handle exploratory lookups

NetDb.cpp

@@ -649,6 +649,7 @@ namespace data
 		key[l] = 0;
 		uint8_t flag = buf[64];
 		LogPrint ("DatabaseLookup for ", key, " recieved flags=", (int)flag);
+		uint8_t lookupType = flag & DATABASE_LOOKUP_TYPE_FLAGS_MASK;
 		uint8_t * excluded = buf + 65;		
 		uint32_t replyTunnelID = 0;
 		if (flag & DATABASE_LOOKUP_DELIVERY_FLAG) //reply to tunnel
@@ -665,7 +666,29 @@ namespace data
 		} 
 		
 		I2NPMessage * replyMsg = nullptr;
-
+		if (lookupType == DATABASE_LOOKUP_TYPE_EXPLORATORY_LOOKUP)
+		{
+			LogPrint ("Exploratory close to  ", key, " ", numExcluded, " excluded");
+			std::set<IdentHash> excludedRouters;
+			for (int i = 0; i < numExcluded; i++)
+			{
+				excludedRouters.insert (excluded);
+				excluded += 32;
+			}	
+			std::vector<IdentHash> routers;
+			for (int i = 0; i < 3; i++)
+			{
+				auto r = GetClosestNonFloodfill (buf, excludedRouters);
+				if (r)
+				{	
+					routers.push_back (r->GetIdentHash ());
+					excludedRouters.insert (r->GetIdentHash ());
+				}	
+			}	
+			replyMsg = CreateDatabaseSearchReply (buf, routers);
+		}	
+		else
+		{	
 			auto router = FindRouter (buf);
 			if (router)
 			{
@@ -690,7 +713,6 @@ namespace data
 				std::set<IdentHash> excludedRouters;
 				for (int i = 0; i < numExcluded; i++)
 				{
-				// TODO: check for all zeroes (exploratory)
 					excludedRouters.insert (excluded);
 					excluded += 32;
 				}	
@@ -699,12 +721,14 @@ namespace data
 				{
 					auto floodfill = GetClosestFloodfill (buf, excludedRouters);
 					if (floodfill)
+					{	
 						routers.push_back (floodfill->GetIdentHash ());
+						excludedRouters.insert (floodfill->GetIdentHash ());
+					}	
 				}	
 				replyMsg = CreateDatabaseSearchReply (buf, routers);
 			}
-		else
-			excluded += numExcluded*32; // we don't care about exluded	
+		}
 		
 		if (replyMsg)
 		{	
@@ -903,6 +927,29 @@ namespace data
 		return r;
 	}	
 
+	std::shared_ptr<const RouterInfo> NetDb::GetClosestNonFloodfill (const IdentHash& destination, 
+		const std::set<IdentHash>& excluded) const
+	{
+		std::shared_ptr<const RouterInfo> r;
+		XORMetric minMetric;
+		IdentHash destKey = CreateRoutingKey (destination);
+		minMetric.SetMax ();
+		// must be called from NetDb thread only
+		for (auto it: m_RouterInfos)
+		{	
+			if (!it.second->IsFloodfill () && !excluded.count (it.first))
+			{	
+				XORMetric m = destKey ^ it.first;
+				if (m < minMetric)
+				{
+					minMetric = m;
+					r = it.second;
+				}
+			}	
+		}	
+		return r;
+	}	
+	
 	void NetDb::ManageLeaseSets ()
 	{
 		for (auto it = m_LeaseSets.begin (); it != m_LeaseSets.end ();)

NetDb.h

@@ -80,6 +80,7 @@ namespace data
 			std::shared_ptr<const RouterInfo> GetRandomRouter (std::shared_ptr<const RouterInfo> compatibleWith) const;
 			std::shared_ptr<const RouterInfo> GetHighBandwidthRandomRouter (std::shared_ptr<const RouterInfo> compatibleWith) const;
 			std::shared_ptr<const RouterInfo> GetClosestFloodfill (const IdentHash& destination, const std::set<IdentHash>& excluded) const;
+			std::shared_ptr<const RouterInfo> GetClosestNonFloodfill (const IdentHash& destination, const std::set<IdentHash>& excluded) const;
 			void SetUnreachable (const IdentHash& ident, bool unreachable);			
 
 			void PostI2NPMsg (I2NPMessage * msg);