Factor feefilter logic out

Break SendMessages() function into smaller units to improve readability.
Adds lock assert, as `round()` isn't thread safe.
closes #21545

Author: amadeuszpawlik

src/net_processing.cpp

@@ -331,6 +331,9 @@ class PeerManagerImpl final : public PeerManager
     /** Send `addr` messages on a regular schedule. */
     void MaybeSendAddr(CNode& node, std::chrono::microseconds current_time);
 
+    /** Send `feefilter` message. */
+    void MaybeSendFeefilter(CNode& node, std::chrono::microseconds current_time) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
     const CChainParams& m_chainparams;
     CConnman& m_connman;
     CAddrMan& m_addrman;
@@ -4219,6 +4222,49 @@ void PeerManagerImpl::MaybeSendAddr(CNode& node, std::chrono::microseconds curre
     }
 }
 
+void PeerManagerImpl::MaybeSendFeefilter(CNode& pto, std::chrono::microseconds current_time)
+{
+    AssertLockHeld(cs_main);
+
+    if (m_ignore_incoming_txs) return;
+    if (!pto.m_tx_relay) return;
+    if (pto.GetCommonVersion() < FEEFILTER_VERSION) return;
+    // peers with the forcerelay permission should not filter txs to us
+    if (pto.HasPermission(NetPermissionFlags::ForceRelay)) return;
+
+    CAmount currentFilter = m_mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
+    static FeeFilterRounder g_filter_rounder{CFeeRate{DEFAULT_MIN_RELAY_TX_FEE}};
+
+    if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
+        // Received tx-inv messages are discarded when the active
+        // chainstate is in IBD, so tell the peer to not send them.
+        currentFilter = MAX_MONEY;
+    } else {
+        static const CAmount MAX_FILTER{g_filter_rounder.round(MAX_MONEY)};
+        if (pto.m_tx_relay->lastSentFeeFilter == MAX_FILTER) {
+            // Send the current filter if we sent MAX_FILTER previously
+            // and made it out of IBD.
+            pto.m_tx_relay->m_next_send_feefilter = 0us;
+        }
+    }
+    if (current_time > pto.m_tx_relay->m_next_send_feefilter) {
+        CAmount filterToSend = g_filter_rounder.round(currentFilter);
+        // We always have a fee filter of at least minRelayTxFee
+        filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
+        if (filterToSend != pto.m_tx_relay->lastSentFeeFilter) {
+            m_connman.PushMessage(&pto, CNetMsgMaker(pto.GetCommonVersion()).Make(NetMsgType::FEEFILTER, filterToSend));
+            pto.m_tx_relay->lastSentFeeFilter = filterToSend;
+        }
+        pto.m_tx_relay->m_next_send_feefilter = PoissonNextSend(current_time, AVG_FEEFILTER_BROADCAST_INTERVAL);
+    }
+    // If the fee filter has changed substantially and it's still more than MAX_FEEFILTER_CHANGE_DELAY
+    // until scheduled broadcast, then move the broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
+    else if (current_time + MAX_FEEFILTER_CHANGE_DELAY < pto.m_tx_relay->m_next_send_feefilter &&
+                (currentFilter < 3 * pto.m_tx_relay->lastSentFeeFilter / 4 || currentFilter > 4 * pto.m_tx_relay->lastSentFeeFilter / 3)) {
+        pto.m_tx_relay->m_next_send_feefilter = current_time + GetRandomDuration<std::chrono::microseconds>(MAX_FEEFILTER_CHANGE_DELAY);
+    }
+}
+
 namespace {
 class CompareInvMempoolOrder
 {
@@ -4705,45 +4751,7 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
         if (!vGetData.empty())
             m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
 
-        //
-        // Message: feefilter
-        //
-        if (pto->m_tx_relay != nullptr &&
-            !m_ignore_incoming_txs &&
-            pto->GetCommonVersion() >= FEEFILTER_VERSION &&
-            !pto->HasPermission(NetPermissionFlags::ForceRelay) // peers with the forcerelay permission should not filter txs to us
-        ) {
-            CAmount currentFilter = m_mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
-            static FeeFilterRounder g_filter_rounder{CFeeRate{DEFAULT_MIN_RELAY_TX_FEE}};
-            if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
-                // Received tx-inv messages are discarded when the active
-                // chainstate is in IBD, so tell the peer to not send them.
-                currentFilter = MAX_MONEY;
-            } else {
-                static const CAmount MAX_FILTER{g_filter_rounder.round(MAX_MONEY)};
-                if (pto->m_tx_relay->lastSentFeeFilter == MAX_FILTER) {
-                    // Send the current filter if we sent MAX_FILTER previously
-                    // and made it out of IBD.
-                    pto->m_tx_relay->m_next_send_feefilter = 0us;
-                }
-            }
-            if (current_time > pto->m_tx_relay->m_next_send_feefilter) {
-                CAmount filterToSend = g_filter_rounder.round(currentFilter);
-                // We always have a fee filter of at least minRelayTxFee
-                filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
-                if (filterToSend != pto->m_tx_relay->lastSentFeeFilter) {
-                    m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
-                    pto->m_tx_relay->lastSentFeeFilter = filterToSend;
-                }
-                pto->m_tx_relay->m_next_send_feefilter = PoissonNextSend(current_time, AVG_FEEFILTER_BROADCAST_INTERVAL);
-            }
-            // If the fee filter has changed substantially and it's still more than MAX_FEEFILTER_CHANGE_DELAY
-            // until scheduled broadcast, then move the broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
-            else if (current_time + MAX_FEEFILTER_CHANGE_DELAY < pto->m_tx_relay->m_next_send_feefilter &&
-                     (currentFilter < 3 * pto->m_tx_relay->lastSentFeeFilter / 4 || currentFilter > 4 * pto->m_tx_relay->lastSentFeeFilter / 3)) {
-                pto->m_tx_relay->m_next_send_feefilter = current_time + GetRandomDuration<std::chrono::microseconds>(MAX_FEEFILTER_CHANGE_DELAY);
-            }
-        }
+        MaybeSendFeefilter(*pto, current_time);
     } // release cs_main
     return true;
 }