fix(dkg/net): Drop outdated connections to nodes that became masternodes recently (#4934)

* feat: switch nTimeFirstMessageReceived from microseconds to seconds

Was acting more like a bool until now, so nothing should change really. Align it with nTimeConnected.

* fix(dkg/net): Drop outdated connections to nodes that became masternodes recently

Such nodes won't be seen as masternodes by RelayInvToParticipants otherwise so no contributions will be sent to them when they are picked as relay members which in its turn may result in other nodes PoSe-punishing us.

src/net.cpp

@@ -2379,6 +2379,7 @@ void CConnman::ThreadOpenMasternodeConnections()
             return;
 
         int64_t nANow = GetAdjustedTime();
+        constexpr const auto &_func_ = __func__;
 
         // NOTE: Process only one pending masternode at a time
 
@@ -2405,6 +2406,22 @@ void CConnman::ThreadOpenMasternodeConnections()
                             continue;
                         }
                         const auto& addr2 = dmn->pdmnState->addr;
+                        if (connectedNodes.count(addr2) && !connectedProRegTxHashes.count(proRegTxHash)) {
+                            // we probably connected to it before it became a masternode
+                            // or maybe we are still waiting for mnauth
+                            (void)ForNode(addr2, [&](CNode* pnode) {
+                                if (pnode->nTimeFirstMessageReceived != 0 && GetSystemTimeInSeconds() - pnode->nTimeFirstMessageReceived > 5) {
+                                    // clearly not expecting mnauth to take that long even if it wasn't the first message
+                                    // we received (as it should normally), disconnect
+                                    LogPrint(BCLog::NET_NETCONN, "CConnman::%s -- dropping non-mnauth connection to %s, service=%s\n", _func_, proRegTxHash.ToString(), addr2.ToString(false));
+                                    pnode->fDisconnect = true;
+                                    return true;
+                                }
+                                return false;
+                            });
+                            // either way - it's not ready, skip it for now
+                            continue;
+                        }
                         if (!connectedNodes.count(addr2) && !IsMasternodeOrDisconnectRequested(addr2) && !connectedProRegTxHashes.count(proRegTxHash)) {
                             int64_t lastAttempt = mmetaman.GetMetaInfo(dmn->proTxHash)->GetLastOutboundAttempt();
                             // back off trying connecting to an address if we already tried recently

src/net_processing.cpp

@@ -2748,7 +2748,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& msg_type, CDataStrea
 
     if (pfrom->nTimeFirstMessageReceived == 0) {
         // First message after VERSION/VERACK
-        pfrom->nTimeFirstMessageReceived = GetTimeMicros();
+        pfrom->nTimeFirstMessageReceived = GetSystemTimeInSeconds();
         pfrom->fFirstMessageIsMNAUTH = msg_type == NetMsgType::MNAUTH;
         // Note: do not break the flow here