check if local ipv6 clearnet address is presented

libi2pd/RouterContext.cpp

@@ -177,6 +177,9 @@ namespace i2p
 			}
 		}
 		if (ipv6)
+		{
+			auto ipv6addr = i2p::util::net::GetClearnetIPV6Address ();
+			if (!ipv6addr.is_unspecified ())
 			{	
 				std::string host; i2p::config::GetOption("address6", host);
 				if (host.empty () && !ipv4) i2p::config::GetOption("host", host); // use host for ipv6 only if ipv4 is not presented
@@ -225,6 +228,7 @@ namespace i2p
 					}
 				}
 			}	
+		}
 		if (ygg)
 		{
 			auto yggaddr = i2p::util::net::GetYggdrasilAddress ();

libi2pd/Transports.cpp

@@ -1345,6 +1345,12 @@ namespace transport
 			}
 		}
 
+		if (ipv6 &&	i2p::util::net::GetClearnetIPV6Address ().is_unspecified ())
+		{
+			LogPrint(eLogWarning, "Transports: Clearnet ipv6 not found. Disabled");
+			ipv6 = false;
+		}	
+		
 		if (!i2p::config::IsDefault("port"))
 		{
 			LogPrint(eLogInfo, "Transports: Accepting incoming connections at port ", port);

libi2pd/util.cpp

@@ -545,7 +545,8 @@ namespace net
 		return (reservedPorts.find(port) != reservedPorts.end());
 	}
 
-	boost::asio::ip::address_v6 GetYggdrasilAddress ()
+	template<typename CheckAddress>
+	static boost::asio::ip::address_v6 GetLocalIPV6Address (CheckAddress checkAddress)
 	{
 #if defined(_WIN32)
 		ULONG outBufLen = 0;
@@ -580,7 +581,7 @@ namespace net
 			{
 				LPSOCKADDR lpAddr = pUnicast->Address.lpSockaddr;
 				sockaddr_in6 *localInterfaceAddress = (sockaddr_in6*) lpAddr;
-				if (IsYggdrasilAddress(localInterfaceAddress->sin6_addr.u.Byte)) {
+				if (checkAddress(localInterfaceAddress->sin6_addr.u.Byte)) {
 					boost::asio::ip::address_v6::bytes_type bytes;
 					memcpy (bytes.data (), &localInterfaceAddress->sin6_addr.u.Byte, 16);
 					FREE(pAddresses);
@@ -590,7 +591,7 @@ namespace net
 			}
 			pCurrAddresses = pCurrAddresses->Next;
 		}
-		LogPrint(eLogWarning, "NetIface: Interface with Yggdrasil network address not found");
+		LogPrint(eLogWarning, "NetIface: Interface with ipv6 network address not found");
 		FREE(pAddresses);
 		return boost::asio::ip::address_v6 ();
 #else
@@ -604,7 +605,7 @@ namespace net
 					if (cur->ifa_addr && cur->ifa_addr->sa_family == AF_INET6)
 					{
 						sockaddr_in6* sa = (sockaddr_in6*)cur->ifa_addr;
-						if (IsYggdrasilAddress(sa->sin6_addr.s6_addr))
+						if (checkAddress(sa->sin6_addr.s6_addr))
 						{
 							boost::asio::ip::address_v6::bytes_type bytes;
 							memcpy (bytes.data (), &sa->sin6_addr, 16);
@@ -617,14 +618,27 @@ namespace net
 		}
 		catch (std::exception& ex)
 		{
-			LogPrint(eLogError, "NetIface: Exception while searching Yggdrasill address using ifaddr: ", ex.what());
+			LogPrint(eLogError, "NetIface: Exception while searching ipv6 address using ifaddr: ", ex.what());
 		}
-		LogPrint(eLogWarning, "NetIface: Interface with Yggdrasil network address not found");
+		LogPrint(eLogWarning, "NetIface: Interface with ipv6 network address not found");
 		if (addrs) freeifaddrs(addrs);
 		return boost::asio::ip::address_v6 ();
 #endif
 	}
 
+	boost::asio::ip::address_v6 GetYggdrasilAddress ()
+	{
+		return GetLocalIPV6Address ([](const uint8_t addr[16]) { return IsYggdrasilAddress (addr); });
+	}	
+
+	boost::asio::ip::address_v6 GetClearnetIPV6Address ()
+	{
+		return GetLocalIPV6Address ([](const uint8_t addr[16])
+			{
+				return (addr[0] & 0xF0) == 0x20; // 2000::/3
+			});	
+	}	
+	
 	bool IsLocalAddress (const boost::asio::ip::address& addr)
 	{
 		auto mtu = // TODO: implement better

libi2pd/util.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2024, The PurpleI2P Project
+* Copyright (c) 2013-2025, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -231,6 +231,7 @@ namespace util
 		int GetMaxMTU (const boost::asio::ip::address_v6& localAddress); // check tunnel broker for ipv6 address
 		const boost::asio::ip::address GetInterfaceAddress (const std::string & ifname, bool ipv6=false);
 		boost::asio::ip::address_v6 GetYggdrasilAddress ();
+		boost::asio::ip::address_v6 GetClearnetIPV6Address ();
 		bool IsLocalAddress (const boost::asio::ip::address& addr);
 		bool IsInReservedRange (const boost::asio::ip::address& host);
 		bool IsYggdrasilAddress (const boost::asio::ip::address& addr);