net: Add CNode::ConnectedThroughNetwork member function

src/net.h

@@ -961,6 +961,18 @@ public:
         assert(false);
     }
 
+    /**
+     * Get network the peer connected through.
+     *
+     * Returns Network::NET_ONION for *inbound* onion connections,
+     * and CNetAddr::GetNetClass() otherwise. The latter cannot be used directly
+     * because it doesn't detect the former, and it's not the responsibility of
+     * the CNetAddr class to know the actual network a peer is connected through.
+     *
+     * @return network the peer connected through.
+     */
+    Network ConnectedThroughNetwork() const;
+
 protected:
     mapMsgCmdSize mapSendBytesPerMsgCmd;
     mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);