base: Add Child_policy::Route

The new return value of 'resolve_session_request' allows the child
policy to define the label used as the policy selector at the server.

Because this patch introduces the distinction of the child-provided
label from the label as presented to the server along with the session
request, the latter is now handled as a dedicated 'Session_state'
argument.

Issue #2248

repos/base/include/base/child.h

@@ -69,11 +69,38 @@ struct Genode::Child_policy
 	 * Determine service to provide a session request
 	 *
 	 * \return  service to be contacted for the new session
+	 * \deprecated
 	 *
 	 * \throw Parent::Service_denied
 	 */
 	virtual Service &resolve_session_request(Service::Name       const &,
-	                                         Session_state::Args const &) = 0;
+	                                         Session_state::Args const &)
+	{
+		throw Parent::Service_denied();
+	}
+
+	/**
+	 * Routing destination of a session request
+	 */
+	struct Route
+	{
+		Service &service;
+		Session_label const label;
+	};
+
+	/**
+	 * Determine service and server-side label for a given session request
+	 *
+	 * \return  routing and policy-selection information for the session
+	 *
+	 * \throw Parent::Service_denied
+	 */
+	virtual Route resolve_session_request(Service::Name const &,
+	                                      Session_label const &)
+	{
+		/* \deprecated  make pure virtual once the old version is gone */
+		throw Parent::Service_denied();
+	}
 
 	/**
 	 * Apply transformations to session arguments
@@ -271,6 +298,9 @@ class Genode::Child : protected Rpc_object<Parent>,
 
 		typedef Session_state::Args Args;
 
+		static Child_policy::Route _resolve_session_request(Child_policy &,
+                                                            Service::Name const &,
+                                                            char const *);
 		/*
 		 * Members that are initialized not before the child's environment is
 		 * complete.
@@ -370,7 +400,7 @@ class Genode::Child : protected Rpc_object<Parent>,
 
 			Args const _args;
 
-			Service &_service;
+			Child_policy::Route _route;
 
 			/*
 			 * The 'Env_service' monitors session responses in order to attempt
@@ -439,8 +469,9 @@ class Genode::Child : protected Rpc_object<Parent>,
 			               Label const &label = Label())
 			:
 				_args(_construct_args(child._policy, label)),
-				_service(child._policy.resolve_session_request(_service_name(), _args)),
+				_route(child._resolve_session_request(child._policy, _service_name(),
-				_env_service(child, _service),
+				                                      _args.string())),
+				_env_service(child, _route.service),
 				_connection(_env_service, child._id_space, id, _args,
 				            child._policy.filter_session_affinity(Affinity()))
 			{ }

repos/base/include/base/local_connection.h

@@ -60,8 +60,8 @@ struct Genode::Local_connection_base : Noncopyable
 		                      Args const &args, Affinity const &affinity,
 		                      size_t ram_quota)
 		:
-			_session_state(service, id_space, id, _init_args(args, ram_quota),
+			_session_state(service, id_space, id, label_from_args(args.string()),
-			               affinity)
+			               _init_args(args, ram_quota), affinity)
 		{
 			_session_state.service().initiate_request(_session_state);
 		}

repos/base/include/base/service.h

@@ -192,7 +192,7 @@ class Genode::Local_service : public Service
 			case Session_state::CREATE_REQUESTED:
 
 				try {
-					SESSION &rpc_obj = _factory.create(session.args(),
+					SESSION &rpc_obj = _factory.create(Session_state::Server_args(session).string(),
 					                                   session.affinity());
 					session.local_ptr = &rpc_obj;
 					session.cap       = rpc_obj.cap();
@@ -272,9 +272,10 @@ class Genode::Parent_service : public Service
 				session.id_at_parent.construct(session.parent_client,
 				                               _env.id_space());
 				try {
+
 					session.cap = _env.session(name().string(),
 					                           session.id_at_parent->id(),
-					                           session.args().string(),
+					                           Session_state::Server_args(session).string(),
 					                           session.affinity());
 
 					session.phase = Session_state::AVAILABLE;

repos/base/include/base/session_state.h

@@ -21,6 +21,7 @@
 #include <base/id_space.h>
 #include <base/env.h>
 #include <base/log.h>
+#include <base/session_label.h>
 
 namespace Genode {
 
@@ -62,8 +63,9 @@ class Genode::Session_state : public Parent::Client, public Parent::Server,
 
