exclude routers from the same subnet from next hop

libi2pd/NetDb.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2025, The PurpleI2P Project
+* Copyright (c) 2013-2026, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -1163,6 +1163,7 @@ namespace data
 					(reverse ? (compatibleWith->IsReachableFrom (*router) && router->GetCompatibleTransports (true)):
 						router->IsReachableFrom (*compatibleWith)) && !router->IsNAT2NATOnly (*compatibleWith) &&
 					router->IsECIES () && !router->IsHighCongestion (clientTunnel) &&
+					!router->IsSameSubnet (*compatibleWith) &&
 					(!checkIsReal || router->GetProfile ()->IsReal ()) &&
 					(!endpoint || (router->IsV4 () && (!reverse || router->IsPublished (true)))); // endpoint must be ipv4 and published if inbound(reverse)
 			});
@@ -1202,6 +1203,7 @@ namespace data
 					(router->GetCaps () & RouterInfo::eHighBandwidth) &&
 					router->GetVersion () >= NETDB_MIN_HIGHBANDWIDTH_VERSION &&
 					router->IsECIES () && !router->IsHighCongestion (true) &&
+					!router->IsSameSubnet (*compatibleWith) &&
 					(!checkIsReal || router->GetProfile ()->IsReal ()) &&
 					(!endpoint || (router->IsV4 () && (!reverse || router->IsPublished (true)))); // endpoint must be ipv4 and published if inbound(reverse)
 

libi2pd/RouterInfo.cpp

@@ -971,15 +971,9 @@ namespace data
 	template<typename Filter>
 	std::shared_ptr<const RouterInfo::Address> RouterInfo::GetAddress (Filter filter) const
 	{
-		// TODO: make it more generic using comparator
+		auto addresses = GetAddresses ();
-#ifdef __cpp_lib_atomic_shared_ptr
-		AddressesPtr addresses = m_Addresses;
-#else
-		auto addresses = boost::atomic_load (&m_Addresses);
-#endif
 		for (const auto& address : *addresses)
 			if (address && filter (address)) return address;
-
 		return nullptr;
 	}
 
@@ -1211,6 +1205,21 @@ namespace data
 		}
 	}
 
+	bool RouterInfo::IsSameSubnet (const RouterInfo& other) const
+	{
+		auto transports = m_SupportedTransports & other.m_SupportedTransports;
+		if (!transports) return false;
+		auto addresses1 = GetAddresses (), addresses2 = other.GetAddresses ();;
+		for (int i = 0; i < eNumTransports; i++)
+			if (i != eNTCP2V6MeshIdx && (transports & (1 << i)))
+			{
+				auto addr1 = (*addresses1)[i], addr2 = (*addresses2)[i];
+				if (addr1 && addr2 && !addr1->host.is_unspecified () && !addr2->host.is_unspecified ())
+					return addr1->IsSameSubnet (*addr2); // first adddess with IPs
+			}
+		return false;
+	}
+
 	void LocalRouterInfo::CreateBuffer (const PrivateKeys& privateKeys)
 	{
 		RefreshTimestamp ();

libi2pd/RouterInfo.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2025, The PurpleI2P Project
+* Copyright (c) 2013-2026, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -186,6 +186,14 @@ namespace data
 
 				bool IsV4 () const { return (caps & AddressCaps::eV4) || (host.is_v4 () && !host.is_unspecified ()); };
 				bool IsV6 () const { return (caps & AddressCaps::eV6) || (host.is_v6 () && !host.is_unspecified ()); };
+
+				bool IsSameSubnet (const Address& other)
+				{
+					if (host.is_unspecified () || other.host.is_unspecified ()) return false;
+					if (host.is_v4 () && other.host.is_v4 ()) return !std::memcmp (host.to_v4 ().to_bytes ().data (), other.host.to_v4 ().to_bytes ().data (), 3); // /24
+					if (host.is_v6 () && other.host.is_v6 ()) return !std::memcmp (host.to_v6 ().to_bytes ().data (), other.host.to_v6 ().to_bytes ().data (), 7); // /56
+					return false;
+				}
 			};
 
 			class Buffer: public std::array<uint8_t, MAX_RI_BUFFER_SIZE>
@@ -263,6 +271,7 @@ namespace data
 			void EnableMesh ();
 			void DisableMesh ();
 			bool IsCompatible (const RouterInfo& other) const { return m_SupportedTransports & other.m_SupportedTransports; };
+			bool IsSameSubnet (const RouterInfo& other) const;
 			bool IsReachableFrom (const RouterInfo& other) const { return m_ReachableTransports & other.m_SupportedTransports; };
 			bool IsReachableBy (CompatibleTransports transports) const { return m_ReachableTransports & transports; };
 			CompatibleTransports GetCompatibleTransports (bool incoming) const { return incoming ? m_ReachableTransports : m_SupportedTransports; };