net: require a verack before responding to anything else

theuni · furszy · commit 475b1c64bb10 · 2021-11-22T10:31:25.000-03:00
7a8c251 made this logic hard to follow. After that change, messages would not be sent to a peer via SendMessages() before the handshake was complete, but messages could still be sent as a response to an incoming message. For example, if a peer had not yet sent a verack, we wouldn't notify it about new blocks, but we would respond to a PING with a PONG. This change makes the behavior straightforward: until we've received a verack, never send any message other than version/verack/reject. The behavior until a VERACK is received has always been undefined, this change just tightens our policy. This also makes testing much easier, because we can now connect but not send version/verack, and anything sent to us is an error.
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
@@ -1290,6 +1290,14 @@ bool static ProcessMessage(CNode* pfrom, std::string strCommand, CDataStream& vR
                   (fLogIPs ? strprintf(", peeraddr=%s", pfrom->addr.ToString()) : ""));
     }
 
+    else if (!pfrom->fSuccessfullyConnected)
+    {
+        // Must have a verack message before anything else
+        LOCK(cs_main);
+        Misbehaving(pfrom->GetId(), 1);
+        return false;
+    }
+
 
     else if (strCommand == NetMsgType::ADDR || strCommand == NetMsgType::ADDRV2) {
         int stream_version = vRecv.GetVersion();
