check congestion and random reject short tunnel build requests

libi2pd/TransitTunnel.cpp

@@ -188,7 +188,7 @@ namespace tunnel
 	}
 
 	TransitTunnels::TransitTunnels ():
-		m_IsRunning (false)
+		m_IsRunning (false), m_Rng(i2p::util::GetMonotonicMicroseconds ()%1000000LL)
 	{
 	}
 		
@@ -328,8 +328,25 @@ namespace tunnel
 				// check if we accept this tunnel
 				std::shared_ptr<i2p::tunnel::TransitTunnel> transitTunnel;
 				uint8_t retCode = 0;
-				if (!i2p::context.AcceptsTunnels () || i2p::context.GetCongestionLevel (false) >= CONGESTION_LEVEL_FULL)
+				if (i2p::context.AcceptsTunnels ())
+				{
+					auto congestionLevel = i2p::context.GetCongestionLevel (false);
+					if (congestionLevel < CONGESTION_LEVEL_FULL)
+					{	
+						if (congestionLevel >= CONGESTION_LEVEL_MEDIUM)
+						{	
+							// random reject depending on congestion level
+							int level = m_Rng () % (CONGESTION_LEVEL_FULL - CONGESTION_LEVEL_MEDIUM) + CONGESTION_LEVEL_MEDIUM;
+							if (congestionLevel > level)
+								retCode = 30;
+						}	
+					}	
+					else
+						retCode = 30;
+				}	
+				else	
 					retCode = 30;
+				
 				if (!retCode)
 				{
 					// create new transit tunnel
@@ -452,7 +469,7 @@ namespace tunnel
 						if (congestionLevel < CONGESTION_LEVEL_FULL)
 						{
 							// random reject depending on congestion level
-							int level = i2p::tunnel::tunnels.GetRng ()() % (CONGESTION_LEVEL_FULL - CONGESTION_LEVEL_MEDIUM) + CONGESTION_LEVEL_MEDIUM;
+							int level = m_Rng () % (CONGESTION_LEVEL_FULL - CONGESTION_LEVEL_MEDIUM) + CONGESTION_LEVEL_MEDIUM;
 							if (congestionLevel > level)
 								accept = false;
 						}	

libi2pd/TransitTunnel.h

@@ -152,6 +152,7 @@ namespace tunnel
 			std::unique_ptr<std::thread> m_Thread;
 			std::list<std::shared_ptr<TransitTunnel> > m_TransitTunnels;
 			i2p::util::Queue<std::shared_ptr<I2NPMessage> > m_TunnelBuildMsgQueue;
+			std::mt19937 m_Rng;
 			
 		public:
 

libi2pd/Tunnel.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2024, The PurpleI2P Project
+* Copyright (c) 2013-2025, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -246,8 +246,6 @@ namespace tunnel
 			uint32_t GetMaxNumTransitTunnels () const { return m_MaxNumTransitTunnels; };
 			int GetCongestionLevel() const { return m_MaxNumTransitTunnels ? CONGESTION_LEVEL_FULL * m_TransitTunnels.GetNumTransitTunnels () / m_MaxNumTransitTunnels : CONGESTION_LEVEL_FULL; }
 			
-			std::mt19937& GetRng () { return m_Rng; };
-			
 		private:
 
 			template<class TTunnel>