Use alternate dns name if name resolution fails for internet server (6dns.org seems to be unreliable, but is still the only one to provide both ipv4 and ipv6 name resolution for free).

src/net/common/resolverthread.cpp

@@ -45,6 +45,7 @@ ResolverThread::Init(const ClientContext &context)
 
 	GetContext().SetAddrFamily(context.GetAddrFamily());
 	GetContext().SetServerAddr(context.GetServerAddr());
+	GetContext().SetAlternateServerAddr(context.GetAlternateServerAddr());
 	GetContext().SetServerPort(context.GetServerPort());
 }
 
@@ -78,6 +79,19 @@ ResolverThread::Main()
 		context.GetProtocol(),
 		(struct sockaddr *)context.GetClientSockaddr(),
 		context.GetClientSockaddrSize());
+
+	if (!m_retVal && !context.GetAlternateServerAddr().empty())
+	{
+		// Try alternate name.
+		m_retVal = socket_resolve(
+			context.GetAlternateServerAddr().c_str(),
+			tmpStr.str().c_str(),
+			context.GetAddrFamily(),
+			SOCK_STREAM,
+			context.GetProtocol(),
+			(struct sockaddr *)context.GetClientSockaddr(),
+			context.GetClientSockaddrSize());
+	}
 }
 
 const ClientContext &