class ara::idsm::ContextDataProvider

The abstract class ara::idsm::ContextDataProvider serves for the application-specific provision and modification of context data for the Intrusion Detection System Manager [SWS_AIDSM_10500]. Applications derive from the class, implement the callback ModifyContextData, and control release for IdsM via the methods Offer and StopOffer [SWS_AIDSM_10507]. The instance is not copyable, and since central methods are not thread-safe, concurrent access is likely to require external synchronization (interpretation). Question (open)

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Context

The class ara::idsm::ContextDataProvider serves for providing and modifying context data for the Intrusion Detection System Manager (IdsM) subsystem [SWS_AIDSM_10500]. Within the security architecture, the class acts as an interface between a security-relevant application and the IdsM service. Since the member function ModifyContextData is specified as pure virtual [SWS_AIDSM_10509], ContextDataProvider represents an abstract base class. An application derives its own implementation in order to supplement specific context data in the event of security-relevant events. Binding to the architecture configuration is performed via an ara::core::InstanceSpecifier for the modeled provider port [SWS_AIDSM_10501].

Lifecycle

Creation of an instance is performed explicitly via the constructor by specifying the port identifier (ara::core::InstanceSpecifier) as well as the buffer parameters additionalBytes and originalContextDataOffset [SWS_AIDSM_10501]. This constructor is declared as thread-safe [SWS_AIDSM_10501]. In order to guarantee clear ownership for the interface endpoint, both the copy constructor [SWS_AIDSM_10504] and the copy assignment operator [SWS_AIDSM_10506] are deleted. Passing the instance is possible via move semantics: the move constructor is thread-safe [SWS_AIDSM_10503], whereas the assignment operator operator= with rvalue reference is defined as not thread-safe [SWS_AIDSM_10505].

After creation, the instance is in an inactive state. Only by explicitly calling Offer() is registration activated and IdsM authorized to call ModifyContextData [SWS_AIDSM_10507]. This authorization can be revoked at any time via StopOffer() [SWS_AIDSM_10508]. Prior to destroying the object via the virtual destructor [SWS_AIDSM_10502], according to common practice StopOffer() is likely required to be called to terminate ongoing callbacks by IdsM in a timely manner (interpretation). Question Q-ee65caee57919f00 (open) The virtual destructor is specified as not thread-safe [SWS_AIDSM_10502].

Usage Path

A typical use case begins with the definition of an application-specific class that inherits from ContextDataProvider and implements the method ModifyContextData [SWS_AIDSM_10509]. After instantiation, the application calls Offer() to provide the context data for IdsM [SWS_AIDSM_10507]. As soon as IdsM registers a security event for which context data is to be supplemented, the subsystem calls the callback ModifyContextData [SWS_AIDSM_10509]. The method receives the data area as ara::core::Span<std::uint8_t> and the identifier EventIdType, updates the buffer content, and returns the actual byte count as ara::core::Result<std::size_t> [SWS_AIDSM_10509]. If data provision is to be terminated, the application calls StopOffer() [SWS_AIDSM_10508].

Sequence diagram: Interaction sequence between application, ContextDataProvider, and IdsM from activation via Offer through the callback to deactivation via StopOffer. Sources: [SWS_AIDSM_10507], [SWS_AIDSM_10508], [SWS_AIDSM_10509]

Error Scenarios

All methods of the interface are declared with noexcept; errors are returned via the type ara::core::Result. Calling Offer() returns a ara::core::Result<void> [SWS_AIDSM_10507], which must be checked by the application in order to intercept possible errors during service provision. If the provider cannot write the requested context data to ModifyContextData, the implementation is likely to report a system-specific error in the ara::core::Result<std::size_t> (interpretation) [SWS_AIDSM_10509]. Question Q-585e19770d59309e (open)

Regarding concurrency, note that Offer() [SWS_AIDSM_10507], StopOffer() [SWS_AIDSM_10508], ModifyContextData() [SWS_AIDSM_10509], the assignment operator [SWS_AIDSM_10505], and the destructor [SWS_AIDSM_10502] are specified as not thread-safe. If these methods are called concurrently from multiple threads without external synchronization, this is likely to lead to data races and unpredictable behavior (interpretation). Question Q-80b83a52aba53d67 (open)