Added a DNS script for linux and Mac OSX as an alternative to system calls (fixes #15)

Author: ereOn

apps/freelan/config/freelan.cfg

@@ -722,6 +722,27 @@ ipv6_address_prefix_length=2aa1::1/8
 # Default: in_network
 #dns_servers_acceptance_policy=in_network
 
+# The script to call when a DNS entry is to be added or removed.
+#
+# The script is called with the tap adapter's name as it's first argument.
+# The second argument is a verb which can be:
+# - add: A DNS entry must be added.
+# - remove: A DNS entry must be removed.
+# The third argument is the DNS server address to add or remove.
+#
+# If the script exits with a non-zero value, it is assumed that the addition or
+# removal of the DNS entry failed. If the addition fails for a given address,
+# the script won't be called for removal for this same address.
+#
+# On Windows, if no script is provided, FreeLAN will add/remove the DNS server
+# using system calls.
+#
+# On Mac OS X and Linux, there is sadly no reliable system call and you MUST
+# provide a script or DNS settings will simply be ignored.
+#
+# Default: <empty>
+#dns_script=
+
 [security]
 
 # The passphrase used to generate a pre-shared key to use for encryption.

apps/freelan/src/configuration_helper.cpp

@@ -372,6 +372,7 @@ po::options_description get_router_options()
 	("router.system_route_acceptance_policy", po::value<fl::router_configuration::system_route_scope_type>()->default_value(fl::router_configuration::system_route_scope_type::none), "The system route acceptance policy.")
 	("router.maximum_routes_limit", po::value<unsigned int>()->default_value(1), "The maximum count of routes to accept for a given host.")
 	("router.dns_servers_acceptance_policy", po::value<fl::router_configuration::dns_servers_scope_type>()->default_value(fl::router_configuration::dns_servers_scope_type::in_network), "The DNS servers acceptance policy.")
+	("router.dns_script", po::value<fs::path>()->default_value(""), "The DNS script.")
 	;
 
 	return result;
@@ -567,4 +568,5 @@ void setup_configuration(const fscp::logger& logger, fl::configuration& configur
 	configuration.router.system_route_acceptance_policy = vm["router.system_route_acceptance_policy"].as<fl::router_configuration::system_route_scope_type>();
 	configuration.router.maximum_routes_limit = vm["router.maximum_routes_limit"].as<unsigned int>();
 	configuration.router.dns_servers_acceptance_policy = vm["router.dns_servers_acceptance_policy"].as<fl::router_configuration::dns_servers_scope_type>();
+	configuration.router.dns_script = vm["router.dns_script"].as<fs::path>();
 }

apps/freelan/src/main.cpp

@@ -478,6 +478,11 @@ void run(fscp::logger& logger, const cli_configuration& configuration, int& exit
 		core.set_authentication_callback(boost::bind(&execute_authentication_script, configuration.fl_configuration.server.authentication_script, logger, _1, _2, _3, _4));
 	}
 
+	if (!configuration.fl_configuration.router.dns_script.empty())
+	{
+		core.set_dns_callback(boost::bind(&execute_dns_script, configuration.fl_configuration.router.dns_script, logger, _1, _2, _3));
+	}
+
 	core.open();
 
 	signals.async_wait(boost::bind(signal_handler, _1, _2, boost::ref(core), boost::ref(exit_signal)));

apps/freelan/src/tools.cpp

@@ -227,3 +227,21 @@ bool execute_authentication_script(const boost::filesystem::path& script, const
 
 	return (exit_status == 0);
 }
+
+bool execute_dns_script(const boost::filesystem::path& script, const fscp::logger& logger, const std::string& tap_adapter, freelan::core::DnsAction action, const boost::asio::ip::address& dns_server)
+{
+	const std::string str_action = (action == freelan::core::DnsAction::Add) ? "add" : "remove";
+
+#if defined(WINDOWS) && defined(UNICODE)
+	int exit_status = execute(logger, script, { to_wstring(tap_adapter), to_wstring(str_action), to_wstring(dns_server.to_string()) });
+#else
+	int exit_status = execute(logger, script, { tap_adapter, str_action, dns_server.to_string() });
+#endif
+
+	if (exit_status != 0)
+	{
+		logger(fscp::log_level::warning) << "DNS script exited with a non-zero exit status: " << exit_status;
+	}
+
+	return (exit_status == 0);
+}

apps/freelan/src/tools.hpp

@@ -110,4 +110,15 @@ bool execute_certificate_validation_script(const boost::filesystem::path& script
  */
 bool execute_authentication_script(const boost::filesystem::path& script, const fscp::logger& logger, const std::string& username, const std::string& password, const std::string& remote_host, uint16_t remote_port);
 
+/**
+ * \brief The DNS function.
+ * \param script The script to call.
+ * \param logger The logger instance.
+ * \param tap_adapter The tap_adapter instance.
+ * \param action A flag that indicates the action.
+ * \param dns_server The DNS server address to add or remove.
+ * \return The execution result of the specified script.
+ */
+bool execute_dns_script(const boost::filesystem::path& script, const fscp::logger& logger, const std::string& tap_adapter, freelan::core::DnsAction action, const boost::asio::ip::address& dns_server);
+
 #endif /* TOOLS_HPP */

apps/freelan/src/windows/service.cpp

@@ -515,6 +515,11 @@ namespace windows
 					core.set_authentication_callback(boost::bind(&execute_authentication_script, fl_configuration.server.authentication_script, logger, _1, _2, _3, _4));
 				}
 
