From 54ea2be8e0efd63d298600bb5f9374ae8d08dc1b Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Thu, 26 Mar 2026 21:09:41 -0400
Subject: [PATCH] don't select non-connected peer for first hop if too many
 connection from that subnet

---
 libi2pd/Transports.cpp | 52 ++++++++++++++++++++++++++++++------------
 libi2pd/Transports.h   |  3 +++
 libi2pd/TunnelPool.cpp |  3 ++-
 3 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/libi2pd/Transports.cpp b/libi2pd/Transports.cpp
index 49176a93..40bd8446 100644
--- a/libi2pd/Transports.cpp
+++ b/libi2pd/Transports.cpp
@@ -1405,31 +1405,53 @@ namespace transport
 		return m_BanList.emplace (addr, ts).second;
 	}
 
-	boost::asio::ip::address Transports::GetNetworkAddress (std::shared_ptr<TransportSession> session) const
+	boost::asio::ip::address Transports::GetNetworkAddress (const boost::asio::ip::address& addr) const
 	{
-		if (session)
+		if (!addr.is_unspecified ())
 		{
-			auto networkAddr = session->GetRemoteAddress ();
-			if (!networkAddr.is_unspecified ())
+			if (addr.is_v4 ())
+				return boost::asio::ip::network_v4 (addr.to_v4 (), 24).network (); // /24
+			else
 			{
-				if (networkAddr.is_v4 ())
-					return boost::asio::ip::network_v4 (networkAddr.to_v4 (), 24).network (); // /24
-				else
+				if (i2p::util::net::IsYggdrasilAddress (addr))
 				{
-					if (i2p::util::net::IsYggdrasilAddress (networkAddr))
-					{
-						// change to 2xx range
-						auto bytes = networkAddr.to_v6 ().to_bytes ();
-						bytes[0] = 0x02;
-						return  boost::asio::ip::network_v6 (boost::asio::ip::address_v6 (bytes), 64).network (); // /64
-					}
-					return boost::asio::ip::network_v6 (networkAddr.to_v6 (), 56).network (); // /56
+					// change to 2xx range
+					auto bytes = addr.to_v6 ().to_bytes ();
+					bytes[0] = 0x02;
+					return  boost::asio::ip::network_v6 (boost::asio::ip::address_v6 (bytes), 64).network (); // /64
 				}
+				return boost::asio::ip::network_v6 (addr.to_v6 (), 56).network (); // /56
 			}
 		}
 		return boost::asio::ip::address ();
 	}
 
+	boost::asio::ip::address Transports::GetNetworkAddress (std::shared_ptr<TransportSession> session) const
+	{
+		if (session)
+			return GetNetworkAddress (session->GetRemoteAddress ());
+		return boost::asio::ip::address ();
+	}
+
+	bool Transports::IsTooManyConnectionsFromSubnet (std::shared_ptr<const i2p::data::RouterInfo> r) const
+	{
+		if (!r && !IsCheckReserved ()) return false;
+		auto addresses = r->GetAddresses ();
+		if (!addresses) return false;
+		for (auto& address : *addresses)
+			if (address && !address->host.is_unspecified ())
+			{
+				auto networkAddr = GetNetworkAddress (address->host);
+				if (!networkAddr.is_unspecified ())
+				{
+					std::lock_guard<std::mutex> l( m_ConnectedNetworksMutex);
+					auto it = m_ConnectedNetworks.find (networkAddr);
+					if (it != m_ConnectedNetworks.end () && it->second > MAX_NUM_CONNECTIONS_FROM_SUBNET_FOR_PEER) return true;
+				}
+			}
+		return false;
+	}
+
 	void InitAddressFromIface ()
 	{
 		bool ipv6; i2p::config::GetOption("ipv6", ipv6);
diff --git a/libi2pd/Transports.h b/libi2pd/Transports.h
index 5aab25d8..90cca0c6 100644
--- a/libi2pd/Transports.h
+++ b/libi2pd/Transports.h
@@ -199,6 +199,8 @@ namespace transport
 			bool IsBanned (const boost::asio::ip::address& addr);
 			bool AddBan (const boost::asio::ip::address& addr);
 
+			bool IsTooManyConnectionsFromSubnet (std::shared_ptr<const i2p::data::RouterInfo> r) const;
+
 		private:
 
 			void Run ();
@@ -218,6 +220,7 @@ namespace transport
 			template<typename Filter>
 				std::shared_ptr<const i2p::data::RouterInfo> GetRandomPeer (Filter filter) const;
 			boost::asio::ip::address GetNetworkAddress (std::shared_ptr<TransportSession> session) const;
+			boost::asio::ip::address GetNetworkAddress (const boost::asio::ip::address& addr) const;
 
 		private:
 
diff --git a/libi2pd/TunnelPool.cpp b/libi2pd/TunnelPool.cpp
index f8a1f3a7..e9e71ca4 100644
--- a/libi2pd/TunnelPool.cpp
+++ b/libi2pd/TunnelPool.cpp
@@ -578,7 +578,8 @@ namespace tunnel
 				i2p::data::netdb.GetRandomRouter (prevHop, reverse, endpoint, false);
 			if (hop)
 			{
-				if (!hop->HasProfile () || !hop->GetProfile ()->IsBad ())
+				if ((!hop->HasProfile () || !hop->GetProfile ()->IsBad ()) &&
+					(prevHop != i2p::context.GetSharedRouterInfo () || !i2p::transport::transports.IsTooManyConnectionsFromSubnet (hop)))
 					break;
 			}
 			else if (tryClient)