Development of libtrap interface

General information

There are two types of libtrap interfaces (unidirectional) — input and output. After successful initialization of libtrap (trap_ctx_init()), all interfaces are stored in libtrap context in the array trap_ctx_priv_s::in_ifc_list or trap_ctx_priv_s::out_ifc_list. That means every IFC must initialize its structure trap_input_ifc_s or trap_output_ifc_s as it is listed in Steps section below.

Libtrap interface (IFC) is a source code file that is compiled with the rest of libtrap. Every IFC implements functions:

typedef void (*ifc_terminate_func_t)(void *);
typedef void (*ifc_destroy_func_t)(void *);
typedef void (*ifc_create_dump_func_t)(void *, uint32_t, const char *);

and one or both functions:

typedef int (*ifc_recv_func_t)(void *, void *, uint32_t *, int);
typedef int (*ifc_send_func_t)(void *, const void *, uint32_t, int);

The full list of required functions of IFC can be found in IFC API.

Additionally, IFC should implement it's own constructor function.

What to do to develop IFC

To add new IFC into libtrap some steps should be done:

1. choose new IFC type letter by defining new macro in Types of IFC.
2. add new IFC type into trap_ifc_type_supported
3. add call to constructor into trapifc_in_construct() resp. trapifc_out_construct() for input resp. output IFC
4. write own implementation of IFC functions (IFC API)
5. write own constructor of new IFC
6. set pointers to functions in trap_input_ifc_s or trap_output_ifc_s, the setting of pointers should be done in IFC's constructor

Simplified example of input IFC can be found in ifc_dummy.c. This file implements blackhole and generator. Blackhole is the output IFC that drops every message that is sent by module. Generator is the input IFC generates messages that are received by module.

More complex example is TCPIP and UNIX socket IFCs implemented in ifc_tcpip.c.