 		Reconstructible<Id_space<Parent::Client>::Element> _id_at_client;
 
-		Args     _args;
+		Session_label const _label;
-		Affinity _affinity;
+		Args                _args;
+		Affinity            _affinity;
 
 	public:
 
@@ -110,15 +112,22 @@ class Genode::Session_state : public Parent::Client, public Parent::Server,
 		 * Constructor
 		 *
 		 * \param service          interface that was used to create the session
+		 * \param label            session label to be presented to the server
 		 * \param client_id_space  ID space for client-side session IDs
 		 * \param client_id        session ID picked by the client
 		 * \param args             session arguments
 		 *
 		 * \throw Id_space<Parent::Client>::Conflicting_id
+		 *
+		 * The client-provided (and child-name-prefixed) session label is
+		 * contained in 'args'. In contrast, the 'label' argument is the label
+		 * presented to the server along with the session request, which
+		 * depends on the policy of 'Child_policy::resolve_session_request'.
 		 */
 		Session_state(Service                  &service,
 		              Id_space<Parent::Client> &client_id_space,
 		              Parent::Client::Id        client_id,
+		              Session_label      const &label,
 		              Args               const &args,
 		              Affinity           const &affinity);
 
@@ -195,6 +204,24 @@ class Genode::Session_state : public Parent::Client, public Parent::Server,
 		 * This function has no effect for sessions not created via a 'Factory'.
 		 */
 		void destroy();
+
+		/**
+		 * Utility to override the client-provided label by the label assigned
+		 * by 'Child_policy::resolve_session_request'.
+		 */
+		struct Server_args
+		{
+			char _buf[Args::capacity()];
+
+			Server_args(Session_state const &session)
+			{
+				Genode::strncpy(_buf, session._args.string(), sizeof(_buf));
+				Arg_string::set_arg_string(_buf, sizeof(_buf),
+				                           "label", session._label.string());
+			}
+
+			char const *string() const { return _buf; }
+		};
 };
 
 

repos/base/lib/symbols/ld

@@ -85,8 +85,8 @@ _ZN6Genode13Registry_base7_insertERNS0_7ElementE T
 _ZN6Genode13Registry_base7_removeERNS0_7ElementE T
 _ZN6Genode13Registry_base9_for_eachERNS0_15Untyped_functorE T
 _ZN6Genode13Session_state7destroyEv T
-_ZN6Genode13Session_stateC1ERNS_7ServiceERNS_8Id_spaceINS_6Parent6ClientEEENS6_2IdERKNS_6StringILm256EEERKNS_8AffinityE T
+_ZN6Genode13Session_stateC1ERNS_7ServiceERNS_8Id_spaceINS_6Parent6ClientEEENS6_2IdERKNS_13Session_labelERKNS_6StringILm256EEERKNS_8AffinityE T
-_ZN6Genode13Session_stateC2ERNS_7ServiceERNS_8Id_spaceINS_6Parent6ClientEEENS6_2IdERKNS_6StringILm256EEERKNS_8AffinityE T
+_ZN6Genode13Session_stateC2ERNS_7ServiceERNS_8Id_spaceINS_6Parent6ClientEEENS6_2IdERKNS_13Session_labelERKNS_6StringILm256EEERKNS_8AffinityE T
 _ZN6Genode13Shared_objectC1ERNS_3EnvERNS_9AllocatorEPKcNS0_4BindENS0_4KeepE T
 _ZN6Genode13Shared_objectC2ERNS_3EnvERNS_9AllocatorEPKcNS0_4BindENS0_4KeepE T
 _ZN6Genode13Shared_objectD1Ev T

repos/base/src/core/main.cc

@@ -94,7 +94,8 @@ Session_capability Core_parent::session(Parent::Client::Id          id,
 			return;
 
