publish and request through exploratory tunnel if floodfill is not reachable

libi2pd/I2NPProtocol.cpp

@@ -244,7 +244,8 @@ namespace i2p
 		return m;
 	}
 
-	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::RouterInfo> router, uint32_t replyToken)
+	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::RouterInfo> router, 
+		uint32_t replyToken, std::shared_ptr<const i2p::tunnel::InboundTunnel> replyTunnel)
 	{
 		if (!router) // we send own RouterInfo
 			router = context.GetSharedRouterInfo ();
@@ -258,10 +259,20 @@ namespace i2p
 		uint8_t * buf = payload + DATABASE_STORE_HEADER_SIZE;
 		if (replyToken)
 		{
-			memset (buf, 0, 4); // zero tunnelID means direct reply
-			buf += 4;
-			memcpy (buf, router->GetIdentHash (), 32);
-			buf += 32;
+			if (replyTunnel)
+			{
+				htobe32buf (buf, replyTunnel->GetNextTunnelID ());
+				buf += 4; // reply tunnelID
+				memcpy (buf, replyTunnel->GetNextIdentHash (), 32);
+				buf += 32; // reply tunnel gateway
+			}
+			else
+			{	
+				memset (buf, 0, 4); // zero tunnelID means direct reply
+				buf += 4;
+				memcpy (buf, context.GetIdentHash (), 32);
+				buf += 32;
+			}	
 		}
 
 		uint8_t * sizePtr = buf;

libi2pd/I2NPProtocol.h

@@ -276,7 +276,7 @@ namespace tunnel
 	    const uint8_t * replyKey, const uint8_t * replyTag, bool replyECIES = false);
 	std::shared_ptr<I2NPMessage> CreateDatabaseSearchReply (const i2p::data::IdentHash& ident, std::vector<i2p::data::IdentHash> routers);
 
-	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::RouterInfo> router = nullptr, uint32_t replyToken = 0);
+	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::RouterInfo> router = nullptr, uint32_t replyToken = 0, std::shared_ptr<const i2p::tunnel::InboundTunnel> replyTunnel = nullptr);
 	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (const i2p::data::IdentHash& storeHash, std::shared_ptr<const i2p::data::LeaseSet> leaseSet); // for floodfill only
 	std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::LocalLeaseSet> leaseSet, uint32_t replyToken = 0, std::shared_ptr<const i2p::tunnel::InboundTunnel> replyTunnel = nullptr);
 	bool IsRouterInfoMsg (std::shared_ptr<I2NPMessage> msg);

libi2pd/NetDb.cpp

@@ -643,6 +643,7 @@ namespace data
 		auto floodfill = GetClosestFloodfill (destination, dest->GetExcludedPeers ());
 		if (floodfill)
 		{
+			if (direct && !floodfill->IsCompatible (i2p::context.GetRouterInfo ())) direct = false; // check if fllodfill is reachable
 			if (direct)
 				transports.SendMessage (floodfill->GetIdentHash (), dest->CreateRequestMessage (floodfill->GetIdentHash ()));
 			else
@@ -1087,7 +1088,19 @@ namespace data
 			LogPrint (eLogInfo, "NetDb: Publishing our RouterInfo to ", i2p::data::GetIdentHashAbbreviation(floodfill->GetIdentHash ()), ". reply token=", replyToken);
 			m_PublishExcluded.insert (floodfill->GetIdentHash ());
 			m_PublishReplyToken = replyToken;
-			transports.SendMessage (floodfill->GetIdentHash (), CreateDatabaseStoreMsg (i2p::context.GetSharedRouterInfo (), replyToken));
+			if (floodfill->IsCompatible (i2p::context.GetRouterInfo ())) // able to connect?
+				// send directly
+				transports.SendMessage (floodfill->GetIdentHash (), CreateDatabaseStoreMsg (i2p::context.GetSharedRouterInfo (), replyToken));
+			else
+			{
+				// otherwise through exploratory	
+				auto exploratoryPool = i2p::tunnel::tunnels.GetExploratoryPool ();
+				auto outbound = exploratoryPool ? exploratoryPool->GetNextOutboundTunnel () : nullptr;
+				auto inbound = exploratoryPool ? exploratoryPool->GetNextInboundTunnel () : nullptr;	
+				if (inbound && outbound)
+					outbound->SendTunnelDataMsg (floodfill->GetIdentHash (), 0, 
+						CreateDatabaseStoreMsg (i2p::context.GetSharedRouterInfo (), replyToken, inbound));	
+			}		
 		}
 	}