From b0543dfe32fd1b5bd2bf89597254b406def02593 Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Wed, 4 Feb 2026 14:36:46 -0500
Subject: [PATCH] let few first tunnel build messages go through before drop

---
 libi2pd/I2NPProtocol.cpp | 19 ++++++++++++++++---
 libi2pd/I2NPProtocol.h   |  8 ++++++--
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/libi2pd/I2NPProtocol.cpp b/libi2pd/I2NPProtocol.cpp
index 045fad8d..822a136a 100644
--- a/libi2pd/I2NPProtocol.cpp
+++ b/libi2pd/I2NPProtocol.cpp
@@ -557,9 +557,13 @@ namespace i2p
 				case eI2NPShortTunnelBuild:
 				{
 					auto ts = i2p::util::GetMonotonicMilliseconds ();
-					if (!m_LastTunnelBuildMessageTimestamp || ts > m_LastTunnelBuildMessageTimestamp + TUNNEL_BUILD_MESSAGES_MIN_INTERVAL)
+					if (!m_LastTunnelBuildMessageTimestamp ||
+						ts > m_LastTunnelBuildMessageTimestamp + TUNNEL_BUILD_MESSAGES_MAX_INTERVAL ||
+						ts > m_LastTunnelBuildMessageTimestamp + TUNNEL_BUILD_MESSAGES_MIN_INTERVAL +
+							m_NumThrottledTunnelBuildMessages*TUNNEL_BUILD_MESSAGES_EXTRA_INTERVAL_PER_MESSAGE)
 					{
 						m_LastTunnelBuildMessageTimestamp = ts;
+						m_NumThrottledTunnelBuildMessages = 0;
 						if (m_NumDroppedTunnelBuildMessages > 0)
 						{
 							LogPrint (eLogWarning, "I2NP: ", m_NumDroppedTunnelBuildMessages, " tunnel build messages dropped");
@@ -567,8 +571,17 @@ namespace i2p
 						}
 						HandleI2NPMessage (msg);
 					}
-					else // drop TBM
-						m_NumDroppedTunnelBuildMessages++;
+					else
+					{
+						if (m_NumThrottledTunnelBuildMessages < MAX_NUM_THROTTLED_TUNNEL_BUILD_MESSAGES)
+						{
+							// let TBM go through
+							m_NumThrottledTunnelBuildMessages++;
+							HandleI2NPMessage (msg);
+						}
+						else // drop TBM
+							m_NumDroppedTunnelBuildMessages++;
+					}
 					break;
 				}
 				default:
diff --git a/libi2pd/I2NPProtocol.h b/libi2pd/I2NPProtocol.h
index bef65267..fe358b6f 100644
--- a/libi2pd/I2NPProtocol.h
+++ b/libi2pd/I2NPProtocol.h
@@ -320,11 +320,15 @@ namespace tunnel
 	void HandleI2NPMessage (std::shared_ptr<I2NPMessage> msg);
 
 	const uint64_t TUNNEL_BUILD_MESSAGES_MIN_INTERVAL = 200; // in milliseconds
+	const uint64_t TUNNEL_BUILD_MESSAGES_MAX_INTERVAL = 3000; // in milliseconds
+	const uint64_t TUNNEL_BUILD_MESSAGES_EXTRA_INTERVAL_PER_MESSAGE = 50; // in milliseconds
+	const int MAX_NUM_THROTTLED_TUNNEL_BUILD_MESSAGES = 5;
 	class I2NPMessagesHandler
 	{
 		public:
 
-			I2NPMessagesHandler (): m_LastTunnelBuildMessageTimestamp (0), m_NumDroppedTunnelBuildMessages (0) {};
+			I2NPMessagesHandler (): m_LastTunnelBuildMessageTimestamp (0),
+				m_NumThrottledTunnelBuildMessages (0), m_NumDroppedTunnelBuildMessages (0) {};
 			~I2NPMessagesHandler ();
 			void PutNextMessage (std::shared_ptr<I2NPMessage>&& msg);
 			void Flush ();
@@ -333,7 +337,7 @@ namespace tunnel
 
 			std::list<std::shared_ptr<I2NPMessage> > m_TunnelMsgs, m_TunnelGatewayMsgs;
 			uint64_t m_LastTunnelBuildMessageTimestamp; // in milliseconds
-			int m_NumDroppedTunnelBuildMessages;
+			int m_NumThrottledTunnelBuildMessages, m_NumDroppedTunnelBuildMessages;
 	};
 }