 		Session_state &session = *new (_alloc)
-			Session_state(service, _id_space, id, args.string(), affinity);
+			Session_state(service, _id_space, id, label_from_args(args.string()),
+			              args.string(), affinity);
 
 		service.initiate_request(session);
 

repos/base/src/lib/base/child.cc

@@ -156,12 +156,13 @@ void Child::session_sigh(Signal_context_capability sigh)
  */
 Session_state &
 create_session(Child_policy::Name const &child_name, Service &service,
+               Session_label const &label,
                Session_state::Factory &factory, Id_space<Parent::Client> &id_space,
                Parent::Client::Id id, Session_state::Args const &args,
                Affinity const &affinity)
 {
 	try {
-		return service.create_session(factory, id_space, id, args, affinity);
+		return service.create_session(factory, id_space, id, label, args, affinity);
 	}
 	catch (Allocator::Out_of_memory) {
 		error("could not allocate session meta data for child ", child_name);
@@ -179,6 +180,34 @@ create_session(Child_policy::Name const &child_name, Service &service,
 }
 
 
+/*
+ * \deprecated  Temporary wrapper around 'Child_policy::resolve_session_request'
+ *              that tries both overloads.
+ *
+ * \throw Parent::Service_denied
+ */
+Child_policy::Route Child::_resolve_session_request(Child_policy &policy,
+                                                    Service::Name const &name,
+                                                    char const *argbuf)
+{
+	Session_label const label = label_from_args(argbuf);
+
+	/*
+	 * \deprecated  Try old interface, remove once all 'Child_policy'
+	 *              implementations are updated.
+	 */
+	try {
+
+		Session_state::Args args(argbuf);
+		return Child_policy::Route {
+			policy.resolve_session_request(name, args), label };
+	}
+	catch (Parent::Service_denied) { }
+
+	return policy.resolve_session_request(name, label);
+}
+
+
 Session_capability Child::session(Parent::Client::Id id,
                                   Parent::Service_name const &name,
                                   Parent::Session_args const &args,
@@ -202,10 +231,11 @@ Session_capability Child::session(Parent::Client::Id id,
 	Affinity const filtered_affinity = _policy.filter_session_affinity(affinity);
 
 	/* may throw a 'Parent::Service_denied' exception */
-	Service &service = _policy.resolve_session_request(name.string(), argbuf);
+	Child_policy::Route route = _resolve_session_request(_policy, name.string(), argbuf);
+	Service &service = route.service;
 
 	Session_state &session =
-		create_session(_policy.name(), service, *_session_factory,
+		create_session(_policy.name(), service, route.label, *_session_factory,
 		               _id_space, id, argbuf, filtered_affinity);
 
 	session.ready_callback = this;

repos/base/src/lib/base/session_state.cc

@@ -40,8 +40,9 @@ void Session_state::generate_session_request(Xml_generator &xml) const
 		xml.node("create", [&] () {
 			xml.attribute("id", id_at_server->id().value);
 			xml.attribute("service", _service.name());
+			xml.attribute("label", _label);
 			xml.node("args", [&] () {
-				xml.append_sanitized(_args.string());
+				xml.append_sanitized(Server_args(*this).string());
 			});
 		});
 		break;
@@ -110,11 +111,12 @@ void Session_state::destroy()
 Session_state::Session_state(Service                  &service,
                              Id_space<Parent::Client> &client_id_space,
                              Parent::Client::Id        client_id,
+                             Session_label      const &label,
                              Args const               &args,
                              Affinity           const &affinity)
 :
 	_service(service),
 	_donated_ram_quota(Arg_string::find_arg(args.string(), "ram_quota").ulong_value(0)),
 	_id_at_client(*this, client_id_space, client_id),
-	_args(args), _affinity(affinity)
+	_label(label), _args(args), _affinity(affinity)
 { }