[net/refactor] Rework ThreadOpenConnections logic

Make the connection counts explicit and extract into interface functions around
m_conn_type. Using explicit counting and switch statements where possible
should help prevent counting bugs in the future.

src/net.cpp

@@ -1829,21 +1829,27 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
         int nOutboundFullRelay = 0;
         int nOutboundBlockRelay = 0;
         std::set<std::vector<unsigned char> > setConnected;
+
         {
             LOCK(cs_vNodes);
             for (const CNode* pnode : vNodes) {
-                if (!pnode->IsInboundConn() && (pnode->m_conn_type != ConnectionType::MANUAL)) {
-                    // Netgroups for inbound and addnode peers are not excluded because our goal here
-                    // is to not use multiple of our limited outbound slots on a single netgroup
-                    // but inbound and addnode peers do not use our outbound slots.  Inbound peers
-                    // also have the added issue that they're attacker controlled and could be used
-                    // to prevent us from connecting to particular hosts if we used them here.
-                    setConnected.insert(pnode->addr.GetGroup(addrman.m_asmap));
-                    if (pnode->m_tx_relay == nullptr) {
-                        nOutboundBlockRelay++;
-                    } else if (pnode->m_conn_type == ConnectionType::OUTBOUND) {
-                        nOutboundFullRelay++;
-                    }
+                if (pnode->IsFullOutboundConn()) nOutboundFullRelay++;
+                if (pnode->IsBlockOnlyConn()) nOutboundBlockRelay++;
+
+                // Netgroups for inbound and manual peers are not excluded because our goal here
+                // is to not use multiple of our limited outbound slots on a single netgroup
+                // but inbound and manual peers do not use our outbound slots. Inbound peers
+                // also have the added issue that they could be attacker controlled and used
+                // to prevent us from connecting to particular hosts if we used them here.
+                switch(pnode->m_conn_type){
+                    case ConnectionType::INBOUND:
+                    case ConnectionType::MANUAL:
+                        break;
+                    case ConnectionType::OUTBOUND:
+                    case ConnectionType::BLOCK_RELAY:
+                    case ConnectionType::ADDR_FETCH:
+                    case ConnectionType::FEELER:
+                        setConnected.insert(pnode->addr.GetGroup(addrman.m_asmap));
                 }
             }
         }

src/net.h

@@ -789,10 +789,18 @@ public:
     std::atomic_bool fPauseRecv{false};
     std::atomic_bool fPauseSend{false};
 
+    bool IsFullOutboundConn() const {
+        return m_conn_type == ConnectionType::OUTBOUND;
+    }
+
     bool IsManualConn() const {
         return m_conn_type == ConnectionType::MANUAL;
     }
 
+    bool IsBlockOnlyConn() const {
+        return m_conn_type == ConnectionType::BLOCK_RELAY;
+    }
+
     bool IsFeelerConn() const {
         return m_conn_type == ConnectionType::FEELER;
     }
@@ -805,6 +813,21 @@ public:
         return m_conn_type == ConnectionType::INBOUND;
     }
 
+    bool ExpectServicesFromConn() const {
+        switch(m_conn_type) {
+            case ConnectionType::INBOUND:
+            case ConnectionType::MANUAL:
+            case ConnectionType::FEELER:
+                return false;
+            case ConnectionType::OUTBOUND:
+            case ConnectionType::BLOCK_RELAY:
+            case ConnectionType::ADDR_FETCH:
+                return true;
+        }
+
+        assert(false);
+    }
+
 protected:
     mapMsgCmdSize mapSendBytesPerMsgCmd;
     mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);