create new list of SSU2 introducers

libi2pd/NetDb.cpp

@@ -1233,6 +1233,16 @@ namespace data
 			});
 	}
 
+	std::shared_ptr<const RouterInfo> NetDb::GetRandomSSU2Introducer (bool v4, const std::set<IdentHash>& excluded) const
+	{
+		return GetRandomRouter (
+			[v4, &excluded](std::shared_ptr<const RouterInfo> router)->bool
+			{
+				return !router->IsHidden () && router->IsSSU2Introducer (v4) && 
+					!excluded.count (router->GetIdentHash ());
+			});
+	}
+	
 	std::shared_ptr<const RouterInfo> NetDb::GetHighBandwidthRandomRouter (std::shared_ptr<const RouterInfo> compatibleWith, bool reverse) const
 	{
 		return GetRandomRouter (

libi2pd/NetDb.hpp

@@ -93,6 +93,7 @@ namespace data
 			std::shared_ptr<const RouterInfo> GetRandomSSU2PeerTestRouter (bool v4, const std::set<IdentHash>& excluded) const;
 			std::shared_ptr<const RouterInfo> GetRandomSSUV6Router () const; // TODO: change to v6 peer test later
 			std::shared_ptr<const RouterInfo> GetRandomIntroducer (bool v4, const std::set<IdentHash>& excluded) const;
+			std::shared_ptr<const RouterInfo> GetRandomSSU2Introducer (bool v4, const std::set<IdentHash>& excluded) const;
 			std::shared_ptr<const RouterInfo> GetClosestFloodfill (const IdentHash& destination, const std::set<IdentHash>& excluded, bool closeThanUsOnly = false) const;
 			std::vector<IdentHash> GetClosestFloodfills (const IdentHash& destination, size_t num,
 				std::set<IdentHash>& excluded, bool closeThanUsOnly = false) const;

libi2pd/RouterInfo.cpp

@@ -1065,6 +1065,17 @@ namespace data
 			});
 	}
 
+	bool RouterInfo::IsSSU2Introducer (bool v4) const
+	{
+		if (!(m_SupportedTransports & (v4 ? eSSU2V4 : eSSU2V6))) return false;
+		return (bool)GetAddress (
+			[v4](std::shared_ptr<const RouterInfo::Address> address)->bool
+			{
+				return (address->IsSSU2 ()) && address->IsIntroducer () &&
+					((v4 && address->IsV4 ()) || (!v4 && address->IsV6 ())) && !address->host.is_unspecified ();
+			});
+	}
+		
 	void RouterInfo::SetUnreachableAddressesTransportCaps (uint8_t transports)
 	{
 		for (auto& addr: *m_Addresses)

libi2pd/RouterInfo.h

@@ -235,6 +235,7 @@ namespace data
 			bool IsPeerTesting (bool v4) const;
 			bool IsSSU2PeerTesting (bool v4) const;
 			bool IsIntroducer (bool v4) const;
+			bool IsSSU2Introducer (bool v4) const;
 
 			uint8_t GetCaps () const { return m_Caps; };
 			void SetCaps (uint8_t caps) { m_Caps = caps; };

libi2pd/SSU2.cpp

@@ -755,28 +755,68 @@ namespace transport
 
 	void SSU2Server::UpdateIntroducers (bool v4)
 	{
+		uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
 		std::list<std::shared_ptr<SSU2Session>> newList;
 		auto& introducers = v4 ? m_Introducers : m_IntroducersV6;
+		std::set<i2p::data::IdentHash> excluded;
 		for (const auto& it : introducers)
 		{
 			if (it->IsEstablished ())
 			{
+				if (ts < it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION)
 					it->SendKeepAlive ();
+				if (ts < it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION)
+				{	
 					newList.push_back (it);
+					excluded.insert (it->GetRemoteIdentity ()->GetIdentHash ());
+				}	
+				// TODO: remove introducer
 			}	
 		}	
 		if (newList.size () < SSU2_MAX_NUM_INTRODUCERS)
 		{
-			std::set<i2p::data::IdentHash> excluded;
-			for (auto& it1: newList)
-				excluded.insert (it1->GetRemoteIdentity ()->GetIdentHash ());
-			auto sessions = FindIntroducers (SSU_MAX_NUM_INTRODUCERS - newList.size (), v4, excluded);
+			auto sessions = FindIntroducers (SSU2_MAX_NUM_INTRODUCERS - newList.size (), v4, excluded);
+			if (sessions.empty () && !introducers.empty ())
+			{
+				// bump creation time for previous introducers if no new sessions found
+				LogPrint (eLogDebug, "SSU2: No new introducers found. Trying to reuse existing");
+				for (auto& it : introducers)
+					it->SetCreationTime (it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION);
+				// try again
+				excluded.clear ();
+				sessions = FindIntroducers (SSU2_MAX_NUM_INTRODUCERS - newList.size (), v4, excluded);
+			}	
+						
 			for (const auto& it : sessions)
 			{
+				// TODO: add introducer
 				newList.push_back (it);
+				if (newList.size () >= SSU2_MAX_NUM_INTRODUCERS) break;
 			}	
 		}	
 		introducers = newList;
+
+		if (introducers.size () < SSU2_MAX_NUM_INTRODUCERS)
+		{
+			for (auto i = introducers.size (); i < SSU2_MAX_NUM_INTRODUCERS; i++)
+			{
+				auto introducer = i2p::data::netdb.GetRandomSSU2Introducer (v4, excluded);
+				if (introducer)
+				{
+					auto address = v4 ? introducer->GetSSU2V4Address () : introducer->GetSSU2V6Address ();
+					if (address)
+					{
+						CreateSession (introducer, address);
+						excluded.insert (introducer->GetIdentHash ());
+					}
+				}
+				else
+				{
+					LogPrint (eLogDebug, "SSU2: Can't find more introducers");
+					break;
+				}
+			}
+		}
 	}	
 }
 }