[net] Encapsulate CNode message polling

Author: dergoegge

src/net.cpp

@@ -2812,6 +2812,20 @@ void CNode::MarkReceivedMsgsForProcessing(unsigned int recv_flood_size)
     fPauseRecv = nProcessQueueSize > recv_flood_size;
 }
 
+std::optional<std::pair<CNetMessage, bool>> CNode::PollMessage(size_t recv_flood_size)
+{
+    LOCK(cs_vProcessMsg);
+    if (vProcessMsg.empty()) return std::nullopt;
+
+    std::list<CNetMessage> msgs;
+    // Just take one message
+    msgs.splice(msgs.begin(), vProcessMsg, vProcessMsg.begin());
+    nProcessQueueSize -= msgs.front().m_raw_message_size;
+    fPauseRecv = nProcessQueueSize > recv_flood_size;
+
+    return std::make_pair(std::move(msgs.front()), !vProcessMsg.empty());
+}
+
 bool CConnman::NodeFullyConnected(const CNode* pnode)
 {
     return pnode && pnode->fSuccessfullyConnected && !pnode->fDisconnect;

src/net.h

@@ -426,6 +426,14 @@ class CNode
     void MarkReceivedMsgsForProcessing(unsigned int recv_flood_size)
         EXCLUSIVE_LOCKS_REQUIRED(!cs_vProcessMsg);
 
+    /** Poll the next message from the processing queue of this connection.
+     *
+     * Returns std::nullopt if the processing queue is empty, or a pair
+     * consisting of the message and a bool that indicates if the processing
+     * queue has more entries. */
+    std::optional<std::pair<CNetMessage, bool>> PollMessage(size_t recv_flood_size)
+        EXCLUSIVE_LOCKS_REQUIRED(!cs_vProcessMsg);
+
     bool IsOutboundOrBlockRelayConn() const {
         switch (m_conn_type) {
             case ConnectionType::OUTBOUND_FULL_RELAY:

src/net_processing.cpp

@@ -4854,8 +4854,6 @@ bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt
 {
     AssertLockHeld(g_msgproc_mutex);
 
-    bool fMoreWork = false;
-
     PeerRef peer = GetPeerRef(pfrom->GetId());
     if (peer == nullptr) return false;
 
@@ -4883,17 +4881,14 @@ bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt
     // Don't bother if send buffer is too full to respond anyway
     if (pfrom->fPauseSend) return false;
 
-    std::list<CNetMessage> msgs;
-    {
-        LOCK(pfrom->cs_vProcessMsg);
-        if (pfrom->vProcessMsg.empty()) return false;
-        // Just take one message
-        msgs.splice(msgs.begin(), pfrom->vProcessMsg, pfrom->vProcessMsg.begin());
-        pfrom->nProcessQueueSize -= msgs.front().m_raw_message_size;
-        pfrom->fPauseRecv = pfrom->nProcessQueueSize > m_connman.GetReceiveFloodSize();
-        fMoreWork = !pfrom->vProcessMsg.empty();
-    }
-    CNetMessage& msg(msgs.front());
+    auto poll_result{pfrom->PollMessage(m_connman.GetReceiveFloodSize())};
+    if (!poll_result) {
+        // No message to process
+        return false;
+    }
+
+    CNetMessage& msg{poll_result->first};
+    bool fMoreWork = poll_result->second;
 
     TRACE6(net, inbound_message,
         pfrom->GetId(),