+				if (!fl_configuration.router.dns_script.empty())
+				{
+					core.set_dns_callback(boost::bind(&execute_dns_script, fl_configuration.router.dns_script, logger, _1, _2, _3));
+				}
+
 				core.open();
 
 				boost::unique_lock<boost::mutex> lock(ctx.stop_function_mutex);

libs/asiotap/include/asiotap/base_dns_servers_manager.hpp

@@ -130,6 +130,16 @@ namespace asiotap
 			 */
 			typedef boost::shared_ptr<entry_type_impl> entry_type;
 
+			/**
+			 * \brief The add handler type.
+			 */
+			typedef boost::function<bool (const dns_server_type&)> dns_server_add_handler_type;
+
+			/**
+			 * \brief The remove handler type.
+			 */
+			typedef boost::function<bool (const dns_server_type&)> dns_server_remove_handler_type;
+
 			/**
 			 * \brief The registration success handler type.
 			 */
@@ -151,7 +161,13 @@ namespace asiotap
 			typedef boost::function<void(const dns_server_type&, const boost::system::system_error&)> dns_server_unregistration_failure_handler_type;
 
 			explicit base_dns_servers_manager(boost::asio::io_service& io_service_) :
-				m_io_service(io_service_)
+				m_io_service(io_service_),
+				m_dns_server_add_handler(),
+				m_dns_server_remove_handler(),
+				m_dns_server_registration_success_handler(),
+				m_dns_server_registration_failure_handler(),
+				m_dns_server_unregistration_success_handler(),
+				m_dns_server_unregistration_failure_handler()
 			{
 			}
 
@@ -166,6 +182,16 @@ namespace asiotap
 				return m_io_service;
 			}
 
+			void set_dns_server_add_handler(dns_server_add_handler_type handler)
+			{
+				m_dns_server_add_handler = handler;
+			}
+
+			void set_dns_server_remove_handler(dns_server_remove_handler_type handler)
+			{
+				m_dns_server_remove_handler = handler;
+			}
+
 			void set_dns_server_registration_success_handler(dns_server_registration_success_handler_type handler)
 			{
 				m_dns_server_registration_success_handler = handler;
@@ -190,7 +216,15 @@ namespace asiotap
 			{
 				try
 				{
-					static_cast<DNSServersManagerType*>(this)->register_dns_server(dns_server);
+					bool result = false;
+
+					if (m_dns_server_add_handler) {
+						result = m_dns_server_add_handler(dns_server);
+					}
+
+					if (!result) {
+						static_cast<DNSServersManagerType*>(this)->register_dns_server(dns_server);
+					}
 
 					if (m_dns_server_registration_success_handler)
 					{
@@ -214,7 +248,15 @@ namespace asiotap
 			{
 				try
 				{
-					static_cast<DNSServersManagerType*>(this)->unregister_dns_server(dns_server);
+					bool result = false;
+
+					if (m_dns_server_remove_handler) {
+						result = m_dns_server_remove_handler(dns_server);
+					}
+
+					if (!result) {
+						static_cast<DNSServersManagerType*>(this)->unregister_dns_server(dns_server);
+					}
 
 					if (m_dns_server_unregistration_success_handler)
 					{
@@ -256,6 +298,8 @@ namespace asiotap
 
 			boost::asio::io_service& m_io_service;
 			entry_table_type m_entry_table;
+			dns_server_add_handler_type m_dns_server_add_handler;
+			dns_server_remove_handler_type m_dns_server_remove_handler;
 			dns_server_registration_success_handler_type m_dns_server_registration_success_handler;
 			dns_server_registration_failure_handler_type m_dns_server_registration_failure_handler;
 			dns_server_unregistration_success_handler_type m_dns_server_unregistration_success_handler;

libs/asiotap/include/asiotap/error.hpp

@@ -72,7 +72,9 @@ namespace asiotap
 		process_handle_expected,
 		external_process_output_parsing_error,
 		no_such_tap_adapter,
-		invalid_ip_configuration
+		invalid_ip_configuration,
+		external_process_execution_failed,
+		no_dns_script_provided
 	};
 
 	/**

libs/asiotap/src/error.cpp

@@ -94,6 +94,14 @@ namespace asiotap
 			{
 				return "The specified IP configuration is invalid";
 			}
+			case asiotap_error::external_process_execution_failed:
+			{
+				return "The execution of the external process failed";
+			}
+			case asiotap_error::no_dns_script_provided:
+			{
+				return "No DNS script was provided";
+			}
 			default:
 			{
 				return "Unknown asiotap error";

libs/freelan/include/freelan/configuration.hpp

@@ -620,6 +620,11 @@ namespace freelan
 		 * \brief The DNS servers acceptance policy.
 		 */
 		dns_servers_scope_type dns_servers_acceptance_policy;
+
+		/**
+		 * \brief The DNS script.
+		 */
+		boost::filesystem::path dns_script;
 	};
 
 	/**