check if router if real only if tunnel build rate is low and router's profile is presented when handle exploratory request

libi2pd/NetDb.cpp

@@ -991,7 +991,7 @@ namespace data
 		auto dest = m_Requests.FindRequest (ident);
 		if (dest)
 		{
-			if (num > 0)
+			if (num > 0 || dest->GetNumExcludedPeers () < 3) // before 3-rd attempt might be just bad luck
 				// try to send next requests
 				m_Requests.SendNextRequest (dest);
 			else
@@ -1451,9 +1451,11 @@ namespace data
 		IdentHash destKey = CreateRoutingKey (destination);
 		minMetric.SetMax ();
 		// must be called from NetDb thread only
+		bool checkIsReal = i2p::tunnel::tunnels.GetPreciseTunnelCreationSuccessRate () < NETDB_TUNNEL_CREATION_RATE_THRESHOLD; // too low rate
+		std::lock_guard<std::mutex> l(m_RouterInfosMutex);
 		for (const auto& it: m_RouterInfos)
 		{
-			if (!it.second->IsDeclaredFloodfill () && it.second->GetProfile ()->IsReal ())
+			if (!it.second->IsDeclaredFloodfill () && (!checkIsReal || (it.second->HasProfile () && it.second->GetProfile ()->IsReal ())))
 			{
 				XORMetric m = destKey ^ it.first;
 				if (m < minMetric && !excluded.count (it.first))

libi2pd/RouterInfo.h

@@ -280,6 +280,7 @@ namespace data
 
 			std::shared_ptr<RouterProfile> GetProfile () const;
 			void DropProfile () { m_Profile = nullptr; };
+			bool HasProfile () const { return (bool)m_Profile; }; 
 
 			bool Update (const uint8_t * buf, size_t len);
 			void DeleteBuffer () { m_Buffer = nullptr; };