid=%s: asking other peer %d for correct TX\n", __func__,
+                      txid.ToString(), peer->m_id);
+
+            RequestObject(peer->m_id, inv, GetTime<std::chrono::microseconds>(), is_masternode,
+                          /*fForce=*/true);
+        }
+    }
+}
+
 bool PeerManagerImpl::IsInvInFilter(NodeId nodeid, const uint256& hash) const
 {
     PeerRef peer = GetPeerRef(nodeid);
+    return IsInvInFilter(peer, hash);
+}
+
+bool PeerManagerImpl::IsInvInFilter(const PeerRef& peer, const uint256& hash) const
+{
     if (peer == nullptr)
         return false;
     if (auto tx_relay = peer->GetTxRelay(); tx_relay != nullptr) {

src/net_processing.h

@@ -90,6 +90,9 @@ class PeerManager : public CValidationInterface, public NetEventsInterface
     /** Is an inventory in the known inventory filter. Used by InstantSend. */
     virtual bool IsInvInFilter(NodeId nodeid, const uint256& hash) const = 0;
 
+    /** Ask a number of our peers, which have a transaction in their inventory, for the transaction. */
+    virtual void AskPeersForTransaction(const uint256& txid, bool is_masternode) = 0;
+
     /** Broadcast inventory message to a specific peer. */
     virtual void PushInventory(NodeId nodeid, const CInv& inv) = 0;