Overview: IPC message structure
In KasperskyOS, all interactions between processes have statically defined types. The permissible structures of an IPC message are defined by the IDL descriptions of servers.
An IPC message (request and response) contains a constant part and an (optional) arena.
Constant part of an IPC message
The constant part of an IPC message contains the RIID, MID, and (optionally) fixed-size parameters of interface methods.
Fixed-size parameters are parameters that have IDL types of a fixed size.
The RIID and MID identify the interface and method being called:
- The RIID (Runtime Implementation ID) is the sequence number of the utilized endpoint within the set of server endpoints (starting at zero).
- The MID (Method ID) is the sequence number of the called method within the set of methods of the utilized endpoint (starting at zero).
The type of the constant part of the IPC message is generated by the NK compiler based on the IDL description of the interface. A separate structure is generated for each interface method. Union types are also generated for storing any request to a process, component or interface. For more details, refer to Example generation of transport methods and types.
IPC message arena
An IPC message arena (hereinafter also referred to as an arena) contains variable-size parameters of interface methods (and/or elements of these parameters).
Variable-size parameters are parameters that have IDL types of a variable size.
For more details, refer to "Working with an IPC message arena".
Maximum IPC message size
The maximum size of an IPC message is determined by the KasperskyOS kernel parameters. On most hardware platforms supported by KasperskyOS, the cumulative size of the constant part and arena of an IPC message cannot exceed 4, 8, or 16 MB.
IPC message structure verification by the security module
Prior to querying IPC message-related rules, the Kaspersky Security Module verifies that the sent IPC message is correct. Requests and responses are both validated. If the IPC message has an incorrect structure, it will be rejected without calling the security model methods associated with it.
Implementation of IPC interaction
To make it easier for a developer to implement IPC interaction, KasperskyOS Community Edition provides the following:
- NK compiler that generates transport methods and types.
Libkoslibrary that provides the API for working with IPC transport.
Implementation of simple IPC interaction is demonstrated in the echo and ping examples (/opt/KasperskyOS-Community-Edition-<version>/examples/).
