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init: defer forwarded session requests when needed

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This patch changes init's service forwarding such that pending requests
are kept unanswered as long as the requested service is not present
(yet). In dynamic-init scenarios, this is needed in situtions where the
dynamic init is known to eventually provide the service but the internal
subsystem is not ready yet. Previously, a client that attempted to
request a session in this early phase would get a 'Service_denied'
exception. By deferring the forwarding in this situation, the behaviour
becomes deterministic.

If a matching '<service>' exists but there is no matching policy sub
node, the request is answered with 'Service_denied' - as expected.
This commit is contained in:
Norman Feske 2017-06-30 15:21:29 +02:00 committed by Christian Helmuth
parent b3e039d0b1
commit 6184a27619
2 changed files with 26 additions and 5 deletions
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26
repos/os/src/init/server.cc
View File

@ -109,7 +109,7 @@ Init::Server::_resolve_session_request(Service::Name const &service_name,
matching_service = &service; });
if (!matching_service)
throw Service_denied();
throw Service_not_present();
return matching_service->resolve_session_request(label);
}
@ -169,6 +169,16 @@ void Init::Server::session_closed(Session_state &session)
void Init::Server::_handle_create_session_request(Xml_node request,
Parent::Client::Id id)
{
/*
* Ignore requests that are already successfully forwarded (by a prior call
* of '_handle_create_session_request') but still remain present in the
* 'session_requests' ROM because the server child has not responded yet.
*/
try {
_client_id_space.apply<Parent::Client>(id, [&] (Parent::Client const &) { });
return;
} catch (Id_space<Parent::Client>::Unknown_id) { /* normal case */ }
if (!request.has_sub_node("args"))
return;
@ -257,6 +267,7 @@ void Init::Server::_handle_create_session_request(Xml_node request,
catch (Insufficient_cap_quota) {
_env.parent().session_response(Parent::Server::Id { id.value },
Parent::INSUFFICIENT_CAP_QUOTA); }
catch (Service_not_present) { /* keep request pending */ }
}
@ -356,11 +367,15 @@ void Init::Server::apply_config(Xml_node config)
_session_request_handler.construct(_env.ep(), *this,
&Server::_handle_session_requests);
_session_requests->sigh(*_session_request_handler);
if (_session_requests.constructed())
_handle_session_requests();
}
/*
* Try to resolve pending session requests that may become serviceable with
* the new configuration.
*/
if (services_provided && _session_requests.constructed())
_handle_session_requests();
/*
* Re-validate routes of existing sessions, close sessions whose routes
* changed.
@ -375,6 +390,7 @@ void Init::Server::apply_config(Xml_node config)
if (!route_unchanged)
throw Service_denied();
}
catch (Service_denied) { close_session(session); }
catch (Service_denied) { close_session(session); }
catch (Service_not_present) { close_session(session); }
});
}

5
repos/os/src/init/server.h
View File

@ -51,6 +51,11 @@ class Init::Server : Session_state::Ready_callback,
*/
Id_space<Parent::Client> _client_id_space;
/**
* Exception type
*/
class Service_not_present : Exception { };
/**
* Meta data of service provided to our parent
*/