blob: 764d25d1b63177f5a7f53ce8f36cc16f67817a5e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
|
@dir /lib/subsys
@brief lib/subsys: Types for declaring a "subsystem".
## Subsystems in Tor
A subsystem is a module with support for initialization, shutdown,
configuration, and so on.
Many parts of Tor can be initialized, cleaned up, and configured somewhat
independently through a table-driven mechanism. Each such part is called a
"subsystem".
To declare a subsystem, make a global `const` instance of the `subsys_fns_t`
type, filling in the function pointer fields that you require with ones
corresponding to your subsystem. Any function pointers left as "NULL" will
be a no-op. Each system must have a name and a "level", which corresponds to
the order in which it is initialized. (See `app/main/subsystem_list.c` for a
list of current subsystems and their levels.)
Then, insert your subsystem in the list in `app/main/subsystem_list.c`. It
will need to occupy a position corresponding to its level.
At this point, your subsystem will be handled like the others: it will get
initialized at startup, torn down at exit, and so on.
Historical note: Not all of Tor's code is currently handled as
subsystems. As you work with older code, you may see some parts of the code
that are initialized from `tor_init()` or `run_tor_main_loop()` or
`tor_run_main()`; and torn down from `tor_cleanup()`. We aim to migrate
these to subsystems over time; please don't add any new code that follows
this pattern.
|
